Hyaluronic acid

Hyaluronic Acid in the Third Millennium.

Since its first isolation in 1934, hyaluronic acid (HA) has been studied across a variety of research areas. This unbranched glycosaminoglycan consisting of repeating disaccharide units of N-acetyl-d-glucosamine and d-glucuronic acid is almost ubiquitous in humans and in other vertebrates. HA is involved in many key processes, including cell signaling, wound reparation, tissue regeneration, morphogenesis, matrix organization and pathobiology, and has unique physico-chemical properties, such as biocompatibility, biodegradability, mucoadhesivity, hygroscopicity and viscoelasticity. For these reasons, exogenous HA has been investigated as a drug delivery system and treatment in cancer, ophthalmology, arthrology, pneumology, rhinology, urology, aesthetic medicine and cosmetics. To improve and customize its properties and applications, HA can be subjected to chemical modifications: conjugation and crosslinking. The present review gives an overview regarding HA, describing its history, physico-chemical, structural and hydrodynamic properties and biology (occurrence, biosynthesis (by hyaluronan synthases), degradation (by hyaluronidases and oxidative stress), roles, mechanisms of action and receptors). Furthermore, both conventional and recently emerging methods developed for the industrial production of HA and its chemical derivatization are presented. Finally, the medical, pharmaceutical and cosmetic applications of HA and its derivatives are reviewed, reporting examples of HA-based products that currently are on the market or are undergoing further investigations.

Hyaluronic Acid: Molecular Mechanisms and Therapeutic Trajectory.

Hyaluronic acid (also known as hyaluronan or hyaluronate) is naturally found in many tissues and fluids, but more abundantly in articular cartilage and synovial fluid (SF). Hyaluronic acid (HA) content varies widely in different joints and species. HA is a non-sulfated, naturally occurring non-protein glycosaminoglycan (GAG), with distinct physico-chemical properties, produced by synoviocytes, fibroblasts, and chondrocytes. HA has an important role in the biomechanics of normal SF, where it is partially responsible for lubrication and viscoelasticity of the SF. The concentration of HA and its molecular weight (MW) decline as osteoarthritis (OA) progresses with aging. For that reason, HA has been used for more than four decades in the treatment of OA in dogs, horses and humans. HA produces anti-arthritic effects via multiple mechanisms involving receptors, enzymes and other metabolic pathways. HA is also used in the treatment of ophthalmic, dermal, burns, wound repair, and other health conditions. The MW of HA appears to play a critical role in the formulation of the products used in the treatment of diseases. This review provides a mechanism-based rationale for the use of HA in some disease conditions with special reference to OA.

Advantages of Hyaluronic Acid and Its Combination with Other Bioactive Ingredients in Cosmeceuticals.

This study proposes a review on hyaluronic acid (HA) known as hyaluronan or hyaluronate and its derivates and their application in cosmetic formulations. HA is a glycosaminoglycan constituted from two disaccharides (N-acetylglucosamine and D-glucuronic acid), isolated initially from the vitreous humour of the eye, and subsequently discovered in different tissues or fluids (especially in the articular cartilage and the synovial fluid). It is ubiquitous in vertebrates, including humans, and it is involved in diverse biological processes, such as cell differentiation, embryological development, inflammation, wound healing, etc. HA has many qualities that recommend it over other substances used in skin regeneration, with moisturizing and anti-ageing effects. HA molecular weight influences its penetration into the skin and its biological activity. Considering that, nowadays, hyaluronic acid has a wide use and a multitude of applications (in ophthalmology, arthrology, pneumology, rhinology, aesthetic medicine, oncology, nutrition, and cosmetics), the present study describes the main aspects related to its use in cosmetology. The biological effect of HA on the skin level and its potential adverse effects are discussed. Some available cosmetic products containing HA have been identified from the brand portfolio of most known manufacturers and their composition was evaluated. Further, additional biological effects due to the other active ingredients (plant extracts, vitamins, amino acids, peptides, proteins, saccharides, probiotics, etc.) are presented, as well as a description of their possible toxic effects.

Hyaluronan.

Hyaluronan (hyaluronic acid) is a high-molecular-mass polysaccharide found in the extracellular matrix, especially of soft connective tissues. It is synthesized in the plasma membrane of fibroblasts and other cells by addition of sugars to the reducing end of the polymer, whereas the nonreducing end protrudes into the pericellular space. The polysaccharide is catabolized locally or carried by lymph to lymph nodes or the general circulation, from where it is cleared by the endothelial cells of the liver sinusoids. The overall turnover rate is surprisingly rapid for a connective tissue matrix component (t1/2 0.5 to a few days). Hyaluronan has been assigned various physiological functions in the intercellular matrix, e.g., in water and plasma protein homeostasis. Hyaluronan production increases in proliferating cells and the polymer may play a role in mitosis. Extensive hyaluronidase-sensitive coats have been identified around mesenchymal cells. They are either anchored firmly in the plasma membrane or bound via hyaluronan-specific binding proteins (receptors). Such receptors have now been identified on many different cells, e.g., the lymphocyte homing receptor CD 44. Interaction between a hyaluronan receptor and extracellular polysaccharide has been connected with locomotion and cell migration. Hyaluronan seems to play an important role during development and differentiation and has other cell regulatory activities. Hyaluronan has also been recognized in clinical medicine. A concentrated solution of hyaluronan (10 mg/ml) has, through its tissue protective and rheological properties, become a device in ophthalmic surgery. Analysis of serum hyaluronan is promising in the diagnosis of liver disease and various inflammatory conditions, e.g., rheumatoid arthritis. Interstitial edema caused by accumulation of hyaluronan may cause dysfunction in various organs.

Hyaluronic acid and tissue mechanics orchestrate mammalian digit tip regeneration.

Tissue regeneration is rare in mammals, but the digit tip can regrow after amputation, whereas injuries beyond the nail do not. How the microenvironment drives divergent outcomes remains unclear. In this study, we found that the extracellular matrix (ECM) and tissue mechanics govern the amputation response in mouse digits. Nonregenerative regions were stiffer and contained dense, organized collagen, whereas regenerative regions were soft and enriched in hyaluronic acid (HA). Depleting HA inhibited regeneration and promoted fibrosis, demonstrating that the HA-collagen balance shaped tissue mechanics and repair signaling. Stabilization of HA with hyaluronan and proteoglycan link protein 1 (HAPLN1) after nonregenerative amputations tuned ECM mechanics, reduced scarring, and enhanced bone repair. Thus, ECM composition and mechanics influence cell behavior and ECM-targeted strategies could help unlock mammalian regeneration.

Crosslinking hyaluronic acid soft-tissue fillers: current status and perspectives from an industrial point of view.

Hyaluronan (HA)-based soft-tissue fillers are injectable crosslinked hydrogels aimed to counteract facial skin aging signs via minimally invasive procedures. The crosslinking step is required to drastically improve HA residence time in vivo and provide the gel with specific viscoelastic properties matching the clinical indications. While HA as a raw material and HA fillers are widely studied, little is reported about crosslinkers themselves used in commercial fillers. This article introduces the specifications of the ideal crosslinker in HA fillers. The properties of commercially used crosslinkers are reviewed. An up-to-date review of innovative hydrogel fabrication alternatives is conducted, and advantages and drawbacks are discussed. HA fillers are predominantly manufactured using 1,4-butanediol diglycidyl ether (BDDE) which is considered as the gold standard crosslinker worldwide due to its proven and unrivaled clinical track record of more than 20 years. Extensive studies have been published covering BDDE-crosslinked HA fillers' chemistry, gel properties, and clinical effectiveness and safety. However, new hydrogel fabrication strategies have emerged, paving the way for innovative alternatives potentially bringing novel features to HA fillers. Nevertheless, major efforts must still be implemented to assess their safety, efficacy, stability and suitability for industrialization.

Naked mole-rat hyaluronan.

Naked mole rats (NMRs) are renowned for their exceptional longevity and remarkable maintenance of health throughout their lifetime. Their subterranean lifestyle has led to adaptations that have resulted in elevated levels of a very high molecular weight hyaluronan in their tissues. Hyaluronan, a glycosaminoglycan, is a key component of the extracellular matrix, which plays a critical role in maintaining tissue structure and regulating cell signaling pathways. This phenomenon in NMRs is attributed to a higher processing and production capacity by some of their hyaluronan synthases, along with lower degradation by certain hyaluronidases. Furthermore, this adaptation indirectly confers several advantages to NMRs, such as the preservation of skin elasticity and youthful appearance, accelerated wound healing, protection against oxidative stress, and resistance to conditions such as cancer and arthritis, largely attributable to CD44 signaling and other intricate mechanisms. Thus, the main objective of this study was to conduct a comprehensive study of the distinctive features of NMR hyaluronan, particularly emphasizing the currently known molecular mechanisms that contribute to its beneficial properties. Furthermore, this research delves into the potential applications of NMR hyaluronan in both cosmetic and therapeutic fields, as well as the challenges involved.

Oral administration of hyaluronic acid to improve skin conditions via a randomized double-blind clinical test.

To evaluate the impact of oral intake of Hyaluronic Acid (HA) on skin health. HA, an endogenous substance in the human body, plays a key role in skin health. However, its concentration in the skin decreases significantly with age. Previous studies suggested that oral intake of HA can supplement the body's HA level, but did not reveal the effects on different age groups and skin types. A double-blind, randomized clinical trial with 129 female participants, covering young and elderly groups and differnet skin types, was conducted to assess the efficacy of orally administered HA on skin health. Oral administration of HA significantly promoted skin hydration after 2-8 weeks among both young and elderly groups. Skin tone improvement was observed after 4-8 weeks, while an increase in epidermal thickness was noted after 12 weeks. This study provides direct evidence supporting the clinical efficacy of oral intake of HA in promoting skin health.

Hyaluronic Acid in Rheumatology.

Hyaluronic acid (HA), also known as hyaluronan, is an anionic glycosaminoglycan widely distributed throughout various tissues of the human body. It stands out from other glycosaminoglycans as it lacks sulfation and can attain considerable size: the average human synovial HA molecule weighs about 7 million Dalton (Da), equivalent to roughly 20,000 disaccharide monomers; although some sources report a lower range of 3-4 million Da. In recent years, HA has garnered significant attention in the field of rheumatology due to its involvement in joint lubrication, cartilage maintenance, and modulation of inflammatory and/or immune responses. This review aims to provide a comprehensive overview of HA's involvement in rheumatology, covering its physiology, pharmacology, therapeutic applications, and potential future directions for enhancing patient outcomes. Nevertheless, the use of HA therapy in rheumatology remains controversial with conflicting evidence regarding its efficacy and safety. In conclusion, HA represents a promising therapeutic option to improve joint function and alleviate inflammation and pain.

Matrix engineering.

Matrix engineering is a technology that utilizes hyaluronan (HA, hyaluronic acid) based matrices to control, direct or augment tissue regenerative processes. Hyaluronan and the concept of matrix engineering have become established tools in ophthalmic and orthopaedic medicine. The clinical indications for HA are limited by the physical properties and short residence time of the natural HA molecule. To expand and improve upon its current medical applications, a family of HA derivatives was prepared by chemical modification and cross-linking. Relative to the non-modified HA molecule, the hylan family of polymers provides more versatile physical forms, improved mechanical properties and an extended residence time. Hylan can also be used as a surface coating to improve blood compatibility. The chemical, physical and biological properties of hylans will be reviewed, focusing on the specific therapeutic indications they enable.

Hyaluronan: an overview.

Hyaluronic acid (HA) is a polyanionic natural polymer occurring as a linear polysaccharide composed of glucuronic acid and N-acetylglucosamine repeats. Hyaluronic acid has a wide range of applications with its excellent physicochemical properties such as biodegradability, biocompatibility, non-toxicity, non-immunogenicity and serves as an excellent tool in biomedical applications such as osteoarthritis surgery, ocular surgery, plastic surgery, tissue engineering and drug delivery. This work provides an overview on hyaluronic acid, its chemistry and biochemistry and its medical applications.

Marine Biomaterials: Hyaluronan.

The marine-derived hyaluronic acid and other natural biopolymers offer exciting possibilities in the field of biomaterials, providing sustainable and biocompatible alternatives to synthetic materials. Their unique properties and abundance in marine sources make them valuable resources for various biomedical and industrial applications. Due to high biocompatible features and participation in biological processes related to tissue healing, hyaluronic acid has become widely used in tissue engineering applications, especially in the wound healing process. The present review enlightens marine hyaluronan biomaterial providing its sources, extraction process, structures, chemical modifications, biological properties, and biocidal applications, especially for wound healing/dressing purposes. Meanwhile, we point out the future development of wound healing/dressing based on hyaluronan and its composites and potential challenges.

Biochemistry of hyaluronan.

Hyaluronan (hyaluronic acid) is a linear polysaccharide formed from disaccharide units containing N-acetylglucosamine and glucuronic acid. It is ubiquitously distributed in the organism but is found in the highest concentrations in soft connective tissues. The molecular weight of hyaluronan is usually in the order of 10(6) to 10(7). Due to hydrogen bonding, the chain is rather stiff and the molecule behaves in solution as an extended, randomly kinked coil. Molecules of hyaluronan start to entangle already at concentrations of less than 1 g/l and form a continuous polymer network. Some of the functions of the polysaccharide have been connected with the unique physical chemical characteristics of the network such as its rheological properties, flow resistance, osmotic pressure, exclusion properties and filter effect. Hyaluronan is synthesized in the cell membrane by adding monosaccharides to the reducing end of the chain. The precursors are UDP-glucuronic acid and UDP-N-acetylglucosamine. The polysaccharide grows out from the cell surface and it can be shown that fibroblasts, for example, surround themselves with a coat of hyaluronan. The rate of biosynthesis is regulated by various factors, such as growth factors, hormones, inflammatory mediators, etc. The responsible enzyme, hyaluronan synthase, is a phosphoprotein and the regulation of the synthetic rate is apparently via phosphorylation. The hyaluronan is at least partly carried by lymph flow from the tissues. Part of the material is taken up and degraded in the lymph nodes. Another part is carried to the general circulation and taken up in the endothelial cells in the liver sinusoids. These cells have specific receptors for hyaluronan, which also recognize chondroitin sulphate. The uptake in the liver of high-molecular weight hyaluronan is very efficient and its normal half-life in serum is only in the order of 2 to 5 min. The polysaccharide is rapidly degraded in the lysosomes to low-molecular weight products, lactate and acetate. The total turnover of hyaluronan in serum is in the order of 10-100 mg/24 h. The normal concentration of hyaluronan in serum is less than 100 micrograms/l with a mean of 30-40 micrograms/l. High serum levels have been noted in liver cirrhosis (impaired uptake in the liver) and rheumatoid arthritis (increased synthesis in the tissues). Hyaluronan has been shown to interact specifically with certain proteins and cell surfaces. It binds to proteoglycans in cartilage and other tissues and fills an important structural role in the organization of the extra-cellular matrix.(ABSTRACT TRUNCATED AT 400 WORDS)

Beneficial effects of hyaluronic acid.

Biomaterials are playing a vital role in our day-to-day life. Hyaluronan (hyaluronic acid), a biomaterial, receives special attention among them. Hyaluronic acid (HA) is a polyanionic natural polymer occurring as linear polysaccharide composed of glucuronic acid and N-acetylglucosamine repeats via a β-1,4 linkage. It is the most versatile macromolecule present in the connective tissues of all vertebrates. Hyaluronic acid has a wide range of applications with its excellent physicochemical properties such as biodegradability, biocompatibility, nontoxicity, and nonimmunogenicity and serves as an excellent tool in biomedical applications such as osteoarthritis surgery, ocular surgery, plastic surgery, tissue engineering, and drug delivery. It plays a key role in cushioning and lubricating the body and is abundant in the eyes, joints, and heart valves. A powerful antioxidant, hyaluronic acid is perhaps best known for its ability to bond water to tissue. Hyaluronan production increases in proliferating cells, and the polymer may play a role in mitosis. This chapter gives an overview of hyaluronic acid and its physicochemical properties and applications. This chapter gives a deep understanding on the special benefits of hyaluronic acid in the fields of pharmaceutical, medical, and environmental applications. Hyaluronic acid paves the way for beneficial research and applications to the welfare of life forms.

Hyaluronan and the Fascial Frontier.

The buzz about hyaluronan (HA) is real. Whether found in face cream to increase water volume loss and viscoelasticity or injected into the knee to restore the properties of synovial fluid, the impact of HA can be recognized in many disciplines from dermatology to orthopedics. HA is the most abundant polysaccharide of the extracellular matrix of connective tissues. HA can impact cell behavior in specific ways by binding cellular HA receptors, which can influence signals that facilitate cell survival, proliferation, adhesion, as well as migration. Characteristics of HA, such as its abundance in a variety of tissues and its responsiveness to chemical, mechanical and hormonal modifications, has made HA an attractive molecule for a wide range of applications. Despite being discovered over 80 years ago, its properties within the world of fascia have only recently received attention. Our fascial system penetrates and envelopes all organs, muscles, bones and nerve fibers, providing the body with a functional structure and an environment that enables all bodily systems to operate in an integrated manner. Recognized interactions between cells and their HA-rich extracellular microenvironment support the importance of studying the relationship between HA and the body's fascial system. From fasciacytes to chronic pain, this review aims to highlight the connections between HA and fascial health.

Antibodies against hyaluronan oligosaccharides in xenotransplantation.

Carbohydrate-specific antibodies are significant mediators of xenograft rejection. This study analyzed the carbohydrate specificity of antibodies in baboons before and after xenotransplantation of organs or injection of porcine red blood cells from hDAF transgenic pigs, using a glycan array with structurally defined glycans. Antibodies against hyaluronic acid disaccharide (HA2) showed the highest reactivity at baseline and rose after xenogeneic exposure. We also investigated in the serum of baboons that underwent xenotransplantation with either hDAF or hDAF/hMCP transgenic pig organs and Lewis rats after hamster-skin xenotransplantation the specificity of anti-HA antibodies on a glycan microarray representing HA oligosaccharides containing from two to 40 saccharides. Notably, the HA oligosaccharides ranging from 32 to 40 saccharides exhibited the highest antibody binding intensities at baseline in baboon and rat sera. After xenotransplantation, antibodies against HA38 and HA40 in baboons, and HA32, HA34, and HA36 in rats showed the highest titer increases. The changes of anti-HA IgM and IgG antibodies in rats after skin xenotransplantation was also confirmed by an ELISA specific for HA2, HA24, and HA85 antibodies. Thus, xenotransplantation is associated with increased antibodies against HA-oligosaccharides, which may represent a new target for intervention.

Hyaluronic acid: Still useful in knee osteoarthritis?

Viscosupplementation for osteoarthritis.

Viscosupplementation therapy can restore the elastic and viscous properties of synovial fluid and thus recreate the intra-articular joint homeostasis that is disrupted in the degenerative joint. Hyaluronan (hyaluronic acid) products have been developed and used for viscosupplementation therapy in osteoarthritis. Viscosupplementation treatments using these products are well tolerated. Because viscosupplementation therapy is based on the concept of replenishing a normal physiological component of synovial fluid and cartilaginous tissue, exogenous administration of hyaluronic acid has the potential to have few side effects or local or systemic reactions. Viscosupplementation represents an alternative treatment for patients with osteoarthritis in which oral medications and/or surgery are not options or are ineffective.

Hyaluronic acid (hyaluronan) in experimental osteoarthritis.

We studied the effects of intraarticular (ia) administration of hyaluronic acid (HA) (Mw approximately 9 x 10(5)) (Artz) on cartilage integrity and release into synovial fluid (SF) of keratan sulfate peptides (KS-pep) in an ovine model of early osteoarthritis (OA) induced by meniscectomy. Five consecutive weekly injections of HA (2 ml, 10 mg/ml) or saline (2 ml) were initiated 16 weeks after meniscectomy, and animals were sacrificed 5 weeks after the last injection. SF was sampled 8, 16, 23, and 26 weeks postoperation. In the saline injected animals KS-pep levels increased progressively in SF, relative to nonoperated controls (p < 0.05). KS-pep levels in SF of the HA treated group also increased, but were not statistically different from controls. Using a modified Mankin histological scoring system, cartilage at necropsy of HA injected joints showed less damage than similar regions of saline treated animals. A new mechanism for the protective effects of HA on cartilage is proposed.

Hyaluronan as a therapeutic target in human diseases.

Accumulation and turnover of extracellular matrix is a hallmark of tissue injury, repair and remodeling in human diseases. Hyaluronan is a major component of the extracellular matrix and plays an important role in regulating tissue injury and repair, and controlling disease outcomes. The function of hyaluronan depends on its size, location, and interactions with binding partners. While fragmented hyaluronan stimulates the expression of an array of genes by a variety of cell types regulating inflammatory responses and tissue repair, cell surface hyaluronan provides protection against tissue damage from the environment and promotes regeneration and repair. The interactions of hyaluronan and its binding proteins participate in the pathogenesis of many human diseases. Thus, targeting hyaluronan and its interactions with cells and proteins may provide new approaches to developing therapeutics for inflammatory and fibrosing diseases. This review focuses on the role of hyaluronan in biological and pathological processes, and as a potential therapeutic target in human diseases.

Hyaluronic acid production and characterization by novel Bacillus subtilis harboring truncated Hyaluronan Synthase.

Hyaluronic Acid (HA) is a natural biopolymer that has important physiological and industrial applications due to its viscoelastic and hydrophilic characteristics. The responsible enzyme for HA production is Hyaluronan synthase (HAS). Although in vitro structure-function of intact HAS enzyme has been partly identified, there is no data on in vivo function of truncated HAS forms. In the current study, novel recombinant Bacillus subtilis strains harboring full length (RBSFA) and truncated forms of SeHAS (RBSTr4 and RBSTr3) were developed and HA production was studied in terms of titer, production rate and molecular weight (Mw). The maximum HA titer for RBSFA, RBSTr4&#xa0;and RBSTr3 was 602&#x2009;&#xb1;&#x2009;16.6, 503&#x2009;&#xb1;&#x2009;19.4 and 728&#x2009;&#xb1;&#x2009;22.9&#xa0;mg/L, respectively. Also, the HA production rate was 20.02, 15.90 and 24.42&#xa0;mg/L.h-1, respectively. The findings revealed that RBSTr3 produced 121% and 137% more HA rather than RBSFA and RBSTr4, respectively. More interestingly, the HA Mw was about 60&#xa0;kDa for all strains which is much smaller than those obtained in prior studies.

Hyaluronan (hyaluronic acid) in human saliva.

Hyaluronan (hyaluronic acid) is a glycosaminoglycan that functions as a constituent of ground substance, a mediator of cell proliferation and would healing, and that plays a prominent part in tumorigenesis as well as in embryogenesis. Its presence and possible role in saliva has been subjected to little study. Unstimulated and stimulated pure parotid and mixed saliva was obtained from 10 volunteers. The protein content of the samples was assayed and the hyaluronan concentration was evaluated by means of an enzyme immunosorbent-like assay using a hyaluronan-binding peptide. Stimulated whole saliva had the highest protein content (mean 1.26 mg/ml) followed by unstimulated parotid saliva (1.15 mg/ml), stimulated parotid saliva (0.95 mg/ml) and unstimulated whole saliva (0.93 mg/ml). Absolute hyaluronan concentrations were highest in unstimulated whole saliva (mean 459.2 ng (nanograms)/ml), and lowest in stimulated parotid saliva (82.7 ng/ml). When hyaluronan concentrations are expressed as ng/mg of protein, the highest are in the unstimulated whole saliva (mean 477.5 ng/mg protein) followed by stimulated parotid saliva (229.7 ng/mg), unstimulated parotid saliva (179.6 ng/mg) and stimulated whole saliva (159.9 ng/mg). There are wide variations in the levels of hyaluronan in human saliva depending on the type of saliva and the conditions at the time of collection. Regulation of hyaluronan metabolism represents an intricate balance between production and degradation, and it is unclear whether elevated concentrations of hyaluronan in response to tissue proliferation, regeneration or repair. The hyaluronan may contribute to the healing properties of saliva, assisting in protecting the oral mucosa and adding to the lubricating properties of saliva.

Ligand Binding and Signaling of HARE/Stabilin-2.

The Stabilin receptors are a two-member family in the type H class of scavenger receptors. These dynamic receptors bind and internalize multiple ligands from the cell surface for the purpose of clearing extracellular material including some synthetic drugs and for sensing the external environment of the cell. Stabilin-1 was the first receptor to be cloned, though the biological activity of Hyaluronic Acid Receptor for Endocytosis (HARE)/Stabilin-2 was observed about 10 years prior to the cloning of Stabilin-1. Stabilin-1 has a more diverse expression profile among the tissues than HARE/Stabilin-2. This review will focus on HARE/Stabilin-2 and its interactions with hyaluronan, heparin, and phosphorothioate antisense oligonucleotides and what is known about how this receptor participates in signaling upon ligand binding.

Hyaluronan-Cyclodextrin Conjugates as Doxorubicin Delivery Systems.

In the last years, nanoparticles based on cyclodextrins have been widely investigated for the delivery of anticancer drugs. In this work, we synthesized nanoparticles with a hyaluronic acid backbone functionalized with cyclodextrins under green conditions. We functionalized hyaluronic acid with two different molecular weights (about 11 kDa and 45 kDa) to compare their behavior as doxorubicin delivery systems. We found that the new hyaluronan-cyclodextrin conjugates increased the water solubility of doxorubicin. Moreover, we tested the antiproliferative activity of doxorubicin in the presence of the new cyclodextrin polymers in SK-N-SH and SK-N-SH-PMA (over-expressing CD44 receptor) cancer cells. We found that hyaluronan-cyclodextrin conjugates improved the uptake and antiproliferative activity of doxorubicin in the SK-N-SH-PMA compared to the SK-N-SH cell line at the ratio 8/1 doxorubicin/polymer. Notably, the system based on hyaluronan (45 kDa) was more effective as a drug carrier and significantly reduced the IC50 value of doxorubicin by about 56%. We also found that hyaluronic acid polymers determined an improved antiproliferative activity of doxorubicin (IC50 values are on average reduced by about 70% of free DOXO) in both cell lines at the ratio 16/1 doxorubicin/polymer.

Hyaluronic Acid and Controlled Release: A Review.

Hyaluronic acid (HA) also known as hyaluronan, is a natural polysaccharide-an anionic, non-sulfated glycosaminoglycan-commonly found in our bodies. It occurs in the highest concentrations in the eyes and joints. Today HA is used during certain eye surgeries and in the treatment of dry eye disease. It is a remarkable natural lubricant that can be injected into the knee for patients with knee osteoarthritis. HA has also excellent gelling properties due to its capability to bind water very quickly. As such, it is one the most attractive controlled drug release matrices and as such, it is frequently used in various biomedical applications. Due to its reactivity, HA can be cross-linked or conjugated with assorted bio-macromolecules and it can effectively encapsulate several different types of drugs, even at nanoscale. Moreover, the physiological significance of the interactions between HA and its main membrane receptor, CD44 (a cell-surface glycoprotein that modulates cell-cell interactions, cell adhesion and migration), in pathological processes, e.g. cancer, is well recognized and this has resulted in an extensive amount of studies on cancer drug delivery and tumor targeting. HA acts as a therapeutic but also as a tunable matrix for drug release. Thus, this review focuses on controlled or sustained drug release systems assembled from HA and its derivatives. More specifically, recent advances in controlled release of proteins, antiseptics, antibiotics and cancer targeting drugs from HA and its derivatives were reviewed. It was shown that controlled release from HA has many benefits such as optimum drug concentration maintenance, enhanced therapeutic effects, improved efficiency of treatment with less drug, very low or insignificant toxicity and prolonged in vivo release rates.

Particle diffusion in extracellular hydrogels.

Hyaluronic acid is an abundant polyelectrolyte in the human body that forms extracellular hydrogels in connective tissues. It is essential for regulating tissue biomechanics and cell-cell communication, yet hyaluronan overexpression is associated with pathological situations such as cancer and multiple sclerosis. Due to its enormous molecular weight (in the range of millions of Daltons), accumulation of hyaluronan hinders transport of macromolecules including nutrients and growth factors through tissues and also hampers drug delivery. However, the exact contribution of hyaluronan to tissue penetrability is poorly understood due to the complex structure and molecular composition of tissues. Here we reconstitute biomimetic hyaluronan gels and systematically investigate the effects of gel composition and crosslinking on the diffusion of microscopic tracer particles. We combine ensemble-averaged measurements via differential dynamic microscopy with single-particle tracking. We show that the particle diffusivity depends on the particle size relative to the network pore size and also on the stress relaxation dynamics of the network. We furthermore show that addition of collagen, the other major biopolymer in tissues, causes the emergence of caged particle dynamics. Our findings are useful for understanding macromolecular transport in tissues and for designing biomimetic extracellular matrix hydrogels for drug delivery and tissue regeneration.

Therapeutic roles of hyaluronan and synthases in cartilage.

Hyaluronan synthases (HASs) are essential enzymes for hyaluronic acid (HA) production; a key component for joint lubrication and cartilage health. Dysregulated HA synthesis contributes to joint dysfunction. In this Forum, we discuss the role of HAS in matrix assembly, inflammation and the pathogenesis of osteoarthritis (OA).

From modeling to remodeling of upper airways: Centrality of hyaluronan (hyaluronic acid).

After traumatic events (accidental or surgical), the respiratory tract activates specific and prolix repairing mechanisms which tend to claw back the primitive differentiated state. The attempt of reactivation of the normal tissue functions is called 'remodeling' and its aim is to reinstate the modeling mechanisms that existed before the damaging event or the pathology's establishment. Endoscopic sinus surgery represents the gold standard treatment for inflammatory, malformative, benign, and, in selected cases, malignant diseases. The surgical technique is commonly described as minimally invasive as the nostrils are used as an access route and therefore does not leave any external scars. Currently, the surgical procedures, even though minimally invasive regarding the way in, are in fact widely destructive towards the surgical target. The healing process and re-epithelialization will depend on the amount of bony tissue that has been exposed and it will be important to stratify the different surgical typologies in order to foresee the increasing difficulty of mucosal healing process. As far as upper inflammatory diseases are concerned, recent studies demonstrated how intranasal hyaluronic acid can positively regulate mucosal glands secretion and modulate inflammatory response, being a useful tool for the improvement of remodeling after endoscopic sinus surgery. Acid has shown to be able to regulate mucosal glands secretion and modulate the inflammatory response.

Emerging Therapies for Spastic Movement Disorders.

Spasticity develops as a result of central nervous system (CNS) injury; however, secondary changes within the muscles and connective tissue also contribute to muscle stiffness. The hyaluronan hypothesis postulates that the accumulation of hyaluronan promotes the development of muscle stiffness. Intramuscular injections of the enzyme hyaluronidase, which hydrolyzes long-chained hyaluronan polymers to smaller polymers, was shown to reduce muscle stiffness and increase passive and active range of motion in patients with spasticity. These results provide preliminary evidence of the hyaluronan hypothesis and suggest an emerging therapy to reduce muscle stiffness using the enzyme hyaluronidase.

Elastin-Hyaluronan Bioconjugate as Bioactive Component in Electrospun Scaffolds.

Hyaluronic acid or hyaluronan (HA) and elastin-inspired peptides (EL) have been widely recognized as bioinspired materials useful in biomedical applications. The aim of the present work is the production of electrospun scaffolds as wound dressing materials which would benefit from synergic action of the bioactivity of elastin peptides and the regenerative properties of hyaluronic acid. Taking advantage of thiol-ene chemistry, a bioactive elastin peptide was successfully conjugated to methacrylated hyaluronic acid (MAHA) and electrospun together with poly-D,L-lactide (PDLLA). To the best of our knowledge, limited reports on peptide-conjugated hyaluronic acid were described in literature, and none of these was employed for the production of electrospun scaffolds. The conformational studies carried out by Circular Dichroism (CD) on the bioconjugated compound confirmed the preservation of secondary structure of the peptide after conjugation while Scanning Electron Microscopy (SEM) revealed the supramolecular structure of the electrospun scaffolds. Overall, the study demonstrates that the bioconjugation of hyaluronic acid with the elastin peptide improved the electrospinning processability with improved characteristics in terms of morphology of the final scaffolds.

Hyaluronan or hylans for knee osteoarthritis?

In joints affected by osteoarthritis, the synovial fluid's capacity to lubricate and to absorb shock are typically reduced. These changes are partly due to a reduction in the size and concentration of hyaluronic acid (hyaluronan) molecules naturally present in synovial fluid. A new approach in the management of osteoarthritis of the knee is to inject hyaluronan or derivatives of this molecule (hylans) into the joint. We consider the place of two preparations: [symbol: see text]Hyalgan and Synvisc.

The significant role of glycosaminoglycans in tooth development.

This review delves into the roles of glycosaminoglycans (GAGs), integral components of proteoglycans, in tooth development. Proteoglycans consist of a core protein linked to GAG chains, comprised of repeating disaccharide units. GAGs are classified into several types, such as hyaluronic acid, heparan sulfate, chondroitin sulfate, dermatan sulfate, and keratan sulfate. Functioning as critical macromolecular components within the dental basement membrane, these GAGs facilitate cell adhesion and aggregation, and play key roles in regulating cell proliferation and differentiation, thereby significantly influencing tooth morphogenesis. Notably, our recent research has identified the hyaluronan-degrading enzyme Transmembrane protein 2 (Tmem2) and we have conducted functional analyses using mouse models. These studies have unveiled the essential role of Tmem2-mediated hyaluronan degradation and its involvement in hyaluronan-mediated cell adhesion during tooth formation. This review provides a comprehensive summary of the current understanding of GAG functions in tooth development, integrating insights from recent research, and discusses future directions in this field.

Hyaluronan-Conjugated Carbon Quantum Dots for Bioimaging Use.

This work demonstrates the application of hyaluronan-conjugated nitrogen-doped carbon quantum dots (HA-nCQDs) for bioimaging of tumor cells and illustrates their potential use as carriers in targeted drug delivery. Quantum dots are challenging to deliver with specificity, which hinders their application. To facilitate targeted internalization by cancer cells, hyaluronic acid, a natural ligand of CD44 receptors, was covalently grafted on nCQDs. The HA-nCQD conjugate was synthesized by carbodiimide coupling of the amine moieties on nCQDs and the carboxylic acids on HA chains. Conjugated HA-nCQD retained sufficient fluorescence, although with 30% lower quantum efficiency than the original nCQDs. Confocal microscopy showed enhanced internalization of HA-nCQDs, facilitated by CD44 receptors. To demonstrate the specificity of HA-nCQDs toward human tumor cells, patient-derived breast cancer tissue with high-CD44 expression was implanted in adult mice. The tumors were allowed to grow up to 200-250 mm3 prior to the injection of HA-nCQDs. With either local or systemic injection, we achieved a high level of tumor specificity judged by a strong signal-to-noise ratio between the tumor and the surrounding tissue in vivo. Overall, the results show that HA-nCQDs can be used for imaging of CD44-specific tumors in preclinical models of human cancer and potentially used as carriers for targeted drug delivery into CD44-rich cells.

The Hyaluronan/CD44 Axis: A Double-Edged Sword in Cancer.

Hyaluronic acid (HA) receptor CD44 is widely used for identifying cancer stem cells and its activation promotes stemness. Recent evidence shows that overexpression of CD44 is associated with poor prognosis in most human cancers and mediates therapy resistance. For these reasons, in recent years, CD44 has become a treatment target in precision oncology, often via HA-conjugated antineoplastic drugs. Importantly, HA molecules of different sizes have a dual effect and, therefore, may enhance or attenuate the CD44-mediated signaling pathways, as they compete with endogenous HA for binding to the receptors. The magnitude of these effects could be crucial for cancer progression, as well as for driving the inflammatory response in the tumor microenvironment. The increasingly common use of HA-conjugated drugs in oncology, as well as HA-based compounds as adjuvants in cancer treatment, adds further complexity to the understanding of the net effect of hyaluronan-CD44 activation in cancers. In this review, I focus on the significance of CD44 in malignancy and discuss the dichotomous function of the hyaluronan/CD44 axis in cancer progression.

Hyaluronic acid injections relieve knee pain.

To evaluate the efficacy of intra-articular viscosupplementation therapy with hyaluronic acid for pain relief of knee osteoarthritis, we conducted a meta-analysis of randomized, double-blinded, placebo-controlled trials. We searched systematically for randomized, double-blinded, placebo-controlled trials of hyaluronic acid (hyaluronan and hylan G-F20) for pain relief of knee osteoarthritis. Studies reporting pain visual analogue scale (VAS) differences were included in the meta-analysis. Changes in pain were measured by VAS for placebo and treatment, and summary estimates of the differences between the 2 arms were calculated at 1 week, 5 to 7 weeks, 8 to 12, and 15 to 22 weeks after the last intra-articular injection. Sources of heterogeneity were assessed using information on quality score, type of viscosupplementation, and VAS change in pain with activity or rest. Heterogeneity across the studies was significant in all analyses (P<.01); therefore a random effect model was used. Pain was measured either on activity or at rest. Eleven trials (9 hyaluronan and 2 hylan G-F 20) allowed calculation of the summary estimate of difference in change of VAS pain at 1 week, 6 of the 11 allowed the estimation between 5 to 7 weeks and 8 to 12 weeks, and only 3 at 15 to 22 weeks. The summary estimates of VAS differences between therapy and placebo injection: at 1 week, 4.4 (95% confidence interval [CI], 1.1-7.2); at 5 to 7 weeks, 17.7 (7.5-28.0); at 8 to 12 weeks, 18.1 (6.3-29.9) and at 15 to 22 weeks, 4.4 (-15.3 to 24.1). Intra-articular viscosupplementation was moderately effective in relieving knee pain in patients with osteoarthritis at 5 to 7 and 8 to 10 weeks after the last injection but not at 15 to 22 weeks.

Computational Study of Complex Formation between Hyaluronan Polymers and Polyarginine Peptides at Various Ratios.

Hyaluronic acid, a naturally occurring carbohydrate biopolymer in human tissues, finds wide application in cosmetics, medicine, and material science. Its anionic properties play a crucial role in its interaction with positively charged macromolecules and ions. Among these macromolecules, positively charged arginine molecules or polyarginine peptides demonstrate potential in drug delivery when complexed with hyaluronan. This study aimed to compare and elucidate the results of both experimental and computational investigations on the interactions between hyaluronic acid polymers and polyarginine peptides. Experimental findings revealed that by varying the length of polyarginine peptides and the molar ratio, it is possible to modulate the size, solubility, and stability of hyaluronan-arginine particles. To further explore these interactions, molecular dynamics simulations were conducted to model the complexes formed between hyaluronic acid polymers and arginine peptides. The simulations are considered in different molar ratios and lengths of polyarginine peptides. By analysis of the data, we successfully determined the shape and size of the resulting complexes. Additionally, we identified the primary driving forces behind complex formation and explained the observed variations in peptide interactions with hyaluronan.

Hyaluronic Acid-Based Bioconjugate Systems, Scaffolds, and Their Therapeutic Potential.

In recent years, the development of hyaluronic acid or hyaluronan (HA) based scaffolds, medical devices, bioconjugate systems have expanded into a broad range of research and clinical applications. Research findings over the last two decades suggest that the abundance of HA in most mammalian tissues with distinctive biological roles and chemical simplicity for modifications have made it an attractive material with a rapidly growing global market. Besides its use as native forms, HA has received much interest on so-called "HA-bioconjugates" and "modified-HA systems". In this review, the importance of chemical modifications of HA, underlying rationale approaches, and various advancements of bioconjugate derivatives with their potential physicochemical, and pharmacological advantages are summarized. This review also highlights the current and emerging HA-based conjugates of small molecules, macromolecules, crosslinked systems, and surface coating strategies with their biological implications, including their potentials and key challenges discussed in detail.

Analysis of hyaluronan and its derivatives using chromatographic and mass spectrometric techniques.

The aim of this paper is to review chromatographic and mass-spectrometric methods and underline the best analytical approaches for successful analysis of various hyaluronic acid species in different types of samples. Hyaluronan-degrading enzymes and chemical depolymerization produce di- or oligosaccharides suitable for hyaluronan quantification or structural characterization of hyaluronan derivatives. Efficient purification and pre-column derivatization of hyaluronan disaccharides by reductive amination allow subnanogram quantification in biological samples. The chromatographic separation is capable to distinguish all glycosaminoglycans disaccharides and to resolve hyaluronan fragments with 2-40 monomers. Using electrospray ionization or matrix assisted laser desorption ionization, hyaluronan fragments up to 8 kDa or 41 kDa, respectively, can be observed. One- or two-dimensional chromatographic separation with higly sensitive mass-spectrometric detection is an indispensable tool for revealing substituent position, extent of modification and substitution patterns of chemically modified hyaluronan derivatives. It is essential for studying structure-biological function relationships of hyaluronan and its derivatives.

Intra-articular hyaluronan (hyaluronic acid) and hylans for the treatment of osteoarthritis: mechanisms of action.

Although the predominant mechanism of intra-articular hyaluronan (hyaluronic acid) (HA) and hylans for the treatment of pain associated with knee osteoarthritis (OA) is unknown, in vivo, in vitro, and clinical studies demonstrate various physiological effects of exogenous HA. HA can reduce nerve impulses and nerve sensitivity associated with the pain of OA. In experimental OA, this glycosaminoglycan has protective effects on cartilage, which may be mediated by its molecular and cellular effects observed in vitro. Exogenous HA enhances chondrocyte HA and proteoglycan synthesis, reduces the production and activity of proinflammatory mediators and matrix metalloproteinases, and alters the behavior of immune cells. Many of the physiological effects of exogenous HA may be a function of its molecular weight. Several physiological effects probably contribute to the mechanisms by which HA and hylans exert their clinical effects in knee OA.

Role of hyaluronic acid in periodontal therapy (Review).

Hyaluronic acid (HA) is essential for the function of extracellular matrices in both hard and soft periodontal components. HA plays an important role in the mechanisms underlying inflammation and wound healing. HA is located in periodontal tissues in differing amounts, including non-mineralized tissues, such as gingiva and periodontal ligament, and lower levels located in mineralized tissues, such as cementum and alveolar bone. According to preliminary findings, HA exhibits potential in the regulation of periodontal tissue regeneration and in the treatment of periodontal disease. HA promotes symptomatic relief in both marginal gingiva and deeper periodontal tissues. The present review aimed to examine the role of HA in periodontal therapy, and investigate the current literature supporting its use in periodontal regeneration.