Effectiveness of topical hyaluronic acid of different molecular weights in xerosis cutis treatment in elderly: a double-blind, randomized controlled trial

Dry skin is a common dermatological condition that frequently affects the elderly. A contributing cause to dry skin is a reduced concentration of hyaluronic acid (HA) in both the epidermis and dermis. The effectiveness of moisturizer containing HA as a therapy for dry skin is impacted by its specific molecular weight. Low molecular weight HA (LMWHA) is believed to be more effective in replenishing skin hydration in aging skin compared to High Molecular Weight HA (HMWHA) due to its ability to penetrate the stratum corneum. However, there is a lack of clinical research supporting this claim. A double-blind, randomized controlled trial was conducted on 36 residents of a nursing home in Jakarta. The participants, aged between 60 and 80 years, had been diagnosed with dry skin. Each test subject was administered three distinct, randomized moisturizing lotions (LMWHA, HMWHA, or vehicle), to be topically applied to three separate sites on the leg. Skin capacitance (SCap), transepidermal water loss (TEWL), and specified symptom sum score (SRRC) were measured at weeks 0, 2, and 4. After four weeks of therapy, area that was treated with LMWHA showed greater SCap values compared to the area treated with HMWHA (56.37 AU vs. 52.37 AU, p = 0.004) and vehicle (56.37 AU vs. 49.01 AU, p < 0.001). All groups did not show any significant differences in TEWL and SRRC scores. No side effects were found in all groups. The application of a moisturizer containing LMWHA to the dry skin of elderly resulted in significant improvements in skin hydration compared to moisturizers containing HMWHA and vehicle. Furthermore, these moisturizers demonstrated similar safety in treating dry skin in the elderly. ClinicalTrials.gov Identifier NCT06178367, https://clinicaltrials.gov/study/NCT06178367 .

Adverse reactions to cosmetic implants after COVID-19 vaccination: A literature review

BACKGROUND

As the world's population of people vaccinated with the COVID-19 vaccine increases, adverse reactions are increasingly being reported. There have been progressive reports of the effects of COVID-19 vaccination on cosmetic fillers or prostheses, but they have not been reviewed based on their clinical morphologic patterns. This article reviewed the progress of research on adverse reactions to cosmetic implants after COVID-19 vaccination.

METHODS

We researched the English-language literature up to October 15, 2022, using predefined keywords to identify relevant studies about adverse reactions to cosmetic implants after the COVID-19 vaccination, collecting patient characteristics, implant type, the time interval between vaccination and implantation or injection, time of onset, symptoms, treatments, and outcomes.

RESULTS

Among the adverse reactions to implants associated with COVID-19 vaccination, we distinguished between (1) injectable fillers and (2) surgical prosthetic implants. The most common adverse reactions were at the site of hyaluronic acid injection and breast prosthesis after Pfizer vaccination, mainly DIRs, and mainly manifested as edema, rash, fever, and capsular contracture. This paper also reported the possible causes, treatments of DIRs, and limitations of current studies.

CONCLUSIONS

In this article, we attempted to investigate and discuss all the adverse reactions of cosmetic implants related to COVID-19 vaccination in the current literature, to unmask these reactions and make a more accurate assessment of vaccine safety.

Tmem2 Deficiency Leads to Enamel Hypoplasia and Soft Enamel in Mouse

Teeth consist of 3 mineralized tissues: enamel, dentin, and cementum. Tooth malformation, the most common craniofacial anomaly, arises from complex genetic and environmental factors affecting enamel structure, size, shape, and tooth eruption. Hyaluronic acid (HA), a primary extracellular matrix component, contributes to structural and physiological functions in periodontal tissue. Transmembrane protein 2 (TMEM2), a novel cell surface hyaluronidase, has been shown to play a critical role during embryogenesis. In this study, we demonstrate Tmem2 messenger RNA expression in inner enamel epithelium and presecretory, secretory, and mature ameloblasts. Tmem2 knock-in reporter mice reveal TMEM2 protein localization at the apical and basal ends of secretory ameloblasts. Micro-computed tomography analysis of epithelial-specific Tmem2 conditional knockout (Tmem2-CKO) mice shows a significant reduction in enamel layer thickness and severe enamel deficiency. Enamel matrix protein expression was remarkably downregulated in Tmem2-CKO mice. Scanning electron microscopy of enamel from Tmem2-CKO mice revealed an irregular enamel prism structure, while the microhardness and density of enamel were significantly reduced, indicating impaired ameloblast differentiation and enamel matrix mineralization. Histological evaluation indicated weak adhesion between cells and the basement membrane in Tmem2-CKO mice. The reduced and irregular expressions of vinculin and integrin β1 suggest that Tmem2 deficiency attenuated focal adhesion formation. In addition, abnormal HA accumulation in the ameloblast layer and weak claudin 1 immunoreactivity in Tmem2-CKO mice indicate impaired tight junction gate function. Irregular actin filament assembly was also observed at the apical and basal ends of secretory ameloblasts. Last, we demonstrated that Tmem2-deficient mHAT9d mouse ameloblasts exhibit defective adhesion to HA-containing substrates in vitro. Collectively, our data highlight the importance of TMEM2 in adhesion to HA-rich extracellular matrix, cell-to-cell adhesion, ameloblast differentiation, and enamel matrix mineralization.

The Effects of Mucopolysaccharide Polysulfate on Steroid-Induced Tight Junction Barrier Dysfunction in Human Epidermal Keratinocytes and a 3D Skin Model

INTRODUCTION

The long-term use of topical corticosteroids (TCS) is associated with side effects such as skin atrophy and barrier deterioration. Moisturizers, such as mucopolysaccharide polysulfate (MPS), have been reported to prevent relapses in atopic dermatitis (AD) when used in combination with TCS. However, the mechanisms underlying the positive effects of MPS in combination with TCS in AD are poorly understood. In the present study, we investigated the effects of MPS in combination with clobetasol 17-propionate (CP) on tight junction (TJ) barrier function in human epidermal keratinocytes (HEKa) and 3D skin models.

METHODS

The expression of claudin-1, which is crucial for TJ barrier function in keratinocytes, and transepithelial electrical resistance (TEER) was measured in CP-treated human keratinocytes incubated with and without MPS. A TJ permeability assay, using Sulfo-NHS-Biotin as a tracer, was also conducted in a 3D skin model.

RESULTS

CP reduced claudin-1 expression and TEER in human keratinocytes, whereas MPS inhibited these CP-induced effects. Moreover, MPS inhibited the increase in CP-induced TJ permeability in a 3D skin model.

CONCLUSION

The present study demonstrated that MPS improved TJ barrier impairment induced by CP. The improvement of TJ barrier function may partially be responsible for the delayed relapse of AD induced by the combination of MPS and TCS.

Coating Methods of Carbon Nonwovens with Cross-Linked Hyaluronic Acid and Its Conjugates with BMP Fragments

The cross-linking of polysaccharides is a universal approach to affect their structure and physical properties. Both physical and chemical methods are used for this purpose. Although chemical cross-linking provides good thermal and mechanical stability for the final products, the compounds used as stabilizers can affect the integrity of the cross-linked substances or have toxic properties that limit the applicability of the final products. These risks might be mitigated by using physically cross-linked gels. In the present study, we attempted to obtain hybrid materials based on carbon nonwovens with a layer of cross-linked hyaluronan and peptides that are fragments of bone morphogenetic proteins (BMPs). A variety of cross-linking procedures and cross-linking agents (1,4-butanediamine, citric acid, and BDDE) were tested to find the most optimal method to coat the hydrophobic carbon nonwovens with a hydrophilic hyaluronic acid (HA) layer. Both the use of hyaluronic acid chemically modified with BMP fragments and a physical modification approach (layer-by-layer method) were proposed. The obtained hybrid materials were tested with the spectrometric (MALDI-TOF MS) and spectroscopic methods (IR and 1H-NMR). It was found that the chemical cross-linking of polysaccharides is an effective method for the deposition of a polar active substance on the surface of a hydrophobic carbon nonwoven fabric and that the final material is highly biocompatible.

Enhanced Transdermal Absorption of Hyaluronic Acid via Fusion with Pep-1 and a Hyaluronic Acid Binding Peptide

It is always big challenges for hyaluronic acid (HA) in transmembrane absorbing and efficient delivering to the skin. Pep-1, as one of the cell-penetrating peptides, has been documented to permeate various substances across cellular membranes without covalent binding. Here, a novel hyaluronic acid binding peptide (named HaBP) is designed, and then combined with Pep-1 to enhance the cell-penetrating efficiency of HA. The results of ELISA and immunofluorescence assay show that HaBP could bind with HA very well, and a combination of Pep-1 and HaBP could efficiently improve the transmembrane ability of HA. Furthermore, HA gradually enters the dermis from the surface of the skin in mice when it is administrated with both HaBP and Pep-1, while there are no obvious allergies or other adverse reactions during this process. This study finds a new method to promote the efficient transmembrane and transdermal absorption of HA, and throws some light on further research on the development of hyaluronic acid and its related cosmetics or drugs.

Molecular weight-dependent hyaluronic acid permeability and tight junction modulation in human buccal TR146 cell monolayers

The oral route is considered an attractive method for drug delivery, as it avoids the hepatic and intestinal first-pass metabolism processes. Hyaluronic acid (HA) beneficial effects to the human body include anti-aging and wound healing but its effects on oral barrier integrity and mechanical function have not yet been investigated. In this study, we analyzed oral barrier integrity and the paracellular pathway of HA transportation in TR146 cell monolayers during and after permeation and using low molecular weight HA (LMW-HA, <100 kDa) and high molecular weight HA (HMW-HA, >500 kDa). Cytotoxicity assays in TR146 cells revealed that neither LMW-HA or HMW-HA altered cell viability at concentrations <0.5 % during 24 h of treatment. HA-treated TR146 cell monolayers showed enhanced oral barrier integrity and reduced apparent permeability of fluorescein. Moreover, HA significantly increased tight junction (TJ)-related genes expression, including ZO-2, marvelD3, cingulin, claudin-1, claudin-3, and claudin-4 expression. Overall, the results of the present study indicate that HA can permeate across the oral barrier and enhance oral barrier function via the upregulated expression of TJ-related genes.

2-kDa hyaluronan ameliorates human facial wrinkles through increased dermal collagen density related to promotion of collagen remodeling

BACKGROUND/AIMS

Hyaluronan (HA) oligosaccharides are involved in several biological processes, primarily collagen remodeling and wound healing. Collagen remodeling is retarded in aging skin and causes wrinkles. The aim of this study was to evaluate the effect of 2-kDa HA oligosaccharides (HA2k) on wrinkles by permeation through the stratum corneum and promotion of collagen remodeling.

METHODS

A 3D skin model and excised human skin were used to evaluate the permeation of fluorescein-labeled HA2k. The effect of HA2k on collagen metabolism was evaluated by measuring the protein level of type 1 pro-collagen (COL1A1) and matrix metalloproteinase-1 (MMP-1) in the 3D skin model. 0.1% HA2k solution and vehicle control was applied to the human forearm for 8 weeks to evaluate dermal collagen density. To evaluate the effect of HA2k on depth of facial wrinkles, a randomized controlled trial was conducted with 0.1% HA2k lotion and vehicle lotion for 8 weeks.

RESULTS

HA2k was confirmed to permeate through the stratum corneum by fluorescent microscopy. Both COL1A1 and MMP-1 were upregulated by HA2k application in a 3D skin model culture. The collagen density was higher for the HA2k-treated forearm than for the vehicle control-treated forearm after 4 weeks. The maximum wrinkle depths in the nasolabial fold and crow's feet area were significantly shallower in the HA2k lotion group than in the control group.

CONCLUSION

HA2k permeated the stratum corneum, activated collagen synthesis and degradation simultaneously, and ameliorated wrinkles.

Effects of mucopolysaccharide polysulphate on tight junction barrier in human epidermal keratinocytes

Tight junctions (TJs) play important roles in epidermal barrier function and their dysfunction is involved in the pathogenesis of various skin diseases, including atopic dermatitis (AD). Mucopolysaccharide polysulphate (MPS) is the active ingredient of a moisturizing agent used to treat xerosis in patients with AD; however, its mechanism of action on TJ barrier function remains unclear. To elucidate the effects of MPS on TJs, adult human epidermal keratinocyte (HEKa) cells were exposed to MPS, subjected to Western blotting and quantitative PCR analyses for the investigation of TJ-related factors. MPS treatment significantly increased the mRNA and protein expression of claudin-1 (CLDN1) and zonula occludens-1, and significantly increased transepithelial electrical resistance (TEER), which indicates TJ integrity. Conversely, the sulphated and non-sulphated glycosaminoglycans, chondroitin sulphate and hyaluronic acid, respectively, had little effect on TEER or the expression of mRNAs or TJ-related proteins. Interestingly, MPS treatment also inactivated the extracellular signal-regulated kinase signalling pathway, which is known to negatively regulate CLDN1 expression. Furthermore, MPS notably improved the reduction in CLDN1 expression and TEER caused by histamine, which is upregulated in the skin of patients with AD and is known to disrupt the TJ barrier function. Taken together, these findings demonstrate that treatment with the moisturizing agent, MPS, can repair TJ dysfunction and could therefore represent a new therapeutic option for treating patients with AD.

Current Practices in Hyaluronic Acid Dermal Filler Treatment in Asia Pacific and Practical Approaches to Achieving Safe and Natural-Looking Results

Complications such as delayed inflammatory reactions (DIRs) and unnatural outcomes can sometimes arise from hyaluronic acid (HA) dermal filler treatments and can be challenging to address. Given the popularity of HA dermal fillers for aesthetic procedures, there is a need for preventive strategies to minimize these complications. Two hundred practitioners from 10 regions in Asia Pacific who administer HA fillers completed a survey on prevention of DIRs and unnatural outcomes. Thirteen global experts convened to evaluate the current practices and propose practical approaches for safe and appropriate use of HA dermal fillers. From the survey, the top three measures used to reduce the risk of DIRs included choosing an appropriate HA filler, aseptic technique, and patient selection. Key strategies employed to achieve natural-looking outcomes were treatment customization, understanding the rheological properties and behavior of different HA fillers, and being conservative in treatment approach. The panel developed a concise reference guide aimed at minimizing the risk of DIRs while achieving natural aesthetic outcomes. Five practical considerations were recommended: patient assessment and individualization of treatment plan, choice of an appropriate HA filler, adequate knowledge of facial anatomy, strict adherence to aseptic methods, and proper injection technique. The panel highlighted the need for education efforts to increase awareness of differential immunogenicity between HA fillers and to improve understanding on the importance of preserving aesthetic individuality for optimal results. These practical insights from the global experts support practitioners in optimizing safety and quality of aesthetic treatment with HA fillers.

Hyaluronic acid detection and relative quantification by mass spectrometry imaging in human skin tissues

Hyaluronic acid (HA) is a major component of the skin, contributing to tissue hydration and biomechanical properties. As HA content in the skin decreases with age, formulas containing HA are widely used in cosmetics and HA injections in aesthetic procedures to reduce the signs of aging. To prove the beneficial effects of these treatments, efficient quantification of HA levels in the skin is necessary, but remains difficult. A new analytical method has been developed based on matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) to quantify HA content in cross sections of human skin explants. A standardized and reproducible chemical entity (3 dimeric motifs or 6-mer) quantifiable by MALDI-MSI was produced by enzymatic hydrolysis using a specific hyaluronidase (H1136) in HA solution. This enzymatic digestion was carried out on skin sections before laser desorption, enabling the detection of HA. Histological coloration allowed us to localize the epidermis and the dermis on skin sections and, by comparison with the MALDI molecular image, to calculate the relative HA concentrations in these tissue areas. Skin explants were treated topically using a formula containing HA or its placebo, and the HA distribution profiles were compared with those obtained from untreated explants. A significant increase in HA was shown in each skin layer following topical application of the formula containing HA versus placebo and untreated samples (average of 126±40% and 92±40%, respectively). The MALDI-MSI technique enabled the quantification and localization of all HA macromolecules (endogenous and exogenous) on skin sections and could be useful for determining the efficacy of new cosmetic products designed to fight the signs of aging.

Delayed adverse reaction to a natural dermal filler mimicking salivary gland neoplasia

BACKGROUND

Cosmetic dermal fillers are a sought-after procedure globally. However, despite the safety claims of filler materials by the manufacturers, adverse reactions still occur.

CASE PRESENTATION

This case report is of a 66-year-old female who presented with a late-onset complication of a hyaluronic acid dermal filler that clinically mimicked a salivary gland neoplasm. The patient presented with firm peri-oral swellings of short duration that clinically mimicked a pleomorphic adenoma and mucoepidermoid carcinoma. The diagnosis was that of a foreign-body granulomatous response to dermal fillers. Although other mimics of a similar nature are reported a knowledgeable clinician, careful choice of filler material, knowledge of the product, thorough pre-procedural history taking and post-procedural patient follow-up can drastically minimize a possible misdiagnosis. The reaction was treated with a combination of hyaluronidase, betamethasone and 5-flurouracil intra-lesional injections monthly for 11 consecutive months, with total clinical resolution.

CONCLUSIONS

Patient education of the procedure, product name and the possibility of an adverse reaction occurring, even years later or at a site distant to the initial site of placement, is vital. Further, we review the recent reported adverse association of the new mRNA COVID-19 vaccines and dermal filler placement.

New Functions of Low-Molecular-Weight Hyaluronic Acid on Epidermis Filaggrin Production and Degradation

Hyaluronic acid (HA) is a high-molecular-weight polysaccharide with high moisturizing power. It is composed of repeating disaccharides of N-acetyl-D-glucosamine and D-glucuronic acid. Low-molecular-weight hyaluronan (LMHA) is obtained by changing the molecular weight or modifying the functional groups of HA and is commonly used together with HA in cosmetics. The objective of this study was to determine whether LMHA promotes the synthesis of filaggrin (FLG). We also investigated whether LMHA activates FLG-degrading enzymes. Three-dimensional (3D) models of the human epidermis were cultured with LMHA. Real-time PCR was used to quantify the mRNA levels of profilaggrin (proFLG), involucrin (IVL), and FLG-degrading enzymes. FLG protein levels were measured by fluorescent antibody staining and Western blotting. The mRNA was quantified using a 3D epidermis model, and it was observed that the mRNA levels of proFLG, IVL, caspase-14 (CASP14), and bleomycin hydrolase were increased by the application of LMHA. Immunofluorescence results showed an increase in FLG proteins, and results from experiments using 3D epidermis models showed that LMHA increased the activity of CASP14. This suggests that the topical application of LMHA would result in an increase in natural moisturizing factor and promote moisturization of the stratum corneum.

Epidermal Hyaluronan in Barrier Alteration-Related Disease

In skin, although the extracellular matrix (ECM) is highly developed in dermis and hypodermis, discrete intercellular spaces between cells of the living epidermal layers are also filled with ECM components. Herein, we review knowledge about structure, localization and role of epidermal hyaluronan (HA), a key ECM molecule. HA is a non-sulfated glycosaminoglycan non-covalently bound to proteins or lipids. Components of the basal lamina maintain some segregation between the epidermis and the underlying dermis, and all epidermal HA is locally synthesized and degraded. Functions of HA in keratinocyte proliferation and differentiation are still controversial. However, through interactions with partners, such as the TSG-6 protein, HA is involved in the formation, organization and stabilization of the epidermal ECM. In addition, epidermal HA is involved in the formation of an efficient epidermal barrier made of cornified keratinocytes. In atopic dermatitis (AD) with profuse alterations of the epidermal barrier, HA is produced in larger amounts by keratinocytes than in normal skin. Epidermal HA inside AD lesional skin is located in enlarged intercellular spaces, likely as the result of disease-related modifications of HA metabolism.

Stringiness of hyaluronic acid emulsions

Objective

Cosmetic emulsions containing hyaluronic acid are ubiquitous in the cosmetic industry. However, the addition of (different molecular weight) hyaluronic acid can affect the filament stretching properties of concentrated emulsions. This property is often related to the “stringiness” of an emulsion, which can affect the consumer's choice for a product. It is thus very important to investigate and predict the effect of hyaluronic acid on the filament stretching properties of cosmetic emulsions.

Methods

Model emulsions and emulsions with low and high molecular weights are prepared and their filament stretching properties are studied by the use of an extensional rheometer. Two different stretching speeds are employed during the stretching of the emulsions, a low speed at 10 µm/s and a high speed at 10 mm/s. The shear rheology of the samples is measured by rotational rheology.

Results

We find that filament formation only occurs at high stretching speeds when the emulsion contains high molecular weight hyaluronic acid. The formation of this filament, which happens at intermediate states of the break‐up, coincides with an exponential decay in the break‐up dynamics. The beginning and end of the break‐up of high molecular weight hyaluronic acid emulsions show a power law behaviour, where the exponent depends on the initial stretching rate. At a lower stretching speed, no filament is observed for both high molecular weight and low molecular weight hyaluronic acid emulsions and the model emulsion. The emulsions show a power law behaviour over the whole break‐up range, where the exponent also depends on the stretching rate. No significant difference is observed between the shear flow properties of the emulsions containing different molecular weights hyaluronic acid.

Conclusion

In this work, we underline the importance of the molecular weight of hyaluronic acid on the elongational properties of concentrated emulsions. The filament formation properties, for example the stringiness, of an emulsion is a key determinant of a product liking and repeat purchase. Here, we find that high molecular weight hyaluronic acid and a high stretching speed are the control parameters affecting the filament formation of an emulsion.

Hyaluronic acid (HA) stimulates the in vitro expression of CD44 proteins but not HAS1 proteins in normal human epidermal keratinocytes (NHEKs) and is HA molecular weight dependent

BACKGROUND

In the skin, hyaluronic acid is broken down to smaller fragments by hyaluronidase enzymes, particularly when skin is wounded. The impact of various molecular weight fragments of HA on normal human epidermal keratinocytes (NHEK) with regard to expression of important cellular proteins has not been deeply explored.

AIMS

Examination of three molecular weight (Mw) fractions of hyaluronic acid: 1) average Mw of the high fraction: 1.5-2 MDa, 2) average Mw of the medium fraction: 200-500 kDa, and 3) average Mw of the low fraction: 5-10 kDa and a unique 1:1:1 composite complex of the three HA fragments (Triluronic^® Acid) was done to examine the influence of the HA on two critical skin cell protein targets: hyaluronan synthase-1 (HAS-1) and the HA binding protein cluster of differentiation 44 (CD44).

METHODS

NHEKs were treated in vitro with a 1.0% stock solution of each HA Mw fraction at 1.0, 0.5, and 0.1% concentrations of the 1.0% solution and the polysaccharide composite at the same concentrations for 48 Hrs. The cells were than analyzed by ELISA protein assays for HAS-1 and CD44 protein content.

RESULTS

Examination of HAS-1 protein expression indicates that none of the HA test materials influenced the expression of HAS-1 at any concentration. Examination of the CD44 protein expression indicated that the low Mw fraction and the commercial complex of the three Mw fractions upregulated CD44 protein expression in NHEKs, but the medium Mw and high Mw HA fractions did not.

CONCLUSIONS

In this work, it was demonstrated that HA can influence the expression of CD44 protein, a critical HA transmembrane HA binding protein, and the influence appears to be molecular weight dependent.

Hyaluronic Acid-Mediated Drug Delivery System Targeting for Inflammatory Skin Diseases: A Mini Review

Hyaluronic acid (HA), a major component of extracellular matrix has been widely applied in pharmaceutical and cosmetic industries due to its reported pharmacological properties. Various types of HA drug delivery system including nanoparticles, cryogel-based formulations, microneedle patches, and nano-emulsions were developed. There are studies reporting that several HA-based transdermal delivery systems exhibit excellent biocompatibility, enhanced permeability and efficient localized release of anti-psoriasis drugs and have shown to inhibit psoriasis-associated skin inflammation. Similarly HA is found in abundant at epidermis of atopic dermatitis (AD) suggesting its role in atopic AD pathology. Anti-allergenic effect of atopic eczema can be achieved through the inhibition of CD44 and protein kinase C alpha (PKCα) interaction by HA. Herein, we aim to evaluate the current innovation on HA drug delivery system and the other potential applications of HA in inflammatory skin diseases, focusing on atopic dermatitis and psoriasis. HA is typically integrated into different delivery systems including nanoparticles, liposomes, ethosomes and microneedle patches in supporting drug penetration through the stratum corneum layer of the skin. For instance, ethosomes and microneedle delivery system such as curcumin-loaded HA-modified ethosomes were developed to enhance skin retention and delivery of curcumin to CD44-expressing psoriatic cells whereas methotrexate-loaded HA-based microneedle was shown to enhance skin penetration of methotrexate to alleviate psoriasis-like skin inflammation. HA-based nanoparticles and pluronic F-127 based dual responsive (pH/temperature) hydrogels had been described to enhance drug permeation through and into the intact skin for AD treatment.

Delayed Inflammatory Reactions to Hyaluronic Acid Fillers: A Literature Review and Proposed Treatment Algorithm

Background and Objectives

There is a wide diversity of opinions regarding the management of delayed inflammatory reactions (DIRs) secondary to hyaluronic acid (HA)-based fillers. The plethora of approaches has led the authors to conduct a review regarding management and treatment of DIRs as well as establish therapeutic guidelines for this purpose.

Materials and Methods

A review of the literature was performed through databases such as PubMed using keywords including HA-fillers and complications, delayed HA filler sequelae and therapy, soft tissue and dermal filler reactions and management. Additionally, a survey comprised of questions regarding the management and treatment of DIRs was sent to 18 physicians highly experienced with soft-tissue filler injections in 10 countries. Their answers and recommendations were analyzed and debated amongst these panelists.

Results

Sixteen panelists favored antibiotic therapy as first-line treatment for DIRs, specifically dual antibiotic therapy consisting of a fluoroquinolone along with a tetracycline or macrolide for a period of 3-6 weeks. The majority refrained from the use of intralesional (IL) or systemic steroids except in the case of disfiguring or recalcitrant reactions. IL hyaluronidase was recommended by 13 panelists; however, some preferred a watchful waiting approach for a period of 48 hours to 2 weeks prior to IL hyaluronidase, and in cases where antibiotics did not lead to improvement.

Conclusion

A consensus was reached and summarized to propose a clear, easy-to-follow, stepwise algorithm for the treatment of DIRs.

Hyaluronan metabolism enhanced during epidermal differentiation is suppressed by vitamin C

BACKGROUND

Hyaluronan is a large, linear glycosaminoglycan present throughout the narrow extracellular space of the vital epidermis. Increased hyaluronan metabolism takes place in epidermal hypertrophy, wound healing and cancer. Hyaluronan is produced by hyaluronan synthases and catabolized by hyaluronidases, reactive oxygen species and KIAA1199.

OBJECTIVES

To investigate the changes in hyaluronan metabolism during epidermal stratification and maturation, and the impact of vitamin C on these events.

METHODS

Hyaluronan synthesis and expression of the hyaluronan-related genes were analysed during epidermal maturation from a simple epithelium to a fully differentiated epidermis in organotypic cultures of rat epidermal keratinocytes using quantitative reverse transcriptase polymerase chain reaction, immunostaining and Western blotting, in the presence and absence of vitamin C.

RESULTS

With epidermal stratification, both the production and the degradation of hyaluronan were enhanced, resulting in an increase of hyaluronan fragments of various sizes. While the mRNA levels of Has3 and KIAA1199 remained stable during the maturation, Has1, Has2 and Hyal2 showed a transient upregulation during stratification, Hyal1 transcription remained permanently increased and transcription of the hyaluronan receptor, Cd44, decreased. At maturation, vitamin C downregulated Has2, Hyal2 and Cd44, whereas it increased high-molecular-mass hyaluronan in the epidermis, and reduced small fragments in the medium, suggesting stabilization of epidermal hyaluronan.

CONCLUSIONS

Epidermal stratification and maturation is associated with enhanced hyaluronan turnover, and release of large amounts of hyaluronan fragments. The high turnover is suppressed by vitamin C, which is suggested to enhance normal epidermal differentiation in part through its effect on hyaluronan.

Hyaluronan Rich Microenvironment in the Limbal Stem Cell Niche Regulates Limbal Stem Cell Differentiation

Purpose

Limbal epithelial stem cells (LSCs), located in the basal layer of the corneal epithelium in the corneal limbus, are vital for maintaining the corneal epithelium. LSCs have a high capacity of self-renewal with increased potential for error-free proliferation and poor differentiation. To date, limited research has focused on unveiling the composition of the limbal stem cell niche, and, more important, on the role the specific stem cell niche may have in LSC differentiation and function. Our work investigates the composition of the extracellular matrix in the LSC niche and how it regulates LSC differentiation and function.

Methods

Hyaluronan (HA) is naturally synthesized by hyaluronan synthases (HASs), and vertebrates have the following three types: HAS1, HAS2, and HAS3. Wild-type and HAS and TSG-6 knockout mice-HAS1-/-;HAS3-/-, HAS2Δ/ΔCorEpi, TSG-6-/--were used to determine the importance of the HA niche in LSC differentiation and specification.

Results

Our data demonstrate that the LSC niche is composed of a HA rich extracellular matrix. HAS1-/-;HAS3-/-, HAS2Δ/ΔCorEpi, and TSG-6-/- mice have delayed wound healing and increased inflammation after injury. Interestingly, upon insult the HAS knock-out mice up-regulate HA throughout the cornea through a compensatory mechanism, and in turn this alters LSC and epithelial cell specification.

Conclusions

The LSC niche is composed of a specialized HA matrix that differs from that present in the rest of the corneal epithelium, and the disruption of this specific HA matrix within the LSC niche leads to compromised corneal epithelial regeneration. Finally, our findings suggest that HA has a major role in maintaining the LSC phenotype.

Noninvasive penetration of 5 nm hyaluronic acid molecules across the epidermal barrier (in vitro) and its interaction with human skin cells

OBJECTIVE

Hyaluronic acid represents one of the major components of the extracellular environment. The main challenge remains in the ability to deliver these molecules noninvasively across the skin barrier, which can be overcome by the reduction in size to an extent that allows these molecules to pass across the skin barrier. The aim of this study was to measure the penetration and bioavailability of low molecular weight hyaluronic acid to cross an epidermal barrier model.

METHODS

Determining the quantity of hyaluronic acid in the test solutions was carried with method of photocolorimetry analysis. Investigation of the interaction of cells with LMWHA was studied with a confocal microscope.

RESULTS

The study showed that LMWHA is able to cross the epidermis. Most effective penetration level is during the first 6 hours reaching 75%, and then the concentration started to decline and reached the equilibrium state within the following 2 hours. Confocal laser microscopy demonstrated different distribution and behavior of these molecules among the keratinocytes and fibroblasts.

CONCLUSION

Reducing the size of hyaluronic acid to 5 nm enhance their transport across the epidermal layer. The concentration of hyaluronic acid molecules was higher on the fibroblast surface in comparison to their extracellular environment.

A biocompatible macromolecular two-photon initiator based on hyaluronan

The possibility of the direct encapsulation of living cells via two-photon induced photopolymerization enables the microfabrication of hydrogel scaffolds with high initial cell loadings and intimate matrix-cell contact. While highly efficient water-soluble two-photon initiators based on benzylidene ketone dyes have been developed, they exhibit considerable cyto- and phototoxicity. To address the problem of photoinitiator migration from the extracellular matrix into the cytosol, a two-photon initiator bound to a polymeric hyaluronan backbone (HAPI) was synthesized in this work. HAPI exhibited a distinct improvement of cytocompatibility compared to a reference two-photon initiator. Basic photophysical investigations were performed to characterize the absorption and fluorescence behavior of HAPI. Laser scanning microscopy was used to visualize and confirm the hindered transmembrane migration behavior of HAPI. The performance of HAPI was tested in two-photon polymerization at exceedingly high printing speeds of 100 mm s-1 producing gelatin-based complex 3D hydrogel scaffolds with a water content of 85%. The photodamage of the structuring process was low and viable MC3T3 cells embedded in the gel were monitored for several days after structuring.

Hyaluronan Hybrid Cooperative Complexes as a Novel Frontier for Cellular Bioprocesses Re-Activation

Hyaluronic Acid (HA)-based dermal formulations have rapidly gained a large consensus in aesthetic medicine and dermatology. HA, highly expressed in the Extracellular Matrix (ECM), acts as an activator of biological cascades, stimulating cell migration and proliferation, and operating as a regulator of the skin immune surveillance, through specific interactions with its receptors. HA may be used in topical formulations, as dermal inducer, for wound healing. Moreover, intradermal HA formulations (injectable HA) provide an attractive tool to counteract skin aging (e.g., facial wrinkles, dryness, and loss of elasticity) and restore normal dermal functions, through simple and minimally invasive procedures. Biological activity of a commercially available hyaluronic acid, Profhilo®, based on NAHYCO™ technology, was compared to H-HA or L-HA alone. The formation of hybrid cooperative complexes was confirmed by the sudden drop in η0 values in the rheological measurements. Besides, hybrid cooperative complexes proved stable to hyaluronidase (BTH) digestion. Using in vitro assays, based on keratinocytes, fibroblasts cells and on the Phenion® Full Thickness Skin Model 3D, hybrid cooperative complexes were compared to H-HA, widely used in biorevitalization procedures, and to L-HA, recently proposed as the most active fraction modulating the inflammatory response. Quantitative real-time PCR analyses were accomplished for the transcript quantification of collagens and elastin. Finally immunofluorescence staining permitted to evaluate the complete biosynthesis of all the molecules investigated. An increase in the expression levels of type I and type III collagen in fibroblasts and type IV and VII collagen in keratinocytes were found with the hybrid cooperative complexes, compared to untreated cells (CTR) and to the H-HA and L-HA treatments. The increase in elastin expression found in both cellular model and in the Phenion® Full Thickness Skin Model 3D also at longer time (up to 7 days), supports the clinically observed improvement of skin elasticity. The biomarkers analyzed suggest an increase of tissue remodeling in the presence of Profhilo®, probably due to the long lasting release and the concurrent action of the two HA components.

Is molecular size a discriminating factor in hyaluronan interaction with human cells?

Nowadays there is a great interest in investigating the effect of particular hyaluronan fragments in the biomedical field and in cosmeceutical applications. Literature has reported that very low molecular weight HA (Mw<5kDa) has an inflammatory effect, whilst HA ranging from 15 to 250 has shown controversial effects. This work aims to give better elucidation on the correlation between the different sized HA fragments and their biological functions. In this respect, a simple and effective degradation strategy is used to obtain several HA fragments. Also, an hydrodynamic and structural characterization was performed in order to obtain samples suitable to evaluate cellular response. In particular an in vitro scratch test in time lapse experiments was used to study the effect of HA fragments, ranging from 1800 to 6kDa on wound dermal reparation based on human keratinocytes. All high and low Mw HA used in this study allowed for faster wound closure compared to the un-treated cells, except for 6kDa that, on the contrary, prevented repair. In addition, TGF-β 1, TNFα and IL-6, representative biomarkers of the inflammation phase occurring in wound healing process, were quantified by RT-PCR. A general up-regulation trend of these biomarkers was found with the HA molecular weight reduction. LHA6kDa was the only treatment that induced a major inflammatory response (over 30 fold increase respect to control) confirming the recent literature outcomes. IL-6 protein level evaluated through ELISA assay corroborated the previous results. Furthermore, activation of key HA receptors, such as CD44, RHAMM, TLR4, with respect to hyaluronan size, was evaluated, at transcriptional level showing selective recognition by HA 1800, 1400, 500 for CD44, whilst the lower Mw fragments activated TLR-4 moderately at 50 and 15kDa. An increase to "alarm" level was found for 6kDa fragments. Immunofluorescence staining confirmed this data. The present research work demonstrated that the diverse pharma grade hyaluronan fragments could modulate cellular processes differently. From 1800kDa down to 50kDa, CD44 was the recognized receptor and pro-inflammatory biomarkers were only slightly up-regulated during wound healing in the presence of HA. Finally our outcomes showed that the lower the fragment size the higher the concern for inflammatory cytokines up-regulation; repair process impairment was highlighted only for 6kDa chains.

Interactions of hyaluronic Acid with the skin and implications for the dermal delivery of biomacromolecules

Hyaluronic acid (HA) hydrogels are interesting delivery systems for topical applications. Besides moisturizing the skin and improving wound healing, HA facilitates topical drug absorption and is highly compatible with labile biomacromolecules. Hence, in this study we investigated the influence of HA hydrogels with different molecular weights (5 kDa, 100 kDa, 1 MDa) on the skin absorption of the model protein bovine serum albumin (BSA) using fluorescence lifetime imaging microscopy (FLIM). To elucidate the interactions of HA with the stratum corneum and the skin absorption of HA itself, we combined FLIM and Fourier-transform infrared (FTIR) spectroscopy. Our results revealed distinct formulation and skin-dependent effects. In barrier deficient (tape-stripped) skin, BSA alone penetrated into dermal layers. When BSA and HA were applied together, however, penetration was restricted to the epidermis. In normal skin, penetration enhancement of BSA into the epidermis was observed when applying low molecular weight HA (5 kDa). Fluorescence resonance energy transfer analysis indicated close interactions between HA and BSA under these conditions. FTIR spectroscopic analysis of HA interactions with stratum corneum constituents showed an α-helix to β-sheet interconversion of keratin in the stratum corneum, increased skin hydration, and intense interactions between 100 kDa HA and the skin lipids resulting in a more disordered arrangement of the latter. In conclusion, HA hydrogels restricted the delivery of biomacromolecules to the stratum corneum and viable epidermis in barrier deficient skin, and therefore seem to be potential topical drug vehicles. In contrast, HA acted as an enhancer for delivery in normal skin, probably mediated by a combination of cotransport, increased skin hydration, and modifications of the stratum corneum properties.

Human skin penetration of hyaluronic acid of different molecular weights as probed by Raman spectroscopy

BACKGROUND

Topical delivery of molecules into the human skin is one of the main issues in dermatology and cosmetology. Several techniques were developed to study molecules penetration into the human skin. Although widely accepted, the conventional methods such as Franz diffusion cells are unable to provide the accurate localization of actives in the skin layers. A different approach based on Raman spectroscopy has been proposed to follow-up the permeation of actives. It presents a high molecular specificity to distinguish exogenous molecules from skin constituents.

METHODS

Raman micro-imaging was applied to monitor the skin penetration of hyaluronic acids (HA) of different molecular weights. The first step, was the spectral characterization of these HA. After, we have determined spectral features of HA by which they can be detected in the skin. In the second part, transverse skin sections were realized and spectral images were recorded.

RESULTS

Our results show a difference of skin permeation of the three HA. Indeed, HA with low molecular weight (20-300 kDa) passes through the stratum corneum in contrast of the impermeability of high molecular weight HA (1000-1400 kDa).

CONCLUSION

Raman spectroscopy represents an analytical, non-destructive, and dynamic method to evaluate the permeation of actives in the skin layers.

Hyaluronan-phosphatidylethanolamine polymers form pericellular coats on keratinocytes and promote basal keratinocyte proliferation

Aged keratinocytes have diminished proliferative capacity and hyaluronan (HA) cell coats, which are losses that contribute to atrophic skin characterized by reduced barrier and repair functions. We formulated HA-phospholipid (phosphatidylethanolamine, HA-PE) polymers that form pericellular coats around cultured dermal fibroblasts independently of CD44 or RHAMM display. We investigated the ability of these HA-PE polymers to penetrate into aged mouse skin and restore epidermal function in vivo. Topically applied Alexa(647)-HA-PE penetrated into the epidermis and dermis, where it associated with both keratinocytes and fibroblasts. In contrast, Alexa(647)-HA was largely retained in the outer cornified layer of the epidermis and quantification of fluorescence confirmed that significantly more Alexa(647)-HA-PE penetrated into and was retained within the epidermis than Alexa(647)-HA. Multiple topical applications of HA-PE to shaved mouse skin significantly stimulated basal keratinocyte proliferation and epidermal thickness compared to HA or vehicle cream alone. HA-PE had no detectable effect on keratinocyte differentiation and did not promote local or systemic inflammation. These effects of HA-PE polymers are similar to those reported for endogenous epidermal HA in youthful skin and show that topical application of HA-PE polymers can restore some of the impaired functions of aged epidermis.

Active ingredients against human epidermal aging

The decisive role of the epidermis in maintaining body homeostasis prompted studies to evaluate the changes in epidermal structure and functionality over the lifetime. This development, along with the identification of molecular mechanisms of epidermal signaling, maintenance, and differentiation, points to a need for new therapeutic alternatives to treat and prevent skin aging. In addition to recovering age- and sun-compromised functions, proper treatment of the epidermis has important esthetic implications. This study reviews active ingredients capable of counteracting symptoms of epidermal aging, organized according to the regulation of specific age-affected epidermal functions: (1) several compounds, other than retinoids and derivatives, act on the proliferation and differentiation of keratinocytes, supporting the protective barrier against mechanical and chemical insults; (2) natural lipidic compounds, as well as glycerol and urea, are described as agents for maintaining water-ion balance; (3) regulation of immunological pathogen defense can be reinforced by natural extracts and compounds, such as resveratrol; and (4) antioxidant exogenous sources enriched with flavonoids and vitamin C, for example, improve solar radiation protection and epidermal antioxidant activity. The main objective is to provide a functional classification of active ingredients as regulatory elements of epidermal homeostasis, with potential cosmetic and/or dermatological applications.

Hyaluronan metabolism in human keratinocytes and atopic dermatitis skin is driven by a balance of hyaluronan synthases 1 and 3

Hyaluronan (HA) is a glycosaminoglycan synthesized directly into the extracellular matrix by three hyaluronan synthases (HAS1, HAS2, and HAS3). HA is abundantly synthesized by keratinocytes but its epidermal functions remain unclear. We used culture models to grow human keratinocytes as autocrine monolayers or as reconstructed human epidermis (RHE) to assess HA synthesis and HAS expression levels during the course of keratinocyte differentiation. In both the models, epidermal differentiation downregulates HAS3 mRNA expression while increasing HAS1 without significant changes in hyaluronidase expression. HA production correlates with HAS1 mRNA expression level during normal differentiation. To investigate the regulation of HAS gene expression during inflammatory conditions linked to perturbed differentiation, lesional and non-lesional skin biopsies of atopic dermatitis (AD) patients were analyzed. HAS3 mRNA expression level increases in AD lesions compared with healthy and non-lesional skin. Simultaneously, HAS1 expression decreases. Heparin-binding EGF-like growth factor (HB-EGF) is upregulated in AD epidermis. An AD-like HAS expression pattern is observed in RHE incubated with HB-EGF. These results indicate that HAS1 is the main enzyme responsible for HA production by normal keratinocytes and thus, must be considered as an actor of normal keratinocyte differentiation. In contrast, HAS3 can be induced by HB-EGF and seems mainly involved in AD epidermis.

Barriers and more: functions of tight junction proteins in the skin

Although the existence of tight junction (TJ) structures (or a secondary epidermal barrier) was postulated for a long time, the first description of TJ proteins in the epidermis (occludin, ZO-1, and ZO-2) was only fairly recent. Since then, a wealth of new insights concerning TJs and TJ proteins, including their functional role in the skin, have been gathered. Of special interest is that the epidermis as a multilayered epithelium exhibits a very complex localization pattern of TJ proteins, which results in different compositions of TJ protein complexes in different layers. In this review, we summarize our current knowledge about the role of TJ proteins in the epidermis in barrier function, cell polarity, vesicle trafficking, differentiation, and proliferation. We hypothesize that TJ proteins fulfill TJ structure-dependent and structure-independent functions and that the specific function of a TJ protein may depend on the epidermal layer where it is expressed.