Skin extracellular matrix stimulation following injection of a hyaluronic acid-based dermal filler in a rat model

Elastogenesis in Focus: Navigating Elastic Fibers Synthesis for Advanced Dermal Biomaterial Formulation

Elastin, a fibrous extracellular matrix (ECM) protein, is the main component of elastic fibers that are involved in tissues' elasticity and resilience, enabling them to undergo reversible extensibility and to endure repetitive mechanical stress. After wounding, it is challenging to regenerate elastic fibers and biomaterials developed thus far have struggled to induce its biosynthesis. This review provides a comprehensive summary of elastic fibers synthesis at the cellular level and its implications for biomaterial formulation, with a particular focus on dermal substitutes. The review delves into the intricate process of elastogenesis by cells and investigates potential triggers for elastogenesis encompassing elastin-related compounds, ECM components, and other molecules for their potential role in inducing elastin formation. Understanding of the elastogenic processes is essential for developing biomaterials that trigger not only the synthesis of the elastin protein, but also the formation of a functional and branched elastic fiber network.

Decellularized Extracellular Matrix Scaffolds for Soft Tissue Augmentation: From Host-Scaffold Interactions to Bottlenecks in Clinical Translation

Along with a paradigm shift in looking at soft tissue fillers from space-filling to bioactive materials, decellularized extracellular matrix (DEM) fillers have gained more attention considering their superior bioactivity. However, the complex mechanisms that govern the interaction between host tissues and DEMs have been partially understood. This review first covers the mechanisms that determine immunogenicity, angiogenesis and vasculogenesis, and recellularization and remodeling after DEM implantation into host tissue, with a particular focus on related findings from filler materials. Accordingly, the review delves into the dual role of macrophages and their M1/M2 polarization paradigm to form both constructive and destructive immune responses to DEM implants. Moreover, the contribution of macrophages in angiogenesis has been elucidated, which includes but is not limited to the secretion of angiogenic growth factors and extracellular matrix (ECM) remodeling. The findings challenge the traditional view of immune cells as solely destructive entities in biomaterials and indicate their multifaceted roles in tissue regeneration. Furthermore, the review discusses how the compositional factors of DEMs, such as the presence of growth factors and matrikines, can influence angiogenesis, cell fate, and differentiation during the recellularization process. It is also shown that the biomechanical properties of DEMs, including tissue stiffness, modulate cell responses through mechanotransduction pathways, and the structural properties of DEMs, such as scaffold porosity, impact cell-cell and cell-ECM interactions. Finally, we pointed out the current clinical applications, the bottlenecks in the clinical translation of DEM biomaterials into soft tissue fillers, as well as the naïve research areas of the field.

Characterization and Comparative Investigation of Hydroxyapatite/Carboxymethyl Cellulose (CaHA/CMC) Matrix for Soft Tissue Augmentation in a Rat Model

This study endeavors to develop an injectable subdermal implant material tailored for soft tissue repair and enhancement. The material consists of a ceramic phase of calcium hydroxyapatite (CaHA), which is biocompatible, 20-60 μm in size, known for its biocompatibility and minimal likelihood of causing foreign body reactions, antigenicity, and minimal inflammatory response, dispersed in a carrier phase composed of carboxymethyl cellulose (CMC), glycerol, and water for injection. The gel formulation underwent comprehensive characterization via various analytical techniques. X-ray diffraction (XRD) was employed to identify crystalline phases and investigate the structural properties of ceramic particles, while thermogravimetric analysis (TGA) was conducted to evaluate the thermal stability and decomposition behavior of the final formulation. Scanning electron microscopy (SEM) was utilized to examine the surface morphology and particle size distribution, confirming the homogeneous dispersion of spherical CaHA particles within the matrix. SEM analysis revealed particle sizes ranging from approximately 20-60 μm. Elemental analysis confirmed a stoichiometric Ca/P ratio of 1.65 in the hydroxyapatite (HA) structure. Heavy metal content exhibited suitability for surgical implant use without posing toxicity risks. Rheological analysis revealed a storage modulus of 58.6 and 68.9 kPa and a loss modulus of 21.7 and 24.8 kPa at the frequencies of 2 and 5 Hz, respectively. 150 μL of sterilized CaHA/CMC was injected subcutaneously into rats and compared with a similar product, Crystalys, to assess its effects on soft tissues. Skin tissue samples of rats were collected at specific intervals throughout the study (30, 45, 60, 90 and 120 days), and examined histologically. Results demonstrated that CaHA/CMC gel led to a significant increase in dermal thickness, elastic fibers, and collagen density. Based on the findings, the formulated CaHA/CMC gel was found to be biocompatible, biodegradable, nonimmunogenic, nontoxic, safe, and effective, and represents a promising option for soft tissue repair and augmentation.

Histologic Evaluation of Early Papilla Healing after Augmentation with Injectable Hyaluronic Acid-A Proof of Concept

Objectives: This human histological study's purpose was to histologically evaluate papillae's healing after hyaluronic acid (HA) gel augmentation at three healing time points after one injection with hyaDENT BG®. Methods: Fifteen papillae from two patients with stage III, grade B periodontitis have been selected for this study. Every week for three weeks, five papillae were injected once with HA gel, and during the fourth week, the papillae were surgically removed as part of step 3 of the periodontal treatment. The histological analysis was performed on fifteen papillae, with five papillae corresponding to every timepoint of healing (weeks 1, 2, and 3). The primary outcome was considered to be the newly formed collagen fibers. The presence of residual HA, the integrity of epithelium or the presence of erosions/ulcerations, the presence and characteristics of inflammatory infiltrate, the presence of granulomatous reactions, and interstitial edema were considered to be secondary outcomes. Results: From the first to the third week, newly formed connective tissue begins to appear, while the observed HA pools (vesicles) content decreases. The density of inflammatory infiltrate was higher in the first week after injection, decreasing considerably by week 3; however, it was still visible throughout the healing time points. A granulomatous reaction was present in only three samples, while no signs of ulceration or necrosis could be observed; however, epithelial erosions could be observed on some samples after the first week. Conclusions: Papila augmentation with hyaluronic acid promotes new collagen formation from the second week of healing despite some foreign body granulomatous reactions.

Bottlenose dolphin (Tursiops truncatus) immortalized fibroblasts on novel 3D in vitro collagen-free scaffolds

Dolphins, as apex predators, can be considered relevant sentinels of the health of marine ecosystems. The creation of 3D cell models to assess in vitro cell-to-cell and cell-to-matrix interactions in environmental-mimicking conditions, is of considerable interest. However, to date the establishment of cetacean 3D culture systems has not yet been accomplished. Thus, in this study, different 3D systems of bottlenose dolphin (Tursiops truncatus) skin fibroblasts have been analyzed. Particularly, novel scaffolds based on hyaluronic acid and ionic-complementary self-assembling peptides such as RGD-EAbuK and EAbuK-IKVAV have been compared to Matrigel. Histological and fluorescent staining, electron microscopy (TEM) analyses and viability assays have been performed and RT-PCR has been used to detect extracellular matrix (ECM) components produced by cells. Results showed that Matrigel induced cells to form aggregates with lower viability and no ECM production compared to the novel scaffolds. Moreover, scaffolds allowed dispersed cells to produce a collagenous ECM containing collagen1a1, laminin B1 and elastin. The HA-EAbuK-IKVAV scaffold resulted in the most suitable 3D model in terms of cell quantity and viability. The development of this innovative approach is the first step towards the possibility to create 3D in vitro models for this protected species.

Tunnel technique and subepithelial connective tissue graft, with or without cross-linked hyaluronic acid, in the treatment of multiple gingival recessions: 12-month outcomes of a randomized clinical trial

BACKGROUND

This study evaluated the influence of the adjunctive application of a cross-linked hyaluronic acid (HA) in the treatment of multiple gingival recessions, using a modified coronally advanced tunnel (MCAT) technique and subepithelial connective tissue graft (SCTG) (MCAT+SCTG±HA).

METHODS

A randomized, split-mouth, double-masked comparison of the effects of MCAT+HA+SCTG (test) versus MCAT+SCTG (control) in the treatment of multiple, contralateral gingival recessions with clinical, esthetic, and histological evaluations was carried out. All samples were stained with hematoxylin and eosin, Masson's trichrome, Verhoeff-Van Gieson, and Alcian blue stain for semiquantitative evaluation. The primary outcome variable was 12-month mean root coverage (MRC).

RESULTS

Twenty-four patients with 266 gingival recessions received both control and test treatments (133 recessions per group). 12-month MRC of the MCAT+HA+SCTG group was not significantly different from the MCAT+SCTG group with 84.32%±  34.46% and 85.71%±  36.43%, respectively (p = 0.991). Both treatment modes produced favorable esthetic outcomes (root coverage esthetic score [RES] 9.51±  1.01 tests vs. 9.26±  1.10 controls, p = 0.7292). However, the application of HA improved soft tissue texture (p = 0.0091). The remaining end point measures did not differ significantly between groups. Histological evaluation showed a significantly greater number of elastic fibers and a moderate increase in collagen fiber density in biopsy samples taken from the test sides when compared to the control sides (p = 0.0419 and p = 0.300, respectively).

CONCLUSIONS

MCAT+SCTG is an effective procedure in the treatment of multiple recession Type 1 (RT1) and RT2 recessions. There were no statistically significant differences in evaluated clinical treatment outcomes in the MCAT+HA+SCTG group compared to the MCAT+SCTG group within a period of 12 months. The application of HA increased collagen and elastic fiber density.

Aesthetic Rehabilitation Medicine: Enhancing Wellbeing beyond Functional Recovery

Although rehabilitation medicine emphasizes a holistic health approach, there is still a large gap of knowledge about potential interventions aimed at improving overall wellbeing through cosmetic interventions. Therefore, this narrative review investigates the role of different rehabilitative techniques in enhancing aesthetics, quality of life, and psychosocial wellbeing for patients with disabilities. The study follows the SANRA framework quality criteria for a narrative review. Literature searches across PubMed/Medline, Web of Science, and Scopus identified articles focusing on rehabilitation strategies within the aesthetic rehabilitation domain. The review identified evidence supporting injection procedures, such as Botulinum Toxin, Platelet-Rich Plasma, Hyaluronic Acid, Ozone, and Carboxytherapy, and assessing their applications in several disabling disorders. Additionally, physical therapies like Extracorporeal Shock Wave Therapy, Laser Therapy, Microcurrent Therapy, Tecar Therapy, and physical exercises were explored for their impact on cutaneous microcirculation, cellulite treatment, wound healing, and scar appearance improvement. Lastly, the manuscript underlines the role of manual therapy techniques in addressing both physical discomfort and aesthetic concerns, discussing their effectiveness in adipose tissue therapy, scar tissue mobilization, and regional fat thickness reduction. Taken together, this review emphasizes the role of a multidisciplinary approach, aiming to provide valuable insights into potential benefits for both functional and aesthetic outcomes.

Translational Biochemistry of the Skin

Understanding translational biochemistry of the skin is an essential component in mastering non-invasive aesthetic treatments. Collagen is the most abundant protein in the animal kingdom and plays a significant role in maintaining structural function in biologically healthy human skin. Collagen degradation and synthesis occurs throughout human life. Upregulation of collagen synthesis remains the mainstay of non-invasive aesthetic skin treatments. Elastin is a smaller yet significant component in the skin's ability to maintain biologically healthy stretch and recoil. Multi-Omics represents a relatively nascent field in the optimization and development of therapies aimed at the aesthetic improvement of the skin.

New Directions in Aesthetic Medicine: A Novel and Hybrid Filler Based on Hyaluronic Acid and Lactose Modified Chitosan

Fillers based on crosslinked hyaluronic acid (HA) are becoming increasingly important in the field of aesthetic medicine, for example for treating wrinkles or for volumizing purposes. However, crosslinking agents are usually associated with toxicity and adverse reactions. The aim of this study is the development of an innovative technology to manufacture high performance HA-based fillers using minimal amounts of crosslinking agent. In this work, new fillers based on HA, functionalized with different amounts of 1,4-butanediol diglycidyl ether (BDDE) (degree of modification ranging between 3.5% and 8.8%) and formulated with a lactose modified chitosan (CTL), were investigated. The relative quantities of these polymeric building blocks in the formulations were 20-25 and 5 mg/mL for HA and CTL, respectively. Due to its cationic nature, CTL could interact with the anionic HA and enhance the elastic properties of the filler. Fillers manufactured with this novel technology (HACL-CTL) were characterized and compared with several fillers available in the market. In particular, resistance against hyaluronidase, swelling, cohesivity and rheological properties were investigated. Cohesivity, resistance to hydrolysis and swelling of HACL-CTL were comparable to commercial products. However, HACL-CTL fillers showed excellent elastic performance that reached 94% of elasticity in response to shear stresses. Surprisingly, these fillers also showed a resistance to compression higher than that of currently marketed products, making them very promising for their lifting effect.

Triple Cross-Linked Hyaluronic Acid Based on Tri-Hyal Technique Has More Durable Effect on Dermal Renewal

Background

Hyaluronic acid (HA)-based fillers are applied to treat facial wrinkles and volume loss. Many efforts have been made to improve properties of HA to prolong the duration in aesthetic indications. A new cross-linking technique called “Tri-Hyal”, could make HAs to achieve desired rheological characteristics. HAs synthesized by Tri-Hyal are triple cross-linked and sustained-release, which could increase duration of promoting skin rejuvenation after injection.

Purpose

To evaluate the efficiency and persistence of HAs with Tri-Hyal on skin rejuvenation and further investigate underlying mechanisms, we compared the performances of cross-linked HA (AF) based on Tri-Hyal with another highly acceptable HA filler (Res) in vivo and in vitro.

Methods

Male BALB/c mice were divided into three groups, treated with AF, Res and vehicle, respectively. Skin biopsies were taken on day 0, 30, 90 and 180 after injection and hematoxylin and eosin (H&E), Masson’s trichrome (MT), immunohistochemical (IHC) stainings for CD31, TGF-β and MMP9 were performed. EdU incorporation, cell counting kit-8 (CCK-8), SA-β-Gal staining and activity were measured by biochemical analysis. RFP-GFP-LC3 adeno virus was used for autophagic flux detection. Protein levels of CD44, P62 and LC3I/II were detected by Western blot. Reactive oxygen species (ROS) level was detected by flow cytometry with DCFH-DA probe.

Results

The AF synthesized by Tri-Hyal showed persistent dermal structural correction without attenuation up to 6 months, which was illustrated by skin thickness, formation of elastic fibers and vascular density. Consistently, in fibroblasts the AF improved cell proliferation and slowed the senescent in vitro. Furthermore, it promoted cellular autophagy to reduce ROS level, which would account for its function in skin renewal.

Conclusion

The HA with Tri-Hyal could stimulate the production of extracellular matrix components more persistently than traditional HA fillers. In terms of mechanisms, it delayed senescence in dermal fibroblasts through reducing oxidative stress mediated by induction of autophagy.

A Comparative Study between Conventional and Advanced Extraction Techniques: Pharmaceutical and Cosmetic Properties of Plant Extracts

This study aimed to compare the influence of extraction methods on the pharmaceutical and cosmetic properties of medicinal and aromatic plants (MAPs). For this purpose, the dried plant materials were extracted using advanced (microwave (MAE), ultrasonic (UAE), and homogenizer (HAE) assisted extractions) and conventional techniques (maceration, percolation, decoction, infusion, and Soxhlet). The tyrosinase, elastase, α-amylase, butyryl, and acetylcholinesterase inhibition were tested by using L-3,4 dihydroxy-phenylalanine, N-Succinyl-Ala-Ala-p-nitroanilide, butyryl, and acetylcholine as respective substrates. Antioxidant activities were studied by ABTS, DPPH, and FRAP. In terms of extraction yield, advanced extraction techniques showed the highest values (MAE > UAE > HAE). Chemical profiles were dependent on the phenolic compounds tested, whereas the antioxidant activities were always higher, mainly in infusion and decoction as a conventional technique. In relation to the pharmaceutical and cosmetic properties, the highest inhibitory activities against α-amylase and acetylcholinesterase were observed for Soxhlet and macerated extracts, whereas the highest activity against tyrosinase was obtained with MAE > maceration > Soxhlet. Elastase and butyrylcholinesterase inhibitory activities were in the order of Soxhlet > maceration > percolation, with no activities recorded for the other tested methods. In conclusion, advanced methods afford an extract with high yield, while conventional methods might be an adequate approach for minimal changes in the biological properties of the extract.

A Prospective, Open-Label Study to Evaluate the Impact of VYC-12L Injection on Skin Quality Attributes in Healthy Volunteers

Purpose

Age-related changes in skin structure and function can negatively impact skin quality. VYC-12L is a crosslinked hyaluronic acid filler for treating fine lines and improving hydration and elasticity. The goal of this study was to understand skin quality, histologic, and genomic changes underlying long-term clinical benefits of VYC-12L treatment.

Patients and Methods

In this prospective, nonrandomized, open-label study, 11 healthy men (n = 2) and women (n = 9) received intradermal VYC-12L treatment on the volar forearm. Clinical probes assessed skin quality at baseline and months 1 and 3 post-treatment. Punch biopsies were collected 1 and 3 months post-treatment to evaluate histologic and genomic changes. Safety was evaluated throughout.

Results

Participants had a mean age of 41 years and Fitzpatrick skin phototypes II (54.5%) and III (45.5%). At months 1 and 3, VYC-12L-treated skin had higher hydration in the stratum corneum than untreated skin. Cutometer measurements indicated treated skin that was firmer and more resistant to deformation. Histology showed increased epidermal AQP3 and Ki67 expression 1 and 3 months post-treatment and a qualitative increase in papillary dermal collagen I at month 3. Genomic analyses demonstrated treatment-related upregulation of genes involved in adipocyte differentiation, lipid metabolism, keratinocyte renewal, and dermal extracellular matrix (ECM) maintenance. Injection site reactions were mild-to-moderate in severity and resolved by month 1. Five participants reported 19 adverse events; most (68.4%) were related to the biopsy and none to VYC-12L.

Conclusion

VYC-12L produced changes in hydration, firmness, and ECM density and composition consistent with improved skin properties, demonstrating that VYC-12L can act as a substrate for tissue repair.

Use of subdermal hyaluronic acid injections and a free labial mucocutaneous graft for the repair of feline eyelid agenesis

OBJECTIVE

To describe a technique to repair feline eyelid agenesis using a hyaluronic acid (HA) subdermal filler injection to allow for acute soft tissue expansion, followed by a free labial mucocutaneous graft.

MATERIALS AND METHODS

Thirty-nine colobomatous eyelids in 24 feline patients with secondary keratitis were recruited to the study group.

RESULTS

Keratitis and trichiasis were markedly resolved in 27/39 (69.2%) eyelids after a single procedure. Post-operative HA subdermal filler injections were required to resolve 5/39 (12.8%) eyelids that had mild post-operative trichiasis, and 1/39 (2.5%) eyelids that had post-operative lateral canthal collapse. Complications occurred in 6/39 (15.4%) cases, consisting of distal graft necrosis (n = 2 eyes), suture rubbing the cornea (n = 2 eyes), moderate trichiasis (n = 1 eye) and graft adherence to the episclera (n = 1 eye).

CONCLUSION

The technique was successful in enhancing corneal protection, cosmesis and eyelid function and should be considered as a surgical option for any degree of eyelid agenesis in feline patients.

Non-Surgical Touch-Up with Hyaluronic Acid Fillers Following Facial Reconstructive Surgery

The use of hyaluronic acid (HA) injectable fillers has become increasingly widespread in facial recontouring and rejuvenation. We report our experiences to emphasize the role of HA fillers as tools beyond aesthetic treatments in cases of post-surgical facial sequelae. HA fillers are generally used for aesthetic rejuvenation, but one potential new horizon could be their application in trauma, reconstructive, and craniofacial surgery. This study was conducted retrospectively, evaluating medical reports of patients treated at the Maxillofacial Surgery Unit, University of Campania “Luigi Vanvitelli”, Naples, for lip incompetence, trauma, oncological, reconstructive, and craniosynostosis surgery sequelae. Visual analog scale (VAS) evaluation was performed to assess patient satisfaction. No major complications (i.e., impending necrosis or visual loss) were reported. Bruising and swelling was reported for 48 h after lip injection. At the immediate VAS evaluation, 67% of the patients were “extremely satisfied” and 33% “satisfied”. In those 33%, VAS scores changed to “extremely satisfied” at 6–9 weeks and 3–6 months of VAS evaluation (contextually to improvement in tissue flexibility, elasticity, and aesthetic appearance). Results indicate that this minimally invasive approach achieves a high level of aesthetic enhancement, improving patient satisfaction. The concept of HA filler applications could be a frontier that may be applicable to other areas of reconstructive facial plastic surgery.

Unravelling the Dermatological Potential of the Brown Seaweed Carpomitra costata

The ever-increasing interest in keeping a young appearance and healthy skin has leveraged the skincare industry. This, coupled together with the increased concern regarding the safety of synthetic products, has boosted the demand for new and safer natural ingredients. Accordingly, the aim of this study was to evaluate the dermatological potential of the brown seaweed Carpomitra costata. The antioxidant, anti-enzymatic, antimicrobial, photoprotective and anti-inflammatory properties of five C. costata fractions (F1-F5) were evaluated. The ethyl acetate fraction (F3) demonstrated the most promising results, with the best ability to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals (EC50 of 140.1 µg/mL) and the capacity to reduce reactive oxygen species (ROS) production promoted by UVA and UVB radiation in 3T3 cells, revealing its antioxidant and photoprotective potential. This fraction also exhibited the highest anti-enzymatic capacity, inhibiting the activities of collagenase, elastase and tyrosinase (IC50 of 7.2, 4.8 and 85.9 µg/mL, respectively). Moreover, F3 showed anti-inflammatory potential, reducing TNF-α and IL-6 release induced by LPS treatment in RAW 264.7 cells. These bioactivities may be related to the presence of phenolic compounds, such as phlorotannins, as demonstrated by NMR analysis. The results highlight the potential of C. costata as a source of bioactive ingredients for further dermatological applications.

Unravelling the Dermatological Potential of the Brown Seaweed Carpomitra costata

The ever-increasing interest in keeping a young appearance and healthy skin has leveraged the skincare industry. This, coupled together with the increased concern regarding the safety of synthetic products, has boosted the demand for new and safer natural ingredients. Accordingly, the aim of this study was to evaluate the dermatological potential of the brown seaweed Carpomitra costata. The antioxidant, anti-enzymatic, antimicrobial, photoprotective and anti-inflammatory properties of five C. costata fractions (F1–F5) were evaluated. The ethyl acetate fraction (F3) demonstrated the most promising results, with the best ability to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals (EC50 of 140.1 µg/mL) and the capacity to reduce reactive oxygen species (ROS) production promoted by UVA and UVB radiation in 3T3 cells, revealing its antioxidant and photoprotective potential. This fraction also exhibited the highest anti-enzymatic capacity, inhibiting the activities of collagenase, elastase and tyrosinase (IC50 of 7.2, 4.8 and 85.9 µg/mL, respectively). Moreover, F3 showed anti-inflammatory potential, reducing TNF-α and IL-6 release induced by LPS treatment in RAW 264.7 cells. These bioactivities may be related to the presence of phenolic compounds, such as phlorotannins, as demonstrated by NMR analysis. The results highlight the potential of C. costata as a source of bioactive ingredients for further dermatological applications.

The Effects of Subcutaneously Injected Novel Biphasic Cross-Linked Hyaluronic Acid Filler: In Vivo Study

BACKGROUND

Biphasic hyaluronic acid (HA) fillers have been used extensively to improve facial skin. However, in some cases, the skin surface is irregular because of the premature loss of HA solution. We propose a new biphasic filler (G-filler) to overcome this problem by using small particles of HA hydrogel instead of HA solution, which can provide a smooth skin surface and good durability.

METHOD

We evaluated the rheologic properties of G-filler and its physiologic effects after subcutaneous injection in a mouse model by histologic analysis.

RESULTS

The G-filler showed a similar elastic modulus (G') and complex viscosity (η*) as the conventional biphasic filler, but had a higher viscous modulus (G″) than the conventional monophasic filler. The highest material elasticity (tan δ) value and the lowest percentage elasticity value indicate the rheologic properties of G-filler are closer to those of liquids. After subcutaneous injection of G-filler, collagen content (~ 2-fold) and elastin fibers (~ 6.5-fold) were significantly increased at 12 weeks compared to those of the saline group. Fibronectin (~ 2.6-fold) and the laminin-immunolabeled cell number (~ 6-fold) were also significantly increased at 12 weeks. Significant increases in the CD31-immunoreactive cell numbers of the G-filler groups were observed at 2, 6, and 12 weeks (~ 3.7-fold) compared to those of the saline groups. There were no significant differences between the G-filler and saline groups in patterns of skin thickness and inflammatory cell numbers around loading sites.

CONCLUSION

These findings demonstrate that the injection of a new biphasic filler with improved rheologic properties can effectively stimulate extracellular matrix production and angiogenesis without safety concerns.

NO LEVEL ASSIGNED

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Comparison of polycaprolactone and calcium hydroxylapatite dermal fillers in a rat model

Polycaprolactone (PCL) and calcium hydroxylapatite (CaHA) are semipermanent dermal fillers that are frequently preferred in the last decade. This study aims to compare the effects of these two fillers in the rat skin. A total of 30 female rats were divided into; control, PCL, and CaHA group. Tissue samples taken at the second and fourth month were stained with hematoxylin-eosin, Masson trichrome, collagen type 1, and 3 immunohistochemical antibodies. Collagen density was quantitatively compared using the Image J computer program. At 2 and 4 months, the density of collagen increased in both filler groups compared to the control group. There was no significant difference between collagen density or type 1 and type 3 collagen H scores in the filler groups. The number of fibroblast nuclei was significantly higher in the PCL group at 4 months compared to the other two groups. Dermis thickness was found to be superior in both filler groups compared to the control group at the fourth month, there was no significant difference between the filler groups. We compared the effect of CaHA and PCL filler on collagenization histologically and immunohistochemically. We found that PCL and CaHA fillers are effective in increasing dermal collagen density, type 1 and type 3 collagen amount, and preventing dermis atrophy and showed that they have no advantage over each other in this respect. We have shown that PCL filler provides more fibroblast increase compared to CaHA filler and the effect of stimulating fibroblast proliferation takes longer.

The Correction of Facial Morphea Lesions by Hyaluronic Acid: A Case Series and Literature Review

INTRODUCTION

The aim of the study is to assess the long-term safety and efficacy of hyaluronic acid (HA) administration in correction of facial morphea lesions and to review the literature on the subject. Morphea is a chronic inflammatory disease of the connective tissue which may lead to serious deformations. The lesions located on the face particularly affect patients' quality of life and self-esteem; thus, there is a demand for safe and effective methods of treatment.

CASE PRESENTATION

The paper presents three female patients aged 16, 17 and 70 with facial morphea lesions who had HA preparation Juvéderm® Voluma or Volux, Vycross® technology, Allergan, injected. One of the patients had additionally fractional ablative CO2 laser (FAL) therapy.

DISCUSSION

The literature provides reports on successful use of HA, polymethylmethacrylate and poly-L-lactic acid for the correction of facial defects in localized scleroderma. HA is a natural component of the extracellular matrix and it therefore minimizes the probability of immunogenicity. The application technique also plays an important role. On the other hand, FAL therapy leads to the degradation of the abnormal collagen and the induction of normal collagen synthesis.

CONCLUSIONS

HA injection and combination of HA application with FAL are minimally invasive, effective and safe therapeutic options for patients suffering from morphea.

Effect of Hyaluronic Acid and Poly-L-Lactic Acid Dermal Fillers on Collagen Synthesis: An in vitro and in vivo Study

Purpose

Skin ageing is marked by structural and functional changes in epidermis and dermis, which result clinically in wrinkles, loss of elasticity, and rough-textured appearance. In this context, different dermal fillers have been used to overcome these negative effects associated with skin ageing, such as hyaluronic acid (HA) and poly-L-lactic acid (PLLA). Despite their low immunogenicity, these materials can cause an inflammatory reaction after application.

Materials and Methods

Considering high demand of HA and PLLA as filler material, this study aimed to evaluate their in vitro and in vivo effects. For the in vitro study, human dermal fibroblast cell cultures were supplemented with HA or PLLA for 24, 48, and 72 h. The following parameters were assayed: 1) cell proliferation, 2) cell viability, and 3) quantification of type I collagen by ELISA. For the in vivo study, HA or PLLA was injected in the dermis of Wistar rats and the tissues were collected after 15, 30, and 60 days for histologic evaluation and for quantification of type I collagen by Western blotting. The quantitative data were statistically analyzed using an ANOVA two-way. The significance level was set at 5%.

Results

At 72 h, high cell proliferation was observed for HA compared to control (p<0.05). Cultures exposed to PLLA exhibited a reduction in both cell proliferation and viability compared to control in all time points (p<0.05). Type I collagen expression was greater in cultures exposed to HA or PLLA compared to control (p<0.05). Histologic analysis showed the presence of multinucleated cells only in the PLLA group in all experimental time points. Western blotting analysis revealed high content of type I collagen in HA compared to PLLA (p<0.05).

Conclusion

The present study addresses a potentially unfavorable effect of dermal PLLA filler on the fibroblast phenotype, with possible clinical complications, unlike HA.

Effect of Hyaluronic Acid Filler Injection on the Interdental Papilla in a Mouse Model of Open Gingival Embrasure

The black triangle resulting from interdental papilla (IDP) loss is associated with poor aesthetics and difficulty in pronunciation and food impaction. There is limited knowledge of gingival tissue inflammatory response to hyaluronic acid (HA) filler injection, a minimally invasive IDP reconstruction method. This study aimed to examine the morphological and histological changes in IDP and the inflammatory cytokine localization to the IDP post-HA filler injection using an open gingival embrasure (OGE) mouse model. Mice from the control, sham, and OGE groups were attached with reference, inactive, and activated wires for 5 days, respectively. The degree of IDP loss was determined based on the spring-papilla distance (SPD). Morphological and histological changes in the OGE group injected with phosphate-buffered saline (PBS) or HA fillers were examined on days 2 and 7 post-injection. Immunohistochemical analysis was performed to determine the localization patterns of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, myeloperoxidase (MPO), and Ki67. Five days post-wire attachment, the control and OGE groups exhibited a significantly higher SPD than the sham group (p < 0.0167). The SPD of the HA filler injection group was significantly lower than that of the PBS injection group on days 2, 4, and 7 post-injection (p < 0.05). The IDP of the OGE group was wide and flat. HA filler was stable in the connective tissue underlying the epithelial tissue even on day 7 post-injection. TNF-α, IL-1β, IL-6, MPO, and Ki67 were highly localized to the connective tissue surrounding the filler on day 2, which decreased on day 7 post-injection. Thus, HA filler can safely and successfully reconstruct the IDP in cases of OGE.

Improvements in Skin Quality Biological Markers in Skin Explants Using Hyaluronic Acid Filler VYC-12L

Hyaluronic acid (HA), both crosslinked and uncrosslinked, is used clinically to treat fine lines and provides additional improvements in skin quality attributes. The purpose of this study was to assess potential early differences in the expression of biological markers of skin quality in living human skin explants injected with uncrosslinked and crosslinked HA gels.

Methods

Living human skin explants injected with VYC-12L or noncrosslinked HA with mannitol (HYD) and noninjected controls were assessed via microscopy, histology, and immunohistochemistry on days 3 and/or 8 for biological markers of elasticity (collagen density, elastin, fibrillin-1) and hydration [aquaporin-3, acidic glycosaminoglycans (GAGs), HA]. Hydration was also assessed via a corneometer probe on days 0, 1, 2, and 8.

Results

On day 3 versus controls, VYC-12L moderately increased collagen density in the upper reticular dermis and clearly increased fibrillin-1 expression, with slight increases persisting on day 8. Increases with HYD were smaller and did not persist on day 8. Both VYC-12L and HYD increased aquaporin-3 expression and GAG content on days 3 and 8, but VYC-12L produced greater GAG increases in the reticular dermis. Day 8 instrument-assessed hydration increased by 49% and 22% for VYC-12L and HYD, respectively. Elastin expression in oxytalan and elaunin fibers was unchanged. Upper-dermal HA reductions suggested HA injection-induced hyaluronidase expression.

Conclusion

VYC-12L produced greater, more lasting improvements in biological markers of skin quality than HYD.

Comparison of Volume Retention and Biocompatibility of Acellular Dermal Matrix/Hyaluronic Acid Filler to Autologous Fat Grafts in a Mouse Model

BACKGROUND

Although fat grafting has become a widely used technique in aesthetic and reconstructive surgeries, resorption is still a challenge. Micronized acellular dermal matrix (ADM) has been considered as a stable, biocompatible soft tissue coverage material that can be used as a volume filler. Here, we compared the bioacceptance and sustainability of ADM hyaluronic acid (HA) filler with human fat graft in a mouse model.

METHODS

Harvested human fat and ADM/HA filler were injected randomly on the dorsal side of mice. Thirty-two mice were analyzed over a 7-week period with respect to volume, weight and microscopic evaluations with hematoxylin and eosin (H&E), epidermal growth factor (EGF) and vascular endothelial growth factor (VEGF) staining.

RESULTS

The volume and weight were maintained at 80% and 83%, respectively, in the ADM/HA filler group and 56.5% and 49.7%, respectively, in the fat-grafted group by the 7th week. There were no significant microscopic differences in inflammatory changes and granulation via H&E staining. At 1 and 2 weeks, EGF and VEGF immunostaining intensity scores were lower in the ADM/HA filler group. At 7 weeks, there were no significant differences in immunostaining intensity scores between the two groups.

CONCLUSIONS

During the 7-week experimental period, the ADM/HA filler showed no foreign body reaction and the proper volume was well maintained. This suggests that the ADM/HA filler can possibly be used in small amounts as an alternative to autologous fat grafts.

NO LEVEL ASSIGNED

This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authorshttp://www.springer.com/00266.

A multi-center, open-label, pilot study of allograft adipose matrix for the correction of atrophic temples

BACKGROUND

Autologous fat grafting (AFG) and synthetic fillers are currently used in esthetic and reconstructive surgery. Challenges in AFG include inconsistent graft retention, donor site morbidities, insufficient harvest, and excessive harvesting times. An allograft adipose matrix (AAM) has been developed as an off-the-shelf alternative to AFG and synthetic fillers.

AIMS

To evaluate the clinical safety and retention of an AAM over 24 weeks after treatment of bilateral atrophic temples.

PATIENTS/METHODS

Ten subjects (nine females, one male, aged 47-69 years) with temple atrophy were enrolled in the IRB-approved study. AAM (Renuva^® , MTF Biologics, Edison, NJ) was injected (<3 mL) bilaterally into the atrophic temples of each subject. Volume retention, global improvement, and safety were evaluated at 1, 4, 8, 12, 16, 20, and 24 weeks. Biopsy specimens were obtained for adipogenic and angiogenic histological evaluation.

RESULTS

The mean temple volume improved over the baseline and was retained throughout the study period. Fullness (measure of volume) increased immediately from 0 pretreatment to 2.8 post-treatment (scale 0-4 = none-maximum). Fullness varied from 0.8 to 2.2 from weeks 1 through 12 and was 2.7-3.0 from weeks 16-24, around 75% increase from baseline. Furthermore, skin tone, smoothness, texture, and overall appearance also improved with 71% of subjects being satisfied to very satisfied with the results. Adverse events were minimal and histology revealed native tissue incorporation and remodeling.

CONCLUSION

AAM is safe and well tolerated, provides at least 6-month volume retention, improves skin quality, and supports adipose tissue remodeling after treatment into temples.

Hyaluronan Dermal Fillers: Efforts Towards a Wider Biophysical Characterization and the Correlation of the Biophysical Parameters to the Clinical Outcome

Introduction

Hyaluronic Acid (HA) fillers are among the most used products in cosmetic medicine. Companies offer different formulations to allow full facial treatment and/or remodeling. Gels are being studied to establish the biophysical properties behind the specific clinical use and a correlation between the gel biophysical properties and their clinical performance. Clinicians' awareness is growing about the potential benefit deriving from such biophysical characterization.

Aim

The Aliaxin^® line of HA dermal fillers is the object of this study. The study aimed to widen the biophysical characterization of these gels by investigating a variety of properties to better support their optimal use. Further, we aimed to provide some clinical findings to gain a deeper insight into the correlation between filler features and clinical outcome.

Methods

The four gels of the line were investigated, for the first time, for their cohesivity and stability to Reactive Oxygen Species (ROS). Additional secondary rheological parameters; evidence of relative water-uptake ability; and some clinical findings on product safety, palpability and duration of the aesthetic effect are provided.

Results and conclusion

The gels proved highly cohesive and sensitive to ROS action with stability declining with the decrease in the overall gel elasticity. The G* and complex viscosity values at clinically relevant frequencies and gel water-uptake ability are consistent with the relative clinical indication related to gel projection and hydration capacity. Clinical outcomes showed the safety of the products and a perception of palpability well correlating with the cohesive/viscosity properties of the gels. A similar duration of the aesthetic effect (up to 1 year) was observed despite the diverse in vitro gel stability. The results broaden our knowledge of these gels and may contribute to optimize their clinical use towards the improvement of patient safety and satisfaction. Initial clinical observation indicated that gel biophysical properties allow for a reliable prediction of gel palpability, while in vitro data on gel stability cannot be related to the duration of the observed skin improvement. The latter finding further corroborates the idea of a skin restoration process activated by the gels besides the physical volumetric action.

Hyaluronan-based hydrogels as dermal fillers: The biophysical properties that translate into a "volumetric" effect

Biophysical and biochemical data on hyaluronan (HA)-based dermal fillers strongly support their optimal use and design to meet specific requisites. Here, four commercially available (in Europe) HA "volumetric" fillers, among the most used in the clinical practice, have been characterized in vitro. Analyses revealed the highest amounts of water-soluble HA reported so far and provided hydrodynamic data for these soluble polymeric fractions. Volumetric gels exhibit a wide range of rigidity with most of them showing G' values around 200-300Pa. They greatly differ in cohesivity. 1mL of gel hydrates up to 2.4-3.2mL. The products completely solubilize due to Bovine Testicular Hyaluronidase (BTH)'s action, thus predicting in vivo complete resorption. For the first time, filler degradation due to reactive oxygen species (ROS) was studied by rheological measurements and a rank in stability was established. Studies using Human Dermal Fibroblasts (HDF) indicated a positive biological response to the HA networks. Further, gel capacity to prompt collagen I, elastin and aquaporin3 synthesis was demonstrated, thus suggesting a positive effect on skin elasticity and hydration, besides the physical volumetric action. The findings are the first wide assessment of features for the volumetric class of HA-fillers and include first data on their resistance to degradation by ROS and biological effects on HDF. The study represents a valuable contribution to the understanding of HA-fillers, useful to optimize their use and manufacture.

Dual-plane hyaluronic acid treatment for atrophic acne scars

BACKGROUND

Acne is a common condition that affects up to 80% of all adolescents. Scarring may affect some 95% as a function of severity and delay before treatment. The pathogenesis includes enzymatic degradation of collagen fibers and subcutaneous fat.

OBJECTIVE

This study aimed to treat atrophic acne scars using the Dual-Plane injection of Hyaluronic Acid.

METHODS

A total of 12 patients with moderate-to-severe atrophic acne scars were treated with a novel NAHYCO™ based Hyaluronic Acid filler, using a dual-plane technique for two treatment sessions at a 4-week interval. Results were objectively assessed by two blinded Dermatologists and subjectively evaluated by the patients themselves.

RESULTS

A total of 8 out of the 12 patients reported moderate improvement, two indicated marked improvement and two rated minimal improvement. Dermatologists' mean global evaluation score was 2.5 ± 0.43.

LIMITATIONS

The small sample size and regional nature of a single-center study. Nevertheless, both the expert dermatologists' and the patients' evaluations of standardized high-resolution medical photographs were consistent, suggesting that this inherent bias was negligible.

CONCLUSION

The treatment led to impressive improvement in the depth of the scars, suggesting that this technique can result in safe and rapid amelioration of atrophic acne scars in only two sessions.

Evaluation of the In Vivo Kinetics and Biostimulatory Effects of Subcutaneously Injected Hyaluronic Acid Filler

BACKGROUND

Because subcutaneously injected hyaluronic acid filler is absorbed over 6 months to 1 year after the treatment of facial wrinkles, frequent retreatment may be required. However, persistent long-term effects are often clinically observed when hyaluronic acid filler is injected as a bolus for facial augmentation. Therefore, the authors investigated, over time, the changes in volume and histologic features of subcutaneous bolus injections of hyaluronic acid.

METHODS

Hyaluronic acid filler was subcutaneously injected as a bolus into the dorsum of 6-week-old rats. At several time points (immediately after injection and 4, 8, 16, 32, and 64 weeks thereafter), magnetic resonance imaging was introduced to observe morphologic changes and to measure volume. Histologic examination of sectioned tissues was also performed.

RESULTS

The average volume increased for up to 4 weeks after injection and then gradually decreased, with 74.8 percent of the injected volume remaining after 64 weeks, with no statistical difference compared to the initial volume. Histologic analysis revealed that lattice structures were created by fibroblasts and collagen fibers, and blood vessels and adipocytes were also generated in the filler.

CONCLUSIONS

Although subcutaneous bolus injections of hyaluronic acid filler exhibited flattening, the total volume was maintained even after 64 weeks. Histologically, hyaluronic acid filler acted as a scaffold for autogenous tissue replacement by means of fibroblast migration and proliferation, collagen induction, and angiogenesis, followed by proliferation of adipocytes. This study demonstrates that the total volume is maintained long-term by replacing part of the injected hyaluronic acid filler with autologous tissues.

Complication Management following Rejuvenation Procedures with Hyaluronic Acid Fillers-an Algorithm-based Approach

BACKGROUND

Hyaluronic acid is an ideal facial filler, however, although established as both safe and effective, complications do occur. Treatment recommendations that combine both expert opinions and clinical trial data are currently lacking, partly due to difficulties with diagnoses, nonspecific diagnostic investigations, and certain disorders presenting with similar symptoms, thereby confounding diagnosis and treatment.

METHODS

The purpose of this article was to provide the aesthetic clinician with practical recommendations regarding complication diagnosis arising as a consequence of hyaluronic acid filler rejuvenation treatment. It also provides recommendations for their management using step-wise treatment algorithms that are based on published expert opinions, as well as the author's clinical experience.

RESULTS

Algorithms are provided for the most common categories of complication associated with hyaluronic acid filler treatment, that is, skin discoloration, edema, nodules, infection, and vascular compromise.

CONCLUSIONS

These guidelines are not intended to be complete or exhaustive but may prove informative for aesthetic clinicians who are responsible for treating patients with hyaluronic acid fillers. It may help to guide them on recognizing potential complications and it provides clear guidance on optimum treatment pathways.

Hyaluronic acid, a promising skin rejuvenating biomedicine: A review of recent updates and pre-clinical and clinical investigations on cosmetic and nutricosmetic effects

Hyaluronic acid (HA) plays multifaceted role in regulating the various biological processes such as skin repairmen, diagnosis of cancer, wound healing, tissue regeneration, anti-inflammatory, and immunomodulation. Owing to its remarkable biomedical and tissue regeneration potential, HA has been numerously employed as one of the imperative components of the cosmetic and nutricosmetic products. The present review aims to summarize and critically appraise recent developments and clinical investigations on cosmetic and nutricosmetic efficacy of HA for skin rejuvenation. A thorough analysis of the literature revealed that HA based formulations (i.e., gels, creams, intra-dermal filler injections, dermal fillers, facial fillers, autologous fat gels, lotion, serum, and implants, etc.) exhibit remarkable anti-wrinkle, anti-nasolabial fold, anti-aging, space-filling, and face rejuvenating properties. This has been achieved via soft tissue augmentation, improved skin hydration, collagen and elastin stimulation, and face volume restoration. HA, alone or in combination with lidocaine and other co-agents, showed promising efficacy in skin tightness and elasticity, face rejuvenation, improving aesthetic scores, reducing the wrinkle scars, longevity, and tear trough rejuvenation. Our critical analysis evidenced that application/administration of HA exhibits outstanding nutricosmetic efficacy and thus is warranted to be used as a prime component of cosmetic products.

Hyaluronan chemistries for three-dimensional matrix applications

Hyaluronan is a ubiquitous constituent of mammalian extracellular matrices and, because of its excellent intrinsic biocompatibility and chemical modification versatility, has been widely employed in a multitude of biomedical applications. In this article, we will survey the approaches used to tailor hyaluronan to specific needs of tissue engineering, regenerative and reconstructive medicine and overall biomedical research. We will also describe recent examples of applications in these broader areas, such as 3D cell culture, bioprinting, organoid biofabrication, and precision medicine that are facilitated by the use of hyaluronan as a biomaterial.

Tissue Expansion Using Hyaluronic Acid Filler for Single-Stage Ear Reconstruction: A Novel Concept for Difficult Areas

BACKGROUND

Auricular reconstruction is one of the most challenging procedures in plastic surgery. An adequate skin envelope is essential for cartilage framework coverage, yet few good options exist without additional surgery. We propose a novel method for minimally invasive tissue expansion, using hyaluronic acid (HA) filler to allow for single-stage ear reconstruction.

OBJECTIVES

To introduce the novel concept of HA filler for tissue expansion in ear reconstruction, and as an alternative to traditional expansion techniques.

METHODS

Macrolane is a large particle HA gel developed for large volume restoration. Expansion of the non-hair-bearing mastoid skin was performed in our clinic weekly or every other week. Final expansion was completed one week prior to reconstructive surgery. Tissue from one patient's expanded pocket was sent for histological analysis.

RESULTS

Ten patients underwent single-stage auricular reconstruction with preoperative expansion. Injection sessions ranged from 7 to 13 (mean, 9.7). Mean injected volume per session was 2.03 mL per patient, for an average total of 19.8 mL (range, 14.5-30 mL). There were no major complications. One minor complication required removal of exposed wire from the antihelix in the office. Hematoxylin and eosin stain revealed similar histology to that seen with traditional expanders.

CONCLUSIONS

This novel expansion technique using serial HA injections allowed for optimized skin coverage in single-stage ear reconstruction. The concept of tissue expansion using HA filler is a new frontier for research that may be applicable to other arenas of reconstruction.

LEVEL OF EVIDENCE

4.

Regenerative Medicine and Stem Cells in Dermatology

BACKGROUND

Clinically relevant regenerative medicine is still in its early stages of development. Difficulties in regenerating large-scale and complex structures, the lack of safety data, and the paucity of clinical trials have slowed the process of technological advance.

OBJECTIVE

To familiarize the clinician with techniques available in the laboratory and experimental approaches being tested clinically. In addition, a layout is discussed for how dermatologists can lead the way in bringing regenerative medicine to clinical reality.

METHODS

This article reviews the relevant literature on regenerative medicine for dermatological applications and discusses findings and techniques in a clinically relevant context.

RESULTS

Multiple cell-free and cell-based approaches for regenerating dermatologic tissues have been reported in the basic science and clinical literature. These are reviewed in the order of complexity.

CONCLUSION

Incremental steps are needed to apply the principles of regenerative medicine to simple medical problems first. Such a stepwise approach would commence, for example, with creation of single-function tissues that could fill soft-tissue defects and proceed to the development of fully functional skin grafts. Likewise, cell-free approaches can build the foundation for the more technically demanding cell-based strategies that are likely necessary for achieving the ultimate goal of regenerative dermatology.

The Effect of Hyaluronic Acid Application on the Perisilicon Capsule Structure

BACKGROUND

Silicon implants constitute a major part of plastic surgery practice. Although materials with high biocompatibility have been used around the implants, capsule formation still develops and progressive nature of this process results in capsule contraction. The aim of this study is to evaluate the effects of hyaluronic acid injected around the silicon block on the capsule structure.

METHODS

Twenty Wistar albino rats were used in the study. Rats were divided into two main groups (group 1 and group 2) and two subgroups. Rats in group 1 were sacrificed in week 4 and rats in group 2 were sacrificed in week 8. A subcutaneous pouch was created in the dorsum of the rats and a silicon block was placed into the pouch in groups 1A and 2A. 0.2 ml of hyaluronic acid was injected around the silicon block in group 1B and group 2B. Rats were sacrificed and capsule structure and thickness were analyzed following macroscopic evaluation. Concentrations of transforming growth factor-β1 (TGF-β1) and heat shock protein-47 (HSP-47) were evaluated immunohistochemically, and statistical comparisons were made.

RESULT

Capsule structure consisted of three layers in all the groups. A more intense collagen structure was observed in the middle layer. The capsule was thinnest in group 1A and thickest in group 2B; the difference between the groups was statistically significant. TGF-β1 was most intense in group 2B and it was correlated with the amount of collagen. Involvement of HSP-47 was observed mainly in collagen and also in fibroblasts and vascular structures, and its concentration was found to be lower in groups 2A and 2B.

CONCLUSION

Exogenously added cross-linked hyaluronic acid increased the capsular thickness and may increase the risk of developing capsular contracture around silicone implants.

LEVEL OF EVIDENCE II

Evidence was obtained from the well-designed controlled trials without randomization.

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.

Long-lasting and bioactive hyaluronic acid-hydroxyapatite composite hydrogels for injectable dermal fillers: Physical properties and in vivo durability

Hyaluronic acid (HAc)–hydroxyapatite (HAp) composite hydrogels were developed to improve the biostability and bioactivity of HAc for dermal filler applications. Two kinds of HAc-HAp composite fillers were generated: HAcmicroHAp and HAc-nanoHAp composites. HAc-microHAp was fabricated by mixing HAp microspheres with HAc hydrogels, and HAc-nanoHAp was made by in situ precipitation of nano-sized HAp particles in HAc hydrogels. Emphasis was placed on the effect of HAp on the durability and bioactivity of the fillers. Compared with the pure HAc filler, all of the HAc-HAp composite fillers exhibited significant improvements in volumetric maintenance based on in vivo tests owing to their reduced water content and higher degree of biointegration between the filler and surrounding tissues. HAc-HAp composite fillers also showed noticeable enhancement in dermis recovery, promoting collagen and elastic fiber formation. Based on their long-lasting durability and bioactivity, HAc-HAp composite fillers have great potential for soft tissue augmentation with multifunctionality.

Biophysical and biological characterization of a new line of hyaluronan-based dermal fillers: A scientific rationale to specific clinical indications

Chemico-physical and biological characterization of hyaluronan-based dermal fillers is of key importance to differentiate between numerous available products and to optimize their use. These studies on fillers are nowadays perceived as a reliable approach to predict their performance in vivo. The object of this paper is a recent line of hyaluronic acid (HA)-based dermal fillers, Aliaxin®, available in different formulations that claim a complete facial restoration. The aim of the study is to provide biophysical and biological data that may support the clinical indications and allow to predict performance possibly with respect to similar available products. Aliaxin® formulations were tested for their content in soluble HA, water uptake capacity, rheological behavior, stability to enzymatic degradation, and for in vitro capacity to stimulate extracellular matrix components production. The formulations were found to contain a low amount of soluble HA and were equivalent to each other regarding insoluble hydrogel concentration. The different crosslinking degree declared by the producer was consistent with the trend in water uptake capacity, rigidity, viscosity. No significant differences in stability to enzymatic hydrolysis were found. In vitro experiments, using a full thickness skin model, showed an increase in collagen production in the dermoepidermal junction. Results support the claims of different clinical indications, the classification of products regarding hydro-, lift-action and the specifically suggested needle gauge for the delivery. The biological outcomes also support products effectiveness in skin structure restoration. These data predicted a better performance regarding hydro-action, tissue integration, clinical management during delivery, and a high durability of the aesthetic effect when compared to data on marketed similar products.

Key importance of compression properties in the biophysical characteristics of hyaluronic acid soft-tissue fillers

Hyaluronic acid (HA) soft-tissue fillers are the most popular degradable injectable products used for correcting skin depressions and restoring facial volume loss. From a rheological perspective, HA fillers are commonly characterised through their viscoelastic properties under shear-stress. However, despite the continuous mechanical pressure that the skin applies on the fillers, compression properties in static and dynamic modes are rarely considered. In this article, three different rheological tests (shear-stress test and compression tests in static and dynamic mode) were carried out on nine CE-marked cross-linked HA fillers. Corresponding shear-stress (G', tanδ) and compression (E', tanδc, normal force FN) parameters were measured. We show here that the tested products behave differently under shear-stress and under compression even though they are used for the same indications. G' showed the expected influence on the tissue volumising capacity, and the same influence was also observed for the compression parameters E'. In conclusion, HA soft-tissue fillers exhibit widely different biophysical characteristics and many variables contribute to their overall performance. The elastic modulus G' is not the only critical parameter to consider amongst the rheological properties: the compression parameters E' and FN also provide key information, which should be taken into account for a better prediction of clinical outcomes, especially for predicting the volumising capacity and probably the ability to stimulate collagen production by fibroblasts.

Cohesive Polydensified Matrix Hyaluronic Acid for Fine Lines

BACKGROUND

Fine lines and crepey skin are dermal manifestations of multilevel, age-related volume loss. It is, therefore, logical to combine intradermal volumetry for fine lines with subcutaneous volumetry for contours. This publication provides evidence- and experience-based rationales for application of cohesive polydensified matrix hyaluronic acid filler (Belotero Balance).

METHODS

Evidence level II data demonstrate efficacy of this product and longevity for up to a year or more with intradermal, superficial blanch injection. Its softness, flow tendencies, and homogeneous tissue integration are informed by low elasticity (G') and viscosity, high cohesivity, and high tan delta. Ultrastructural analysis confirms variable-density cross-linking, intended to confer resilience, and absence of detectable particles, minimizing Tyndall effect.

RESULTS

Scientific properties of Belotero Balance predict its 3-dimensional tissue expansion with prominent horizontal vectoring. We define this as superficial flow volumetry. High cohesivity and resilience can maintain structural integrity in typically mobile facial areas with strong muscular forces, uneven pressure, and significant hyaluronidase activity. This facilitates a natural appearance, both in repose and animation.

CONCLUSIONS

Based on available evidence and experience, cohesive polydensified matrix hyaluronic acid is a notably efficacious fine line filler. The ideal fine line filler would restore dermis structurally and dynamicaly-moving as one with it, efficaciously expanding it, withstanding mechanical stress, swelling minimally, and potentially stimulating collagenesis. The relative contributions of space-filling, water binding, and collagenesis have implications for efficacy. A focus of current research is to determine the impact of filler cohesivity and tissue integration on these ideal qualities.

Development and characterization of a rapid polymerizing collagen for soft tissue augmentation

A liquid collagen has been developed that fibrilizes upon injection. Rapid polymerizing collagen (RPC) is a type I porcine collagen that undergoes fibrillization upon interaction with ionic solutions, such as physiological solutions. The ability to inject liquid collagen would be beneficial for many soft tissue augmentation applications. In this study, RPC was synthesized and characterized as a possible dermal filler. Transmission electron microscopy, ion induced RPC fibrillogenesis tests, collagenase resistance assay, and injection force studies were performed to assess RPC's physicochemical properties. An in vivo study was performed which consisted of a 1‐, 3‐, and 6‐month study where RPC was injected into the ears of miniature swine. The results demonstrated that the liquid RPC requires low injection force (<7 N); fibrillogenesis and banding of collagen occurs when RPC is injected into ionic solutions, and RPC has enhanced resistance to collagenase breakdown. The in vivo study demonstrated long‐term biocompatibility with low irritation scores. In conclusion RPC possesses many of the desirable properties of a soft tissue augmentation material. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 758–767, 2016.