Comparative physical properties of hyaluronic acid dermal fillers

A 52-week follow-up, multi-center, randomized, double-blinded comparison of efficacy and safety of two hyaluronic acid fillers for the treatment of moderate-to-severe nasolabial folds in Chinese population

INTRODUCTION

To investigate the efficacy and safety of Cutegel® MAX (Cutegel) in the correction of moderate-to-severe nasolabial folds (NLFS) compared to Restylane® (Restylane, control).

METHODS

This study was a 52-week, multicenter, randomized, double-blinded, active-controlled clinical trial. Qualified participants with moderate-to-severe NLFs were randomly assigned in a 1:1 ratio to receive Cutegel or Restylane. For the primary efficacy endpoint, the response rate was defined as the percentage of subjects exhibiting an improvement of at least one-point based on blinded evaluation of Wrinkle Severity Rating Scale (WSRS) at 24 weeks after injection. Other secondary efficacy endpoints and treatment-emergent adverse events (TEAEs) were assessed.

RESULTS

Of 340 subjects randomized, 317 completed the week 52 visit. In the per protocol set (PPS), the blinded evaluator-assessed response rates at week 24 were 81.17% for Cutegel versus 77.56% for Restylane (p =  0.327). The between-group treatment differences in response rates were 3.60% [95% confidence interval (CI) = (-5.39%, 12.60%)], which demonstrated the noninferiority of Cutegel. Other secondary efficacy endpoints supported this. No significant differences were observed in the occurrence of adverse events between the two groups.

CONCLUSION

Similar to Restylane, Cutegel was effective and well tolerated in correcting moderate-to-severe NLFs among the Chinese population.

Resolve and dissolve-An ultrasound-guided investigation on the effects of hyaluronidase on different soft tissue fillers

BACKGROUND

Nonsurgical cosmetic procedures, particularly the use of hyaluronic acid (HA)-based soft tissue fillers, are becoming increasingly popular. This trend has catalyzed the development of a plethora of HA-based products differing in product characteristics, thereby catering to an ever-widening spectrum of aesthetic applications. However, complications rise concomitant with the increasing number of procedures. Among the strategies to manage such adverse events is the enzymatic breakdown with hyaluronidase.

OBJECTIVE

To analyze the response of different HA-based soft tissue filler materials to hyaluronidase injections.

METHODS

A total of 11 different HA-based soft tissue fillers were evaluated using noninvasive ultrasound imaging to assess their behavior in response to hyaluronidase injections. The HA-based soft tissue fillers were categorized according to their product characteristics into a structuring, volumizing, and lip volumizing group. Standardized injections of 0.2 cc were performed in chicken breast to simulate human tissue. Ultrasound measurements of width, height, and calculated volume were performed immediately after filler injection, 1 h and 24 h following hyaluronidase injection.

RESULTS

Regardless of the soft tissue filler analyzed, the most significant volume reduction occurred within the first h after applying hyaluronidase, with a 64.1% decrease from the initial volume. After 24 h, the total volume reduction reached 81.7%. No statistically significant differences were found when comparing the three groups at each follow-up time period, except for the height measurement after 1 h. While width was statistically significant in all groups between the investigated follow-up groups, the volume reduction was only statistically significant in the groups with the highest and second highest G' values (i.e., Group 1-structuring, Group 2-volumizing).

CONCLUSION

The effectiveness of hyaluronidase in dissolving HA-based fillers is initially independent of product characteristics of HA-based fillers such as G-prime, with increased efficacy in fillers with higher G-prime values, as evidenced by significant volume reductions in such groups.

The Impact of Gel Parameters on the Dispersal and Fragmentation of Hyaluronic Acid Gel Fillers within an Artificial Model of Arterial Embolism

Accidental arterial embolization of hyaluronic acid (HA) fillers can lead to severe complications, including skin ischemia, blindness, and stroke. Currently, the intra-arterial dispersal and fragmentation behavior of HA gels is unknown but critical to our understanding of the pathomechanism of these injuries. This work introduces the Pulsatile Unit for the Laboratory Simulation of Arterio-embolic Restrictions (PULSAR) and evaluates the intravascular behavior of different HA gels. The fragmentation and dispersal behaviors of four HA gels with distinct rheological properties were evaluated via high-resolution videography and ImageJ particle size and morphology analysis. The gels' elastic modulus (G'), loss modulus (G″), tan(δ), and HA concentration were subsequently correlated with their intra-arterial behaviors. This study effectively confirms the extensive fragmentation of HA gels upon arterial inoculation, with particle sizes ranging from <50 µm to >1 mm. Gel particle size and morphology correlated most significantly with tan(δ). Conversely, arterial flow rates did not significantly influence gel fragmentation behavior, though the probability of proximal, macrovascular obstruction was affected. Overall, this study validates the PULSAR model for simulation of arterial dynamics and the testing of intravascular filler kinematics. The findings demonstrate the ability of gels to microfragment and disseminate distally, as well as induce partial proximal occlusion depending on gel rheology and arterial flow parameters.

Efficacy of a New Hyaluronic Acid Dermal Filler on Nasolabial Folds Correction: A Prospective, Comparative, Double-Blinded Clinical Trial

BACKGROUND

Hyaluronic acid-based dermal fillers are the cornerstones of wrinkle correction and facial contour redefinition.

OBJECTIVE

To assess the efficacy and safety of EST LF compared with RES L for the treatment of nasolabial folds (NLFs).

MATERIALS AND METHODS

In this prospective, split-face, randomized, investigator and subject-blinded trial, 45 subjects with moderate-to-severe symmetrical NLFs were randomized to EST LF on one side of the face and RES L on the other side and were followed up for 9 months. The primary end point was change in WSRS score from the baseline to Month 1 (M1). Secondary end points included changes in WSRS score at other time points, aesthetic improvement, wrinkle volume quantification, adverse events, and local tolerance.

RESULTS

The efficacy difference between EST LF and RES L at M1 was in favor of EST LF (-0.16, CI, -0.28 to -0.03]), demonstrating its noninferiority. Considering other time points, significant differences were observed at 3 and 6 months for EST LF , assessed with WSRS, GAIS, or NLF volume quantification. Both treatments were well tolerated.

CONCLUSION

EST LF is effective and well tolerated for the treatment of NLFs.

Efficacy Evaluation of a Hyaluronic Acid Dermal Filler Containing Mannitol: Clinical and Aesthetic Assessment Using High-Frequency Ultrasound

BACKGROUND

Mannitol may be a good excipient for hyaluronic acid (HA) filler.

OBJECTIVE

This study aimed to assess the tolerability and effectiveness of a mannitol-containing HA filler for the improvement of nasolabial folds (NLFs).

PATIENTS AND METHODS

Thirty Middle Eastern participants aged 18 to 65 years with moderate-to-severe NLFs on the Wrinkle Severity Rating Scale (WSRS) received 1 to 2 mL of a HA filler containing mannitol in both NLFs. Wrinkle Severity Rating Scale; volume, depth, and area of NLFs; and ultrasound parameters were measured at baseline, Weeks 2, 12, and 24 after the injection. Adverse events and participants' satisfaction were recorded in all follow-up visits.

RESULTS

Eighty-nine percent, 86%, and 61% of participants showed at least one grade improvement in WSRS, at Weeks 2, 12, and 24, respectively. The area and volume of NLFs significantly decreased compared with baseline (p-value < .01). In severe NLFs, echo density of the dermis significantly increased at Week 2. Participants reported great satisfaction with the treatment, and adverse events were mainly mild and transient. One patient had significant pain during injection, but this resolved without sequelae.

CONCLUSION

The tested mannitol-containing HA filler showed to be effective in Middle Eastern participants. The safety will require a follow-up larger study.

Stem Cell-Derived Extracellular Vesicle-Bearing Injectable Hydrogel for Collagen Generation in Dermis

Despite the remarkable advances of dermal fillers that reduce wrinkles caused by dermis thickness reduction, they still lack effective hydrogel systems that stimulate collagen generation along with injection convenience. Here, we develop a stem cell-derived extracellular vesicle (EV)-bearing thermosensitive hydrogel (EVTS-Gel) for effective in vivo collagen generation. The TS-Gel undergoes sol-gel transition at 32.6 °C, as demonstrated by the storage and loss moduli crossover. Moreover, the TS-Gel and the EVTS-Gel have comparable rheological properties. Both hydrogels are injected in a sol state; hence, they require lower injection forces than conventional hydrogel-based dermal fillers. When locally administered to mouse skin, the TS-Gel extends the retention time of EVs by 2.23 times. Based on the nature of the controlled EV release, the EVTS-Gel significantly inhibits the dermis thickness reduction caused by aging compared to the bare EV treatment for 24 weeks. After a single treatment, the collagen layer thickness of the EVTS-Gel-treated dermis becomes 2.64-fold thicker than that of the bare EV-treated dermis. Notably, the collagen generation efficacy of the bare EV is poorer than that of the EVTS-Gel of a 10× lesser dose. Overall, the EVTS-Gel shows potential as an antiaging dermal filler for in vivo collagen generation.

The bioengineering application of hyaluronic acid in tissue regeneration and repair

The multifaceted role of hyaluronic acid (HA) across diverse biomedical disciplines underscores its versatility in tissue regeneration and repair. HA hydrogels employ different crosslinking including chemical (chitosan, collagen), photo- initiation (riboflavin, LAP), enzymatic (HRP/H2O2), and physical interactions (hydrogen bonds, metal coordination). In biophysics and biochemistry, HA's signaling pathways, primarily through CD44 and RHAMM receptors, modulate cell behavior (cell migration; internalization of HA), inflammation, and wound healing. Particularly, smaller HA fragments stimulate inflammatory responses through toll-like receptors, impacting macrophages and cytokine expression. HA's implications in oncology highlight its involvement in tumor progression, metastasis, and treatment. Elevated HA in tumor stroma impacts apoptosis resistance and promotes tumor growth, presenting potential therapeutic targets to halt tumor progression. In orthopedics, HA's presence in synovial fluid aids in osteoarthritis management, as its supplementation alleviates pain, enhances synovial fluid's viscoelastic properties, and promotes cartilage integrity. In ophthalmology, HA's application in dry eye syndrome addresses symptoms by moisturizing the eyes, replenishing tear film deficiencies, and facilitating wound healing. Intravitreal injections and hydrogel-based systems offer versatile approaches for drug delivery and vitreous humor replacement. For skin regeneration and wound healing, HA hydrogel dressings exhibit exceptional properties by promoting moist wound healing and facilitating tissue repair. Integration of advanced regenerative tools like stem cells and solubilized amnion membranes into HA-based systems accelerates wound closure and tissue recovery. Overall, HA's unique properties and interactions render it a promising candidate across diverse biomedical domains, showcasing immense potentials in tissue regeneration and therapeutic interventions. Nevertheless, many detailed cellular and molecular mechanisms of HA and its applications remain unexplored and warrant further investigation.

The rheology of injectable hyaluronic acid hydrogels used as facial fillers: A review

Injectable hyaluronic acid (HA) hydrogels have been popularized in facial aesthetics as they provide a long-lasting effect, low risk of complications, allergenicity tests are not required before application and can be easily removed by the action of hyaluronidases. On the other hand, the development of these systems requires in-depth studies of chemical mechanisms involved in hydrogel formation. Ideal dermal fillers should temporarily fluidize during extrusion through the needle and quickly recover their original shape after application. Hydrogels with more elastic properties, for example, are difficult to inject while viscous materials are too liquid. A balance between both properties should be achieved. Each region of the face requires products with distinct rheological properties. High G' dermal fillers are preferable for deeper wrinkles whereas the counterpart with lower values of G' is more indicated in superficial wrinkles or lip augmentation. Factors such as molecular weight and concentration of HA, pH, type and concentration of the crosslinking agent, particle size, crosslinking reaction time and crosslinking agent/polysaccharide ratio should be modulated to achieve specific rheological properties. In this review, the effect of each variable is discussed in detail to guide the rational development of new dermal fillers.

Nonsurgical Gluteal Volume Correction with Hyaluronic Acid: A Retrospective Study to Assess Long-term Safety and Efficacy

Background

Augmentation and reshaping of body volume, particularly in the gluteal area, presents a significant challenge in aesthetic surgery. Hyaluronic acid (HA) fillers have emerged as an effective and safe tool for such indications, but literature examining nonsurgical gluteal reshaping with HA remains limited. This study aims to evaluate the long-term safety of using recommended volumes of HA body fillers for nonsurgical gluteal augmentation.

Methods

A retrospective, observational study was carried out across multiple centers in Italy and the United Arab Emirates. The study involved participants between 22 and 53 years of age who underwent gluteal augmentation using HA body filler (HYAcorp MLF1/2) between 2017 and 2021, with up to 4 years and 7 months of follow-up. Participants and investigators independently evaluated the procedure's effectiveness by comparing pre- and posttreatment photographs. The Global Aesthetic Improvement Scale was used to assess posttreatment satisfaction by both participants and investigators. All adverse effects (AEs) were recorded.

Results

The study included a diverse group of 91 participants. No serious adverse events were reported, with the majority of AE occurring shortly after treatment and resolving in 1 week. AEs were more frequently observed in participants with previous treatments using different substances in the treatment area.

Conclusions

The real-world application of HA body filler (HYAcorp MLF1/2) for gluteal augmentation in the participants of this study showed the treatment's effectiveness, with no severe adverse events reported among the participants. High levels of satisfaction were reported among both participants and investigators.

Effectiveness and Safety of Resilient Hyaluronic Acid (RHA) Dermal Fillers for the Correction of Moderate-to-Severe Nasolabial Folds in People of Color: Post Hoc Subgroup Analyses of US Pivotal Clinical Data

BACKGROUND

People of color (POC) are often underrepresented in clinical studies evaluating the safety and effectiveness of aesthetic products, including hyaluronic acid (HA) fillers, for which there is to date limited clinical data in POC.

OBJECTIVES

The aim of this study was to assess the safety and effectiveness of a new line of dynamic resilient HA fillers (RHA; Revance, Nashville, TN) for treating moderate-to-severe nasolabial folds (NLFs) in POC vs non-POC.

METHODS

Post hoc subgroup analyses compared the efficacy and safety of POC vs non-POC subjects treated with RHA2, RHA3, or RHA4 for correction of moderate-to-severe NLFs in the pooled per-protocol population (N = 217) in 2 clinical trials. Evaluated population cohorts were classified by Fitzpatrick skin type (FST) (high FST [IV-VI] vs low FST [I-III]) and by subject-reported race (non-White vs White) relative to baseline at 6, 9, 12, and 15 months.

RESULTS

POC consistently showed greater improvement in wrinkle severity and higher responder rates compared with non-POC, which reached statistical significance at several measured time points. Global Aesthetic Improvement Scale scores and subject satisfaction ratings were similar for POC and non-POC and remained high throughout the course of the study. Treatment-related adverse event rates were generally lower for high FSTs vs low FSTs, with no reported cases of keloidal scarring.

CONCLUSION

The RHA line of dynamic fillers is well tolerated and effective for the correction of moderate-to-severe NLFs in POC and can be confidently used in this important and growing patient population.See the abstract translated into Hindi, Portuguese, Korean, German, Italian, Arabic, Chinese, and Taiwanese online here: https://doi.org/10.1093/asj/sjad251.

LEVEL OF EVIDENCE: 2

Highly Concentrated Stabilized Hybrid Complexes of Hyaluronic Acid: Rheological and Biological Assessment of Compatibility with Adipose Tissue and Derived Stromal Cells towards Regenerative Medicine

Cells and extracts derived from adipose tissue are gaining increasing attention not only in plastic surgery and for aesthetic purposes but also in regenerative medicine. The ability of hyaluronan (HA) to support human adipose stromal cell (hASC) viability and differentiation has been investigated. However, the compatibility of adipose tissue with HA-based formulation in terms of biophysical and rheological properties has not been fully addressed, although it is a key feature for tissue integration and in vivo performance. In this study, the biophysical and biochemical properties of highly concentrated (45 mg/mL) high/low-molecular-weight HA hybrid cooperative complex were assessed with a further focus on the potential application in adipose tissue augmentation/regeneration. Specifically, HA hybrid complex rheological behavior was observed in combination with different adipose tissue ratios, and hyaluronidase-catalyzed degradation was compared to that of a high-molecular-weight HA (HHA). Moreover, the HA hybrid complex's ability to induce in vitro hASCs differentiation towards adipose phenotype was evaluated in comparison to HHA, performing Oil Red O staining and analyzing gene/protein expression of PPAR-γ, adiponectin, and leptin. Both treatments supported hASCs differentiation, with the HA hybrid complex showing better results. These outcomes may open new frontiers in regenerative medicine, supporting the injection of highly concentrated hybrid formulations in fat compartments, eventually enhancing residing staminal cell differentiation and improving cell/growth factor persistence towards tissue regeneration districts.

Adverse Events Associated with Hyaluronic Acid Filler Injection for Non-surgical Facial Aesthetics: A Systematic Review of High Level of Evidence Studies

BACKGROUND

Hyaluronic acid (HA) dermal fillers are widely used in aesthetic medicine. While generally safe, potential complications can arise.

OBJECTIVE

This systematic review aims to identify and classify potential complications linked to the use of HA dermal fillers, as informed by high-quality, low-risk-of-bias studies.

METHODS

This review follows the Cochrane review standards for clinical systematic reviews. This systematic review analyzed 48 high level of evidence studies on the use of hyaluronic acid (HA) dermal fillers in non-surgical facial aesthetics and the adverse events that occurred.The inclusion criteria were randomized control studies on HA dermal fillers and their complications. Excluded were case reports, case series, observational studies, and other non-randomized research due to their inability to provide generalized conclusions and their inherent publication bias.

RESULTS

Adverse events were classified into three categories: expected reactions, product or technique-related adverse events, and severe adverse events. Most adverse events were short-lived injection site reactions, which resolved spontaneously. Specific HA fillers and injection techniques influenced the occurrence of adverse events, which generally resolved within weeks without treatment. Severe adverse events were rare, persisting for months and requiring active medical intervention.

DISCUSSION

This classification system can enhance understanding, prevention, and treatment of HA filler complications, and support patient education. The common complications were injection site reactions, with persistent symptoms treated with topical steroids, NSAIDs, or hyaluronidase. Severe complications included severe edema, angioedema and others, often necessitating specific treatments.

CONCLUSION

HA dermal fillers are generally safe and effective, with most adverse events being transient and mild to moderate in severity. Severe adverse events, although rare, do occur and are generally non-treatment related. Informed consent, patient education, and professional training are crucial for safe and successful outcomes. Level of Evidence II This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Evaluation of the Hydrophilic, Cohesive, and Physical Properties of Eight Hyaluronic Acid Fillers: Clinical Implications of Gel Differentiation

Background

Hyaluronic acid (HA) fillers are used to treat an array of aesthetic indications. Proper filler selection is paramount for successful patient outcomes. However, many important physiochemical and physical properties that impact HA gel behavior remain undefined.

Purpose

To evaluate the hydrophilicity, cohesivity and particle size of eight commercial HA fillers manufactured by either Non-Animal Stabilized Hyaluronic Acid (NASHA) or Optimal Balance Technology (OBT) techniques.

Methods and Materials

Three individual in vitro experiments were performed to assess HA swelling capacity, cohesion, and particle size. Image analyses, blinded evaluation using the Gavard-Sundaram Cohesivity Scale, and laser diffraction technology were utilized, respectively.

Results

Compared to fillers manufactured with NASHA technology, OBT products demonstrated greater swelling capacity, cohesion, and wider particle size distributions. Strong positive correlations between swelling factor, degree of cohesivity, and increasing widths of the particle size distributions were observed.

Conclusions

The hydrophilicity, cohesivity and particle size distributions vary among HA fillers manufactured with different techniques. The creation of new labels identifying products based on their unique combination of physiochemical and physical characteristics may help guide appropriate selection of HA fillers to optimize patient outcomes.

The third generation barbed lifting threads: Added value of hyaluronic acid

INTRODUCTION

Facial thread lifting is a highly demanded procedure in esthetic clinics worldwide. The aim of this retrospective study is to evaluate the clinical effectiveness and overall patients' satisfaction of a new generation of barbed threads, in which a hyaluronic acid (HA) coat was added to the PLLA/PCL threads and compare the results with PLLA/PCL threads without HA.

MATERIALS AND METHODS

Twenty patients treated with the PLLA/PCL threads with or without hyaluronic acid (HA) were compared for FaceQ scales: Age appraisal, psychological function, skin satisfaction, satisfaction with facial appearance, appraisal lines of nasolabial folds, satisfaction of lower face, and jaw were compared at baseline, 4 and 12 months post-treatment. Early impact on life and the skin adverse effects were assessed 1 week post-treatment. Finally, patients and two physicians provided the GAIS score at 4 and 12 months and a comparison was made between the two groups.

RESULTS

There was a statistically significant improvement in all scales of FaceQ for all included patients at baseline and at 4 and 12 months post-treatment. Importantly, there were less skin-related adverse effects such as skin redness, uneven tone, irregular surface, burning, and itching sensation at a recovery period (1 week post-treatment) in the group receiving HA-containing threads.

CONCLUSION

A notably higher long-term improvement in aging appearance, satisfaction with face appearance, lower jaw and face as well as GAIS was seen in the group treated with HA-containing threads compared to the other treatment arm.

Implications for cumulative and prolonged clinical improvement induced by cross-linked hyaluronic acid: An in vivo biochemical/microscopic study in humans

In photoaged human skin, type I collagen fragmentation impairs dermal extracellular matrix (ECM) integrity, resulting in collapsed/contracted fibroblasts with reduced type I procollagen synthesis. Injections of cross-linked hyaluronic acid (CL-HA) reverse these deleterious changes. To investigate the time course and effects of biochemical changes induced by injected CL-HA, particularly whether fibroblast activation leads to accumulation/deposition of dermal collagen, we injected CL-HA into photoaged skin of human participants over 60 years-old and performed biochemical/microscopic analyses of skin samples. Beginning 1 week post-injection and lasting 6-9 months, fibroblasts exhibited activation, including increased immunostaining and gene expression of markers of type I collagen synthesis, such as heat shock protein 47 and components of the transforming growth factor-β pathway. At 1 week post-injection, multiphoton microscopy revealed elongation/stretching of fibroblasts, indicating enhanced dermal mechanical support. At 4 weeks, second-harmonic generation microscopy revealed thick collagen bundles densely packed around pools of injected CL-HA. At 12 months, accumulation of thick collagen bundles was observed and injected CL-HA remained present in substantial amounts. Thus, by occupying space in the dermal ECM, injected CL-HA rapidly and durably enhances mechanical support, stimulating fibroblast elongation and activation, which results in thick, densely packed type I collagen bundles accumulating as early as 4 weeks post-injection and continuing for at least a year. These observations indicate that early and prolonged clinical improvement following CL-HA injection results from space-filling and collagen deposition. As type I collagen has an estimated half-life of 15 years, our data provide the foundations for optimizing the timing/frequency of repeat CL-HA injections.

3D printed scaffolds based on hyaluronic acid bioinks for tissue engineering: a review

Hyaluronic acid (HA) is widely distributed in human connective tissue, and its unique biological and physicochemical properties and ability to facilitate biological structure repair make it a promising candidate for three-dimensional (3D) bioprinting in the field of tissue regeneration and biomedical engineering. Moreover, HA is an ideal raw material for bioinks in tissue engineering because of its histocompatibility, non-immunogenicity, biodegradability, anti-inflammatory properties, anti-angiogenic properties, and modifiability. Tissue engineering is a multidisciplinary field focusing on in vitro reconstructions of mammalian tissues, such as cartilage tissue engineering, neural tissue engineering, skin tissue engineering, and other areas that require further clinical applications. In this review, we first describe the modification methods, cross-linking methods, and bioprinting strategies for HA and its derivatives as bioinks and then critically discuss the strengths, shortcomings, and feasibility of each method. Subsequently, we reviewed the practical clinical applications and outcomes of HA bioink in 3D bioprinting. Finally, we describe the challenges and opportunities in the development of HA bioink to provide further research references and insights.

An experimental study of the vascular embolism caused by recombinant type III collagen implants and hyaluronic acid

BACKGROUND

There are significant differences in the reported incidence of vascular complications that result from the injection of different soft tissue fillers. This study aimed to compare the risk of vascular embolism after recombinant type III collagen implants and hyaluronic acid (HA) injection into arteries.

METHODS

Different concentrations of recombinant type III collagen and Restylane were injected into the central ear artery of rabbits, to construct an immediate embolization model. We screened for vascular recanalization and tissue necrosis at 30 min, 1 day, and 7 days after injection, and histopathology examination was processed on Day 7.

RESULTS

At 30 min after injection, complete recanalization of the central ear artery was observed in 17 rabbits in the C1 group while none in the HA group. On Day 1 after injection, complete recanalization of the CEA main trunk was observed in all rabbits in the collagen group while 50% in the HA group. There was a significant difference between the C1 group and the HA group in terms of vascular recanalization and skin necrosis.

CONCLUSION

Under the present experimental conditions, the risk of causing vascular embolism was much lower with collagen than with Restylane. Different doses of collagen at different injection rates have the same safety profile.

Investigation of Crosslinking Parameters and Characterization of Hyaluronic Acid Dermal Fillers: From Design to Product Performances

Despite process similarities, distinctive manufacturing technologies offer hyaluronic acid dermal fillers with different in vitro physicochemical and rheological properties due to peculiar crosslinked hydrogel networks. A better understanding of dermal filler properties could provide specific clinical indications and expectations with more accurate performance correlations. In this study, with an emphasis on the degree of modification, hyaluronic acid concentration and molecular weight, these process parameters were able to modulate dermal filler properties, especially rheology. Moreover, an extensive characterization of commercial hyaluronic acid injectables of the Hyal System line was described to present product properties and help to elucidate related clinical effects. Standardized methodologies were applied to correlate in vitro parameters with feasible clinical indications. In view of an optimized dermal filler design, the results of the extrudability measurements allowed the quantification of the effect of hydrogel composition, rheological properties and needle size on injectability. Composition, dynamic viscosity and needle size showed an impactful influence on hydrogel extrudability. Finally, the positive influence of 200 KDa hyaluronic acid in comparison to fragments of ether-crosslinked hyaluronic acid on fibroblast recognition were shown with a migration assay.

Long-Term Efficacy and Tolerability of a Medium G' HA Filler with Tri-Hyal Technology on the Rejuvenation of the Mobile Facial Zone

Purpose

Injectable hyaluronic acid-based fillers are commonly used for the correction of skin contour irregularities and to smooth skin depressions formed by volume loss during the aging process. These fillers are particularly efficient to restore perioral skin depressions/wrinkles or to correct topographical anomalies. The European directives require a continuous evaluation of the performance of these medical devices, particularly for CE marked products.

Methods

An 18-month prospective randomized single-blind study for the efficacy and safety of ART FILLER Universal (AFU) was performed on the lips, the nasolabial folds, and the marionettes lines. The evaluations were performed on 153 subjects enrolled in this study. The efficacy, the longevity, and the safety were evaluated for the injected areas via area specific clinical scoring after a single injection with the filler and with no re-touch.

Results

We showed here that filler injection induced potent improvements of volume restoration after a single injection on all the treated areas. These beneficial properties of the filler were significant 3 weeks after injection and during the whole study period. Moreover, injections of the filler were well tolerated by the subjects. The recorded adverse events are routinely seen with HA fillers for face volume corrections, and most of these local reactions resolved within 14 days.

Conclusion

AFU was well tolerated and showed a continuous efficacy for at least 18 months, in exploratory analyses.

Hyaluronic Acid Basics and Rheology

Hyaluronic acid (HA) is the most common dermal filler in use. It improves wrinkles and volume loss not only by filling and volumizing but also by hydrating the injected area with its water affinity. It is a naturally occurring component of skin, and there is a negligible risk of immunologic or allergic reaction with injection. It is rapidly degraded by the injection of hyaluronidase, thus creating an ideal injectable material that is low risk and reversible. Its duration of effect may be longer than expected based on bioavailability of the HA product due to collagen synthesis or fibroblast stimulation.

The Intrinsic Relation between the Hydrogel Structure and In Vivo Performance of Hyaluronic Acid Dermal Fillers: A Comparative Study of Four Typical Dermal Fillers

BACKGROUND

Hyaluronic acid dermal fillers are composed of cross-linked viscoelastic particles with high biocompatibility. The performance of the fillers is determined by the viscoelastic properties of particles and the connecting force between particles. However, the relationships among the properties of fillers, the interaction of the gels and the surrounding tissue are not clear enough.

METHOD

Four kinds of typical dermal filler were selected in this research to reveal the interaction between the gels and cells. A series of analytical tools was applied to characterize the structure and physicochemical properties of the gel, as well as observing their interaction with the surrounding tissues in vivo and discussing their internal mechanism.

RESULT

The large particles internal the gel and the high rheological properties endow the Restylane2 with excellent support. However, these large-size particles have a significant impact on the metabolism of the local tissue surrounding the gel. Juvéderm3 present gel integrity with the high cohesiveness and superior support. The rational matching of large and small particles provides the Juvéderm3 with supporting capacity and excellent biological performance. Ifresh is characterized by small-size particles, moderate cohesiveness, good integrity, lower viscoelasticity and the superior cellular activity located the surrounding tissues. Cryohyaluron has high cohesion and medium particle size and it is prominent in cell behaviors involving localized tissues. Specific macroporous structure in the gel may facilitate the nutrients delivering and removing the waste.

CONCLUSION

It's necessary to make the filler both sufficient support and biocompatibility through the rational matching of particle sizes and rheological properties. Gels with macroporous structured particle showed an advantage in this area by providing a space inside the particle.

Precision of Soft-Tissue Filler Injections: An Ultrasound-Based Verification Study

BACKGROUND

Uncontrolled product spread is an important issue to consider in facial filler injections. Lack of precision can result in reduced effectiveness and surface projection, as well as irregularities and product visibility.

OBJECTIVES

The authors sought to assess the precision of soft-tissue filler injections in the face by employing a cannula.

METHODS

This single-center observational study investigated soft-tissue filler distribution utilizing real-time non-invasive ultrasound imaging. Outcome parameters included (1) the tissue plane of product distribution, (2) the extent of horizontal as well as vertical product spread at the injection site, and (3) the product surface area taking into account the multifactorial influence of several independent variables. Participants were followed up to 30 days post-injection.

RESULTS

A total 100 facial injections were performed in 8 patients (2 males, 6 females) with a mean age of 37.20 (±6.34) years and a mean BMI of 22.21 (±1.39) kg/m.2. The plane of product distribution remained constant in approximately 90% of cases at day 0 (d0), d14, and d30. Mean horizontal product spread was higher compared with vertical spread, and both significantly decreased over all time points (P < .001). Mean product surface area was 22.51 ± 16.34 mm2 at d0, 15.97 ± 11.28 mm2 at d14, and 12.9 ± 9.15 mm2 at d30. Analysis employing generalized linear models revealed that injection volume and injection depth significantly influenced product surface area.

CONCLUSIONS

Injection of soft-tissue filler employing a cannula allows precise application of the product within the intended tissue plane. Precision can be improved by injecting less product into deeper tissue layers.

LEVEL OF EVIDENCE: 5

Granular Disulfide-Crosslinked Hyaluronic Hydrogels: A Systematic Study of Reaction Conditions on Thiol Substitution and Injectability Parameters

Granular polymer hydrogels based on dynamic covalent bonds are attracting a great deal of interest for the design of injectable biomaterials. Such materials generally exhibit shear-thinning behavior and properties of self-healing/recovery after the extrusion that can be modulated through the interactions between gel microparticles. Herein, bulk macro-hydrogels based on thiolated-hyaluronic acid were produced by disulphide bond formation using oxygen as oxidant at physiological conditions and gelation kinetics were monitored. Three different thiol substitution degrees (SD%: 65%, 30% and 10%) were selected for hydrogel formation and fully characterized as to their stability in physiological medium and morphology. Then, extrusion fragmentation technique was applied to obtain hyaluronic acid microgels with dynamic disulphide bonds that were subsequently sterilized by autoclaving. The resulting granular hyaluronic hydrogels were able to form stable filaments when extruded through a syringe. Rheological characterization and cytotoxicity tests allowed to assess the potential of these materials as injectable biomaterials. The application of extrusion fragmentation for the formation of granular hyaluronic hydrogels and the understanding of the relation between the autoclaving processes and the resulting particle size and rheological properties should expand the development of injectable materials for biomedical applications.

Non-Surgical Management of the Gingival Smile with Botulinum Toxin A-A Systematic Review and Meta-Analysis

Currently, concern about facial attractiveness is increasing, and this fact has led to orthodontics in adult patients being an increasingly demanded treatment, and with it, multi-disciplinary work. When it is caused by a vertical excess of the maxilla, the ideal solution is orthognathic surgery. However, in borderline cases and when the cause is hyperactivity of the upper lip levator muscle complex, alternative conservative solutions can be considered, such as the application of botulinum toxin A (BTX-A). Botulinum toxin is a protein produced by a bacterium and causes a reduction in the force of muscle contraction. The multi-factorial nature of the smile requires an individualized diagnosis in each patient, since there are multiple ways to treat the gummy smile (orthognathic surgery, gingivoplasty, orthodontic intrusion). In recent years, interest has grown in the simplest techniques that allow the patient to quickly return to their usual routine, such as lip replacement. However, this procedure shows recurrences in the first 6-8 post-operative weeks. The main objective of this systematic review and meta-analysis is to analyze the effectiveness of BTX-A in the treatment of gummy smile in the short term, to study its stability, and to evaluate potential complications. A thorough search of the PubMed, Scopus, Embase, Web of Science, and Cochrane databases and a grey literature search were conducted. The inclusion criteria were studies with a sample size greater than or equal to 10 patients with gingival exposure greater than 2 mm in smile, treated with BTX-A infiltration. Those patients whose exclusive etiology of their gummy smile was related to altered passive eruption, gingival thickening, or overeruption of upper incisors were excluded. In the qualitative analysis, the mean pre-treatment gingival exposure ranged between 3.5 and 7.2 mm, reaching a reduction of up to 6 mm after infiltration with botulinum toxin at 12 weeks. Although multiple muscles are involved in the facial expression, the muscles par excellence selected for blockade with BTX-A were levator labii superioris, levator labii superioris ala nasalis, and zygomaticus minor, infiltrating from 1.25 to 7.5 units per side. In the quantitative analysis, the difference in mean reduction between both groups was -2.51 mm at two weeks and -2.24 mm at three months. The benefit of BTX-A in terms of improvement of gummy smile is demonstrated, as a significant reduction in gummy smile is estimated by BTX-A therapy two weeks after its application. Its results gradually decrease over time, however, they stay satisfactory without returning to their initial values after 12 weeks.

Synthesis and Characterization of Hierarchical Zeolites Modified with Polysaccharides and Its Potential Role as a Platform for Drug Delivery

Hierarchical zeolites are aluminosilicates with a crystal structure, which next to the micropores possess secondary porosity in the range of mesopores and/or small macropores. Due to their ordered structure and additional secondary porosity, they have aroused great interest among scientists in recent years. Therefore, the present work concerns the synthesis and characterization of hierarchical zeolites with secondary mesoporosity, based on commercial zeolites such as MFI (ZSM-5), BEA (β) and FAU (Y), and modified with polysaccharides such as inulin, hyaluronic acid, and heparin. All materials were characterized by various analytical techniques and applied as a platform for delivery of selected drug molecules. On the basis of X-ray diffraction (presence of reflections in the 2θ angle range of 1.5-2.5°) and low-temperature nitrogen sorption isotherms (mixture of isotherms of I and IV type) additional secondary porosity was found in the mesopore range. Additional tests were also conducted to determine the possibility of loading selected molecules with biological activity into the aforementioned materials and then releasing them in the therapeutic process. Molecules with different therapeutic options were selected for testing, namely ibuprofen, curcumin, and ferulic acid with anti-inflammatory, potentially anticancer, antioxidant, and skin discoloration activities, respectively. Preliminary studies have confirmed the possibility of using hierarchical zeolites as potential carriers for bioactive molecules, as the loading percentage of active substances ranged from 39-79% and cumulative release for ibuprofen reached almost 100% after 8 h of testing.

A prospective multicenter clinical trial evaluating the efficacy and safety of a hyaluronic acid-based filler with Tri-Hyal technology in the treatment of lips and the perioral area

BACKGROUND

Age-related changes of facial soft tissue cause clinical signs of facial aging such as lip atrophy, marionette lines, and an accentuated nasolabial fold. These changes can be modified using dermal fillers.

AIMS

To evaluate efficacy, longevity, and safety of a cross-linked hyaluronic acid-based filler with Tri-Hyal technology in the treatment of lips, nasolabial folds, and marionette lines.

MATERIALS AND METHODS

This prospective, multi-center trial evaluated injections of three different areas (lips, nasolabial fold alone, or with marionette wrinkles) with a soft tissue filler containing 25 mg/ml cross-linked hyaluronic acid and 0.3% lidocaine. Primary endpoint was the aesthetic correction 3 weeks after one injection session without touch-up. Follow-up was 18 months. Assessments were performed using the Global Aesthetic Score (GAS), clinical scoring based on photographic scales, high-frequency ultrasound imaging, and the Global Aesthetic Improvement Scale (GAIS).

RESULTS

In total, 100 subjects were injected. GAS improved significantly for all treatment indications at 3 weeks (p < 0.0001). Success rates were highest for nasolabial folds (98.4%), followed by marionette lines (94.4%) and lips (73.5%). After 18 months post-injection, success was observed in 91%, 88%, and 33% of subjects injected into nasolabial folds, marionette lines, and lips, respectively. GAIS scored highest for nasolabial folds (SGAIS: 71%; IGAIS: 40%), followed by marionette lines (SGAIS: 56%; IGAIS: 33%) and lips (SGAIS: 30%; IGAIS: 22%) at 18 months follow-up.

CONCLUSIONS

The filler demonstrated high efficacy and safety in all indications. Regional differences in longevity were evident. Thus, the necessity of regional retreatments should be discussed with patients before injection.

Evaluation of the Performance and Tolerance of the Combination of an HA-based Filler with Tri-Hyal Technology and a Skin Biorevitalizer on Skin Aging Parameters

Background

Biorevitalization solutions contain numerous nutritive compounds to improve skin quality. Dermal fillers like HA (hyaluronic acid), depending on rheological characteristics, are used to fill large static defaults with a sustained long-term efficacy. Treatments with either dermal filler or biorevitalization solutions alone are not enough to bring a global facial aging approach.

Objective

To demonstrate the anti-aging performance and safety of a new protocol, BIONUTRILIFT, which combined an HA-based filler with Tri-Hyal technology and a skin biorevitalizer, to target the skin quality and wrinkles correction at the same time.

Materials and Methods

Eligible subjects were enrolled based on a score of 2, 3, 4, or 5 on Bazin cheek folds wrinkle scale. Safety outcomes measured were immediate and local tolerability. Performance outcomes measured included: proportion of subjects in whom the severity of cheeks folds, nasolabial folds, marionette lines, upper lip wrinkles and skin radiance remained at least one point below the baseline measurement (Bazin scale) Global Aesthetic Improvement Scale scores by subjects and investigators.

Results

In performance analyses with the combined protocol, skin radiance and cheek folds wrinkle correction sustained during the four-month study and decrease by 61% and 55%, respectively. 96% and 77% of subjects respectively showed at least a one-point decrease in the mean skin radiance score and Bazin score compared with baseline. Interestingly, the BIONUTRILIFT protocol showed the distance effect of vector A (cheek injection) and vector B (mandibular injection) on perioral zone and remained significant even 120 days after injections. Adverse events (AEs) were consistent with the expected AEsthat occurred after dermal injections. No serious AEswere recorded.

Conclusion

BIONUTRILIFT may satisfy the subjects' demand by obtaining in the same session a simple, personalized, noninvasive, atraumatic, and reproductible technique.

Oxidized hyaluronic acid/adipic acid dihydrazide hydrogel as cell microcarriers for tissue regeneration applications

Hyaluronic acid (HA) is a biopolymer present in various human tissues, whose degradation causes tissue damage and diseases. The oxidized hyaluronic acid/adipic acid dihydrazide (oxi-HA/ADH) hydrogels have attracted attention due to their advantages such as thermosensitivity, injectability, in situ gelation, and sterilization. However, studies are still scarce in the literature as microcarriers. In that sense, this work is a study of oxi-HA/ADH microparticles of 215.6 ± 2.7 µm obtained by high-speed shearing (18,000 rpm at pH 7) as cell microcarriers. Results showed that BALB/c 3T3 fibroblasts and adipose mesenchymal stem cells (h-AdMSC) cultured on the oxi-HA/ADH microcarriers presented a higher growth of both cells in comparison with the hydrogel. Moreover, the extrusion force of oxi-HA/ADH microparticles was reduced by 35% and 55% with the addition of 25% and 75% HA fluid, respectively, thus improving its injectability. These results showed that oxi-HA/ADH microcarriers can be a potential injectable biopolymer for tissue regeneration applications.

Hyaluronic Acid in Biomedical Fields: New Trends from Chemistry to Biomaterial Applications

The aim of this review is to give an updated perspective about the methods for chemical modifications of hyaluronic acid (HA) toward the development of new applications in medical devices and material engineering. After a brief introduction on chemical, structural and biological features of this important natural polysaccharide, the most important methods for chemical and physical modifications are disclosed, discussing both on the formation of new covalent bonds and the interaction with other natural polysaccharides. These strategies are of paramount importance in the production of new medical devices and materials with improved properties. In particular, the use of HA in the development of new materials by means of additive manufacturing techniques as electro fluid dynamics, i.e., electrospinning for micro to nanofibres, and three-dimensional bioprinting is also discussed.

The Rheology and Physicochemical Characteristics of Hyaluronic Acid Fillers: Their Clinical Implications

Hyaluronic acid (HA) fillers have become the most popular material for facial volume augmentation and wrinkle correction. Several filler brands are currently on the market all around the world and their features are extremely variable; for this reason, most users are unaware of their differences. The study of filler rheology has become a wellspring of knowledge, differentiating HA fillers, although these properties are not described thoroughly by the manufacturers. The authors of this review describe the more useful rheological properties that can help clinicians understand filler characteristics and the likely correlation of these features with clinical outcomes.

Sticking Together: Injectable Granular Hydrogels with Increased Functionality via Dynamic Covalent Inter-Particle Crosslinking

Granular hydrogels are an exciting class of microporous and injectable biomaterials that are being explored for many biomedical applications, including regenerative medicine, 3D printing, and drug delivery. Granular hydrogels often possess low mechanical moduli and lack structural integrity due to weak physical interactions between microgels. This has been addressed through covalent inter-particle crosslinking; however, covalent crosslinking often occurs through temporal enzymatic methods or photoinitiated reactions, which may limit injectability and material processing. To address this, a hyaluronic acid (HA) granular hydrogel is developed with dynamic covalent (hydrazone) inter-particle crosslinks. Extrusion fragmentation is used to fabricate microgels from photocrosslinkable norbornene-modified HA, additionally modified with either aldehyde or hydrazide groups. Aldehyde and hydrazide-containing microgels are mixed and jammed to form adhesive granular hydrogels. These granular hydrogels possess enhanced mechanical integrity and shape stability over controls due to the covalent inter-particle bonds, while maintaining injectability due to the dynamic hydrazone bonds. The adhesive granular hydrogels are applied to 3D printing, which allows the printing of structures that are stable without any further post-processing. Additionally, the authors demonstrate that adhesive granular hydrogels allow for cell invasion in vitro. Overall, this work demonstrates the use of dynamic covalent inter-particle crosslinking to enhance injectable granular hydrogels.

Bridging a Century-Old Problem: The Pathophysiology and Molecular Mechanisms of HA Filler-Induced Vascular Occlusion (FIVO)-Implications for Therapeutic Interventions

Biocompatible hyaluronic acid (HA, hyaluronan) gel implants have altered the therapeutic landscape of surgery and medicine, fostering an array of innovative products that include viscosurgical aids, synovial supplements, and drug-eluting nanomaterials. However, it is perhaps the explosive growth in the cosmetic applications of injectable dermal fillers that has captured the brightest spotlight, emerging as the dominant modality in plastic surgery and aesthetic medicine. The popularity surge with which injectable HA fillers have risen to in vogue status has also brought a concomitant increase in the incidence of once-rare iatrogenic vaso-occlusive injuries ranging from disfiguring facial skin necrosis to disabling neuro-ophthalmological sequelae. As our understanding of the pathophysiology of these injuries has evolved, supplemented by more than a century of astute observations, the formulation of novel therapeutic and preventative strategies has permitted the amelioration of this burdensome complication. In this special issue article, we review the relevant mechanisms underlying HA filler-induced vascular occlusion (FIVO), with particular emphasis on the rheo-mechanical aspects of vascular blockade; the thromboembolic potential of HA mixtures; and the tissue-specific ischemic susceptibility of microvascular networks, which leads to underperfusion, hypoxia, and ultimate injury. In addition, recent therapeutic advances and novel considerations on the prevention and management of muco-cutaneous and neuro-ophthalmological complications are examined.

Lip Lifting Efficacy of Hyaluronic Acid Filler Injections: A Quantitative Assessment Using 3-Dimensional Photography

The study aimed to compare the volume enhancement and the lifting capacity of two different hyaluronic acid gels for lip injection. Thirty-six Korean female patients were randomized into two groups according to the cross-linking degree of the hyaluronic acid filler injected. Using a fixed injection protocol, patients were injected with 1 mL of hyaluronic acid filler in the lips and followed up at four and 12 weeks after injection. Lip volume, lip projection, and columella–labial angle were measured using a 3-dimensional imaging system at each time point. Follow-up values were compared with baseline. Compared with pre-treatment values, there was a statistically significant increase in mean lip volume and lip projection at four and 12 weeks after injection, with no significant differences between the two groups. Lips injected with hyaluronic acid filler of intermediate cross-link density resulted in more acute angles than lips injected with lightly cross-linked hyaluronic acid. The difference was statistically significant at each follow-up time point. No serious complications were observed throughout the study period. Our results imply that in patients who want a prominent upper lip lift, lip injections using hyaluronic acid fillers with intermediate cross-linking density can be a good option due to their lift capacity. The degree of cross-linking may not be a significant determinant of simple lip volume augmentation when other variables are constant.

Quantitative Evaluation of Volume Augmentation and Durational Changes in the Anteromedial Cheek with Hyaluronic Acid Fillers Using Three-Dimensional Measurement: 2-Year Results from a Comparative Split-Face Study

SUMMARY

Hyaluronic acid fillers are widely used for the augmentation of facial soft tissues. Hyaluronic acid fillers can be monophasic or biphasic and have different characteristics, especially regarding volumetric effects and maintenance potential. However, there is paucity of long-term quantitative and objective data on clinical outcomes following hyaluronic acid injection. In this study, the authors evaluated volumetric changes over 2 years and the maintenance potentials of both types of fillers on the anteromedial cheek using objective three-dimensional measurements. This comparative split-face study enrolled participants aged 30 to 50 years who received a midfacial injection of the test filler (Belotero Volume) on one side and a random control filler (Juvéderm, Restylane SubQ, or Yvoire Contour) on the contralateral side. The authors conducted three-dimensional scanning assessments at baseline and after 30 minutes; 3 days; 2, 4, 12, and 24 weeks; and 2 years. The volume augmentation effects for the anteromedial cheek of two monophasic fillers (Belotero Volume and Juvéderm Voluma) were maintained for at least 2 years (81 percent and 66 percent, respectively, compared to the volume at 4 weeks). Two biphasic fillers (Yvoire Contour and Restylane SubQ) maintained over 50 percent volume compared to the volume 4 weeks after injection. Monophasic fillers showed better outcomes than biphasic fillers; however, both types of hyaluronic acid fillers demonstrated superior efficacy, safety, and durability for volumetric augmentation in the anteromedial cheek. Objective data obtained using three-dimensional imaging analysis will enable dermatologists to better demonstrate the results of the procedure to patients, through the provision of visual aids.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, II.

Hyaluronan Hydrogels: Rheology and Stability in Relation to the Type/Level of Biopolymer Chemical Modification

BDDE (1,4-butanediol-diglycidylether)-crosslinked hyaluronan (HA) hydrogels are widely used for dermo-aesthetic purposes. The rheology and stability of the gels under physiological conditions greatly affect their clinical indications and outcomes. To date, no studies investigating how these features are related to the chemistry of the polymeric network have been reported. Here, four available HA-BDDE hydrogels were studied to determine how and to what extent their rheology and stability with respect to enzymatic hydrolysis relate to the type and degree of HA structural modification. ¹H-/¹³C-NMR analyses were associated for the quantification of the “true” HA chemical derivatization level, discriminating between HA that was effectively crosslinked by BDDE, and branched HA with BDDE that was anchored on one side. The rheology was measured conventionally and during hydration in a physiological medium. Sensitivity to bovine testicular hyaluronidase was quantified. The correlation between NMR data and gel rheology/stability was evaluated. The study indicated that (1) the gels greatly differed in the amounts of branched, crosslinked, and overall modified HA, with most of the HA being branched; (2) unexpectedly, the conventionally measured rheological properties did not correlate with the chemical data; (3) the gels’ ranking in terms of rheology was greatly affected by hydration; (4) the rheology of the hydrated gels was quantitatively correlated with the amount of crosslinked HA, whereas the correlations with the total HA modification level and with the degree of branched HA were less significant; (5) increasing HA derivatization/crosslinking over 9/3 mol% did not enhance the stability with respect to hyaluronidases. These results broaden our knowledge of these gels and provide valuable information for improving their design and characterization.

Novel Chitosan Dermal Filler with Enhanced Moldability and Elasticity

Currently, dermal fillers are largely based on commercialized cross-linked hyaluronic acid (HA) injections, which require a large injection force. Additionally, HA can be easily decomposed by enzymes, and HA-treated tissues present a risk of developing granuloma. In this study, a chitosan-based dermal filler is presented that operates on a liquid-to-gel transition and allows the injection force to be kept ≈4.7 times lower than that required for HA injections. Evaluation of the physical properties of the chitosan filler indicates high viscoelasticity and recovery rate after gelation at 37 °C. Furthermore, in an in vivo evaluation, the liquid injection-type chitosan filler transitions to a gel state within 5 min after injection into the body, and exhibits a compressive strength that is ≈2.4 times higher than that of cross-linked HA. The filler also exhibits higher moldability and maintains a constant volume in the skin for a longer time than the commercial HA filler. Therefore, it is expected that the chitosan filler will be clinically applicable as a novel material for dermal tissue restoration and supplementation.

Adipose Collagen Fragment: A Novel Adipose-Derived Extracellular Matrix Concentrate for Skin Filling

BACKGROUND

Skin filler is an option for treating skin aging and wrinkles; however, currently used fillers are limited by poor biocompatibility, rapid degradation, and possible hypersensitivity reactions. Autologous adipose tissue-derived products have been recognized as promising options for skin rejuvenation.

OBJECTIVES

This study aimed to develop a novel adipose-derived product for skin filling.

METHODS

Adipose collagen fragment (ACF) was prepared through pulverization, filtration, and centrifugation. The macrography, structure, types of collagen, and cell viability of ACF were evaluated by immunostaining, western blotting, and cell culture assays. ACF, nanofat, and phosphate-buffered saline (9 spots/side, 0.01 mL/spot) were intradermally injected in the dorsal skin of 36 female BALB/c nude mice; the skin filling capacity and the collagen remodeling process were then investigated. Twenty-one female patients with fine rhytides in the infraorbital areas were enrolled and received clinical applications of ACF treatment. Therapeutic effects and patients' satisfaction scores were recorded.

RESULTS

The mean [standard deviation] yield of ACF from 50 mL of Coleman fat was 4.91 [0.25] mL. ACF contained nonviable cells and high levels of collagen I, collagen IV, and laminin. Fibroblasts and procollagen significantly increased in ACF and ACF-treated dermis (P < 0.05). Overall, 85.7% of patients were satisfied with the therapy results, and no infections, injection site nodules, or other unwanted side effects were observed.

CONCLUSIONS

ACF significantly improved dermal thickness and collagen synthesis and may serve as a potential autologous skin filler.

Design of an elastic porous injectable biomaterial for tissue regeneration and volume retention

Soft tissue reconstruction currently relies on two main approaches, one involving the implantation of external biomaterials and the second one exploiting surgical autologous tissue displacement. While both methods have different advantages and disadvantages, successful long-term solutions for soft tissue repair are still limited. Specifically, volume retention over time and local tissue regeneration are the main challenges in the field. In this study the performance of a recently developed elastic porous injectable (EPI) biomaterial based on crosslinked carboxymethylcellulose is analyzed. Nearly quantitative volumetric stability, with over 90% volume retention at 6 months, is observed, and the pore space of the material is effectively colonized with autologous fibrovascular tissue. A comparative analysis with hyaluronic acid and collagen-based clinical reference materials is also performed. Mechanical stability, evidenced by a low-strain elastic storage modulus (G') approaching 1kPa and a yield strain of several tens of percent, is required for volume retention in-vivo. Macroporosity, along with in-vivo persistence of at least several months, is instead needed for successful host tissue colonization. This study demonstrates the importance of understanding material design criteria and defines the biomaterial requirements for volume retention and tissue colonization in soft tissue regeneration. STATEMENT OF SIGNIFICANCE: We present the design of an elastic, porous, injectable (EPI) scaffold suspension capable of inducing a precisely defined, stable volume of autologous connective tissue in situ. It combines volume stability and vascularized tissue induction capacity known from bulk scaffolds with the ease of injection in shear yielding materials. By comparative study with a series of clinically established biomaterials including a wound healing matrix and dermal fillers, we establish design rules regarding rheological and compressive mechanical properties as well as degradation characteristics that rationally underpin the volume stability and tissue induction in a high-performance biomaterial. These design rules should allow to streamline the development of new colonizable injectables.

Evaluating hyaluronic acid dermal fillers: a critique of current characterization methods

Soft‐tissue augmentation has gained much popularity in recent years. Hyaluronic acid (HA) based dermal fillers; a non‐permanent injectable device, can restore volume loss, fill fine lines and wrinkles and add curves and contours. HA based dermal fillers entered the non‐surgical treatment market in the late 1990s, however there is a lack of data and literature comparing the range of products and detailing the complexities of these products and how it relates to tissue performance. Measuring the physico‐chemical properties of these dermal fillers provide key parameters to predict their performance after injection into the body. This article reviews the currently reported methods and parameters used to characterize dermal fillers. The review of these methods and data from the literature provides a useful guide to clinicians and injectors in selecting the optimal product suitable for the needs of each patient.

Retrobulbar Hyaluronidase Injection: Does It Reach the Eye?

PURPOSE

To determine if retrobulbar injection of hyaluronidase reaches the vitreous cavity, and to determine its concentration in the vitreous.

METHODS

Prospective case-control study. Patients undergoing evisceration with implant for noninfective blind eyes were enrolled in the study. Before the evisceration, a retrobulbar injection of 3,000 IU of hyaluronidase (2 ml) was injected. Time from injection to in vivo sampling of posterior vitreous was noted. Vitreous samples from controls were obtained from patients undergoing vitrectomy for retinal detachment or diabetic retinopathy. Concentration of hyaluronidase was assessed in all 30 samples. An ELISA-based microtiter-technique was used to evaluate the activity of hyaluronidase by an avidin-peroxidase-based procedure using an ELISA reader. Incubations were carried out at room temperature and at 37°C. All the samples were analyzed in duplicates, and the mean of each sample was plotted on a scatter plot.

RESULTS

Total of 30 vitreous samples were analyzed, of which 15 were controls and 15 were test samples. Of the 15 test samples, injection-to-sampling time was 0 to 20 minutes in 4 samples, 20 to 40 minutes in 6 samples, and 40 to 60 minutes in 5 samples. The highest concentration of hyaluronidase detected in control and test samples were 2.9 and 3.0 µg/ml, and the lowest concentration was 1.7 and 1.5 µg/ml (SD 0.3), respectively. There was no significant difference between control and test groups.

CONCLUSION

Retrobulbar injection did not result in higher concentration of hyaluronidase in the posterior vitreous compared with controls when measured up to 60 minutes following injection.

Efficacy of hyaluronic acid, absorbable collagen sponge, and their combination in minimizing bisphosphonate-related osteonecrosis of the jaws (BRONJ) after dental extraction: a preliminary animal histomorphometric study

Introduction

There is no study on the effectiveness of hyaluronic acid (HA) placement either with or without absorbable collagen sponge (ACS) in reducing or preventing bisphosphonate-related osteonecrosis of the jaws (BRONJ). This preliminary animal study examined the efficacy of this clinically important treatment.

Methods

For simulating BRONJ, zoledronic acid was administered to 40 rats for 5 weeks. Two weeks later, a right first molar was extracted from each rat. The rats were randomized into four groups of socket treatments: control (empty extraction socket) or with sockets filled with ACS, HA, or HA+ACS (n=4×10). After 2 weeks, 5 rats in each group were sacrificed and subjected to histopathologic and histomorphometric evaluation. Eight weeks post-surgically, the rest of rats were euthanized and histologically examined. The Kruskal-Wallis test was used to compare the four treatments at each time point (α=0.05).

Results

Six rats were lost overall. In the second week, vascularization was higher in ACS group (P<0.05); osteoclast activity was not different between groups (P>0.05); empty lacunae were the most and fewest in control and HA+ACS groups, respectively (P<0.05); eosinophil infiltration was maximum in HA group (P<0.05); lymphocyte counts were maximum and minimum in the HA+ACS and ACS groups, respectively (P<0.05); the highest and lowest neutrophil counts were seen in ACS and control groups, respectively (P<0.05); and the extent of live bone did not differ between groups (P>0.05). In the eighth week, vascularization was not different in groups (P>0.05); the highest and lowest osteoclast activities were seen in the control and HA+ACS groups, respectively (P<0.05); empty lacunae were the most and fewest in control and HA+ACS, respectively (P<0.05); maximum and minimum numbers of eosinophils were in control and HA+ACS groups, respectively (P<0.05); HA and control groups exhibited the highest and lowest lymphocyte counts, respectively (P<0.05); the lowest and highest neutrophil counts were observed in HA+ACs and control groups, respectively (P<0.05); and the highest and lowest extents of the live bone were observed in HA+ACS and control groups, respectively (P<0.05).

Conclusions

Within the limitations of this preliminary animal study, HA and especially HA+ACS seem a proper method for preventing or treating BRONJ.

Rheologic and Physicochemical Characteristics of Hyaluronic Acid Fillers: Overview and Relationship to Product Performance

Injections with hyaluronic acid (HA) fillers for facial rejuvenation and soft-tissue augmentation are among the most popular aesthetic procedures worldwide. Many HA fillers are available with unique manufacturing processes and distinct in vitro physicochemical and rheologic properties, which result in important differences in the fillers' clinical performance. The aim of this paper is to provide an overview of the properties most widely used to characterize HA fillers and to report their rheologic and physicochemical values obtained using standardized methodology to allow scientifically based comparisons. Understanding rheologic and physicochemical properties will guide clinicians in aligning HA characteristics to the facial area being treated for optimal clinical performance.