Maintaining a youthful, healthy, and natural appearance while aging fuels the social interactions and quality of life.1 Minimally invasive fillers for soft-tissue augmentation are among the most widespread aesthetic treatments for facial rejuvenation, and hyaluronic acid (HA)-based fillers have become the second most popular nonsurgical aesthetic procedure.2–4
For each indication, optimal outcomes require a specific injection technique but also selecting the right HA filler. To preserve a natural expressiveness of emotions, injectables must adapt to facial dynamics like native soft tissues.3,4 Hence, selecting fillers with appropriate rheological properties is key to achieve natural-looking and durable aesthetic results. These will determine gel performances when exposed to diverse mechanical stresses in various facial areas.5
For many injectables, gel stabilization is ensured by chemically crosslinking HA polymers with BDDE-covalent bonds, resulting in stabilized HA chains with a degree of modification (MoD) usually ranging between 6% and 10% depending on intended indications.3,6–9 TEOSYAL RHA (Resilient Hyaluronic Acid) gels are 4 monophasic cohesive fillers specifically developed to accompany and sustain facial dynamics. The manufacturer optimized their crosslinking reaction conditions to better preserve natural HA polymers from unintended cleavage and degradation resulting from classical methods. The resulting longer chains form a densely entangled network, which, consequently, requires fewer BDDE-covalent bonds for stabilization. Hence, their MoD is substantially decreased from 6%-10% to 2%-4%, rendering the long HA chains less rigidly crosslinked9 and maintaining their ability to interact and slide dynamically within the gel.
Their mechanical characterization10 demonstrated that RHA gels possess resilient properties (rheological data on file, TEOXANE): that is the ability to recover an original shape/position and retain mechanical properties, after being bent, compressed or stretched. This combination of flexibility and strength likely explains the cohesivity and stretching abilities previously reported for RHA.9 It is reminiscent of endogenous dermal HA and believed to be key to the respect of facial dynamics and muscle activity.
However, the wrinkle filling efficacy of RHA gels and their durability, given their lower MoD, had not been investigated yet. Here, the authors report the results of a randomized, controlled, split-face, double-blinded trial comparing during 18 months the safety and the efficacy of 3 RHA fillers versus already marketed comparators, in the treatment of nasolabial fold (NLF). Subjects with moderate wrinkles were treated with RHA2, whereas subjects with severe wrinkles were treated with either RHA3 or RHA4.
The protocol was approved by an Independent Ethics Committee (Centre Léon Bérard—Sud Est IV) and authorized by the French authority ANSM on February 11, 2014. Before inclusion, all participants signed a fully informed consent form. The study was conducted in compliance with the Helsinki declaration, with 6 treating investigators at a single investigational site specialized in dermatological clinical studies (Contract Research Organization DERMSCAN, Villeurbanne, France) between February 2014 and September 2015.
Ninety eligible subjects displaying 2 visible symmetrical NLF were recruited by DERMSCAN, from their database of registered volunteers: 30 with moderate (Wrinkle Severity Rating Scale [WSRS] = 3) and 60 with severe (WSRS = 4) NLF.11 Exclusion criteria included diabetes, autoimmune diseases, allergy to filler ingredients (e.g., lidocaine), coagulation troubles, anti-inflammatories or anticoagulants uptake 1 week before injection, facial subcutaneous retaining structure, permanent or semipermanent fillers, resorbable filler injections in the NLF within a year, facial botulinum toxin injection, facial peeling, laser or ultrasound treatment within 6 months, enrolment in another clinical trial on NLF within 4 weeks before study, or in an exclusion period from a previous study.
RHA2, 3, and 4 (TEOXANE, SA, Geneva, Switzerland) are viscoelastic, sterile, nonpyrogenic, clear, colorless, and biodegradable crosslinked sodium HA (NaHA from nonanimal origin) gel devices, in a physiological buffer (pH 7.3), which contains 0.3% lidocaine hydrochloride to reduce pain upon injection. Lidocaine-containing respective comparators were Juvederm Volift (VYC‐17.5L) and Ultra4 (ULT4) (Allergan, Inc., Irvine, CA) and TEOSYAL PureSense Ultra Deep (UD) (TEOXANE, SA, Geneva, Switzerland) (Table 1).8,9,12
Treatments and Blinding
Each NLF was injected with an RHA gel and its contralateral counterpart with the respective comparator (Figure 1). Optional touch-up was performed on one or both NLF using the same products for optimal aesthetic results. Injection depths were compliant with instructions for use. Volumes and techniques were determined by the injectors, but the technique had to be identical for both NLFs of each subject. The study products were labeled with the subject number, the side, and the order of injection according to a randomization list established before the study and kept in a sealed envelope, in the Trial Master File during the study. These data were unknown to injected subjects and the blind live evaluator (BLE, or main investigator, for the assessment of efficacy criteria) who did not perform the injection.
This study comprised 9 visits (V1–V9) (Figure 1). V1: Subjects screening and clinical evaluation of inclusion/exclusion criteria, subjects' medical history recording, initial WSRS scores assessment, concomitant medication examination, and consent form signing. V2: Subjects randomization and injection on Day 0 (D0). Physicians recorded efficacy and safety parameters and took before/after photographs of the NLF. Subjects filled a satisfaction questionnaire, and pain was assessed. V3: Aesthetic improvement optimization: subjects received a touch-up injection if deemed necessary by the injector, on D14. Efficacy, pain, and safety parameters were recorded. V4–V9: Efficacy and safety parameters were recorded from Month 1 (M1) to 18 (M18).
Evaluation Criteria and Assessments
Primary End Point
The main assessment criterion was the clinical evaluation of NLF improvement from preinjection using WSRS scores,11 rated on-site by an independent BLE at M6.
Secondary End Points
Throughout the study: (1) Clinical evaluation of NLF WSRS score improvement from baseline by the BLE. (2) Evolution of the NLF volume from baseline using 3D Dermatop (Eotech, SA. Marcoussis, France): The technique consists in reconstructing skin topography by interference fringe projection.13 Fringes of different widths are projected onto the explored skin area of the subject and are deformed proportionally to the skin relief. Several different camera acquisitions of that same area allow the software to reconstruct its profilometry and to calculate the height of every point. Computer processing provides quantitative measurements of parameters of the cutaneous relief such as the volume (mm3) of the NLF cavities over a 4-cm2 facial area. Measurements of the exact same facial area were performed at all time points of the study. Pseudocolored photographs were also created with a topographic heat map calibrated from the highest (orange-red) to deepest (blue-magenta) facial points. For each subject, calibration was set before treatment and used for all subsequent measurements. (3) Global Aesthetic Improvement Scale (GAIS) scores assessment by physicians and subjects. (4) Assessment of the injection quality with a subjective evaluation questionnaire. (5) Analysis of Patient-Reported Outcome Measures using the FACE-Q scale14 (appraisal of the NLF) and satisfaction questionnaires. (6) Photographic illustration of filler injection results.
(1) Pain assessment, using a 100-mm Visual Analog Scale15 during and at 5, 15, and 30 minutes after injection. (2) Safety evaluation using injection site reactions (recorded daily by the subjects in a diary for 14 days after each injection). (3) Adverse event collection by the BLE at each visit.
After database lock, statistical analyses were performed for efficacy parameters on the Intention-To-Treat (ITT) population and for safety parameters on the “safety” population. Analyses were conducted on RHA products versus comparators, either within groups individually or pooled together. WSRS score comparisons were performed using the Wilcoxon signed-rank test. The last-observation-carried-forward method was used at M15/M18 because subjects whose WSRS score came back to their pretreatment score (correction lost on both sides) at M12/M15 exited the study. Post hoc statistical tests were performed for secondary end points, for descriptive purposes.
Subject Demographics, Initial Treatment, and Touch-up
The 3 treatment groups showed similar demographic characteristics. The mean age was 57.9 years. The population was mixed in terms of genders (83.3% females) and Fitzpatrick skin phototypes (94.4% Types I–III). Mean total volumes injected per subject were very similar between groups in each arm. When groups were pooled together, the percentage of NLF that needed a touch-up was nonsignificantly lower for RHA gels than comparators (Table 2).
Primary Efficacy Criterion and WSRS Scores
Globally, no significant difference in WSRS score evolution was observed over time between RHA and comparators. In Group 1, the mean WSRS score was significantly reduced from 3.0 to 1.6 (p < .001) on both sides, at M6. No difference was observed between sides, over time, despite a slight trend in favor of RHA2 (Figure 2Aa). At M12, 50% of the NLF treated with VYC‐17.5L had already come back to the pretreatment score, compared to only 30% with RHA2. This advantage in favor of RHA2 persisted until M18 (Figure 2Ba). In Group 2, WSRS improvement was also substantial (from 4.0 at baseline to 1.9 (p < .001) at M6 on both sides). The evolution of scores and proportions of subjects with NLF back to baseline over time were close to identical between fillers (Figure 2Ab, Bb). In Group 3, the WSRS score was substantially reduced from 4.0 to 1.8 (RHA4) versus from 4.0 to 1.9 (UD) (p < .001) at M6. A trend in favor of RHA4 was consistently observed until M18 (Figure 2Ac, Bc), the difference being statistically significant at M15.
Secondary Efficacy Criteria
Evolution of NLF Volumes
For each subject, photographs were acquired (Figure 3A) and quantification of NLF correction was performed using the 3D Dermatop system (see Methods). Interference fringe projection measurements were computer-processed to provide pseudocolored illustrations of wrinkle topography (Figure 3B) as well as quantification of cavity volumes (Figure 4). In Group 1, optimal cavity filling was achieved at D14, with substantial reductions in NLF volumes that were very similar: from mean values of 4.1 to 0.8 mm3/4 cm2 for RHA2, versus from 4.5 to 0.9 mm3/4 cm2 for VYC‐17.5L (Figure 4). From M6 onward, despite no significant difference between sides, a trend in favor of RHA2 was noticed. In Group 2, NLF volume reduction was initially similar (from 9.0 to 2.1 mm3/4 cm2 for RHA3 vs from 8.6 to 2.1 mm3/4 cm2 for ULT4, at D14), and then slightly but consistently more important with RHA3 than ULT4, reaching statistical significance at M18 (respectively, 3.7 vs 5.2 mm3/4 cm2 at M18). In Group 3, volume reduction was initially similar (from 9.1 to 1.4 mm3/4 cm2 for RHA4 vs from 9.2 to 1.8 mm3/4 cm2 for UD, at D14). Then, a more pronounced difference in favor of RHA4 was observed consistently throughout the study, reaching statistical significance from M12 onward (respectively, 3.3 vs 5.4 mm3/4 cm2 at M18). Altogether, these data suggested that RHA gels have a longer filling duration than comparators.
Global Aesthetic Improvements
Most subjects and physicians rated GAIS scores as “improved” or “much improved” from before treatment, for all products. No statistical difference (the McNemar test) was observed between gels at any visit. As a whole, improvement was reported by at least 90% of subjects and physicians up to M6, and reached a minimum of 56.7% at M12 (Table 3). In Group 1, at M12, 50% of subjects still assessed their NLF as “much improved” with RHA2, versus 33% with VYC‐17.5L. In Group 2, results were in favor of ULT4 until M6 and slightly in favor of RHA3 at M9/M12. Globally, in Group 3, “much improved” results were reported with a higher proportion for RHA4 throughout the study with a pronounced difference at M9: 60% versus 40% (Figure 5). These results (Table 3 and Figure 5) show that both physicians and subjects reported high GAIS scores at all time points. They also suggest that over the long term, subjects tend to favor RHA fillers over comparators.
Injectors' Satisfaction With the Products
For all filler injections, treating investigators were asked to assess the easiness of use and aesthetic results observed on D0. Injectors were globally “satisfied” to “very satisfied” with all products. Results tended to favor RHA products over comparators in terms of easiness of injection (deemed “very satisfactory” for 68% vs 51% of injectors), easiness of product positioning (63% vs 48%), as well as results observed immediately (61% vs 48%) or after massage (85% vs 78%) (Figure 6). These results indicate that injectors tend to express an overall preference for RHA fillers.
Subject Satisfaction on the Long Term
Subjects were asked to deem how treatment outcomes affected their quality of life and self-image. NLF appraisal using the FACE-Q14 questionnaire was similar for all products until M12. However, from M15 onward, a trend in favor of RHA products was observed, in terms of proportions of subjects not bothered anymore by “the depth of their NLF” and “how old these wrinkles make them look” (Figure 7A, B). A similar trend was observed when the subjects' faces were either relaxed or in a dynamic pose (Figure 7C, D). This suggests that RHA products enhance the confidence of subjects with their appearance and even more than comparators on the long term.
Safety and Pain Assessment
Injection site reaction reported by subjects and investigators were consistent with HA fillers, mainly bruising, redness, hardening, pain/tenderness, lumps/bumps, and swelling. Most were mild-to-moderate and lasted ≤7 days. One month after injection, only a few subjects still displayed redness, hardening, lumps/bumps, or swelling (1%–10%). Neither Unexpected Adverse Device Effects nor device-related Serious Adverse Events were reported in this study. The safety of all tested RHA products can thus be considered as good and equivalent to comparators (the McNemar exact test). Injection-induced pain levels reported were not statistically different between products (the Wilcoxon signed-rank test) and fell below the “no pain” threshold (10 mm)16 within 5 minutes after injection.
This randomized controlled trial investigated 3 monophasic cohesive fillers characterized by long (high molecular weight) HA chains and reduced crosslinking rates. Although BDDE-crosslinked HA has long been reported to be safe and well tolerated,17 some authors have hypothesized that high degrees of BDDE crosslinking, associated with short HA chains, might influence the development of delayed reactions.18,19 The authors' results demonstrated that RHA fillers developed with low levels of BDDE crosslinking, offered efficacy and safety profiles at least equivalent to well-established comparators possessing higher MoDs. Furthermore, results also showed that RHA fillers offered improved satisfaction immediately after injection but also in the long term, both for investigators and subjects.
These features might largely rely on the mechanical resilience of these gels. It may render them less stiff and adaptable to stretching forces, as previously reported from in vitro tests.9 It may also provide strength to resist repeated compressions in mobile facial areas. The stretching ability likely translates into improved comfort during injection, as reported by physicians (Figure 6). It may also influence gel biointegration, ensuring easier positioning and eliciting improved immediate aesthetic results and higher satisfaction right after injection (Figures 5 and 6). These results are consistent with the reported good implant integration in tissues at a variety of injection depths and the natural-looking corrections obtained with RHA, both immediately and during a 6-month follow-up.9
Resilient HA fillers demonstrated excellent results in terms of WSRS score evolution over 18 months. Indeed, the proportion of subjects whose NLF went back to their baseline score showed a trend in favor of RHA products over time, supporting their long-lasting efficacy (Figure 2). Nasolabial fold volume quantification corroborated the improved durability for RHA fillers in each treatment group, from 6 months onward (Figures 3 and 4). This also translated into increased subject aesthetic satisfaction for RHA fillers versus comparators, up to 18 months, the difference being substantially more pronounced at later time points (Figures 5 and 7).
The long-lasting effect of RHA fillers, despite their decreased crosslinking, may rely on biochemical and mechanical grounds. First, enzymatic and Reactive Oxygen Species (ROS)-mediated biodegradation of the longer chains entangled in RHA gels may prove more difficult and time-consuming than for shorter chains, in vivo. Second, their stretching capacities may translate into increased adaptability to constraints associated with repeated movements and facial dynamism. Thus, resilience may provide RHA gels with a durable ability to resist degradation induced by muscle contractions. This is in line with a recent study, which demonstrated that when the pressure applied on fillers by muscle contraction is relieved by botulinum toxin, the durability of HA implants is consequently substantially increased.20 Although attractive, these potential mechanisms still have to be experimentally confirmed with further investigations.
The authors are grateful to Cédric Jung and Audrey Natalizio (DERMSCAN), and François Bourdon, Patrice Delobel, Kevin Legent, Stéphane Meunier, and Sylvain Moisenier (TEOXANE) for their help.
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