Comparative analysis of collagen-stimulating effects of poly-L-lactic acid, poly-D, L-lactic acid, and polycaprolactone subcutaneous injections in porcine model

Dear Editor, Biostimulators are cutting-edge cosmetic treatments that rejuvenate the skin by stimulating collagen production. Poly-L-lactic acid (PLLA; Sculptra; Galderma), poly-D, L-lactic acid (PDLLA; AestheFill, REGEN), and polycaprolactone (PCL; Ellansé; Sinclair Pharma) stimulate the biosynthesis of type I collagen (COL1), thereby remodeling the dermal architecture, augmenting skin thickness and elasticity, and achieving cosmetic volumization and wrinkle correction.[1] Biostimulators have been shown to induce the production of type III collagen (COL3), which functions as a subcutaneous scaffold and plays a crucial role in reducing superficial facial static wrinkles.[2] This study investigated the ability of these three biostimulators to stimulate collagen synthesis at different time points. PLLA, PDLLA, and PCL were subcutaneously injected into the dorsal skin of six adult Lee-Sung minipigs [Table S1]. Skin samples were obtained at 28, 91, and 182 days after injection, and collagen production was examined. The procedures are detailed in Supplementary Materials. After the skin samples were harvested, quantitative reverse transcription polymerase chain reaction was performed to determine the mRNA expression levels of COL1 and COL3. In addition, immunohistochemistry staining was performed on skin samples to assess COL1 and COL3 densities. At 28 days postinjection, PLLA led to a higher mRNA expression of COL1 compared to PDLLA. Furthermore, at days 91 and 182, the increase in COL1 mRNA expression induced by PLLA remained significantly greater than that observed with the other two biostimulators. Similarly, at 28 days, PLLA resulted in higher mRNA expression levels of COL3 compared to PDLLA [Figure 1]. However, by days 91 and 182, no significant differences in COL3 expression were noted among the three biostimulators. Histological analysis confirmed that at 28 days postinjection, PLLA stimulated a higher density of COL1 fibers compared to the other biostimulators [Figure 2].Figure 1: Quantitative polymerase chain reaction of type I and type III collagen expression levels following stimulation at 28, 91, and 182 days. Note: *P < 0.05, **P < 0.01. NS: no significance.Figure 2: Density of type I collagen fibers (depicted in brown) was assessed using immunohistochemical staining. Noticeable variations in collagen density were observed on day 28. Representative histological micrographs from the animal specimens Y171 (day 28), Y173 (day 91), and Y167 (day 182) are presented. Scale bar = 50 μm.The factors influencing the type and degree of the reaction between the material and host include composition, size, shape, surface roughness, and porosity of the biostimulator. In this study, the increased production of COL1 after PLLA injection compared with after PDLLA and PCL injection may be attributed to several factors. First, PLLA has a slower degradation rate,[3,4] leading to its prolonged presence within the deep dermis or subcutaneous layer and the sustained activation of fibroblasts. Second, PLLA induces a more pronounced foreign body reaction due to its rough surface and irregular shape, stimulating collagen production by fibroblasts.[5] These effects are less pronounced with PDLLA and PCL due to their faster degradation and the less prominent reactions induced. Differences in the chemical structure may also influence collagen production. Further research is needed to fully understand these mechanisms and to evaluate the long-term effects of the 3 biostimulators. This study has several limitations. First, the functionality (i.e., tensile strength and elasticity contribution) of the newly produced collagen was not evaluated, limiting our understanding of the practical effects of the biostimulators. Second, the 6-month observation period in this study may not capture the long-term effects of the biostimulators on collagen production and skin quality. Longer-term studies are essential to assess the durability and sustainability of the observed effects. This study compared PLLA with PDLLA and PCL using a porcine model and revealed that PLLA has a superior ability to stimulate COL1 production, with this effect sustained for at least 182 days. However, while PLLA initially induced higher levels of COL3 compared to PDLLA, these differences diminished after day 91, indicating that the long-term impact of PLLA is primarily driven by its effect on COL1 rather than COL3. Although elevated COL1 levels can contribute to skin volumization and structural support, excessive COL1 production may pose a risk of scarring or fibrosis. Therefore, while PLLA remains a promising candidate for enhancing skin rejuvenation, it is essential to carefully optimize dosing and application techniques to minimize potential adverse outcomes. Future research should focus on validating these findings in human subjects and evaluating the safety and efficacy of PLLA in various clinical settings, as well as exploring its use in combination therapies to maximize its potential in both aesthetic and regenerative medicine. Ethical approval Institutional Animal Care and Use Committee (IACUC) approval stutas: NLAC-111-M-024. Data availability statement The datasets generated during and/or analyzed during the current study are not publicly available, but are available from the corresponding author on reasonable request. Financial support and sponsorship Nil. Conflicts of interest Dr. Jeff Huang Cheng-Chieh, Dr. Jason Li Chien-Nien, Dr. Luiz Eduardo Toledo Avelar, Dr. Alessandra Haddad and Dr. Stephanie Lam are speakers and medical consultant of Galderma. Dr. Leon Tsung-Ju Lee has no conflict of interest to disclose.