In Vivo Investigation of the Biostimulatory and Rejuvenating Effects of Small-Particle Cross-linked Hyaluronic Acid Injections in Photoaged Human Skin

Injection of cross-linked hyaluronic acid (CLHA) has been traditionally utilized to treat wrinkles and provide volume. Recent studies have also shown that intradermal placement of CLHA provides lasting secondary effects and may be a useful method for improving skin appearance and physiology.The aim of this study was to investigate the biostimulatory effects and potential underlying mechanisms induced by repeated intradermal microinjections of small-particle cross-linked hyaluronic acid (SPCLHA) for skin rejuvenation.Eight patients with photoaged forearm skin underwent three intradermal microinjections of SPCLHA and isotonic sodium chloride (control). At 0, 4, 8, 12, and 24 weeks, biophysical parameters were measured, and skin biopsies were obtained at 12 and 24 weeks for assessment employing histological and immunohistochemical analyses, transmission electron microscope, and real-time fluorescence quantitative polymerase chain reaction.SPCLHA treatments significantly improved skin appearance and physiologic functions starting at 8 weeks. Histologic examination revealed thickening of the epidermis, more red-stained collagen fibers in the dermis, and increased formation of blood vessels in SPCLHA-treated skin. Immunohistochemical evaluation showed increased collagen deposition, proliferation of keratinocytes and fibroblasts, and cutaneous vascularity in SPCLHA-treated skin compared with controls. Fibroblasts appeared morphologically stretched with well-developed rough endoplasmic reticulum. Gene expression concerning various extracellular matrix (ECM) proteins and growth factors was upregulated at 12 weeks and several genes remained upregulated at 24 weeks.Intradermal microinjections of SPCLHA can stimulate production of collagen and other ECM components, restore the structural integrity of dermal microenvironment, and may be considered an effective method for skin rejuvenation.