Dermal response to combined double filler administration

Aim. This experimental work presents a comparative assessment of the effect of hyaluronic acid and crystalline calcium hydroxyapatite on derma in separate and combined application setting.Materials and methods. The study used rats (30 animals) for subdermal injection of 0.05 ml medium. Group 1 was administered calcium hydroxyapatite (Radiesse (Merz, Germany)), group 2 received hyaluronic acid (Restylane (SabQ, Sweden)) and Group 3 — both preparations combined in ratio 1:1 (Mix). Results were evaluated 4 months after the filler injection. Sections were stained with haematoxylin–eosin, van Gieson’s and Masson’s trichrome techniques. Collagen types I and III were detected with polyclonal antibodies (Abcam, England). Fibroblasts were positively identified with vimentin (LabVision), macrophages — with CD68 (LabVision) tagging. Effect of extracellular matrix remodelling was studied with α-SMA actin (Abcam, England).Results. We demonstrate that separate filling of hyaluronic acid and calcium hydroxyapatite produces different response mechanisms, while their combined administration does not lead to a marked voluming of the dermal extracellular matrix.Conclusion. Combined administration of the two fillers under study may facilitate a prolonged effect of their combined action exceeding 4 months, due to the absence of fibrosis, complications and side effects.