Fibroblast cellular responses to calcium hydroxyapatite-based biomaterials

Introduction: Calcium hydroxyapatite (CaHa) is widely used in aesthetic procedures as a collagen biostimulator. Objective: This study evaluated how different concentrations of CaHA (0.5% to 2.5%) in three commercial formulations (Stiim®, Rennova®, and Radiesse®) influence cell viability, human fibroblast proliferation, and gene expression of extracellular matrix markers, including type I and III collagen, osteocalcin, and osteopontin. Material and method: CaHa were evaluated on cell viability, proliferation, and gene expression of extracellular matrix markers in human fibroblasts (n=3, each time-point). Cell viability was assessed using MTT and trypan blue exclusion assays, proliferation by cell counting, and gene expression of type I and III collagen, osteocalcin, and osteopontin by RT-PCR. Result: Stiim® showed a significant increase in viability at lower concentrations (1% and 2%) after 24 h and at 0.5% and 1% after 72 h, while the 2.5% concentration drastically reduced viability. Radiesse® demonstrated greater stability, with early proliferation stimulation and sustained induction of both type I and III collagen. Rennova® exhibited a later and more variable response, with reduced proliferation at intermediate concentrations. Osteocalcin and osteopontin expression varied between formulations, with Radiesse® showing a stronger stimulatory effect. The results indicate that HA effects on fibroblasts are formulation- and concentration-dependent, directly influencing cellular behavior and biostimulatory potential. Conclusion: These gene expression findings suggest that CaHA may promote pathways associated with dermal neocollagenesis.