Enhancing Regenerative Outcomes: Histopathological Comparison of Calcium Hydroxylapatite Alone and Combined With Platelet-rich Fibrin: A 6-week Study.

BACKGROUND: Calcium hydroxylapatite-carboxymethylcellulose (CaHA-CMC) is a widely used biostimulatory filler that promotes collagen production through fibroblast activation. Platelet-rich fibrin (PRF) has been proposed as a bioactive adjunct capable of enhancing tissue regeneration. Because collagen remodeling becomes more evident weeks after injection, this study aims to evaluate whether the addition of PRF modifies the subdermal tissue response at 6 weeks. METHODS: A prospective observational study was conducted in 5 patients undergoing abdominoplasty. Four conditions were evaluated: saline (control), PRF alone, CaHA-CMC + saline solution, and CaHA-CMC + PRF. Injections were administered subdermally 6 weeks before surgery. Tissue samples were collected intraoperatively and analyzed using hematoxylin and eosin staining and immunohistochemistry. A semiquantitative histomorphometric surrogate analysis was performed using the collagen-associated eosinophilic area. Statistical comparisons were conducted using Wilcoxon signed-rank tests. RESULTS: The CaHA-CMC + PRF group demonstrated the highest collagen-associated eosinophilic area values (~4.4 times versus control; P = 0.01), followed by CaHA-CMC + saline solution (~2.3 times; P = 0.03). The PRF-only group showed a mild, nonsignificant increase (~1.6 times; P = 0.08). Immunohistochemical analysis suggested increased type IV collagen expression, CD45-positive, lymphocyte infiltration, and neovascularization in the CaHA-CMC + PRF group compared with other groups. These findings indicate a more pronounced and coordinated tissue response in the presence of PRF. CONCLUSIONS: The addition of PRF to CaHA-CMC may enhance subdermal tissue remodeling at 6 weeks. However, given the small sample size and semiquantitative methodology, these results should be interpreted as exploratory and require further validation.