Immunoregenerative remodeling of the dermal microenvironment induced by platelet-rich plasma in atrophic abdominal striae.

Striae distensae are chronic dermal lesions characterized by extracellular matrix disruption, fragmentation of collagen and elastic fibers, fibroblast dysfunction, and impaired tissue homeostasis. Although platelet-rich plasma (PRP) has regenerative potential, the temporal tissue and immune changes associated with treatment remain incompletely understood. This exploratory longitudinal study investigated histological, histomorphometric, and immunohistochemical changes during subcutaneous autologous PRP treatment in women with post-gestational atrophic abdominal striae. Six participants were allocated to saline-control or PRP groups (n = 3 each) and received weekly applications for 12 consecutive weeks. Biopsies were evaluated at pre-treatment baseline, and after 6 and 12 weeks of treatment using Masson's Trichrome and Weigert's Resorcin-Fuchsin staining, histomorphometry, and immunohistochemistry for IL-6, iNOS, CD163, CX3CR1, CCL5, TGF-β, FOXP3, CTLA-4, and PD-L1. Peripheral-blood platelet counts and platelet concentrations in freshly prepared PRP after separation were assessed throughout treatment. PRP was associated with progressive collagen bundle thickening, improved fiber organization, reduced interfibrillar spaces, and restoration of a denser, thicker, and more interconnected elastic fiber network. These structural changes coincided with time-dependent variations in inflammatory, macrophage-associated, chemokine, regulatory, and immune-checkpoint immunoreactivities. Later samples showed increased CCL5, CX3CR1, iNOS, and TGF-β immunoreactivities, while FOXP3, CTLA-4, PD-L1, CD163, and IL-6 displayed distinct temporal patterns. Collectively, the findings indicate that PRP treatment is associated with coordinated extracellular matrix reconstruction and dynamic immune-stromal remodeling. However, the small sample and single-marker immunohistochemical design preclude causal, functional, or lineage-specific conclusions. These hypothesis-generating observations warrant confirmation in larger studies using standardized PRP characterization, molecular assays, multiplex imaging, and spatial or single-cell approaches.