Platelet α-granule cargo packaging and endocytosis are important for normal mouse skin wound healing

Platelet-rich plasma or platelet-derived factors are often used to promote acute and chronic wound healing, an intricate multi-step process involving multiple cell types and factors. However, their use is controversial with mixed results, stressing the need for detailed functional insights into how platelets affect wound healing, beyond initial hemostasis. Our study investigated the importance of platelet function in physiological healing using a dorsal full-thickness excisional skin wounding of mice with defects in α-granule cargo packaging (Nbeal2-/- mice) and endocytic trafficking (platelet-specific Arf6-/- and VAMP2/3∆ mice). Wound healing dynamics and skin structure, as established by histology, were significantly disrupted in all three mouse strains. Each showed unique kinetic, morphological, and structural healing patterns that differed from wild-type controls. Notably, Nbeal2-/- mice had delayed (epi)dermal regeneration, which was reflected by reductions in scab formation and/or resolution, re-epithelialization, and cell migration and proliferation. In the platelet-specific endocytosis-deficient mice, Arf6-/- and VAMP2/3∆, slower re-epithelialization was accompanied by defects in structural skin characteristics, including wound collagen and muscle/keratin content. Molecular profiling of bioactive peptides from skin (wound) extracts showed how modulating platelet α-granule cargo or endocytosis differentially affected healing, beyond initial hemostasis. Based on the changing profiles in the presence of several bioactive molecules (e.g., IL-1β, VEGF, MMP-9, and TIMP-1), the inflammation, proliferation, and tissue remodeling phases appear to all be affected by platelet function(s). These findings provide a better understanding of platelets' role in all wound healing phases, advancing clinical wound care.