Effects and the mechanism of pine pollen polysaccharides on diabetic wound healing in vitro and in vivo

Introduction: Pine pollen polysaccharides (PPPS) has anti-inflammatory, immunomodulatory, anti-oxidant, hypoglycemic, and anti-bacterial properties. PPPS can accelerate wound healing in mouse cutaneous wounds, yet it is unclear whether PPPS can promote diabetic wound healing. Methods: Fibroblasts, keratinocytes, and human umbilical vein endothelial cells (HUVECs) were stimulated with high glucose (HG) to mimic hyperglycemic environment. Cell viability, apoptosis, migration, and angiogenesis were assessed by cell counting, Western blot, transwell migration, and tube formation assays. Neutrophil extracellular traps (NETs) and macrophage polarization were analyzed by immunofluorescence and flow cytometry. Streptozotocin-induced diabetes mellitus (DM) mice were subjected to skin wounds and PPPS administration to validate the role of PPPS in diabetic wound healing. Results: PPPS treatment impaired HG-induced viability reduction, apoptosis promotion, and migration repression of fibroblasts, keratinocytes, and HUVECs, accompanied by promotion of angiogenesis of HUVECs under HG stimulation. Specifically, PPPS treatment facilitated NET degradation and suppressed macrophage M1 polarization. Furthermore, PPPS accelerated diabetic wound healing in DM mice, along with decreased citrullinated H3 and PAD4 protein levels and elevated CD31 protein levels, suggesting that PPPS facilitated re-epithelialization and vascularization and reduced NETs. Conclusions: PPPS accelerates diabetic wound healing via mediating NETs and the polarization of M1-type macrophages, providing new insights into the promoting role of PPPS in diabetic wound healing.