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This study investigated the impact of vitamin D status on the regenerative potential of serum exosomes in diabetic and non-diabetic patients, using a wound healing assay with HaCaT keratinocytes treated with exosomes from vitamin D-sufficient and deficient individuals (n=22). The key finding was that exosomes from vitamin D-sufficient donors enhanced keratinocyte healing, while those from vitamin D-deficient diabetics did not. 1α,25(OH)₂D₃ promoted proliferation up to 100 nM, with inhibition at 200 nM.
Vitamin D status, rather than glycemic control, appears to be a critical determinant of the regenerative capacity of serum exosomes, suggesting a potential target for improving wound healing in diabetic patients.
Vitamin D is a critical factor in immune regulation and epithelial regeneration. Vitamin D deficiency is commonly observed in diabetic patients and is associated with impaired wound healing. Circulating exosomes transport bioactive molecules and influence cellular behavior relevant to tissue repair. This study aimed to investigate the capacity of serum exosomes derived from individuals with/without diabetes and with different vitamin D statuses to enhance keratinocyte-mediated wound healing. Serum samples were collected from diabetic patients and healthy nondiabetic controls [22 participants in total: eight healthy volunteers and 14 patients with type 2 diabetes, of whom six were vitamin D-sufficient (>20 ng/mL) and eight were vitamin D-deficient (<20 ng/mL)]. Exosomes were isolated using ExoQuick™ and quantified using the ExoView R200 platform. HaCaT keratinocytes (HaCaT cells—human immortalized keratinocytes) were subjected to a wound healing assay and treated with serum-derived exosomes or with different concentrations of 1α,25(OH)₂D₃. Expressions of cytokeratin 14, E-cadherin, and vitamin D receptor were measured using immunofluorescence. Exosomes from vitamin D-sufficient donors enhanced keratinocyte healing, while those from deficient diabetics were ineffective. 1α,25(OH)₂D₃ promoted proliferation up to a concentration of 100 nM, with inhibition at 200 nM. This biphasic response aligns with those of previous studies and suggests a threshold beyond which calcitriol may exert feedback-inhibitory or cytostatic effects. Regenerative efficacy aligned more with vitamin D status than glycemic metrics. Vitamin D status influences the regenerative efficacy of circulating exosomes. Stratifying diabetic patients by vitamin D levels may improve the outcomes of exosome-based therapies.
