Short-term pretreatment with deferoxamine enhances the in vivo vascularization capacity of nanofat seeded onto dermal substitutes

Insufficient early vascularization remains a major limitation for the successful integration of implanted dermal substitutes. To overcome this challenge, nanofat has recently been introduced as a promising fat derivative for implant seeding. The present study investigated whether short-term ex vivo pretreatment with the hypoxia-mimetic agent deferoxamine (DFO) can further enhance the in vivo vascularization capacity of nanofat. Nanofat from green fluorescent protein (GFP)+ donor mice was pretreated for 1 h with DFO (1 mM) or vehicle and subsequently seeded onto collagen-glycosaminoglycan-based dermal substitutes, which were implanted into dorsal skinfold chambers of syngeneic GFP- recipient mice. Implant vascularization, microhemodynamics, tissue integration and inflammatory response were assessed over a 14-day period using intravital fluorescence microscopy, histology and immunohistochemistry. Dermal substitutes seeded with DFO-pretreated nanofat exhibited a faster and more extensive vascularization, as evidenced by a significantly higher functional microvessel density in both implant border and center zones when compared to controls. Most blood-perfused microvessels originated from the GFP+ DFO-pretreated nanofat. The improved vascularization was associated with reduced leukocyte-endothelial cell interactions in peri-implant venules as well as a decreased implant infiltration by macrophages and neutrophils, indicating an attenuation of the early innate inflammatory response. Moreover, DFO pretreatment promoted the tissue integration of the implants and regenerative extracellular matrix remodeling, as evidenced by increased collagen III deposition. These findings demonstrate that short-term ex vivo DFO pretreatment effectively primes nanofat to enhance microvascular network formation and suppress inflammation, resulting in an accelerated and improved engraftment of nanofat-seeded dermal substitutes.