Background: Adipose tissue-derived microvascular fragments (MVF) represent effective vascularization units for tissue engineering. Most experimental studies in rodents exclusively use epididymal adipose tissue as a visceral fat source for MVF isolation. However, in future clinical practice, MVF may be rather isolated from liposuctioned subcutaneous fat tissue of patients. Therefore, we herein compared the vascularization characteristics of MVF isolates from visceral and subcutaneous fat tissue of murine origin. Methods: MVF isolates were generated from visceral and subcutaneous fat tissue of donor mice using two different enzymatic procedures. For in vivo analyses, the MVF isolates were seeded onto collagen-glycosaminoglycan scaffolds and implanted into full-thickness skin defects within dorsal skinfold chambers of recipient mice. Results: By means of the two isolation procedures, we isolated a higher number of MVF from visceral fat tissue when compared to subcutaneous fat tissue, while their length distribution, viability and cellular composition were comparable in both groups. Intravital fluorescence microscopy as well as histological and immunohistochemical analyses revealed a significantly reduced vascularization of implanted scaffolds seeded with subcutaneous MVF isolates when compared to implants seeded with visceral MVF isolates. Light and scanning electron microscopy showed that this was due to high amounts of undigested connective tissue within the subcutaneous MVF isolates, which clogged the scaffold pores and prevented the interconnection of individual MVF into new microvascular networks. Conclusion: These findings indicate the need for improved protocols to generate connective tissue-free MVF isolates from subcutaneous fat tissue for future translational studies.

Adipose tissue-derived microvascular fragments (MVF) represent effective vascularization units for tissue engineering. Most experimental studies exclusively use epididymal fat tissue of male donor mice as a source for MVF isolation. However, in future clinical practice, MVF-based approaches may be applied in both male and female patients. Therefore, we herein compared the vascularization capacity of MVF isolated from the epididymal and peri-ovarian fat tissue of male and female donor mice. Freshly isolated MVF from male and female donors did not differ in their number, length distribution, viability and cellular composition. After their assembly into spheroids, they also exhibited a comparable in vitro sprouting activity. Moreover, they could be seeded onto collagen-glycosaminoglycan matrices, which were implanted into full-thickness skin defects within mouse dorsal skinfold chambers. Repetitive intravital fluorescence microscopy as well as histological and immunohistochemical analyses revealed a comparable vascularization and incorporation of implants seeded with MVF of male and female origin. Taken together, these findings demonstrate that the vascularization capacity of MVF is not gender-specific.