Abstract
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.
Highlights
The survival and long-term function of a tissue construct are crucially determined by its rapid and adequate vascularization after implantation, which guarantees a sufficientmicrovascular fragments (MVF) are a randomized mixture of functional arteriolar, capillary and venular vessel segments, which can be isolated in large amounts by means of mechanical dissection and enzymatic digestion of adipose tissue [4,5,6]
These findings indicate that subcutaneous adipose tissue of mouse origin contains more microvessels and a markedly higher amount of connective tissue when compared to visceral adipose tissue
Subcutaneous adipose tissue was characterized by a higher adipocyte density due to a heterogeneous mixture of mature unilocular adipocytes intercalated with small multilocular adipocytes
Summary
The survival and long-term function of a tissue construct are crucially determined by its rapid and adequate vascularization after implantation, which guarantees a sufficientMVF are a randomized mixture of functional arteriolar, capillary and venular vessel segments, which can be isolated in large amounts by means of mechanical dissection and enzymatic digestion of adipose tissue [4,5,6]. MVF are typically isolated from the epididymal fat pads of donor mice or rats [5, 10,11,12] This is due to the abundance and accessibility of this type of visceral fat tissue in rodents. In a realistic future clinical scenario, autologous MVF may be rather isolated from liposuctioned subcutaneous fat tissue of patients in an intraoperative one-step procedure. In this context, it should be considered that visceral and subcutaneous adipose tissue differ in terms of molecular, cellular and structural characteristics [13,14,15,16]. CONCLUSION: These findings indicate the need for improved protocols to generate connective tissue-free MVF isolates from subcutaneous fat tissue for future translational studies
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