Abstract
Fat grafting is a frequently applied procedure in plastic surgery for volume reconstruction. Moreover, the transplantation of white adipose tissue (WAT) and brown adipose tissue (BAT) increasingly gains interest in preclinical research for the treatment of obesity-related metabolic defects. Therefore, we herein directly compared the vascularization capacity and survival of WAT and BAT grafts. For this purpose, size-matched grafts isolated from the inguinal WAT pad and the interscapular BAT depot of C57BL/6N donor mice were syngeneically transplanted into the dorsal skinfold chamber of recipient animals. The vascularization and survival of the grafts were analyzed by means of intravital fluorescence microscopy, histology, and immunohistochemistry over an observation period of 14 days. WAT grafts showed an identical microvascular architecture and functional microvessel density as native WAT. In contrast, BAT grafts developed an erratic microvasculature with a significantly lower functional microvessel density when compared to native BAT. Accordingly, they also contained a markedly lower number of CD31-positive microvessels, which was associated with a massive loss of perilipin-positive adipocytes. These findings indicate that in contrast to WAT grafts, BAT grafts exhibit an impaired vascularization capacity and survival, which may be due to their higher metabolic demand. Hence, future studies should focus on the establishment of strategies to improve the engraftment of transplanted BAT.
Highlights
In humans, three types of fat tissue consisting of white, brown, and beige/brite adipocytes can be differentiated
The vascularization of White adipose tissue (WAT) and Brown adipose tissue (BAT) grafts within the dorsal skinfold chamber of recipient mice was analyzed by means of repeated intravital fluorescence microscopy
WAT grafts presented as homogenous adipose tissue (Figure 2a), which typically consists of a dense network of microvessels surrounding individual adipocytes in a regular fashion
Summary
Three types of fat tissue consisting of white, brown, and beige/brite adipocytes can be differentiated. White adipose tissue (WAT) is the most prevalent type throughout the body and acts as an energy storage in triglyceride form. It fulfills other important functions, such as the secretion of inflammatory and metabolic mediators [1]. Brown adipose tissue (BAT) is characterized by a higher number of mitochondria within each cell, permitting the conversion of stored energy into body heat by uncoupling oxidative phosphorylation. The main depots in humans are located in the supraclavicular and neck region as well as paravertebrally, mediastinally, paraaortically, and suprarenally. In rodents BAT is located in an interscapular depot [3]. Even though the extent of BAT activity and its influence on the metabolism is more pronounced in rodents, active
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