Adipose tissue engineering from adult human stem cells: a new concept in biosurgery.

Current autologous fat grafting technique suffers from the drawbacks of donor site morbidity and, more importantly, significant resorption of the grafted fat. Adipose tissue engineering using adult human stem cells has been found to overcome the shortcomings of autologous fat grafting in reconstructing facial defects. Mesenchymal stem cells that can self-renew and differentiate into mature adipocytes have been used to generate adipose tissue, in both in vitro and in vivo cell transplantation studies. However, long-term maintenance of the shape and dimension of the produced adipose tissue remains a challenge, even in tissue engineering with cell transplantation. The choice of appropriate scaffolds to promote stem cell adhesion, proliferation, and differentiation is essential for successful adipogenesis. Recent advances in nanotechnology allow the development of nanostructured scaffolds with a cellular environment that maximally enhances not only cell expansion but also the neovascularization that is crucial for long-term maintenance of cell volume. Cell homing is a technique that actively recruits endogenous host stem cells into a predefined anatomic location for the desired tissue generation. Bypassing ex vivo cell manipulation, the cell homing technique eliminates donor site morbidity and rejection, reducing the regulation issue in clinical translation. Mao et al. introduced the concept of biosurgery, which combined nanostructured scaffolds and growth factor biocues, with or without cell transplantation, for successful de novo adipogenesis in restoring facial defects. Important questions, such as the necessity of cell transplantation in scaling up the size of engineered adipose tissue, need to be answered with further studies. However, the era of biosurgery replacing conventional treatments such as biologically inactive filler injections and alloplastic implants appears to be in the near future.