Effect of Concentrating Endogenous Stromal Cells in the Fat Graft

Craniofacial injuries have serious psychosocial sequele and affect quality of life. Many individuals who suffer significant facial disfigurement from injury experience psychological distress and impairment in functioning not limited to the acute phase of injury, but over a longer term period of treatment, recovery, and adjustment. Until recently, treatment of disfiguring craniofacial injuries has been mostly limited to surgical flap procedures, microsurgical tissue transfer, and implantable prostheses. However, these methods can leave conspicuous scars on the face and the donor site, and in the case of implants can lead to complications associated with foreign materials. Autologous fat grafting with minimally invasive cannulas is a procedure that has been used for decades in common plastic surgery practice for facial aesthetic procedures. This technique is also a promising treatment for soft tissue reconstruction after craniofacial trauma because the graft harvest and injection are minimally invasive. The treatment is performed by using a small liposuction cannula to aspirate fat tissue from the donor site, and then re-injecting the fat into the recipient site with specialized injection cannulas. After harvest, and prior to injection, the fat graft is subjected to a mechanical processing step to separate the aqueous layer and concentrate the adipocytes. This often takes the form of centrifugation or filtering. The main problem with autologous fat grafting is a variable resorption of the graft volume over time. As much as 30-60% of the graft volume can diminish over time. Many variables may influence the behavior of clinical fat grafts, including harvest site, harvest technique, graft preparation, and injection technique. In our current IRB approved study on fat grafting (IRB # PRO09060101), we are seeking to accurately quantify the fat graft resorption over time following a highly standardized surgical technique. Evaluation methods include a 3D surface imaging, high resolution CT scanning, and quality of life measures. This study has enrolled and treated patients without adverse event, and the evaluation methods have been performed successfully. In this proposed study, we plan to use essentially the same surgical procedure and evaluation methods, but with modified preparation of the fat graft. This modified preparation involves concentrating the endogenous stromal cells in the graft material in an effort to increase graft retention over time. The aspirated fat material used for fat grafting consists of mature adipocytes, a small amount of fibrous tissue, and immature adipose stromal cells. These adipose stromal cells (ASCs) are a mixed population of non-lipid laden cells that serve to turn over mature adipocytes and vascular elements. "Preadipocytes," as well as endothelial precursor cells and multilineage progenitor cells, are found. Of note, ASCs have been shown to stimulate angiogenesis when stressed under hypoxic conditions and these cells may be instrumental in healing and volume retention of fat grafts. Yoshimura, et. al. (1) found that fat aspirated with a liposuction cannula (i.e. the method of fat harvest for fat grafting) is deficient in ASCs compared to whole fat. This is due to the fact that a major portion of ASCs are located around larger blood vessels that are left intact in the donor site after liposuction with a blunt cannula.