Effect of Concentrating Endogenous Stromal Cells in the Fat Graft

Overview

Traumatic facial injuries, especially those sustained in military combat, are characterized by destruction of bone and soft tissue. While the bony structures of the face can be reconstructed, it is difficult to return the soft tissue back to its original form. Many times, fat grafting, a common cosmetic and reconstructive procedure, is used in hopes of improving the soft tissue deformity. Fat grafting is a procedure in which a person's own fat is taken from areas throughout the body, usually the thighs or abdomen, with a small liposuction tube. The fat is then transferred into the area that has lost volume or fullness. The fullness of the soft tissue area may decrease over time because the transferred fat can be reabsorbed by the body. Altering the current fat grafting procedure, slightly, could lead to less reabsorption and a lasting fullness of the soft tissue area outcome of the fat graft procedure. We are conducting this research study to help us improve the surgical treatment of people who have suffered facial soft tissue loss as a result of trauma. The goal of this research study is to see how each person's fat grafts will maintain the fat over time and to measure the quality of life during a 9 month post-surgical follow-up period. The total duration of participation is approximately 11 months. In this study, we will concentrate the fat in the fat grafting procedure to determine whether this process will maintain the fat over time. The areas treated with enhanced fat grafts will be compared with areas treated with standard of care fat grafts. At least two areas of your face will be treated with fat grafts, (standard of care fat grafts and concentrated fat grafts).

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.