Risk factors for pannus formation in the post-bariatric surgery population.

BACKGROUND: Previous studies describe a relationship between pannus mass and panniculectomy-related complication rates. Patient management may be improved by elucidating the key factors influencing pannus formation. METHODS: A retrospective review was conducted of 135 patients who had undergone laparoscopic Roux-en-Y gastric bypass from 1996 to 2010 and subsequent panniculectomy. Outcome measures included age, sex, body mass index, time of surgery, resected pannus mass, comorbidities, and panniculectomy-related complications. Nonparametric continuous and nominal variables were assessed using Spearman rank-correlation and Mann-Whitney U tests, respectively. RESULTS: One hundred thirty-five patients (123 women and 12 men; mean age, 44.7 years) were included in analysis. All patients had body contouring surgery more than 1 year after bariatric surgery (median time interval, 2.1 years). Median body mass index at the time of bypass, 1 year after bypass, and at the time of body contouring surgery was 48.7, 30.0, and 29.4 kg/m, respectively. Median pannus mass was 2.2 kg. Larger pannus mass was associated with greater age at gastric bypass surgery (p = 0.034), higher pre-gastric bypass body mass index (p = 0.031), higher prepanniculectomy body mass index (p < 0.001), and longer time interval between gastric bypass and panniculectomy (p = 0.046). Female patients requiring blood transfusions had a significantly larger pannus mass than those who did not (p = 0.048). CONCLUSION: Performing bariatric surgery on patients at a younger age or having patients reduce body mass index as much as possible before bariatric surgery may be useful for minimizing symptomatic pannus formation and in turn may decrease rates of panniculectomy-related complications. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, III.

Prevalence of endogenous CD34+ adipose stem cells predicts human fat graft retention in a xenograft model.

BACKGROUND: Fat grafting is a promising technique for soft-tissue augmentation, although graft retention is highly unpredictable and factors that affect graft survival have not been well defined. Because of their capacity for differentiation and growth factor release, adipose-derived stem cells may have a key role in graft healing. The authors' objective was to determine whether biological properties of adipose-derived stem cells present within human fat would correlate with in vivo outcomes of graft volume retention. METHODS: Lipoaspirate from eight human subjects was processed using a standardized centrifugation technique and then injected subcutaneously into the flanks of 6-week-old athymic nude mice. Graft masses and volumes were measured, and histologic evaluation, including CD31+ staining for vessels, was performed 8 weeks after transplantation. Stromal vascular fraction isolated at the time of harvest from each subject was analyzed for surface markers by multiparameter flow cytometry, and also assessed for proliferation, differentiation capacity, and normoxic/hypoxic vascular endothelial growth factor secretion. RESULTS: Wide variation in percentage of CD34+ progenitors within the stromal vascular fraction was noted among subjects and averaged 21.3 ± 15 percent (mean ± SD). Proliferation rates and adipogenic potential among stromal vascular fraction cells demonstrated moderate interpatient variability. In mouse xenograft studies, retention volumes ranged from approximately 36 to 68 percent after 8 weeks, with an overall average of 52 ± 11 percent. A strong correlation (r = 0.78, slope = 0.76, p < 0.05) existed between stromal vascular fraction percentage of CD34+ progenitors and high graft retention. CONCLUSION: Inherent biological differences in adipose tissue exist between patients. In particular, concentration of CD34+ progenitor cells within the stromal vascular fraction may be one of the factors used to predict human fat graft retention.

VEGF microsphere technology to enhance vascularization in fat grafting.

Vascularization is crucial for implantation of engineered tissues in reconstructive surgery. Polypeptides encapsulated in microspheres can be efficiently transported to their site of action and released in a sustained dosage. We evaluated the effect of delivering vascular endothelial growth factor (VEGF)-encapsulated microspheres in a lipoaspirate scaffold on vascularization and tissue survival. The VEGF-loaded (n=6) and empty (n=6) poly(lactic-co-glycolic acid) microspheres in human lipoaspirate and the human lipoaspirate alone (n=6) were injected subcutaneously into the flanks of athymic nude mice. Three mice from each group were killed, and grafts were explanted at weeks 3 and 6. Increases in mass and volume of VEGF samples, as well as decreases in empty and lipoaspirate-only samples, were observed at 3 and 6 weeks, reaching statistical significance at 6 weeks. Hematoxylin and eosin and CD31+ imaging demonstrated significantly greater vascularization in VEGF samples than in both the empty and lipoaspirate-only groups at both 3 and 6 weeks.