Application of Epineural Sheath For Fat Graft Volume Maintenance
Safak Uygur, MD, Grzegorz Kwiecien, MD, Adam Bobkiewicz, MD, Maria Madajka, PhD, Maria Siemionow, MD.
Cleveland Clinic, Cleveland, OH, USA.
PURPOSE: The mechanism of fat graft survival is still not known. The goal of this project was to develop and test the epineural sheath as a new protective material for fat volume maintenance. We have confirmed the presence of proangiogenic markers and semipermeability of the epineural sheath. We hypothesize that implantation of fat graft into epineural sheath tube and fat coverage with epineural patch will maintain fat volume
METHODS: The efficacy of epineural sheath in fat volume maintenance was tested in Lewis rat model. Five experimental groups were created (n=20): Group 1: Fat graft without coverage (control); Group 2: Epineural tube filled with fat graft; Group 3: Fat graft mixed with minced epineural sheath; Group 4: Epinueral tube alone; Group 5: Fat graft covered with epineural sheath patch. All grafts were implanted into the dorsal subcutaneous region of the rat and were followed for 1, 3, 6 and 12 weeks, when samples were obtained for histological evaluation.
A 3 cm long segment of sciatic nerve was harvested and empty epineural tube was created. The branches of sciatic nerve were used to create minced epineural sheath. Epineural sheath patches for Group 5 and epineural tubes for Group 4 were obtained from the isogenic donors. The adipose tissue was extracted from the gluteal region of the rat. Each graft was weighed to compare fat graft volume before implantation and at the end of each follow-up period.
RESULTS: In groups 1 and 3, grafts lost over 25% of their weight at 1-st week, over 50% of at 3-rd week and 100% of weight was lost at 6-th week post-implantation. The weight of fat graft within the epineural sheath tube (Group 2) and the weight of epineural tube alone were maintained up to 12 weeks post-implantation. The weight of fat graft within the epineural patch was maintained up to 6 weeks but 50% of fat weight loss was observed between 6 and 12 weeks. Epineural sheath tube and patches were intact and no leakage of fat graft was observed. Based on H&E staining, normal structure and integrity of the fat filled epineural tube was preserved up to12 weeks after implantation. Fat was equally distributed inside the tube. No signs of epineural sheath perforation were observed. The diameter of the epineural tube was preserved through the entire length of the tube.
CONCLUSION: This study has shown that both the epineural tubes and epineural patches maintain 100% and 50 % respectively of fat graft volume at 12 weeks post-implantation. In contrast, fat graft implantation without epineural sheath coverage showed 100 % fat absorption at 12 weeks follow up. The integrity of fat graft as well as epineural sheath structure was confirmed by histology. This is the first report presenting 100 % of fat graft maintenance at 12 weeks post-implantation. The role and mechanism of epineural sheath in fat volume maintenance is currently investigated.
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