OBJECTIVETo investigate the effects of allogeneic adipose-derived stem cells (ADSCs) of rat on the early neovascularization of autologous fat transplantation.

METHODS(1) Experiment 1. Adipose tissue was collected from both inguinal regions of two SD rats to isolate, culture, and purify ADSCs through collagen enzyme digestion, density gradient centrifugation, and adherence method. The fourth passage of cells were collected for morphologic observation, detection of expressions of surface markers CD34, CD49d, CD106, and CD45 of ADSCs with flow cytometer, identification of adipogenic and osteogenic differentiation, and determination of the cell proliferation ability with thiazolyl blue method. (2) Experiment 2. Another 30 SD rats were divided into allogeneic adipose granule (AG) group (A, n = 6), autologous AG group (B, n = 8), autologous ADSCs+autologous AG group (C, n = 8), and allogeneic ADSCs+autologous AG group (D, n = 8) according to the random number table. The fourth passage of ADSCs were obtained from adipose tissue from one side of inguinal region of SD rats in group C. Adipose tissue obtained from one side of inguinal region of SD rats of the other 3 groups was abandoned. The AG was prepared from another side of inguinal region of SD rats in the 4 groups. The mixture of 0.6 g AG from one rat and 1 mL DMEM/F12 nutrient solution was injected subcutaneously into the back of another rat in group A, and so on. Autologous AG was injected into its own body of the rats in group B. The mixture of 1 mL autologous ADSCs mixture which contains 3.0 × 10⁶ cells per mililitre autologous ADSCs combined with autologous AG was injected into the rats in group C. The mixture of 1 mL allogeneic ADSCs mixture which contains 3.0 × 10⁶ cells per mililitre ADSCs extractived from the former 2 rats in experiment 1 combined with autologous AG was injected into the rats in group D. At 7 days post transplantation, fat transplants were harvested for gross observation, measurement of wet weight, pathological observation, and assessment of cells with positive expression of CD31 with immunohistochemical method. Data were processed with one-way analysis of variance and SNK test.

RESULTS(1) The fourth passage of cells proliferated well showing fusiform shape similar to fibroblasts. These cells showed positive expression of CD34 and CD49d and weak positive expression of CD106 and CD45. They were able to differentiate into adipocytes and osteoblasts. These cells were identified as ADSCs. The fourth passage of cells grew faster than that of the tenth passage. (2) At 7 days post transplantation, no liquifying necrosis or infection was observed in the fat transplants of the rats in the 4 groups. Wet weight of the fat transplants in groups A and B was respectively (0.25 ± 0.04) and (0.26 ± 0.03) g, which were less than those of groups C and D [(0.36 ± 0.03) and (0.35 ± 0.04) g, with P values below 0.05]. HE staining showed that there were less fat cells and more fibroblasts in the transplants of group A, visible fibrous tissue around uneven shape of fat cells in the transplants of group B, and almost identical size and shape of fat cells and unobvious fibrous tissues were found in the transplants of groups C and D. The cells with positive expression of CD31 were distributed in fibrous tissues in larger number but less around fat cells in the transplants of group A, while more of these cells were observed surrounding fat cells in the transplants of group B. There were more cells with positive expression of CD31 distributed surrounding fat cells in the transplants of groups C and D than that in group B. The cells with positive expression of CD31 observed under 400 times field were more in number in groups C (20.5 ± 1.1) and D (22.1 ± 1.0) than in groups A (8.0 ± 3.6) and B (10.9 ± 1.7), with P values below 0.05.

CONCLUSIONSAllogeneic ADSCs combined with autologous AG can significantly improve the early vascularization of fat transplantation as well as autologous ADSCs combined with autologous AG.