Preliminary evaluation and mechanism of adipose-derived stem cell transplantation from allogenic diabetic rats in the treatment of diabetic rat wounds

Objective To investigate whether adipose-derived stem cells (ASCs) from allogeneic diabetic rats can promote wound healing in diabetic rats or not and the mechanism. Methods (1) Fifty-six male Wistar rats aged 12-16 weeks were divided into diabetic group and healthy group according to the random number table (the same grouping method below), with 28 rats in each group. Rats in healthy group were not treated with any treatment. Rats in diabetic group were injected with 10 g/L streptozotocin 60 mg/kg intraperitoneally in one time to establish the diabetic model. Four rats in diabetic group and 4 rats in healthy group were selected according to the random number table, and the adipose tissue in the inguinal region was taken to culture and purify ASCs, so as to obtain healthy rat-derived ASCs (hereinafter referred to as nASCs) and diabetic rat-derived ASCs (hereinafter referred to as dASCs). The third passage of nASCs (n=3) and dASCs (n=3) were taken, and the positive expression rates of cell surface differentiation antigens CD105, CD31, CD34, and CD44 were detected with flow cytometer for defining ASCs purity. (2) The rest 24 rats in healthy group and 24 rats in diabetic group were used to make three round full-thickness skin defect wounds with a diameter of 12 mm on the back of each rat. Immediately after injury, phosphate buffer saline (PBS), nASCs of 2×10⁷/mL, and dASCs of 2×10⁷/mL each in the volume of 0.5 mL were subcutaneously injected into three wounds and their margins of each rat, respectively. On post injury day (PID) 1, 3, 7, and 12, 6 rats in each group were selected according to the random number table to calculate the wound area, and the wound tissue was stained with hematoxylin-eosin to observe the histological morphology of the wound. (3) Human ASCs (hASCs) were subcultured, and the 4th to 7th passage of cells were used for the subsequent experiments. The hASCs were divided into 7 groups, with 12 samples in each group. Cells in blank control group were cultured with mesenchymal stem cell culture medium, and cells in simple advanced glycation end products (AGEs) group, simple protein group, simple high glucose group, simple high osmotic pressure group, AGEs-high glucose combination group, and protein-high osmotic pressure combination group were cultured with mesenchymal stem cell culture medium containing a final mass concentration of 100 mg/L AGEs, 100 mg/L bovine serum albumin (BSA), 28 mmol/L D-glucose, 28 mmol/L mannitol, 100 mg/L AGEs+ 28 mmol/L D-glucose, 100 mg/L BSA+ 28 mmol/L mannitol, respectively. Cell proliferation was detected by cell counting kit 8 at post culture hour (PCH) 2 and on post culture day (PCD) 2, 4 and 6. (4) The hASCs were divided into blank control group, simple AGE group, simple high glucose group, and AGE-high glucose combination group, with 12 samples in each group, which were treated the same as corresponding groups in experiment (3). On PCD 0, 2, 4, and 6, the positive expression rates of cell surface differentiation antigens CD105, CD44, and CD45 were detected by flow cytometer to estimate their homeostasis. (5) The hASCs were divided into AGE-high glucose combination group and protein-high osmotic pressure combination group, with 9 samples in each group, which were treated the same as corresponding groups in experiment (3). On PCD 2, 4, and 6, the expression of intracellular protein was detected by cyanine 3-streptavidin double-antibody sandwich technique. Data were processed with analysis of variance for factorial design, least significant difference test, and Bonferroni correction. Results (1) The positive expression rates of CD44 in nASCs and dASCs were both higher than 96%, the positive expression rates of CD31 and CD34 were low, and the positive expression rates of CD105 were about 40%, which basically met the purity requirements. (2) The areas of wounds treated by three methods in rats of healthy group and diabetic group were similar on PID 1 (P>0.05). In healthy group, compared with (0.682 1±0.078 9), (0.314 3±0.113 7), and (0.064 3±0.002 1) cm² of the PBS-treated wounds in rats, the area of nASCs-treated wounds in rats decreased significantly on PID 3, 7, and 12 [(0.464 1±0.092 6), (0.223 9±0.072 7), and (0.034 3±0.012 5) cm², P<0.05], the area of dASCs-treated wounds in rats decreased significantly on PID 3 and 12 [(0.514 1±0.124 1) and (0.043 7±0.032 8) cm², P<0.05] but was not obviously changed on PID 7 [(0.274 2±0.062 5) cm², P>0.05]. Compared with those of the dASCs-treated wounds of rats within the same group, the area of the nASCs-treated wounds of rats in healthy group decreased significantly on PID 3 and 7 (P<0.05) but was not obviously changed on PID 12 (P>0.05). In diabetic group, compared with (0.853 5±0.204 8), (0.670 5±0.164 8), and (0.131 4±0.074 4) cm² of the PBS-treated wounds in rats, the area of nASCs-treated wounds in rats decreased significantly on PID 3, 7, and 12 [(0.633 4±0.132 5), (0.331 8±0.023 5), and (0.074 2±0.003 8) cm², P<0.05], the area of dASCs-treated wounds in rats decreased significantly on PID 3 [(0.773 6±0.182 2) cm², P<0.05] but was not obviously changed on PID 7 and 12 [(0.510 6±0.192 2) and (0.114 4±0.003 1) cm², P>0.05]. Compared with the dASCs-treated wounds of rats within the same group, the area of the nASCs-treated wounds of rats in diabetic group was not obviously changed on PID 3 and 7 (P>0.05) but decreased significantly on PID 12 (P<0.05). There was no obvious difference in histological morphology of the wounds treated with three methods in rats of each group on PID 1. On PID 3, a small amount of microvessels were formed in the wounds treated with nASCs and dASCs of rats in both groups, but microvessel formation was almost undetected in the PBS-treated wounds. On PID 7, more small blood vessels and fibroblasts (Fbs) were observed in the wounds treated with nASCs and dASCs of rats in both groups, but the small blood vessels and Fbs were slightly less in the PBS-treated wounds. On PID 12, the wounds treated with nASCs and dASCs of rats in the two groups were covered by epithelial tissue, the granulation tissue in the PBS-treated wounds of rats in healthy group was not obvious, and the PBS-treated wounds of rats in diabetic group were not completely epithelialized. (3) Compared with those of blank control group, the cell number of hASCs in simple AGEs group decreased significantly on PCD 2, 4, and 6 (P<0.05), which increased significantly on PCD 2 and 4 in simple high glucose group (P<0.05), and that in AGEs-high glucose combination group decreased significantly on PCD 4 and 6 (P<0.05). (4) Compared with that on PCD 4 within the same group, the positive expression rate of CD105 in hASCs decreased significantly in blank control group, simple AGEs group, and AGEs-high glucose combination group on PCD 6 (P<0.05). The positive expression rate of CD44 was higher than 95%, and that of CD45 was less than 2% in hASCs of each group at each time point. (5) Detection values of 7 proteins were located in the confidence interval. The expression levels of basic fibroblast growth factor and tissue inhibitor of metalloproteinase-1 in hASCs of AGEs-high glucose combination group and protein-high osmotic pressure combination group showed increasing trend with the prolongation of culture time. The expression level of human monocyte chemoattractant protein 1 (MCP-1) in hASCs of AGEs-high glucose combination group showed increasing trend with the prolongation of culture time, while the expression level of growth-regulated oncogene (GRO) on PCD 6 was significantly higher than that on PCD 4 within the same group (P<0.05); the expression levels of MCP-1 and GRO in hASCs of protein-high osmotic pressure combination group showed decreasing trend with the prolongation of culture time. The expression level of follistatin in hASCs of protein-high osmotic pressure combination group decreased obviously on PCD 4, while that in hASCs of AGEs-high glucose combination group was significantly lower on PCD 6 than that on PCD 4 (P<0.05). The expression level of vascular endothelial growth factor (VEGF) in hASCs of protein-high osmotic pressure combination group decreased gradually with the prolongation of culture time, while that in hASCs of AGEs-high glucose combination group on PCD 4 decreased significantly as compared with that on PCD 2 (P<0.05). The expression level of urokinase-type plasminogen activator receptor in hASCs of protein-high osmotic pressure combination group on PCD 6 was significantly higher than that on PCD 4 within the same group (P<0.05) and that of AGEs-high glucose combination group on PCD 6 (P<0.05). Conclusions Both nASCs and dASCs can promote wound healing in rats with simple defect injury, but dASCs have no significant effect on wound healing in rats with diabetes mellitus, which may be related to the inhibition of ASCs proliferation and the influence of high glucose and AGEs intervention on their homeostasis and secretory function.