Regenerative therapeutic effects of conditioned medium from human umbilical cord‑derived mesenchymal stem cells as an adjuvant to insulin therapy in a rat model of type 2 diabetes

Standard therapies for type 2 diabetes (T2DM) that utilize anti‑diabetic drugs and insulin are well established; nevertheless, the incidence of complications and mortality associated with the disease remain relatively high. Conditioned medium (CM) from human umbilical cord‑derived mesenchymal stem cells (hUC‑MSCs) has demonstrated regenerative effects, although these have yet to be properly investigated for the purposes of managing T2DM. Therefore, the present study aimed to evaluate the therapeutic potential of CM from hUC‑MSCs in various animal models of T2DM. T2DM was established in rats using a high‑fat diet and streptozotocin, and the rats were subsequently injected with insulin, CM or insulin + CM two times per week (subcutaneously for insulin; intraperitoneally for CM) over a 4‑week period. Blood glucose levels were measured prior to each treatment up until 2 weeks after the final injection. At the end of the experiment, glucose tolerance, insulin sensitivity and the levels of glycated hemoglobin (HbA1c), serum insulin and insulin‑like growth factor‑1 (IGF‑1) were measured. Histological analyses of pancreatic tissues were also performed, and the findings were compared among the groups. The CM‑treated group was found to exhibit significantly improved levels of blood glucose, glucose tolerance and insulin sensitivity, whereas administering a combination of CM and insulin therapy to the rats led to even more robust effects in terms of blood glucose level management and reducing the level of HbA1c compared with the other treatment groups. CM treatment also led to an improvement in the IGF‑1 serum level, although this was found to be reduced in the other diabetic groups. Furthermore, both the numbers of β‑cells and their capability to secrete insulin were enhanced in the CM‑treated group. Taken together, these findings underscore the regenerative effect of CM from hUC‑MSCs in terms of T2DM therapy.