Subcutaneous transplantation of human BMMSCs extends life span in immunocompromised mice. (A) Kaplan-Meier analysis of survival. Recipient mice transplanted with subcutaneous human BMMSC using HA/TCP as a carrier vehicle (Transplant, n = 13) manifested a significantly increased life span compared with age-matched control immunocompromised mice (Control, n = 20; P < .05). (B) The natural aging phenotype of human kyphosis was observed in 6 of 9 aging control mice, shown here as extreme curvature of the vertebrae and tail, although not in transplantation mice (n = 15). (C) Body weight at indicated months showed no significant difference between control and transplant recipients. Bars represent the means. (D) When human skin fibroblasts were transplanted subcutaneously using HA/TCP as a carrier (HA/TCP/FB), there is no increased life span in the recipients (n = 10; P = .391). (E) Newly formed bone (B) and bone marrow (BM) were found in the BMMSC transplants (Transplant) at 8 weeks after transplantation. However, the fibroblast group (HA/TCP/FB) failed to form new tissue and only showed connective tissue (CT) around HA/TCP particles (HA) by hematoxylin and eosin staining. (F) When human BMMSCs (10⁶) were infused into immunocompromised mice (n = 12) via tail vein, there was no consistent increase in life span extension (P > .05) compared with the control group.