Human histocompatibility antigens are quite heterogeneous and promote the 
rejection of transplanted tissue. Recent advances in stem cell research that 
enable the use of a patient's own stem cells for transplantation are very 
important because rejection could be avoided. In particular, Yamanaka's group in 
Japan gave new hope to patients with incurable diseases when they developed 
induced murine pluripotent stem cells (iPSCs) in 2006 and human iPSCs in 2007. 
Whereas embryonic stem cells (ESCs) are derived from the inner cell mass and are 
supported in culture by LIF, iPSCs are derived from fetal or adult somatic 
cells. Through the application of iPSC technology, adult somatic cells can 
develop a pluripotent state. One advantage of using iPSCs instead of ESCs in 
regenerative medicine is that (theoretically) immune rejection could be avoided, 
although there is some debate about immune rejection of a patient's own iPSCs. 
Many diseases occur in elderly patients. In order to use regenerative medicine 
with the elderly, it is important to demonstrate that iPSCs can indeed be 
generated from older patients. Recent findings have shown that iPSCs can be 
established from aged mice and aged humans. These iPSCs can differentiate to 
cells from all three germ layers. However, it is not known whether iPSCs from 
aged mice or humans show early senescence. Before clinical use of iPSCs, issues 
related to copy number variation, tumorigenicity and immunogenicity must be 
resolved. It is particularly important that researchers have succeeded in 
generating iPSCs that have differentiated to somatic cells related to specific 
diseases of the elderly, including atherosclerosis, diabetes, Alzheimer's 
disease and Parkinson's disease. These efforts will facilitate the use of 
personalized stem cell transplantation therapy for currently incurable diseases.