Stem cells and their potential clinical applications in psychiatric disorders.

The robustness of stem cells is one of the major factors that directly impacts life quality and life span. Evidence has accumulated that changes in the stem cell compartment affect human mental health and serve as an indicator of psychiatric problems. It is well known that stem cells continuously replace differentiated cells and tissues that are used up during life, although this replacement occurs at a different pace in the various organs. However, the participation of local neural stem cells in regeneration of the central nervous system is controversial. It is known that low numbers of stem cells circulate continuously in peripheral blood (PB) and lymph and undergo a circadian rhythm in their PB level, with the peak occurring early in the morning and the nadir at night, and recent evidence suggests that the number and pattern of circulating stem cells in PB changes in psychotic disorders. On the other hand, progress in the creation of induced pluripotent stem cells (iPSCs) from patient somatic cells provides valuable tools with which to study changes in gene expression in psychotic patients. We will discuss the various potential sources of stem cells that are currently employed in regenerative medicine and the mechanisms that explain some of their beneficial effects as well as the emerging problems with stem cell therapies. However, the main question remains: Will it be possible in the future to modulate the stem cell compartment to reverse psychiatric problems?