Chapter 12 - Very Small Embryonic-like Stem Cells and Their Potential Relevance for Kidney Homeostasis

Abstract

Continuous tissue and organ regeneration is one of the important homeostatic mechanisms of the multicellular organism. The senescent, functionally differentiated mature cells in adult organs are continuously being replaced by new ones. This cell turnover is more rapid in the hematopoietic system, intestinal epithelium, and epidermis than in the kidney, skeletal muscles, liver, and heart. Old or senescent cells in adult organisms are eliminated by various mechanisms. Thus, to keep a cell mass balance in different tissues and organs, new cells have to be generated continuously to replace eliminated ones. The new cells are supplied by a pool of tissue-committed stem cells (TCSCs) that reside in specific niches spread throughout the organs and tissues. The novel hypothetical concept presented in this chapter addresses data that support the residence of some very primitive pluripotent stem cells (PSCs) in adult tissues with the ability to differentiate into multiple types of TCSCs. The similar or overlapping populations of primitive stem cells in adult tissues were detected using various experimental strategies and, subsequently, were assigned different names. However, it is an important challenge to understand the biological significance of these primitive stem cells residing in adult tissues. Finally, it is important to explore in future the relationship between VSELs and TCSCs from the enopoietic system located in Bowman's capsule.