Characterization of prostatic stem cells

Recent studies have revealed that a very small subpopulation of multipotent and undiffer-entiated PSCs, comprising about 0.1-3.0% of the total prostatic epithelial cell population, principally reside within specialized areas or "niches" localized in the basal cell layer of acinar and ductal regions of the human prostate gland [5]. Anne T. Collins and colleagues isolated and characterized human adult SCs based on the identity of cell surface integrin antigens [25]. They showed that, in vivo, putative SCs express higher levels of the a2-integrin subunit than other cells within the basal layer. Later, it was shown that a subpopulation of a2p1hi basal cells express the CD133 antigen and that this expression correlates with a high proliferative potential and ability to regenerate a fully differentiated prostatic epithelium with expression of prostatic secretory products in vivo [22]. CD133+ cells possess three important attributes of epithelial stem cells: they are rare, comprise a high in vitro proliferative potential, and are capable of reconstituting highly branched ductal structures. Besides, Patricia E. Burger and colleagues reported that SCs can be purified from isolated proximal duct regions by virtue of their high expression of the cell surface protein stem cell antigen 1 (SCA-1) [26]. Subsequently, it was demonstrated that the Sca-1 surface antigen can be used to enrich for murine prostate cells displaying multiple properties of primitive cells including androgen independence, replication quiescence, multi lineage differentiation, and in vivo prostate regenerative capacity [27]. Combined cell surface markers such as CD45-CD31-Ter119-Sca-1+CD49f+ were defined by Devon A. Lawson and colleagues who found that prostate cells can self-renew to form spheres for many generations and can differentiate to produce prostatic tubule structures containing both basal and luminal cells in vivo. These cells also localize to the putative PSC niche in the proximal region of the prostate gland [28].

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