CD133+ renal stem cells always co-express CD24 in adult human kidney tissue

We (Angelotti et al., 2012; Romagnani et al., 2013; Ronconi et al., 2009; Sagrinati et al., 2006) and others (Lindgren et al., 2011; Sallustio et al., 2013) previously demonstrated that in fresh renal tissue, adult human kidneys contain a population of renal stem and more committed progenitor cells characterized by co-expression of surface markers CD133 and CD24. These cells can be expanded in culture while maintaining their phenotype, and they exhibit self-renewal potential as well as the capacity to differentiate into podocytes and tubular cells both in vitro and in vivo (Angelotti et al., 2012; Lindgren et al., 2011; Romagnani et al., 2013; Ronconi et al., 2009; Sagrinati et al., 2006; Sallustio et al., 2013). Consistently, CD133+ renal cells represent a subset of CD24+ cells during human kidney development, when they constitute the metanephric mesenchyme-derived primordial nephron (Lazzeri et al., 2007). In their manuscript published in the August issue of Stem Cell Research, Bombelli et al. describe the isolation of putative novel renal stem cells by culturing nephrosphere suspensions from adult human kidneys (Bombelli et al., 2013). Based on our previous studies,