Introduction. Evidence suggests that the human endometrium contains stem or progenitor cells that are responsible for its remarkable regenerative capability. A common property of somatic stem cells is their quiescent state. It remains unclear whether slow-cycling cells exist in the human endometrium. We hypothesized that the human endometrium contains a subset of slow-cycling cells with somatic stem cell properties. Here, we established an in vitro stem cell assay to isolate human endometrial-derived mesenchymal stem-like cells (eMSC). Methods. Single-cell stromal cultures were initially labeled with fluorescent nanoparticles and a small population of fluorescent persistent cells (FPC) remained after culture of 21 days. Two populations of stromal cells, namely FPC and non-FPC were sorted. Results: Quantitative analysis of functional assays demonstrated that the FPC had higher colony forming ability, underwent more rounds of self-renewal and had greater enrichment of phenotypically defined prospective eMSC markers: CD146<sup>+</sup>/CD140b<sup>+</sup> and W5C5<sup>+</sup> than the non-FPC. They also differentiate into multiple mesenchymal lineages and the expression of lineage specific markers was lower than that of non-FPC. The FPC exhibit low proliferation activities. A proliferation dynamics study revealed that more FPC had a prolonged G<inf>1</inf> phase. Conclusions: With this study we present an efficient method to label and isolate slow-proliferating cells obtained from human endometrial stromal cultures without genetic modifications. The FPC population could be easily maintained in vitro and are of interest for tissue-repair and engineering perspectives. In summary, nanoparticle labeling is a promising tool for the identification of putative somatic stem or progenitor cells when their surface markers are undefined. © 2014 Xiang et al.; licensee BioMed Central Ltd.
Xiang, L., Chan, R. W. S., Ng, E. H. Y., & Yeung, W. S. B. (2014). Nanoparticle labeling identifies slow cycling human endometrial stromal cells. Stem Cell Research and Therapy, 5(4). https://doi.org/10.1186/scrt473