A tag-less method of sorting stem cells from clinical specimens and separating mesenchymal from epithelial progenitor cells.

Background: The interest in stem cell (SC) isolation from easily accessible clinical specimens is booming. The lack of homogeneity in pluri/multipotent SC preparation blurs standardization, which however is recommended for successful applications. Multipotent mesenchymal SCs (MSCs) in fact express a broad panel of surface antigens, which limit the possibility of sorting homogeneous preparations by using an immunotag-based method.

Methods: We present a tag-less, flow-assisted method to purify, distinguish, and sort pluri/multipotent SCs obtained from clinical specimens, based on differences in the biophysical properties that cells acquire when in suspension under fluidic conditions. A suspension of cells in a transport fluid is injected into a ribbon-like capillary device by continuous flow. In a relatively short time (about 30 min), sorted cells are collected.

Results: We obtained baseline separation between MSCs and epithelial cells, which are important contaminants of isolated MSCs. The extent of separation is evaluated by flow cytometry through detection of a specific epithelial antigen. MSCs from various human sources also prove to have different, characteristic, highly-reproducible fractionation profiles. Finally, we evaluated the dissimilar differentiation potential among cell fractions obtained from sorting a single MSC source. After differentiation induction, a fraction displayed a differentiation yield close to 100%, whereas unfractionated cells contained only 40% of responding cells.

Conclusions: The results demonstrate that the method presented is able to obtain selected and well-characterized living MSCs with an increased differentiation yield. Its reduced cost, full biocompatibility, and scale-up potential could make this method an effective procedure for stem cell selection.