Isolation and Validation of Podoplanin-positive Mesenchymal Stem Cell Subpopulations Using an Indirect Magnetic Bead Strategy.

The study of functional heterogeneity in mesenchymal stem cells relies on the efficient isolation of specific subpopulations (e.g., podoplanin (PDPN)-positive cells). However, for most membrane protein targets, directly available commercial magnetic beads for sorting are limited. To address this, our laboratory has established and tested a standardized magnetic bead sorting protocol based on the indirect coupling principle of "phycoerythrin (PE)-labeled flow cytometry antibodies/anti-PE magnetic beads." Using PDPN-positive cells as a model target population, this protocol enriches a target cell fraction without relying on expensive flow cytometric cell sorters. Researchers can use compatible PE-labeled flow cytometry antibodies targeting accessible cell-surface proteins and combine them with commercially available anti-PE microbeads to establish a sorting workflow for selected targets after target-specific optimization. This approach avoids the lengthy lead times and high costs associated with customizing or ordering target-specific magnetic beads for each new target, making it particularly suitable for accessible surface markers that are rare or understudied. In the PDPN model system tested here, the protocol enabled enrichment of the target subpopulation with high post-sort PDPN positivity and preserved CCK-8-based proliferation/metabolic activity compared with unsorted MSCs.