Multiple Differentiation Capacity of STRO-1+/CD146+ Periodontal Ligament Mesenchymal Progenitor Cells

Objectives: Although mesenchymal progenitor cells can be isolated from periodontal ligament (PDL) tissues using stem cell markers STRO-1 and CD146, the proportion of these cells that have the capacity for differentiation into multiple cell lineages remains to be determined. This study was designed to quantify the proportions of primary PDL cells that can undergo multi-lineage differentiation, and to compare the magnitude of these capabilities relative to bone marrow-derived stem cells (MSC) and parental PDL (PPDL) cells.

Methods: PDL mesenchymal progenitor (PMP) cells were isolated from primary human PPDL cells using the markers STRO-1 and CD146. The colony-forming efficiency and multi-lineage differentiation potential of PMP, PPDL, and MSC under chondrogenic, osteogenic and adipogenic conditions were determined by qRT-PCR and immunohistochemistry.

Results: Flow cytometry data showed that on average 2.6% of PPDL cells were STRO-1+/CD146+, whereas more than 63% were STRO-1-/CD146-. Colony-forming efficiency of STRO-1+/CD146+ PMP cells (19.33%) and MSC (16.7%) was statistically higher than that in PPDL cells (6.76%). qRT-PCR data showed that cartilage specific genes, early markers of osteoblastic differentiation, and adipogenic markers were significantly up-regulated under appropriate conditions in PMP cells and MSCs compared to either their non-induced counterparts or induced PPDL cells. Consistent with these findings, immunohistochemistry revealed that cartilaginous macromolecules, mineralized calcium nodules, and lipid vacuoles were substantially accumulated under chondrogenic, osteogenic or adipogenic conditions in PMP and MSC cultures, respectively, compared to their non-induced counterparts or induced PPDL cultures.

Conclusions: The findings show that on average 2.6% of cells derived from human PDL are STRO-1+/CD146+ mesenchymal progenitor cells that could potentially contribute to periodontal regeneration. These PMP cells demonstrate multi-lineage differentiation capacity that is comparable in magnitude to that of MSCs and significantly greater than that of PPDL cells.

(NIH grants R01-DE 01667 to SK and R01-DE013725 to YLK).