CD49f is a putative odontogenic epithelial stem cell marker

Objective: Elucidation of the cellular and molecular mechanisms that maintain mouse incisor unlimited growing potential is of broad interest and paramount for the future regenerative therapy. However, analysis of the properties and regulation of odontogenic epithelial stem cells (OESC) has been limited by a lack of well-accepted stem cell marker. The purpose of our study was to identify a stem cell surface marker for isolation and enrichment stem cell derived from mouse incisor cervical loops (CL) where OESC are believed to reside.

Method: We examined the RNA expression profiles in both mouse incisor CL tissue and sphere cells from our newly established OESC culture system. High expression of Sca-1, CD49f, and CD44 were found in the spheres compare to the CL tissue. Fluorescence-activated cell sorting (FACS) analyses of mouse incisor CL and OESC sphere cells with Sca-1, CD49f, and CD44 were also performed. Sphere forming assays with Sca-1, CD49f, and CD44 FACS sorted cells were used for evaluate the self-renewal and differentiation ability of each marker. Immunofluorescent studies were also performed to examine the location of these markers.

Result: FACS analyses of mouse incisor CL and OESC sphere cells based on CD44+ or Sca1+ did not enrich the cells with high sphere-forming activities. In contrast, CD49f+ cells were able to form spheres at a significantly high ratio than CD49f- cells. We also demonstrated that CD49f^Bright subpopulation further enriched the sphere forming cells among the CD49f+ population. CD49f+ cells were able to self-renewal and differentiate into cytokeratin 14, amelogenin expressed, and mineral material producing cells.

Conclusion: The development of an in vitro sphere culture and identifying CD49f^Bright as a stem cell marker for OESC will shed light on understanding the signaling networks to regulate the stem cell maintenance, cell fate, and differentiation.