Odontogenic Potential Of Hair Follicle Derived Stem Cells

Morphogenesis and development of tooth initiate from epithelial-mesenchymal interactions,indicating that stem cells of both epithelial and mesenchymal origin should be considered in stem cell based tooth regeneration using tissue engineering approach.Previous studies have demonstrated that tooth germ cells,dental pulp stem cells from adult or deciduous tooth and stem cells from apical papilla have the potential to differentiate into odontoblast lineages and perform the dentinogenesis.However, these cells are very limited and some of them can not be directly isolated from patients themselves in clinical practice.Bone marrow is the only source for non-dental stem cell which can demonstrate odontogenic potential with the induction of oral epithelium from E10 fetal mouse.In addition,the lack of seeding cells for enamel regeneration is always a big rock on the way of tooth regeneration.Recent studies highlighted in stem cells from hair follicle because of their tremendous plasticities and easier accessibility.In this paper,we explored the odontogenic potential of hair-follicle-derived stem cells and main results were listed as follows.PartⅠ.Culturing of hair follicle dermal stem cells and evaluation of their multiple differentiation capacity.Both cultured hair follicle dermal sheath cells and dermal papilla cells demonstrated a larger CFU efficiency and higher reproductive activity compared with interfollicular dermal fibroblasts.Follicle dermal stem cells were heterogeneous and lacking specific surface markers.However,directed differentiation potential of stem cells could be detected with heterogeneous cells which containing stem cells.We found that cultured follicle dermal cells including putative MSCs from aged GFP transgenic mice still presented plasticity, as indicated by the results of multiple differentiation assays.Stem cells from follicle dermal papilla presented a higher ALP activity than those from dermal sheath under the same osteogenic microenvironment.PartⅡ.Odontogenic potential of mesenchymal stem cells from hair follicle dermal papilla.In the in vitro mixed co-culture system containing apical bud cells,GFP labeled follicle dermal papilla cells and dental mesenchymal cells,DSP co-localized with GFP,indicating that some GFP~+ DPCs can differentiate to odontoblasts.These results also suggested that odontogenic microenvironment for non-dental stem cells could be obtained from outside of embryo. Tooth-germ-cell conditioned medium produced by apical bud cells and dental mesenchymal cells could also change the morphology and cell cycle of DPC and further drive these cells to express Dspp and Dmpl genes.PartⅢ.Tissue engineering a pulp-dentin complex using hair follicle dermal papilla cells.We combined an untreated dermal papilla cell pellet with a scaffold which preliminary binded with TGC-CM.Recombinants were cultured under subcutaneous condition of nude mouse.Histological analyses of recoverd explants showed that there was only a small quantity of homogeneous hard tissue instead of typical tubler dentin.Cell pellet of dermal papilla cells treated with TGC-CM preliminary could only form a bone like tissue after cultured in renal capsule for 3 weeks.These results suggested that terminal differentiation of odontoblast is a complicated process which could not accomplished with signaling molecules only.PartⅣ.Possibilty of enamel regeration using hair follicle epithelial stem cells.Outer root-sheath cells were cultured in vitro and demonstrated some typical characteristics of epithelial stem cells.These cells presented a larger CFU efficiency and higher reproductive activity compared with keratinocytes.Keratin 19 and integrinβ1 could be detected in these cells at the same time.We then recombined these cells with dental mesenchymes from first lower molar of E17 SD rats and apical papilla of 7 dpn C57BL/6 GFP transgenic mice.Epithelial cells from the back of E17 SD rats were used as control groups.Results showed that both dental mesenchymes could initiate the ameloblast differentiation of epithelial cells from the back of E17 SD rats.But there were no sufficient experimental evidence showed that hair follicle epithelial stem cells could differentiate to ameloblasts.In summary,our data showed for the first time that mesenchymal stem cells from hair follicle dermal papilla could differentiate to odontoblasts with the induction of dental epithelium from apical bud.Dental mesenchyme from apical papilla of 7 dpn C57BL/6 GFP transgenic mice as well as that from first lower molar of E 17 SD rat could initiate the ameloblast differentiation of epithelial cells from the back of E17 SD rats.We had not found the way to make hair follicle epithelial stem cells differentiate to ameloblasts yet.