Abstract: Objective：To evaluate the effects of estrogen deficiency on the proliferation and odonto/osteogenic differentiation of rat stem cells from the apical papilla(SCAPs). Methods: Ten 8-week-old female SD rats were randomly divided into two groups, sham-operation group(Sham) and ovariectomized group(OVX), 5 rats in each group. All rats were anesthetized and both ovaries of OVX-rats were gently removed. Sham-operation rats were treated with the same incisions to expose the ovaries but without any hurt to them. One month after the operation, the apical papillae of rat incisors were gently separated and SCAPs were isolated and incubated. Methyl thiazolyl tetrazolium(MTT) assay, alkaline phosphotase(ALP) activity, real-time reverse transcription（RT-PCR）and western blot assay were respectively used to determine the proliferation and odonto/osteogenic differentiation potential of rat SCAPs. Cell pellets of OVX-SCAPs and Sham-SCAPs were respectively transplanted into the renal capsules of immunodeficient female rats. After in vivo culture for 8 weeks, the retrieved implants were processed for hematoxylin and eosin (H & E) staining. Results: MTT results showed that OVX-SCAPs exhibited the decreased proliferative activity as compared with Sham- SCAPs. ALP activity of OVX- SCAPs was lower than that of Sham- SCAPs (P<0.01). Real-time RT-PCR and Western blot results showed that the expression of odonto/osteogenic markers (Dspp/DSP, Osx/OSX, Ocn/OCN) in OVX- SCAPs was significantly inhibited as compared with Sham- SCAPs (P<0.01). Sham-SCAPs implants showed the typical dentin-pulp like complex, while the retrieved implants of OVX-SCAPs exhibited unregular tissue. Conclusions: Estrogen deficiency significantly inhibits the proliferation and odonto/osteogenetic potential of rat SCAPs.

Key words: Estrogen, Stem cells from the apical papilla, proliferation, odonto/osteogenetic differentiation