Cell Tissue Res. 2007 Apr 19; [Epub ahead of print]

Human dental follicle cells acquire cementoblast features under stimulation by BMP-2/-7 and enamel matrix derivatives (EMD) in vitro.

    Kemoun P, Laurencin-Dalicieux S, The dental follicle (DF) surrounding the developing tooth germ is an ectomesenchymal tissue composed of various cell populations derived from the cranial neural crest. Human dental follicle cells (HDFC) are believed to contain precursor cells for cementoblasts, periodontal ligament cells, and osteoblasts. Bone morphogenetic proteins (BMPs) produced by Hertwig's epithelial root sheath or present in enamel matrix derivatives (EMD) seem to be involved in the control of DF cell differentiation, but their precise function remains largely unknown. We report the immunolocalization of STRO-1 (a marker of multipotential mesenchymal progenitor cells) and BMP receptors (BMPR) in DF in vivo. In culture, HDFC co-express STRO-1/BMPR and exhibit multilineage properties. Incubation with rhBMP-2 and rhBMP-7 or EMD for 24 h increases the expression of BMP-2 and BMP-7 by HDFC. Long-term stimulation of these cells by rhBMP-2 and/or rhBMP-7 or EMD significantly increases alkaline phosphatase activity (AP) and mineralization. Expression of cementum attachment protein (CAP) and cementum protein-23 (CP-23), two putative cementoblast markers, has been detected in EMD-stimulated whole DF and in cultured HDFC stimulated with EMD or BMP-2 and BMP-7. RhNoggin, a BMP antagonist, abolishes AP activity, mineralization, and CAP/CP-23 expression in HDFC cultures and the expression of BMP-2 and BMP-7 induced by EMD. Phosphorylation of Smad-1 and MAPK is stimulated by EMD or rhBMP-2. However, rhNoggin blocks only Smad-1 phosphorylation under these conditions. Thus, EMD may activate HDFC toward the cementoblastic phenotype, an effect mainly (but not exclusively) involving both exogenous and endogenous BMP-dependent pathways.

人类牙囊细胞经BMP-2/-7 和EMD体外诱导后表现出成牙骨质细胞特性

 牙囊是包绕牙胚周围的间充质组织，它由颅神经嵴来源的多种细胞成份组成。一般认为，牙囊细胞包含成牙骨质细胞、牙周膜细胞和成骨细胞的前体细胞。有上皮根鞘产生或存在于EMD中的BMPs可以调控牙囊细胞分化，但是其确切的功能还不清楚。我们研究发现，在体内牙囊组织有STRO-1 和BMPR的表达。体外培养牙囊细胞共表达STRO-1 和BMPR,并表现出多向分化特性。使用rhBMP-2 和rhBMP-7 或 EMD诱导牙囊细胞24小时，可以升高其BMP-2和BMP-7的表达。如果进行长期诱导，则可以显著增加细胞碱磷酶活性和矿化能力。在经过EMD诱导的整个牙囊组织以及经rhBMP-2 和rhBMP-7 或 EMD诱导的牙囊细胞中，均表达作为成牙骨质细胞标志的CAP和CP-23。RhNoggin是BMP的拮抗剂，可以抑制上述经诱导的牙囊细胞的碱磷酶活性，矿化和CAP/CP-23表达。然而，rhNoggin只阻断Smad-1磷酸化。因此，EMD诱导牙囊细胞向成牙骨质细胞分化，主要而并非唯一的途径就是内源性和外源性BMP依赖通路。