Title: NG2 Potentiates Prechondroblastic Cell Signaling During Mandibular Condylar Cartilage Development
MAMORU YOTSUYA (Presenter)
University of Illinois at Chicago
Toru Sato, Tokyo Dental College
David Reed, University of Illinois at Chicago
Objectives: Growth in mandibular condylar cartilage (MCC) is dependent upon the coordinated migration, proliferation, and differentiation of prechondroblastic cells in the perichondrium expressing the pro-chondrogenic fibroblast growth factor-2 (FGF2). Nerve glial antigen 2 (NG2) is also expressed in the MCC and has a known binding affinity for FGF2. Here we evaluate the spatiotemporal distribution of NG2 and FGF2 during MCC development and the effects of NG2 signaling on FGF2 and TGF-β expression.
Methods: To evaluated the spatial distribution of NG2 and FGF2 in vivo, temporomandibular tissue was collected from c57 BL/6 mice at 1, 3, 7, 10, 14, and 70 days postnatal, sectioned, and immunohistochemically labeled (IHC; Enzo Multiview Plus). To evaluate NG2 signaling in vitro, primary MCC cells were collected from 10 day postnatal mice, and cultured with and without 300 ng/ml phorbol myristate acetate (PMA) for Protein Kinase C (PKC) mediated phosphorylation of the intracellular domain, and a 1:100 NG2 antibody treatment for competitive binding of the ectodomain. RT-qPCR was performed using primers for NG2, FGF2, and TGF-β.
Results: In vivo IHC data illustrate that NG2 and FGF2 are both tightly localized to the prechondroblastic cell layer in the developing MCC, particularly on the lateral and medial margins. In skeletally mature tissue, NG2 and FGF2 are restricted to the pericellular matrix. In vitro, PMA mediated phosphorylation of the NG2 intracellular domain lowers FGF2 and TGF-β expression (p < 0.05). Competitive NG2 antibody treatment had no effect on FGF2 and TGF-β expression.
Conclusions: These data show NG2 is a marker for prechondroblastic cells in the developing MCC and may interact with matrix associated FGF2. Further, PKC mediated phosphorylation of NG2 attenuates pro-chondrogenic signaling, consistent with published results illustrating that PMA treatment favors a migratory over proliferative cellular phenotype. These data support the hypothesis that NG2 can potentiate pro-chondrogenic signaling in MCC development.