Role of D1 and E Cyclins in Cell Cycle Progression of Human Fibroblasts Adhering to Cementum Attachment Protein

Abstract

Cementum attachment protein (CAP) is a collagenous protein present in the matrix of tooth cementum that mediates preferential attachment of some mesenchymal cell types, and CAP binding capacity is related to mineralizing tissue-forming capacity in culture. We have examined if adhesion to surfaces containing CAP as the only attachment protein permits human fibroblasts to escape G 1 arrest and synthesize DNA, and if adhesion to CAP modulates the levels of cyclins D 1 and E. Human gingival fibroblasts (HGFs) were serum-starved, trypsinized, and added to plates coated with CAP or bovine serum albumin (BSA). Cells were then exposed to either 10% fetal bovine serum (FBS) or to cementum-derived growth factor (CGF), an insulin-like growth factor I (IGF-I)-like molecule sequestered in tooth cementum, plus epidermal growth factor (EGF). DNA synthesis was measured as [ 3 H]thymidine uptake, and cyclin D 1 and E levels were determined by Western analysis. Cyclin E-dependent kinase (Cdk) activity was assessed in terms of H1 kinase activity in immunoprecipitates of cyclin E. Cells adhering to CAP synthesized DNA, whereas on BSA they remained unattached and did not synthesize DNA. Protein levels of cyclin D 1 were higher in cells adhering to CAP in the absence and presence of growth factors. Cyclin E levels were not affected by adhesion alone, but they increased in the presence of growth factors. Cyclin E-associated kinase activity was higher in cells adherent on CAP, and it increased further in the presence of growth factors. Our results indicate that adhesion to CAP increases cyclin D 1 levels and cyclin E-associated Cdk activity, and that these increases contribute to cell cycle progression. We previously observed that the signaling reactions induced during adhesion are characteristic of the CAP; together these observations indicate that specific matrix components present in the local environment can contribute to recruitment and differentiation of specific cell types for normal homeostasis and wound healing.

Apical tooth germ cell‐conditioned medium enhances the differentiation of periodontal ligament stem cells into cementum/periodontal ligament‐like tissues

“…Second, analysis by flow cytometry and BrdU incorporation showed that many PDLSCs tend to escape G0G1 arrest and traverse the cell cycle in the presence of APTG‐CM. This result is consistent with a previous report from Yokokoji (46), in which it was shown that cementum matrix may permit human fibroblasts to escape cell cycle arrest and complete cell division and differentiation, and indicates that APTG‐CM may provide a proper microenvironment which contains multiple molecular signals necessary for the proliferation and differentiation of PDLSCs. In parallel with determining the effects of APTG‐CM on morphological appearance and cell proliferation, our study also provided evidence that PDLSCs exposed to APTG‐CM showed high ALP activity, calcified nodule formation and the expression of mineralization‐related genes, including genes for COLI, ALP, OCN, BSP and CP‐23.…”

Cementum proteins: role in cementogenesis, biomineralization, periodontium formation and regeneration

“…Cell attachment to cementum attachment protein induces immediate‐early G 1 phase events, and cyclin D 1 levels increase in the cells adhered to cementum attachment protein alone, even without growth factors. The expression of cyclin D1 is regulated by adhesion in the presence of growth factors, and signal reactions generated by binding cementum attachment protein to cementum attachment protein receptors induce expression of cyclin D1 . Cementum attachment protein affects cell‐cycle progression through mechanisms that are common to other molecules.…”

Cementum and Periodontal Wound Healing and Regeneration

“…3). For example, cells can escape cell cycle arrest and complete cell division and differentiation in the presence of cementum proteins alone (Yokokoji and Narayanan, 2001). Needed molecules may also be present in enamel matrix extracts, although in this case the active components may or may not be the same as those of the cementum matrix.…”