Primary Genes Promoting Cementoblast Differentiaton

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DESCRIPTION (provided by applicant): Periodontal regeneration is an important, yet unattainable, treatment objective in dentistry. Developing better regenerative treatments requires a deeper understanding of cementoblast, osteoblast, and PDL fibroblast biology. The recently established OC-CM cementoblastic cell line provides an invaluable research tool for studying cementoblast molecular biology. We found that prostaglandin (PG) E2 and fluprostenol (flup; a specific FP receptor agonist) promoted, while interleukin-1 (IL-1) inhibited, OC-CM mineralization and differentiation. These effects were reproducible in primary human cementoblasts. Mechanistically, receptor bound flup and IL-1 induce primary genes, which regulate downstream genes and ultimately control cell function. Some primary genes are induced by both flup and IL-I, while others are preferentially induced by each treatment. We hypothesize that preferentially induced primary genes dictate flup- and IL-l-regulated cementoblast function. To identify primary genes we performed subtraction hybridization using OC-CM cells treated with 0.1 (M flup or 10 ng/ml IL-1 for 90 min. Two cDNA subtractions were performed: (a) flup - IL-l, to identify flup-induced genes and (b) IL-1 - flup, to identify IL-l-induced genes. Several preferentially induced primary genes were identified. Our objective is to study the role of the transcription factors Nur77 and egr1, and the MAP kinase signaling regulator mkp1 in cementoblast function. In preliminary studies, mRNA from all three genes was rapidly and transiently induced by flup, but not by IL-1, in OC-CM cells. This temporal pattern of Nur77, egr1, and mkp1 mRNA expression was replicated in primary human cementoblasts and primary mouse osteoblasts treated with flup. We propose three Specific Aims: 1) to characterize Nur77, egr1, and mkp1 gene regulation by prostanoids in cementoblasts, 2) to characterize Nur77, egr1, and mkp1 protein involvement in regulating cementoblast gene expression and differentiation, and 3) to examine PGE2 and PGF2alpha induction of Nur77, egr1, and mkp1 gene expression in cementoblasts in vivo. We anticipate that Nur77, egr1, and mkp1 will be key mediators of cementoblast differentiation. These studies will contribute to our understanding of the molecular signals that regulate cementoblast function.