Maximum occlusal force tended to increase with age. There was a gender difference in the maximum occlusal force at all age groups, values being larger in the males. In the males, the maximum occlusal force continued to increase until their 20s, while in the females, this increase almost terminated at the age of 17.

Caldecrin/chymotrypsin C is a novel secretory-type serine protease that was originally isolated as a serum calcium-decreasing factor from the pancreas. Previously, we reported that caldecrin suppressed the bone-resorbing activity of rabbit mature osteoclasts (Tomomura, A., Yamada, H., Fujimoto, K., Inaba, A., and Katoh, S. Calcium ions have numerous cellular functions, and serum calcium homeostasis is tightly regulated by the intestines, kidneys, and bones, which are governed by the key systemic hormones, parathyroid hormone, 1␣,25-dihydroxy vitamin D 3 , and calcitonin. Bone is a dynamic serum calciumregulating tissue. Bone formation by osteoblasts involves deposition of minerals, including calcium, and bone resorption by osteoclasts releases calcium from bone (1).We have purified and cloned the serum calcium-decreasing factor caldecrin from the pancreas (2-6). Caldecrin is a secretory-type serine protease that has chymotryptic activity and is also known as chymotrypsin C (EC 3.4.21.2) (8). We originally reported that the administration of caldecrin decreases mouse serum calcium concentration in a dose-dependent manner, and serum calcium decreasing activity is correlated with a decrease in serum hydroxyproline, which is included as a component of collagen and is a marker of bone resorption (2). Interestingly, this does not depend on its protease activity. Furthermore, caldecrin inhibits not only parathyroid hormone-stimulated bone destruction in mouse long bone organ culture but also bone resorption by rabbit mature osteoclasts in vitro (7). Taken together with our previous results, these observations suggest that caldecrin may suppress osteoclast differentiation and/or its activity through as yet unknown mechanisms.Osteoclasts, multinucleated giant cells that have a unique bone resorption activity, are differentiated from hematopoietic cells of the monocyte/macrophage lineage (9 -11). Osteoclast differentiation (osteoclastogenesis) from bone marrow cells (BMCs) 4 requires the cell-to-cell contact of osteoclast progenitor cells with osteoblasts or bone marrow stromal cells. The key molecule for osteoclastogenesis is a member of the tumor necrosis factor family (receptor activator of NF-B ligand (RANKL) (12), also called TRANCE (13)/ODF (14)/OPGL (15)) and is expressed in the osteoblast and bone marrow stro-

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During chronic inflammation from diseases, such as periodontal disease, the proinflammatory cytokines interferon-gamma (IFNγ) and tumor necrosis factor-α (TNFα) alter bone remodeling. To elucidate the underlying molecular mechanisms, we investigated the effect of IFNγ and TNFα on the proliferation and survival of clonal MC3T3-E1 mouse osteoblasts. We found that although IFNγ or TNFα alone affected cell growth and survival only marginally, costimulation with both synergistically inhibited cell growth and reduced cell viability. The diminished cell viability was due to apoptosis, as indicated by increased TUNEL staining and elevated caspase 3, 8, and 9 activities. Western blot also showed that costimulation with IFNγ and TNFα elicited cytochrome c release and downregulated B cell lymphoma 2 (Bcl-2) expression without affecting Bcl-2-associated X (Bax) protein expression. Furthermore, stable Bcl-2 overexpression significantly alleviated cell death following costimulation. Collectively, these results suggested that IFNγ and TNFα elicited osteoblast apoptosis via cytochrome c release from damaged mitochondria, caspase activation, and Bcl-2 downregulation.

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