CTSK blocking peptide

Background: The bone-bone marrow interface is an area of the bone marrow microenvironment in which both bone remodeling cells, osteoblasts and osteoclasts, and hematopoietic cells are anatomically juxtaposed. The close proximity of these cells naturally suggests that they interact with one another, but these interactions are just beginning to be characterized. Methodology/Principal Findings: An Id1(-/-) mouse model was used to assess the role of Id1 in the bone marrow microenvironment. Micro-computed tomography and fracture tests showed that Id1(-/-) mice have reduced bone mass and increased bone fragility, consistent with an osteoporotic phenotype. Osteoclastogenesis and pit formation assays revealed that loss of Id1 increased osteoclast differentiation and resorption activity, both in vivo and in vitro, suggesting a cell autonomous role for Id1 as a negative regulator of osteoclast differentiation. Examination by flow cytometry of the hematopoietic compartment of Id1(-/-) mice showed an increase in myeloid differentiation. Additionally, we found increased expression of osteoclast genes, TRAP, Oscar, and CTSK in the Id1(-/-) bone marrow microenvironment. Lastly, transplantation of wild-type bone marrow into Id1(-/-) mice repressed TRAP, Oscar, and CTSK expression and activity and rescued the hematopoietic and bone phenotype in these mice. Conclusions/Significance: In conclusion, we demonstrate an osteoporotic phenotype in Id1(-/-) mice and a mechanism for Id1 transcriptional control of osteoclast-associated genes. Our results identify Id1 as a principal player responsible for the dynamic cross-talk between bone and bone marrow hematopoietic cells.

The consumption of caffeine from some common beverages has been associated with low bone mass by inducing urinary calcium loss and deceasing bone mineral density. However, the effect of caffeine on osteoclast differentiation is still unclear. Here, we demonstrate that caffeine directly enhances osteoclast differentiation and maturation. TRAP staining showed that the number of larger (>100 mu m) osteoclastic cells as well as of TRAP-positive multinucleated cells was increased by caffeine treatment. Among the MAP kinases, caffeine specifically activated p38 MAP kinase, which in turn, controlled osteoclast differentiation and maturation. This is evidenced by the abolishment of activated p38 MAP kinase by pretreatment with SB203580, a p38-specific inhibitor, resulting in suppressed osteoclast differentiation and maturation that should be increased by caffeine. Caffeine significantly induced the expression of Mitf and pretreatment with SB203580 markedly suppressed the expression of Mitf induced by caffeine. Whereas it failed to regulate the expression of NFATc1 and Oscar, the expressions of Cathepsin K and TRAP were induced by caffeine treatment in primary preosteoclasts. Real-time PCR and luciferase assays showed that the increase of osteoclastic cell-cell fusion by caffeine was through the transcriptional up-regulation of DC-STAMP expression but not of Atp6v0d2. These results strongly suggest that caffeine directly enhances osteoclast differentiation and maturation through p38 MAP kinase activation, thus inducing Mitf expression and transcriptional activation of DC-STAMP, and finally CtsK and TRAP. (C) 2013 Elsevier Inc. All rights reserved.