Bone resorption and bone formation appear to be tightly coupled. To explore osteoclast influences on osteoblast recruitment and differentiation, we examined osteoclast conditioned media (CM) for influences on osteoblasts. Osteoclast CM stimulated human mesenchymal stem (hMS) cell mineralized nodule formation. We identified candidate osteoclast-derived coupling factors using Affymetrix microarray. We observed induction of sphingosine kinase 1 (SPHK1), WntlOb, and BMP6 in mature multinucleated osteoclasts as compared to pre-osteoclasts. Stimulation of hMS cell nodule formation by the osteoclast CM was attenuated by the Wnt antagonist, Dkk1, a BMP-6 neutralizing antibody, and by a S1P antagonist. Sclerostin expression was elevated in osteoclast precursors and rapidly down-regulated during differentiation. CM from osteoclasts generated in vitro from 18-month old mice was unable to support hMS cell mineralization. TGF-beta treatment elevated SPHK1 and WntlOb expression. Our central hypothesis is that osteoclast production of SPHK1, WntlOb, and BMP6, combined with decreased Sclerostin expression, promotes osteoblast precursor recruitment, proliferation, differentiation, and survival and that each factor plays an integral role in maintaining coupling between osteoclast-mediated bone resorption and osteoblast-mediated bone formation.
In Aim 1, we will use functional cell assays and gene expression to ascertain the mechanisms by which osteoclast-derived coupling factors promote osteoblast gene expression, recruitment, proliferation, differentiation, and survival in vitro.
In Aim 2 we will use molecular approaches to determine the mechanisms by which Sclerostin, SPHK1, WntlOb, and BMP6 are modulated during osteoclast differentiation in vitro.
In Aim 3 we will use an in vivo model to examine the role of TGF-beta regulation of coupling factor production on osteoclast-mediated coupling of bone resorption to bone formation.
In Aim 4 we will examine gene expression and cellular assays to resolve the contribution of age in osteoclast support of osteoblast maturation and mineralization. Together, these studies will provide important novel information on how osteoclasts control osteoblast-mediated bone formation.
A crucial question in bone biology is how osteoblasts are recruited to a resorption site and how the amount of bone laid down is controlled. Studies have implicated osteoclasts as important modulators of bone formation. Understanding the mechanisms by which osteoclasts influence osteoblast recruitment, differentiation, and survival will likely lead to more effective theapies to selectively promote bone formation.
|Farr, Joshua N; Xu, Ming; Weivoda, Megan M et al. (2017) Targeting cellular senescence prevents age-related bone loss in mice. Nat Med 23:1072-1079|
|Rocca, Walter A (2017) Time, Sex, Gender, History, and Dementia. Alzheimer Dis Assoc Disord 31:76-79|
|Khosla, Sundeep; Shane, Elizabeth (2017) Response to Stoecker et al. J Bone Miner Res 32:1388|
|Rocca, Walter A; Savica, Rodolfo; Grossardt, Brandon R (2017) Response to Letter by Friedman on ""Incidence and time trends of drug-induced parkinsonism: A 30-year population-based study"". Mov Disord 32:1111-1112|
|Drake, Matthew T; Khosla, Sundeep (2017) Hormonal and systemic regulation of sclerostin. Bone 96:8-17|
|Gazzuola Rocca, Liliana; Smith, Carin Y; Grossardt, Brandon R et al. (2017) Adverse childhood or adult experiences and risk of bilateral oophorectomy: a population-based case-control study. BMJ Open 7:e016045|
|Farr, Joshua N; Melton 3rd, L Joseph; Achenbach, Sara J et al. (2017) Fracture Incidence and Characteristics in Young Adults Aged 18 to 49 Years: A Population-Based Study. J Bone Miner Res 32:2347-2354|
|Ni Mhuircheartaigh, Orla; Crowson, Cynthia S; Gabriel, Sherine E et al. (2017) Fragility Fractures Are Associated with an Increased Risk for Cardiovascular Events in Women and Men with Rheumatoid Arthritis: A Population-based Study. J Rheumatol 44:558-564|
|Drake, Matthew T; Clarke, Bart L; Oursler, Merry Jo et al. (2017) Cathepsin K Inhibitors for Osteoporosis: Biology, Potential Clinical Utility, and Lessons Learned. Endocr Rev 38:325-350|
|Farr, Joshua N; Fraser, Daniel G; Wang, Haitao et al. (2016) Identification of Senescent Cells in the Bone Microenvironment. J Bone Miner Res 31:1920-1929|
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