Role of CaMKK2 in Osteocytes within the Bone Microenvironment

Background and Hypothesis: The Ca+2/calmodulin (CaM)-mediated protein kinase kinase 2 (CaMKK2) is a multi-functional kinase with effects on cell proliferation, differentiation and metabolism. The role of CaMKK2 in bone has been explored with its ablation favoring osteoblasts to osteoclasts and bone mass accrual as observed in Camkk2-/- mice, or following its inhibition by STO-609. One outstanding question is whether the anabolic effects of CaMKK2 are bone-cell intrinsic. While analyzing mice harboring bone-cell specific deletion of CaMKK2, we observed a high bone mass phenotype when the kinase is deleted from osteocytes, the most abundant cells within the bone. We therefore hypothesized that the loss of CaMKK2 enhances osteocyte differentiation. Experimental Design or Project Methods: We used two osteocyte cell lines MLO-Y4 and MLO-A5, both generated from mice expressing the immortalizing T-antigen, to test our hypothesis. The MLO-A5 line has post-osteoblast/pre-osteocyte characteristics while the MLO-Y4 line has mature osteocyte characteristics. CaMKK2 expression was silenced in MLO-A5 cells using Lentiviruses encoding CaMKK2 short hairpin (sh) RNA constructs. STO-609 was employed to inhibit CaMKK2 in the MLO-Y4 line as it proved resistant to transfection. Immunoblotting was used to verify CaMKK2 silencing/inhibition. Comparisons on cell morphologies were observed using immunofluorescence. As osteocytes are defined by dendritic morphology, the number of dendritic processes were analyzed. Additionally, the differences in the expression of the osteocyte markers SOST, E11 and DMP1 were examined by qRT-PCR. Results: To be finalized. Conclusion and Potential Impact: Overall, our studies will provide more information towards understanding the role of CaMKK2 in bone biology and aid its development as a therapeutic target in the treatment of osteoporosis.

Download Full-text

A genomic and transcriptomic approach to the high bone mass phenotype: evidences of heterogeneity and of additive effects of TWIST1, IL6R, DLX3, and PPARG

Bone Abstracts ◽

10.1530/boneabs.1.pp277 ◽

2013 ◽

Author(s):

Patricia Sarrion ◽

Leonardo Mellibovsky ◽

Roser Urreizti ◽

Sergi Civit ◽

Neus Cols ◽

...

Keyword(s):

Bone Mass ◽

Additive Effects ◽

High Bone Mass ◽

High Bone ◽

High Bone Mass Phenotype

Download Full-text

Faculty Opinions recommendation of Cnot7-null mice exhibit high bone mass phenotype and modulation of BMP actions.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1089983.543155 ◽

2007 ◽

Author(s):

Joseph Bidwell

Keyword(s):

Bone Mass ◽

High Bone Mass ◽

High Bone ◽

High Bone Mass Phenotype

Download Full-text

Osteoarthritis: Insights Offered by the Study of Bone Mass Genetics

Current Osteoporosis Reports ◽

10.1007/s11914-021-00655-1 ◽

2021 ◽

Vol 19 (2) ◽

pp. 115-122

Author(s):

A. Hartley ◽

C. L. Gregson ◽

L. Paternoster ◽

J. H. Tobias

Keyword(s):

Bone Mass ◽

Causal Effect ◽

Mendelian Randomisation ◽

Mineral Density ◽

High Bone Mass ◽

Increased Risk ◽

High Bone ◽

Genetic Mechanisms ◽

Additional Support

Abstract Purpose of Review This paper reviews how bone genetics has contributed to our understanding of the pathogenesis of osteoarthritis. As well as identifying specific genetic mechanisms involved in osteoporosis which also contribute to osteoarthritis, we review whether bone mineral density (BMD) plays a causal role in OA development. Recent Findings We examined whether those genetically predisposed to elevated BMD are at increased risk of developing OA, using our high bone mass (HBM) cohort. HBM individuals were found to have a greater prevalence of OA compared with family controls and greater development of radiographic features of OA over 8 years, with predominantly osteophytic OA. Initial Mendelian randomisation analysis provided additional support for a causal effect of increased BMD on increased OA risk. In contrast, more recent investigation estimates this relationship to be bi-directional. However, both these findings could be explained instead by shared biological pathways. Summary Pathways which contribute to BMD appear to play an important role in OA development, likely reflecting shared common mechanisms as opposed to a causal effect of raised BMD on OA. Studies in HBM individuals suggest this reflects an important role of mechanisms involved in bone formation in OA development; however further work is required to establish whether the same applies to more common forms of OA within the general population.

Download Full-text

Sex dimorphic regulation of osteoprogenitor progesterone in bone stromal cells

Journal of Molecular Endocrinology ◽

10.1530/jme-17-0076 ◽

2017 ◽

Vol 59 (4) ◽

pp. 351-363 ◽

Cited By ~ 3

Author(s):

Alexander Kot ◽

Zhendong A Zhong ◽

Hongliang Zhang ◽

Yu-An Evan Lay ◽

Nancy E Lane ◽

...

Keyword(s):

Mouse Model ◽

Bone Mass ◽

Gene Transcription ◽

Conditional Knockout ◽

Sequencing Analysis ◽

Wild Type ◽

High Bone Mass ◽

Matrix Interaction ◽

High Bone ◽

High Bone Mass Phenotype

Increasing peak bone mass is a promising strategy to prevent osteoporosis. A mouse model of global progesterone receptor (PR) ablation showed increased bone mass through a sex-dependent mechanism. Cre-Lox recombination was used to generate a mouse model of osteoprogenitor-specific PR inactivation, which recapitulated the high bone mass phenotype seen in the PR global knockout mouse mode. In this work, we employed RNA sequencing analysis to evaluate sex-independent and sex-dependent differences in gene transcription of osteoprogenitors of wild-type and PR conditional knockout mice. PR deletion caused marked sex hormone-dependent changes in gene transcription in male mice as compared to wild-type controls. These transcriptional differences revealed dysregulation in pathways involving immunomodulation, osteoclasts, bone anabolism, extracellular matrix interaction and matrix interaction. These results identified many potential mechanisms that may explain our observed high bone mass phenotype with sex differences when PR was selectively deleted in the MSCs.

Download Full-text