scholarly journals Accelerated Development With Increased Bone Mass and Skeletal Response to Loading Suggest Receptor Activity Modifying Protein-3 as a Bone Anabolic Target

2022 ◽  
Vol 12 ◽  
Author(s):  
Suruchi Pacharne ◽  
Matthew Livesey ◽  
Mahita Kadmiel ◽  
Ning Wang ◽  
Kathleen M. Caron ◽  
...  

Knockout technologies provide insights into physiological roles of genes. Studies initiated into endocrinology of heteromeric G protein-coupled receptors included deletion of receptor activity modifying protein-3, an accessory protein that alters ligand selectivity of calcitonin and calcitonin-like receptors. Initially, deletion of Ramp3-/- appeared phenotypically silent, but it has emerged that mice have a high bone mass phenotype, and more subtle alterations to angiogenesis, amylin homeostasis, and a small proportion of the effects of adrenomedullin on cardiovascular and lymphatic systems. Here we explore in detail, effects of Ramp3-/- deletion on skeletal growth/development, bone mass and response of bone to mechanical loading mimicking exercise. Mouse pups lacking RAMP3 are healthy and viable, having accelerated development of the skeleton as assessed by degree of mineralisation of specific bones, and by microCT measurements. Specifically, we observed that neonates and young mice have increased bone volume and mineralisation in hindlimbs and vertebrae and increased thickness of bone trabeculae. These changes are associated with increased osteoblast numbers and bone apposition rate in Ramp3-/- mice, and increased cell proliferation in epiphyseal growth plates. Effects persist for some weeks after birth, but differences in gross bone mass between RAMP3 and WT mice lose significance in older animals although architectural differences persist. Responses of bones of 17-week old mice to mechanical loading that mimics effects of vigorous exercise is increased significantly in Ramp3-/- mice by 30% compared with WT control mice. Studies on cultured osteoblasts from Ramp3-/- mice indicate interactions between mRNA expression of RAMPs1 and 3, but not RAMP2 and 3. Our preliminary data shows that Ramp3-/- osteoblasts had increased expression β-catenin, a component of the canonical Wnt signalling pathway known to regulate skeletal homeostasis and mechanosensitivity. Given interactions of RAMPs with both calcitonin and calcitonin-like receptors to alter ligand selectivity, and with other GPCRs to change trafficking or ligand bias, it is not clear whether the bone phenotype of Ramp3-/- mice is due to alterations in signalling mediated by one or more GPCRS. However, as antagonists of RAMP-interacting receptors are growing in availability, there appears the likelihood that manipulation of the RAMP3 signalling system could provide anabolic effects therapeutically.

2017 ◽  
Vol 59 (4) ◽  
pp. 351-363 ◽  
Author(s):  
Alexander Kot ◽  
Zhendong A Zhong ◽  
Hongliang Zhang ◽  
Yu-An Evan Lay ◽  
Nancy E Lane ◽  
...  

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.


2007 ◽  
Vol 22 (5) ◽  
pp. 708-716 ◽  
Author(s):  
Wendy Balemans ◽  
Jean-Pierre Devogelaer ◽  
Erna Cleiren ◽  
Elke Piters ◽  
Emanuelle Caussin ◽  
...  

Bone ◽  
2010 ◽  
Vol 47 ◽  
pp. S40
Author(s):  
M. Rauner⁎ ◽  
W. Bauer ◽  
I. Habermann ◽  
M. Haase ◽  
C. Goettsch ◽  
...  

PLoS ONE ◽  
2014 ◽  
Vol 9 (5) ◽  
pp. e98388 ◽  
Author(s):  
Glyn D. Palmer ◽  
Mukundan G. Attur ◽  
Qing Yang ◽  
James Liu ◽  
Paxton Moon ◽  
...  

2018 ◽  
Vol 1 (1) ◽  
Author(s):  
Nick Clough ◽  
Justin Williams ◽  
Uma Sankar

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.


2007 ◽  
Vol 22 (8) ◽  
pp. 1217-1223 ◽  
Author(s):  
Kaoru Washio-Oikawa ◽  
Takahisa Nakamura ◽  
Michihiko Usui ◽  
Mitsuhiro Yoneda ◽  
Youichi Ezura ◽  
...  

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