Dataset Information

The Role of TGFbeta-regulated osteocytic perilacunar/canalicular remodeling in age-related bone fragility

ABSTRACT: Poor bone quality (BQ) is a major factor in skeletal fragility in the elderly. Molecular mechanisms establishing and maintaining BQ, independent of bone mass, are unknown but are thought to be primarily determined by osteocytes. We hypothesize that the age-related decline in BQ results from suppression of osteocyte perilacunar/canalicular remodeling (PLR), which maintains bone material properties. We examined bones from young and aged mice with an osteocyte-intrinsic repression of TGFbeta signaling (TbetaRIIocy-/-) that suppresses PLR. Control-aged bone displayed decreased TGFbeta signaling and PLR, but aging male TbetaRIIocy-/- bone did not worsen existing PLR suppression. This epistatic relationship impacted collagen material behavior at the nano and tissue scale in macromechanical tests. The effects of age on bone mass, density, and mineral material behavior were independent of osteocytic TGFbeta. We determine that the decline of BQ with age arises from lost osteocyte function and maintenance of collagen integrity in a TGFbeta-dependent fashion.

INSTRUMENT(S): Orbitrap Eclipse

ORGANISM(S): Mus Musculus (ncbitaxon:10090)

SUBMITTER: Birgit Schilling

PROVIDER: MSV000091488 | MassIVE | Tue Mar 14 17:33:00 GMT 2023

SECONDARY ACCESSION(S): PXD040873

REPOSITORIES: MassIVE

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Project description:Dysregulation of cell signaling in bone cells, such as osteocytes, osteoblasts, osteoclasts, and chondrocytes, and elevated burden of senescent cells in bone and cartilage, are implicated in osteoarthritis (OA). Mass spectrometric analyses provides a crucial molecular tool-kit to understand complex signaling relationships in age-related diseases, such as OA. Here we introduce a novel mass spectrometric workflow to promote proteomic studies of bone and cartilage. This workflow uses highly specialized steps, including extensive overnight demineralization, pulverization, and incubation for 72 h in 6 M guanidine hydrochloride and EDTA, followed by proteolytic digestion. Analysis on a high-resolution Orbitrap Eclipse and Orbitrap Exploris 480 mass spectrometer using Data-Independent Acquisition (DIA) provides deep coverage of the bone proteome, and preserves post-translational modifications, such as hydroxyproline. A spectral library-free quantification strategy, directDIA, identified and quantified over 2,000 protein groups (with more than 2 unique peptides) from calcium-rich bone matrices. Key components identified were proteins of the extracellular matrix (ECM), bone-specific proteins (e.g., bone sialoprotein 2, IBSP), and signaling proteins (e.g., transforming growth factor beta-2, TGFB2) and lysyl oxidase homolog 2 (LOXL2), an important protein in collagen crosslinking. Post-translational modifications (PTMs) were identified without the need for specific enrichment. This includes collagen hydroxyproline modifications, chemical modifications for collagen self-assembly and network formation. Multiple senescence factors were identified, such as C3 protein of the complement system and many matrix metalloproteinases, that might be monitored during age-related bone disease progression. Our innovative workflow yields in-depth protein coverage and quantification strategies to discover underlying biological mechanisms of bone aging and to provide tools to monitor therapeutic interventions.

Project description:Proctor2016 - Circadian rhythm of PTH and the dynamics of signaling molecules on bone remodeling This model is described in the article: Simulated Interventions to Ameliorate Age-Related Bone Loss Indicate the Importance of Timing. Proctor CJ, Gartland A. Front Endocrinol (Lausanne) 2016; 7: 61 Abstract: Bone remodeling is the continuous process of bone resorption by osteoclasts and bone formation by osteoblasts, in order to maintain homeostasis. The activity of osteoclasts and osteoblasts is regulated by a network of signaling pathways, including Wnt, parathyroid hormone (PTH), RANK ligand/osteoprotegrin, and TGF-?, in response to stimuli, such as mechanical loading. During aging there is a gradual loss of bone mass due to dysregulation of signaling pathways. This may be due to a decline in physical activity with age and/or changes in hormones and other signaling molecules. In particular, hormones, such as PTH, have a circadian rhythm, which may be disrupted in aging. Due to the complexity of the molecular and cellular networks involved in bone remodeling, several mathematical models have been proposed to aid understanding of the processes involved. However, to date, there are no models, which explicitly consider the effects of mechanical loading, the circadian rhythm of PTH, and the dynamics of signaling molecules on bone remodeling. Therefore, we have constructed a network model of the system using a modular approach, which will allow further modifications as required in future research. The model was used to simulate the effects of mechanical loading and also the effects of different interventions, such as continuous or intermittent administration of PTH. Our model predicts that the absence of regular mechanical loading and/or an impaired PTH circadian rhythm leads to a gradual decrease in bone mass over time, which can be restored by simulated interventions and that the effectiveness of some interventions may depend on their timing. This model is hosted on BioModels Database and identified by: BIOMD0000000612. To cite BioModels Database, please use: BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models. To the extent possible under law, all copyright and related or neighbouring rights to this encoded model have been dedicated to the public domain worldwide. Please refer to CC0 Public Domain Dedication for more information.

Dataset Information

The Role of TGFbeta-regulated osteocytic perilacunar/canalicular remodeling in age-related bone fragility

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