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Cell and matrix response of temporomandibular cartilage to mechanical loading.

ABSTRACT: The generation of transgenic mice expressing green fluorescent proteins (GFPs) has greatly aided our understanding of the development of connective tissues such as bone and cartilage. Perturbation of a biological system such as the temporomandibular joint (TMJ) within its adaptive remodeling capacity is particularly useful in analyzing cellular lineage progression. The objectives of this study were to determine: (i) if GFP reporters expressed in the TMJ indicate the different stages of cell maturation in fibrocartilage and (ii) how mechanical loading affects cellular response in different regions of the cartilage.Four-week-old transgenic mice harboring combinations of fluorescent reporters (Dkk3-eGFP, Col1a1(3.6 kb)-GFPcyan, Col1a1(3.6 kb)-GFPtpz, Col2a1-GFPcyan, and Col10a1-RFPcherry) were used to analyze the expression pattern of transgenes in the mandibular condylar cartilage (MCC). To study the effect of TMJ loading, animals were subjected to forced mouth opening with custom springs exerting 50 g force for 1 h/day for 5 days. Dynamic mineralization and cellular proliferation (EdU-labeling) were assessed in loaded vs control mice.Dkk3 expression was seen in the superficial zone of the MCC, followed by Col1 in the cartilage zone, Col2 in the prehypertrophic zone, and Col10 in the hypertrophic zone at and below the tidemark. TMJ loading increased expression of the GFP reporters and EdU-labeling of cells in the cartilage, resulting in a thickness increase of all layers of the cartilage. In addition, mineral apposition increased resulting in Col10 expression by unmineralized cells above the tidemark.The TMJ responded to static loading by forming thicker cartilage through adaptive remodeling.

SUBMITTER: Utreja A

PROVIDER: S-EPMC4757844 | biostudies-literature | 2016 Feb

REPOSITORIES: biostudies-literature

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Cell and matrix response of temporomandibular cartilage to mechanical loading.

Utreja A A Dyment N A NA Yadav S S Villa M M MM Li Y Y Jiang X X Nanda R R Rowe D W DW

Osteoarthritis and cartilage 20150908 2

<h4>Objectives</h4>The generation of transgenic mice expressing green fluorescent proteins (GFPs) has greatly aided our understanding of the development of connective tissues such as bone and cartilage. Perturbation of a biological system such as the temporomandibular joint (TMJ) within its adaptive remodeling capacity is particularly useful in analyzing cellular lineage progression. The objectives of this study were to determine: (i) if GFP reporters expressed in the TMJ indicate the different ...[more]

PMID: 26362410

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Project description:Osteocytes sense mechanical loads and transduce mechanical signals into a chemical response. They are the most abundant bone cells deeply embedded in mineralized bone matrix, which affects their regulatory activity in the mechanical adaptation of bone. The specific location in the calcified bone matrix hinders studies on osteocytes in the in vivo setting. Recently, we developed a three-dimensional mechanical loading model of human osteocytes in their native matrix, allowing to study osteocyte mechanoresponsive target gene expression in vitro. Here we aimed to identify differentially expressed genes by mapping the response of human primary osteocytes in their native matrix to mechanical loading using RNA sequencing. Human fibular bone was retrieved from 10 donors (age: 32-82 years, 5 female, 5 male). Cortical bone explants (8.0 × 3.0 × 1.5 mm; length × width × height) were either not loaded or mechanically loaded by 2000 or 8000 μɛ for 5 minutes, followed by 0, 6, or 24 hours post-culture without loading. High-quality RNA was isolated, and differential gene expression analysis performed by R2 platform. Real-time PCR was used to confirm differentially expressed genes. Twenty-eight genes were differentially expressed between unloaded and loaded (2000 or 8000 μɛ) bone at 6 hours post-culture, and 19 genes at 24 hours post-culture. Eleven of these genes were related to bone metabolism, ie, EGR1, FAF1, H3F3B, PAN2, RNF213, SAMD4A, and TBC1D24 at 6 hours post-culture, and EGFEM1P, HOXD4, SNORD91B, and SNX9 at 24 hours post-culture. Mechanical loading significantly decreased RNF213 gene expression, which was confirmed by real-time PCR. In conclusion, mechanically loaded osteocytes differentially expressed 47 genes, of which 11 genes were related to bone metabolism. RNF213 might play a role in mechanical adaptation of bone by regulating angiogenesis, which is a prerequisite for successful bone formation. The functional aspects of the differentially expressed genes in bone mechanical adaptation requires future investigation. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Project description:BackgroundQuantification of dynamic biomechanical strain in articular cartilage in vivo; in situ using noninvasive MRI techniques is desirable and may potentially be used to assess joint pathology.PurposeTo demonstrate the use of static mechanical loading and continuous 3D-MRI acquisition of the human knee joint in vivo to measure the strain in the tibiofemoral articular cartilage.Study typeProspective.SubjectsFive healthy human volunteers (four women, one man; age 25.6?±?1.7) underwent MRI at rest, under static mechanical loading condition, and during recovery.Field strength/sequenceA field strength of 3T was used. The sequence used was 3D-continuous golden angle radial sparse parallel (GRASP) MRI and compressed sensing (CS) reconstruction.AssessmentTibiofemoral cartilage deformation maps under loading and during recovery were calculated using an optical flow algorithm. The corresponding Lagrangian strain was calculated in the articular cartilage.Statistical testsRange of displacement and strain in each subject, and the resulting mean and standard deviation, were calculated.ResultsDuring the loading condition, the cartilage displacement in the direction of loading ranged from a minimum of -673.6?±?121.9 ?m to a maximum of 726.5?±?169.5 ?m. Corresponding strain ranged from a minimum of -7.0?±?4.2% to a maximum of 5.4?±?1.6%. During the recovery condition, the cartilage displacement in the same direction reduced to a minimum of -613.0?±?129.5 ?m and a maximum of 555.7?±?311.4 ?m. The corresponding strain range reduced to a minimum of -1.6?±?7.5% to a maximum of 4.2?±?2.6%.Data conclusionThis study shows the feasibility of using static mechanical loading with continuous GRASP-MRI acquisition to measure the strain in the articular cartilage. By measuring strain during the loading and recovery phases, dynamic strain information in the articular cartilage might be able to be investigated.Level of evidence2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2020;51:426-434.

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Cell and matrix response of temporomandibular cartilage to mechanical loading.

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Cell and matrix response of temporomandibular cartilage to mechanical loading.

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