Biology subjects

Beier, F.

Publications and source records attributed to Beier, F..

4 recordsLinked to original sources

bioRxiv2019

Overexpression Of Mig-6 In Limb Mesenchyme Leads To Accelerated Osteoarthritis In Mice

BackgroundMitogen-inducible gene 6 (Mig-6) is a tumour suppressor gene that is also associated with the development of osteoarthritis (OA)-like disorder. Recent evidence from our lab and others showed that cartilage-specific Mig-6 knockout (KO) mice develop chondro-osseous nodules, along with increased articular cartilage thickness and enhanced EGFR signaling in the articular cartilage. Here, we evaluate the phenotype of mice with skeletal-specific overexpression of Mig-6. MethodsSynovial joint tissues of the knee were assessed in 12 and 36 weeks-old skeleton-specific Mig-6 overexpressing (Mig-6over/over) and control animals using histological stains, immunohistochemistry, semi-quantitative OARSI scoring, and microCT for skeletal morphometry. Measurement of articular cartilage and subchondral bone thickness were also performed using histomorphometry. ResultsOur results show only subtle developmental effects of Mig-6 overexpression. However, male Mig-6over/over mice show accelerated cartilage degeneration at 36 weeks of age, in both medial and lateral compartments of the knee. Immunohistochemistry for SOX9 and PRG4 showed decreased staining in Mig-6over/over mice relative to controls, providing potential molecular mechanisms for the observed effects. ConclusionOverexpression of Mig-6 in articular cartilage causes no major developmental phenotype but results in accelerated development of OA during aging. These data demonstrate that precise regulation of the Mig-6/EGFR pathway is critical for joint homeostasis.

genetics↗

bioRxiv2019

Exposure to the RXR agonist SR11237 in early life causes disturbed skeletal morphogenesis in a rat model

Longitudinal bone growth occurs through endochondral ossification (EO), controlled by various signaling molecules. Retinoid X Receptor (RXR) is a nuclear receptor with important roles in cell death, development, and metabolism. However, little is known about its role in EO. In this study, the agonist SR11237 was used to evaluate RXR activation on EO.\n\nRats given SR11237 from post-natal day 5 to 15 were harvested for micro-computed tomography scanning and histology. In parallel, newborn CD1 mouse tibiae were cultured with increasing concentrations of SR11237 for histological and whole mount evaluation.\n\nRXR agonist-treated rats were smaller than controls, and developed dysmorphia of the growth plate. Cells invading the calcified and dysmorphic growth plate appeared pre-hypertrophic in size and shape corresponding with P57 immunostaining. Additionally, SOX9 positive cells were found surrounding the calcified tissue. The epiphysis of SR11237 treated bones showed increased TRAP staining, and additional TUNEL staining at the osteo-chondral junction. MicroCT revealed morphological disorganization in the long bones of treated animals. Isolated mouse long bones treated with SR11237 grew significantly less than their DMSO controls.\n\nThis study demonstrates that stimulation of the RXR receptor causes irregular ossification, premature closure of the growth plate, and disrupted long bone growth in rodent models.

developmental biology↗

bioRxiv2019

Overexpression of Mig-6 in Cartilage Induces An Osteoarthritis-Like Phenotype In Mice.

BackgroundOsteoarthritis (OA) is the most common form of arthritis and characterized by degeneration of articular cartilage. Mitogen-inducible gene 6 (Mig-6) has been identified as a negative regulator of the Epidermal Growth Factor Receptor (EGFR). Cartilage-specific Mig-6 knockout (KO) mice display increased EGFR signaling, an anabolic buildup of articular cartilage and formation of chondro-osseous nodules. Since our understanding of the EGFR/Mig-6 network in cartilage remains incomplete, we characterized mice with cartilage-specific overexpression of Mig-6 in this study.\n\nMethodsUtilizing knee joints from cartilage-specific Mig-6 overexpressing (Mig-6over/over) mice (at multiple time points), we evaluated the articular cartilage using histology, immunohistochemical staining and semi-quantitative OARSI scoring at multiple ages. MicroCT analysis was employed to examine skeletal morphometry, body composition, and bone mineral density.\n\nResultsOur data show that cartilage-specific Mig-6 overexpression did not cause any major developmental abnormalities in articular cartilage, although Mig-6over/over mice have slightly shorter long bones compared to the control group. Moreover, there was no significant difference in bone mineral density and body composition in any of the groups. However, our results indicate that Mig-6over/over male mice show accelerated cartilage degeneration at 12 and 18 months of age. Immunohistochemistry for SOX9 demonstrated that the number of positively stained cells in Mig-6over/over mice decreased relative to controls. Immunostaining for MMP13 staining is increased in areas of cartilage degeneration in Mig-6over/over mice. Moreover, staining for phospho-EGFR (Tyr-1173) and lubricin (PRG4) was decreased in the articular cartilage of Mig-6over/over mice.\n\nConclusionOverexpression of Mig-6 in articular cartilage causes no major developmental phenotype; however these mice develop earlier OA during aging. These data demonstrate that Mig-6/EGFR pathways is critical for joint homeostasis and might present a promising therapeutic target for OA.

physiology↗

bioRxiv2019

Liver X Receptor activation regulates genes involved in lipid homeostasis in developing chondrocytes

ObjectiveOsteoarthritis (OA) is the most common type of arthritis and causes debilitating symptoms and decreased quality of life. Currently available treatment options target symptoms but do not address the underlying issue of joint tissue degeneration. As such, a better understanding of the molecular mechanisms maintaining cartilage health is needed for developing novel therapeutic strategies. Liver X Receptors (LXRs) are nuclear receptors that have been previously shown to offer protection against OA. This is potentially due to suppression of chondrocyte hypertrophy in endochondral bone growth in response to LXR activation. In order to better understand the regulatory mechanisms behind this effect, we aimed to systematically examine LXRs effects on growth plate chondrocyte gene expression.\n\nMethodsPrimary chondrocytes isolated from the long bones of E15.5 mice were treated with the specific LXR agonist, GW3965, and RNA was isolated for Affymetrix microarrays followed by real time qPCR validation. Bioinformatics analyses were performed using Gene Ontology (GO) and KEGG pathway analysis. Immunohistochemistry was conducted to examine protein localization of LXR and identified targets in GW3965-treated E15.5 tibiae compared to control.\n\nResultsActivation of LXR in primary growth plate chondrocytes resulted in differential regulations of various genes involved in lipid metabolism, including several genes involved in cholesterol efflux. This pattern was compared to LXR activation in immature murine articular chondrocytes (IMACs), which revealed similar roles in lipid homeostasis. Immunohistochemical analysis of LXR and its identified targets Abca1 and Srebf1 revealed preferential protein localization to pre-hypertrophic and resting chondrocytes in GW3965-treated tibial growth plates compared to controls.\n\nConclusionOur findings show for the first time that LXR activation alters expression of lipid metabolism genes in growth plate chondrocytes, in part through activation of molecules responsible for cellular cholesterol efflux. This provides insight into potential mechanisms through which LXR regulates cellular metabolism to alter chondrocyte behavior and phenotype.

physiology↗