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Aberrant Calreticulin Expression in Articular Cartilage of Dio2 Deficient Mice
Nils Bomer1, Frederique M F Cornelis2, Yolande F M Ramos1
1Department of Molecular Epidemiology, LUMC, Leiden, Netherlands.
Objective:
To identify intrinsic differences in cartilage gene expression profiles between wild-type- and Dio2-/--mice, as a mechanism to investigate factors that contribute to prolonged healthy tissue homeostasis.
Methods:
Previously generated microarray-data (Illumina MouseWG-6 v2) of knee cartilage of wild-type and Dio2 -/- -mice were re-analyzed to identify differential expressed genes independent of mechanical loading conditions by forced treadmill-running. RT-qPCR and western blot analyses of overexpression and knockdown of Calr in mouse chondro-progenitor cells (ATDC5) were applied to assess the direct effect of differential Calr expression on cartilage deposition.
Results:
Differential expression analyses of articular cartilage of Dio2-/- (N = 9) and wild-type-mice (N = 11) while applying a cutoff threshold (P < 0.05 (FDR) and FC > |1,5|) resulted in 1 probe located in Calreticulin (Calr) that was found significantly downregulated in Dio2-/- mice (FC = -1.731; P = 0.044). Furthermore, overexpression of Calr during early chondrogenesis in ATDC5 cells leads to decreased proteoglycan deposition and corresponding lower Aggrecan expression, whereas knocking down Calr expression does not lead to histological differences of matrix composition.
Conclusion:
We here demonstrate that the beneficial homeostatic state of articular cartilage in Dio2-/- mice is accompanied with significant lower expression of Calr. Functional analyses further showed that upregulation of Calr expression could act as an initiator of cartilage destruction. The consistent association between Calr and Dio2 expression suggests that enhanced expression of these genes facilitate detrimental effects on cartilage integrity.
Insights
Dio2-/- mice exhibit prolonged healthy cartilage homeostasis due to lower Calreticulin (Calr) expression. Upregulating Calr in cartilage cells can initiate destruction, suggesting Calr and Dio2 expression negatively impact cartilage integrity.
Area of Science:
- Biochemistry
- Molecular Biology
- Genetics
Background:
- Cartilage homeostasis is crucial for joint health.
- Dio2 gene plays a role in thyroid hormone metabolism and potentially cartilage health.
- Understanding gene expression differences can reveal mechanisms of tissue maintenance.
Purpose of the Study:
- To investigate intrinsic gene expression differences in cartilage between wild-type and Dio2 knockout mice.
- To identify factors contributing to prolonged healthy cartilage homeostasis.
- To explore the role of Calreticulin (Calr) in cartilage homeostasis.
Main Methods:
- Re-analysis of existing microarray data from wild-type and Dio2-/- mouse knee cartilage.
- RT-qPCR and Western blot analyses in ATDC5 chondro-progenitor cells.
- Assessing the impact of Calr overexpression and knockdown on cartilage deposition.
Main Results:
- Significantly lower Calreticulin (Calr) expression was observed in Dio2-/- mice cartilage (P < 0.05, FC = -1.731).
- Overexpression of Calr in ATDC5 cells decreased proteoglycan deposition and Aggrecan expression.
- Calr knockdown did not result in significant histological matrix composition differences.
Conclusions:
- Dio2-/- mice display improved cartilage homeostasis associated with reduced Calr expression.
- Increased Calr expression may initiate cartilage destruction.
- A potential detrimental interaction between Calr and Dio2 expression impacts cartilage integrity.
