Investigating collagen II cartilage disorders using hiPSC-derived cartilage organoids

Date

Oct 25, 2024

Time

11:00 AM - 12:00 PM

Speaker

Jinia Lilianty

Affiliation

Murdoch Children’s Research Institute, The University of Melbourne, Australia

Language

en

Main Topic

Biologie

Host

Meritxell Huch

Description

Collagen II (COL2A1) is a crucial structural protein in cartilage extracellular matrix. COL2A1 mutations lead to various cartilage disorders, ranging from mild early-onset arthritis to lethal perinatal malformations. Existing in vitro disease models do not use disease-specific cells and mouse models do not replicate human physiology, making the study of collagen II disorders particularly challenging. Consequently, the molecular pathology of these mutations is not fully understood, and no effective drug therapies are available for patients. To tackle this problem, we have modelled a severe and a lethal cartilage disorder caused by heterozygous COL2A1 p.R989C and p.G1113C mutations, respectively. We introduced the patient mutations into hiPSCs using CRISPR/Cas9 gene editing. Mutant and isogenic control lines were differentiated into human cartilage organoids using our developed protocol, then we used these organoids to uncover molecular mechanisms of these mutations. While both mutations cause similar collagen biosynthetic defects, they are more severe in p.G1113C mutant organoids compared to p.R989C. The mutant organoids exhibited slow collagen II folding, intracellular retention, dilated endoplasmic reticulum (ER), and reduced and abnormal collagen II fibrils in the extracellular matrix, mirroring findings in patients and mouse models. Despite these similarities, the mutations affected chondrocyte maturation differently: p.R989C accelerated hypertrophy, whereas p.G1113C delayed it, potentially explaining the observed bone defects in patients. Using unbiased whole transcriptomics analysis, we found that both mutant collagen II proteins activate the PERK arm of the ER unfolded protein response (UPR), suggesting ER stress, consistent with the dilated ER found in the mutants. This study expands our understanding of COL2A1 molecular mechanisms in clinically relevant human disease models. Our in vitro models, which reproduce disease phenotypes, have significant potential for pre-clinical drug screening. Ultimately, we can therapeutically target the pathogenic pathway identified in this study, potentially leading to new therapeutic strategies for collagen II disorders.

Last modified: Oct 25, 2024, 7:46:02 AM