Project description:Objective: Mammalian somatic cells can be reprogrammed into induced pluripotent stem cells (iPSCs) via the forced expression of Yamanaka reprogramming factors. However, only a limited population of the cells that pass through a particular pathway can metamorphose into iPSCs, while the others do not. This study aimed to clarify the pathways that chondrocytes follow during the reprogramming process. Design: The fate of human articular chondrocytes under reprogramming was investigated through a time-coursed single-cell transcriptomic analysis, which we termed an inverse genetic approach. The iPS interference technique was also employed to verify that chondrocytes inversely return to pluripotency following the proper differentiation pathway . Results: We confirmed that human chondrocytes could be converted into cells with an iPSC phenotype. Moreover, it was clarified that a limited population that underwent the silencing of SOX9, a master gene for chondrogenesis, at a specific point during the proper transcriptome transition pathway, could eventually become iPS cells. Interestingly, the other cells, which failed to be reprogrammed, followed a distinct pathway toward cells with a surface zone chondrocyte phenotype. The critical involvement of cellular communication network factors (CCNs) in this process was indicated. The idea that chondrocytes, when reprogrammed into iPSCs, follow the differentiation pathway backward was supported by the successful iPS interference using SOX9. Conclusions: This inverse genetic strategy is expected to be utilized to identify the master genes for the differentiation of various somatic cells. The utility of CCNs in articular cartilage regeneration is also supported.
Project description:BBF2H7 (BBF2 human homolog on chromosome 7), an ER-resident basic leucine zipper transcription factor, is activated in response to ER stress and abundantly expresses in chondrocytes. While BBF2H7 is widely expressed in many tissues and organs, the most intense signals were detected in the proliferating zone of the cartilage. We compared gene expressions in primary cultured chondrocytes prepared from rib cartilage between WT and BBF2H7-/- mice at E18.5. Primary cultured chondrocytes were prepared from E18.5 rib cartilage of WT and BBF2H7-/- mice. Chondrocytes were isolated using 0.2% collagenase D (Roche) after adherent connective tissue was removed by 0.2% trypsin (Sigma) and collagenase pretreatment. Isolated chondrocytes were maintained in α-MEM (Gibco) supplemented with 10% FCS and 50 µg/mL ascorbic acid. Adenovirus vectors expressing the mouse p60 BBF2H7 (1-377 aa, BBF-N) were constructed with the AdenoX Expression system (Clontech), according to the manufacturerâs protocol. The cells were infected with adenoviruses 30 h before analysis. We compared gene expressions in primary cultured chondrocytes prepared from rib cartilage between WT and BBF2H7-/- mice at E18.5 using a microarray and various genes associated with protein secretory pathway and ER biogenesis were significantly down-regulated in BBF2H7-/- chondrocytes. We infected primary cultured chondrocytes prepared from BBF2H7-/- mice with adenovirus expressing p60 BBF2H7. Several genes were up-regulated and we picked up them as the direct target of BBF2H7.
Project description:We investigated the molecular mechanisms that regulate the self-renewal and differentiation of chondroprogenitors by comparing the transcriptome profiles between resting chondrocytes and proliferative chondrocytes
Project description:The severity of osteoarthritis (OA) and cartilage degeneration are highly correlated with the development of synovitis, which is mediated by the activity of inflammatory macrophages. A better understanding of intercellular communication between inflammatory macrophages and chondrocytes should aid in the discovery of novel therapeutic targets. Here, we explored the pathological role of inflammatory macrophage-extracellular vesicles (EVs) in cartilage degeneration. Macrophages were stimulated by treatment with bacterial lipopolysaccharides to mimic the state of inflammatory macrophages and the resulting EVs (M-LPS EVs) were harvested for chondrocyte stimulation and intraarticular injection in a mouse model. This stimulation resulted in increased catabolism of chondrocytes and cartilage degeneration. Consistently, RNA-seq analyses of stimulated chondrocytes indicated that upregulated genes are mainly categorized into apoptotic process and TNF-signaling pathway which suggests the induction of apoptotic process. These chondrocytes exhibited a significant elevation in the expression of pyroptosis-related molecules that were correlated with the expression of chondrocyte catabolic factors. The disruption of caspase-11 significantly alleviated pyroptotic and catabolic processes in stimulated chondrocytes and the pathological changes in collagenase-induced OA model. Our results provide a new insight into the pathological mechanisms of OA and suggest that non-canonical pyroptosis signaling in chondrocytes represents an attractive therapeutic target for future treatment.
Project description:The synovial joint forms from a pool of progenitor cells in the interzone region of the future joint. Expression of Gdf5 and Wnt9a has been used to mark the earliest cellular processes in the formation of the interzone and the progenitor cells. However, progression and lineage specification toward the different tissues of the joint is not well understood. Here, by lineage tracing studies we identify a population of Lgr5+ interzone cells that contribute to the formation of cruciate ligaments, synovial membrane and articular chondrocytes of the joint. This is supported by single cell transcriptome analyses. Furthermore, we showed that Col22a1, a marker of early articular chondrocytes, co-expresses with Lgr5+ cells prior to cavitation as an important lineage marker specifying the progression towards articular chondrocytes. Lgr5+ cells contribute to the repair of a joint defect with the re-establishment of Col22a1 containing superficial layer.
Project description:This study examines the best way to teach genetics to family medicine residents. First year family medicine residents at the University of Toronto will be taught basic clinical genetics as well as a specific disease in genetics via 3 different educational methods. All participants will undergo an oral examination and written knowledge test 3 months after this education. Results between groups will be compared, and the best way to teach genetics to residents determined.
Project description:Proteins from chondrocytes incubated in various conditions were extracted and subjected to label-free shotgun proteomics for establishing differences between conditions.