Mkx mediates tenogenic differentiation but incompletely inhibits the proliferation of hypoxic MSCs

Enthesitis on Chip - A Model for Studying Acute and Chronic Inflammation of the Enthesis and its Pharmacological Treatment

Enthesitis, the inflammation of the enthesis, which is the point of attachment of tendons and ligaments to bones, is a common musculoskeletal disease. The inflammation often originates from the fibrocartilage region of the enthesis as a consequence of mechanical overuse or -load and consequently tissue damage. During enthesitis, waves of inflammatory cytokines propagate in(to) the fibrocartilage, resulting in detrimental, heterotopic bone formation. Understanding of human enthesitis and its treatment options is limited, also because of lacking in vitro model systems that can closely mimic the pathophysiology of the enthesis and can be used to develop therapies. In this study, an enthes(it)is-on-chip model is developed. On opposite sides of a porous culture membrane separating the chip's two microfluidic compartments, human mesenchymal stromal cells are selectively differentiated into tenocytes and fibrochondrocytes. By introducing an inflammatory cytokine cocktail into the fibrochondrocyte compartment, key aspects of acute and chronic enthesitis, measured as increased expression of inflammatory markers, can be recapitulated. Upon inducing chronic inflammatory conditions, hydroxyapatite deposition, enhanced osteogenic marker expression and reduced secretion of tissue-related extracellular matrix components are observed. Adding the anti-inflammatory drug celecoxib to the fibrochondrocyte compartment mitigates the inflammatory state, demonstrating the potential of the enthesitis-on-chip model for drug testing.

Single-cell RNA sequencing analysis of the temporomandibular joint condyle in 3 and 4-month-old human embryos

BACKGROUND

The temporomandibular joint (TMJ) is a complex joint consisting of the condyle, the temporal articular surface, and the articular disc. Functions such as mastication, swallowing and articulation are accomplished by the movements of the TMJ. To date, the TMJ has been studied more extensively, but the types of TMJ cells, their differentiation, and their interrelationship during growth and development are still unclear and the study of the TMJ is limited. The aim of this study was to establish a molecular cellular atlas of the human embryonic temporomandibular joint condyle (TMJC) by single-cell RNA sequencing, which will contribute to understanding and solving clinical problems.

RESULTS

Human embryos at 3 and 4 months of age are an important stage of TMJC development. We performed a comprehensive transcriptome analysis of TMJC tissue from human embryos at 3 and 4 months of age using single-cell RNA sequencing. A total of 16,624 cells were captured and the gene expression profiles of 15 cell clusters in human embryonic TMJC were determined, including 14 known cell types and one previously unknown cell type, "transition state cells (TSCs)". Immunofluorescence assays confirmed that TSCs are not the same cell cluster as mesenchymal stem cells (MSCs). Pseudotime trajectory and RNA velocity analysis revealed that MSCs transformed into TSCs, which further differentiated into osteoblasts, hypertrophic chondrocytes and tenocytes. In addition, chondrocytes (CYTL1^high + THBS1^high) from secondary cartilage were detected only in 4-month-old human embryonic TMJC.

CONCLUSIONS

Our study provides an atlas of differentiation stages of human embryonic TMJC tissue cells, which will contribute to an in-depth understanding of the pathophysiology of the TMJC tissue repair process and ultimately help to solve clinical problems.

MKX-AS1 Gene Expression Associated with Variation in Drug Response to Oxaliplatin and Clinical Outcomes in Colorectal Cancer Patients

Oxaliplatin (OXAL) is a commonly used chemotherapy for treating colorectal cancer (CRC). A recent genome wide association study (GWAS) showed that a genetic variant (rs11006706) in the lncRNA gene MKX-AS1 and partnered sense gene MKX could impact the response of genetically varied cell lines to OXAL treatment. This study found that the expression levels of MKX-AS1 and MKX in lymphocytes (LCLs) and CRC cell lines differed between the rs11006706 genotypes, indicating that this gene pair could play a role in OXAL response. Further analysis of patient survival data from the Cancer Genome Atlas (TCGA) and other sources showed that patients with high MKX-AS1 expression status had significantly worse overall survival (HR = 3.2; 95%CI = (1.17-9); p = 0.024) compared to cases with low MKX-AS1 expression status. Alternatively, high MKX expression status had significantly better overall survival (HR = 0.22; 95%CI = (0.07-0.7); p = 0.01) compared to cases with low MKX expression status. These results suggest an association between MKX-AS1 and MKX expression status that could be useful as a prognostic marker of response to OXAL and potential patient outcomes in CRC.

The role of hypoxia in stem cell regulation of the central nervous system: From embryonic development to adult proliferation

Hypoxia is involved in the regulation of various cell functions in the body, including the regulation of stem cells. The hypoxic microenvironment is indispensable from embryonic development to the regeneration and repair of adult cells. In addition to embryonic stem cells, which need to maintain their self-renewal properties and pluripotency in a hypoxic environment, adult stem cells, including neural stem cells (NSCs), also exist in a hypoxic microenvironment. The subventricular zone (SVZ) and hippocampal dentate gyrus (DG) are the main sites of adult neurogenesis in the brain. Hypoxia can promote the proliferation, migration, and maturation of NSCs in these regions. Also, because most neurons in the brain are non-regenerative, stem cell transplantation is considered as a promising strategy for treating central nervous system (CNS) diseases. Hypoxic treatment also increases the effectiveness of stem cell therapy. In this review, we firstly describe the role of hypoxia in different stem cells, such as embryonic stem cells, NSCs, and induced pluripotent stem cells, and discuss the role of hypoxia-treated stem cells in CNS diseases treatment. Furthermore, we highlight the role and mechanisms of hypoxia in regulating adult neurogenesis in the SVZ and DG and adult proliferation of other cells in the CNS.