The formation of a blood vessel network is crucial for organ development and regeneration. Over the past three decades, the central molecular mechanisms governing blood vessel growth have been extensively studied. Recent evidence indicates that vascular endothelial cells—the specialized cells lining the inner surface of blood vessels—exhibit significant heterogeneity to meet the specific needs of different organs. This review focuses on the current understanding of endothelial cell heterogeneity, which includes both intra-organ and inter-organ heterogeneity. Intra-organ heterogeneity encompasses arterio-venous and tip-stalk endothelial cell specialization, while inter-organ heterogeneity refers to organ-specific transcriptomic profiles and functions. Advances in single-cell RNA sequencing (scRNA-seq) have enabled the identification of new endothelial subpopulations and the comparison of gene expression patterns across different subsets of endothelial cells. Integrating scRNA-seq with other high-throughput sequencing technologies promises to deepen our understanding of endothelial cell heterogeneity at the epigenetic level and in a spatially resolved context. To further explore human endothelial cell heterogeneity, vascular organoids offer powerful tools for studying gene function in three-dimensional culture systems and for investigating endothelial-tissue interactions using human cells. Developing organ-specific vascular organoids presents unique opportunities to unravel inter-organ endothelial cell heterogeneity and its implications for human disease. Emerging technologies, such as scRNA-seq and vascular organoids, are poised to transform our understanding of endothelial cell heterogeneity and pave the way for innovative therapeutic strategies to address human vascular diseases. Graphical Abstract

Mechanotransduction is essential for living cells to adapt to their extracellular environment. However, it is unclear how the biophysical adaptation of intracellular organelles responds to mechanical stress or how these adaptive changes affect cellular homeostasis. Here, using the tendon cell as a mechanosensitive cell type within a bioreactor, we show that the tension of the plasma membrane (PM) and the endoplasmic reticulum (ER) adaptively increases in response to repetitive external stimuli. Depletion of stromal interaction molecule 1 (STIM1), the highest expressed PM-ER tether protein, interfered with mechanotransduction from the PM to the ER, and affected the ER tension. We found that an optimized mechanical strain increased ER tension in a homeostatic manner, but excessive strain resulted in ER expansion, as well as activating ER stress. Last, we showed that changes in ER tension were linked with ER-mitochondria interactions and associated with cellular energetics and function. Together, these findings identify a PM-ER mechanotransduction mechanism that dose-dependently regulates cellular metabolism.

Hematopoiesis and the behavior of hematopoietic stem and progenitor cells (HSPCs) are regulated by the bone marrow niche. Here, we introduce the major niche cell types in bone marrow and their response to stress condition. We highlight the hematopoietic response and bone marrow niche adaptation to inflammatory condition and non-hematopoietic diseases, which are not systematically summarized. These emerging data suggest targeting hematopoiesis and bone marrow niche may provide novel therapeutic target to precisely control the progression of the diseases.

Cyclin-dependent kinases (CDK) 14 regulates cell cycle, tumor expansion by influencing the downstream targets of the canonical Wnt signaling pathway. However, the function of CDK14 during organ development and regeneration has not been investigated in genetically-modified animals. Here, we found that genetic ablation of Cdk14 influenced pulmonary vascular endothelial cells and alveolar epithelial cells during mice embryonic development as well as repair of lung after bleomycin or lipopolysaccharide induced injury. Genetic knockout of Cdk14 and the CDK14 covalent inhibitor FMF-04-159-2 resulted in reduction of pulmonary vessel covered area and epithelial cell number, exhibiting increased mortality and more severe lung damage after injury. Mechanistically, Cdk14 ablation inhibited the proliferation of epithelial and vascular endothelial cells, inducing cell cycle arrest at the G₂/M phase. Through RNA-seq analysis of both endothelial and epithelial cells, we found that knockdown of Cdk14 controls the expression of signal transducers and activator of transcription 1 (STAT1) as well as associated genes in interferon signaling. Disruption of Cdk14 interferes with IFN-γ induced lung repair in vivo, suggesting potential crosstalk of CDK14 signaling and IFN-γ pathway. Our work highlights the importance of Cdk14 in lung development and regenerative repair through an uncharacterized CDK14- IFN-γ signaling axis.

Aims: Rotator cuff tear (RCT) is the leading cause of shoulder pain, primarily associated with age-related tendon degeneration. This study aimed to elucidate the potential differential gene expressions in tendons across different age groups, and to investigate their roles in tendon degeneration.Methods: Linear regression and differential expression (DE) analyses were performed on two transcriptome profiling datasets of torn supraspinatus tendons to identify age-related genes. Subsequent functional analyses were conducted on these candidate genes to explore their potential roles in tendon ageing. Additionally, a secondary DE analysis was performed on candidate genes by comparing their expressions between lesioned and normal tendons to explore their correlations with RCTs.Results: We identified 49 genes in torn supraspinatus tendons associated with advancing age. Among them, five age-related genes showed DE in lesioned tendons compared to normal tendons. Functional analyses and previous studies have highlighted their specific enrichments in biological functions, such as muscle development (e.g. myosin heavy chain 3 (MYH3)), transcription regulation (e.g. CCAAT enhancer binding brotein delta (CEBPD)), and metal ion homeostasis (e.g. metallothionein 1X (MT1X)).Conclusion: This study uncovered molecular aspects of tendon ageing and their potential links to RCT development, offering insights for targeted interventions. These findings enhance our understanding of the mechanisms of tendon degeneration, allowing potential strategies to be made for reducing the incidence of RCT.Cite this article: Bone Joint Res 2024;13(9):474–484.