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Background: Numerous studies have shown that somite development is a necessary stage of myogenesis chondrogenesis and osteogenesis. Our previous study has established a stable presomitic mesoderm progenitor cell line (UiPSM) in vitro. Naturally, we wanted to explore whether UiPSM cell can develop bone and myogenic differentiation. Results: Selective culture conditions yielded PAX3 and PAX7 positive skeletal muscle precursors from UiPSM cells. The skeletal muscle precursors undergo in vitro maturation resulting in myotube formation. MYOD effectively promoted the maturity of the skeletal myocytes in a short time. We found that UiPSM and MYOD mediated UiPSM cell-derived skeletal myocytes were viable after transplantation into the tibialis anterior muscle of MITRG mice, as assessed by bioluminescence imaging and scRNA-seq. Lack of teratoma formation and evidence of long-term myocytes engraftment suggests considerable potential for future therapeutic applications. Moreover, UiPSM cells can differentiate into osteoblast and chondroblast cells in vitro. Conclusions: UiPSM differentiation has potential as a developmental model for musculoskeletal development research and treatment of musculoskeletal disorders. [ABSTRACT FROM AUTHOR]

Background: The kidneys require vast amounts of mitochondria to provide ample energy to reabsorb nutrients and regulate electrolyte, fluid, and blood pressure homeostasis. The lack of the human model hinders the investigation of mitochondria homeostasis related to kidney physiology and disease. Results: Here, we report the generation of mitochondria-rich kidney organoids via partial reprogramming of human urine cells (hUCs) under the defined medium. First, we reprogrammed mitochondria-rich hUCs into expandable intermediate mesoderm progenitor like cells (U-iIMPLCs), which in turn generated nephron progenitors and formed kidney organoids in both 2D and 3D cultures. Cell fate transitions were confirmed at each stage by marker expressions at the RNA and protein levels, along with chromatin accessibility dynamics. Single cell RNA-seq revealed hUCs-induced kidney organoids (U-iKOs) consist of podocytes, tubules, and mesenchyme cells with 2D dominated with mesenchyme and 3D with tubule and enriched specific mitochondria function associated genes. Specific cell types, such as podocytes and proximal tubules, loop of Henle, and distal tubules, were readily identified. Consistent with these cell types, 3D organoids exhibited the functional and structural features of the kidney, as indicated by dextran uptake and transmission electron microscopy. These organoids can be further matured in the chick chorioallantoic membrane. Finally, cisplatin, gentamicin, and forskolin treatment led to anatomical abnormalities typical of kidney injury and altered mitochondria homeostasis respectively. Conclusions: Our study demonstrates that U-iKOs recapitulate the structural and functional characteristics of the kidneys, providing a promising model to study mitochondria-related kidney physiology and disease in a personalized manner. [ABSTRACT FROM AUTHOR]

Despite direct reprogramming of human cardiac fibroblasts into induced cardiomyocytes (iCM) holds great potential for heart regeneration, the mechanisms are poorly understood. Whether other human somatic cells could be reprogrammed into cardiomyocytes is also unknown. Here, we report human urine cells (hUCs) could be converted into CM-like cells from different donors and the related chromatin accessibility dynamics (CAD) by assay for transposase accessible chromatin(ATAC)-seq. hUCs transduced by MEF2C, TBX5, MESP1 and MYOCD but without GATA4 expressed multiple cardiac specific genes, exhibited Ca2+ oscillation potential and sarcomeric structures, and contracted synchronously in coculture with mouse CM. Additionally, we found that MYOCD is required for both closing and opening critical loci, mainly by hindering the opening of loci enriched with motifs for the TEAD and AP1 family and promoting the closing of loci enriched with ETS motifs. These changes differ partially from CAD observed during iCM induction from human fibroblasts. Collectively, our study offers one practical platform for iCM generation and insights into mechanisms for iCM fate determination. [ABSTRACT FROM AUTHOR]

Reprogramming of human dermal fibroblasts (HDFs) into induced cardiomyocyte-like cells (iCMs) represents a promising strategy for human cardiac regeneration. Different cocktails of cardiac transcription factors can convert HDFs into iCMs, although with low efficiency and immature phenotype. Here, GATA4, MEF2C, TBX5, MESP1, and MYOCD (GMTMeMy for short) were used to reprogram HDFs by retrovirus infection. We found that the exogenous expression stoichiometry of GATA4 (GATA4 stoichiometry) significantly affected reprogramming efficiency. When 1/8 dosage of GATA4 virus (GATA4 dosage) plus MTMeMy was used, the reprogramming efficiency was obviously improved compared with average pooled virus encoding each factor, which measured, by the expression level of cardiac genes, the percentage of cardiac troponin T and alpha-cardiac myosin heavy-chain immunopositive cells and the numbers of iCMs showing calcium oscillation or beating synchronously in co-culture with mouse CMs. In addition, we prepared conditioned maintenance medium (CMM) by CM differentiation of H9 human embryonic stem cell line. We found that compared with traditional maintenance medium (TMM), CMM made iCMs show well-organized sarcomere formation and characteristic calcium oscillation wave earlier. These findings demonstrated that appropriate GATA4 stoichiometry was essential for cardiac reprogramming and some components in CMM were important for maturation of iCMs. [ABSTRACT FROM AUTHOR]

Background: The exit from pluripotency or pluripotent-somatic transition (PST) landmarks an event of early mammalian embryonic development, representing a model for cell fate transition. Results: In this study, using a robust JUN-induced PST within 8 h as a model, we investigate the chromatin accessibility dynamics (CAD) as well as the behaviors of corresponding chromatin remodeling complex SS18/BAFs, to probe the key events at the early stage of PST. Here, we report that, JUN triggers the open of 34661 chromatin sites within 4 h, accomplished with the activation of somatic genes, such as Anxa1, Fosl1. ChIP-seq data reveal a rapid relocation of SS18/BAFs from pluripotent loci to AP-1 associated ones. Consistently, the knockdown of Brg1, core component of BAF complexes, leads to failure in chromatin opening but not closing, resulting in delay for JUN induced PST. Notably, the direct interaction between SS18/BAFs and JUN-centric protein complexes is undetectable by IP-MS. Instead, we show that H3K27ac deposited by cJUN dependent process regulates SS18/BAFs complex to AP1-containing loci and facilitate chromatin opening and gene activation. Conclusions: These results reveal a rapid transfer of chromatin remodeling complexes BAF from pluripotent to somatic loci during PST, revealing a simple mechanistic aspect of cell fate control. [ABSTRACT FROM AUTHOR]