Cardiac differentiation is modulated by anti-apoptotic signals in murine embryonic stem cells

BACKGROUND Embryonic stem cells(ESCs)serve as a crucial ex vivo model,representing epiblast cells derived from the inner cell mass of blastocyst-stage embryos.ESCs exhibit a unique combination of self-renewal potency,unlimited proliferation,and pluripotency.The latter is evident by the ability of the isolated cells to differ-entiate spontaneously into multiple cell lineages,representing the three primary embryonic germ layers.Multiple regulatory networks guide ESCs,directing their self-renewal and lineage-specific differentiation.Apoptosis,or programmed cell death,emerges as a key event involved in sculpting and forming various organs and structures ensuring proper embryonic development.How-ever,the molecular mechanisms underlying the dynamic interplay between diffe-rentiation and apoptosis remain poorly understood.AIM To investigate the regulatory impact of apoptosis on the early differentiation of ESCs into cardiac cells,using mouse ESC(mESC)models-mESC-B-cell lym-phoma 2(BCL-2),mESC-PIM-2,and mESC-metallothionein-1(MET-1)-which overexpress the anti-apoptotic genes Bcl-2,Pim-2,and Met-1,respectively.METHODS mESC-T2(wild-type),mESC-BCL-2,mESC-PIM-2,and mESC-MET-1 have been used to assess the effect of potentiated apoptotic signals on cardiac differentiation.The hanging drop method was adopted to generate embryoid bodies(EBs)and induce terminal differentiation of mESCs.The size of the generated EBs was measured in each condition compared to the wild type.At the functional level,the percentage of cardiac differentiation was measured by calculating the number of beating cardiomyocytes in the manipulated mESCs compared to the control.At the molecular level,quantitative reverse transcription-polymerase chain reaction was used to assess the mRNA expression of three cardiac markers:Troponin T,GATA4,and NKX2.5.Additionally,troponin T protein expression was evaluated through immunofluorescence and western blot assays.RESULTS Our findings showed that the upregulation of Bcl-2,Pim-2,and Met-1 genes led to a reduction in the size of the EBs derived from the manipulated mESCs,in comparison with their wild-type counterpart.Additionally,a decrease in the count of beating cardiomyocytes among differentiated cells was observed.Furthermore,the mRNA expression of three cardiac markers-troponin T,GATA4,and NKX2.5-was diminished in mESCs overexpressing the three anti-apoptotic genes compared to the control cell line.Moreover,the overexpression of the anti-apoptotic genes resulted in a reduction in troponin T protein expression.CONCLUSION Our findings revealed that the upregulation of Bcl-2,Pim-2,and Met-1 genes altered cardiac differentiation,providing insight into the intricate interplay between apoptosis and ESC fate determination.

Transdifferentiation of Fetal Liver-delivered Mesenchymal Stem Cells into Cardiomyocyte-like Cells

Objectives To explore the possibility to induce mesenchymal stem cells from human fetal livers （FMSCs） to differentiate along cardiac lineage and the way to obtain high rate of differentiation. Methods Cells from passage 6-9 were plated at the density of 1.5 × 10^4/cm^2 and were treated with the combination of 5-azacytine（5-aza）, retinoitic acid（RA） and Dimethylsulfoxide （DMSO） in different doses when near confluence. 24 hours later, the treatment was removed by changing into normal medium without inducers. Different culture conditions were tried, including temperature, oxygen content and medium. Results When FMSCs were treated with highdose combination （ 5-aza 50 μM ＋RA 10-1 μM ＋ DMSO 1%） and modified combination（5-aza 50 μM ＋RA 10-3 μM ＋ DMSO 0.8 %） in cardiac differentiation medium （CDM）, at 37℃ and 20% 02, the cardiac differentiation was induced. When near confluence, cells became round and tended to gather together to form ball-like structures. 3 weeks after treatment, the cells were harvested and stained with anti-desmin and cardiac troponin I antibodies, and about 40% of the cells were positively stained. No beating cells observed during observation. Conclusions FMSCs cardiac have lineage the potential to differentiate along , and the stimulus for the cardiac differentiation is different from those for MSCs from different species.

CTCF acetylation at lysine 20 is required for the early cardiac mesoderm differentiation of embryonic stem cells

The CCCTC-binding factor(CTCF)protein and its modified forms regulate gene expression and genome organization.However,information on CTCF acetylation and its biological function is still lacking.Here,we show that CTCF can be acetylated at lysine 20(CTCF-K20)by CREB-binding protein(CBP)and deacetylated by histone deacetylase 6(HDAC6).CTCF-K20 is required for the CTCF interaction with CBP.A CTCF point mutation at lysine 20 had no effect on self-renewal but blocked the mesoderm differentiation of mouse embryonic stem cells(mESCs).The CTCF-K20 mutation reduced CTCF binding to the promoters and enhancers of genes associated with early cardiac mesoderm differentia-tion,resulting in diminished chromatin accessibility and decreased enhancer-promoter interactions,impairing gene expression.In summary,this study reveals the important roles of CTCF-K20 in regulating CTCF genomic functions and mESC differentiation into mesoderm.

PGC-1α promotes mitochondrial respiration and biogenesis during the differentiation of hiPSCs into cardiomyocytes

Although it is widely accepted that human induced pluripotent stem cell-derived cardiomyocytes(hiPSC-CMs)are readily available,robustly reproducible,and physiologically appropriate human cells for clinical applications and research in the cardiovascular field,hiPSC-CMs cultured in vitro retain an immature metabolic phenotype that limits their application,and little is known about the underlying molecular mechanism controlling mitochondrial metabolic maturation during human induced pluripotent stem cells(hiPSCs)differentiation into cardiomyocytes.In this study,we found that peroxisome proliferator-activated receptor g coactivator-1α(PGC-1α)played an important role in inducing mitochondrial biogenesis and establishing oxidative phosphorylation(OXPHOS)during the cardiac differentiation of hiPSCs.Knocking down PGC-1α by siRNA impaired mitochondrial respiration,while upregulating PGC-1α by ZLN005 promoted mitochondrial biosynthesis and function by regulating the expression of downstream genes involved in mitochondrial dynamics and oxidative metabolism in hiPSCCMs.Furthermore,we found that estrogen-related receptor a(ERRa)was required for the induction of PGC-1α stimulatory effects in hiPSC-CMs.These findings provide key insights into the molecular control of mitochondrial metabolism during cardiac differentiation and may be used to generate more metabolically mature cardiomyocytes for application.

Biomaterial property-controlled stem cell fates for cardiac regeneration

Myocardial infarction(MI)affects more than 8 million people in the United States alone.Due to the insufficient regeneration capacity of the native myocardium,one widely studied approach is cardiac tissue engineering,in which cells are delivered with or without biomaterials and/or regulatory factors to fully regenerate the cardiac functions.Specifically,in vitro cardiac tissue engineering focuses on using biomaterials as a reservoir for cells to attach,as well as a carrier of various regulatory factors such as growth factors and peptides,providing high cell retention and a proper microenvironment for cells to migrate,grow and differentiate within the scaffolds before implantation.Many studies have shown that the full establishment of a functional cardiac tissue in vitro requires synergistic actions between the seeded cells,the tissue culture condition,and the biochemical and biophysical environment provided by the biomaterials-based scaffolds.Proper electrical stimulation and mechanical stretch during the in vitro culture can induce the ordered orientation and differentiation of the seeded cells.On the other hand,the various scaffolds biochemical and biophysical properties such as polymer composition,ligand concentration,biodegradability,scaffold topography and mechanical properties can also have a significant effect on the cellular processes.