Effects of histone deacetylase inhibitor valproic acid on skeletal myocyte development

EnhancerNet: a predictive model of cell identity dynamics through enhancer selection

Understanding how cell identity is encoded by the genome and acquired during differentiation is a central challenge in cell biology. I have developed a theoretical framework called EnhancerNet, which models the regulation of cell identity through the lens of transcription factor-enhancer interactions. I demonstrate that autoregulation in these interactions imposes a constraint on the model, resulting in simplified dynamics that can be parameterized from observed cell identities. Despite its simplicity, EnhancerNet recapitulates a broad range of experimental observations on cell identity dynamics, including enhancer selection, cell fate induction, hierarchical differentiation through multipotent progenitor states and direct reprogramming by transcription factor overexpression. The model makes specific quantitative predictions, reproducing known reprogramming recipes and the complex haematopoietic differentiation hierarchy without fitting unobserved parameters. EnhancerNet provides insights into how new cell types could evolve and highlights the functional importance of distal regulatory elements with dynamic chromatin in multicellular evolution.

Stem cell-based strategies for skeletal muscle tissue engineering

Skeletal muscle tissue engineering has been a key area of focus over the years and has been of interest for developing regenerative strategies for injured or degenerative skeletal muscle tissue. Stem cells have gained increased attention as sources for developing skeletal muscle tissue for subsequent studies or potential treatments. Focus has been placed on understanding the molecular pathways that govern skeletal muscle formation in development to advance differentiation of stem cells towards skeletal muscle fates in vitro. Use of growth factors and transcription factors have long been the method for guiding skeletal muscle differentiation in vitro. However, further research in small molecule induced differentiation offers a xeno-free option that could result from use of animal derived factors.

Valproic acid stimulates myogenesis in pluripotent stem cell-derived mesodermal progenitors in a NOTCH-dependent manner

Muscular dystrophies are debilitating neuromuscular disorders for which no cure exists. As this disorder affects both cardiac and skeletal muscle, patients would benefit from a cellular therapy that can simultaneously regenerate both tissues. The current protocol to derive bipotent mesodermal progenitors which can differentiate into cardiac and skeletal muscle relies on the spontaneous formation of embryoid bodies, thereby hampering further clinical translation. Additionally, as skeletal muscle is the largest organ in the human body, a high myogenic potential is necessary for successful regeneration. Here, we have optimized a protocol to generate chemically defined human induced pluripotent stem cell-derived mesodermal progenitors (cdMiPs). We demonstrate that these cells contribute to myotube formation and differentiate into cardiomyocytes, both in vitro and in vivo. Furthermore, the addition of valproic acid, a clinically approved small molecule, increases the potential of the cdMiPs to contribute to myotube formation that can be prevented by NOTCH signaling inhibitors. Moreover, valproic acid pre-treated cdMiPs injected in dystrophic muscles increase physical strength and ameliorate the functional performances of transplanted mice. Taken together, these results constitute a novel approach to generate mesodermal progenitors with enhanced myogenic potential using clinically approved reagents.

The Protective Role of Prenatal Alpha Lipoic Acid Supplementation against Pancreatic Oxidative Damage in Offspring of Valproic Acid-Treated Rats: Histological and Molecular Study

Background: Sodium valproate (VPA) is an antiepileptic drug (AED) licensed for epilepsy and used during pregnancy in various indications. Alpha-lipoic acid (ALA) is a natural compound inducing endogenous antioxidant production. Our study aimed to investigate the effect of prenatal administration of VPA on the pancreas of rat offspring and assess the potential protective role of ALA co-administration during pregnancy. Methods: Twenty-eight pregnant female albino rats were divided into four groups: group I (negative control), group II (positive control, ALA treated), group III (VPA-treated), and group IV (VPA-ALA-treated). The pancreases of the rat offspring were removed at the fourth week postpartum and prepared for histological, immune-histochemical, morphometric, molecular, and oxidative stress marker studies. Results: In group III, there were pyknotic nuclei, vacuolated cytoplasm with ballooning of acinar, α, and β cells of the pancreas. Ultrastructural degeneration of cytoplasmic organelles was detected. Additionally, there was a significant increase in oxidative stress, a decrease in insulin-positive cell percentage, and an increase in glucagon positive cells in comparison to control groups. Moreover, VPA increased the gene expression of an apoptotic marker, caspase-3, with a decrease in anti-apoptotic Bcl2 and nuclear factor erythroid 2-related factor 2 (Nrf2) transcriptional factor. Conversely, ALA improved oxidative stress and apoptosis in group VI, and a consequent improvement of the histological and ultrastructure picture was detected. Conclusion: ALA co-administration with VPA significantly improved the oxidative stress condition, histological and morphometric picture of the pancreas, and restored normal expression of related genes, including Nrf2, caspase-3, and Bcl-2. Administration of α-lipoic acid has a protective effect against VPA-induced pancreatic oxidative damage via its cytoprotective antioxidant effect.

The Histone Deacetylase Inhibitor (MS-275) Promotes Differentiation of Human Dental Pulp Stem Cells into Odontoblast-Like Cells Independent of the MAPK Signaling System

The role of dental pulp stem cells (DPSCs) in dental tissue regeneration is gaining attention because DPSCs can differentiate into odontoblasts and other specialized cell types. Epigenetic modification has been found to play an important role in cell differentiation and regulation, among which histone deacetylase (HDAC) is involved in suppressing genes by removing histone acetyl groups. The use of HDAC inhibitor to control this is increasing and has been widely studied by many researchers. This study aimed to induce differentiation by causing epigenetic changes in odontoblast-related genes and the MAPK signaling pathway in human dental pulp stem cells. Western blot and immunofluorescence staining showed increased expression of DMP-1, ALP, DSPP, and RUNX2 compared to the control. However, activation of the MAPK signaling system was similar to but slightly different from the expression of odontoblast-related proteins. After 3 days, as shown by MTT and LDH assays, proliferation decreased overall, but cytotoxicity decreased at only a specific concentration. We confirmed that there was no change in mRNA expression of caspase 3 or 9 using real-time PCR. In addition, flow cytometry analysis confirmed that differentiation occurred due to the decrease in the expression of the CD73 and CD146. Although overall proliferation was reduced due to the G2/M inhibition of the cell cycle, the expression of BCL-2 protected the cells from cell death. Overall, cell proliferation decreased in response to MS-275, but it did not induce cytotoxicity in 5 nM and 10 nM concentration and induces differentiation into odontoblast-like cells.

(Epi)genetic Modifications in Myogenic Stem Cells: From Novel Insights to Therapeutic Perspectives

The skeletal muscle is considered to be an ideal target for stem cell therapy as it has an inherent regenerative capacity. Upon injury, the satellite cells, muscle stem cells that reside under the basal lamina of the myofibres, start to differentiate in order to reconstitute the myofibres while maintaining the initial stem cell pool. In recent years, it has become more and more evident that epigenetic mechanisms such as histon modifications, DNA methylations and microRNA modulations play a pivatol role in this differentiation process. By understanding the mechanisms behind myogenesis, researchers are able to use this knowledge to enhance the differentiation and engraftment potential of different muscle stem cells. Besides manipulation on an epigenetic level, recent advances in the field of genome-engineering allow site-specific modifications in the genome of these stem cells. Combining epigenetic control of the stem cell fate with the ability to site-specifically correct mutations or add genes for further cell control, can increase the use of stem cells as treatment of muscular dystrophies drastically. In this review, we will discuss the advances that have been made in genome-engineering and the epigenetic regulation of muscle stem cells and how this knowledge can help to get stem cell therapy to its full potential.

The effect of sodium valproate on differentiation of human adipose-derived stem cells into cardiomyocyte-like cells in two-dimensional culture and fibrin scaffold conditions

Differentiation of mesenchymal stem cells (MSCs) into cardiomyocytes is a complex phenomenon, and attempts to find an effective inducing agent are still ongoing. We studied the effect of fibrin scaffold and sodium valproate (VPA, as a histone deacetylase inhibitor) on the differentiation of human adipose-derived stem cells (hADSCs) into cardiomyocyte-like cells. The cells were cultured in culture flask (2D) and in fibrin scaffold (3D), fabricated of human plasma fibrinogen, with and without VPA (1 mM). QRT-PCR, Western blot, and immunochemistry assays were used to evaluate the expression of cardiac markers at gene and protein levels. High levels of CD44, CD90, CD73, and CD105 were expressed on the surface of hADSCs. Treated encapsulated hADSCs (3D) presented significantly higher mRNA expression of HAND1 (1.54-fold), HAND2 (1.59-fold), cTnI (1.76-fold), MLC2v (1.4-fold), Cx43 (1.38-fold), βMHC (1.34-fold), GATA4 (1.48-fold), and NKX2.5 (1.66-fold) in comparison to 2D conditions at four weeks after induction. The protein expressions of NKX2.5 (0.78 vs 0.65), cTnI (1.04 vs 0.81), and Cx43 (1.11 vs 1.08) were observed in the differentiated cells both in 3D and 2D groups, while control cells were absolutely negative for these proteins. The frequency of cTnI and Cx43-positive cells was significantly higher in 3D (24.2 ± 15 and 12 ± 3%) than 2D conditions (19.8 ± 3 and 10 ± 2%). Overall, the results showed that VPA can increase cardiomyogenesis in hADSCs and that fibrin scaffold enhances the inductive effect of VPA. Results of this study may improve cell-based protocols for implementation of more successful cardiac repair strategies.

Valproic Acid Exposure of Pregnant Rats During Organogenesis Disturbs Pancreas Development in Insulin Synthesis and Secretion of the Offspring

Valproic acid (VPA) plays a role in histone modifications that eventually inhibit the activity of histone deacetylase (HDAC), and will affect the expressions of genes Pdx1, Nkx6.1, and Ngn3 during pancreatic organogenesis. This experiment was designed to study the effect of VPA exposure in pregnant rats on the activity of HDAC that controls the expression of genes regulating the development of beta cells in the pancreas to synthesize and secrete insulin. This study used 30 pregnant Sprague-Dawley rats, divided into 4 groups, as follows: (1) a control group of pregnant rats without VPA administration, (2) pregnant rats administered with 250 mg VPA on day 10 of pregnancy, (3) pregnant rats administered with 250 mg VPA on day 13 of pregnancy, and (4) pregnant rats administered with 250 mg VPA on day 16 of pregnancy. Eighty-four newborn rats born to control rats and rats administered with VPA on days 10, 13, and 16 of pregnancy were used to measure serum glucose, insulin, DNA, RNA, and ratio of RNA/DNA concentrations in the pancreas and to observe the microscopical condition of the pancreas at the ages of 4 to 32 weeks postpartum with 4-week intervals. The results showed that at the age of 32 weeks, the offspring of pregnant rats administered with 250 mg VPA on days 10, 13, and 16 of pregnancy had higher serum glucose concentrations and lower serum insulin concentrations, followed by decreased concentrations of RNA, and the ratio of RNA/DNA in the pancreas. Microscopical observations showed that the pancreas of the rats born to pregnant rats administered with VPA during pregnancy had low immunoreaction to insulin. The exposure of pregnant rats to VPA during pregnancy disturbs organogenesis of the pancreas of the embryos that eventually disturb the insulin production in the beta cells indicated by the decreased insulin secretion during postnatal life.

Fibrin scaffold could promote survival of the human adipose-derived stem cells during differentiation into cardiomyocyte-like cells

Human adipose-derived stem cells (hADSCs) are capable of differentiation into many cells including cardiac cells. Different types of scaffolds are used for cell differentiation but the best is yet to be determined. In this study, fibrin scaffold (3D) was fabricated using human plasma fibrinogen and compared with culture plates (2D) for the growth and differentiation of hADSCs into cardiomyocyte-like cells. For this purpose, after obtaining the properties of the isolated hADSCs and fibrin scaffold, four biochemical tests were employed to determine the relative growth rate of hADSCs in 2D and 3D cultures. To examine the effects of two different culture systems on cardiomyogenic differentiation, hADSCs were treated with 10 or 50 μM 5-azacytidine (5-Aza) for 24 h and followed until 10 weeks. The results indicated that the growth of hADSCs in 3D significantly increased after the seventh day (P < 0.05). Western blot, qRT-PCR and immunochemistry assays were used to evaluate the rate of cardiac differentiation, which showed significantly higher expression of special cardiac genes such as NKX2.5, Cx43, MLC2v, βMHC, HAND1, HAND2 and cTnI (P < 0.05) in the treated hADSCs with 50 μM 5-Aza in the 3D group. However, the expression level of the specific cardiac proteins in 3D was not significant using western blot and immunofluorescence staining. In conclusion, this study suggests that the fibrin scaffold with a compressive stress of 107.74 kPa can keep the cells alive for 10 weeks and also allows a higher and sooner differentiation of hADSCs into cardiomyocyte-like cells treated with 50 μM 5-Aza.

Histone acetylation favours the cardiovascular commitment of adipose tissue-derived stromal cells

BACKGROUND

Although adipose stromal cells (ASCs) retain the ability to transdifferentiate at low rate towards the cardiac lineage, the potential mechanisms underlying such process have still to be elucidated.

METHODS

Since chromatin state modifications are involved in several processes regulating the cellular cell fate commitment, we aimed at evaluating the role of histone protein acetylation in the cardiovascular-like transdifferentiation of ASCs.

RESULTS

We found a clear increase of histone 3 acetylation status paralleled by a significant upregulation of cardiac TnI gene expression, in ASCs treated with the conditioned medium of primary cardiomyocyte cell cultures for 72h. This result suggests that histone acetylation contributes to the transdifferentiation of ASCs towards the cardiac lineage. In order to directly test this hypothesis, ASCs cultured with regular medium were treated with SAHA, a pan histone deacetylase inhibitor. We found that SAHA enhanced the cardiac permissive state of ASCs, increasing both mRNA and protein expression of cardiovascular genes, particularly cTnI. This suggests that histone acetylation induction is sufficient to promote cardiovascular transdifferentiation.

CONCLUSIONS

The control of ASC fate by epigenetic regulators might be an interesting tool to boost both cardiac commitment and regenerative capacities of ASCs.

Gene expression profiling discerns molecular pathways elicited by ligand signaling to enhance the specification of embryonic stem cells into skeletal muscle lineage

Regulation of lineage specification and differentiation in embryonic stem (ES) cells can be achieved through the activation of endogenous signaling, an avenue for potential application in regenerative medicine. During vertebrate development, retinoic acid (RA) plays an important role in body axis elongation and mesoderm segmentation in that graded exposure to RA provides cells with positional identity and directs commitment to specific tissue lineages. Nevertheless, bexarotene, a clinically approved rexinoid, enhances the specification and differentiation of ES cells into skeletal myocytes more effectively than RA. Thus profiling the transcriptomes of ES cells differentiated with bexarotene or RA permits the identification of different genetic targets and signaling pathways that may contribute to the difference of bexarotene and RA in efficiency of myogenesis. Interestingly, bexarotene induces the early expression of a myogenic progenitor marker, Meox1, while the expression of many RA targets is also enhanced by bexarotene. Several signaling molecules involved in the progression of myogenic specification and commitment are differentially regulated by bexarotene and RA, suggesting that early targets of rexinoid allow the coordinated regulation of molecular events which leads to efficient myogenic differentiation in ES cells.

Harpin Hpa1 promotes flower development in Impatiens and Parochetus plants

BACKGROUND

The harpin protein Hpa1 has multiple beneficial effects in plants, promoting plant growth and development, increasing crop yield, and inducing plant resistance to pathogens and insect pests. In these effects, the 10-40 residue fragment (Hpa110-42) isolated from the Hpa1 sequence is 1.3 to 7.5-fold more effective than the full length.

RESULTS

This study extends the beneficial effects of Hpa1 and Hpa110-42 to flower development in three species of the garden balsam Impatiens and the garden scoparius Parochetus communis plant. The external application of Hpa1 or Hpa110-42 to the four ornamental plants had three effects, i.e., promoting flower growth, retarding senescence of fully expanded flowers, and increasing anthocyanin concentrations in those flowers and therefore improving their ornamental visages. Based on quantitative comparisons, Hpa110-42 was at least 17 and 42 % more effective than Hpa1 to increase anthocyanin concentrations and to promote the growth of flowers or delay their senescence.

CONCLUSION

Our results suggest that Hpa1 and especially Hpa110-42 have a great potential of horticultural application to increase ornamental merits of the different garden plants.

Persistent behavioral effects following early life exposure to retinoic acid or valproic acid in zebrafish

BACKGROUND

Moderate to severe dysregulation in retinoid signaling during early development is associated with a constellation of physical malformations and/or neural tube defects, including spina bifida. It is thought that more subtle dysregulation of this system, which might be achievable via dietary (i.e. hypervitaminosis A) or pharmacological (i.e. valproic acid) exposure in humans, will manifest on behavioral domains including sociability, without overt physical abnormalities.

METHODS

During early life, zebrafish were exposed to low doses of two chemicals that disrupt retinoid signaling. From 0 to 5dpf, larvae were reared in aqueous solutions containing retinoic acid (0, 0.02, 0.2 or 2nM) or valproic acid (0, 0.5, 5.0 or 50μM). One cohort of zebrafish was assessed using a locomotor activity screen at 6-dpf; another was reared to adulthood and assessed using a neurobehavioral test battery (startle habituation, novel tank exploration, shoaling, and predator escape/avoidance).

RESULTS

There was no significant increase in the incidence of physical malformation among exposed fish compared to controls. Both retinoic acid and valproic acid exposures during development disrupted larval activity with persisting behavioral alterations later in life, primarily manifesting as decreased social affiliation.

CONCLUSIONS

Social behavior and some aspects of motor function were altered in exposed fish; the importance of examining emotional or psychological consequences of early life exposure to retinoid acting chemicals is discussed.