Myocardin-related transcription factor-A is a key regulator in retinoic acid-induced neural-like differentiation of adult bone marrow-derived mesenchymal stem cells

Bone marrow mesenchymal stem cells in treatment of peripheral nerve injury

Peripheral nerve injury (PNI) is a common neurological disorder and complete functional recovery is difficult to achieve. In recent years, bone marrow mesenchymal stem cells (BMSCs) have emerged as ideal seed cells for PNI treatment due to their strong differentiation potential and autologous transplantation ability. This review aims to summarize the molecular mechanisms by which BMSCs mediate nerve repair in PNI. The key mechanisms discussed include the differentiation of BMSCs into multiple types of nerve cells to promote repair of nerve injury. BMSCs also create a microenvironment suitable for neuronal survival and regeneration through the secretion of neurotrophic factors, extracellular matrix molecules, and adhesion molecules. Additionally, BMSCs release pro-angiogenic factors to promote the formation of new blood vessels. They modulate cytokine expression and regulate macrophage polarization, leading to immunomodulation. Furthermore, BMSCs synthesize and release proteins related to myelin sheath formation and axonal regeneration, thereby promoting neuronal repair and regeneration. Moreover, this review explores methods of applying BMSCs in PNI treatment, including direct cell transplantation into the injured neural tissue, implantation of BMSCs into nerve conduits providing support, and the application of genetically modified BMSCs, among others. These findings confirm the potential of BMSCs in treating PNI. However, with the development of this field, it is crucial to address issues related to BMSC therapy, including establishing standards for extracting, identifying, and cultivating BMSCs, as well as selecting application methods for BMSCs in PNI such as direct transplantation, tissue engineering, and genetic engineering. Addressing these issues will help translate current preclinical research results into clinical practice, providing new and effective treatment strategies for patients with PNI.

The benign nature and rare occurrence of cardiac myxoma as a possible consequence of the limited cardiac proliferative/ regenerative potential: a systematic review

BACKGROUND

Cardiac Myxoma is a primary tumor of heart. Its origins, rarity of the occurrence of primary cardiac tumors and how it may be related to limited cardiac regenerative potential, are not yet entirely known. This study investigates the key cardiac genes/ transcription factors (TFs) and signaling pathways to understand these important questions.

METHODS

Databases including PubMed, MEDLINE, and Google Scholar were searched for published articles without any date restrictions, involving cardiac myxoma, cardiac genes/TFs/signaling pathways and their roles in cardiogenesis, proliferation, differentiation, key interactions and tumorigenesis, with focus on cardiomyocytes.

RESULTS

The cardiac genetic landscape is governed by a very tight control between proliferation and differentiation-related genes/TFs/pathways. Cardiac myxoma originates possibly as a consequence of dysregulations in the gene expression of differentiation regulators including Tbx5, GATA4, HAND1/2, MYOCD, HOPX, BMPs. Such dysregulations switch the expression of cardiomyocytes into progenitor-like state in cardiac myxoma development by dysregulating Isl1, Baf60 complex, Wnt, FGF, Notch, Mef2c and others. The Nkx2-5 and MSX2 contribute predominantly to both proliferation and differentiation of Cardiac Progenitor Cells (CPCs), may possibly serve roles based on the microenvironment and the direction of cell circuitry in cardiac tumorigenesis. The Nkx2-5 in cardiac myxoma may serve to limit progression of tumorigenesis as it has massive control over the proliferation of CPCs. The cardiac cell type-specific genetic programming plays governing role in controlling the tumorigenesis and regenerative potential.

CONCLUSION

The cardiomyocytes have very limited proliferative and regenerative potential. They survive for long periods of time and tightly maintain the gene expression of differentiation genes such as Tbx5, GATA4 that interact with tumor suppressors (TS) and exert TS like effect. The total effect such gene expression exerts is responsible for the rare occurrence and benign nature of primary cardiac tumors. This prevents the progression of tumorigenesis. But this also limits the regenerative and proliferative potential of cardiomyocytes. Cardiac Myxoma develops as a consequence of dysregulations in these key genes which revert the cells towards progenitor-like state, hallmark of CM. The CM development in carney complex also signifies the role of TS in cardiac cells.

Rapid neurogenic differentiation of human mesenchymal stem cells through electrochemical stimulation

The neurogenic differentiation of human mesenchymal stem cells (hMSCs) has been substantially handicapped with the choice of chemical or electrical stimulations for long durations. We demonstrate an innovative strategy of stimulation with <1.0 V for <200 s to achieve hMSCs differentiation towards neural progenitor cells within 24 h and their commitment towards differentiation to neurons on day 3 with the use of three-electrode electrostimulation. Stimulated hMSCs (ES hMSCs) showed elevated expression of neural-specific markers and mitochondrial membrane potential. A voltage bias of ±0.5 V and ±1.0 V did not show any adverse effect on cell viability and proliferation, whereas cells stimulated with ±1.5 V showed an upsurge in the dead cell populations. With the progression of time after stimulation, a rise in mitochondrial membrane potential (MMP, ΔΨ _M) was observed in the ES hMSCs and thereby generating intracellular reactive oxygen species (ROS), acting as a key messenger to induce neuronal differentiation. The stratagem may provide insightful handles to circumvent neurodifferentiation impediments, a focal issue for regenerative medicine.

Inhibition of epithelial-mesenchymal transition in retinal pigment epithelial cells by a retinoic acid receptor-α agonist

Epithelial-mesenchymal transition (EMT) in retinal pigment epithelial (RPE) cells plays a key role in proliferative retinal diseases such as age-related macular degeneration by contributing to subretinal fibrosis. To investigate the potential role of retinoic acid receptor-α (RAR-α) signaling in this process, we have now examined the effects of the RAR-α agonist Am580 on EMT induced by transforming growth factor-β2 (TGF-β2) in primary mouse RPE cells cultured in a three-dimensional type I collagen gel as well as on subretinal fibrosis in a mouse model. We found that Am580 inhibited TGF-β2-induced collagen gel contraction mediated by RPE cells. It also attenuated the TGF-β2-induced expression of the mesenchymal markers α-smooth muscle actin, fibronectin, and collagen type I; production of pro-matrix metalloproteinase 2 and interleukin-6; expression of the focal adhesion protein paxillin; and phosphorylation of SMAD2 in the cultured RPE cells. Finally, immunofluorescence analysis showed that Am580 suppressed both the TGF-β2-induced translocation of myocardin-related transcription factor-A (MRTF-A) from the cytoplasm to the nucleus of cultured RPE cells as well as subretinal fibrosis triggered by laser-induced photocoagulation in a mouse model. Our observations thus suggest that RAR-α signaling inhibits EMT in RPE cells and might attenuate the development of fibrosis associated with proliferative retinal diseases.

Aortic carboxypeptidase-like protein regulates vascular adventitial progenitor and fibroblast differentiation through myocardin related transcription factor A

The vascular adventitia contains numerous cell types including fibroblasts, adipocytes, inflammatory cells, and progenitors embedded within a complex extracellular matrix (ECM) network. In response to vascular injury, adventitial progenitors and fibroblasts become activated and exhibit increased proliferative capacity and differentiate into contractile cells that remodel the ECM. These processes can lead to vascular fibrosis and disease progression. Our previous work established that the ECM protein aortic carboxypeptidase-like protein (ACLP) promotes fibrotic remodeling in the lung and is activated by vascular injury. It is currently unknown what controls vascular adventitial cell differentiation and if ACLP has a role in this process. Using purified mouse aortic adventitia Sca1+ progenitors, ACLP repressed stem cell markers (CD34, KLF4) and upregulated smooth muscle actin (SMA) and collagen I expression. ACLP enhanced myocardin-related transcription factor A (MRTFA) activity in adventitial cells by promoting MRTFA nuclear translocation. Sca1 cells from MRTFA-null mice exhibited reduced SMA and collagen expression induced by ACLP, indicating Sca1 cell differentiation is regulated in part by the ACLP-MRTFA axis. We determined that ACLP induced vessel contraction and increased adventitial collagen in an explant model. Collectively these studies identified ACLP as a mediator of adventitial cellular differentiation, which may result in pathological vessel remodeling.

RXRα and MRTF-A have a synergistic effect in the retinoic acid-induced neural-like differentiation of adult bone marrow-derived mesenchymal stem cells

Mesenchymal stem cells (MSCs) have multilineage differentiation potential and can transform into neuron cells under an appropriate environment. Retinoic acid (RA) facilitates the neuronal differentiation of MSCs. We found that RXRα, a RA receptor, was significantly upregulated in RA-induced process. Here, we show that RXRα collaborated with myocardin-related transcription factor-A (MRTF-A) to strongly promote the RA-induced process as evidenced by the increase in NF-H expression and NF-H promoter transcription activity. Our studies reveal that RXRα and MRTF-A exhibit protein interactions and synergistically inhibit the MSCs apoptosis by enhancing the P21 expression. Furthermore, RXRα and MRTF-A can activate P21 transcription by affecting the formation of the MRTF-A/RXRα/RARE complex. These findings reveal the important roles of RXRα and MRTF-A signaling in RA-induced neural-like differentiation of MSCs and describe a new mechanism underlying the synergistic interaction of RXRα and MRTF-A.

Differentiation of Human Mesenchymal Stem Cells towards Neuronal Lineage: Clinical Trials in Nervous System Disorders

Mesenchymal stem cells (MSCs) have been proposed as an alternative therapy to be applied into several pathologies of the nervous system. These cells can be obtained from adipose tissue, umbilical cord blood and bone marrow, among other tissues, and have remarkable therapeutic properties. MSCs can be isolated with high yield, which adds to their ability to differentiate into non-mesodermal cell types including neuronal lineage both in vivo and in vitro. They are able to restore damaged neural tissue, thus being suitable for the treatment of neural injuries, and possess immunosuppressive activity, which may be useful for the treatment of neurological disorders of inflammatory etiology. Although the long-term safety of MSC-based therapies remains unclear, a large amount of both pre-clinical and clinical trials have shown functional improvements in animal models of nervous system diseases following transplantation of MSCs. In fact, there are several ongoing clinical trials evaluating the possible benefits this cell-based therapy could provide to patients with neurological damage, as well as their clinical limitations. In this review we focus on the potential of MSCs as a therapeutic tool to treat neurological disorders, summarizing the state of the art of this topic and the most recent clinical studies.

The Synergy of Two Factors on Insulin Expression

As a potential cure for diabetes, more and more attentions have been paid to organ transplants to replace insulin therapy. As a result, many researchers have explored out many programs to get insulin-producing cells (IPCs) to replace the defective β cells. Currently, more and more new induction methods are being proposed, and at the same time, more and more possible induction molecular mechanisms are being revealed. The purpose of this study was to explore whether and how the two factors pdx-1 and myocardin affected the differentiation of rat mesenchymal stem cells (rMSCs) into IPCs. In this study, we investigated the process of transfecting myocardin and/or pdx-1 in rMSCs in vitro. The results showed that rMSCs were able to secrete insulin after cotransfected with myocardin and pdx-1. At the same time, we explored the possible mechanism that myocardin and pdx-1 coinduced rMSCs into IPCs by forming a complex to promote the transcriptional activity of insulin. Our results may provide a theoretical basis to the study of islet transplantation in the future.

Gelatin Directly Enhances Neurogenic Differentiation Potential in Bone Marrow-Derived Mesenchymal Stem Cells Without Stimulation of Neural Progenitor Cell Proliferation

Gelatin has been reported to induce generation of mesenchymal stem cells (MSCs) with enhanced potential of differentiation into neuronal lineage cells. However, the presence of various cell types besides MSCs in bone marrow has raised doubts about the effects of gelatin. In the following report, we determined whether gelatin can directly enhance neurogenic differentiation potential in MSCs without proliferation of neural progenitor cells (NPCs). MSCs comprised a high proportion of bone marrow-derived primary cells (BMPCs) and gelatin induced significant increases in MSC proliferation during primary culture, and the proportion of MSCs was maintained at more than 99% throughout the subculture. However, NPCs comprised a low percentage of BMPCs and a decrease in proliferation was detected despite gelatin treatment during the primary culture, and the proportion of subcultured NPCs gradually decreased. In a similar manner, MSCs exposed to gelatin during primary culture showed more enhanced neurogenic differentiation ability than those not exposed to gelatin. Together, these results demonstrate that gelatin directly enhances neurogenic differentiation in bone marrow-derived MSCs without stimulating NPC proliferation.

Isolation and Culture of Pig Spermatogonial Stem Cells and Their in Vitro Differentiation into Neuron-Like Cells and Adipocytes

Spermatogonial stem cells (SSCs) renew themselves throughout the life of an organism and also differentiate into sperm in the adult. They are multipopent and therefore, can be induced to differentiate into many cells types in vitro. SSCs from pigs, considered an ideal animal model, are used in studies of male infertility, regenerative medicine, and preparation of transgenic animals. Here, we report on a culture system for porcine SSCs and the differentiation of these cells into neuron-like cells and adipocytes. SSCs and Sertoli cells were isolated from neonatal piglet testis by differential adhesion and SSCs were cultured on a feeder layer of Sertoli cells. Third-generation SSCs were induced to differentiate into neuron-like cells by addition of retinoic acid, β-mercaptoethanol, and 3-isobutyl-1-methylxanthine (IBMX) to the induction media and into adipocytes by the addition of hexadecadrol, insulin, and IBMX to the induction media. The differentiated cells were characterized by biochemical staining, qRT-PCR, and immunocytochemistry. The cells were positive for SSC markers, including alkaline phosphatase and SSC-specific genes, consistent with the cells being undifferentiated. The isolated SSCs survived on the Sertoli cells for 15 generations. Karyotyping confirmed that the chromosomal number of the SSCs were normal for pig (2n = 38, n = 19). Pig SSCs were successfully induced into neuron-like cells eight days after induction and into adipocytes 22 days after induction as determined by biochemical and immunocytochemical staining. qPCR results also support this conclusion. The nervous tissue markers genes, Nestin and β-tubulin, were expressed in the neuron-like cells and the adipocyte marker genes, PPARγ and C/EBPα, were expressed in the adipocytes.

Immunodeficiency and severe susceptibility to bacterial infection associated with a loss-of-function homozygous mutation of MKL1

Megakaryoblastic leukemia 1 (MKL1), also known as MAL or myocardin-related transcription factor A (MRTF-A), is a coactivator of serum response factor, which regulates transcription of actin and actin cytoskeleton-related genes. MKL1 is known to be important for megakaryocyte differentiation and function in mice, but its role in immune cells is unexplored. Here we report a patient with a homozygous nonsense mutation in the MKL1 gene resulting in immunodeficiency characterized predominantly by susceptibility to severe bacterial infection. We show that loss of MKL1 protein expression causes a dramatic loss of filamentous actin (F-actin) content in lymphoid and myeloid lineage immune cells and widespread cytoskeletal dysfunction. MKL1-deficient neutrophils displayed reduced phagocytosis and almost complete abrogation of migration in vitro. Similarly, primary dendritic cells were unable to spread normally or to form podosomes. Silencing of MKL1 in myeloid cell lines revealed that F-actin assembly was abrogated through reduction of globular actin (G-actin) levels and disturbed expression of multiple actin-regulating genes. Impaired migration of these cells was associated with failure of uropod retraction likely due to altered contractility and adhesion, evidenced by reduced expression of the myosin light chain 9 (MYL9) component of myosin II complex and overexpression of CD11b integrin. Together, our results show that MKL1 is a nonredundant regulator of cytoskeleton-associated functions in immune cells and fibroblasts and that its depletion underlies a novel human primary immunodeficiency.

Characterization of mesenchymal progenitor cell populations from non-epithelial oral mucosa

OBJECTIVES

The characteristics of cell populations extracted from oral mucosal non-epithelial tissues and their ability to differentiate were evaluated in vitro as a potential source of cells for mandibular and corneal regeneration.

MATERIALS AND METHODS

Oral mucosal non-epithelial cells (OMNECs) were extracted from tissue samples and were studied by flow cytometry and RT-PCR. Cells differentiating into osteoblasts, adipocytes, chondrocytes, neurocytes, or keratocytes were characterized by RT-PCR and cell staining.

RESULTS

OMNECs expressed CD44, CD90, CD105, CD166, and STRO-1 antigens, which are markers for mesenchymal stem cells. In addition, Oct3/4, c-Myc, Nanog, KLF4, and Rex, which are expressed by embryonic or pluripotent stem cells, were detected by RT-PCR. Expression of CD49d, CD56, and PDGFRα, proteins closely associated with the neural crest, was observed in OMNECs, as was expression of Twist1, Sox9, Snail1 and Snail2, which are early neural crest and neural markers. Specific differentiation markers were expressed in OMNECs after differentiation into osteoblasts, adipocytes, chondrocytes, or keratocytes.

CONCLUSIONS

Populations of OMNECs may contain both mesenchymal stem cells and neural crest origin cells and are a potential cell source for autologous regeneration of mandibular or corneal stroma.

Efficient In vitro labeling rabbit bone marrow-derived mesenchymal stem cells with SPIO and differentiating into neural-like cells

Mesenchymal stem cells (MSCs) can differentiate into neural cells to treat nervous system diseases. Magnetic resonance is an ideal means for cell tracking through labeling cells with superparamagnetic iron oxide (SPIO). However, no studies have described the neural differentiation ability of SPIO-labeled MSCs, which is the foundation for cell therapy and cell tracking in vivo. Our results showed that bone marrow-derived mesenchymal stem cells (BM-MSCs) labeled in vitro with SPIO can be induced into neural-like cells without affecting the viability and labeling efficiency. The cellular uptake of SPIO was maintained after labeled BM-MSCs differentiated into neural-like cells, which were the basis for transplanted cells that can be dynamically and non-invasively tracked in vivo by MRI. Moreover, the SPIO-labeled induced neural-like cells showed neural cell morphology and expressed related markers such as NSE, MAP-2. Furthermore, whole-cell patch clamp recording demonstrated that these neural-like cells exhibited electrophysiological properties of neurons. More importantly, there was no significant difference in the cellular viability and [Ca(2+)]i between the induced labeled and unlabeled neural-like cells. In this study, we show for the first time that SPIO-labeled MSCs retained their differentiation capacity and could differentiate into neural-like cells with high cell viability and a good cellular state in vitro.