Dissecting dual roles of MyoD during lineage conversion to mature myocytes and myogenic stem cells

The generation of myotubes from fibroblasts upon forced MyoD expression is a classic example of transcription factor-induced reprogramming. We recently discovered that additional modulation of signaling pathways with small molecules facilitates reprogramming to more primitive induced myogenic progenitor cells (iMPCs). Here, we dissected the transcriptional and epigenetic dynamics of mouse fibroblasts undergoing reprogramming to either myotubes or iMPCs using a MyoD-inducible transgenic model. Induction of MyoD in fibroblasts combined with small molecules generated Pax7+ iMPCs with high similarity to primary muscle stem cells. Analysis of intermediate stages of iMPC induction revealed that extinction of the fibroblast program preceded induction of the stem cell program. Moreover, key stem cell genes gained chromatin accessibility prior to their transcriptional activation, and these regions exhibited a marked loss of DNA methylation dependent on the Tet enzymes. In contrast, myotube generation was associated with few methylation changes, incomplete and unstable reprogramming, and an insensitivity to Tet depletion. Finally, we showed that MyoD's ability to bind to unique bHLH targets was crucial for generating iMPCs but dispensable for generating myotubes. Collectively, our analyses elucidate the role of MyoD in myogenic reprogramming and derive general principles by which transcription factors and signaling pathways cooperate to rewire cell identity.

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Pro-myogenic small molecules revealed by a chemical screen on primary muscle stem cells

Skeletal Muscle ◽

10.1186/s13395-020-00248-z ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Sean M. Buchanan ◽

Feodor D. Price ◽

Alessandra Castiglioni ◽

Amanda Wagner Gee ◽

Joel Schneider ◽

...

Keyword(s):

Skeletal Muscle ◽

Stem Cells ◽

Stem Cell ◽

Small Molecules ◽

Satellite Cell ◽

Satellite Cells ◽

Muscle Repair ◽

Muscle Stem Cells

Abstract Satellite cells are the canonical muscle stem cells that regenerate damaged skeletal muscle. Loss of function of these cells has been linked to reduced muscle repair capacity and compromised muscle health in acute muscle injury and congenital neuromuscular diseases. To identify new pathways that can prevent loss of skeletal muscle function or enhance regenerative potential, we established an imaging-based screen capable of identifying small molecules that promote the expansion of freshly isolated satellite cells. We found several classes of receptor tyrosine kinase (RTK) inhibitors that increased freshly isolated satellite cell numbers in vitro. Further exploration of one of these compounds, the RTK inhibitor CEP-701 (also known as lestaurtinib), revealed potent activity on mouse satellite cells both in vitro and in vivo. This expansion potential was not seen upon exposure of proliferating committed myoblasts or non-myogenic fibroblasts to CEP-701. When delivered subcutaneously to acutely injured animals, CEP-701 increased both the total number of satellite cells and the rate of muscle repair, as revealed by an increased cross-sectional area of regenerating fibers. Moreover, freshly isolated satellite cells expanded ex vivo in the presence of CEP-701 displayed enhanced muscle engraftment potential upon in vivo transplantation. We provide compelling evidence that certain RTKs, and in particular RET, regulate satellite cell expansion during muscle regeneration. This study demonstrates the power of small molecule screens of even rare adult stem cell populations for identifying stem cell-targeting compounds with therapeutic potential.

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

Cells ◽

10.3390/cells8050429 ◽

2019 ◽

Vol 8 (5) ◽

pp. 429 ◽

Cited By ~ 3

Author(s):

Natacha Breuls ◽

Giorgia Giacomazzi ◽

Maurilio Sampaolesi

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Cell Therapy ◽

Cell Fate ◽

Stem Cell Therapy ◽

Genome Engineering ◽

Full Potential ◽

Muscle Stem Cells ◽

Genetic Modifications ◽

Myogenic Stem Cells

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.

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Stem Cell Function, Self-Renewal, Heterogeneity, and Regenerative Potential in Skeletal Muscle Stem Cells

Recent Patents on Regenerative Medicine ◽

10.2174/2210296511202010011 ◽

2012 ◽

Vol 2 (1) ◽

pp. 11-21

Author(s):

Silvia Cristini ◽

Giulio Alessandri ◽

Francesco Acerbi ◽

Daniela Tavian ◽

Eugenio A. Parati ◽

...

Keyword(s):

Skeletal Muscle ◽

Stem Cells ◽

Stem Cell ◽

Cell Function ◽

Self Renewal ◽

Muscle Stem Cells ◽

Skeletal Muscle Stem Cells

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Stem Cell Function, Self-Renewal, Heterogeneity, and Regenerative Potential in Skeletal Muscle Stem Cells

Recent Patents on Regenerative Medicine ◽

10.2174/2210297311202010011 ◽

2012 ◽

Vol 2 (1) ◽

pp. 11-21

Author(s):

Silvia Cristini ◽

Giulio Alessandri ◽

Francesco Acerbi ◽

Daniela Tavian ◽

Eugenio A. Parati ◽

...

Keyword(s):

Skeletal Muscle ◽

Stem Cells ◽

Stem Cell ◽

Cell Function ◽

Self Renewal ◽

Muscle Stem Cells ◽

Skeletal Muscle Stem Cells

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Induction of Stem Cell Like Cells from Mouse Embryonic Fibroblast by Short-Term Shear Stress and Vitamin C

Applied Sciences ◽

10.3390/app11041941 ◽

2021 ◽

Vol 11 (4) ◽

pp. 1941

Author(s):

Seungmin Yeom ◽

Myung Chul Lee ◽

Shambhavi Pandey ◽

Jaewoon Lim ◽

Sangbae Park ◽

...

Keyword(s):

Stem Cells ◽

Shear Stress ◽

Stem Cell ◽

Vitamin C ◽

Suspension Culture ◽

Small Molecules ◽

Tumor Development ◽

Embryonic Stem ◽

Short Term ◽

External Stimuli

Induced pluripotent stem cells (iPSCs) are a good medicine source because of their potential to differentiate into various tissues or cells. However, traditionally, iPSCs made by specific transgenes and virus vectors are not appropriate for clinical use because of safety concerns and risk of tumor development. The goal of this research was to develop an alternative method for reprogramming, using small molecules and external stimuli. Two groups were established: short-term shear stress (STSS) under suspension culture and a combination of short-term shear stress and vitamin C (SSVC) under suspension culture. For STSS, the pipetting was carried out for cells twice per day for 2 min for 14 days in the embryonic stem cell (ES) medium. In the case of SSVC, the procedure was the same as for STSS however, its ES medium included 10 µM of vitamin C. After 14 days, all spheroids were picked and checked for pluripotency by ALP (alkaline phosphatase) assay and immunocytochemistry. Both groups partially showed the characteristics of stem cells but data demonstrated that the spheroids under shear stress and vitamin C had improved stem cell-like properties. This research showed the possibility of external stimuli and small molecules to reprogram the somatic cells without the use of transgenes.

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Empowering Muscle Stem Cells for the Treatment of Duchenne Muscular Dystrophy

Cells Tissues Organs ◽

10.1159/000514305 ◽

2021 ◽

pp. 1-14

Author(s):

Romina L. Filippelli ◽

Natasha C. Chang

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Duchenne Muscular Dystrophy ◽

Muscular Dystrophy ◽

Cell Function ◽

Critical Role ◽

Membrane Integrity ◽

Muscle Membrane ◽

Muscle Stem Cell ◽

Muscle Stem Cells

Duchenne muscular dystrophy (DMD) is a devastating and debilitating muscle degenerative disease affecting 1 in every 3,500 male births worldwide. DMD is progressive and fatal; accumulated weakening of the muscle tissue leads to an inability to walk and eventual loss of life due to respiratory and cardiac failure. Importantly, there remains no effective cure for DMD. DMD is caused by defective expression of the <i>DMD</i> gene, which encodes for dystrophin, a component of the dystrophin glycoprotein complex. In muscle fibers, this protein complex plays a critical role in maintaining muscle membrane integrity. Emerging studies have shown that muscle stem cells, which are adult stem cells responsible for muscle repair, are also affected in DMD. DMD muscle stem cells do not function as healthy muscle stem cells, and their impairment contributes to disease progression. Deficiencies in muscle stem cell function include impaired establishment of cell polarity leading to defective asymmetric stem cell division, reduced myogenic commitment, impaired differentiation, altered metabolism, and enhanced entry into senescence. Altogether, these findings indicate that DMD muscle stem cells are dysfunctional and have impaired regenerative potential. Although recent advances in adeno-associated vector and antisense oligonucleotide-mediated mechanisms for gene therapy have shown clinical promise, the current therapeutic strategies for muscular dystrophy do not effectively target muscle stem cells and do not address the deficiencies in muscle stem cell function. Here, we discuss the merits of restoring endogenous muscle stem cell function in degenerating muscle as a viable regenerative medicine strategy to mitigate DMD.

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Small Molecules Affect Human Dental Pulp Stem Cell Properties Via Multiple Signaling Pathways

Stem Cells and Development ◽

10.1089/scd.2012.0426 ◽

2013 ◽

Vol 22 (17) ◽

pp. 2402-2413 ◽

Cited By ~ 21

Author(s):

Mey Al-Habib ◽

Zongdong Yu ◽

George T.-J. Huang

Keyword(s):

Stem Cell ◽

Small Molecules ◽

Signaling Pathways ◽

Dental Pulp ◽

Human Dental Pulp ◽

Dental Pulp Stem Cell ◽

Multiple Signaling

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The Role of the Renin–Angiotensin System in the Cancer Stem Cell Niche

Journal of Histochemistry & Cytochemistry ◽

10.1369/00221554211026295 ◽

2021 ◽

pp. 002215542110262

Author(s):

Ethan J. Kilmister ◽

Swee T. Tan

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Signaling Pathways ◽

Renin Angiotensin System ◽

Epidemiological Data ◽

Malignant Cells ◽

Angiotensin System ◽

Renin Angiotensin

Cancer stem cells (CSCs) drive metastasis, treatment resistance, and tumor recurrence. CSCs reside within a niche, an anatomically distinct site within the tumor microenvironment (TME) that consists of malignant and non-malignant cells, including immune cells. The renin–angiotensin system (RAS), a critical regulator of stem cells and key developmental processes, plays a vital role in the TME. Non-malignant cells within the CSC niche and stem cell signaling pathways such as the Wnt, Hedgehog, and Notch pathways influence CSCs. Components of the RAS and cathepsins B and D that constitute bypass loops of the RAS are expressed on CSCs in many cancer types. There is extensive in vitro and in vivo evidence showing that RAS inhibition reduces tumor growth, cell proliferation, invasion, and metastasis. However, there is inconsistent epidemiological data on the effect of RAS inhibitors on cancer incidence and survival outcomes, attributed to different patient characteristics and methodologies used between studies. Further mechanistic studies are warranted to investigate the precise effects of the RAS on CSCs directly and/or the CSC niche. Targeting the RAS, its bypass loops, and convergent signaling pathways participating in the TME and other key stem cell pathways that regulate CSCs may be a novel approach to cancer treatment:

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APC is required for muscle stem cell proliferation and skeletal muscle tissue repair

The Journal of Cell Biology ◽

10.1083/jcb.201501053 ◽

2015 ◽

Vol 210 (5) ◽

pp. 717-726 ◽

Cited By ~ 27

Author(s):

Alice Parisi ◽

Floriane Lacour ◽

Lorenzo Giordani ◽

Sabine Colnot ◽

Pascal Maire ◽

...

Keyword(s):

Cell Cycle ◽

Skeletal Muscle ◽

Stem Cells ◽

Stem Cell ◽

Cell Cycle Progression ◽

Cell Types ◽

Double Knockout ◽

Muscle Stem Cells ◽

Adult Muscle ◽

Canonical Wnt

The tumor suppressor adenomatous polyposis coli (APC) is a crucial regulator of many stem cell types. In constantly cycling stem cells of fast turnover tissues, APC loss results in the constitutive activation of a Wnt target gene program that massively increases proliferation and leads to malignant transformation. However, APC function in skeletal muscle, a tissue with a low turnover rate, has never been investigated. Here we show that conditional genetic disruption of APC in adult muscle stem cells results in the abrogation of adult muscle regenerative potential. We demonstrate that APC removal in adult muscle stem cells abolishes cell cycle entry and leads to cell death. By using double knockout strategies, we further prove that this phenotype is attributable to overactivation of β-catenin signaling. Our results demonstrate that in muscle stem cells, APC dampens canonical Wnt signaling to allow cell cycle progression and radically diverge from previous observations concerning stem cells in actively self-renewing tissues.

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