scholarly journals Controlling Self-Renewal and Differentiation of Stem Cells via Mechanical Cues

2012 ◽  
Vol 2012 ◽  
pp. 1-12 ◽  
Author(s):  
Michele M. Nava ◽  
Manuela T. Raimondi ◽  
Riccardo Pietrabissa

The control of stem cell responsein vitro, including self-renewal and lineage commitment, has been proved to be directed by mechanical cues, even in the absence of biochemical stimuli. Through integrin-mediated focal adhesions, cells are able to anchor onto the underlying substrate, sense the surrounding microenvironment, and react to its properties. Substrate-cell and cell-cell interactions activate specific mechanotransduction pathways that regulate stem cell fate. Mechanical factors, including substrate stiffness, surface nanotopography, microgeometry, and extracellular forces can all have significant influence on regulating stem cell activities. In this paper, we review all the most recent literature on the effect of purely mechanical cues on stem cell response, and we introduce the concept of “force isotropy” relevant to cytoskeletal forces and relevant to extracellular loads acting on cells, to provide an interpretation of how the effects of insoluble biophysical signals can be used to direct stem cells fatein vitro.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 394-394
Author(s):  
Kristin J Hope ◽  
Sonia Cellot ◽  
Stephen Ting ◽  
Guy Sauvageau

Abstract Abstract 394 Hematopoietic stem cells (HSC) can not yet be unambiguously prospectively identified, a fact which has made it difficult to determine whether a segregation of cell fate determinants underlies the asymmetric/symmetric self-renewal of these cells or whether deregulation of such determinants could contribute to the pathogenesis of hematopoietic malignancies by inducing constitutive symmetric self-renewal divisions. We have addressed these questions through a functional genetics approach taking advantage of systematic RNAi to evaluate the function of conserved polarity factors and cell fate determinants in HSCs. From a list of 72 of such factors identified in the literature, 30 murine homologues were chosen based on their differentially higher level of expression in HSC-enriched populations as measured by qRT-PCR. For each candidate we designed 3 unique short hairpin RNA (shRNA) encoding retroviral constructs also carrying EGFP for the purposes of following transduced cells. Primitive hematopoietic cells enriched for HSC were infected at high efficiency with the library in an arrayed 96-well format and their in vivo reconstituting potential was then evaluated through competitive repopulating unit assays. Genes for which shRNA vectors altered late transplant EGFP levels below or above thresholds as defined by a control shRNA to luciferase were considered as hits. Using this approach, we identified and comprehensively validated 4 genes, including the RNA binding protein Msi2, for which shRNA-mediated depletion dramatically impairs repopulation but does not induce cell death or a cell cycle block. Importantly, we show that the loss in the repopulating ability of these shRNA transduced cells is mediated at the stem cell level and is not due to progenitor or downstream cell toxicity or to any defect in the process of bone marrow homing. Subsequent expression profiling indicated that Msi2 is also upregulated in HOXB4-overexpressing symmetrically expanding HSC in line with our findings that it functions as a positive HSC regulator and further suggesting that it represents a potential novel HSC marker. As well as finding HSC agonists, the RNAi screen identified the homeodomain containing transcription factor Prox1 as a negative HSC regulator since its shRNA-mediated transcript loss consistently led to the dramatic in vivo accumulation of EGFP+ transduced cells. Grafts comprised of Prox1 shRNA-transduced cells did not exhibit any lineage skewing however, repeatedly contained an average of 10-fold more primitive Lin-Sca+CD150+48- cells as compared to non-transduced donor cells within the same recipient or to control shRNA-luciferase grafts indicating Prox1 knockdown leads to a significant in vivo expansion of phenotypic HSCs. Moreover, following a 7 day in vitro culture, cells infected with shRNAs to Prox1 were both morphologically and immunophenotypically more primitive than control cells and when transplanted at this time yielded a significantly enhanced engraftment level relative to control shRNAs (51+/-6% GFP vs 8+/-3% GFP). These results further suggest that Prox1 reduction by RNAi expands functional HSCs in vitro. Together these findings have identified conserved cell fate determinants as important and novel regulators of murine hematopoietic stem cells. Disclosures: No relevant conflicts of interest to declare.


2019 ◽  
Vol 2019 ◽  
pp. 1-16 ◽  
Author(s):  
Fei Xing ◽  
Lang Li ◽  
Changchun Zhou ◽  
Cheng Long ◽  
Lina Wu ◽  
...  

It is well known that stem cells reside within tissue engineering functional microenvironments that physically localize them and direct their stem cell fate. Recent efforts in the development of more complex and engineered scaffold technologies, together with new understanding of stem cell behavior in vitro, have provided a new impetus to study regulation and directing stem cell fate. A variety of tissue engineering technologies have been developed to regulate the fate of stem cells. Traditional methods to change the fate of stem cells are adding growth factors or some signaling pathways. In recent years, many studies have revealed that the geometrical microenvironment played an essential role in regulating the fate of stem cells, and the physical factors of scaffolds including mechanical properties, pore sizes, porosity, surface stiffness, three-dimensional structures, and mechanical stimulation may affect the fate of stem cells. Chemical factors such as cell-adhesive ligands and exogenous growth factors would also regulate the fate of stem cells. Understanding how these physical and chemical cues affect the fate of stem cells is essential for building more complex and controlled scaffolds for directing stem cell fate.


Cells ◽  
2020 ◽  
Vol 9 (8) ◽  
pp. 1873 ◽  
Author(s):  
Andrea Remuzzi ◽  
Barbara Bonandrini ◽  
Matteo Tironi ◽  
Lorena Longaretti ◽  
Marina Figliuzzi ◽  
...  

Stem cell fate and behavior are affected by the bidirectional communication of cells and their local microenvironment (the stem cell niche), which includes biochemical cues, as well as physical and mechanical factors. Stem cells are normally cultured in conventional two-dimensional monolayer, with a mechanical environment very different from the physiological one. Here, we compare culture of rat mesenchymal stem cells on flat culture supports and in the “Nichoid”, an innovative three-dimensional substrate micro-engineered to recapitulate the architecture of the physiological niche in vitro. Two versions of the culture substrates Nichoid (single-layered or “2D Nichoid” and multi-layered or “3D Nichoid”) were fabricated via two-photon laser polymerization in a biocompatible hybrid organic-inorganic photoresist (SZ2080). Mesenchymal stem cells, isolated from rat bone marrow, were seeded on flat substrates and on 2D and 3D Nichoid substrates and maintained in culture up to 2 weeks. During cell culture, we evaluated cell morphology, proliferation, cell motility and the expression of a panel of 89 mesenchymal stem cells’ specific genes, as well as intracellular structures organization. Our results show that mesenchymal stem cells adhered and grew in the 3D Nichoid with a comparable proliferation rate as compared to flat substrates. After seeding on flat substrates, cells displayed large and spread nucleus and cytoplasm, while cells cultured in the 3D Nichoid were spatially organized in three dimensions, with smaller and spherical nuclei. Gene expression analysis revealed the upregulation of genes related to stemness and to mesenchymal stem cells’ features in Nichoid-cultured cells, as compared to flat substrates. The observed changes in cytoskeletal organization of cells cultured on 3D Nichoids were also responsible for a different localization of the mechanotransducer transcription factor YAP, with an increase of the cytoplasmic retention in cells cultured in the 3D Nichoid. This difference could be explained by alterations in the import of transcription factors inside the nucleus due to the observed decrease of mean nuclear pore diameter, by transmission electron microscopy. Our data show that 3D distribution of cell volume has a profound effect on mesenchymal stem cells structure and on their mechanobiological response, and highlight the potential use of the 3D Nichoid substrate to strengthen the potential effects of MSC in vitro and in vivo.


Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 800-800
Author(s):  
Sonia Cellot ◽  
Jana Krosl ◽  
Keith Humphries ◽  
Guy Sauvageau

Abstract We previously reported the generation of pluripotent and ultracompetitive HSCs through modulation of Hoxb4 and Pbx1 levels. These Hoxb4hiPbx1lo HSCs display a tremendous regenerative potential, yet they are still fully responsive to in vivo regulatory signals that control stem cell pool size (20 000 HSCmouse) and differentiation pathways. Further work in our laboratory attempted to circumvent these physiological constraints by expanding Hoxb4hiPbx1lo transduced HSCs in vitro, and hence revealing their intrinsic expansion potential. Independent experiments were performed where primary mouse BM cells were co-infected with retroviruses encoding antisense Pbx1 cDNA plus YFP, and Hoxb4 plus GFP (double gene transfer ranged between 20–50%). Hoxb4hiPbx1lo HSCs measured using the CRU assay expanded by 105-fold during a 12 day in vitro culture. Following serial transplantations, these cells displayed an additional 4–5 log expansion in vivo. Total stem cell content per animal remained within normal limits. Southern blot analyses of proviral integrations showed that the expansion was polyclonal, and analyses of individually expanded clones provided a molecular proof of in vitro self-renewal (SR). This unprecedented level of HSC expansion in such a short time course (105-fold in 12 days) implies an absolute HSC doubling time of approximately 17 hours in our culture, raising the possibility that virtually all dividing HSCs undergo self-renewal. This analysis prompted us to dissect the impact of Hoxb4 on cell proliferation versus cell fate (SR?). When analyzed during the period of maximal HSC expansion, the cell cycle distribution of Sca+ or Sca+Lin− cells were comparable between the cultures initiated with neo control versus Hoxb4 BM cells (CTL vs Hoxb4: G0/G1: 66% vs 83%; S: 15% vs 9%; G2/M: 18% vs 7%). Correspondingly, CFSE tracking studies confirmed the identical, or even lower, number of cellular divisions in Sca+ cells isolated from cultures initiated with Hoxb4 versus neo transduced cells. Annexin V studies precluded protection from apoptosis as the major mechanism to increase HSC numbers since similar results (3–10% positive cells) were observed in the Hoxb4 versus neo-transduced cells. In summary, our studies support the emerging concept that distinct molecular pathways regulate cell proliferation and self-renewal, suggesting that Hoxb4 + antisense Pbx1 predominantly triggers self-renewal over HSC proliferation.


2013 ◽  
Vol 2013 ◽  
pp. 1-12 ◽  
Author(s):  
Nazmul Haque ◽  
Mohammad Tariqur Rahman ◽  
Noor Hayaty Abu Kasim ◽  
Aied Mohammed Alabsi

Cell-based regenerative therapies, based onin vitropropagation of stem cells, offer tremendous hope to many individuals suffering from degenerative diseases that were previously deemed untreatable. Due to the self-renewal capacity, multilineage potential, and immunosuppressive property, mesenchymal stem cells (MSCs) are considered as an attractive source of stem cells for regenerative therapies. However, poor growth kinetics, early senescence, and genetic instability duringin vitroexpansion and poor engraftment after transplantation are considered to be among the major disadvantages of MSC-based regenerative therapies. A number of complex inter- and intracellular interactive signaling systems control growth, multiplication, and differentiation of MSCs in their niche. Common laboratory conditions for stem cell culture involve ambient O2concentration (20%) in contrast to their niche where they usually reside in 2–9% O2. Notably, O2plays an important role in maintaining stem cell fate in terms of proliferation and differentiation, by regulating hypoxia-inducible factor-1 (HIF-1) mediated expression of different genes. This paper aims to describe and compare the role of normoxia (20% O2) and hypoxia (2–9% O2) on the biology of MSCs. Finally it is concluded that a hypoxic environment can greatly improve growth kinetics, genetic stability, and expression of chemokine receptors duringin vitroexpansion and eventually can increase efficiency of MSC-based regenerative therapies.


2013 ◽  
Vol 45 (23) ◽  
pp. 1123-1135 ◽  
Author(s):  
David A. Brafman

Within the adult organism, stem cells reside in defined anatomical microenvironments called niches. These architecturally diverse microenvironments serve to balance stem cell self-renewal and differentiation. Proper regulation of this balance is instrumental to tissue repair and homeostasis, and any imbalance can potentially lead to diseases such as cancer. Within each of these microenvironments, a myriad of chemical and physical stimuli interact in a complex (synergistic or antagonistic) manner to tightly regulate stem cell fate. The in vitro replication of these in vivo microenvironments will be necessary for the application of stem cells for disease modeling, drug discovery, and regenerative medicine purposes. However, traditional reductionist approaches have only led to the generation of cell culture methods that poorly recapitulate the in vivo microenvironment. To that end, novel engineering and systems biology approaches have allowed for the investigation of the biological and mechanical stimuli that govern stem cell fate. In this review, the application of these technologies for the dissection of stem cell microenvironments will be analyzed. Moreover, the use of these engineering approaches to construct in vitro stem cell microenvironments that precisely control stem cell fate and function will be reviewed. Finally, the emerging trend of using high-throughput, combinatorial methods for the stepwise engineering of stem cell microenvironments will be explored.


2015 ◽  
Vol 6 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Kazuyuki Ohbo ◽  
Shin-ichi Tomizawa

AbstractStem cells are identified classically by an in vivo transplantation assay plus additional characterization, such as marker analysis, linage-tracing and in vitro/ex vivo differentiation assays. Stem cell lines have been derived, in vitro, from adult tissues, the inner cell mass (ICM), epiblast, and male germ stem cells, providing intriguing insight into stem cell biology, plasticity, heterogeneity, metastable state, and the pivotal point at which stem cells irreversibly differentiate to non-stem cells. During the past decade, strategies for manipulating cell fate have revolutionized our understanding about the basic concept of cell differentiation: stem cell lines can be established by introducing transcription factors, as with the case for iPSCs, revealing some of the molecular interplay of key factors during the course of phenotypic changes. In addition to de-differentiation approaches for establishing stem cells, another method has been developed whereby induced expression of certain transcription factors and/or micro RNAs artificially converts differentiated cells from one committed lineage to another; notably, these cells need not transit through a stem/progenitor state. The molecular cues guiding such cell fate conversion and reprogramming remain largely unknown. As differentiation and de-differentiation are directly linked to epigenetic changes, we overview cell fate decisions, and associated gene and epigenetic regulations.


Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 4374-4374
Author(s):  
Roshanak Ghazanfari ◽  
Hongzhe Li ◽  
Dimitra Zacharaki ◽  
Simón Méndez-Ferrer ◽  
Stefan Scheding

Abstract Human bone marrow contains a rare population of non-hematopoietic mesenchymal stromal cells (BM-MSC) with multilineage differentiation capacity, which are essential constituents of the hematopoietic microenvironment. Self-renewal and differentiation are the two key properties of somatic stem cells, however, stem cell properties of human adult BM-MSC have not been demonstrated conclusively yet. We have previously shown that low/negative expression of PDGFRα on linneg/CD45neg/CD271pos cells identified a highly enriched population of primary BM-MSC in adult human bone marrow (Li et al. Blood, 2013, 122:3699). Based on this work, the current study aimed to investigate the in-vitro and in-vivo stem cell properties of this putative stromal stem cell population. The in-vitro clonogenic potential of freshly sorted human linneg/CD45neg/CD271pos/PDGFRlow/neg cells was evaluated by utilizing the CFU-F assay as well as the recently-developed mesensphere assay, which enables MSC amplification while preserving an immature phenotype (Isern et al, Cell Reports 2013, 30: 1714-24). Comparable colony frequencies were obtained with both assays (19.3 ± 2 and 17.5 ± 2.3 CFU-F and spheres per 100 plated cells, respectively, n=6, p=0.19). In order to test whether both assays identified the same population of clonogenic cells, colonies and spheres were replated under both conditions for up to three generations. The results showed comparable capacities of CFU-F and mesenspheres to form secondary and tertiary CFU-F and spheres. In-vitro self-renewal as indicated by increasing numbers of CFU-F and spheres (416.6 ± 431.7-fold and 49.5 ± 65.7-fold, respectively, n=3) was observed up to the third generation and decreased thereafter. The total number of generations was five (CFU-F) and six (spheres). In-vitro differentiation assays with both, CFU-F- and sphere-derived cells (tested until passage three) demonstrated tri-lineage differentiation potential (adipocytes, osteoblasts, chondrocytes). In addition, CFU-Fs and spheres had comparable surface marker profiles (CD73, CD90, CD105, and HLA-ABC positive; CD31, CD34 and HLA-DR negative), except for CD90, which was higher expressed on CFU-Fs. To investigate in-vivo self-renewal and differentiation potential of the putative stromal stem cells, linneg/CD45neg/CD271pos/PDGFRlow/neg -derived CFU-F and spheres were serially transplanted s.c into NSG mice. After 8 weeks, implants were harvested, human cells were FACS-isolated (CD90 and CD105 expression), and re-assayed under CFU-F and sphere conditions. Whereas in-vivo self-renewal of CFU-F could not be shown (111.5 ± 36 –fold decrease in total CFU-F numbers after primary transplantation, n=3), sphere self-renewal was clearly demonstrated by increased numbers of spheres after primary as well as secondary transplantation (1.13 ± 0.05 and 2.06 ± 0.26 –fold, respectively, n=3), which is remarkable given the fact that the number of recovered human cells is underestimated due to the isolation approach. Here, confirming GFP-marking experiments are ongoing. Finally, preliminary data indicate that linneg/CD45neg/CD271pos/PDGFRlow/neg –derived spheres display full in-vivo differentiation capacity in primary and secondary transplantations. Taken together, our data demonstrate - for the first time - that primary human linneg/CD45neg/CD271pos/PDGFRlow/neg cells meet stringent stem cell criteria, i.e. in-vitro and in-vivo self-renewal and differentiation. These findings answer the long-open question of the potential stem cell properties of adult human MSC and will enable to better understand the properties of native BM-MSC and their biological role in the bone marrow. Disclosures No relevant conflicts of interest to declare.


2012 ◽  
Vol 46 (2) ◽  
pp. 75-80
Author(s):  
Shamoli Bhattacharyya

ABSTRACT Mesenchymal stem cells have shown great promise as the source of adult stem cells for regenerative medicine. Present research efforts are directed at isolating these cells from various sources, growing them in vitro and maintaining their pluripotency as well as capacity for self renewal. It is crucial to identify the regulatory molecules which directly or indirectly control the proliferative status or influence the niche microenvironment. The main challenge is to understand the basic biology of the stem cells and manipulate them for further therapeutic applications. Considering their malignant potential, stem cells may be a double edged sword. While the benefits of these cells need to be harnessed judiciously, a significant amount of research is required before embarking on widespread use of this tool for the benefit of humanity. How to cite this article Bhattacharyya S. Advances and Applications in Stem Cell Biology. J Postgrad Med Edu Res 2012;46(2):75-80.


2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Anqi Guo ◽  
Bingjie Wang ◽  
Cheng Lyu ◽  
Wenjing Li ◽  
Yaozu Wu ◽  
...  

Abstract Background Apparent Young’s modulus (AYM), which reflects the fundamental mechanical property of live cells measured by atomic force microscopy and is determined by substrate stiffness regulated cytoskeletal organization, has been investigated as potential indicators of cell fate in specific cell types. However, applying biophysical cues, such as modulating the substrate stiffness, to regulate AYM and thereby reflect and/or control stem cell lineage specificity for downstream applications, remains a primary challenge during in vitro stem cell expansion. Moreover, substrate stiffness could modulate cell heterogeneity in the single-cell stage and contribute to cell fate regulation, yet the indicative link between AYM and cell fate determination during in vitro dynamic cell expansion (from single-cell stage to multi-cell stage) has not been established. Results Here, we show that the AYM of cells changed dynamically during passaging and proliferation on substrates with different stiffness. Moreover, the same change in substrate stiffness caused different patterns of AYM change in epithelial and mesenchymal cell types. Embryonic stem cells and their derived progenitor cells exhibited distinguishing AYM changes in response to different substrate stiffness that had significant effects on their maintenance of pluripotency and/or lineage-specific characteristics. On substrates that were too rigid or too soft, fluctuations in AYM occurred during cell passaging and proliferation that led to a loss in lineage specificity. On a substrate with ‘optimal’ stiffness (i.e., 3.5 kPa), the AYM was maintained at a constant level that was consistent with the parental cells during passaging and proliferation and led to preservation of lineage specificity. The effects of substrate stiffness on AYM and downstream cell fate were correlated with intracellular cytoskeletal organization and nuclear/cytoplasmic localization of YAP. Conclusions In summary, this study suggests that optimal substrate stiffness regulated consistent AYM during passaging and proliferation reflects and contributes to hESCs and their derived progenitor cells lineage specificity maintenance, through the underlying mechanistic pathways of stiffness-induced cytoskeletal organization and the downstream YAP signaling. These findings highlighted the potential of AYM as an indicator to select suitable substrate stiffness for stem cell specificity maintenance during in vitro expansion for regenerative applications.


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