Human embryonic stem cell-derived mesoderm-like epithelium transitions to mesenchymal progenitor cells

Hyaluronan in mesenchymal stromal cell lineage differentiation from human pluripotent stem cells: application in serum free culture

BACKGROUND

Hyaluronan (HA) is an extracellular glycosaminoglycan polysaccharide with widespread roles throughout development and in healthy and neoplastic tissues. In pluripotent stem cell culture it can support both stem cell renewal and differentiation. However, responses to HA in culture are influenced by interaction with a range of cognate factors and receptors including components of blood serum supplements, which alter results. These may contribute to variation in cell batch production yield and phenotype as well as heighten the risks of adventitious pathogen transmission in the course of cell processing for therapeutic applications. MAIN: Here we characterise differentiation of a human embryo/pluripotent stem cell derived Mesenchymal Stromal Cell (hESC/PSC-MSC)-like cell population by culture on a planar surface coated with HA in serum-free media qualified for cell production for therapy. Resulting cells met minimum criteria of the International Society for Cellular Therapy for identification as MSC by expression of. CD90, CD73, CD105, and lack of expression for CD34, CD45, CD14 and HLA-II. They were positive for other MSC associated markers (i.e.CD166, CD56, CD44, HLA 1-A) whilst negative for others (e.g. CD271, CD71, CD146). In vitro co-culture assessment of MSC associated functionality confirmed support of growth of hematopoietic progenitors and inhibition of mitogen activated proliferation of lymphocytes from umbilical cord and adult peripheral blood mononuclear cells, respectively. Co-culture with immortalized THP-1 monocyte derived macrophages (Mɸ) concurrently stimulated with lipopolysaccharide as a pro-inflammatory stimulus, resulted in a dose dependent increase in pro-inflammatory IL6 but negligible effect on TNFα. To further investigate these functionalities, a bulk cell RNA sequence comparison with adult human bone marrow derived MSC and hESC substantiated a distinctive genetic signature more proximate to the former.

CONCLUSION

Cultivation of human pluripotent stem cells on a planar substrate of HA in serum-free culture media systems is sufficient to yield a distinctive developmental mesenchymal stromal cell lineage with potential to modify the function of haematopoietic lineages in therapeutic applications.

Comparison of the mesodermal differentiation potential between embryonic stem cells and scalable induced pluripotent stem cells

BACKGROUND

Mesenchymal stem cells (MSCs) have promising potential in clinical application, whereas their limited amount and sources hinder their bioavailability. Embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) have become prominent options in regenerative medicine as both possess the ability to differentiate into MSCs.

METHODS

Recently, our research team has successfully developed human leukocyte antigen (HLA)-homozygous iPSC cell lines with high immune compatibility, covering 13.5% of the Taiwanese population. As we deepen our understanding of the differences between these ESCs and HLA-homozygous iPSCs, our study focused on morphological observations and flow cytometry analysis of specific surface marker proteins during the differentiation of ESCs and iPSCs into MSCs.

RESULTS

The results showed no significant differences between the two pluripotent stem cells, and both of them demonstrated the equivalent ability to further differentiate into adipose, cartilage, and bone cells.

CONCLUSION

Our research revealed that these iPSCs with high immune compatibility exhibit the same differentiation potential as ESCs, enhancing the future applicability of highly immune-compatible iPSCs.

Progress and emerging techniques for biomaterial-based derivation of mesenchymal stem cells (MSCs) from pluripotent stem cells (PSCs)

The use of mesenchymal stem cells (MSCs) for clinical purposes has skyrocketed in the past decade. Their multilineage differentiation potentials and immunomodulatory properties have facilitated the discovery of therapies for various illnesses. MSCs can be isolated from infant and adult tissue sources, which means they are easily available. However, this raises concerns because of the heterogeneity among the various MSC sources, which limits their effective use. Variabilities arise from donor- and tissue-specific differences, such as age, sex, and tissue source. Moreover, adult-sourced MSCs have limited proliferation potentials, which hinders their long-term therapeutic efficacy. These limitations of adult MSCs have prompted researchers to develop a new method for generating MSCs. Pluripotent stem cells (PSCs), such as embryonic stem cells and induced PSCs (iPSCs), can differentiate into various types of cells. Herein, a thorough review of the characteristics, functions, and clinical importance of MSCs is presented. The existing sources of MSCs, including adult- and infant-based sources, are compared. The most recent techniques for deriving MSCs from iPSCs, with a focus on biomaterial-assisted methods in both two- and three-dimensional culture systems, are listed and elaborated. Finally, several opportunities to develop improved methods for efficiently producing MSCs with the aim of advancing their various clinical applications are described.

MSCs vs. iPSCs: Potential in therapeutic applications

Over the past 2 decades, mesenchymal stem cells (MSCs) have attracted a lot of interest as a unique therapeutic approach for a variety of diseases. MSCs are capable of self-renewal and multilineage differentiation capacity, immunomodulatory, and anti-inflammatory properties allowing it to play a role in regenerative medicine. Furthermore, MSCs are low in tumorigenicity and immune privileged, which permits the use of allogeneic MSCs for therapies that eliminate the need to collect MSCs directly from patients. Induced pluripotent stem cells (iPSCs) can be generated from adult cells through gene reprogramming with ectopic expression of specific pluripotency factors. Advancement in iPS technology avoids the destruction of embryos to make pluripotent cells, making it free of ethical concerns. iPSCs can self-renew and develop into a plethora of specialized cells making it a useful resource for regenerative medicine as they may be created from any human source. MSCs have also been used to treat individuals infected with the SARS-CoV-2 virus. MSCs have undergone more clinical trials than iPSCs due to high tumorigenicity, which can trigger oncogenic transformation. In this review, we discussed the overview of mesenchymal stem cells and induced pluripotent stem cells. We briefly present therapeutic approaches and COVID-19-related diseases using MSCs and iPSCs.

Application of mesenchymal stem cells derived from human pluripotent stem cells in regenerative medicine

Mesenchymal stem cells (MSCs) represent the most clinically used stem cells in regenerative medicine. However, due to the disadvantages with primary MSCs, such as limited cell proliferative capacity and rarity in the tissues leading to limited MSCs, gradual loss of differentiation during in vitro expansion reducing the efficacy of MSC application, and variation among donors increasing the uncertainty of MSC efficacy, the clinical application of MSCs has been greatly hampered. MSCs derived from human pluripotent stem cells (hPSC-MSCs) can circumvent these problems associated with primary MSCs. Due to the infinite self-renewal of hPSCs and their differentiation potential towards MSCs, hPSC-MSCs are emerging as an attractive alternative for regenerative medicine. This review summarizes the progress on derivation of MSCs from human pluripotent stem cells, disease modelling and drug screening using hPSC-MSCs, and various applications of hPSC-MSCs in regenerative medicine. In the end, the challenges and concerns with hPSC-MSC applications are also discussed.

Pluripotent-derived Mesenchymal Stem/stromal Cells: an Overview of the Derivation Protocol Efficacies and the Differences Among the Derived Cells

Mesenchymal stem/stromal cells (MSCs) are remarkable tools for regenerative medicine. Therapeutic approaches using these cells can promote increased activity and viability in several cell types through diverse mechanisms such as paracrine and immunomodulatory activities, contributing substantially to tissue regeneration and functional recovery. However, biological samples of human MSCs, usually obtained from adult tissues, often exhibit variable behavior during in vitro culture, especially with respect to cell population heterogeneity, replicative senescence, and consequent loss of functionality. Accordingly, it is necessary to establish standard protocols to generate high-quality, stable cell cultures, for example, by using pluripotent stem cells (PSCs) in derivation protocols of MSC-like cells since PSCs maintain their characteristics consistently during culture. However, the available protocols seem to generate distinct populations of PSC-derivedMSCs (PSC-MSCs) with peculiar attributes, which do not always resemble bona fide primary MSCs. The present review addresses the developmental basis behind some of these derivation protocols, exposing the differences among them and discussing the functional properties of PSC-MSCs, shedding light on elements that may help determine standard characterizations and criteria to evaluate and define these cells.

Human Leukocyte Antigen Class I Pseudo-Homozygous Mesenchymal Stem Cells Derived from Human Induced Pluripotent Stem Cells

Mesenchymal stem cells (MSC) are an important type of cell that are highly recognized for their safety and efficacy as a cell therapy agent. In order to obtain MSC, primary tissues (adipose tissue, bone marrow, and umbilical cord blood) must be used; however, these tissues, especially umbilical cord blood, are difficult to obtain due to various reasons, such as the low birth rate trend. In addition, to maximize the safety and efficacy of MSC as allogenic cell therapeutic agents, it is desirable to minimize the possibility of an immune rejection reaction after in vivo transplantation. This study tried to establish a novel method for producing induced pluripotent stem cells (iPSC)-derived MSC in which the human leukocyte antigen (HLA)-class I gene is knocked out. To do so, dermal fibroblast originated iPSC generation using Yamanaka 4-factor, HLA class I gene edited iPSC generation using CRISPR/Cas9, and differentiation from iPSC to MSC using MSC culture medium was utilized. Through this, HLA-A, B, and C pseudo-homozygous iPSC-derived MSC (KO iMSC) were produced by monoallelically knocking out the polymorphic HLA-A, B, and C genes, which are the major causes of immune rejection during allogenic cell transplantation. Produced KO iMSC possesses multipotency and it was safe in vivo to be able to be differentiated to cartilage. In addition, it was not attacked by natural killer cells unlike HLA class I null cells. In conclusion, KO iMSC that do not induce immune rejection during allogenic cell transplantation can be produced. In the future, KO iMSC can be successfully utilized as allogenic cell therapeutic agents for many recipients through HLA screening.

Use of human induced pluripotent stem cells for cartilage regeneration in vitro and within chondral defect models of knee joint cartilage in vivo: a Preferred Reporting Items for Systematic Reviews and Meta-Analyses systematic literature review

BACKGROUND AIMS

Articular cartilage has limited regenerative ability when damaged through trauma or disease. Failure to treat focal chondral lesions results in changes that inevitably progress to osteoarthritis. Osteoarthritis is a major contributor to disability globally, which results in significant medical costs and lost wages every year. Human induced pluripotent stem cells (hiPSCs) have long been considered a potential autologous therapeutic option for the treatment of focal chondral lesions. Although there are significant advantages to hiPSCs over other stem cell options, such as mesenchymal and embryonic stem cells, there are concerns regarding their ability to form bona fide cartilage and their tumorgenicity in vivo.

METHODS

The authors carried out a systematic literature review on the use of hiPSCs to produce differentiated progeny capable of producing high-quality cartilage in vitro and regenerate cartilage in osteochondral defects in vivo in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Eight studies were included in the review that used hiPSCs or their derived progeny in xenogeneic transplants in animal models to regenerate cartilage in osteochondral defects of the knee joint. The in vitro-differentiated, hiPSC-derived and in vivo defect repair ability of the hiPSC-derived progeny transplants were assessed.

RESULTS

Most studies reported the generation of high-quality cartilage-producing progeny that were able to successfully repair cartilage defects in vivo. No tumorigenicity was observed.

CONCLUSIONS

The authors conclude that hiPSCs offer a valuable source of cartilage-producing progeny that show promise as an effective cell-based therapy in treating focal chondral lesions.

Efficient Isolation and Enrichment of Mesenchymal Stem Cells from Human Embryonic Stem Cells by Utilizing the Interaction between Integrin α5β1 and Fibronectin

Human pluripotent stem cells (hPSCs) are a potent source of clinically relevant mesenchymal stem cells (MSCs) that confer functional and structural benefits in cell therapy and tissue regeneration. Obtaining sufficient numbers of MSCs in a short period of time and enhancing the differentiation potential of MSCs can be offered the potential to improve the regenerative activity of MSCs therapy. In addition, the underlying processes in the isolation and derivation of MSCs from hPSCs are still poorly understood and controlled. To overcome these clinical needs, an efficient and simplified technique on the isolation of MSCs from spontaneously differentiated human embryonic stem cells (hESCs) via integrin α5β1 (fibronectin (FN) receptor)-to-FN interactions (hESC-FN-MSCs) is successfully developed. It is demonstrated that hESC-FN-MSCs exhibit a typical MSC surface phenotype, cellular morphology, with the whole transcriptome similar to conventional adult MSCs; but show higher proliferative capacity, more efficient trilineage differentiation, enhanced cytokine secretion, and attenuated cellular senescence. In addition, the therapeutic potential and regenerative capacity of the isolated hESC-FN-MSCs are confirmed by in vitro and in vivo multilineage differentiation. This novel method will be useful in the generation of abundant amounts of clinically relevant MSCs for stem cell therapeutics and regenerative medicine.

Human pluripotent stem cell-derived chondroprogenitors for cartilage tissue engineering

The cartilage of joints, such as meniscus and articular cartilage, is normally long lasting (i.e., permanent). However, once damaged, especially in large animals and humans, joint cartilage is not spontaneously repaired. Compensating the lack of repair activity by supplying cartilage-(re)forming cells, such as chondrocytes or mesenchymal stromal cells, or by transplanting a piece of normal cartilage, has been the basis of therapy for biological restoration of damaged joint cartilage. Unfortunately, current biological therapies face problems on a number of fronts. The joint cartilage is generated de novo from a specialized cell type, termed a 'joint progenitor' or 'interzone cell' during embryogenesis. Therefore, embryonic chondroprogenitors that mimic the property of joint progenitors might be the best type of cell for regenerating joint cartilage in the adult. Pluripotent stem cells (PSCs) are expected to differentiate in culture into any somatic cell type through processes that mimic embryogenesis, making human (h)PSCs a promising source of embryonic chondroprogenitors. The major research goals toward the clinical application of PSCs in joint cartilage regeneration are to (1) efficiently generate lineage-specific chondroprogenitors from hPSCs, (2) expand the chondroprogenitors to the number needed for therapy without loss of their chondrogenic activity, and (3) direct the in vivo or in vitro differentiation of the chondroprogenitors to articular or meniscal (i.e., permanent) chondrocytes rather than growth plate (i.e., transient) chondrocytes. This review is aimed at providing the current state of research toward meeting these goals. We also include our recent achievement of successful generation of "permanent-like" cartilage from long-term expandable, hPSC-derived ectomesenchymal chondroprogenitors.

Differentiation and Establishment of Dental Epithelial-Like Stem Cells Derived from Human ESCs and iPSCs

Tooth development and regeneration occur through reciprocal interactions between epithelial and ectodermal mesenchymal stem cells. However, the current studies on tooth development are limited, since epithelial stem cells are relatively difficult to obtain and maintain. Human embryonic stem cells (hESCs) and induced pluripotent stem cells (hiPSCs) may be alternative options for epithelial cell sources. To differentiate hESCs/hiPSCs into dental epithelial-like stem cells, this study investigated the hypothesis that direct interactions between pluripotent stem cells, such as hESCs or hiPSCs, and Hertwig's epithelial root sheath/epithelial rests of Malassez (HERS/ERM) cell line may induce epithelial differentiation. Epithelial-like stem cells derived from hES (EPI-ES) and hiPSC (EPI-iPSC) had morphological and immunophenotypic characteristics of HERS/ERM cells, as well as similar gene expression. To overcome a rare population and insufficient expansion of primary cells, EPI-iPSC was immortalized with the SV40 large T antigen. The immortalized EPI-iPSC cell line had a normal karyotype, and a short tandem repeat (STR) analysis verified that it was derived from hiPSCs. The EPI-iPSC cell line co-cultured with dental pulp stem cells displayed increased amelogenic and odontogenic gene expression, exhibited higher dentin sialoprotein (DSPP) protein expression, and promoted mineralized nodule formation. These results indicated that the direct co-culture of hESCs/hiPSCs with HERS/ERM successfully established dental epithelial-like stem cells. Moreover, this differentiation protocol could help with understanding the functional roles of cell-to-cell communication and tissue engineering of teeth.

Tissue Engineering Using Vascular Organoids From Human Pluripotent Stem Cell Derived Mural Cell Phenotypes

Diffusion is a limiting factor in regenerating large tissues (100–200 μm) due to reduced nutrient supply and waste removal leading to low viability of the regenerating cells as neovascularization of the implant by the host is a slow process. Thus, generating prevascularized tissue engineered constructs, in which endothelial (ECs) and mural (MCs) cells, such as smooth muscle cells (SMCs), and pericytes (PCs), are preassembled into functional in vitro vessels capable of rapidly connecting to the host vasculature could overcome this obstacle. Toward this purpose, using feeder-free and low serum conditions, we developed a simple, efficient and rapid in vitro approach to induce the differentiation of human pluripotent stem cells-hPSCs (human embryonic stem cells and human induced pluripotent stem cells) to defined SMC populations (contractile and synthetic hPSC-SMCs) by extensively characterizing the cellular phenotype (expression of CD44, CD73, CD105, NG2, PDGFRβ, and contractile proteins) and function of hPSC-SMCs. The latter were phenotypically and functionally stable for at least 8 passages, and could stabilize vessel formation and inhibit vessel network regression, when co-cultured with ECs in vitro. Subsequently, using a methylcellulose-based hydrogel system, we generated spheroids consisting of EC/hPSC-SMC (vascular organoids), which were extensively phenotypically characterized. Moreover, the vascular organoids served as focal starting points for the sprouting of capillary-like structures in vitro, whereas their delivery in vivo led to rapid generation of a complex functional vascular network. Finally, we investigated the vascularization potential of these vascular organoids, when embedded in hydrogels composed of defined extracellular components (collagen/fibrinogen/fibronectin) that can be used as scaffolds in tissue engineering applications. In summary, we developed a robust method for the generation of defined SMC phenotypes from hPSCs. Fabrication of vascularized tissue constructs using hPSC-SMC/EC vascular organoids embedded in chemically defined matrices is a significant step forward in tissue engineering and regenerative medicine.

Where is human-based cellular pharmaceutical R&D taking us in cartilage regeneration?

Lately, cellular-based cartilage joint therapies have gradually gained more attention, which leads to next generation bioengineering approaches in the development of cell-based medicinal products for human use in cartilage repair. The greatest hurdles of chondrocyte-based cartilage bioengineering are: (i) preferring the cell source; (ii) differentiation and expansion processes; (iii) the time necessary for chondrocyte expansion pre-implantation; and (iv) fixing the chondrocyte count in accordance with the lesion surface area of the patient in question. The chondrocyte presents itself to be the focal starting material for research and development of bioengineered cartilage-based medicinal products which promise the regeneration and restoration of non-orthopedic cartilage joint defects. Even though chondrocytes seem to be the first choice, inevitable complications related to proliferation, dedifferentation and redifferentiation are probable. Detailed studies are a necessity to fully investigate detailed culturing conditions, the chondrogenic strains of well-defined phenotypes and evaluation of the methods to be used in biomaterial production. Despite a majority of the current methods which aid amelioration of joint functionality, they are insufficient in fully restoring the natural structure and composition of the joint cartilage. Hence current studies have trended towards gene therapy, mesenchymal stem cells and tissue engineering practices. There are many studies addressing the outcomes of chondrocytes in the clinical scene, and many vital biomaterials have been developed for structuring the bioengineered cartilage. This study aims to convey to the audience the practical significance of chondrocyte-based clinical applications.

Chondrogenic Differentiation from Induced Pluripotent Stem Cells Using Non-Viral Minicircle Vectors

Human degenerative cartilage has low regenerative potential. Chondrocyte transplantation offers a promising strategy for cartilage treatment and regeneration. Currently, chondrogenesis using human pluripotent stem cells (hiPSCs) is accomplished using human recombinant growth factors. Here, we differentiate hiPSCs into chondrogenic pellets using minicircle vectors. Minicircles are a non-viral gene delivery system that can produce growth factors without integration into the host genome. We generated minicircle vectors containing bone morphogenetic protein 2 (BMP2) and transforming growth factor beta 3 (TGFβ3) and delivered them to mesenchymal stem cell-like, hiPSC-derived outgrowth (OG) cells. Cell pellets generated using minicircle-transfected OG cells successfully differentiated into the chondrogenic lineage. The implanted minicircle-based chondrogenic pellets recovered the osteochondral defects in rat models. This work is a proof-of-concept study that describes the potential application of minicircle vectors in cartilage regeneration using hiPSCs.

Phenotypic Variation Between Stromal Cells Differentially Impacts Engineered Cardiac Tissue Function

IMPACT STATEMENT

Understanding the relationship between parenchymal and supporting cell populations is paramount to recapitulate the multicellular complexity of native tissues. Incorporation of stromal cells is widely recognized to be necessary for the stable formation of stem cell-derived cardiac tissues; yet, the types of stromal cells used have varied widely. This study systematically characterized several stromal populations and found that stromal phenotype and morphology was highly variable depending on cell source and exerted differential impacts on cardiac tissue function and induced pluripotent stem cell-cardiomyocyte phenotype. Therefore, the choice of supporting stromal population can differentially impact the phenotypic or functional performance of engineered cardiac tissues.

A Systems-level Characterization of the Differentiation of Human Embryonic Stem Cells into Mesenchymal Stem Cells

Mesenchymal stem/stromal cells (MSCs) are self-renewing multipotent cells with regenerative, secretory and immunomodulatory capabilities that are beneficial for the treatment of various diseases. To avoid the issues that come with using tissue-derived MSCs in therapy, MSCs may be generated by the differentiation of human embryonic stems cells (hESCs) in culture. However, the changes that occur during the differentiation process have not been comprehensively characterized. Here, we combined transcriptome, proteome and phosphoproteome profiling to perform an in-depth, multi-omics study of the hESCs-to-MSCs differentiation process. Based on RNA-to-protein correlation, we determined a set of high confidence genes that are important to differentiation. Among the earliest and strongest induced proteins with extensive differential phosphorylation was AHNAK, which we hypothesized to be a defining factor in MSC biology. We observed two distinct expression waves of developmental HOX genes and an AGO2-to-AGO3 switch in gene silencing. Exploring the kinetic of noncoding ORFs during differentiation, we mapped new functions to well annotated long noncoding RNAs (CARMN, MALAT, NEAT1, LINC00152) as well as new candidates which we identified to be important to the differentiation process. Phosphoproteome analysis revealed ESC and MSC-specific phosphorylation motifs with PAK2 and RAF1 as top predicted upstream kinases in MSCs. Our data represent a rich systems-level resource on ESC-to-MSC differentiation that will be useful for the study of stem cell biology.

Multiplicity of Mesenchymal Stromal Cells: Finding the Right Route to Therapy

Over the last decade, the acceleration in the clinical use of mesenchymal stromal cells (MSCs) has been nothing short of spectacular. Perhaps most surprising is how little we know about the "MSC product." Although MSCs are being delivered to patients at an alarming rate, the regulatory requirements for MSC therapies (for example in terms of quality assurance and quality control) are nowhere near the expectations of traditional pharmaceuticals. That said, the standards that define a chemical compound or purified recombinant protein cannot be applied with the same stringency to a cell-based therapy. Biological processes are dynamic, adaptive and variable. Heterogeneity will always exist or emerge within even the most rigorously sorted clonal cell populations. With MSCs, perhaps more so than any other therapeutic cell, heterogeneity pervades at multiple levels, from the sample source to the single cell. The research and clinical communities collectively need to recognize and take steps to address this troublesome truth, to ensure that the promise of MSC-based therapies is fulfilled.

From skeletal development to the creation of pluripotent stem cell-derived bone-forming progenitors

Bone has many functions. It is responsible for protecting the underlying soft organs, it allows locomotion, houses the bone marrow and stores minerals such as calcium and phosphate. Upon damage, bone tissue can efficiently repair itself. However, healing is hampered if the defect exceeds a critical size and/or is in compromised conditions. The isolation or generation of bone-forming progenitors has applicability to skeletal repair and may be used in tissue engineering approaches. Traditionally, bone engineering uses osteochondrogenic stem cells, which are combined with scaffold materials and growth factors. Despite promising preclinical data, limited translation towards the clinic has been observed to date. There may be several reasons for this including the lack of robust cell populations with favourable proliferative and differentiation capacities. However, perhaps the most pertinent reason is the failure to produce an implant that can replicate the developmental programme that is observed during skeletal repair. Pluripotent stem cells (PSCs) can potentially offer a solution for bone tissue engineering by providing unlimited cell sources at various stages of differentiation. In this review, we summarize key embryonic signalling pathways in bone formation coupled with PSC differentiation strategies for the derivation of bone-forming progenitors.This article is part of the theme issue 'Designer human tissue: coming to a lab near you'.

Production of Mesenchymal Stem Cells Through Stem Cell Reprogramming

Mesenchymal stem cells (MSCs) possess a broad spectrum of therapeutic applications and have been used in clinical trials. MSCs are mainly retrieved from adult or fetal tissues. However, there are many obstacles with the use of tissue-derived MSCs, such as shortages of tissue sources, difficult and invasive retrieval methods, cell population heterogeneity, low purity, cell senescence, and loss of pluripotency and proliferative capacities over continuous passages. Therefore, other methods to obtain high-quality MSCs need to be developed to overcome the limitations of tissue-derived MSCs. Pluripotent stem cells (PSCs), including embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), are considered potent sources for the derivation of MSCs. PSC-derived MSCs (PSC-MSCs) may surpass tissue-derived MSCs in proliferation capacity, immunomodulatory activity, and in vivo therapeutic applications. In this review, we will discuss basic as well as recent protocols for the production of PSC-MSCs and their in vitro and in vivo therapeutic efficacies. A better understanding of the current advances in the production of PSC-MSCs will inspire scientists to devise more efficient differentiation methods that will be a breakthrough in the clinical application of PSC-MSCs.

Comparison of human isogeneic Wharton's jelly MSCs and iPSC-derived MSCs reveals differentiation-dependent metabolic responses to IFNG stimulation

Variability among donors, non-standardized methods for isolation, and characterization contribute to mesenchymal stem/stromal cell (MSC) heterogeneity. Induced pluripotent stem cell (iPSCs)-derived MSCs would circumvent many of current issues and enable large-scale production of standardized cellular therapy. To explore differences between native MSCs (nMSCs) and iPSC-derived MSCs (iMSCs), we developed isogeneic lines from Wharton’s jelly (WJ) from the umbilical cords of two donors (#12 and #13) under xeno-free conditions. Next, we reprogrammed them into iPSCs (iPSC12 and iPSC13) and subsequently differentiated them back into iMSCs (iMSC12 and iMSC13) using two different protocols, which we named ARG and TEX. We assessed their differentiation capability, transcriptome, immunomodulatory potential, and interferon-γ (IFNG)-induced changes in metabolome. Our data demonstrated that although both differentiation protocols yield iMSCs similar to their parental nMSCs, there are substantial differences. The ARG protocol resulted in iMSCs with a strong immunomodulatory potential and lower plasticity and proliferation rate, whereas the TEX protocol raised iMSCs with a higher proliferation rate, better differentiation potential, though weak immunomodulatory response. Our data suggest that, following a careful selection and screening of donors, nMSCs from umbilical’s cord WJ can be easily reprogrammed into iPSCs, providing an unlimited source of material for differentiation into iMSCs. However, the differentiation protocol should be chosen depending on their clinical use.

Generation and Applications of Induced Pluripotent Stem Cell-Derived Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are adult stem cells with fibroblast-like morphology and isolated from the bone marrow via plastic adhesion. Their multipotency and immunoregulatory properties make MSCs possible therapeutic agents, and an increasing number of publications and clinical trials have highlighted their potential in regenerative medicine. However, the finite proliferative capacity of MSCs limits their scalability and global dissemination as a standardized therapeutic product. Furthermore, adult tissue provenance could constrain accessibility, impinge on cellular potency, and incur greater exposure to disease-causing pathogens based on the donor. These issues could be circumvented by the derivation of MSCs from pluripotent stem cells. In this paper, we review methods that induce and characterize MSCs derived from induced pluripotent stem cells (iPSCs) and introduce MSC applications to disease modeling, pathogenic mechanisms, and drug discovery. We also discuss the potential applications of MSCs in regenerative medicine including cell-based therapies and issues that should be overcome before iPSC-derived MSC therapy will be applied in the clinic.

MSX2 Initiates and Accelerates Mesenchymal Stem/Stromal Cell Specification of hPSCs by Regulating TWIST1 and PRAME

The gap in knowledge of the molecular mechanisms underlying differentiation of human pluripotent stem cells (hPSCs) into the mesenchymal cell lineages hinders the application of hPSCs for cell-based therapy. In this study, we identified a critical role of muscle segment homeobox 2 (MSX2) in initiating and accelerating the molecular program that leads to mesenchymal stem/stromal cell (MSC) differentiation from hPSCs. Genetic deletion of MSX2 impairs hPSC differentiation into MSCs. When aided with a cocktail of soluble molecules, MSX2 ectopic expression induces hPSCs to form nearly homogeneous and fully functional MSCs. Mechanistically, MSX2 induces hPSCs to form neural crest cells, an intermediate cell stage preceding MSCs, and further differentiation by regulating TWIST1 and PRAME. Furthermore, we found that MSX2 is also required for hPSC differentiation into MSCs through mesendoderm and trophoblast. Our findings provide novel mechanistic insights into lineage specification of hPSCs to MSCs and effective strategies for applications of stem cells for regenerative medicine.

Embryonic Stem Cell-Derived Mesenchymal Stem Cells (MSCs) Have a Superior Neuroprotective Capacity Over Fetal MSCs in the Hypoxic-Ischemic Mouse Brain

Human mesenchymal stem cells (MSCs) have huge potential for regenerative medicine. In particular, the use of pluripotent stem cell‐derived mesenchymal stem cells (PSC‐MSCs) overcomes the hurdle of replicative senescence associated with the in vitro expansion of primary cells and has increased therapeutic benefits in comparison to the use of various adult sources of MSCs in a wide range of animal disease models. On the other hand, fetal MSCs exhibit faster growth kinetics and possess longer telomeres and a wider differentiation potential than adult MSCs. Here, for the first time, we compare the therapeutic potential of PSC‐MSCs (ES‐MSCs from embryonic stem cells) to fetal MSCs (AF‐MSCs from the amniotic fluid), demonstrating that ES‐MSCs have a superior neuroprotective potential over AF‐MSCs in the mouse brain following hypoxia‐ischemia. Further, we demonstrate that nuclear factor (NF)‐κB‐stimulated interleukin (IL)‐13 production contributes to an increased in vitro anti‐inflammatory potential of ES‐MSC‐conditioned medium (CM) over AF‐MSC‐CM, thus suggesting a potential mechanism for this observation. Moreover, we show that induced pluripotent stem cell‐derived MSCs (iMSCs) exhibit many similarities to ES‐MSCs, including enhanced NF‐κB signaling and IL‐13 production in comparison to AF‐MSCs. Future studies should assess whether iMSCs also exhibit similar neuroprotective potential to ES‐MSCs, thus presenting a potential strategy to overcome the ethical issues associated with the use of embryonic stem cells and providing a potential source of cells for autologous use against neonatal hypoxic‐ischemic encephalopathy in humans. Stem Cells Translational Medicine2018;7:439–449

The utility of stem cells in pediatric urinary bladder regeneration

Pediatric patients with a neurogenic urinary bladder, caused by developmental abnormalities including spina bifida, exhibit chronic urological problems. Surgical management in the form of enterocystoplasty is used to enlarge the bladder, but is associated with significant clinical complications. Thus, alternative methods to enterocystoplasty have been explored through the incorporation of stem cells with tissue engineering strategies. Within the context of this review, we will examine the use of bone marrow stem cells and induced pluripotent stem cells (iPSCs), as they relate to bladder regeneration at the anatomic and molecular levels. The use of bone marrow stem cells has demonstrated significant advances in bladder tissue regeneration as multiple aspects of bladder tissue have been recapitulated including the urothelium, bladder smooth muscle, vasculature, and peripheral nerves. iPSCs, on the other hand, have been well characterized and used in multiple tissue-regenerative settings, yet iPSC research is still in its infancy with regards to bladder tissue regeneration with recent studies describing the differentiation of iPSCs to the bladder urothelium. Finally, we examine the role of the Sonic Hedgehog signaling cascade that mediates the proliferative response during regeneration between bladder smooth muscle and urothelium. Taken together, this review provides a current, comprehensive perspective on bladder regeneration.

Human Neural Stem Cell Extracellular Vesicles Improve Tissue and Functional Recovery in the Murine Thromboembolic Stroke Model

Over 700 drugs have failed in stroke clinical trials, an unprecedented rate thought to be attributed in part to limited and isolated testing often solely in “young” rodent models and focusing on a single secondary injury mechanism. Here, extracellular vesicles (EVs), nanometer-sized cell signaling particles, were tested in a mouse thromboembolic (TE) stroke model. Neural stem cell (NSC) and mesenchymal stem cell (MSC) EVs derived from the same pluripotent stem cell (PSC) line were evaluated for changes in infarct volume as well as sensorimotor function. NSC EVs improved cellular, tissue, and functional outcomes in middle-aged rodents, whereas MSC EVs were less effective. Acute differences in lesion volume following NSC EV treatment were corroborated by MRI in 18-month-old aged rodents. NSC EV treatment has a positive effect on motor function in the aged rodent as indicated by beam walk, instances of foot faults, and strength evaluated by hanging wire test. Increased time with a novel object also indicated that NSC EVs improved episodic memory formation in the rodent. The therapeutic effect of NSC EVs appears to be mediated by altering the systemic immune response. These data strongly support further preclinical development of a NSC EV-based stroke therapy and warrant their testing in combination with FDA-approved stroke therapies.

Pluripotent Stem Cells as a Robust Source of Mesenchymal Stem Cells

Mesenchymal stem cells (MSC) have been extensively studied over the past years for the treatment of different diseases. Most of the ongoing clinical trials currently involve the use of MSC derived from adult tissues. This source may have some limitations, particularly with therapies that may require extensive and repetitive cell dosage. However, nowadays, there is a staggering growth in literature on a new source of MSC. There is now increasing evidence about the mesenchymal differentiation from pluripotent stem cell (PSC). Here, we summarize the current knowledge of pluripotent-derived mesenchymal stem cells (PD-MSC). We present a historical perspective on the subject, and then discuss some critical questions that remain unanswered.

Human Embryonic Stem Cell-Derived Oligodendrocyte Progenitor Cells: Preclinical Efficacy and Safety in Cervical Spinal Cord Injury

Cervical spinal cord injury (SCI) remains an important research focus for regenerative medicine given the potential for severe functional deficits and the current lack of treatment options to augment neurological recovery. We recently reported the preclinical safety data of a human embryonic cell‐derived oligodendrocyte progenitor cell (OPC) therapy that supported initiation of a phase I clinical trial for patients with sensorimotor complete thoracic SCI. To support the clinical use of this OPC therapy for cervical injuries, we conducted preclinical efficacy and safety testing of the OPCs in a nude rat model of cervical SCI. Using the automated TreadScan system to track motor behavioral recovery, we found that OPCs significantly improved locomotor performance when administered directly into the cervical spinal cord 1 week after injury, and that this functional improvement was associated with reduced parenchymal cavitation and increased sparing of myelinated axons within the injury site. Based on large scale biodistribution and toxicology studies, we show that OPC migration is limited to the spinal cord and brainstem and did not cause any adverse clinical observations, toxicities, allodynia, or tumors. In combination with previously published efficacy and safety data, the results presented here supported initiation of a phase I/IIa clinical trial in the U.S. for patients with sensorimotor complete cervical SCI. Stem Cells Translational Medicine2017;6:1917–1929

Mesenchymal stem cells and their therapeutic applications in inflammatory bowel disease

Mesenchymal stem or stromal cells (MSCs) are non-hematopoietic stem cells that facilitate tissue regeneration through mechanisms involving self-renewal and differentiation, supporting angiogenesis and tissue cell survival, and limiting inflammation. MSCs were originally identified and expanded in long-term cultures of cells from bone marrow and other organs; and their native identity was recently confined into pericytes and adventitial cells in vascularized tissue. The multipotency, as well as the trophic and immunosuppressive effects, of MSCs have prompted the rapid development of clinical applications for many diseases involving tissue inflammation and immune disorders, including inflammatory bowel disease. Although standard criteria have been established to define MSCs, their therapeutic efficacy has varied significantly among studies due to their natural heterogenicity. Thus, understanding the biological and immunological features of MSCs is critical to standardize and optimize MSCs-based therapy. In this review, we highlight the cellular and molecular mechanisms involved in MSCs-mediated tissue repair and immunosuppression. We also provide an update on the current development of MSCs-based clinical trials, with a detailed discussion of MSC-based cell therapy in inflammatory bowel disease.

Characterization of Mesenchymal Stem Cell-Like Cells Derived From Human iPSCs via Neural Crest Development and Their Application for Osteochondral Repair

Mesenchymal stem cells (MSCs) derived from induced pluripotent stem cells (iPSCs) are a promising cell source for the repair of skeletal disorders. Recently, neural crest cells (NCCs) were reported to be effective for inducing mesenchymal progenitors, which have potential to differentiate into osteochondral lineages. Our aim was to investigate the feasibility of MSC-like cells originated from iPSCs via NCCs for osteochondral repair. Initially, MSC-like cells derived from iPSC-NCCs (iNCCs) were generated and characterized in vitro. These iNCC-derived MSC-like cells (iNCMSCs) exhibited a homogenous population and potential for osteochondral differentiation. No upregulation of pluripotent markers was detected during culture. Second, we implanted iNCMSC-derived tissue-engineered constructs into rat osteochondral defects without any preinduction for specific differentiation lineages. The implanted cells remained alive at the implanted site, whereas they failed to repair the defects, with only scarce development of osteochondral tissue in vivo. With regard to tumorigenesis, the implanted cells gradually disappeared and no malignant cells were detected throughout the 2-month follow-up. While this study did not show that iNCMSCs have efficacy for repair of osteochondral defects when implanted under undifferentiated conditions, iNCMSCs exhibited good chondrogenic potential in vitro under appropriate conditions. With further optimization, iNCMSCs may be a new source for tissue engineering of cartilage.

Adipogenic differentiation of culture-expanded bone marrow derived porcine mesenchymal stem cells

In order to use Mesenchymal stem cell populations for obesity and related metabolic syndrome studies in cell culture system, as a prerequisite, we evaluated the potency of these stem cells to undergo adipogenic differentiation. Porcine stem cells were chosen to study adipogenesis in due to the fact that pig has a natural tendency to get obese and the species is considered to be the most desired biomedical model for human applications. Porcine MSCs have been exposed to adipogenic induction media following a 21day protocol and observed under microscope for detecting stages of differentiation. At the terminal differentiation stage; morphologically, the cells appeared rounded with numerous large cytosolic lipid spheres. Upon staining with Oil Red O, the lipid spheres stained bright red. Based on this, proprietary medium was found to differentiate MSCs more efficiently than medium formulated on previous reports. Both, the differential morphologic feature corresponding to the adipocyte and positive Oil Red O staining confirmed about successful adipogenic differentiation. We envision that stem cell based culture system from porcine species would aid for studying molecular adipogenesis and subsequent identification of therapeutic targets for obesity and other metabolic diseases.

Transgene Reactivation in Induced Pluripotent Stem Cell Derivatives and Reversion to Pluripotency of Induced Pluripotent Stem Cell-Derived Mesenchymal Stem Cells

Induced pluripotent stem cells (iPSCs) have enormous potential in regenerative medicine and disease modeling. It is now felt that clinical trials should be performed with iPSCs derived with nonintegrative constructs. Numerous studies, however, including those describing disease models, are still being published using cells derived from iPSCs generated with integrative constructs. Our experimental work presents the first evidence of spontaneous transgene reactivation in vitro in several cellular types. Our results show that the transgenes were predominantly silent in parent iPSCs, but in mesenchymal and endothelial iPSC derivatives, the transgenes experienced random upregulation of Nanog and c-Myc. Additionally, we provide evidence of spontaneous secondary reprogramming and reversion to pluripotency in mesenchymal stem cells derived from iPSCs. These findings strongly suggest that the studies, which use cellular products derived from iPSCs generated with retro- or lentiviruses, should be evaluated with consideration of the possibility of transgene reactivation. The in vitro model described here provides insight into the earliest events of culture transformation and suggests the hypothesis that reversion to pluripotency may be responsible for the development of tumors in cell replacement experiments. The main goal of this work, however, is to communicate the possibility of transgene reactivation in retro- or lenti-iPSC derivatives and the associated loss of cellular fidelity in vitro, which may impact the outcomes of disease modeling and related experimentation.

Chondrogenesis of Embryonic Stem Cell-Derived Mesenchymal Stem Cells Induced by TGFβ1 and BMP7 Through Increased TGFβ Receptor Expression and Endogenous TGFβ1 Production

For decades stem cells have proven to be invaluable to the study of tissue development. More recently, mesenchymal stem cells (MSCs) derived from embryonic stem cells (ESCs) (ESC-MSCs) have emerged as a cell source with great potential for the future of biomedical research due to their enhanced proliferative capability compared to adult tissue-derived MSCs and effectiveness of musculoskeletal lineage-specific cell differentiation compared to ESCs. We have previously compared the properties and differentiation potential of ESC-MSCs to bone marrow-derived MSCs. In this study, we evaluated the potential of TGFβ1 and BMP7 to induce chondrogenic differentiation of ESC-MSCs compared to that of TGFβ1 alone and further investigated the cellular phenotype and intracellular signaling in response to these induction conditions. Our results showed that the expression of cartilage-associated markers in ESC-MSCs induced by the TGFβ1 and BMP7 combination was increased compared to induction with TGFβ1 alone. The TGFβ1 and BMP7 combination upregulated the expression of TGFβ receptor and the production of endogenous TGFβs compared to TGFβ1 induction. The growth factor combination also increasingly activated both of the TGF and BMP signaling pathways, and inhibition of the signaling pathways led to reduced chondrogenesis of ESC-MSCs. Our findings suggest that by adding BMP7 to TGFβ1-supplemented induction medium, ESC-MSC chondrogenesis is upregulated through increased production of endogenous TGFβ and activities of TGFβ and BMP signaling. J. Cell. Biochem. 118: 172-181, 2017. © 2016 Wiley Periodicals, Inc.

hiPSC-derived iMSCs: NextGen MSCs as an advanced therapeutically active cell resource for regenerative medicine

Mesenchymal stem cells (MSCs) are being assessed for ameliorating the severity of graft‐versus‐host disease, autoimmune conditions, musculoskeletal injuries and cardiovascular diseases. While most of these clinical therapeutic applications require substantial cell quantities, the number of MSCs that can be obtained initially from a single donor remains limited. The utility of MSCs derived from human‐induced pluripotent stem cells (hiPSCs) has been shown in recent pre‐clinical studies. Since adult MSCs have limited capability regarding proliferation, the quantum of bioactive factor secretion and immunomodulation ability may be constrained. Hence, the alternate source of MSCs is being considered to replace the commonly used adult tissue‐derived MSCs. The MSCs have been obtained from various adult and foetal tissues. The hiPSC‐derived MSCs (iMSCs) are transpiring as an attractive source of MSCs because during reprogramming process, cells undergo rejuvination, exhibiting better cellular vitality such as survival, proliferation and differentiations potentials. The autologous iMSCs could be considered as an inexhaustible source of MSCs that could be used to meet the unmet clinical needs. Human‐induced PSC‐derived MSCs are reported to be superior when compared to the adult MSCs regarding cell proliferation, immunomodulation, cytokines profiles, microenvironment modulating exosomes and bioactive paracrine factors secretion. Strategies such as derivation and propagation of iMSCs in chemically defined culture conditions and use of footprint‐free safer reprogramming strategies have contributed towards the development of clinically relevant cell types. In this review, the role of iPSC‐derived mesenchymal stromal cells (iMSCs) as an alternate source of therapeutically active MSCs has been described. Additionally, we also describe the role of iMSCs in regenerative medical applications, the necessary strategies, and the regulatory policies that have to be enforced to render iMSC's effectiveness in translational medicine.

Comprehensive transcriptomic and proteomic characterization of human mesenchymal stem cells reveals source specific cellular markers

Mesenchymal stem cells (MSC) are multipotent cells with great potential in therapy, reflected by more than 500 MSC-based clinical trials registered with the NIH. MSC are derived from multiple tissues but require invasive harvesting and imply donor-to-donor variability. Embryonic stem cell-derived MSC (ESC-MSC) may provide an alternative, but how similar they are to ex vivo MSC is unknown. Here we performed an in depth characterization of human ESC-MSC, comparing them to human bone marrow-derived MSC (BM-MSC) as well as human embryonic stem cells (hESC) by transcriptomics (RNA-seq) and quantitative proteomics (nanoLC-MS/MS using SILAC). Data integration highlighted and validated a central role of vesicle-mediated transport and exosomes in MSC biology and also demonstrated, through enrichment analysis, their versatility and broad application potential. Particular emphasis was placed on comparing profiles between ESC-MSC and BM-MSC and assessing their equivalency. Data presented here shows that differences between ESC-MSC and BM-MSC are similar in magnitude to those reported for MSC of different origin and the former may thus represent an alternative source for therapeutic applications. Finally, we report an unprecedented coverage of MSC CD markers, as well as membrane associated proteins which may benefit immunofluorescence-based applications and contribute to a refined molecular description of MSC.

Improved approach for chondrogenic differentiation of human induced pluripotent stem cells

Human induced pluripotent stem cells (hiPSCs) have demonstrated great potential for hyaline cartilage regeneration. However, current approaches for chondrogenic differentiation of hiPSCs are complicated and inefficient primarily due to intermediate embryoid body formation, which is required to generate endodermal, ectodermal, and mesodermal cell lineages. We report a new, straightforward and highly efficient approach for chondrogenic differentiation of hiPSCs, which avoids embryoid body formation. We differentiated hiPSCs directly into mesenchymal stem /stromal cells (MSC) and chondrocytes. hiPSC-MSC-derived chondrocytes showed significantly increased Col2A1, GAG, and SOX9 gene expression compared to hiPSC-MSCs. Following transplantation of hiPSC-MSC and hiPSC-MSC-derived chondrocytes into osteochondral defects of arthritic joints of athymic rats, magnetic resonance imaging studies showed gradual engraftment, and histological correlations demonstrated hyaline cartilage matrix production. Results present an efficient and clinically translatable approach for cartilage tissue regeneration via patient-derived hiPSCs, which could improve cartilage regeneration outcomes in arthritic joints.

A self-setting iPSMSC-alginate-calcium phosphate paste for bone tissue engineering

OBJECTIVES

Calcium phosphate cements (CPCs) are promising for dental and craniofacial repairs. The objectives of this study were to: (1) develop an injectable cell delivery system based on encapsulation of induced pluripotent stem cell-derived mesenchymal stem cells (iPSMSCs) in microbeads; (2) develop a novel tissue engineered construct by dispersing iPSMSC-microbeads in CPC to investigate bone regeneration in an animal model for the first time.

METHODS

iPSMSCs were pre-osteoinduced for 2 weeks (OS-iPSMSCs), or transduced with bone morphogenetic protein-2 (BMP2-iPSMSCs). Cells were encapsulated in fast-degradable alginate microbeads. Microbeads were mixed with CPC paste and filled into cranial defects in nude rats. Four groups were tested: (1) CPC-microbeads without cells (CPC control); (2) CPC-microbeads-iPSMSCs (CPC-iPSMSCs); (3) CPC-microbeads-OS-iPSMSCs (CPC-OS-iPSMSCs); (4) CPC-microbeads-BMP2-iPSMSCs (CPC-BMP2-iPSMSCs).

RESULTS

Cells maintained good viability inside microbeads after injection. The microbeads were able to release the cells which had more than 10-fold increase in live cell density from 1 to 14 days. The cells exhibited up-regulation of osteogenic markers and deposition of minerals. In vivo, new bone area fraction (mean±SD; n=5) for CPC-iPSMSCs group was (22.5±7.6)%. New bone area fractions were (38.9±18.4)% and (44.7±22.8)% for CPC-OS-iPSMSCs group and CPC-BMP2-iPSMSCs group, respectively, 2-3 times the (15.6±11.2)% in CPC control at 12 weeks (p<0.05). Cell-CPC constructs accelerated scaffold resorption, with CPC-BMP2-iPSMSCs having remaining scaffold material that was 7-fold less than CPC control.

SIGNIFICANCE

Novel injectable CPC-microbead-cell constructs promoted bone regeneration, with OS-iPSMSCs and BMP2-iPSMSCs having 2-3 fold the new bone of CPC control. Cell delivery accelerated scaffold resorption, with CPC-BMP2-iPSMSC having remaining scaffold material that was 7-fold less than CPC control. Therefore, CPC-microbead-iPSMSC is a promising injectable material for orthopedic, dental and craniofacial bone regenerations.

Restoration of Physiologically Responsive Low-Density Lipoprotein Receptor-Mediated Endocytosis in Genetically Deficient Induced Pluripotent Stem Cells

Acquiring sufficient amounts of high-quality cells remains an impediment to cell-based therapies. Induced pluripotent stem cells (iPSC) may be an unparalleled source, but autologous iPSC likely retain deficiencies requiring correction. We present a strategy for restoring physiological function in genetically deficient iPSC utilizing the low-density lipoprotein receptor (LDLR) deficiency Familial Hypercholesterolemia (FH) as our model. FH fibroblasts were reprogrammed into iPSC using synthetic modified mRNA. FH-iPSC exhibited pluripotency and differentiated toward a hepatic lineage. To restore LDLR endocytosis, FH-iPSC were transfected with a 31 kb plasmid (pEHZ-LDLR-LDLR) containing a wild-type LDLR (FH-iPSC-LDLR) controlled by 10 kb of upstream genomic DNA as well as Epstein-Barr sequences (EBNA1 and oriP) for episomal retention and replication. After six months of selective culture, pEHZ-LDLR-LDLR was recovered from FH-iPSC-LDLR and transfected into Ldlr-deficient CHO-a7 cells, which then exhibited feedback-controlled LDLR-mediated endocytosis. To quantify endocytosis, FH-iPSC ± LDLR were differentiated into mesenchymal cells (MC), pretreated with excess free sterols, Lovastatin, or ethanol (control), and exposed to DiI-LDL. FH-MC-LDLR demonstrated a physiological response, with virtually no DiI-LDL internalization with excess sterols and an ~2-fold increase in DiI-LDL internalization by Lovastatin compared to FH-MC. These findings demonstrate the feasibility of functionalizing genetically deficient iPSC using episomal plasmids to deliver physiologically responsive transgenes.

Mesenchymal stem cells derived from human induced pluripotent stem cells retain adequate osteogenicity and chondrogenicity but less adipogenicity

Introduction

Previously, we established a simple method for deriving mesenchymal stem cells (MSCs) from human induced pluripotent stem cells (iPSC-MSCs). These iPSC-MSCs were capable of forming osteogenic structures in scaffolds and nanofibers. The objective of this study is to systematically characterize the mesenchymal characteristics of the iPSC-MSCs by comparing them to bone marrow-derived MSCs (BM-MSCs).

Methods

Two iPSC-MSC lines (named as mRNA-iPSC-MSC-YL001 and lenti-iPSC-MSC-A001) and one BM-MSC line were used for the study. Cell proliferation, presence of mesenchymal surface markers, tri-lineage differentiation capability (osteogenesis, chondrogenesis, adipogenesis), and expression of “stemness” genes were analyzed in these MSC lines.

Results

The iPSC-MSCs were similar to BM-MSCs in terms of cell morphology (fibroblast-like) and surface antigen profile: CD29+, CD44+, CD73+, CD90+, CD105+, CD11b–, CD14–, CD31–, CD34–, CD45– and HLA-DR–. A faster proliferative capability was seen in both iPSC-MSCs lines compared to the BM-MSCs. The iPSC-MSCs showed adequate capacity of osteogenesis and chondrogenesis compared to the BM-MSCs, while less adipogenic potential was found in the iPSC-MSCs. The iPSC-MSCs and the tri-lineage differentiated cells (osteoblasts, chondrocytes, adipocytes) all lack expression of “stemness” genes: OCT4, SOX2, GDF3, CRIPTO, UTF1, DPPA4, DNMT3B, LIN28a, and SAL4.

Conclusions

The MSCs derived from human iPSCs with our method have advanced proliferation capability and adequate osteogenic and chondrogenic properties compared to BM-MSCs. However, the iPSC-MSCs were less efficient in their adipogenicity, suggesting that further modifications should be applied to our method to derive iPSC-MSCs more closely resembling the naïve BM-MSCs if necessary.

Molecular characterisation of stromal populations derived from human embryonic stem cells: Similarities to immortalised bone marrow derived stromal stem cells

Human bone marrow-derived stromal (skeletal) stem cells (BM-hMSC) are being employed in an increasing number of clinical trials for tissue regeneration. A limiting factor for their clinical use is the inability to obtain sufficient cell numbers. Human embryonic stem cells (hESC) can provide an unlimited source of clinical grade cells for therapy. We have generated MSC-like cells from hESC (called here hESC-stromal) that exhibit surface markers and differentiate to osteoblasts and adipocytes, similar to BM-hMSC. In the present study, we used microarray analysis to compare the molecular phenotype of hESC-stromal and immortalised BM-hMSC cells (hMSC-TERT). Of the 7379 genes expressed above baseline, only 9.3% of genes were differentially expressed between undifferentiated hESC-stromal and BM-hMSC. Following ex vivo osteoblast induction, 665 and 695 genes exhibited ≥ 2-fold change (FC) in hESC-stromal and BM-hMSC, respectively with 172 genes common to both cell types. Functional annotation of significantly changing genes revealed similarities in gene ontology between the two cell types. Interestingly, genes in categories of cell adhesion/motility and epithelial–mesenchymal transition (EMT) were highly enriched in hESC-stromal whereas genes associated with cell cycle processes were enriched in hMSC-TERT. This data suggests that while hESC-stromal cells exhibit a similar molecular phenotype to hMSC-TERT, differences exist that can be explained by ontological differences between these two cell types. hESC-stromal cells can thus be considered as a possible alternative candidate cells for hMSC, to be employed in regenerative medicine protocols.

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hESC-derived MSC-like cells were compared to immortalised BM-MSC.

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Comparison was performed using microarrays on non-induced and OB induced cells.

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Analysis demonstrated close hierarchical relationships and molecular phenotypes.

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90.7% of genes were similarly expressed in non-induced cells.

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73% of OB induced genes for both cell lines correlated with GO ontology analysis.

Bone tissue engineering via human induced pluripotent, umbilical cord and bone marrow mesenchymal stem cells in rat cranium

Human induced pluripotent stem cells (hiPSCs) are an exciting cell source with great potential for tissue engineering. Human bone marrow mesenchymal stem cells (hBMSCs) have been used in clinics but are limited by several disadvantages, hence alternative sources of MSCs such as umbilical cord MSCs (hUCMSCs) are being investigated. However, there has been no report comparing hiPSCs, hUCMSCs and hBMSCs for bone regeneration. The objectives of this pilot study were to investigate hiPSCs, hUCMSCs and hBMSCs for bone tissue engineering, and compare their bone regeneration via seeding on biofunctionalized macroporous calcium phosphate cement (CPC) in rat cranial defects. For all three types of cells, approximately 90% of the cells remained alive on CPC scaffolds. Osteogenic genes were up-regulated, and mineral synthesis by cells increased with time in vitro for all three types of cells. The new bone area fractions at 12weeks (mean±sd; n=6) were (30.4±5.8)%, (27.4±9.7)% and (22.6±4.7)% in hiPSC-MSC-CPC, hUCMSC-CPC and hBMSC-CPC respectively, compared to (11.0±6.3)% for control (p<0.05). No significant differences were detected among the three types of stem cells (p>0.1). New blood vessel density was higher in cell-seeded groups than control (p<0.05). De novo bone formation and participation by implanted cells was confirmed via immunohistochemical staining. In conclusion, (1) hiPSCs, hUCMSCs and hBMSCs greatly enhanced bone regeneration, more than doubling the new bone amount of cell-free CPC control; (2) hiPSC-MSCs and hUCMSCs represented viable alternatives to hBMSCs; (3) biofunctionalized macroporous CPC-stem cell constructs had a robust capacity for bone regeneration.

Regulation of mesenchymal stromal cells through fine tuning of canonical Wnt signaling

Mesenchymal stromal cells (MSCs) have been extensively utilized for various cell therapeutic trials, but the signals regulating their stromal function remain largely unclear. Here, we show that canonical Wnt signals distinctively regulate MSCs in a biphasic manner depending on signal intensity, i.e., MSCs exhibit proliferation and progenitor self-renewal under low Wnt/β-catenin signaling, whereas they exhibit enhanced osteogenic differentiation with priming to osteoblast-like lineages under high Wnt/β-catenin signaling. Moreover, low or high levels of β-catenin in MSCs distinctly regulated the hematopoietic support of MSCs to promote proliferation or the undifferentiated state of hematopoietic progenitors, respectively. A gene expression study demonstrated that different intracellular levels of β-catenin in MSCs induce distinct transcriptomic changes in subsets of genes belonging to different gene function categories. Different β-catenin levels also induced differences in intracellular levels of the β-catenin co-factors, Tcf-1 and Lef-1. Moreover, nano-scale mass spectrometry of proteins that co-precipitated with β-catenin revealed distinctive spectra of proteins selectively interacting with β-catenin at specific expression levels. Together, these results show that Wnt/β-catenin signals can coax distinct transcription milieu to induce different transcription profiles in MSCs depending on the signal intensity and that fine-tuning of the canonical Wnt signaling intensity can regulate the phase-specific functionality of MSCs.

Dynamic 3D culture: models of chondrogenesis and endochondral ossification

The formation of cartilage from stem cells during development is a complex process which is regulated by both local growth factors and biomechanical cues, and results in the differentiation of chondrocytes into a range of subtypes in specific regions of the tissue. In fetal development cartilage also acts as a precursor scaffold for many bones, and mineralization of this cartilaginous bone precursor occurs through the process of endochondral ossification. In the endochondral formation of bones during fetal development the interplay between cell signalling, growth factors, and biomechanics regulates the formation of load bearing bone, in addition to the joint capsule containing articular cartilage and synovium, generating complex, functional joints from a single precursor anlagen. These joint tissues are subsequently prone to degeneration in adult life and have poor regenerative capabilities, and so understanding how they are created during development may provide useful insights into therapies for diseases, such as osteoarthritis, and restoring bone and cartilage lost in adulthood. Of particular interest is how these tissues regenerate in the mechanically dynamic environment of a living joint, and so experiments performed using 3D models of cartilage development and endochondral ossification are proving insightful. In this review, we discuss some of the interesting models of cartilage development, such as the chick femur which can be observed in ovo, or isolated at a specific developmental stage and cultured organotypically in vitro. Biomaterial and hydrogel-based strategies which have emerged from regenerative medicine are also covered, allowing researchers to make informed choices on the characteristics of the materials used for both original research and clinical translation. In all of these models, we illustrate the essential importance of mechanical forces and mechanotransduction as a regulator of cell behavior and ultimate structural function in cartilage.

A therapy-grade protocol for differentiation of pluripotent stem cells into mesenchymal stem cells using platelet lysate as supplement

Introduction

Mesenchymal stem cells (MSCs) are a promising source of cells for regenerative therapies. Although they can be isolated easily from several tissues, cell expansion is limited since their properties are lost with successive passages. Hence, pluripotent derived MSCs (PD-MSCs) arise as a suitable alternative for MSC production. Nevertheless, at present, PD-MSC derivation protocols are either expensive or not suitable for clinical purposes.

Methods

In this work we present a therapy-grade, inexpensive and simple protocol to derive MSCs from pluripotent stem cells (PSCs) based on the use of platelet lysate (PL) as medium supplement.

Results

We showed that the PD-MSC_PL expressed multiple MSC markers, including CD90, CD73, CD105, CD166, and CD271, among others. These cells also show multilineage differentiation ability and immunomodulatory effects on pre-stimulated lymphocytes. Thorough characterization of these cells showed that a PD-MSC_PL resembles an umbilical cord (UC) MSC and differs from a PSC in surface marker and extracellular matrix proteins and integrin expression. Moreover, the OCT-4 promoter is re-methylated with mesenchymal differentiation comparable with the methylation levels of UC-MSCs and fibroblasts. Lastly, the use of PL-supplemented medium generates significantly more MSCs than the use of fetal bovine serum.

Conclusions

This protocol can be used to generate a large amount of PD-MSCs with low cost and is compatible with clinical therapies.

Electronic supplementary material

The online version of this article (doi:10.1186/scrt540) contains supplementary material, which is available to authorized users.

Olfactomedin 2, a novel regulator for transforming growth factor-β-induced smooth muscle differentiation of human embryonic stem cell-derived mesenchymal cells

Smooth muscle plays important roles in vascular development. Study of smooth muscle differentiation of human embryonic stem cell–derived mesenchymal cells identifies olfactomedin 2 as a novel regulator. Olfactomedin 2 regulates smooth muscle gene transcription by empowering serum response factor binding to the CArG box in smooth muscle gene promoters.

Transforming growth factor-β (TGF-β) plays an important role in smooth muscle (SM) differentiation, but the downstream target genes regulating the differentiation process remain largely unknown. In this study, we identified olfactomedin 2 (Olfm2) as a novel regulator mediating SM differentiation. Olfm2 was induced during TGF-β–induced SM differentiation of human embryonic stem cell–derived mesenchymal cells. Olfm2 knockdown suppressed TGF-β–induced expression of SM markers, including SM α-actin, SM22α, and SM myosin heavy chain, whereas Olfm2 overexpression promoted the SM marker expression. TGF-β induced Olfm2 nuclear accumulation, suggesting that Olfm2 may be involved in transcriptional activation of SM markers. Indeed, Olfm2 regulated SM marker expression and promoter activity in a serum response factor (SRF)/CArG box–dependent manner. Olfm2 physically interacted with SRF without affecting SRF-myocardin interaction. Olfm2-SRF interaction promoted the dissociation of SRF from HERP1, a transcriptional repressor. Olfm2 also inhibited HERP1 expression. Moreover, blockade of Olfm2 expression inhibited TGF-β–induced SRF binding to SM gene promoters in a chromatin setting, whereas overexpression of Olfm2 dose dependently enhanced SRF binding. These results demonstrate that Olfm2 mediates TGF-β–induced SM gene transcription by empowering SRF binding to CArG box in SM gene promoters.

A porous membrane-mediated isolation of mesenchymal stem cells from human embryonic stem cells

Pluripotent human embryonic stem cells (hESCs) acquire mesenchymal characteristics during the epithelial-mesenchymal transition (EMT) process. Here, we report a simple and an efficient isolation method for mesenchymal stem cells (MSCs) from hESCs undergoing EMT using a commercialized porous membrane transwell culture insert. Suspension culture of hESC colonies results in the formation of embryoid bodies, which adhered on the upper compartment of 8 μm porous membrane in the presence of EMG2-MV media. The population migrating through the permeable membrane to the lower compartment not only exhibited EMT markers but also expressed high levels of a panel of typical MSC surface antigen markers, and demonstrated multipotent differentiation capability. In addition, they have a prolonged proliferation capacity without characteristics and chromosomal changes. Furthermore, the isolated MSCs significantly enhanced cardiac functions in a rat model of myocardial infarction (MI) as measured by the left ventricle wall thickness (MI control, 32.9%±3.2% vs. hESCs-MSCs, 38.7%±2.4%), scar length (MI control, 46.1%±2.5% vs. hESCs-MSCs, 41.8%±1.3%), fibrosis area (MI control, 34.3%±1.6% vs. hESCs-MSCs, 28.9%±3.5%), and capillary density. Our findings demonstrate an ease with which hESCs-MSCs can be effectively isolated using the porous membrane, which overcomes the lack of availability of MSCs for therapeutic applications in various diseased animal models.

Human induced pluripotent stem cells: A new source for brown and white adipocytes

Mesenchymal stem cells (MSCs) derived from human induced pluripotent stem cells (hiPSCs) provide a novel source for generating adipocytes, thus opening new avenues for fundamental research and clinical medicine. We present the adipogenic potential of hiPSCs and the various methods to derive hiPSC-MSCs. We discuss the main characteristic of hiPSC-MSCs, which is their low adipogenic capacity as compared to adult-MSCs. Finally, we propose several hypotheses to explanation this feature, underlying a potential critical role of the micro-environment. We favour the hypothesis that the range of factors or culture conditions required to induce adipocyte differentiation of MSCs derived from adult tissues and from embryonic-like cells could differ.

Modulating the biochemical and biophysical culture environment to enhance osteogenic differentiation and maturation of human pluripotent stem cell-derived mesenchymal progenitors

Advances in the fields of stem cell biology, biomaterials, and tissue engineering over the last decades have brought the possibility of constructing tissue substitutes with a broad range of applications in regenerative medicine, disease modeling, and drug discovery. Different types of human stem cells have been used, each presenting a unique set of advantages and limitations with regard to the desired research goals. Whereas adult stem cells are at the frontier of research for tissue and organ regeneration, pluripotent stem cells represent a more challenging cell source for clinical translation. However, with their unlimited growth and wide differentiation potential, pluripotent stem cells represent an unprecedented resource for the construction of advanced human tissue models for biological studies and drug discovery. At the heart of these applications lies the challenge to reproducibly expand, differentiate, and organize stem cells into mature, stable tissue structures. In this review, we focus on the derivation of mesenchymal tissue progenitors from human pluripotent stem cells and the control of their osteogenic differentiation and maturation by modulation of the biophysical culture environment. Similarly to enhancing bone development, the described principles can be applied to the construction of other mesenchymal tissues for basic and applicative studies.