Mechanisms involved in the therapeutic properties of mesenchymal stem cells

Adult stem cell-based apexogenesis

Generally, the dental pulp needs to be removed when it is infected, and root canal therapy (RCT) is usually required in which infected dental pulp is replaced with inorganic materials (paste and gutta percha). This treatment approach ultimately brings about a dead tooth. However, pulp vitality is extremely important to the tooth itself, since it provides nutrition and acts as a biosensor to detect the potential pathogenic stimuli. Despite the reported clinical success rate, RCT-treated teeth are destined to be devitalized, brittle and susceptible to postoperative fracture. Recently, the advances and achievements in the field of stem cell biology and regenerative medicine have inspired novel biological approaches to apexogenesis in young patients suffering from pulpitis or periapical periodontitis. This review mainly focuses on the benchtop and clinical regeneration of root apex mediated by adult stem cells. Moreover, current strategies for infected pulp therapy are also discussed here.

Regulatory T cells enhance mesenchymal stem cell survival and proliferation following autologous cotransplantation in ischemic myocardium

OBJECTIVES

We sought to investigate if autologous freshly isolated regulatory T cells (Tregs) provide a protective and supportive role when cotransplanted with mesenchymal stem cells (MSCs).

METHODS

In a porcine model of chronic ischemia, autologous MSCs were isolated and expanded ex vivo for 4 weeks. Autologous Treg cells were freshly isolated from 100 mL peripheral blood and purified by fluorescence-activated cell sorting. MSCs and Treg cells were then cotransplanted into the chronic ischemic myocardium of Yorkshire pigs by direct intramyocardial injection (1.2 × 10(8) MSCs plus an average of 1.5 million Treg cells in 25 injection sites). Animals were killed 6 weeks postinjection to study the fate of the cells and compare the effect of combined MSCs + Treg cells transplantation versus MSCs alone.

RESULTS

The coinjection of MSCs along with Tregs was safe and no deleterious side effects were observed. Six weeks after injection of the cell combination, spherical MSCs clusters with thin layer capsules were found in the injected areas. In animals treated with MSCs only, the MSC clusters were less organized and not encapsulated. Immunofluorescent staining showed CD25+ cells among the CD90+ (MSC marker) cells, suggesting that the injected Treg cells remained present locally, and survived. Factor VIII+ cells were also prevalent suggesting new angiogenesis. We found no evidence that coinjections were associated with the generation of cardiac myocytes.

CONCLUSIONS

The cotransplantation of Treg cells with MSCs dramatically increased the MSC survival rate, proliferation, and augmented their role in angiogenesis, which suggests a new way for future clinical application of cell-based therapy.

Bone marrow-derived mesenchymal stromal cells improve vascular regeneration and reduce leukocyte-endothelium activation in critical ischemic murine skin in a dose-dependent manner

BACKGROUND AIMS

Stem cells participate in vascular regeneration following critical ischemia. However, their angiogenic and remodeling properties, as well as their role in ischemia-related endothelial leukocyte activation, need to be further elucidated. Herein, we investigated the effect of bone marrow-derived mesenchymal stromal cells (BM-MSCs) in a critically ischemic murine skin flap model.

METHODS

Groups received either 1 × 10(5), 5 × 10(5), or 1 × 10(6) BM-MSCs or cell-free conditioned medium (CM). Controls received sodium chloride. Intravital fluorescence microscopy was performed for morphological and quantitative assessment of micro-hemodynamic parameters over 12 days.

RESULTS

Tortuosity and diameter of conduit-arterioles were pronounced in the MSC groups (P < 0.01), whereas vasodilation was shifted to the end arteriolar level in the CM group (P < 0.01). These effects were accompanied by angiopoietin-2 expression. Functional capillary density and red blood cell velocity were enhanced in all treatment groups (P < 0.01). Although a significant reduction of rolling and sticking leukocytes was observed in the MSC groups with a reduction of diameter in postcapillary venules (P < 0.01), animals receiving CM exhibited a leukocyte-endothelium interaction similar to controls. This correlated with leukocyte common antigen expression in tissue sections (P < 0.01) and p38 mitogen-activated protein kinase expression from tissue samples. Cytokine analysis from BM-MSC culture medium revealed a 50% reduction of pro-inflammatory cytokines (interleukin [IL]-1β, IL-6, IL-12, tumor necrosis factor-α, interferon-γ) and chemokines (keratinocyte chemoattractant, granulocyte colony-stimulating factor) under hypoxic conditions.

DISCUSSION

We demonstrated positive effects of BM-MSCs on vascular regeneration and modulation of endothelial leukocyte adhesion in critical ischemic skin. The improvements after MSC application were dose-dependent and superior to the use of CM alone.

Transplantation of SIRT1-engineered aged mesenchymal stem cells improves cardiac function in a rat myocardial infarction model

BACKGROUND

Previous studies have demonstrated that biological aging has a negative influence on the therapeutic effects of mesenchymal stem cells (MSCs)-based therapy. Using a rat myocardial infarction (MI) model, we tested the hypothesis that silent mating type information regulation 2 homolog 1 (SIRT1) may ameliorate the phenotype and improve the function of aged MSCs and thus enhance the efficacy of aged MSCs-based therapy.

METHODS

Sixty female rats underwent left anterior descending coronary artery ligation and were randomly assigned to receiving: intramyocardial injection of cell culture medium (DMEM group); SIRT1 overexpression vector-treated aged MSCs (SIRT1-aged MSCs group) obtained from aged male SD rats or empty vector-treated aged MSCs (vector-aged MSCs group). Another 20 sham-operated rats that underwent open-chest surgery without coronary ligation or any other intervention served as controls.

RESULTS

SIRT1-aged MSC group exhibited enhanced blood vessel density in the border zone of MI hearts, which was associated with reduced cardiac remodeling, leading to improved cardiac performance. Consistent with the in vivo data, our in vitro experiments also demonstrated that SIRT1 overexpression ameliorated aged MSCs senescent phenotype and recapitulated the pro-angiogenesis property of MSCs and conferred the anti-stress response capabilities, as indicated by increases in pro-angiogenic factors, angiopoietin 1 (Ang1) and basic fibroblast growth factor (bFGF), expressions and a decrease in anti-angiogenic factor thrombospondin-1 (TBS1) at mRNA levels, and increases in Bcl-2/Bax ratio at protein level.

CONCLUSIONS

Up-regulating SIRT1 expression could enhance the efficacy of aged MSCs-based therapy for MI as it relates to the amelioration of senescent phenotype and hence improved biological function of aged MSCs.

Mesenchymal stem cell therapy for cardiac repair

OPINION STATEMENT

Owing to the prevalence of heart disease and the lack of effective long-term solutions for managing cardiac injury, research has turned to cell therapy as a potential mechanism for myocardial repair. Mesenchymal stem cells (MSC) in particular have become popular because their differentiative ability and their angiogenic and immunomodulatory properties make them attractive candidates for transplantation. However, there is still debate regarding the optimal strategy for the delivery of these cells. Recent clinical studies have isolated MSCs from a variety of tissue origins and have also tested the benefits of pretreatment with cardiogenic growth factors. Meanwhile, a newer school of thought instead supports the utilization of cardiomyocytes generated from MSC-derived induced pluripotent stem cells. This review will examine the promise of MSC therapy, discuss the results of past work, and propose steps that must be taken in the future.

Transplantation of bone marrow mesenchymal stem cells on collagen scaffolds for the functional regeneration of injured rat uterus

Serious injuries of endometrium in women of reproductive age are often followed by uterine scar formation and a lack of functional endometrium predisposing to infertility or miscarriage. Bone marrow-derived mesenchymal stem cells (BM-MSCs) have shown great promise in clinical applications. In the present study, BM-MSCs loaded onto degradable collagen membranes were constructed. Collagen membranes provided 3-dimmensional architecture for the attachment, growth and migration of rat BM-MSCs and did not impair the expression of the stemness genes. We then investigated the effect of collagen/BM-MSCs constructs in the healing of severe uterine injury in rats (partial full thickness uterine excision). At four weeks after the transplantation of collagen/BM-MSCs constructs, BM-MSCs were mainly located to the basal membrane of regenerative endometrium. The wounded tissue adjacent to collagen/BM-MSCs constructs expressed higher level of bFGF, IGF-1, TGFβ1 and VEGF than the corresponding tissue in rats receiving collagen construct alone or in spontaneous regeneration group. Moreover, the collagen/BM-MSCs system increased proliferative abilities of uterine endometrial and muscular cells, facilitated microvasculature regeneration, and restored the ability of endometrium to receive the embryo and support its development to a viable stage. Our findings indicate that BM-MSCs may support uterine tissue regeneration.

Consequences of irradiation on bone and marrow phenotypes, and its relation to disruption of hematopoietic precursors

The rising levels of radiation exposure, specifically for medical treatments and accidental exposures, have added great concern for the long term risks of bone fractures. Both the bone marrow and bone architecture are devastated following radiation exposure. Even sub-lethal doses cause a deficit to the bone marrow microenvironment, including a decline in hematopoietic cells, and this deficit occurs in a dose dependent fashion. Certain cell phenotypes though are more susceptible to radiation damage, with mesenchymal stem cells being more resilient than the hematopoietic stem cells. The decline in total bone marrow hematopoietic cells is accompanied with elevated adipocytes into the marrow cavity, thereby inhibiting hematopoiesis and recovery of the bone marrow microenvironment. Poor bone marrow is also associated with a decline in bone architectural quality. Therefore, the ability to maintain the bone marrow microenvironment would hinder much of the trabecular bone loss caused by radiation exposure, ultimately decreasing some comorbidities in patients exposed to radiation.

Urine-derived stem cells for potential use in bladder repair

Engineered bladder tissues, created with autologous bladder cells seeded on biodegradable scaffolds, are being developed for use in patients who need cystoplasty. However, in individuals with organ damage from congenital disorders, infection, irradiation, or cancer, abnormal cells obtained by biopsy from the compromised tissue could potentially contaminate the engineered tissue. Thus, an alternative cell source for construction of the neo-organ would be useful. Although other types of stem cells have been investigated, autologous mesenchymal stem cells (MSCs) are most suitable to use in bladder regeneration. These cells are often used as a cell source for bladder repair in three ways - secreting paracrine factors, recruiting resident cells, and trans-differentiation, inducing MSCs to differentiate into bladder smooth muscle cells and urothelial cells. Adult stem cell populations have been demonstrated in bone marrow, fat, muscle, hair follicles, and amniotic fluid. These cells remain an area of intense study, as their potential for therapy may be applicable to bladder disorders. Recently, we have found stem cells in the urine and the cells are highly expandable, and have self-renewal capacity and paracrine properties. As a novel cell source, urine-derived stem cells (USCs) provide advantages for cell therapy and tissue engineering applications in bladder tissue repair because they originate from the urinary tract system. Importantly, USCs can be obtained via a noninvasive, simple, and low-cost approach and induced with high efficiency to differentiate into bladder cells.

The potential of mesenchymal stem cell in prion research

Scrapie and bovine spongiform encephalopathy are fatal neurodegenerative diseases caused by the accumulation of a misfolded protein (PrP(res)), the pathological form of the cellular prion protein (PrP(C)). For the last decades, prion research has greatly progressed, but many questions need to be solved about prion replication mechanisms, cell toxicity, differences in genetic susceptibility, species barrier or the nature of prion strains. These studies can be developed in murine models of transmissible spongiform encephalopathies, although development of cell models for prion replication and sample titration could reduce economic and timing costs and also serve for basic research and treatment testing. Some murine cell lines can replicate scrapie strains previously adapted in mice and very few show the toxic effects of prion accumulation. Brain cell primary cultures can be more accurate models but are difficult to develop in naturally susceptible species like humans or domestic ruminants. Stem cells can be differentiated into neuron-like cells and be infected by prions. However, the use of embryo stem cells causes ethical problems in humans. Mesenchymal stem cells (MSCs) can be isolated from many adult tissues, including bone marrow, adipose tissue or even peripheral blood. These cells differentiate into neuronal cells, express PrP(C) and can be infected by prions in vitro. In addition, in the last years, these cells are being used to develop therapies for many diseases, including neurodegenerative diseases. We review here the use of cell models in prion research with a special interest in the potential use of MSCs.

Mechanisms of kidney repair by human mesenchymal stromal cells after ischemia: a comprehensive view using label-free MS(E)

Acute kidney injury (AKI) is one of the more frequent and lethal pathological conditions seen in intensive care units. Currently available treatments are not totally effective but stem cell-based therapies are emerging as promising alternatives, especially the use of mesenchymal stromal cells (MSC), although the signaling pathways involved in their beneficial actions are not fully understood. The objective of this study was to identify signaling networks and key proteins involved in the repair of ischemia by MSC. Using an in vitro model of AKI to investigate paracrine interactions and label-free high definition 2D-NanoESI-MS(E) , differentially expressed proteins were identified in a human renal proximal tubule cell lineage (HK-2) exposed to human MSC (hMSC) after an ischemic insult. In silico analysis showed that hMSC stimulated antiapoptotic activity, normal ROS handling, energy production, cytoskeleton organization, protein synthesis, and cell proliferation. The proteomic data were validated by parallel experiments demonstrating reduced apoptosis in HK-2 cells and recovery of intracellular ATP levels. qRT-PCR for proteins implicated in the above processes revealed that hMSC exerted their effects by stimulating translation, not transcription. Western blotting of proteins associated with ROS and energy metabolism confirmed their higher abundance in HK-2 cells exposed to hMSC.

Mesenchymal stem cell therapy induces glucocorticoid synthesis in colonic mucosa and suppresses radiation-activated T cells: new insights into MSC immunomodulation

Non-neoplastic tissues around an abdomino-pelvic tumor can be damaged by the radiotherapy protocol, leading to chronic gastrointestinal complications that affect the quality of life with substantial mortality. Stem cell-based approaches using immunosuppressive bone marrow mesenchymal stem cells (MSCs) are promising cell therapy tools. In a rat model of radiation proctitis, we evidenced that a single MSC injection reduces colonic mucosa damages induced by ionizing radiation with improvement of the re-epithelization process for up to 21 days. Immune cell infiltrate and inflammatory molecule expressions in the colonic mucosa were investigated. We report that MSC therapy specifically reduces T-cell infiltration and proliferation, and increases apoptosis of radiation-activated T cells. We assessed the underlying molecular mechanisms and found that interleukin-10 and regulatory T lymphocytes are not involved in the immunosuppressive process in this model. However, an increased level of corticosterone secretion and HSD11b1 (11β-hydroxysteroid dehydrogenase type 1)-steroidogenic enzyme expression was detected in colonic mucosa 21 days after MSC treatment. Moreover, blocking the glucocorticoid (GC) receptor using the RU486 molecule statistically enhances the allogenic lymphocyte proliferation inhibited by MSCs in vitro and abrogates the mucosal protection induced by MSC treatment in vivo. Using the irradiation model, we found evidence for a new MSC immunosuppressive mechanism involving GCs.

Mesenchymal stem cells in treating autism: Novel insights

Autism spectrum disorders (ASDs) are complex neurodevelopmental disorders characterized by dysfunctions in social interactions, abnormal to absent verbal communication, restricted interests, and repetitive stereotypic verbal and non-verbal behaviors, influencing the ability to relate to and communicate. The core symptoms of ASDs concern the cognitive, emotional, and neurobehavioural domains. The prevalence of autism appears to be increasing at an alarming rate, yet there is a lack of effective and definitive pharmacological options. This has created an increased sense of urgency, and the need to identify novel therapies. Given the growing awareness of immune dysregulation in a significant portion of the autistic population, cell therapies have been proposed and applied to ASDs. In particular, mesenchymal stem cells (MSCs) possess the immunological properties which make them promising candidates in regenerative medicine. MSC therapy may be applicable to several diseases associated with inflammation and tissue damage, where subsequent regeneration and repair is necessary. MSCs could exert a positive effect in ASDs through the following mechanisms: stimulation of repair in the damaged tissue, e.g., inflammatory bowel disease; synthesizing and releasing anti-inflammatory cytokines and survival-promoting growth factors; integrating into existing neural and synaptic network, and restoring plasticity. The paracrine mechanisms of MSCs show interesting potential in ASD treatment. Promising and impressive results have been reported from the few clinical studies published to date, although the exact mechanisms of action of MSCs in ASDs to restore functions are still largely unknown. The potential role of MSCs in mediating ASD recovery is discussed in light of the newest findings from recent clinical studies.

Conditioned medium derived from mesenchymal stem cells culture as a intravesical therapy for cystitis interstitials

The treatment of Interstinal Cystitisis (IC) is still challenge for urologist. Available therapies do not result in long-term control of symptoms and do not provide pain relive to patients. Unique abilities of mesenchymal stem cells (MSC) could be used to develop new treatment approaches for Interstitial Cystitis. Conditioned Medium (CM) derived from MSC culture is rich in plenty of growth factors, cytokines and trophic agents which were widely reported to enhance regeneration of urinary bladder in different conditions. This ready mixture of growth factors could be used to develop intravesical therapy for patients with IC. MSC-CM has anti-apoptotic, anti-inflammatory, supportive, angiogenic, immunosuppressive and immunomodulative properties and seems to be ideal substance to prevent IC recurrence and to create favorable environment for regeneration of damaged bladder wall.

Mesenchymal stem/stromal cells as a pharmacological and therapeutic approach to accelerate angiogenesis

Mesenchymal stem cells or multipotent stromal cells (MSCs) have initially captured attention in the scientific world because of their differentiation potential into osteoblasts, chondroblasts and adipocytes and possible transdifferentiation into neurons, glial cells and endothelial cells. This broad plasticity was originally hypothesized as the key mechanism of their demonstrated efficacy in numerous animal models of disease as well as in clinical settings. However, there is accumulating evidence suggesting that the beneficial effects of MSCs are predominantly caused by the multitude of bioactive molecules secreted by these remarkable cells. Numerous angiogenic factors, growth factors and cytokines have been discovered in the MSC secretome, all have been demonstrated to alter endothelial cell behavior in vitro and induce angiogenesis in vivo. As a consequence, MSCs have been widely explored as a promising treatment strategy in disorders caused by insufficient angiogenesis such as chronic wounds, stroke and myocardial infarction. In this review, we will summarize into detail the angiogenic factors found in the MSC secretome and their therapeutic mode of action in pathologies caused by limited blood vessel formation. Also the application of MSC as a vehicle to deliver drugs and/or genes in (anti-)angiogenesis will be discussed. Furthermore, the literature describing MSC transdifferentiation into endothelial cells will be evaluated critically.

Effects of long-term hypoxia and pro-survival cocktail in bone marrow-derived stromal cell survival

The goal of this study was to determine whether a pro-survival cocktail (PSC, consisting of IGF-1, Bcl-XL, and Caspase-I Inhibitor) and long-term hypoxia (LTH) enhance survival and functional properties of bone marrow-derived stromal stem cells (BMSCs), in response to stress conditions. PSC-treated cells retained BMSC surface markers and protected cells from apoptosis under serum starvation and ischemic (1% O2 and 100 μM H2O2) conditions. LTH promoted osteogenesis, while suppressing adipogenesis. LTH alone did not result in an improvement in the apoptosis rate; however, PSC conferred significant protection regardless of the oxygenation status. One of the possible mechanisms of PSC protection was due to the elevated phospho-AKT in treated groups. PSC treatment or LTH did not alter migration toward stem cell-derived factor-1 alpha (SDF-1α) or fetal bovine serum, nor did they enhance cell motility during wound healing. There was no difference in the secreted cytokine profiles of BMSCs treated with PSC after stress when grown in normoxic or LTH. However, LTH did upregulate the vascular endothelial growth factor, hepatocyte growth factor, and SDF-1α, while it downregulated other anti- and proinflammatory cytokines and chemokines. We also observed a high degree of interdonor BMSC variability in response to pretreatment with PSC and LTH, confounding the functional results, underscoring the observation that not all donor-derived BMSCs will respond similarly.

Use of mesenchymal stem cells or autologous conditioned serum to modulate the inflammatory response to spermatozoa in mares

Current treatments for Persistent mating-induced endometritis such as uterine lavage and oxytocin therapy focus on aiding the uterus in removal of inflammatory products, but these treatments do not modulate the inciting inflammatory response. Biological treatments, such as autologous conditioned serum (ACS) and mesenchymal stem cells (MSCs), have been used in human and veterinary medicine for immunomodulation for over 10 years. The objectives of this project were to evaluate the ability of ACS or MSCs to modulate the inflammatory response to spermatozoa after breeding. Two experiments were performed with six normal mares in each study to evaluate the effects of intrauterine administration of ACS, dexamethasone, or a placebo (experiment 1), or allogeneic MSCs or a placebo (experiment 2) on the inflammatory response to spermatozoa using clinical and biochemical endpoints. Treatment with ACS and MSCs significantly (P < 0.05) reduced the number of neutrophils in the uterine lumen 6 hours after the sperm challenge. An increase (P < 0.05) in the anti-inflammatory cytokine IL-1Ra was observed after treatment with MSCs before exposure to spermatozoa. There was no difference in IL-1Ra concentration in mares treated with ACS, dexamethasone, or a placebo. Mesenchymal stem cells and ACS were able to modulate the immune response to spermatozoa in normal mares. The effect may be due to an increase in IL-1Ra in MSCs-treated mares, but other bioactive molecules may be responsible for the decrease in neutrophils in ACS-treated mares. Autologous conditioned serum and bone-derived culture expanded MSCs were able to modulate the uterine inflammatory response to spermatozoa in normal mares. Treatment with allogeneic stem cells may be beneficial if a similar modulation in inflammatory cytokines occurs in mares affected by persistent mating-induced endometritis.

Mouse bone marrow-derived mesenchymal stem cells induce macrophage M2 polarization through the nuclear factor-κB and signal transducer and activator of transcription 3 pathways

Increasing evidence has demonstrated that mesenchymal stem cells (MSCs)-mediated regulation of macrophages is critical for inflammation response and tissue injury repair. However, the underlying mechanism is not well understood. In this study, we investigated the effect of mouse bone marrow-derived MSCs on macrophages under normal and inflammatory conditions. Co-culture with MSCs or treatment with MSC-conditioned medium (MSC-CM) reduced the expression of tumor necrosis factor-α while inducing the expression of interleukin 10 (IL-10) and arginase 1 in lipopolysaccharide (LPS)-stimulated mouse RAW264.7 cells and splenic CD11b(+) cells. MSC-CM treatment increased the expression of CD206, a marker of alternatively activated M2 macrophages, in RAW264.7 cells. In addition, MSC-CM promoted the proliferation and migration of RAW264.7 cells. MSC-CM treatment activated signal transducer and activator of transcription 3 (STAT3) but inhibited nuclear factor-κB (NF-κB) pathways in LPS-stimulated RAW264.7 cells. Moreover, STAT3 inhibitor S3I-201 antagonized the induction of IL-10, arginase 1, and CD206 by MSC-CM in RAW264.7 cells. Conclusively, our findings suggest that mouse MSCs induce macrophage M2 activation through the NF-κB and STAT3 pathways.

Transplantation of mesenchymal stem cells carrying the human receptor activity-modifying protein 1 gene improves cardiac function and inhibits neointimal proliferation in the carotid angioplasty and myocardial infarction rabbit model

Although transplanting mesenchymal stem cells (MSCs) can improve cardiac function and contribute to endothelial recovery in a damaged artery, natural MSCs may induce neointimal hyperplasia by directly or indirectly acting on vascular smooth muscle cells (VSMCs). Receptor activity-modifying protein 1 (RAMP1) is the component and the determinant of ligand specificity of calcitonin gene-related peptide (CGRP). It is recently reported that CGRP and its receptor involve the proliferation and the apoptosis in vivo and in vitro, and the exogenous RAMP1 enhances the antiproliferation effect of CGRP in VSMCs. Here, we investigated the effects of MSCs overexpressing the human receptor activity-modifying protein 1 (hRAMP1) on heart function and artery repair in rabbit models of myocardial infarction (MI) reperfusion and carotid artery injury. MSCs transfected with a recombinant adenovirus containing the hRAMP1 gene (EGFP-hRAMP1-MSCs) were injected into the rabbit models via the ear vein at 24 h after carotid artery injury and MI 7 days post-EGFP-hRAMP1-MSC transplantation. The cells that expressed both enhance green fluorescent protein (EGFP) and CD31 were detected in the neointima of the damaged artery via immunofluorescence. EGFP-hRAMP1 expression was observed in the injured artery and infarcted myocardium by western blot analysis, confirming that the engineered MSCs targeted the injured artery and infarcted myocardium and expressed hRAMP1 protein. Compared with the EGFP-MSCs group, the EGFP-hRAMP1-MSCs group had a significantly smaller infarcted area and improved cardiac function by 28 days after cell transplantation, as detected by triphenyltetrazolium chloride staining and echocardiography. Additionally, arterial hematoxylin-eosin staining revealed that the area of the neointima and the area ratio of intima/media were significantly decreased in the EGFP-hRAMP1-MSCs group. An immunohistological study showed that the expression of α-smooth muscle antigen and proliferating cell nuclear antigen in the neointima cells of the carotid artery of the EGFP-hRAMP1-MSCs group was approximately 50% lower than that of the EGFP-MSCs group, suggesting that hRAMP1 expression may inhibit VSMCs proliferation within the neointima. Therefore, compared with natural MSCs, EGFP-hRAMP1-engineered MSCs improved infarcted heart function and endothelial recovery from artery injury more efficiently, which will provide valuable information for the development of MSC-based therapy.

Exercise is the real polypill

The concept of a "polypill" is receiving growing attention to prevent cardiovascular disease. Yet similar if not overall higher benefits are achievable with regular exercise, a drug-free intervention for which our genome has been haped over evolution. Compared with drugs, exercise is available at low cost and relatively free of adverse effects. We summarize epidemiological evidence on the preventive/therapeutic benefits of exercise and on the main biological mediators involved.

Towards an advanced therapy medicinal product based on mesenchymal stromal cells isolated from the umbilical cord tissue: quality and safety data

Introduction

Standardization of mesenchymal stromal cells (MSCs) manufacturing is urgently needed to enable translational activities and ultimately facilitate comparison of clinical trial results. In this work we describe the adaptation of a proprietary method for isolation of a specific umbilical cord tissue-derived population of MSCs, herein designated by its registered trademark as UCX®, towards the production of an advanced therapy medicinal product (ATMP).

Methods

The adaptation focused on different stages of production, from cell isolation steps to cell culturing and cryopreservation. The origin and quality of materials and reagents were considered and steps for avoiding microbiological and endotoxin contamination of the final cell product were implemented. Cell isolation efficiency, MSCs surface markers and genetic profiles, originating from the use of different medium supplements, were compared. The ATMP-compliant UCX® product was also cryopreserved avoiding the use of dimethyl sulfoxide, an added benefit for the use of these cells as an ATMP. Cells were analyzed for expansion capacity and longevity. The final cell product was further characterized by flow cytometry, differentiation potential, and tested for contaminants at various passages. Finally, genetic stability and immune properties were also analyzed.

Results

The isolation efficiency of UCX® was not affected by the introduction of clinical grade enzymes. Furthermore, isolation efficiencies and phenotype analyses revealed advantages in the use of human serum in cell culture as opposed to human platelet lysate. Initial decontamination of the tissue followed by the use of mycoplasma- and endotoxin-free materials and reagents in cell isolation and subsequent culture, enabled the removal of antibiotics during cell expansion. UCX®-ATMP maintained a significant expansion potential of 2.5 population doublings per week up to passage 15 (P15). They were also efficiently cryopreserved in a DMSO-free cryoprotectant medium with approximately 100% recovery and 98% viability post-thaw. Additionally, UCX®-ATMP were genetically stable upon expansion (up to P15) and maintained their immunomodulatory properties.

Conclusions

We have successfully adapted a method to consistently isolate, expand and cryopreserve a well-characterized population of human umbilical cord tissue-derived MSCs (UCX®), in order to obtain a cell product that is compliant with cell therapy. Here, we present quality and safety data that support the use of the UCX® as an ATMP, according to existing international guidelines.

The morphology, proliferation rate, and population doubling time factor of adipose-derived mesenchymal stem cells cultured on to non-aqueous SiO2, TiO2, and hybrid sol-gel-derived oxide coatings

In recent years, much attention has been paid to the development of tissue engineering and regenerative medicine, especially when stem cells of various sources are concerned. In addition to the interest in mesenchymal stem cells isolated from bone marrow, recently more consideration has been given to stem cells isolated from adipose tissue (AdMSCs), due to their less invasive method of collection as well as their ease of isolation and culture. However, the development of regenerative medicine requires both the application of biocompatible material and the stem cells to accelerate the regeneration. In this study, we investigated the morphology, proliferation rate index (PRi), and population doubling time factor of adipose-derived mesenchymal stem cells cultured on non-aqueous sol-gel-derived SiO2, TiO2, and SiO2/TiO2 oxide coatings. The results indicated an increase in PRi of AdMSCs when cultured on to titanium dioxide, suggesting its high attractiveness for AdMSCs. In addition, the proper morphology and the shortest doubling time of AdMSCs were observed when cultured on titanium dioxide coating.

Gene expression profiles of human adipose tissue-derived mesenchymal stem cells are modified by cell culture density

Previous studies conducted cell expansion ex vivo using low initial plating densities for optimal expansion and subsequent differentiation of mesenchymal stem cells (MSCs). However, MSC populations are heterogeneous and culture conditions can affect the characteristics of MSCs. In this study, differences in gene expression profiles of adipose tissue (AT)-derived MSCs were examined after harvesting cells cultured at different densities. AT-MSCs from three different donors were plated at a density of 200 or 5,000 cells/cm². After 7 days in culture, detailed gene expression profiles were investigated using a DNA chip microarray, and subsequently validated using a reverse transcription polymerase chain reaction (RT-PCR) analysis. Gene expression profiles were influenced primarily by the level of cell confluence at harvest. In MSCs harvested at ∼90% confluence, 177 genes were up-regulated and 102 genes down-regulated relative to cells harvested at ∼50% confluence (P<0.05, FC>2). Proliferation-related genes were highly expressed in MSCs harvested at low density, while genes that were highly expressed in MSCs harvested at high density (∼90% confluent) were linked to immunity and defense, cell communication, signal transduction and cell motility. Several cytokine, chemokine and growth factor genes involved in immunosuppression, migration, and reconstitution of damaged tissues were up-regulated in MSCs harvested at high density compared with MSCs harvested at low density. These results imply that cell density at harvest is a critical factor for modulating the specific gene-expression patterns of heterogeneous MSCs.

Potential regenerative treatment strategies for intervertebral disc degeneration in dogs

Pain due to spontaneous intervertebral disc (IVD) disease is common in dogs. In chondrodystrophic (CD) dogs, IVD disease typically develops in the cervical or thoracolumbar spine at about 3–7 years of age, whereas in non-chondrodystrophic (NCD) dogs, it usually develops in the caudal cervical or lumbosacral spine at about 6–8 years of age. IVD degeneration is characterized by changes in the biochemical composition and mechanical integrity of the IVD. In the degenerated IVD, the content of glycosaminoglycan (GAG, a proteoglycan side chain) decreases and that of denatured collagen increases. Dehydration leads to tearing of the annulus fibrosus (AF) and/or disc herniation, which is clinically characterized by pain and/or neurological signs. Current treatments (physiotherapy, anti-inflammatory/analgesic medication, surgery) for IVD disease may resolve neurological deficits and reduce pain (although in many cases insufficient), but do not lead to repair of the degenerated disc. For this reason, there is interest in new regenerative therapies that can repair the degenerated disc matrix, resulting in restoration of the biomechanical function of the IVD. CD dogs are considered a suitable animal model for human IVD degeneration because of their spontaneous IVD degeneration, and therefore studies investigating cell-, growth factor-, and/or gene therapy-based regenerative therapies with this model provide information relevant to both human and canine patients. The aim of this article is to review potential regenerative treatment strategies for canine IVD degeneration, with specific emphasis on cell-based strategies.

Mechanisms of T-cell immunosuppression by mesenchymal stromal cells: what do we know so far?

Mesenchymal stromal cells (MSCs) are multipotent cells, which can give rise to several cell types including osteoblasts, adipocytes, and chondroblasts. These cells can be found in a variety of adult and fetal tissues, such as bone marrow, adipose tissue, cord blood, and placenta. In recent years, the biological properties of MSCs have attracted the attention of researchers worldwide due to their potential application for treating a series of clinical situations. Among these properties, special attention should be given to the immunoregulatory potential of those cells. MSCs are able to act on all cells of the immune system, which includes the capacity to inhibit the proliferation and function of T-cells. This feature renders them natural candidates to treat several diseases in which cellular immune response is exacerbated. In this review, we outline the main mechanisms by which MSCs immunosuppress T-cell response, focusing on cell-cell contact, secretion of soluble factors, and regulatory T-cell generation. The influence of surface markers in the immunosuppression process and features of MSCs isolated from different sources are also discussed. Finally, the influences of toll-like receptors and cytokines on the inflammatory microenvironment are highlighted regarding the activation of MSCs to exert their immunoregulatory function.

The Human Umbilical Cord Tissue-Derived MSC Population UCX(®) Promotes Early Motogenic Effects on Keratinocytes and Fibroblasts and G-CSF-Mediated Mobilization of BM-MSCs When Transplanted In Vivo

Mesenchymal stromal cells (MSCs) play an important role in tissue regeneration mainly through the secretion of trophic factors that enhance the repair of damaged tissues. The main goal of this work was to study the paracrine mechanisms by which an umbilical cord tissue-derived MSC population (UCX(®)) promotes the migration capacity of human dermal fibroblasts and keratinocytes, which is highly relevant for skin regeneration. Furthermore, the differences between paracrine activities of MSCs from the umbilical cord tissue and the bone marrow (BM-MSCs) were also evaluated. In vitro scratch assays revealed that conditioned media (CM) obtained from both growing and stationary-phase UCX(®) cultures induced human dermal fibroblast (HDF) and keratinocyte (HaCaT) migration. These assays showed that the motogenic activity of UCX(®) CM to HaCaTs was significantly higher than to HDFs, in opposition to the effect seen with CM produced by BM-MSCs that preferentially induced HDF migration. Accordingly, a comparative quantification of key factors with vital importance in the consecutive stages of wound healing revealed very different secretome profiles between UCX(®) and BM-MSCs. The relatively higher UCX(®) expression of EGF, FGF-2, and KGF strongly supports early induction of keratinocyte migration and function, whereas the UCX(®)-specific expression of G-CSF suggested additional roles in mobilization of healing-related cells including CD34(-)/CD45(-) precursors (MSCs) known to be involved in tissue regeneration. Accordingly, in vitro chemotaxis assays and an in vivo transplantation model for chemoattraction confirmed that UCX(®) are chemotactic to CD34(-)/CD45(-) BM-MSCs via a cell-specific mobilization mechanism mediated by G-CSF. Overall, the results strongly suggest different paracrine activities between MSCs derived from different tissue sources, revealing the potential of UCX(®) to extend the regenerative capacity of the organism by complementing the role of endogenous BM-MSCs.

Fibroblasts derived from human pluripotent stem cells activate angiogenic responses in vitro and in vivo

Human embryonic and induced pluripotent stem cells (hESC/hiPSC) are promising cell sources for the derivation of large numbers of specific cell types for tissue engineering and cell therapy applications. We have describe a directed differentiation protocol that generates fibroblasts from both hESC and hiPSC (EDK/iPDK) that support the repair and regeneration of epithelial tissue in engineered, 3D skin equivalents. In the current study, we analyzed the secretory profiles of EDK and iPDK cells to investigate the production of factors that activate and promote angiogenesis. Analysis of in vitro secretion profiles from EDK and iPDK cells demonstrated the elevated secretion of pro-angiogenic soluble mediators, including VEGF, HGF, IL-8, PDGF-AA, and Ang-1, that stimulated endothelial cell sprouting in a 3D model of angiogenesis in vitro. Phenotypic analysis of EDK and iPDK cells during the course of differentiation from hESCs and iPSCs revealed that both cell types progressively acquired pericyte lineage markers NG2, PDGFRβ, CD105, and CD73 and demonstrated transient induction of pericyte progenitor markers CD31, CD34, and Flk1/VEGFR2. Furthermore, when co-cultured with endothelial cells in 3D fibrin-based constructs, EDK and iPDK cells promoted self-assembly of vascular networks and vascular basement membrane deposition. Finally, transplantation of EDK cells into mice with hindlimb ischemia significantly reduced tissue necrosis and improved blood perfusion, demonstrating the potential of these cells to stimulate angiogenic responses in vivo. These findings demonstrate that stable populations of pericyte-like angiogenic cells can be generated with high efficiency from hESC and hiPSC using a directed differentiation approach. This provides new cell sources and opportunities for vascular tissue engineering and for the development of novel strategies in regenerative medicine.

Mesenchymal stem cells in immune-mediated bone marrow failure syndromes

Immune-mediated bone marrow failure syndromes (BMFS) are characterized by ineffective marrow haemopoiesis and subsequent peripheral cytopenias. Ineffective haemopoiesis is the result of a complex marrow deregulation including genetic, epigenetic, and immune-mediated alterations in haemopoietic stem/progenitor cells, as well as abnormal haemopoietic-to-stromal cell interactions, with abnormal release of haemopoietic growth factors, chemokines, and inhibitors. Mesenchymal stem/stromal cells (MSCs) and their progeny (i.e., osteoblasts, adipocytes, and reticular cells) are considered as key cellular components of the bone marrow haemopoietic niche. MSCs may interfere with haemopoietic as well as immune regulation. Evidence suggests that bone marrow MSCs may be involved in immune-mediated BMFS underlying pathophysiology, harboring either native abnormalities and/or secondary defects, caused by exposure to activated marrow components. This review summarizes previous as well as more recent information related to the biologic/functional characteristics of bone marrow MSCs in myelodysplastic syndromes, acquired aplastic anemia, and chronic idiopathic neutropenia.

Enhancing the migration ability of mesenchymal stromal cells by targeting the SDF-1/CXCR4 axis

Mesenchymal stromal cells (MSCs) are currently being investigated in numerous clinical trials of tissue repair and various immunological disorders based on their ability to secrete trophic factors and to modulate inflammatory responses. MSCs have been shown to migrate to sites of injury and inflammation in response to soluble mediators including the chemokine stromal cell-derived factor-(SDF-)1, but during in vitro culture expansion MSCs lose surface expression of key homing receptors particularly of the SDF-1 receptor, CXCR4. Here we review studies on enhancement of SDF-1-directed migration of MSCs with the premise that their improved recruitment could translate to therapeutic benefits. We describe our studies on approaches to increase the CXCR4 expression in in vitro-expanded cord blood-derived MSCs, namely, transfection, using the commercial liposomal reagent IBAfect, chemical treatment with the histone deacetylase inhibitor valproic acid, and exposure to recombinant complement component C1q. These methodologies will be presented in the context of other cell targeting and delivery strategies that exploit pathways involved in MSC migration. Taken together, these findings indicate that MSCs can be manipulated in vitro to enhance their in vivo recruitment and efficacy for tissue repair.

Mesenchymal stem cell secretome and regenerative therapy after cancer

Cancer treatment generally relies on tumor ablative techniques that can lead to major functional or disfiguring defects. These post-therapy impairments require the development of safe regenerative therapy strategies during cancer remission. Many current tissue repair approaches exploit paracrine (immunomodulatory, pro-angiogenic, anti-apoptotic and pro-survival effects) or restoring (functional or structural tissue repair) properties of mesenchymal stem/stromal cells (MSC). Yet, a major concern in the application of regenerative therapies during cancer remission remains the possible triggering of cancer recurrence. Tumor relapse implies the persistence of rare subsets of tumor-initiating cancer cells which can escape anti-cancer therapies and lie dormant in specific niches awaiting reactivation via unknown stimuli. Many of the components required for successful regenerative therapy (revascularization, immunosuppression, cellular homing, tissue growth promotion) are also critical for tumor progression and metastasis. While bi-directional crosstalk between tumorigenic cells (especially aggressive cancer cell lines) and MSC (including tumor stroma-resident populations) has been demonstrated in a variety of cancers, the effects of local or systemic MSC delivery for regenerative purposes on persisting cancer cells during remission remain controversial. Both pro- and anti-tumorigenic effects of MSC have been reported in the literature. Our own data using breast cancer clinical isolates have suggested that dormant-like tumor-initiating cells do not respond to MSC signals, unlike actively dividing cancer cells which benefited from the presence of supportive MSC. The secretome of MSC isolated from various tissues may partially diverge, but it includes a core of cytokines (i.e. CCL2, CCL5, IL-6, TGFβ, VEGF), which have been implicated in tumor growth and/or metastasis. This article reviews published models for studying interactions between MSC and cancer cells with a focus on the impact of MSC secretome on cancer cell activity, and discusses the implications for regenerative therapy after cancer.

Mesenchymal stem cells maintain long-term in vitro stemness during explant culture

The advantage of mesenchymal stem cells (MSC) in view of cell and/or tissue replacement after transplantation and their prolonged clinical use raises heavy debates not only in the fields of tissue engineering and regenerative medicine to date. Explant culture of umbilical cord (UC) tissue pieces for more than 190 days demonstrated a similar morphology and proliferation rate of outgrowing MSC as compared to UC tissue cultured for 15 days. Flow cytometric analysis revealed the expression of the typical UC-MSC markers CD73, CD90, and CD105 with concomitant absence of CD14, CD31, CD34, and CD45 in all MSC populations. Moreover, subculture of these long-term tissue-derived MSC exhibited nearly identical population doublings and cell cycle distributions and demonstrated the typical MSC surface markers expression until passage 10 in all different explant cultures. Stem cell-like characteristics were also maintained throughout the long term MSC explant cultures, including telomerase activity and the potential to differentiate along the adipogenic, chondrogenic and osteogenic lineage. In contrast, subculture of MSC for more than 10 passages in the absence of the UC tissue microenvironment was uniformly associated with significantly reduced population doublings, cell cycle accumulation in G0/G1, increased senescence and a diminished expression of MCS markers indicating a progressive loss of stemness in all cultures. Together, these findings demonstrated that the stem cell characteristics of MSC can be maintained during long term in vitro culture in the presence of the originating tissue pieces suggesting that the corresponding tissue provides a microenvironment which is essential for keeping MSC in a stem cell-like state.

In situ tissue regeneration through host stem cell recruitment

The field of tissue engineering has made steady progress in translating various tissue applications. Although the classical tissue engineering strategy, which involves the use of culture-expanded cells and scaffolds to produce a tissue construct for implantation, has been validated, this approach involves extensive cell expansion steps, requiring a lot of time and laborious effort before implantation. To bypass this ex vivo process, a new approach has been introduced. In situ tissue regeneration utilizes the body's own regenerating capacity by mobilizing host endogenous stem cells or tissue-specific progenitor cells to the site of injury. This approach relies on development of a target-specific biomaterial scaffolding system that can effectively control the host microenvironment and mobilize host stem/progenitor cells to target tissues. An appropriate microenvironment provided by implanted scaffolds would facilitate recruitment of host cells that can be guided to regenerating structural and functional tissues.

Thiol-ene Michael-type formation of gelatin/poly(ethylene glycol) biomatrices for three-dimensional mesenchymal stromal/stem cell administration to cutaneous wounds

Mesenchymal stromal/stem cells (MSCs) are considered promising cellular therapeutics in the fields of tissue engineering and regenerative medicine. MSCs secrete high concentrations of immunomodulatory cytokines and growth factors, which exert paracrine effects on infiltrating immune and resident cells in the wound microenvironment that could favorably promote healing after acute injury. However, better spatial delivery and improved retention at the site of injury are two factors that could improve the clinical application of MSCs. In this study, we utilized thiol-ene Michael-type addition for rapid encapsulation of MSCs within a gelatin/poly(ethylene glycol) biomatrix. This biomatrix was also applied as a provisional dressing to full thickness wounds in Sprague-Dawley rats. The three-way interaction of MSCs, gelatin/poly(ethylene glycol) biomatrices, and host immune cells and adjacent resident cells in the wound microenvironment favorably modulated wound progression and host response. In this model we observed attenuated immune cell infiltration, lack of foreign giant cell (FBGC) formation, accelerated wound closure and re-epithelialization, as well as enhanced neovascularization and granulation tissue formation by 7 days. The MSC entrapped in the gelatin/poly(ethylene glycol) biomatrix localized cell presentation adjacent to the wound microenvironment and thus mediated the early resolution of inflammatory events and facilitated the proliferative phases in wound healing.

Presence of osteoclast precursor cells during ex vivo expansion of bone marrow-derived mesenchymal stem cells for autologous use in cell therapy

BACKGROUND AIMS

To obtain a cell product competent for clinical use in terms of cell dose and biologic properties, bone marrow-derived mesenchymal stem cells (MSCs) must be expanded ex vivo.

METHODS

A retrospective analysis was performed of records of 76 autologous MSC products used in phase I or II clinical studies performed in a cohort of cardiovascular patients. In all cases, native MSCs present in patient bone marrow aspirates were separated and expanded ex vivo.

RESULTS

The cell products were classified in two groups (A and B), according to biologic properties and expansion time (ex vivo passages) to reach the protocol-established cell dose. In group A, the population of adherent cells obtained during the expansion period (2 ± 1 passages) was composed entirely of MSCs and met the requirements of cell number and biologic features as established in the respective clinical protocol. In group B, in addition to MSCs, we observed during expansion a high proportion of ancillary cells, characterized as osteoclast precursor cells. In this case, although the biologic properties of the resulting MSC product were not affected, the yield of MSCs was significantly lower. The expansion cycles had to be increased (3 ± 1 passages).

CONCLUSIONS

These results suggest that the presence of osteoclast precursor cells in bone marrow aspirates may impose a limit for the proper clinical use of ex vivo expanded autologous bone marrow-derived MSCs.

Regenerative medicine based applications to combat stress urinary incontinence

Stress urinary incontinence (SUI), as an isolated symptom, is not a life threatening condition. However, the fear of unexpected urine leakage contributes to a significant decline in quality of life parameters for afflicted patients. Compared to other forms of incontinence, SUI cannot be easily treated with pharmacotherapy since it is inherently an anatomic problem. Treatment options include the use of bio-injectable materials to enhance closing pressures, and the placement of slings to bolster fascial support to the urethra. However, histologic findings of degeneration in the incontinent urethral sphincter invite the use of tissues engineering strategies to regenerate structures that aid in promoting continence. In this review, we will assess the role of stem cells in restoring multiple anatomic and physiological aspects of the sphincter. In particular, mesenchymal stem cells and CD34⁺ cells have shown great promise to differentiate into muscular and vascular components, respectively. Evidence supporting the use of cytokines and growth factors such as hypoxia-inducible factor 1-alpha, vascular endothelial growth factor, basic fibroblast growth factor, hepatocyte growth factor and insulin-like growth factor further enhance the viability and direction of differentiation. Bridging the benefits of stem cells and growth factors involves the use of synthetic scaffolds like poly (1,8-octanediol-co-citrate) (POC) thin films. POC scaffolds are synthetic, elastomeric polymers that serve as substrates for cell growth, and upon degradation, release growth factors to the microenvironment in a controlled, predictable fashion. The combination of cellular, cytokine and scaffold elements aims to address the pathologic deficits to urinary incontinence, with a goal to improve patient symptoms and overall quality of life.

Intramuscular transplantation and survival of freshly isolated bone marrow cells following skeletal muscle ischemia-reperfusion injury

BACKGROUND

Delayed treatment cellular therapies offer an attractive means to treat extremity injuries involving acute skeletal muscle ischemia-reperfusion injury (I/R). Bone marrow is a rich source of stem and progenitor cells with the potential to improve skeletal muscle regeneration. The extent to which bone marrow cells (BMCs) may be useful for I/R is not known. The purposes of this study were twofold: (1) to evaluate BMC survival following intramuscular injection 0, 2, 7, and 14 days after injury and (2) to determine whether BMCs improve functional recovery following I/R.

METHODS

Magnetic-activated cell sorting was used to isolate lineage-negative (Lin⁻) BMCs and enrich for stem and progenitor cells. To evaluate in vivo cell survival following I/R, Lin⁻ BMCs were injected intramuscularly 0, 2, 7, and 14 days after I/R, and bioluminescent imaging was performed for up to 28 days after cell injections. To assess their ability to improve muscle regeneration, intramuscular injections were performed 2 days after injury, and in vivo muscle function was assessed 14 days later.

RESULTS

Lin⁻ BMCs survived throughout the study period regardless of the timing of delivery. Intramuscular injection of Lin⁻ BMCs did not improve maximal isometric torque (300 Hz); however, both saline-injected and Lin⁻ BMC-injected muscles exhibited an increase in the twitch-tetanus ratio, suggesting that damage incurred with the intramuscular injections may have had deleterious consequences for functional recovery.

CONCLUSION

Although BMCs injected intramuscularly survived cell transplantation, they failed to improve muscle function following I/R. The ability of BMCs to persist in injured muscle following I/R lends to the possibility that with further development, their full potential can be realized.

Engineering stem cell fate with biochemical and biomechanical properties of microcarriers

Microcarriers have been widely used for various biotechnology applications because of their high scale-up potential, high reproducibility in regulating cellular behavior, and well-documented compliance with current Good Manufacturing Practices (cGMP). Recently, microcarriers have been emerging as a novel approach for stem cell expansion and differentiation, enabling potential scale-up of stem cell-derived products in large bioreactors. This review summarizes recent advances of using microcarriers in mesenchymal stem cell (MSC) and pluripotent stem cell (PSC) cultures. From the reported data, efficient expansion and differentiation of stem cells on microcarriers rely on their ability to modulate cell shape (i.e. round or spreading) and cell organization (i.e. aggregate size). Nonetheless, current screening of microcarriers remains empirical, and accurate understanding of how stem cells interact with microcarriers still remains unknown. This review suggests that accurate characterization of biochemical and biomechanical properties of microcarriers is required to fully exploit their potential in regulating stem cell fate decision. Due to the variety of microcarriers, such detailed analyses should lead to the rational design of application-specific microcarriers, enabling the exploitation of reproducible effects for large scale biomedical applications.

Perspectives on the use of stem cells for autism treatment

Autism and autism spectrum disorders (ASDs) are complex neurodevelopmental disorders. ASDs are clinically defined by deficits in communication, social skills, and repetitive and/or restrictive interests and behaviours. With the prevalence rates for ASDs rapidly increasing, the need for effective therapies for autism is a priority for biomedical research. Currently available medications do not target the core symptoms, can have markedly adverse side-effects, and are mainly palliative for negative behaviours. The development of molecular and regenerative interventions is progressing rapidly, and medicine holds great expectations for stem cell therapies. Cells could be designed to target the observed molecular mechanisms of ASDs, that is, abnormal neurotransmitter regulation, activated microglia, mitochondrial dysfunction, blood-brain barrier disruptions, and chronic intestinal inflammation. Presently, the paracrine, secretome, and immunomodulatory effects of stem cells would appear to be the likely mechanisms of application for ASD therapeutics. This review will focus on the potential use of the various types of stem cells: embryonic, induced pluripotential, fetal, and adult stem cells as targets for ASD therapeutics.