Safety of intravenous infusion of human adipose tissue-derived mesenchymal stem cells in animals and humans

The substrate-dependent regeneration capacity of mesenchymal stem cell spheroids derived on various biomaterial surfaces

ADSC spheroids derived on various biomaterials present different in vitro properties, which may explain their different efficacies in cartilage repair.

Safety assessment of myogenic stem cell transplantation and resulting tumor formation

OBJECTIVES

To assess for stem cell migration to liver and lung after transplantation in injured rat anal sphincters. To evaluate histological findings of unanticipated ectopic foci of growth.

METHODS

This is a prospective study involving 33 female virginal Sprague-Dawley rats. Anal sphincters were transected and repaired under sterile technique. Animals received injections of 5.0 × 10 myogenic stem cells (24 rats) or sham control (9 rats) and were killed on day 30. Liver and lung samples were obtained. Upon encountering abnormal foci of growth, further staining protocols were employed. Enzyme-linked immunosorbent assay studies evaluated stem cell media for in vitro growth factor secretion.

RESULTS

No evidence of cell migration to liver or lung was found at the time of euthanasia in any study animal. Ectopic foci of growth were noted in 2 transplant rats. Further histological evaluations of these growths were consistent with benign tumors: no nuclear abnormalities and no evidence of proliferation at day 30. Enzyme-linked immunosorbent assay studies demonstrated positive secretion of vascular endothelial growth factor and insulin growth factor into the media of cultured rat myogenic stem cells.

CONCLUSIONS

Whereas distant migration was not encountered in the liver or lung, 2 transplanted rats developed abnormal foci of growth, that is, tumors, from the external anal sphincter-raising further safety questions. Additional evaluation of these foci seemed benign. Possible explanations include cell trapping, stem cell overgrowth, and/or paracrine factors. The lack of cell migration supports that future investigation of safety parameters could focus locally.

Small molecules and small molecule drugs in regenerative medicine

Regenerative medicine is an emerging, multidisciplinary science that aims to replace or regenerate human cells, tissues or organs, to restore or establish normal function. Research on small molecules and small molecule drugs in regenerative medicine is currently increasing. In this review, we discuss the potential applications of small molecules and small molecule drugs in regenerative medicine. These include enabling novel cell therapy approaches and augmentation of endogenous cells for tissue regeneration, facilitating the generation of target cells for cell therapy, improving the interactions between cells and biomatrices for tissue engineering, and enhancing endogenous stem cell function for tissue regeneration. We also discuss the potential challenges for small molecule drugs in regenerative medicine.

Mesenchymal stem cells: environmentally responsive therapeutics for regenerative medicine

Mesenchymal stem cells (MSCs) are partially defined by their ability to differentiate into tissues including bone, cartilage and adipose in vitro, but it is their trophic, paracrine and immunomodulatory functions that may have the greatest therapeutic impact in vivo. Unlike pharmaceutical treatments that deliver a single agent at a specific dose, MSCs are site regulated and secrete bioactive factors and signals at variable concentrations in response to local microenvironmental cues. Significant progress has been made in understanding the biochemical and metabolic mechanisms and feedback associated with MSC response. The anti-inflammatory and immunomodulatory capacity of MSC may be paramount in the restoration of localized or systemic conditions for normal healing and tissue regeneration. Allogeneic MSC treatments, categorized as a drug by regulatory agencies, have been widely pursued, but new studies demonstrate the efficacy of autologous MSC therapies, even for individuals affected by a disease state. Safety and regulatory concerns surrounding allogeneic cell preparations make autologous and minimally manipulated cell therapies an attractive option for many regenerative, anti-inflammatory and autoimmune applications.

Cellular therapeutics delivery to the spinal cord: technical considerations for clinical application

Current literature demonstrates the efficacy of cell-based therapeutics in small animal models of varied spinal cord diseases. However, logistic challenges remain towards development of an optimized delivery approach to the human spinal cord. Clinical trials utilize a variety of methods to achieve this aim. In this article, the authors review currently employed delivery methods, compare the merits of alternate delivery paradigms, introduce their implementation in completed and ongoing clinical trials, and discuss promising near-term advances in image-guided delivery and in vivo graft tracking.

An Update on Translating Stem Cell Therapy for Stroke from Bench to Bedside

With a constellation of stem cell sources available, researchers hope to utilize their potential for cellular repair as a therapeutic target for disease. However, many lab-to-clinic translational considerations must be given in determining their efficacy, variables such as the host response, effects on native tissue, and potential for generating tumors. This review will discuss the current knowledge of stem cell research in neurological disease, mainly stroke, with a focus on the benefits, limitations, and clinical potential.

Analysis of the karyotype of expanded human adipose-derived stem cells for bone reconstruction of the maxillo-facial region

Mesenchymal stem cells (MSC) and adipose-derived stem cells (ASC) were recently proposed for bone maxillofacial reconstruction in association with biomaterials. For this application MSC must be ex-vivo expanded in order to obtain, for a given volume of implanted biomaterial, a relevant number of bone forming cells. Previously conducted pre-clinical studies suggested that a concentration of 6 x 10(8) ASC associated with 900 mg of anorganic bovine bone (ABB) could be effective for human maxillary sinus floor elevation. A keystone issue to guarantee the quality and safety of Advanced Therapy Medicinal Products containing expanded MSC and ASC is their chromosome stability in culture: this topic has been widely investigated and conflicting results have been published. Abnormal karyotype of human ex-vivo expanded MSC and ASC was found by some authors, while, at the same time, several other studies showed the MSC and ASC karyotype to be normal. It is therefore important that all the results obtained on MSC and ASC karyotype analysis be published. Given this context, the aim of this manuscript, aim of this manuscript is to verify the karyotype stability of ASC in view of their applications in clinical trials. ASC obtained from the adipose tissue of 4 donors were expanded over extended culture time. Based on previous ASC expansions we hypothesized to be able to obtain 6 x 10(8) cells by passage 7. Karyotype analysis of 30 metaphases was planned to be investigated at passage 2, 7, and 15 in all the cultures. No abnormalities were found in the karyotype of two donors at all the passages tested, while a translocation was found in 2 metaphases of a donor at passage 7, but not at passage 15, and in the fourth donor in 5 metaphases a trisomy was found at passage 15. Chromosomal abnormalities were detected only after extended ASC expansion. Whether these anomalies can be related to risk for the patient's safety will have to be demonstrated by in-vivo studies.

The therapeutic effects of human adipose-derived stem cells in Alzheimer's disease mouse models

Alzheimer's disease (AD) is an irreversible neurodegenerative disease, still lacking proper clinical treatment. Therefore, many researchers have focused on the possibility of therapeutic use of stem cells for AD. Adipose-derived stem cells (ASCs), mesenchymal stem cells (MSCs) isolated from adipose tissue, are well known for their pluripotency and their ability to differentiate into multiple tissue types and have immune modulatory properties similar to those of MSCs from other origins. Because of their biological properties, ASCs can be considered for cell therapy and neuroregeneration. Our recent results clearly showed the therapeutic potential of these cells after transplantation into Tg2576 mice (an AD mouse model). Intravenously or intracerebrally transplanted human ASCs (hASCs) greatly improved the memory impairment and the neuropathology, suggesting that hASCs have a high therapeutic potential for AD.

Transplantation of human adipose tissue-derived stem cells delays clinical onset and prolongs life span in ALS mouse model

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that selectively affects motor neurons in the cortex, brain stem, and spinal cord. The precise pathogenic mechanism remains unknown, and there is currently no effective therapy. We evaluated the therapeutic effects of human adipose tissue-derived stem cells (ASCs) in an animal model of ALS. Human abdominal subcutaneous fat tissues were obtained by simple liposuction from donors, and ASCs were isolated from the fat stromal vascular fraction. ASCs were found to differentiate into adipocytes, chondrocytes, osteocytes, and neurons. SOD1G93A ALS mice were divided into three groups: sham, intravenous (IV), and intracerebroventricular (ICV) groups. Human ASCs were transplanted in the ALS mice at 70 postnatal days before the appearance of clinical symptoms. Behavior of transplanted animals was assessed by rotarod test, paw grip endurance (PaGE), and reflex index. Mice in every group were sacrificed after 4 weeks posttransplantation. Transplanted ASCs were identified in the lumbar spinal cords with an antihuman mitochondria antibody and cell type-specific markers for neurons or astrocytes. Delayed onset of clinical symptoms (26 days) and extended survival of animals (24 days) were observed in ALS mice transplanted with ASCs via ICV route. ASCs were found to secrete high levels of neurotrophic factors such as NGF, BDNF, IGF-1, and VEGF. Reduction of apoptotic cell death by these factors was confirmed in cultured CNS cells and in the ALS spinal cord. These results indicate that transplantation of ASCs in ALS mice provides neuroprotective effects by production of cytokines/growth factors, delays disease progression, and prolongs the life span of ALS mice.

Immunomodulatory effects of adipose-derived stem cells: fact or fiction?

Adipose-derived stromal cells (ASCs) are often referred to as adipose-derived stem cells due to their potential to undergo multilineage differentiation. Their promising role in tissue engineering and ability to modulate the immune system are the focus of extensive research. A number of clinical trials using ASCs are currently underway to better understand the role of such cell niche in enhancing or suppressing the immune response. If governable, such immunoregulatory role would find application in several conditions in which an immune response is present (i.e., autoimmune conditions) or feared (i.e., solid organ or reconstructive transplantation). Although allogeneic ASCs have been shown to prevent acute GvHD in both preclinical and clinical studies, their potential warrants further investigation. Well-designed and standardized clinical trials are necessary to prove the role of ASCs in the treatment of immune disorders or prevention of tissue rejection. In this paper we analyze the current literature on the role of ASCs in immunomodulation in vitro and in vivo and discuss their potential in regulating the immune system in the context of transplantation.

Genetic stability of bone marrow-derived human mesenchymal stromal cells in the Quantum System

BACKGROUND AIMS

The Quantum® Cell Expansion System (Quantum; Terumo BCT, Inc, Lakewood, CO, USA) is a novel hollow fiber-based device that automates and closes the cell culture process, reducing labor intensive tasks such as manual cell culture feeding and harvesting. The manual cell selection and expansion processes for the production of clinical-scale quantities of bone marrow-derived human mesenchymal stromal cells (BM-hMSCs) have been successfully translated onto the Quantum platform previously. The formerly static, manual, in vitro process performed primarily on tissue culture polystyrene substrates may raise the question of whether BM-hMSCs cultured on a hollow fiber platform yields comparable cell quality.

METHODS

A rigorous battery of assays was used to determine the genetic stability of BM-hMSCs selected and produced with the Quantum. In this study, genetic stability was determined by assessing spectral karyotype, micronucleus formation and tumorigenicity to resolve chromosomal aberrations in the stem cell population. Cell phenotype, adherent growth kinetics and tri-lineage differentiation were also evaluated. HMSC bone marrow aspirates, obtained from three approved donors, were expanded in parallel using T225 culture flasks and the Quantum.

RESULTS

BM-hMSCs harvested from the Quantum demonstrated immunophenotype, morphology and tri-lineage differentiation capacity characteristics consistent with the International Society of Cell Therapy standard for hMSCs. Cell populations showed no malignant neoplastic formation in athymic mice 60 days post-transplant, no clonal chromosomal aberrations were observed and no DNA damage was found as measured by micronucleus formation.

CONCLUSIONS

Quantum-produced BM-hMSCs are of comparable quality and demonstrate analogous genetic stability to BM-hMSCs cultured on tissue culture polystyrene substrates.

Mesenchymal stem cells from human umbilical cord express preferentially secreted factors related to neuroprotection, neurogenesis, and angiogenesis

Mesenchymal stem cells (MSCs) are promising tools for the treatment of diseases such as infarcted myocardia and strokes because of their ability to promote endogenous angiogenesis and neurogenesis via a variety of secreted factors. MSCs found in the Wharton’s jelly of the human umbilical cord are easily obtained and are capable of transplantation without rejection. We isolated MSCs from Wharton’s jelly and bone marrow (WJ-MSCs and BM-MSCs, respectively) and compared their secretomes. It was found that WJ-MSCs expressed more genes, especially secreted factors, involved in angiogenesis and neurogenesis. Functional validation showed that WJ-MSCs induced better neural differentiation and neural cell migration via a paracrine mechanism. Moreover, WJ-MSCs afforded better neuroprotection efficacy because they preferentially enhanced neuronal growth and reduced cell apoptotic death of primary cortical cells in an oxygen-glucose deprivation (OGD) culture model that mimics the acute ischemic stroke situation in humans. In terms of angiogenesis, WJ-MSCs induced better microvasculature formation and cell migration on co-cultured endothelial cells. Our results suggest that WJ-MSC, because of a unique secretome, is a better MSC source to promote in vivo neurorestoration and endothelium repair. This study provides a basis for the development of cell-based therapy and carrying out of follow-up mechanistic studies related to MSC biology.

Systemic transplantation of human adipose tissue-derived mesenchymal stem cells for the regeneration of irradiation-induced salivary gland damage

Objectives

Cell-based therapy has been reported to repair or restore damaged salivary gland (SG) tissue after irradiation. This study was aimed at determining whether systemic administration of human adipose-derived mesenchymal stem cells (hAdMSCs) can ameliorate radiation-induced SG damage.

Methods

hAdMSCs (1×10⁶) were administered through a tail vein of C3H mice immediately after local irradiation, and then this infusion was repeated once a week for 3 consecutive weeks. At 12 weeks after irradiation, functional evaluations were conducted by measuring salivary flow rates (SFRs) and salivation lag times, and histopathologic and immunofluorescence histochemistry studies were performed to assay microstructural changes, apoptosis, and proliferation indices. The engraftment and in vivo differentiation of infused hAdMSCs were also investigated, and the transdifferentiation of hAdMSCs into amylase-producing SG epithelial cells (SGCs) was observed in vitro using a co-culture system.

Results

The systemic administration of hAdMSCs exhibited improved SFRs at 12 weeks after irradiation. hAdMSC-transplanted SGs showed fewer damaged and atrophied acinar cells and higher mucin and amylase production levels than untreated irradiated SGs. Immunofluorescence TUNEL assays revealed fewer apoptotic cells in the hAdMSC group than in the untreated group. Infused hAdMSCs were detected in transplanted SGs at 4 weeks after irradiation and some cells were found to have differentiated into SGCs. In vitro, a low number of co-cultured hAdMSCs (13%–18%) were observed to transdifferentiate into SGCs.

Conclusion

The findings of this study indicate that hAdMSCs have the potential to protect against irradiation-induced cell loss and to transdifferentiate into SGCs, and suggest that hAdMSC administration should be viewed as a candidate therapy for the treatment of radiation-induced SG damage.

Evolution and future prospects of adipose-derived immunomodulatory cell therapeutics

Over the past two decades, tissue engineering and regenerative medicine have evolved from what many considered a theoretical science to what is now a clinical reality. Tissue engineering combines biomaterial scaffolds, growth factors and stem or progenitor cells to repair damaged tissues. Adipose tissue, an abundant and easily accessed tissue, is a potential source of stromal/stem cells for regenerative therapeutic applications. Like bone marrow-derived mesenchymal stem cells, adipose-derived stromal/stem cells display both immunomodulatory and immunosuppressive properties. The adipose cells exert these actions, in part, through their secretion of paracrine growth factors. This review highlights recent developments in the isolation, characterization and preclinical application of adipose-derived cells and the challenges facing their translation into clinical practice.

Multipotent mesenchymal stromal cell therapy and risk of malignancies

Cell therapy with Multipotent Mesenchymal Stromal Cells (MSC) holds enormous promise for the treatment of a large number of degenerative and immune/inflammatory diseases. Their multilineage differentiation potential, immunoprivilege and capacity of promoting recovery of damaged tissues coupled with anti-inflammatory and immunosuppressive properties are the focus of a multitude of clinical studies currently underway. The recognized clinical potential of MSC repairing/immunomodulatory effects now encompasses graft-versus-host disease, hematologic malignancies, cardiovascular diseases, neurologic and inherited diseases, autoimmune diseases, organ transplantation, refractory wounds, and bone/cartilage defects among others. However, it has been suggested that both the need of extensive ex vivo culture for MSC clinical use, and their proangiogenic, anti-apoptotic and immunomodulatory properties may act together as tumor promoters, raising significant safety concerns. This paper will review the available data on in vitro MSC maldifferentiation and the ability of MSC to sustain tumor growth in vivo, with the aim to clarify whether MSC-based therapeutic approaches may carry actual risk of malignancies.

Adipose tissue-derived multipotent stromal cells have a higher immunomodulatory capacity than their bone marrow-derived counterparts

Adipose tissue-derived multipotent stromal cells (AT-MSCs) are studied as an alternative to bone marrow-derived multipotent stromal cells (BM-MSCs) for immunomodulatory treatment. In this study, we systematically compared the immunomodulatory capacities of BM-MSCs and AT-MSCs derived from age-matched donors. We found that BM-MSCs and AT-MSCs share a similar immunophenotype and capacity for in vitro multilineage differentiation. BM-MSCs and AT-MSCs showed comparable immunomodulatory effects as they were both able to suppress proliferation of stimulated peripheral blood mononuclear cells and to inhibit differentiation of monocyte-derived immature dendritic cells. However, at equal cell numbers, the AT-MSCs showed more potent immunomodulatory effects in both assays as compared with BM-MSCs. Moreover, AT-MSCs showed a higher level of secretion of cytokines that have been implicated in the immunomodulatory modes of action of multipotent stromal cells, such as interleukin-6 and transforming growth factor-β1. This is correlated with higher metabolic activity of AT-MSCs compared with BM-MSCs. We conclude that the immunomodulatory capacities of BM-MSCs and AT-MSCs are similar, but that differences in cytokine secretion cause AT-MSCs to have more potent immunomodulatory effects than BM-MSCs. Therefore, lower numbers of AT-MSCs evoke the same level of immunomodulation. These data indicate that AT-MSCs can be considered as a good alternative to BM-MSCs for immunomodulatory therapy.

Combination therapy of human adipose-derived stem cells and basic fibroblast growth factor hydrogel in muscle regeneration

Skeletal muscle regeneration after sport injury is inconsistent, and complete healing without fibrosis is very important. In this study, we determined whether the combination therapy using human adipose-derived stem cells (h-ADSCs) and basic fibroblast growth factor (bFGF) incorporated into hydrogel could enhance muscle regeneration in a muscle laceration animal model. The h-ADSCs and/or bFGF hydrogels were applied to the lacerated gastrocnemius muscle. Fast twitch muscle contraction improved significantly and fibrosis decreased significantly in combined h-ADSC and bFGF-hydrogel group compared to other experimental groups. Skeletal muscle differentiation of h-ADSCs was determined by immunohistochemistry (PKH-26/MyHC co-staining) and Western blot. Our data suggested that combination therapy of h-ADSCs and bFGF hydrogel resulted in functional recovery, revascularization and reinnervation with minimal fibrosis in lacerated muscle. A combination of h-ADSCs and bFGF hydrogel can be used as a promising therapy for skeletal muscle regeneration.

Stem cell therapy: an exercise in patience and prudence

In recent times, the epigenetic study of pluripotency based on cellular reprogramming techniques led to the creation of induced pluripotent stem cells. It has come to represent the forefront of a new wave of alternative therapeutic approaches in the field of stem cell therapy. Progress in drug development has saved countless lives, but there are numerous intractable diseases where curative treatment cannot be achieved through pharmacological intervention alone. Consequently, there has been an unfortunate rise in incidences of organ failures, degenerative disorders and cancers, hence novel therapeutic interventions are required. Stem cells have unique self-renewal and multilineage differentiation capabilities that could be harnessed for therapeutic purposes. Although a number of mature differentiated cells have been characterized in vitro, few have been demonstrated to function in a physiologically relevant context. Despite fervent levels of enthusiasm in the field, the reality is that other than the employment of haematopoietic stem cells, many other therapies have yet to be thoroughly proven for their therapeutic benefit and safety in application. This review shall focus on a discussion regarding the current status of stem cell therapy, the issues surrounding it and its future prospects with a general background on the regulatory networks underlying pluripotency.

Towards clinical application of mesenchymal stem cells for treatment of neurological diseases of the central nervous system

The diagnosis of a neurological disease of the central nervous system (CNS) is often associated with the anticipation of an irreversible and untreatable disability. This is the case also of multiple sclerosis (MS) where approved treatments effectively modulate the autoimmune attack to myelin antigens, but poorly affect neurodegeneration and do not promote tissue repair. Thus, stem cell-based therapies are increasingly being considered a possible strategy for diseases of the CNS. Mesenchymal stem cells (MSC), the safety of which has been demonstrated in the last 20 years through clinical trials and case studies, are of particular interest in view not only of their neuroprotective, but also of their immunomodulatory properties. Here, we review the therapeutic features of MSC that make them relevant in the treatment of CNS illnesses and discuss the pioneer clinical experience with MSC-based therapy in neurological diseases.

Generation of mesenchymal stem cells as a medicinal product in organ transplantation

PURPOSE OF REVIEW

Mesenchymal stem cells (MSCs) are emerging as an alternative treatment in solid-organ transplantation. The use of MSCs as a therapeutic product requires the translation of basic research protocols into a production process under good manufacturing practice (GMP) to obtain a safe product of high quality. This requires a different mindset from the academic setting of changing protocols into a well defined, controlled and documented process. This review describes some of the challenges faced by culturing MSCs as a medicinal product.

RECENT FINDINGS

Clinical-grade MSCs are used in the clinical trials and proved to be safe as a medicinal product. Because of the differences in the type of MSCs and in the production process, clinical outcome is not always comparable. New standardized methods in the culture condition such as the use of alternatives for fetal bovine serum (FBS), standardized plating densities or the use of bioreactors may further standardize the production process.

SUMMARY

To generate MSCs as a medicinal product in organ transplantation, regulation requires that MSCs have to be generated under GMP. During the whole production process, all critical steps should be known and described. Further steps should be taken to optimize and standardize the production process.

Human adipose tissue derived mesenchymal stem cells aggravate chronic cyclosporin nephrotoxicity by the induction of oxidative stress

The aim of this study was to investigate whether hATMSCs protect against cyclosporine (CsA)-induced renal injury. CsA (7.5 mg/kg) and hATMSCs (3×10⁶/5 mL) were administered alone and together to rats for 4 weeks. The effect of hATMSCs on CsA-induced renal injury was evaluated by assessing renal function, interstitial fibrosis, infiltration of inflammatory cells, and apoptotic cell death. Four weeks of CsA-treatment produced typical chronic CsA-nephropathy. Combined treatment with CsA and hATMSCs did not prevent these effects and showed a trend toward further renal deterioration. To evaluate why hATMSCs aggravated CsA-induced renal injury, we measured oxidative stress, a major mechanism of CsA-induced renal injury. Both urine and serum 8-hydroxydeoxyguanosine(8-OHdG) levels were higher in the CsA+hATMSCs group than in the CsA group (P<0.05). An in vitro study showed similar results. Although the rate of apoptosis did not differ significantly between HK-2 cells cultured in hATMSCs-conditioned medium and those cultured in DMEM, addition of CsA resulted in greater apoptosis in HK-2 cells cultured in hATMSCs-conditioned medium. Addition of CsA increased oxidative stress in the hATMSCs-conditioned medium. The results of our study suggest that treatment with hATMSCs may aggravate CsA-induced renal injury because hATMSCs cause oxidative stress in the presence of CsA.

[Intravenous infusion of adult adipose tissue stem cells for repairing spinal cord ischaemic lesions. An experimental study on animals]

OBJECTIVE

To assess if a peripheral intravenous infusion of adipose tissue stem cells (ATSC), after an ischemic spinal cord injury can promote selective cell migration and cell survival in the damaged neural tissue. ANIMALS AND METHOD: An ischaemic spinal cord injury was provoked by trapping the abdominal aorta for 20 minutes in 11 male New Zealand rabbits (2.5±0.5kg). They were randomised into two groups: one group (n=5) received an intravenous transfusion of 10±2×10(6) ATSC at 24 hours from the injury, and the control group (n=6) were only given the vehicle. The functional status was assessed, using the Tarlov scale at 24h, and 7 and 14 days. The animals were sacrificed at 14 days and a histological and immunohistochemical study was performed.

RESULTS

Complete paraplegia was achieved in both groups. There were no significant differences as regards neurological recovery, which was nil in both cases. In the histological and immunohistochemical study, it was tested to see if there was any bromodeoxyuridine-marked ATSC in the area of the lesion, but there was only a small amount.

CONCLUSION

ATSC are able to migrate and survive in the injured spinal cord after aortic ischaemia after they have been administered intravenously. Intravenous infusion is a harmless procedure with no side effect. No neurological recovery was achieved.

Characteristics of mouse adipose tissue-derived stem cells and therapeutic comparisons between syngeneic and allogeneic adipose tissue-derived stem cell transplantation in experimental autoimmune thyroiditis

Previously, we found that the intravenous administration of human adipose tissue-derived mesenchymal stem cells was a promising therapeutic option for autoimmune thyroiditis even when the cells were transplanted into a xenogeneic model without an immunosuppressant. Therefore, we explored the comparison between the therapeutic effects of syngeneic and allogeneic adipose tissue-derived stem cells on an experimental autoimmune thyroiditis mouse model. Experimental autoimmune thyroiditis was induced in C57BL/6 mice by immunization with porcine thyroglobulin. Adipose tissue-derived stem cells derived from C57BL/6 mice (syngeneic) or BALB/c mice (allogeneic) or saline as a vehicle control were administered intravenously four times weekly. Blood and tissue samples were collected 1 week after the last transplantation. Adipose tissue-derived stem cells from mice were able to differentiate into multiple lineages in vitro; however, mouse adipose tissue-derived stem cells did not have immunophenotypes identical to those from humans. Syngeneic and allogeneic administrations of adipose tissue-derived stem cells reduced thyroglobulin autoantibodies and the inflammatory immune response, protected against lymphocyte infiltration into the thyroid, and restored the Th1/Th2 balance without any adverse effects. However, different humoral immune responses were observed for infused cells from different stem cell sources. The strongest humoral immune response was induced by xenogeneic transplantation, followed by allogeneic and syngeneic administration, in that order. The stem cells were mostly found in the spleen, not the thyroid. This migration might be because the stem cells primarily function in systemic immune modulation, due to being given prior to disease induction. In this study, we confirmed that there were equal effects of adipose tissue-derived stem cells in treating autoimmune thyroiditis between syngeneic and allogeneic transplantations.

Mesenchymal autologous stem cells

The use of cell-based therapies for spinal cord injuries has recently gained prominence as a potential therapy or component of a combination strategy. Experimental and clinical studies have been performed using mesenchymal stem cell therapy to treat spinal cord injuries with encouraging results. However, there have been reports on the adverse effects of these stem cell-based therapies, especially in the context of tumor modulation. This article surveys the literature relevant to the potential of mesenchymal autologous stem cells for spinal cord injuries and their clinical implications.

Do mesenchymal stem cells function across species barriers? Relevance for xenotransplantation

BACKGROUND

Allogeneic mesenchymal stem (stromal) cells (MSC) are a promising therapy for various pathological conditions. Genetically modified pig MSC have been demonstrated to downregulate the human T-cell response to pig antigens in vitro. Before genetically modified pig MSC can be used clinically, however, evidence needs to be provided to indicate whether they will survive in a human (xenogeneic) host.

LITERATURE SEARCH AND RESULTS

A literature search through the end of 2011 identified 94 reports of the in vivo cross-species administration of MSC in a variety of experimental models. The majority (n = 89) involved the use of human MSC in various other species, with an occasional study using pig, rat, or guinea-pig MSC. When human MSC were used, they were largely derived from the bone marrow, adipose tissue, or umbilical cord blood. The routes of administration were varied, although almost half of the studies utilized the intravenous route. In 88 experiments (93.6%), there was evidence that the MSC engrafted and functioned across the species barrier, and in only six cases (6.4%) was there evidence of failure to function. Importantly, MSC function was confirmed in several different cross-species models. For example, human MSC functioned in no fewer than seven different recipient species.

CONCLUSIONS

The data provided by this literature search strengthen the hypothesis that pig MSC will function satisfactorily in a different species, for example, humans. The data also suggest that our own in vitro observations on the efficacy of pig MSC in downregulating the strength of the human T-cell response to pig antigens will likely be reproduced in vivo in pre-clinical large animal models and in clinical trials.

Human adipose tissue-derived mesenchymal stem cells improve cognitive function and physical activity in ageing mice

Brain ageing leads to atrophy and degeneration of the cholinergic nervous system, resulting in profound neurobehavioral and cognitive dysfunction from decreased acetylcholine biosynthesis and reduced secretion of growth and neurotrophic factors. Human adipose tissue-derived mesenchymal stem cells (ADMSCs) were intravenously (1 × 10(6) cells) or intracerebroventricularly (4 × 10(5) cells) transplanted into the brains of 18-month-old mice once or four times at 2-week intervals. Transplantation of ADMSCs improved both locomotor activity and cognitive function in the aged animals, in parallel with recovery of acetylcholine levels in brain tissues. Transplanted cells differentiated into neurons and, in part, into astrocytes and produced choline acetyltransferase proteins. Transplantation of ADMSCs restored microtubule-associated protein 2 in brain tissue and enhanced Trk B expression and the concentrations of brain-derived neurotrophic factor and nerve growth factor. These results indicate that human ADMSCs differentiate into neural cells in the brain microenvironment and can restore physical and cognitive functions of aged mice not only by increasing acetylcholine synthesis but also by restoring neuronal integrity that may be mediated by growth/neurotrophic factors. © 2013 Wiley Periodicals, Inc.

Transplantation of Human Adipose Tissue-Derived Mesenchymal Stem Cells Restores the Neurobehavioral Disorders of Rats With Neonatal Hypoxic-Ischemic Encephalopathy

Improving the effects of human adipose tissue-derived mesenchymal stem cells (ASCs) on the demyelination and neurobehavioral function was investigated in an experimental model of neonatal hypoxic-ischemic encephalopathy (HIE). Seven-day-old male rats were subjected to hypoxia-ischemia-lipopolysaccharide and intracerebroventricularly transplanted with human ASCs (4 × 10(5) cells/rat) once at postnatal day 10 (PND10) or repeatedly at PND10, 17, 27, and 37. Neurobehavioral abnormalities (at PND20, 30, and 40) and cognitive functions (at PND41-44) were evaluated using multiple test systems. Human ASCs recovered the using ratio of forelimb contralateral to the injured brain, improved locomotor activity, and restored rota-rod performance of HIE animals, in addition to showing a marked improvement of cognitive functions. It was confirmed that transplanted human ASCs migrated to injured areas and differentiated into oligodendrocytes expressing myelin basic protein (MBP). Moreover, transplanted ASCs restored production of growth and neurotrophic factors and expression of decreased inflammatory cytokines, leading to attenuation of host MBP loss. The results indicate that transplanted ASCs restored neurobehavioral functions by producing MBP as well as by preserving host myelins, which might be mediated by ASCs' anti-inflammatory activity and release of growth and neurotrophic factors.

Comparison of the therapeutic effects of human and mouse adipose-derived stem cells in a murine model of lipopolysaccharide-induced acute lung injury

INTRODUCTION

Adipose-derived stem cells (ASCs) have emerged as important regulators of inflammatory/immune responses in vitro and in vivo and represent attractive candidates for cell-based therapies for diseases that involve excessive inflammation. Acute lung injury (ALI) is an inflammatory condition for which treatment is mainly supportive due to lack of effective therapies. In this study, the therapeutic effects of ASC-based therapy were assessed in vivo by comparison of the anti-inflammatory properties of both human and murine ASCs in a mouse model of lipopolysaccharide (LPS)-induced ALI.

METHODS

Human ASCs (hASCs) or mouse ASCs (mASCs) were delivered to C57Bl/6 mice (7.5 × 105 total cells/mouse) by oropharyngeal aspiration (OA) four hours after the animals were challenged with lipopolysaccharide (15 mg/kg). Mice were sacrificed 24 and 72 hours after LPS exposure, and lung histology examined for evaluation of inflammation and injury. Bronchoalveolar lavage fluid (BALF) was analyzed to determine total and differential cell counts, total protein and albumin concentrations, and myeloperoxidase (MPO) activity. Cytokine expression in the injured lungs was measured at the steady-state mRNA levels and protein levels for assessment of the degree of lung inflammation.

RESULTS

Both human and mouse ASC treatments provided protective anti-inflammatory responses. There were decreased levels of leukocyte (for example neutrophil) migration into the alveoli, total protein and albumin concentrations in BALF, and MPO activity after the induction of ALI following both therapies. Additionally, cell therapy with both cell types effectively suppressed the expression of proinflammatory cytokines and increased the anti-inflammatory cytokine interleukin 10 (IL-10). Overall, the syngeneic mASC therapy had a more potent therapeutic effect than the xenogeneic hASC therapy in this model.

CONCLUSIONS

Treatment with hASCs or mASCs significantly attenuated LPS-induced acute lung injury in mice. These results suggest a potential benefit for using an ASC-based therapy to treat clinical ALI and may possibly prevent the development of acute respiratory distress syndrome (ARDS).

Optimizing patient derived mesenchymal stem cells as virus carriers for a phase I clinical trial in ovarian cancer

Background

Mesenchymal stem cells (MSC) can serve as carriers to deliver oncolytic measles virus (MV) to ovarian tumors. In preparation for a clinical trial to use MSC as MV carriers, we obtained cells from ovarian cancer patients and evaluated feasibility and safety of this approach.

Methods

MSC from adipose tissues of healthy donors (hMSC) and nine ovarian cancer patients (ovMSC) were characterized for susceptibility to virus infection and tumor homing abilities.

Results

Adipose tissue (range 0.16-3.96 grams) from newly diagnosed and recurrent ovarian cancer patients yielded about 7.41×10⁶ cells at passage 1 (range 4–9 days). Phenotype and doubling times of MSC were similar between ovarian patients and healthy controls. The time to harvest of 3.0×10⁸ cells (clinical dose) could be achieved by day 14 (range, 9–17 days). Two of nine samples tested had an abnormal karyotype represented by trisomy 20. Despite receiving up to 1.6×10⁹ MSC/kg, no tumors were seen in SCID beige mice and MSC did not promote the growth of SKOV3 human ovarian cancer cells in mice. The ovMSC migrated towards primary ovarian cancer samples in chemotaxis assays and to ovarian tumors in athymic mice. Using non-invasive SPECT-CT imaging, we saw rapid co-localization, within 5–8 minutes of intraperitoneal administration of MV infected MSC to the ovarian tumors. Importantly, MSC can be pre-infected with MV, stored in liquid nitrogen and thawed on the day of infusion into mice without loss of activity. MV infected MSC, but not virus alone, significantly prolonged the survival of measles immune ovarian cancer bearing animals.

Conclusions

These studies confirmed the feasibility of using patient derived MSC as carriers for oncolytic MV therapy. We propose an approach where MSC from ovarian cancer patients will be expanded, frozen and validated to ensure compliance with the release criteria. On the treatment day, the cells will be thawed, washed, mixed with virus, briefly centrifuged and incubated for 2 hours with virus prior to infusion of the virus/MSC cocktail into patients.

Systemic administration of human adipose-derived stem cells reverts nociceptive hypersensitivity in an experimental model of neuropathy

Over the last decade, it has been proved that mesenchymal stem cells (MSCs) elicit anti-inflammatory effects. MSCs from adipose tissue (hASCs) differentiate into cells of the mesodermal lineage and transdifferentiate into ectodermal-origin cells. Although there are various etiologies to chronic pain, one common feature is that painful states are associated with increased inflammation. We believe in hASCs as a therapeutic tool also in pathologies involving neuroinflammation and neuronal tissue damage. We have investigated the effect of hASCs injected in a model of neuropathic pain [(mouse sciatic nerve chronic constriction injury (CCI)]. hASCs from 5 donors were characterized, and no major differences were depicted. hASCs were cryopreserved and grown on demand. About 1×10(6), 3×10(6), and 6×10(6) hASCs were intravenously injected into normal immunocompetent mice. No mouse died, and no macroscopic toxicity or behavioral changes were observed, confirming the safety of hASCs. hASCs, intravenously (i.v.) injected into C57BL/6 mice when the neuropathic pain was already established, induced a significant reduction in mechanical allodynia and a complete reversion of thermal hyperalgesia in a dose-response fashion, already 1 day after administration. Moreover, the hASCs effect can be boosted by repeated administrations, allowing a prolonged therapeutic effect. Treatment decreased the level of the CCI-induced proinflammatory cytokine interleukin (IL)-1β and activated the anti-inflammatory cytokine IL-10 in the lesioned nerve. hASCs treatment also restored normal inducible nitric oxide synthase expression in the spinal cord of CCI animals. Our data suggest that hASCs are worthy of further studies as an anti-inflammatory therapy in the treatment of neuropathic pain or chronic inflammatory diseases.

Anti-inflammatory role and immunomodulation of mesenchymal stem cells in systemic joint diseases: potential for treatment

INTRODUCTION

Mesenchymal stem cells (MSCs) are multipotent stromal cells characterized by their ability to differentiate into adipocytes, chondrocytes, osteocytes and a number of other lineages. Investigation into their use has increased in recent years as characterization of their immunomodulatory properties has developed, and their role in the pathophysiology of joint disease has been suggested.

AREAS COVERED

MSCs demonstrate immunosuppressive functionality by suppressing T- and B-cell responses following activation by cytokines such as IL-6 and IL-1α. They also can be induced to exert pro-inflammatory effects in the presence of acute inflammatory environment due to the actions of TNF-α and IFN-γ. In inflammatory joint diseases such as rheumatoid arthritis, MSCs in bone marrow migrate to joints by a TNF-α-dependent mechanism and may be in part responsible for the disease process. MSCs have also been demonstrated in increased numbers in periarticular tissues in osteoarthritis, which may reflect an attempt at joint regeneration.

EXPERT OPINION

Clinical applications for MSCs have shown promise in a number of inflammatory and autoimmune disorders. Future work is likely to further reveal the immunosuppressive characteristics of MSCs, their role in the pathophysiology of joint diseases and provide the basis for new avenues for treatment.

Adipose-derived stromal/stem cells: a primer

Until recently, the complexity of adipose tissue and its physiological role was not well appreciated. This changed with the discovery of adipokines such as leptin. The cellular composition of adipose tissue is heterogeneous and changes as a function of diabetes and disease states such as diabetes. Tissue engineers view adipose tissue as a rich source of adult stromal/stem cells isolated by collagenase digestion. In vitro and in vivo studies have documented that adipose stromal/stem cells are multipotent, with the ability to differentiate along the adipocyte, chondrocyte, osteoblast and other lineage pathways. The adipose stromal/stem cells secrete a wide range of cytokines and growth factors with potential paracrine actions. Furthermore, adipose stromal/stem cells exert immunomodulatory functions when added to mixed lymphocyte reactions, suggesting that they can be transplanted allogeneically. This review article focuses on these mechanisms of adipose stromal/stem cell action and their potential utility as cellular therapeutics.

Mesenchymal stromal cells and regulatory T cells: the Yin and Yang of peripheral tolerance?

In recent years, mesenchymal stromal cells (MSCs) and regulatory T cells (Tregs) have both garnered significant interest from immunologists worldwide, not least because of the potential application of both cell types in the treatment of many chronic inflammatory and autoimmune diseases. Although both MSCs and Tregs can be considered immunosuppressive in their own right, the induction of Tregs by activated MSCs is now a well-publicised phenomenon; however, only recently have the mechanisms involved in this induction started to become clear. Indeed, it is becoming increasingly apparent that there exists a complex interplay between the two lineages leading to this potent inhibition of the host immune response. Cell contact, soluble mediators-including prostaglandin E(2) and transforming growth factor β-and indirect induction via manipulation of other antigen-presenting cells all appear to have vital roles in the interactions between MSCs and Tregs. Much still remains to be discovered before we have a full understanding of this important aspect of the immune response, but there have already been a multitude of clinical trials suggesting that MSC/Treg therapies could offer significant benefits in the treatment of both autoimmune disease and graft versus host disease. Although these therapies are still in their infancy, the synergy between MSCs and Tregs will undoubtedly yield future breakthroughs in the treatment of many debilitating conditions and usher in a new wave of targeted, cell-based therapeutics.

Advances in stem cell therapy for spinal cord injury

Spinal cord injury (SCI) is a devastating condition producing great personal and societal costs and for which there is no effective treatment. Stem cell transplantation is a promising therapeutic strategy, though much preclinical and clinical research work remains. Here, we briefly describe SCI epidemiology, pathophysiology, and experimental and clinical stem cell strategies. Research in stem cell biology and cell reprogramming is rapidly advancing, with the hope of moving stem cell therapy closer to helping people with SCI. We examine issues important for clinical translation and provide a commentary on recent developments, including termination of the first human embryonic stem cell transplantation trial in human SCI.

Neurorestoration induced by mesenchymal stem cells: potential therapeutic mechanisms for clinical trials

Stem cells are emerging as therapeutic candidates in a variety of diseases because of their multipotent capacities. Among these, mesenchymal stem cells (MSCs) derived from bone marrow, umbilical cord blood or adipose tissue, comprise a population of cells that exhibit extensive proliferative potential and retain the ability to differentiate into multiple tissue-specific lineage cells including osteoblasts, chondrocytes, and adipocytes. MSCs have also been shown to enhance neurological recovery, although the therapeutic effects seem to be derived from an indirect paracrine effect rather than direct cell replacement. MSCs secrete neurotrophic factors, promote endogenous neurogenesis and angiogenesis, encourage synaptic connection and remyelination of damaged axons, decrease apoptosis, and regulate inflammation primarily through paracrine actions. Accordingly, MSCs may prevail as a promising cell source for cell-based therapy in neurological diseases.

The preventive and therapeutic effects of intravenous human adipose-derived stem cells in Alzheimer's disease mice

Alzheimer's disease (AD) is characterized by the accumulation of amyloid plaques and neurofibrillary tangles accompanied by cognitive dysfunction. The aim of the present study was to elucidate preventive and therapeutic potential of stem cells for AD. Among stem cells, autologous human adipose-derived stem cells (hASCs) elicit no immune rejection responses, tumorigenesis, or ethical problems. We found that intravenously transplanted hASCs passed through the BBB and migrated into the brain. The learning, memory and pathology in an AD mouse model (Tg2576) mice greatly improved for at least 4 months after intravenous injection of hASC. The number of amyloid plaques and Aβ levels decreased significantly in the brains of hASC-injected Tg mice compared to those of Tg-sham mice. Here, we first report that intravenously or intracerebrally transplanted hASCs significantly rescues memory deficit and neuropathology, in the brains of Tg mice by up-regulating IL-10 and VEGF and be a possible use for the prevention and treatment of AD.

Potential role of stem cells in severe spinal cord injury: current perspectives and clinical data

Stem cell transplantation for spinal cord injury (SCI) along with new pharmacotherapy research offers the potential to restore function and ease the associated social and economic burden in the years ahead. Various sources of stem cells have been used in the treatment of SCI, but the most convincing results have been obtained with neural progenitor cells in preclinical models. Although the use of cell-based transplantation strategies for the repair of chronic SCI remains the long sought after holy grail, these approaches have been to date the most successful when applied in the subacute phase of injury. Application of cell-based strategies for the repair and regeneration of the chronically injured spinal cord will require a combinational strategy that may need to include approaches to overcome the effects of the glial scar, inhibitory molecules, and use of tissue engineering strategies to bridge the lesion. Nonetheless, cell transplantation strategies are promising, and it is anticipated that the Phase I clinical trials of some form of neural stem cell-based approach in SCI will commence very soon.

Human adipose-derived cells: an update on the transition to clinical translation

The pace of discovery involving adipose-derived cells continues to accelerate at both the preclinical and clinical translational levels. Adipose tissue is a source of freshly isolated, heterogeneous stromal vascular fraction cells and culture-expanded, adherent and relatively homogeneous adipose stromal/stem cells. Both populations display regenerative capacity in soft and hard tissue repair, ischemic insults and autoimmune diseases. While their major mechanism of action has been attributed to both direct lineage differentiation and/or paracrine factor release, current evidence favors a paracrine mechanism. Over 40 clinical trials using adipose-derived cells conducted in 15 countries have been registered with the NIH, the majority of which are Phase I or Phase I/II safety studies. This review focuses on the literature of the past 2 years in order to assess the status of clinical and preclinical studies on adipose-derived cell therapies for regenerative medicine.

Effect of an adipose-derived stem cell and nerve growth factor-incorporated hydrogel on recovery of erectile function in a rat model of cavernous nerve injury

Postprostatectomy erectile dysfunction (ED) is the major problem for patients with clinically localized prostate cancer. Recently, gene and stem cell-based therapy of the corpus cavernosum has been attempted for postprostatectomy ED, but those therapies are limited by rapid blood flow and disruption of the normal architecture of the corpus cavernosum. In this study, we attempted to regenerate the damaged cavernous nerve (CN), which is the main cause of ED. We investigated the effectiveness of human adipose-derived stem cell (hADSC) and nerve growth factor-incorporated hyaluronic acid-based hydrogel (NGF-hydrogel) application on the CN in a rat model of bilateral cavernous nerve crush injury. Four weeks after the operation, erectile function was assessed by detecting the intracavernous pressure (ICP)/arterial pressure level by CN electrostimulation. The ICP was significantly increased by application of hADSC with NGF-hydrogel compared to the other experimental groups. CN and penile tissue were collected for histological examination. PKH-26 labeled hADSC colocalized with beta III tubulin were shown in CN tissue sections. hADSC/NGF-hydrogel treatment prevented smooth muscle atrophy in the corpus cavernosum. In addition, the hADSC/NGF-hydrogel group showed increased endothelial nitric oxide synthase protein expression. This study suggests that application of hADSCs with NGF-hydrogel on the CN might be a promising treatment for postprostatectomy ED.

Tissue engineering for the oncologic urinary bladder

Urinary diversion after radical cystectomy in patients with bladder cancer normally takes the form of an ileal conduit or neobladder. However, such diversions are associated with a number of complications including increased risk of infection. A plausible alternative is the construction of a neobladder (or bladder tissue) in vitro using autologous cells harvested from the patient. Biomaterials can be used as a scaffold for naturally occurring regenerative stem cells to latch onto to regrow the bladder smooth muscle and epithelium. Such engineered tissues show great promise in urologic tissue regeneration, but are faced with a number of challenges. For example, the differentiation mesenchymal stem cells from various sources can be difficult and the smooth muscle cells formed do not precisely mimic the natural cells.

Explant culture: a simple, reproducible, efficient and economic technique for isolation of mesenchymal stromal cells from human adipose tissue and lipoaspirate

Adipose tissue has emerged as a preferred source of mesenchymal stem/stromal cells (MSC), due to its easy accessibility and high MSC content. The conventional method of isolation of adipose tissue-derived stromal cells (ASC) involves enzymatic digestion and centrifugation, which is a costly and time-consuming process. Mechanical stress during isolation, use of bacterial-derived products and potential contamination with endotoxins and xenoantigens are other disadvantages of this method. In this study, we propose explant culture as a simple and efficient process to isolate ASC from human adipose tissue. This technique can be used to reproducibly isolate ASC from fat tissue obtained by liposuction as well as surgical resection, and yields an enriched ASC population free from contaminating haematopoietic cells. We show that explanting adipose tissue results in a substantially higher yield of ASC at P0 per gram of initial fat tissue processed, as compared to that obtained by enzymatic digestion. We demonstrate that ASC isolated by explant culture are phenotypically and functionally equivalent to those obtained by enzymatic digestion. Further, the explant-derived ASC share the immune privileged status and immunosuppressive properties implicit to MSC, suggesting that they are competent to be tested and applied in allogeneic clinical settings. As explant culture is a simple, inexpensive and gentle method, it may be preferred over the enzymatic technique for obtaining adipose tissue-derived stem/stromal cells for tissue engineering and regenerative medicine, especially in cases of limited starting material.

Mesenchymal stem cell-based tumor-targeted gene therapy in gastrointestinal cancer

Mesenchymal stem (or stromal) cells (MSCs) are nonhematopoietic progenitor cells that can be obtained from bone marrow aspirates or adipose tissue, expanded and genetically modified in vitro, and then used for cancer therapeutic strategies in vivo. Here, we review available data regarding the application of MSC-based tumor-targeted therapy in gastrointestinal cancer, provide an overview of the general history of MSC-based gene therapy in cancer research, and discuss potential problems associated with the utility of MSC-based therapy such as biosafety, immunoprivilege, transfection methods, and distribution in the host.

Mesenchymal stem cell graft improves recovery after spinal cord injury in adult rats through neurotrophic and pro-angiogenic actions

Numerous strategies have been managed to improve functional recovery after spinal cord injury (SCI) but an optimal strategy doesn't exist yet. Actually, it is the complexity of the injured spinal cord pathophysiology that begets the multifactorial approaches assessed to favour tissue protection, axonal regrowth and functional recovery. In this context, it appears that mesenchymal stem cells (MSCs) could take an interesting part. The aim of this study is to graft MSCs after a spinal cord compression injury in adult rat to assess their effect on functional recovery and to highlight their mechanisms of action. We found that in intravenously grafted animals, MSCs induce, as early as 1 week after the graft, an improvement of their open field and grid navigation scores compared to control animals. At the histological analysis of their dissected spinal cord, no MSCs were found within the host despite their BrdU labelling performed before the graft, whatever the delay observed: 7, 14 or 21 days. However, a cytokine array performed on spinal cord extracts 3 days after MSC graft reveals a significant increase of NGF expression in the injured tissue. Also, a significant tissue sparing effect of MSC graft was observed. Finally, we also show that MSCs promote vascularisation, as the density of blood vessels within the lesioned area was higher in grafted rats. In conclusion, we bring here some new evidences that MSCs most likely act throughout their secretions and not via their own integration/differentiation within the host tissue.

Journey of mesenchymal stem cells for homing: strategies to enhance efficacy and safety of stem cell therapy

Human mesenchymal stem cells (MSCs) communicate with other cells in the human body and appear to "home" to areas of injury in response to signals of cellular damage, known as homing signals. This review of the state of current research on homing of MSCs suggests that favorable cellular conditions and the in vivo environment facilitate and are required for the migration of MSCs to the site of insult or injury in vivo. We review the current understanding of MSC migration and discuss strategies for enhancing both the environmental and cellular conditions that give rise to effective homing of MSCs. This may allow MSCs to quickly find and migrate to injured tissues, where they may best exert clinical benefits resulting from improved homing and the presence of increased numbers of MSCs.