Safety and Efficacy Endpoints for Mesenchymal Stromal Cell Therapy in Renal Transplant Recipients. J Immunol Res. 2015;2015:391797. [PMID: 26258149 PMCID: PMC4518147 DOI: 10.1155/2015/391797]

How to Make Sense out of 75,000 Mesenchymal Stromal Cell Publications?

Mesenchymal stromal cells have been the subject of an expanding number of studies over the past decades. Today, over 75,000 publications are available that shine light on the biological properties and therapeutic effects of these versatile cells in numerous pre-clinical models and early-phase clinical trials. The massive number of papers makes it hard for researchers to comprehend the whole field, and furthermore, they give the impression that mesenchymal stromal cells are wonder cells that are curative for any condition. It is becoming increasingly difficult to dissect how and for what conditions mesenchymal stromal cells exhibit true and reproducible therapeutic effects. This article tries to address the question how to make sense of 75,000, and still counting, publications on mesenchymal stromal cells.

Current advances of stem cell-based therapy for kidney diseases

Kidney diseases are a prevalent health problem around the world. Multidrug therapy used in the current routine treatment for kidney diseases can only delay disease progression. None of these drugs or treatments can reverse the progression to an end-stage of the disease. Therefore, it is crucial to explore novel therapeutics to improve patients’ quality of life and possibly cure, reverse, or alleviate the kidney disease. Stem cells have promising potentials as a form of regenerative medicine for kidney diseases due to their unlimited replication and their ability to differentiate into kidney cells in vitro. Mounting evidences from the administration of stem cells in an experimental kidney disease model suggested that stem cell-based therapy has therapeutic or renoprotective effects to attenuate kidney damage while improving the function and structure of both glomerular and tubular compartments. This review summarises the current stem cell-based therapeutic approaches to treat kidney diseases, including the various cell sources, animal models or in vitro studies. The challenges of progressing from proof-of-principle in the laboratory to widespread clinical application and the human clinical trial outcomes reported to date are also highlighted. The success of cell-based therapy could widen the scope of regenerative medicine in the future.

Mesenchymal Stem Cell-Derived Extracellular Vesicles to the Rescue of Renal Injury

Acute kidney injury (AKI) and chronic kidney disease (CKD) are rising in global prevalence and cause significant morbidity for patients. Current treatments are limited to slowing instead of stabilising or reversing disease progression. In this review, we describe mesenchymal stem cells (MSCs) and their constituents, extracellular vesicles (EVs) as being a novel therapeutic for CKD. MSC-derived EVs (MSC-EVs) are membrane-enclosed particles, including exosomes, which carry genetic information that mimics the phenotype of their cell of origin. MSC-EVs deliver their cargo of mRNA, miRNA, cytokines, and growth factors to target cells as a form of paracrine communication. This genetically reprograms pathophysiological pathways, which are upregulated in renal failure. Since the method of exosome preparation significantly affects the quality and function of MSC-exosomes, this review compares the methodologies for isolating exosomes from MSCs and their role in tissue regeneration. More specifically, it summarises the therapeutic efficacy of MSC-EVs in 60 preclinical animal models of AKI and CKD and the cargo of biomolecules they deliver. MSC-EVs promote tubular proliferation and angiogenesis, and inhibit apoptosis, oxidative stress, inflammation, the epithelial-to-mesenchymal transition, and fibrosis, to alleviate AKI and CKD. By reprogramming these pathophysiological pathways, MSC-EVs can slow or even reverse the progression of AKI to CKD, and therefore offer potential to transform clinical practice.

Allogenic Use of Human Placenta-Derived Stromal Cells as a Highly Active Subtype of Mesenchymal Stromal Cells for Cell-Based Therapies

The application of mesenchymal stromal cells (MSCs) from different sources, including bone marrow (BM, bmMSCs), adipose tissue (atMSCs), and human term placenta (hPSCs) has been proposed for various clinical purposes. Accumulated evidence suggests that the activity of the different MSCs is indirect and associated with paracrine release of pro-regenerative and anti-inflammatory factors. A major limitation of bmMSCs-based treatment for autologous application is the limited yield of cells harvested from BM and the invasiveness of the procedure. Similar effects of autologous and allogeneic MSCs isolated from various other tissues were reported. The easily available fresh human placenta seems to represent a preferred source for harvesting abundant numbers of human hPSCs for allogenic use. Cells derived from the neonate tissues of the placenta (f-hPSC) can undergo extended expansion with a low risk of senescence. The low expression of HLA class I and II on f-hPSCs reduces the risk of rejection in allogeneic or xenogeneic applications in normal immunocompetent hosts. The main advantage of hPSCs-based therapies seems to lie in the secretion of a wide range of pro-regenerative and anti-inflammatory factors. This renders hPSCs as a very competent cell for therapy in humans or animal models. This review summarizes the therapeutic potential of allogeneic applications of f-hPSCs, with reference to their indirect pro-regenerative and anti-inflammatory effects and discusses clinical feasibility studies.

Cellular therapies in organ transplantation

Cellular therapy is a promising tool for improving the outcome of organ transplantation. Various cell types with different immunoregulatory and regenerative properties may find application for specific transplant rejection or injury-related indications. The current era is crucial for the development of cellular therapies. Preclinical models have demonstrated the feasibility of efficacious cell therapy in transplantation, early clinical trials have shown safety of several of these therapies, and the first steps towards efficacy studies in humans have been made. In this review, we address the current state of the art of cellular therapies in clinical transplantation and discuss monitoring tools and endpoints for these studies.

Stem Cell-Derived Extracellular Vesicles and Kidney Regeneration

Extracellular vesicles (EVs) are membranous vesicles containing active proteins, lipids, and different types of genetic material such as miRNAs, mRNAs, and DNAs related to the characteristics of the originating cell. They possess a distinctive capacity to communicate over long distances. EVs have been involved in the modulation of several pathophysiological conditions and, more importantly, stem cell-derived EVs appear as a new promising therapeutic option. In fact, several reports provide convincing evidence of the regenerative potential of EVs released by stem cells and, in particular, mesenchymal stromal cells (MSCs) in different kidney injury models. Described mechanisms involve the reprogramming of injured cells, cell proliferation and angiogenesis, and inhibition of cell apoptosis and inflammation. Besides, the therapeutic use of MSC-EVs in clinical trials is under investigation. This review will focus on MSC-EV applications in preclinical models of acute and chronic renal damage including recent data on their use in kidney transplant conditioning. Moreover, ongoing clinical trials are described. Finally, new strategies to broaden and enhance EV therapeutic efficacy by engineering are discussed.

Mesenchymal stromal cells in clinical kidney transplantation: how tolerant can it be?

PURPOSE OF REVIEW

Progress in the improvement of short-term and long-term outcomes of kidney transplantation seems to have reached a plateau, partially due to consequences of very efficient, but nonspecific immunosuppressive drugs. In recent years, various forms of cell therapy, including the use of mesenchymal stromal cells, have been put forward as an alternative strategy for more defined therapy. It is thought that these therapies will not only allow controlled tapering of immunosuppressive medication, but might bring us also closer to the ambition of generating donor-specific immune regulation and tolerance.

RECENT FINDINGS

Different forms of alloimmunity, including direct, indirect and semi-direct alloantigen presentation have to be controlled before donor-specific immune regulation can be reached. Several mechanisms have been described how mesenchymal stromal cells can affect alloimmunity. Especially, the interaction with professional antigen presenting cells, like dendritic cells, is of critical importance.

SUMMARY

This review will discuss the current status of ongoing clinical trials with mesenchymal stromal cells in kidney transplantation and specifically concentrate on the possibilities and impossibilities of how these therapeutic strategies can contribute to control of the different forms of alloreactivity operation in organ transplantation.

Acute Rejection After Kidney Transplantation Associates With Circulating MicroRNAs and Vascular Injury

Supplemental digital content is available in the text.

Background

Acute rejection (AR) of kidney transplants is associated with the loss of endothelial integrity, microvascular rarefaction and, ultimately, graft dysfunction. Circulating angiogenic microRNAs (miRNAs) may serve as markers for microvascular injury. Here, we investigated the short- and long-term effects of AR after kidney transplantation on systemic vascular injury and the associated circulating miRNA profile.

Methods

Systemic vascular injury was determined by measuring capillary tortuosity and density within the oral mucosa as well as by assessing circulating levels of angiopoietin-2/angiopoietin-1 ratio, vascular endothelial growth factor and soluble thrombomodulin. After a pilot study, we selected 48 miRNAs to assess the AR- and microvascular injury associated circulating miRNAs.

Results

In stable transplant recipients (n = 25) and patients with AR (n = 13), which were also studied longitudinally (1, 6, and 12 months post-AR), we found an AR-associated increase in markers of systemic vascular injury, of which vascular endothelial growth factor and soluble thrombomodulin normalized within 1 year after AR. Of the 48 selected miRNAs, 8 were either decreased (miR-135a, miR-199a-3p, and miR-15a) or increased (miR-17, miR-140-3p, miR-130b, miR-122 and miR-192) in AR. Of these, miR-130b, miR-199a, and miR-192 associated with markers of vascular injury, whereas miR-140-3p, miR-130b, miR-122, and miR-192 normalized within 1 year after AR.

Conclusions

AR after kidney transplantation is characterized by systemic microvascular injury and associates with specific circulating miRNA levels.

Long-term safety of umbilical cord mesenchymal stem cells transplantation for systemic lupus erythematosus: a 6-year follow-up study

The aim of this study is to assess the long-term safety of allogeneic umbilical cord mesenchymal stem cells (UC MSCs) transplantation for patients with refractory systemic lupus erythematosus (SLE). Nine SLE patients, who were refractory to steroid and immunosuppressive drugs treatment and underwent MSCs transplantation in 2009, were enrolled. One million allogeneic UC MSCs per kilogram of body weight were infused intravenously at days 0 and 7. The possible adverse events, including immediately after MSCs infusions, as well as the long-term safety profiles were observed. Blood and urine routine test, liver function, electrocardiogram, chest radiography and serum levels of tumor markers, including alpha fetal protein (AFP), cancer embryo antigen (CEA), carbohydrate antigen 155 (CA155) and CA199, were assayed before and 1, 2, 4 and 6 years after MSCs transplantation. All the patients completed two times of MSCs infusions. One patient had mild dizzy and warm sensation 5 min after MSCs infusion, and the symptoms disappeared quickly. No other adverse event, including fluster, headache, nausea or vomit, was observed. There was no change in peripheral white blood cell count, red blood cell count and platelet number in these patients after followed up for 6 years. Liver functional analysis showed that serum alanine aminotransferase, glutamic-oxalacetic transaminase, total bilirubin and direct bilirubin remained in normal range after MSCs infusions. No newly onset abnormality was detected on electrocardiogram and chest radiography. Moreover, we found no rise of serum tumor markers, including AFP, CEA, CA125 and CA199, before and 6 years after MSCs infusions. Our long-term observational study demonstrated a good safety profile of allogeneic UC MSCs in SLE patients.

Thrombospondin-1 promotes mesenchymal stromal cell functions via TGFβ and in cooperation with PDGF

Mesenchymal stromal cells (MSC) are characterized by unique tropism for wounded tissues, high differentiating capacity, ability to induce tissue repair, and anti-inflammatory and immunoregulatory activities. This has generated interest in their therapeutic use in severe human conditions as well as in regenerative medicine and tissue engineering. Identification of factors involved in the regulation of MSC proliferation, migration and differentiation could provide insights into the pathophysiological regulation of MSC and be exploited to optimize clinical grade expansion protocols for therapeutic use. Here we identify thrombospondin-1 (TSP-1) as a major regulator of MSC. TSP-1 induced MSC proliferation. This effect was mediated by TSP-1-induced activation of endogenous TGFβ, as shown by the inhibitory effects of anti-TGFβ antibodies and by the lack of activity of TSP-2 - that does not activate TGFβ. Moreover, TSP-1 strongly potentiated the proliferative and migratory activity of PDGF on MSC. TSP-1 directly bound to PDGF, through a site located within the TSP-1 type III repeats, and protected the growth factor from degradation by MSC-derived proteases, hence increasing its stability and bioavailability. The studies presented here identify a more comprehensive picture of the pleiotropic effect of TSP-1 on MSC behavior, setting the basis for further studies aimed at investigating the possible use of PDGF and TSP-1 in the in vitro expansion of MSC for therapeutic applications.