Extracellular Vesicles from Wharton's Jelly Mesenchymal Stem Cells Suppress CD4 Expressing T Cells Through Transforming Growth Factor Beta and Adenosine Signaling in a Canine Model

Functional proteins of mesenchymal stem cell-derived extracellular vesicles

Extracellular vesicles (EVs) contain proteins, microRNAs, mRNAs, long non-coding RNAs, and phospholipids, and are a novel mechanism of intercellular communication. It has been proposed that the immunomodulatory and regenerative effects of mesenchymal stem/stromal cells (MSCs) are mainly mediated by soluble paracrine factors and MSC-derived EVs (MSC-EVs). Recent studies suggest that MSC-EVs may serve as a novel and cell-free alternative to whole-cell therapies. The focus of this review is to discuss the functional proteins which facilitate the effects of MSC-EVs. The first section of the review discusses the general functions of EV proteins. Next, we describe the proteomics of MSC-EVs as compared with their parental cells. Then, the review presents the current knowledge that protein contents of MSC-EVs play an essential role in immunomodulation and treatment of various diseases. In summary, functional protein components are at least partially responsible for disease-modulating capacity of MSC-EVs.

Research Status of Mesenchymal Stem Cells in Liver Transplantation

Liver transplantation has been deemed the best choice for end-stage liver disease patients but immune rejection after surgery is still a serious problem. Patients have to take immunosuppressive drugs for a long time after liver transplantation, and this often leads to many side effects. Mesenchymal stem cells (MSCs) gradually became of interest to researchers because of their powerful immunomodulatory effects. In the past, a large number of in vitro and in vivo studies have demonstrated the great potential of MSCs for participation in posttransplant immunomodulation. In addition, MSCs also have properties that may potentially benefit patients undergoing liver transplantation. This article aims to provide an overview of the current understanding of the immunomodulation achieved by the application of MSCs in liver transplantation, to discuss the problems that may be encountered when using MSCs in clinical practice, and to describe some of the underlying capabilities of MSCs in liver transplantation. Cell–cell contact, soluble molecules, and exosomes have been suggested to be critical approaches to MSCs’ immunoregulation in vitro; however, the exact mechanism, especially in vivo, is still unclear. In recent years, the clinical safety of MSCs has been proven by a series of clinical trials. The obstacles to the clinical application of MSCs are decreasing, but large sample clinical trials involving MSCs are still needed to further study their clinical effects.

B Lymphocytes Are the Target of Mesenchymal Stem Cells Immunoregulatory Effect in a Murine Graft-versus-Host Disease Model

There is growing clinical interest in the utilization of mesenchymal stem cells (MSCs) in the management of acute graft-versus-host disease (aGvHD), yet the effect of major histocompatibility complexes (MHCs) on B lymphocytes in this process has been less well documented. Working in an MHC fully mismatched murine aGvHD model, we found that MSC co-transfer significantly prolonged the survival time of the recipients. More interestingly, analysis on immunophenotypic profiles of posttransplant splenocytes showed that surface expression of CD69 (an early activation marker) and CD86 (a costimulatory molecule) was suppressed predominantly on donor derived B lymphocytes by MSC infusion. Additionally, mRNA level of interleukin-4, a potent B lymphocyte stimulator, was strikingly reduced from MSC-treated mice, while interleukin-10, the regulatory B lymphocytes inductor, was increased; these may underlie the lesser activation of B lymphocytes. In consistence, depletion of B lymphocytes in the transfusion inoculum further prolonged the survival time of aGvHD mice regardless of MSC administration. Therefore, B lymphocytes played an important role in the development of aGvHD, and they are targets in MSC-regulated immune response cascade in vivo. This study may provide a mechanistic clue for the treatment of human clinical aGvHD.

Novel insights into MSC-EVs therapy for immune diseases

Mesenchymal stromal cells (MSC) are a heterogeneous cell population with self-renewal and the ability to differentiate into different lineages. The novel regulatory role of MSC in both adaptive and innate immune responses got extensive investigation and MSC have been widely used in clinical trials as immunosuppressive agents for autoimmune and inflammatory diseases, including graft-versus-host disease (GVHD), multiple sclerosis (MS), systemic lupus erythematosus (SLE), chronic kidney disease, etc. Recent studies have found that MSC exerted their immunomodulation function through secreting extracellular vesicles (EVs), which delivered parent cell cargo to recipient cells without oncogenicity or variability. Since MSC-EVs exhibit most of the properties of MSC and take advantage of their cellular immunomodulatory fuction, MSC-EVs appear to a promising none-cell therapy in various human diseases. In this review, we summarize the pivotal roles of MSC-EVs as agents for immunotherapy in diseases.