Mesenchymal Stem Cells Infusion in Patients With Autoimmune Diseases

The autoimmune disorders are a spectrum of diseases ranging from organ-specific, in which antibodies and T cells react to self-antigens localized in a specific tissue, to systemic, which are characterized by reactivity against a specific antigen(s) spread throughout various tissues in the body. The incidence of different autoimmune diseases is variable, according to the Centers for Disease Control and Prevention, 22.7% have rheumatic diseases. Although no population-based epidemiological study has been carried out in Pakistan purely on autoimmune diseases; a study by Mohsin Z et al. reports the combined prevalence of rheumatic diseases at a tertiary hospital in Karachi to be 17.3%. Autoimmune diseases and their treatment modalities are the prime cause of disability in developing countries and have the highest incapacitating rates in health-related quality of life (HRQoL) and daily functioning. The 21st century has seen rapid advances in the treatment of diseases of immune dysfunction. One such treatment modality is stem cell therapy which is believed to repair and regenerate tissues. In particular, mesenchymal stem cells (MSCs) have been applied to treat diseases associated with age, changing lifestyle, immune dysfunction and stroke. MSC therapy has promise to treat various autoimmune disorders like refractory systemic lupus erythematosus (SLE), Crohn's disease, systemic sclerosis (SS), rheumatoid arthritis (RA), multiple sclerosis (MS), graft versus host disease, diabetes mellitus, thyroiditis and even different types of neurological disorders. At present, nearly a thousand clinical trials have used MSC-based therapies. Among those around one hundred trials have been conducted for treatment of immune-mediated disorders, the first one being more than fifteen years ago (table 1). The interest surrounding field of MSCs was initially based on their inherent capacity for self-renewal and regeneration with a potential to form cells of mesodermal origin (adipocytes, osteocytes, chondrocytes, hepatocytes, neurons, muscle cells and epithelial cells) depending on the surrounding microenvironment. Later on, due to their abilities to home to inflamed areas and exert immunomodulatory effects, therapies with MSCs extended to treatment of autoimmune and chronic inflammatory processes. Multiple studies have also demonstrated that MSCs have intrinsic immunomodulatory and anti-inflammatory properties. Table 1: Clinical trials in which mesenchymal stem cells are being used as therapeutic modality. Immune mediated disorder Number of Clinical trials Year of first Clinical trial Reference Graft vs. host disease 49 2004 Inflammatory bowel disease 23 2006 Multiple sclerosis 29 2006 Systemic lupus erythematosus 10 2007 Type I diabetes 26 2008 Primary Sjögren syndrome 1 2009 Type II diabetes 13 2010 Autoimmune hepatitis 2 2011 Ankylosing spondylitis 2 2011 Chronic urticarial 1 2017 Refractory autoimmune thrombocytopenia 1 2019 Source of MSCs MSCs were initially identified in the BM and are commonly isolated by gradient centrifugation to separate nucleated cells, followed by in vitro culture and serial passages. The Mesenchymal and Tissue Stem Cell Committee of the International Society for Cellular Therapy (ISCT) has designated the term 'multipotent mesenchymal stromal cells' for the plastic-adherent cells found under standard culture conditions. The immunophenotype of these cells as per ISCT criteria is positive for cell-surface markers CD73, CD90 and CD105 and negative for surface CD14 or CD11b, CD45, CD34, CD79 or CD19, and HLA-DR. MSCs have also been obtained from adipose tissue, placenta, amniotic fluid, umbilical cord blood (UCB), connective tissues of skeletal muscle and dermis,dental tissue, and fetal tissues such as lung and blood. Mobilized peripheral blood cells have also been reported as a source of MScs. Although gene expression studies demonstrate that MSC populations obtained from different tissue sources are highly heterogeneous, their ability to renew, differentiate, and major functional properties, such as regulation of immunological tolerance, wound healing, inflammation and fibrosis, are common to all MSCs. 1. Effects on cells of immune system MSCs suppress T-cell proliferation induced by alloantigens or mitogens via increasing the number of regulatory T cells and lessen complications of GVHD after HSCT and immune-mediated disease. In addition, MSCs inhibit function of B cells, natural killer cells and dendritic cells. The main immunosuppressive function of MSCs is by production of induced soluble factors; however, these cells can also exert immunosuppressive effects by direct cell-to-cell interaction. The immunosuppressive capacity of MSCs is enhanced under inflammatory conditions in the presence of the proinflammatory cytokines interferon (IFN)-g, tumor necrosis factor-alpha and interleukin (IL)-6.Under immunologically quiescent conditions, MSCs promote T-cell survival and can induce the activation and proliferation of CD4 positive regulatory T cells. 2. Production of immunomodulatory soluble factors MSCs constitutively produce inducible soluble factors, like transforming growth factor-β (TGF-β), hepatocyte growth factor, nitric oxide, HLA-G59 and indoleamine 2,3-dioxygenase that mediate their effects. Large amounts of IL-6 andIL-8, and the chemokine CCL-2 are also produced. MSCs treated with IFN-γ, secrete ICAM-1, CXCL-10 and CCL-8, whereas IL-8 production is decreased. This phenomenon suggests that MSCs target neutrophils and monocytes under non-inflammatory conditions, but attract monocytes, dendritic cells, T cells and natural killer cells under inflammatory conditions. A number of studies reported TGF-βas a key mediator of immunomodulation by MSCs. 3. Proinflammatory "licensing" of MSCs MSCs have been dubbed as ''smart" immune modulators since their suppressive effects require a previous licensing step that occurs in the presence of an inflammatory environment. If MSCs are transplanted during acute inflammation, the microenvironment containing polarized M1 macrophages 'licenses' MSCs to inhibit effector T, B, natural killer and dendritic cells. In contrast, if MSCs are licensed after the polarization of M2 macrophages by Th2-type cytokines as occurs during chronic inflammation, the microenvironment provides alternative licensing and recruits MSCs to the fibrosis process. 4. MSC paracrine factors in the repair mechanism Cellular regeneration of an ischemic tissue necessitates massive cell supply, on the order of a billion for an infarcted heart, for example. Experimental studies and clinical trials have revealed that MSC-mediated therapeutic benefit might largely rely on the contribution of the secreted amounts of growth factors and cytokines rather than on their potential for differentiation into cardiomyocytes, vascular or renal cells as shown by previous study. The panel of regulatory and trophic factors secreted by MSCs include a large number of growth factors, cytokines and chemokines. Translation of MSC knowledge into clinical application Cell therapy indeed appears to be an applicable translational strategy for autoimmune diseases. 1. Graft versus Host Disease (GVHD) In humans, the most studied application for MSCs is GVHD, a complication of hematopoietic stem cell transplantation. In 2004, a 9-year-old boy with severe treatment-resistant acute GVHD of the gut and liver was treated with third-party haploidentical mother-derived MSCs. Phase II clinical trials in patients with steroid-resistant severe acute GVHD showed a 70% initial response rate that was not related to age or HLA match. However, durable complete responses or other primary endpoints in these trials are still lacking. 2. Crohn´s Disease (CD) The first report of a phase I clinical trial of cell therapy using autologous adipose-derived MSCs in CD was published in 2005. Local injection led to healing of fistulas (6/8) with no adverse effects These results were confirmed by the same group in 2009 in a phase II multicenter in a randomized controlled trial \[24\]. Currently, there is a phase III, multicenter, placebo-controlled, randomized and blind study to evaluate the safety and efficacy of allogeneic BM-MSCs, conducted by Osiris Therapeutics. (http://www.clinicaltrials. gov/ct2/show/NCT00482092). 3. Multiple Sclerosis (MS) Phase I/II studies in patients with refractory MS has confirmed the absence of adverse effects during follow-up (6-28 months). An increase in the proportion of CD4+CD25+ regulatory T cells with decreased proliferative responses of lymphocytes and activation markers on dendritic cells was detected hours after MSC transplantation. Patients improved on measures of visual function, without evidence of significant adverse events. Progression of general disability was also reduced after treatment. 4. Systemic Lupus Erythematosus (SLE) Perhaps the most remarkable results of human MSC therapy emerge now from clinical trials aimed at severe, treatment refractory SLE. Patients with active disease and lupus nephritis that was unresponsive to monthly i.v. cyclophosphamide and oral prednisone (≥ 20 mg/day) have shown improved outcomes when treated with MSCs. The Disease Activity Index (SLEDAI) in these patients improved significantly at one, six and twelve months follow-up, as did urinary protein. In some of the trials, patients with high SLEDAI received one infusion of allogeneic BM-MSCs from passage 3-5 from non HLA matched healthy family members. Their follow-up has reached a median of 17.2 (3-36) months, with no adverse effects, deaths or ensuing GVHD. Quite surprisingly, 24 h proteinuria decreased significantly as early as one week after MSC therapy, even preceding changes in anti-dsDNA antibodies, which decreased significantly at one month and three months post MSC dose. T regulatory (Treg) cells, found to be quantitatively and qualitatively deficient in active SLE, were restored at week one as judged by the percentage of CD4+ Foxp3+ cells among peripheral blood mononuclear cells. Other trials although with shorter follow-up also demonstrate significant improvement, verified for SLEDAI score, serum albumin, 24 h urinary protein, serum creatinine, serum complement and anti-dsDNA antibodies. Undoubtedly MSC therapy must be further explored in SLE. 5. Systemic Sclerosis (SS) SS is an immune mediated disease with a prominent vascular and microvascular component often leading to ischemic complications. Since MSCs can differentiate to endothelial cells in vitro and also participate in blood vessel formation in adult tissues, therapy both with autologous and haploidentical third party donor MSCs has been reported, leading to striking improvement in two separate case reports. 6. Rheumatoid Arthritis (RA) Literature search reveals that more than a hundred preclinical studies on RA animal model and nine clinical trials on human patients have been completed on use of MSC-based therapy in RA and establish its safety and efficacy. Whereas, nine clinical trials are still ongoing. In two-thirds of these patients a single dose of allogeneic MSCs at about a dose between 1-10 x106/kg were used. It is believed that MSCs targets the pathogenic memory T cells and halt the progression of disease course in RA patients. 7. Polymyositis/Dermatomyositis (PM/DM) Polymyositis/dermatomyositis (PM/DM) is an autoimmune disease characterized by weakness of proximal skeletal muscles and obvious skin manifestations, and is known to affect multiple organs, such as muscles, lungs, and kidneys. Currently, the etiology is not known. Several studies have suggested that T helper (Th) cells are involved in the pathogenesis of PM/DM, since Th cell-related cellular dysfunction plays an important role in the occurrence and development of PM or DM. Therefore, MSCT could provide a new therapeutic strategy for the treatment of PM and DM. Several studies have demonstrated that this approach has promising clinical outcomes. In another study 32 PM and DM patients were injected intravenously with 1 × 106/kg MSCs. The results of the 9-year follow-up study demonstrated that the symptoms and serological indicators of patients improved, showing the effectiveness and safety of MSCT in PM and DM, while 11 patients died due to reasons not related to transplantation. In another study, 81 patients with PM/DM were randomly divided into two groups: 44 patients in the control group were individually treated with glucocorticoids and immunosuppressants for 6 months, while 37 patients in the transplantation group were injected intravenously with 3.5-5.2 × 107 UC-MSCs. The results of that study showed that the creatine kinase values in both groups were significantly decreased; however, the transplantation group had better results than the control group at several time points, and the lung function was significantly improved in the transplantation group. One patient died after transplantation and no transplantation-related complications occurred. Currently, there are only a few studies investigating PM/DM, and large-scale and randomized clinical studies are needed to evaluate the long-term effectiveness and safety of MSCT in PM/DM patients, including the risks of tumors and infections, as well as the optimal transplantation dose and schedule. Since the clinical outcome in case reports and phase I-II trials seem occasionally striking, there exists a dire need to perform structured and preferably controlled multicenter trials and document results in our own population.