Immunological Reconstitution after Autologous Hematopoietic Stem Cell Transplantation in Patients with Systemic Sclerosis: Relationship Between Clinical Benefits and Intensity of Immunosuppression

Cellular-Based Therapies in Systemic Sclerosis: From Hematopoietic Stem Cell Transplant to Innovative Approaches

Systemic sclerosis (SSc) is a systemic disease characterized by autoimmune responses, vasculopathy and tissue fibrosis. The pathogenic mechanisms involve a wide range of cells and soluble factors. The complexity of interactions leads to heterogeneous clinical features in terms of the extent, severity, and rate of progression of skin fibrosis and internal organ involvement. Available disease-modifying drugs have only modest effects on halting disease progression and may be associated with significant side effects. Therefore, cellular therapies have been developed aiming at the restoration of immunologic self-tolerance in order to provide durable remissions or to foster tissue regeneration. Currently, SSc is recommended as the 'standard indication' for autologous hematopoietic stem cell transplantation by the European Society for Blood and Marrow Transplantation. This review provides an overview on cellular therapies in SSc, from pre-clinical models to clinical applications, opening towards more advanced cellular therapies, such as mesenchymal stem cells, regulatory T cells and potentially CAR-T-cell therapies.

Reconstitution of the immune system and clinical correlates after stem cell transplantation for systemic sclerosis

Systemic sclerosis (SSc) is a chronic autoimmune disease that includes fibrosis, diffuse vasculopathy, inflammation, and autoimmunity. Autologous hematopoietic stem cell transplantation (auto-HSCT) is considered for patients with severe and progressive SSc. In recent decades, knowledge about patient management and clinical outcomes after auto-HSCT has significantly improved. Mechanistic studies have contributed to increasing the comprehension of how profound and long-lasting are the modifications to the immune system induced by transplantation. This review revisits the immune monitoring studies after auto-HSCT for SSc patients and how they relate to clinical outcomes. This understanding is essential to further improve clinical applications of auto-HSCT and enhance patient outcomes.

Pharmacologically Enhanced Regulatory Hematopoietic Stem Cells Revert Experimental Autoimmune Diabetes and Mitigate Other Autoimmune Disorders

Type 1 diabetes (T1D) is characterized by the loss of immune self-tolerance, resulting in an aberrant immune responses against self-tissue. A few therapeutics have been partially successful in reverting or slowing down T1D progression in patients, and the infusion of autologous hematopoietic stem cells (HSCs) is emerging as an option to be explored. In this study, we proposed to pharmacologically enhance by ex vivo modulation with small molecules the immunoregulatory and trafficking properties of HSCs to provide a safer and more efficacious treatment option for patients with T1D and other autoimmune disorders. A high-throughput targeted RNA sequencing screening strategy was used to identify a combination of small molecules (16,16-dimethyl PGE₂ and dexamethasone), which significantly upregulate key genes involved in trafficking (e.g., CXCR4) and immunoregulation (e.g., programmed death ligand 1). The pharmacologically enhanced, ex vivo-modulated HSCs (regulatory HSCs [HSC.Regs]) have strong trafficking properties to sites of inflammation in a mouse model of T1D, reverted autoimmune diabetes in NOD mice, and delayed experimental multiple sclerosis and rheumatoid arthritis in preclinical models. Mechanistically, HSC.Regs reduced lymphocytic infiltration of pancreatic β cells and inhibited the activity of autoreactive T cells. Moreover, when tested in clinically relevant in vitro autoimmune assays, HSC.Regs abrogated the autoimmune response. Ex vivo pharmacological modulation enhances the immunoregulatory and trafficking properties of HSCs, thus generating HSC.Regs, which mitigated autoimmune diabetes and other autoimmune disorders.

Autologous hematopoietic stem cell transplantation modifies specific aspects of systemic sclerosis-related microvasculopathy

Objective:

Autologous hematopoietic stem cell transplantation (AHSCT) is a therapeutic option for patients with severe and progressive systemic sclerosis (SSc). Here, we aimed to investigate how AHSCT affects the vasculopathy of SSc patients.

Methods:

Twenty-seven SSc patients were retrospectively assessed, before and after AHSCT, for vessel morphology (nailfold capillaroscopy), skin expression of endothelial markers and serum levels of markers of inflammation, angiogenesis and endothelial activation. Skin biopsies were analyzed by immunohistochemistry (IHC) for expression of CD31, VE-cadherin, E-selectin, angiopoietin-1 (Ang1), angiopoietin-2 (Ang2), Tie-2, vascular endothelial growth factor A (VEGFA), vascular endothelial growth factor receptor 2 (VEGFR2), and endothelin-1 before and 12 months post-AHSCT. Serum samples from SSc patients were assessed before and up to 36 months after AHSCT for IL-6, von Willebrand factor (vWF), CXC Motif Chemokine Ligand 8 (CXCL8), Endothelin-1, epidermal growth factor (EGF), VEGFA, Pentraxin-3, Intercellular Adhesion Molecule 1 (ICAM-1), E-selectin, P-selectin, Thrombomodulin and IL-18 levels, and compared to healthy control samples.

Results:

On nailfold capillaroscopy, the number of capillaries increased at 1 year, while giant capillaries decreased at 6 months and 1 year after AHSCT. In the skin biopsies, expression of E-selectin notably decreased and Ang1 increased after AHSCT. At baseline, all vascular markers evaluated in the serum were significantly higher in SSc patients when compared to healthy controls, except for ICAM-1. When compared at different time points after AHSCT, Thrombomodulin, Pentraxin-3, vWF, and IL-18 levels remained generally stable at high levels until 36 months after AHSCT.

Conclusion:

Our results suggest that AHSCT contributes to improvements of the vessel morphology and dermal microvasculopathy, but does not normalize elevated levels of serum vascular markers in SSc patients. Additional vascular therapeutic approaches might contribute to more effectively treat the endothelial injury.

Immune rebound associates with a favorable clinical response to autologous HSCT in systemic sclerosis patients

To evaluate the immunological mechanisms associated with clinical outcomes after autologous hematopoietic stem cell transplantation (AHSCT), focusing on regulatory T- (Treg) and B- (Breg) cell immune reconstitution, 31 systemic sclerosis (SSc) patients underwent simultaneous clinical and immunological evaluations over 36-month posttransplantation follow-up. Patients were retrospectively grouped into responders (n = 25) and nonresponders (n = 6), according to clinical response after AHSCT. Thymic function and B-cell neogenesis were respectively assessed by quantification of DNA excision circles generated during T- and B-cell receptor rearrangements. At the 1-year post-AHSCT evaluation of the total set of transplanted SSc patients, thymic rebound led to renewal of the immune system, with higher T-cell receptor (TCR) diversity, positive correlation between recent thymic emigrant and Treg counts, and higher expression of CTLA-4 and GITR on Tregs, when compared with pretransplant levels. In parallel, increased bone marrow output of newly generated naive B-cells, starting at 6 months after AHSCT, renovated the B-cell populations in peripheral blood. At 6 and 12 months after AHSCT, Bregs increased and produced higher interleukin-10 levels than before transplant. When the nonresponder patients were evaluated separately, Treg and Breg counts did not increase after AHSCT, and high TCR repertoire overlap between pre- and posttransplant periods indicated maintenance of underlying disease mechanisms. These data suggest that clinical improvement of SSc patients is related to increased counts of newly generated Tregs and Bregs after AHSCT as a result of coordinated thymic and bone marrow rebound.

Autologous Hematopoietic Stem Cell Transplantation for Autoimmune Diseases: From Mechanistic Insights to Biomarkers

Phase I/II clinical trials of autologous hematopoietic stem cell transplantation (AHSCT) have led to increased safety and efficacy of this therapy for severe and refractory autoimmune diseases (AD). Recent phase III randomized studies have demonstrated that AHSCT induces long-term disease remission in most patients without any further immunosuppression, with superior efficacy when compared to conventional treatments. Immune monitoring studies have revealed the regeneration of a self-tolerant T and B cell repertoire, enhancement of immune regulatory mechanisms, and changes toward an anti-inflammatory milieu in patients that are responsive to AHSCT. However, some patients reactivate the disease after transplantation due to reasons not yet completely understood. This scenario emphasizes that additional specific immunological interventions are still required to improve or sustain therapeutic efficacy of AHSCT in patients with AD. Here, we critically review the current knowledge about the operating immune mechanisms or established mechanistic biomarkers of AHSCT for AD. In addition, we suggest recommendations for future immune monitoring studies and biobanking to allow discovery and development of biomarkers. In our view, AHSCT for AD has entered a new era and researchers of this field should work to identify robust predictive, prognostic, treatment-response biomarkers and to establish new guidelines for immune monitoring studies and combined therapeutic interventions to further improve the AHSCT protocols and their therapeutic efficacy.

Hematopoietic stem cell therapy for autoimmune diseases - Clinical experience and mechanisms

With accumulating evidence and improved outcomes along with recognition that modern biological therapies are not universally effective, require chronic administration and have high acquisition costs, hematopoietic stem cell transplantation (HSCT) has become an emerging direction for cell therapy in autoimmune diseases (ADs). The goal of this therapy is to induce medication-free remissions by resetting the immune system into a naïve and self-tolerant state through eradication of the autoreactive immunologic memory and profound re-configuration of the immune system induced by the transplant procedure. Safety of HSCT has generally improved by implementing internal quality management and external accreditation. Inter-disciplinary guidelines for patient selection, transplant technique and supportive care along with greater center experience should optimize safe and appropriate delivery of HSCT in specific ADs. In this review, we discuss the current role and future perspectives of HSCT in AD, focusing on recent published clinical and scientific studies and recommendations in the field.

Efficacy and safety of autologous haematopoietic stem cell transplantation in systemic sclerosis: a systematic review of the literature

We aimed to assess the efficacy of autologous haematopoietic stem cell transplantation (HSCT) for skin sclerosis (SSc) and lung function in SSc. We performed a systematic literature review in the PubMed and Scopus databases from the earliest records to March 2016. We assessed study quality using the Cochrane tool for randomized studies, the Newcastle-Ottawa Scale for controlled cohort studies and an 18-item quality-appraisal checklist for case series. The primary outcome was the improvement of skin thickening using the modified Rodnan Skin Score (mRSS). The secondary outcome was efficacy on lung function, using diffusing capacity of the lungs for carbon monoxide and forced vital capacity (FVC). The safety of the procedure was evaluated. The literature search identified 431 citations. There were 38 studies involving a total of 344 patients who fulfilled our inclusion criteria. No meta-analysis was performed due to a high heterogeneity. There was a significant improvement in mRSS in the majority of the reports (P < 0·05), and the results were sustained for up to 8 years after autologous HSCT. The randomized studies and the four cohort studies each showed a slight but statistically significant improvement in FVC at 1 or 2 years. The treatment-related mortality calculated by pooling patients of 35 studies (336 patients with a follow-up up to 146 months) was 8·3% after autologous HSCT and 1% in cyclophosphamide-treated groups. Despite heterogeneity among the studies, we determined that autologous HSCT significantly improved cutaneous fibrosis and slightly improved FVC. Safety of autologous HSCT is acceptable given the severity of the disease. This systematic review was registered on PROSPERO, number CRD42016027951.

Autologous hematopoietic stem cell transplantation in systemic sclerosis: A reset to tolerance?

Autologous hematopoietic stem cell transplantation (ASCT) is an effective therapy for refractory autoimmune disease, in particular diffuse cutaneous systemic sclerosis (dcSSc). ASCT is the only treatment that can induce long term remission in dcSSc. However, the mechanism of action of ASCT has not yet been fully elucidated. The current hypothesis is that ASCT induces a long term 'reset' of the immune system, but there is no clear definition yet of such an immunological 'reset to tolerance', nor has it been established how to distinguish a 'reset' from long term immunosuppression. Here, we review the literature on immunological changes after ASCT in dcSSc patients to gain more insight whether changes in immunological parameters can help elucidate the mechanism of action of ASCT. We identified 12 studies. While some immunological parameters could be correlated to clinical response, heterogeneity in the studies, short follow-up time and the small sample sizes preclude firm conclusions. Importantly, most patients displayed a sustained clinical response despite the presence of auto-antibodies or higher-than-normal concentrations of cytokines and proteins associated with disease activity. This suggests that the mechanism of ASCT may not be solely immunological. Future research should focus on larger cohorts of patients and also take functional evaluation of immune cells into account in order to determine whether ASCT induces long term immunosuppression or resets the immune system to tolerance. Answering this question is key to further optimizing ASCT for dcSSc patients.

Resetting the immune response after autologous hematopoietic stem cell transplantation for autoimmune diseases

Autologous hematopoietic stem cell transplantation (AHSCT) is currently investigated as treatment for severe and refractory autoimmune diseases, such as multiple sclerosis (MS), systemic sclerosis (SSc), Crohn's disease (CD) and systemic lupus erythematosus. Randomized clinical trials in MS, SSc and CD have shown the efficacy of AHSCT to promote control of disease activity and progression, when compared to conventional treatment. The use of high dose immunosuppressive conditioning is essential to eliminate the autoimmune repertoire, and the re-infusion of autologous hematopoietic stem cells avoids long-term leucopenia by reconstitution of both immune and hematological systems. Recent studies showed that AHSCT is able to deplete the autoimmune compartment and further promote the formation of a new auto-tolerant immune repertoire, reducing the inflammatory milieu and leading to long-term clinical remission without any complementary post-graft treatment. Deep knowledge about the mechanisms of action related to AHSCT-induced remission is required for the management of possible post-AHSCT relapse and improvement of clinical protocols. This paper will review the mechanisms enrolled in the immune response resetting promoted by AHSCT in patients with autoimmune diseases.

Decreased expression of Runx1 and lowered proportion of Foxp3⁺ CD25⁺ CD4⁺ regulatory T cells in systemic sclerosis

OBJECTIVES

To investigate the role of Foxp3(+) CD25(+) CD4(+) regulatory T cells (Treg) and their transcription factor, Runt-related transcription factor 1 (Runx1), in the pathogenesis and development of systemic sclerosis (SSc).

METHODS

We collected 23 blood samples from patients with SSc including 19 females and 4 males, 11 early-stage cases within 3 years from onset and 12 late-stage cases and 22 samples from age-matched healthy subjects (HS). Total CD4(+) T cells were assessed for the expression of Treg-related markers, CD25 and CD127, on their surface and intracellular Foxp3 using flow cytometry. Relative expression of Runx1 mRNA in magnetically purified Treg was analyzed using real-time PCR.

RESULTS

Proportion of Foxp3(+) cells in total CD4(+) T cells was decreased in patients with either early- or late-stage SSc compared with that in HS, and Runx1 mRNA expression in purified Treg was lower in patients with SSc than in HS. Runx1 mRNA expression level was related to the frequency of Treg in SSc.

CONCLUSIONS

This is the first report on Runx1 expression in Treg of a human autoimmune disease. Low expression of Runx1 along with reduced proportion of Treg in CD4(+) T cells may be associated with development of SSc even in early disease.

Up-regulated expression of HLA-DRB5 transcripts and high frequency of the HLA-DRB5*01:05 allele in scleroderma patients with interstitial lung disease

OBJECTIVE

Interstitial lung disease (ILD) is a serious complication of SSc. We aimed to identify markers associated with SSc-related ILD.

METHODS

RNA was prepared from the peripheral blood mononuclear cells of 14 SSc patients, divided into four different RNA pools according to the presence or absence of ILD and to the treatment, and subjected to microarray analysis. Real-time quantitative PCR was used to confirm the microarray results in 43 SSc patients, 42 autoimmune controls and 10 healthy controls. Genomic DNA samples were collected from 149 patients with SSc (70 in Hokkaido and 79 in Tokyo) who underwent a high-resolution CT for the evaluation of ILD and from 230 healthy controls. Genotyping was performed using sequence-specific primers.

RESULTS

The microarray analysis revealed HLA-DRB5 to be the only gene commonly up-regulated in patients with ILD compared with those without ILD in both comparison groups. High expression levels of HLA-DRB5 in SSc patients with ILD were confirmed by real-time quantitative PCR. The prevalence of HLA-DRB5 gene carriers increased in the SSc patients with ILD relative to those without ILD or to healthy controls in both cohorts. Among the four detected alleles, the HLA-DRB5*01:05 allele was significantly more frequent in SSc patients with ILD than in SSc patients without ILD or in healthy controls. These associations were confirmed in the second cohort.

CONCLUSION

HLA-DRB5 was highly expressed in PBMCs from patients with SSc-related ILD. The HLA-DRB5*01:05 allele is a risk factor for ILD in patients with SSc.

Hematopoietic stem cell transplantation for systemic sclerosis: history and current status

PURPOSE OF REVIEW

Systemic sclerosis (SSc) remains one of the last severe autoimmune disease with a poor prognosis and modest response to immunosuppressive therapy. Mortality in severe diffuse disease with internal organ involvement is elevated. Autologous hematopoietic transplantation (HSCT) has emerged in the last decade as a promising disease-modifying treatment.

RECENT FINDINGS

In phase I/II trials, HSCT has demonstrated to induce impressive reversal of skin fibrosis, neoangiogenesis, improved functionality and quality of life, and stabilization of internal organ function. Treatment-related mortality was reduced over time by better pretransplant evaluation and by treating patients earlier in disease.

SUMMARY

Two out of three randomized trials of autologous HSCT for SSc have been concluded: the nonmyeloablative American Systemic Sclerosis Immune Suppression versus Transplant, and Autologous Stem cell Transplantation International Scleroderma. The myeloablative Scleroderma Cyclophosphamide versus Transplant instead is still recruiting patients. The soon expected results from these trials should clarify the role of autologous HSCT in the challenging management of severe SSc.

Targeting the CXCR4-CXCL12 axis mobilizes autologous hematopoietic stem cells and prolongs islet allograft survival via programmed death ligand 1

Antagonism of CXCR4 disrupts the interaction between the CXCR4 receptor on hematopoietic stem cells (HSCs) and the CXCL12 expressed by stromal cells in the bone marrow, which subsequently results in the shedding of HSCs to the periphery. Because of their profound immunomodulatory effects, HSCs have emerged as a promising therapeutic strategy for autoimmune disorders. We sought to investigate the immunomodulatory role of mobilized autologous HSCs, via target of the CXCR4-CXL12 axis, to promote engraftment of islet cell transplantation. Islets from BALB/c mice were transplanted beneath the kidney capsule of hyperglycemic C57BL/6 mice, and treatment of recipients with CXCR4 antagonist resulted in mobilization of HSCs and in prolongation of islet graft survival. Addition of rapamycin to anti-CXCR4 therapy further promoted HSC mobilization and islet allograft survival, inducing a robust and transferable host hyporesponsiveness, while administration of an ACK2 (anti-CD117) mAb halted CXCR4 antagonist-mediated HSC release and restored allograft rejection. Mobilized HSCs were shown to express high levels of the negative costimulatory molecule programmed death ligand 1 (PD-L1), and HSCs extracted from wild-type mice, but not from PD-L1 knockout mice, suppressed the in vitro alloimmune response. Moreover, HSC mobilization in PD-L1 knockout mice failed to prolong islet allograft survival. Targeting the CXCR4-CXCL12 axis thus mobilizes autologous HSCs and promotes long-term survival of islet allografts via a PD-L1-mediated mechanism.

Bone marrow stem cells in clinical application: harnessing paracrine roles and niche mechanisms

The being of any individual throughout life is a dynamic process relying on the capacity to retain processes of self-renewal and differentiation, both of which are hallmarks of stem cells. Although limited in the adult human organism, regeneration and repair do take place in virtue of the presence of adult stem cells. In the bone marrow, two major populations of stem cells govern the dynamic equilibrium of both hemopoiesis and skeletal homeostasis; the hematopoietic and the mesenchymal stem cells. Recent cell based clinical trials utilizing bone marrow-derived stem cells as therapeutic agents have revealed promising results, while others have failed to display as such. It is therefore imperative to strive to understand the mechanisms by which these cells function in vivo, how their properties can be maintained ex-vivo, and to explore further their recently highlighted immunomodulatory and trophic effects.

Treatment of systemic sclerosis: potential role for stem cell transplantation

Hematopoietic stem cell transplantation may "reset" the immune reconstitution and induce self tolerance of autoreactive lymphocytes, and has been explored in the treatments for systemic sclerosis. Phase I/II trials have shown a satisfactory risk benefit ratio. The true benefit will be identified by two ongoing prospective, randomized phase III trials. Multipotent mesenchymal stromal cells (MSCs) possess antiproliferative, anti-inflammatory, and immunosuppressive properties. The use of MSCs has showed successful responses in patients with severe steroid-resistant acute graft versus host disease in phase II trials, and may be a potentially promising option for patients with systemic sclerosis.