Activation of Innate Immunity in Graft-versus-Host Disease: Implications for Novel Targets?

Cellular senescence marker p16INK4a and NFKB1 gene polymorphisms in lower gastro-intestinal acute graft versus host disease

BACKGROUND

Lower gastrointestinal (GI) graft versus host disease (GVHD) represents a severe complication in allogeneic hematopoietic stem cell transplant (HSCT) recipients with high rates of transplant-related mortality. Deregulated innate immunity reactions are the features of its pathogenesis. Cellular senescence has been considered a program of the innate immunity. We focused on lower GI GVHD from the perspective of cellular senescence.

OBJECTIVE

We analyzed the impact of p16^INK4a expression, a hallmark of cellular senescence, in intestinal biopsies of patients with lower GI GVHD symptoms and NFKB1 gene polymorphisms (rs3774937 C/T and rs3774959 A/G) on HSCT outcome.

STUDY DESIGN

Fifty-two single-center patients who presented with symptoms of lower GI GVHD were analyzed in a retrospective manner. Two SNPs located in the NFKB1 gene regions (rs3774937 C/T and rs3774959 A/G) were genotyped from the peripheral blood samples collected before the start of the conditioning. All patients underwent proctosigmoidoscopy with biopsy of the mucosa. The expression of p16^INK4a was analyzed in normal intestinal crypts and stroma.

RESULTS

Fifty-two patients (50% male) received HSCT for hematological diseases (acute leukemias in 67%) and developed lower GI symptoms. Patients with p16^INK4a expression in the intestinal stroma were in lower risk of developing histological grade 3-4 aGVHD (RR 0.18 [95% CI 0.05-0.65]; p = 0.009). The multivariate linear regression confirmed the independent effect of p16^INK4a expression on time of the lower GI aGVHD symptoms onset (Coef. 38.9 [95% CI 12.7-65.1]; p = 0.005). The NFKB1 rs3774937 CC and TT/TC genotype were present in 40 and 80% of patients with p16^INK4a expression, respectively (p = 0.04). The rs3774959 AA and GG/AG genotype were present among 43 and 82% of patients with p16^INK4a expression, respectively (p = 0.02). Expression of p16^INK4a was associated with no clinical variable but NFKB1 genotype.

CONCLUSIONS

Our results address possible new mechanisms that may lead to better understanding of HSCT-related immune complications. Cellular senescence may bring novel approaches in GVHD diagnostics and therapy.

Multi-faceted role of LRP1 in the immune system

Graft versus host disease (GVHD) represents the major complication after allogeneic hematopoietic stem cell transplantation (Allo-SCT). GVHD-prone patients rely on GVHD prophylaxis (e.g. methotrexate) and generalized anti-GVHD medical regimen (glucocorticoids). New anti-GVHD therapy strategies are being constantly explored, however there is an urgent need to improve current treatment, since GVHD-related mortality reaches 22% within 5 years in patients with chronic GVHD. This review is an attempt to describe a very well-known receptor in lipoprotein studies - the low-density lipoprotein receptor related protein 1 (LRP1) - in a new light, as a potential therapeutic target for GVHD prevention and treatment. Our preliminary studies demonstrated that LRP1 deletion in donor murine T cells results in significantly lower GVHD-related mortality in recipient mice with MHC (major histocompatibility complex) -mismatched HSCT. Given the importance of T cells in the development of GVHD, there is a significant gap in scientific literature regarding LRP1's role in T cell biology. Furthermore, there is limited research interest and publications on this classical receptor molecule in other immune cell types. Herein, we endeavor to summarize existing knowledge about LRP1's role in various immune cells to demonstrate the possibility of this receptor to serve as a novel target for anti-GVHD treatment.

Aggressive Cutaneous Squamous Cell Carcinomas Following Treatment for Graft-versus-Host Disease: A Case Report and Review of Risk Factors

A 19-year-old female with a history of pre-B cell acute lymphocytic leukemia (ALL) presented with two aggressive cutaneous squamous cell carcinomas (C-SCC) in the right hand. The patient was diagnosed with pre-B cell ALL at four years of age. She underwent chemotherapy with initial remission. However, recurrence of the pre-B cell ALL required an unrelated allogeneic cord hematopoietic stem cell transplant (alloHSCT). Post-transplant, the patient developed Graft-Versus-Host Disease (GVHD), which was treated with immunosuppressant therapy for six years until resolution. Fourteen years following the transplant, the patient developed a morbilliform drug eruption secondary to clindamycin. She consequently received prednisone treatment. During the treatment period, the patient developed a new ulcerated and tender nodule on the dorsal aspect of her right hand. Further histopathological biopsy confirmed the diagnosis of C-SCC, which required excision. Ten months following the excision, the patient developed an additional C-SCC nodule on the same right hand, separated by 2.6 cm from the prior C-SCC. She was referred for a ray resection procedure. This case illustrates a patient with multiple risk factors that may have contributed to the continued development of C-SCC. Such risk factors include: a prolonged course of immunosuppressant medications and voriconazole treatment. Additional research is needed to investigate the etiologies and risks of C-SCC development in patients who require a transplant and long-duration immunosuppressive therapy.

Mesenchymal stem cell exosome-derived miR-223 alleviates acute graft-versus-host disease via reducing the migration of donor T cells

Background

Mesenchymal stem cells (MSCs) have been utilized in treating acute graft-versus-host disease (aGvHD) as they show strong immunosuppressive capacity through the release of various mediators, including immunosuppressive molecules, growth factors, chemokines, and exosomes. MicroRNAs (miRNAs) derived from MSC exosomes (MSCs-Exo) play a critical role in the regulation of immune responses. However, the function of miRNAs in treating aGvHD remains unknown. Here, we performed expression profiling of exosome-miRNAs from human umbilical cord MSCs (huc-MSCs) and murine compact bone MSCs (mb-MSCs) to investigate their immunoregulation effects in aGvHD.

Methods

Huc-MSCs-Exo and mb-MSCs-Exo were isolated and constructed MSCs-Exo-derived miRNA expression profiling using high-throughput sequencing. High expression of miR-223 was identified in both kinds of MSCs-Exo by bioinformatics analysis and quantitative real-time PCR (qPCR). In vitro cell crawling assay, transmigration assay and adhesion assay were subsequently applied to investigate the regulation of miR-223 on T cells. MiR-223 target gene was analyzed by western blot, luciferase analysis, and qPCR. Moreover, murine aGvHD model was established by infusing splenocytes and bone marrow nuclear cells from C57BL/6j mice (H-2Kb) into BALB/c recipient mice (H-2Kd). For therapeutic effect, MSCs or miR-223 Agomir were injected via tail vein. The general conditions of the mice in each group were monitored. Hematoxylin-eosin (H&E) staining was used to detect pathological changes of mice spleen, liver, and intestine. Mechanistically, immunofluorescence and flow cytometry were used to evaluate donor T cell migration, and enzyme-linked immunosorbent assay (ELISA) was used to detect the expression of serum inflammatory cytokines IFN-γ, TNF-α, and IL-17.

Results

High-throughput sequencing revealed high expression of miR-223 in huc-MSCs-Exo and mb-MSCs-Exo. MiR-223 could restrain adhesion and migration of T cells by inhibiting ICAM-1 expression in mouse lymphatic endothelial cells. MiR-223Agomir infusion attenuated aGvHD clinical symptoms, reduced the donor T cell infiltration into the spleen, liver, and intestine, and decreased inflammatory cytokines IFN-γ, TNF-α, and IL-17.

Conclusion

MSCs-Exo-derived miR-223 could attenuate aGvHD in mice through decreasing donor T cell migration. Our results unveil a new role of MSCs-Exo containing miR-223 in the treatment of aGvHD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02159-2.

Resolution of acute intestinal graft-versus-host disease

Allogeneic transplantation of hematopoietic stem cells (allo-HCT) represents an increasingly employed therapeutic approach to potentially cure patients suffering from life-threatening malignant and autoimmune disorders. Despite its lifesaving potential, immune-mediated allo-reactivity inherent to the allogeneic transplantation can be observed within up to 50% of all allo-HCT patients regularly resulting in the manifestation of acute and/or chronic graft-versus-host disease (GvHD). Mechanistically, especially donor T cells are assumed to chiefly drive inflammation that can occur in virtually all organs, with the skin, liver, and gut representing as the most frequently affected anatomic sites. Especially in the presence of intestinal manifestations of GvHD, the risk that the disease takes a life-threatening, potentially fatal course is significantly increased. In the light of a rapid gain of knowledge in respect to decode innate and adaptive immunity related mechanisms as, e.g., cytokine networks, intracellular signaling pathways or environmental triggers as, e.g., the intestinal microbiota and the development of novel therapeutic approaches, detailed insight into endogenous mechanisms seeking to counterbalance the proinflammatory machinery or to proactively foster signals promoting the resolution of allo-driven intestinal inflammation is emerging. Here, we seek to highlight the key aspects of those mechanisms involved in and contributing to the resolution of GvHD-associated intestinal inflammation. Concomitantly, we would like to briefly outline and discuss promising future experimental targets suitable to be therapeutically employed to directionally deflect the tissue response from a proinflammatory to an inflammation-resolving type of intestinal GvHD after allo-HCT.

Toll-Like Receptor Stimulation by MicroRNAs in Acute Graft-vs.-Host Disease

Acute graft-vs.-host disease (aGVHD) is a frequent complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT), accounting for substantial morbidity and mortality associated with this treatment modality. The pathogenesis of aGVHD involves a complex cascade of humoral and cellular interactions in which donor T cells target HLA mismatched host tissues, causing tissue injury through secretion of pro-inflammatory cytokines and induction of direct cytotoxicity. Toll-like receptors (TLRs) are key components of the innate immune system that recognize endogenous danger-associated molecular patterns (DAMPs) and exogenous pathogen-associated molecular patterns (PAMPs). Patients receiving conditioning chemotherapy and/or whole-body irradiation prior to all-HSCT are prone to gastrointestinal damage and translocation of microbiota across compromised intestinal epithelium, resulting in release of PAMPs and DAMPs. These “danger signals” play critical roles in disease pathogenesis by both initiating and propagating aGVHD through dendritic cell maturation and alloreactive T cell responses. There are 10–15 TLRs identified in mammalian species, a subset of which recognize single-stranded RNA (ssRNA) and serve as a key component of viral immunity. Recently, ssRNAs other than those of viral origin have been investigated as potential ligands of TLRs. MicroRNAs (miRs) are short (19–24 nt) non-coding RNAs that play critical roles in a variety of diseases. While traditionally miRs post-translationally modulate gene expression, non-canonical functions such as regulating TLR stimulation by acting as TLR ligands have been described. Here, we review the role of TLRs in aGVHD pathogenesis, the function of miRs in TLR stimulation, and the recent literature describing miRs as TLR ligands in aGVHD.

Role of Toll-Like Receptor Signaling in the Pathogenesis of Graft-versus-Host Diseases

Graft-versus-host disease (GVHD) and infection are major complications after allogeneic hematopoietic stem cell transplantation (allo-HSCT) and the leading causes of morbidity and mortality in HSCT patients. Recent work has demonstrated that the two complications are interdependent. GVHD occurs when allo-reactive donor T lymphocytes are activated by major histocompatibility antigens or minor histocompatibility antigens on host antigen-presenting cells (APCs), with the eventual attack of recipient tissues or organs. Activation of APCs is important for the priming of GVHD and is mediated by innate immune signaling pathways. Current evidence indicates that intestinal microbes and innate pattern-recognition receptors (PRRs) on host APCs, including both Toll-like receptors (TLRs) and nucleotide oligomerization domain (NOD)-like receptors (NLRs), are involved in the pathogenesis of GVHD. Patients undergoing chemotherapy and/or total body irradiation before allo-HSCT are susceptible to aggravated gastrointestinal epithelial cell damage and the subsequent translocation of bacterial components, followed by the release of endogenous dangerous molecules, termed pathogen-associated molecular patterns (PAMPs), which then activate the PRRs on host APCs to trigger local or systemic inflammatory responses that modulate T cell allo-reactivity against host tissues, which is equivalent to GVHD. In other words, infection can, to some extent, accelerate the progression of GVHD. Therefore, the intestinal flora's PAMPs can interact with TLRs to activate and mature APCs, subsequently activate donor T cells with the release of pro-inflammatory cytokines, and eventually, induce GVHD. In the present article, we summarize the current perspectives on the understanding of different TLR signaling pathways and their involvement in the occurrence of GVHD.