A Promising Insight: The Potential Influence and Therapeutic Value of the Gut Microbiota in GI GVHD

Macrophages in graft-versus-host disease (GVHD): dual roles as therapeutic tools and targets

Graft-versus-host disease remains one of the most formidable barriers to the complete success of hematopoietic stem cell transplantation that has emerged as the curative approach for many hematopoietic malignancies because it affects quality of life and overall survival. Macrophages are among the important members of the immune system, which perform dual roles in GVHD as both therapeutic tools and targets. This review epitomizes the multifunctional role of macrophages in the pathophysiology of both acute and chronic GVHD. Macrophages play an important role in the early phase of GVHD because of their recruitment and infiltration into target organs. Furthermore, they polarize into two functionally different phenotypes, including M1 and M2. In the case of acute GVHD, most macrophages express the M1 phenotype characterized by the production of pro-inflammatory cytokines that contribute to tissue damage. In contrast, in chronic GVHD, macrophages tend toward the M2 phenotype associated with the repair of tissues and fibrosis. A critical balance among these phenotypes is central to the course and severity of GVHD. Further interactions of macrophages with other lymphocytes such as T cells, B cells, and fibroblast further determine the course of GVHD. Macrophage interaction associated with alloreactive T cells promotes inflammation. This is therefore important in inducing injuries of tissues during acute GVHD. Interaction of macrophages, B cell, fibroblast, and CD4+ T cells promotes fibrosis during chronic GVHD and, hence, the subsequent dysfunction of organs. These are some insights, while several challenges remain. First, the impact of the dominant cytokines in GVHD on the polarization of macrophages is incompletely characterized and sometimes controversial. Second, the development of targeted therapies able to modulate macrophage function without systemic side effects remains an area of ongoing investigation. Future directions involve the exploration of macrophage-targeted therapies, including small molecules, antibodies, and nanotechnology, which modulate macrophage behavior and improve patient outcomes. This underlines the fact that a profound understanding of the dual role of macrophages in GVHD is essential for developing new and more effective therapeutic strategies. Targeting macrophages might represent one avenue for decreasing the incidence and severity of GVHD and improving the success and safety of HSCT.

Case report: The case of T-cell acute lymphoblastic leukemia treated with chemotherapy followed by anti-CD7 CAR-T cells using retroviral vector

CD7-targeted chimeric antigen receptor-T (CAR-T) cell therapy has shown great promise in the treatment of relapsed/refractory T-cell acute lymphoblastic leukemia (T-ALL). In this study, we reported a case of a 34-year-old male patient with T-ALL who finally developed multi-line drug resistance and refractoriness after multiple lines of high-intensity chemotherapy. After physician evaluation, this patient received allogeneic hematopoietic stem cell transplantation (allo-HSCT). Then, The patient remained in complete remission (CR) for four months before a relapse with 26.64% chimerism rate, so he was treated with allogeneic anti-CD7 CAR-T cells after chemotherapy reducing the tumor burden. The CAR-T product was a novel anti-CD7 CAR-T based on retroviral vectors (RV). After infusion, the patient achieved CR within 1 month after anti-CD7 CAR-T infusion and the remission has been ongoing for 9 months to date. Cytokine release syndrome (CRS) 1 was experienced while no immune effector cell-associated neurotoxicity syndrome (ICANS) was found. In addition, CAR copy number peaked at 350, 758 copies/μg on day 6. This case report of clinical treatment of T-ALL with anti-CD7 CAR-T cells prepared using a retroviral vector without gene editing and combined with chemotherapy, which demonstrated that the RV-based anti-CD7 CAR-T cells had good therapeutic effect and high safety in triple-refractory T-ALL patients.

Causal Relationship Between Gut Microbiota and Leukemia: Future Perspectives

The gut microbiota plays a crucial role in maintaining homeostasis in the human gastrointestinal tract. Numerous studies have shown a strong association between the gut microbiota and the emergence and progression of various diseases. Leukemia is one of the most common hematologic malignancies. Although standardized protocols and expert consensus have been developed for routine diagnosis and treatment, limitations remain due to individual differences. Nevertheless, a large number of studies have established a link between the gut microbiota and leukemia, with disturbances in the gut microbiota directly or indirectly affecting the development of leukemia. However, the causal relationship between the two remains unclear, and studying and exploring the causal relationship may open up entirely new avenues and protocols for use in the prevention and/or treatment of leukemia, offering new insights into diagnosis and treatment. In this review, the intricate relationship between the gut microbiota and leukemia is explored in depth, including causal associations, metabolite effects, therapeutic applications, and complications. Based on the characteristics of the gut microbiota, the future applications and prospects of gut microbiota are discussed to provide useful information for clinical treatment of leukemia.

Multifaceted involvements of Paneth cells in various diseases within intestine and systemically

Serving as the guardians of small intestine, Paneth cells (PCs) play an important role in intestinal homeostasis maintenance. Although PCs uniquely exist in intestine under homeostasis, the dysfunction of PCs is involved in various diseases not only in intestine but also in extraintestinal organs, suggesting the systemic importance of PCs. The mechanisms under the participation of PCs in these diseases are multiple as well. The involvements of PCs are mostly characterized by limiting intestinal bacterial translocation in necrotizing enterocolitis, liver disease, acute pancreatitis and graft-vs-host disease. Risk genes in PCs render intestine susceptible to Crohn’s disease. In intestinal infection, different pathogens induce varied responses in PCs, and toll-like receptor ligands on bacterial surface trigger the degranulation of PCs. The increased level of bile acid dramatically impairs PCs in obesity. PCs can inhibit virus entry and promote intestinal regeneration to alleviate COVID-19. On the contrary, abundant IL-17A in PCs aggravates multi-organ injury in ischemia/reperfusion. The pro-angiogenic effect of PCs aggravates the severity of portal hypertension. Therapeutic strategies targeting PCs mainly include PC protection, PC-derived inflammatory cytokine elimination, and substituting AMP treatment. In this review, we discuss the influence and importance of Paneth cells in both intestinal and extraintestinal diseases as reported so far, as well as the potential therapeutic strategies targeting PCs.

Molecular regulation after mucosal injury and regeneration in ulcerative colitis

Ulcerative colitis (UC) is a chronic nonspecific inflammatory disease with a complex etiology. Intestinal mucosal injury is an important pathological change in individuals with UC. Leucine-rich repeat-containing G protein-coupled receptor 5 (LGR5+) intestinal stem cells (ISCs) exhibit self-renewal and high differentiation potential and play important roles in the repair of intestinal mucosal injury. Moreover, LGR5+ ISCs are intricately regulated by both the Wnt/β-catenin and Notch signaling pathways, which jointly maintain the function of LGR5+ ISCs. Combination therapy targeting multiple signaling pathways and transplantation of LGR5+ ISCs may lead to the development of new clinical therapies for UC.