Mesenchymal Stem Cell Transfusion for the Treatment of Refractory Lupus Nephritis

Systemic lupus erythematosus (SLE) is an autoimmune disease in which the immune system loses its immune tolerance to endogenous nuclear substances due to unknown reasons. The incidence and prevalence of SLE in different ethnic groups are different, and the overall incidence and prevalence are about 1.4-8.6/100,000 person-years and 13-366.6/100,000 person, respectively. The incidence and prevalence of SLE in China are about 4-10/100,000 person-years and 97.5-100/100,000 person, respectively. Based on this, it is estimated that there are about 1 million patients with SLE in China, which is a major serious chronic disease. Among patients with systemic lupus erythematosus (SLE), the reported lifetime incidence of lupus nephritis (LN) is 20%-60%, depending on the demographics of the population studied. Kidney involvement in SLE has been associated with higher mortality, especially for patients progressing to kidney failure. The ultimate goal of treating LN is to preserve kidney function and reduce the morbidity and mortality associated with chronic kidney disease (CKD) and kidney failure, while minimizing medication-associated toxicities.

At present, the pathogenesis of LN remains unclear. A genome-wide association study (GWAS) conducted by investigators team found that 9 single nucleotide polymorphism loci were associated with the occurrence of LN. The interaction of multiple factors such as gene polymorphism, viral infection, estrogen, ultraviolet light and smoking leads to increased production and decreased clearance of endogenous nuclear substances inside and outside the kidneys in the body, which induce the imbalance of regulation of innate immune system and adaptive immune system, especially the generation of more long-lived plasma cells, resulting in continuous production of autoantibodies in kidney, and they did not respond to standard immunosuppressive therapy. Deposition of antigen-antibody complexes in all parts of the kidneys, which triggers an inflammatory cascade that includes complement activation and aggregation of various immune cells such as T cells, B cells, dendritic cells (DCs), and macrophages. Many of them have pro-inflammatory phenotypes. These factors eventually put the kidneys in a storm of proinflammation.

The clinical manifestations of LN vary from asymptomatic to nephrotic syndrome, acute nephritis syndrome and chronic nephritis syndrome, but the severity of clinical manifestations does not match the actual pathological involvement of the kidneys. The 2024 EULAR Guideline and the 2024 KDIGO guideline recommend the use of kidney biopsy results as the basis for standard diagnosis and treatment of LN. Currently, according to the 2016 revised International Society of Nephrology/Renal Pathology Society (ISN/RPS) classification system, the pathological manifestations of LN are divided into 6 types (I-VI).

Active LN (National Institutes of Health (NIH) activity index≥1 with or without chronicity index) of Class III, IV or III+V, or IV+V are the focus of clinical treatment. The rationale for classifying LN into different classes is based on differences in the prognosis. Patients with proliferative LN (class III/IV) present the worst prognosis without treatment, and the higher rate of refractory response, and patients with class III, IV, or V LN, but not class I or II LN, are at immediate risk of CKD progression and involve irreversible nephron loss that reduces kidneys lifespan. Immunosuppressive therapy is mostly used for the treatment of class III and class IV and combined with or without class V LN, which is divided into two phases: an induction phase with intensive immunosuppression, usually lasting 3-6 months; and a maintenance phase of prolonged, less intensive treatment to prevent renal flares. The recommended standard first-line treatment for these lesions is as follows: initially with glucocorticoids combined with one of the following options: Calcineurin inhibitors (Voclosporin/Tacrolimus/cyclosporine); Mycophenolic acid analogs (MPAA); Cyclophosphamide; Belimumab+MPAA or reduced-dose cyclophosphamide. The maintenance phase of treatment mainly includes reducing prednisone to \<5 mg/d, and combined with mycophenolate mofetil. The treatment efficacy indicators include the following: complete response, partial response, and no kidney response. However, the complete response rate of LN is only 20%-30% after receiving six months of standard treatment, which is far from satisfactory. Refractory lupus nephritis indicates an inadequate response to lupus nephritis therapy. At present, there is no clear definition for refractory cases, which is defined in 2024 KDIGO Guidelines as no kidney response within initial first-line standard treatment.

In recent years, in addition to the first-line standard treatment regimen of glucocorticoid combined with immunosuppressants. More and more biological agents are being developed, including Rituximab, Ocrelizumab, Caplacizumab, Belimumab, Abatacept, Anifrolumab, APL-2, BI 655064, BMS-986165, Iscalimab, Obinutuzumab, etc. With the exception of Belimumab and Rituximab were recommended for the treatment of some patients especially those in refractory cases, most of these drugs are being studied in clinical trials. However, the clinical data of the current treatment are too few, the long-term treatment effects of these drugs are not exact, and more new treatment options are urgently needed.

Mesenchymal stem cells (MSCs) are a class of pluripotent stem cells, that are derived from early-developing mesoderm tissues and can be extracted from bone marrow, umbilical cord, umbilical cord blood, embryo, adipose tissue, and other tissues. More and more studies suggest that MSCs can secrete hundreds of cytokines, chemokines, and signaling molecules involved in immune regulation, and anti-inflammatory and anti-fibrosis processes, so they have been actively explored for the treatment of autoimmune diseases in recent years. The immunomodulatory mechanisms of MSCs have been studied using in vitro and in vivo experimental animal models of many autoimmune disorders. Our previous studies have also shown that MSC can effectively alleviate renal lesions in lupus nephritis mice by regulating the kidney region immunity, especially reduce the number of long-lived plasma cells and decrease the level of autoantibodies secreted locally in the kidney tissue.

At present, more than ten clinical trials of stem cell therapy for LN have been registered on the ClinicalTrial website, and among these two trial results have been published. However, the results of the two clinical trials were inconsistent.

Human Umbilical Cord-Mesenchymal Stem Cells (uc-MSCs) were derived from umbilical cord Wharton jelly, which are non-invasive acquisition, non-ethical controversy, easy sampling and extraction, low immunogenicity, easy in vitro expansion, and have a stronger immunomodulatory function and stronger proliferation ability compared with other MSCs.

Given that the results of the published clinical studies so far are inconsistent and the outcome indicators of these clinical trials were not confirmed by the pathological results of kidney biopsy, investigators prompted to design a patient-blinded, randomized, placebo-controlled, parallel-design clinical trial (RCT) to test the safety and efficacy of MSC therapy for refractory lupus nephritis.