Muscle and Muscle-like Autoantigen Expression in Myasthenia Gravis Thymus: Possible Molecular Hint for Autosensitization

Effect of thymectomy on the frequencies of peripheral regulatory B and T lymphocytes in patients with Myasthenia gravis-a pilot study

AIM

We aimed to investigate the relationship between the peripheral lymphocyte subset frequency and thymectomy in patients with myasthenia gravis (MG).

MATERIALS AND METHODS

The frequencies of regulatory B (Breg) and regulatory T (Treg) cells in peripheral blood samples obtained from 69 patients with MG and 10 healthy controls were analyzed using flow cytometry. Serum acetylcholine receptor antibodies (AchR-Ab) were measured. Patients with MG were subdivided into pre-thymectomy, post-thymectomy, and normal thymus control group.

RESULTS

The percentage of Breg cells was significantly decreased in both the pre-thymectomy (7.92 ± 1.30%) and post-thymectomy (8.14 ± 1.34%) groups compared to healthy controls (16.02 ± 2.78%) and reduced in the exacerbation and relapse phase compared to the stable maintenance stage. The proportion of cluster of differentiation (CD) 4 + CD25 + T cells and CD4 + CD25 + CD127low/- Treg cells in MG patients were not significantly different than healthy controls. AchR-Ab titers in aggravating or recurrence patients after thymectomy were significantly higher than that of the stable remission patients (11.13 ± 0.70 and 6.03 ± 0.85 nmol/L, respectively; p < 0.001).

CONCLUSION

The frequency of Breg cells may serve as a potential indicator of MG prognosis, while Treg cell frequency did not demonstrate the same prognostic ability. The concentration of AchR-Ab can be used as a dynamic monitoring index of disease severity in patients with MG.

Non-Coding RNAs in Myasthenia Gravis: From Immune Regulation to Personalized Medicine

Myasthenia gravis (MG) is an antibody-mediated autoimmune disorder characterized by altered neuromuscular transmission, which causes weakness and fatigability in the skeletal muscles. The etiology of MG is complex, being associated with multiple genetic and environmental factors. Over recent years, progress has been made in understanding the immunological alterations implicated in the disease, but the exact pathogenesis still needs to be elucidated. A pathogenic interplay between innate immunity and autoimmunity contributes to the intra-thymic MG development. Epigenetic changes are critically involved in both innate and adaptive immune response regulation. They can act as (i) pathological factors besides genetic predisposition and (ii) co-factors contributing to disease phenotypes or patient-specific disease course/outcomes. This article reviews the role of non-coding RNAs (ncRNAs) as epigenetic factors implicated in MG. Particular attention is dedicated to microRNAs (miRNAs), whose expression is altered in MG patients' thymuses and circulating blood. The long ncRNA (lncRNA) contribution to MG, although not fully characterized yet, is also discussed. By summarizing the most recent and fast-growing findings on ncRNAs in MG, we highlight the therapeutic potential of these molecules for achieving immune regulation and their value as biomarkers for the development of personalized medicine approaches to improve disease care.

Targeting autoimmune mechanisms by precision medicine in Myasthenia Gravis

Myasthenia Gravis (MG) is a chronic disabling autoimmune disease caused by autoantibodies to the neuromuscular junction (NMJ), characterized clinically by fluctuating weakness and early fatigability of ocular, skeletal and bulbar muscles. Despite being commonly considered a prototypic autoimmune disorder, MG is a complex and heterogeneous condition, presenting with variable clinical phenotypes, likely due to distinct pathophysiological settings related with different immunoreactivities, symptoms' distribution, disease severity, age at onset, thymic histopathology and response to therapies. Current treatment of MG based on international consensus guidelines allows to effectively control symptoms, but most patients do not reach complete stable remission and require life-long immunosuppressive (IS) therapies. Moreover, a proportion of them is refractory to conventional IS treatment, highlighting the need for more specific and tailored strategies. Precision medicine is a new frontier of medicine that promises to greatly increase therapeutic success in several diseases, including autoimmune conditions. In MG, B cell activation, antibody recycling and NMJ damage by the complement system are crucial mechanisms, and their targeting by innovative biological drugs has been proven to be effective and safe in clinical trials. The switch from conventional IS to novel precision medicine approaches based on these drugs could prospectively and significantly improve MG care. In this review, we provide an overview of key immunopathogenetic processes underlying MG, and discuss on emerging biological drugs targeting them. We also discuss on future direction of research to address the need for patients' stratification in endotypes according with genetic and molecular biomarkers for successful clinical decision making within precision medicine workflow.

The Proteostasis of Thymic Stromal Cells in Health and Diseases

The thymus is the key immune organ for the development of T cells. Different populations of thymic stromal cells interact with T cells, thereby controlling the dynamic development of T cells through their differentiation and function. Proteostasis represents a balance between protein expression, folding, and modification and protein clearance, and its fluctuation usually depends at least partially on related protein regulatory systems for further survival and effects. However, in terms of the substantial requirement for self-antigens and their processing burden, increasing evidence highlights that protein regulation contributes to the physiological effects of thymic stromal cells. Impaired proteostasis may expedite the progression of thymic involution and dysfunction, accompanied by the development of autoimmune diseases or thymoma. Hence, in this review, we summarize the regulation of proteostasis within different types of thymic stromal cells under physiological and pathological conditions to identify potential targets for thymic regeneration and immunotherapy.

Thymic gene expression analysis reveals a potential link between HIF-1A and Th17/Treg imbalance in thymoma associated myasthenia gravis

Myasthenia gravis (MG) is an immune-mediated disease frequently associated with thymic changes. Increased T helper 17 (Th17) cell activity and dysfunctional regulatory T (Treg) cells have been demonstrated in subgroups of MG. On the other hand, hypoxia-inducible factor 1 (HIF-1) has been shown to regulate the Th17/Treg balance by inducing Th17 differentiation while attenuating Treg development. To identify the underlying mechanisms of different thymic pathologies in MG development, we evaluated thymic samples from thymoma-associated myasthenia gravis (TAMG), MG with hyperplasia (TFH-MG) and thymoma without MG (TOMA) patients. Differential gene expression analysis revealed that TAMG and TFH-MG cells are associated with different functional pathways. A higher RORC/FOXP3 ratio provided evidence for Th17/Treg imbalance in TAMG potentially related to increased HIF1A. The hypoxic microenvironment in thymoma may be a driver of TAMG by increasing HIF1A. These findings may lead to new therapeutic approaches targeting HIF1A in the development of TAMG.

[Clinical and epidemiological characteristics of myasthenia in the Altai region]

OBJECTIVE

To analyze the epidemiological and clinical characteristics of myasthenia gravis (MG) in the Altai region (AR).

MATERIAL AND METHODS

One hundred and twenty-two patients with a verified diagnosis of MG, living in the AR, took part in the study. To collect data, a questionnaire was developed, the data of which formed the basis for the study. Data analysis was carried out using the Statistica 12 program (Stat. Soft, Inc.).

RESULTS

The group of patients studied makes up 14-28% of the expected number of patients with MG in AR. In general, patients with late onset of the disease predominated in the group (71 people versus 51). A predominance of women was revealed in the group with an early onset of the disease, while in the group with a late onset the ratio of men and women levels out. The identification of two peaks in the age of onset of the disease in women, which was not observed in the group of men, was a feature of the clinical course of MG in AR. In the study group, the generalized form of MG was more common; the onset of the disease in most patients began with weakness of the external eye muscles. In most patients, MG was associated with antibodies to the acetylcholine receptor, but seronegative cases were also noted. A rarer frequency of thymus pathology has been established. An analysis was carried out of the factors that preceded the onset of MG, among which the most common was viral infection.

CONCLUSION

The clinical and epidemiological features of MG in AR are described. Further monitoring of clinical and epidemiological data on MG in AR will make it possible to clarify the regional characteristics of risk factors for the development and course of the disease.