Extended Abstract
Introduction
Multiple sclerosis (MS) is an autoimmune and inflammatory disease in which the myelin sheath in the central nervous system is attacked by the immune system. Studies indicate that both genetic and environmental factors influence the disease. Attack to various parts of the nervous system and the impact of environmental factors contribute to the highly variable symptoms of MS, which can include weakness, numbness and tingling in one or more limbs, dizziness, facial pain, and double vision. The onset of this disease typically occurs in young adulthood, between the ages of 20 and 40. Women are at a higher risk of developing MS, with a prevalence rate 2-3 times greater than men. The corpus callosum, the largest fiber bundle in the brain, forms the main connection between the two cerebral hemispheres and is involved in complex functions, such as cognition and sensory integration. The corpus callosum is frequently abnormal in MS. Cognitive impairments affect approximately 50% of MS patients and are categorized by impaired attention, reduced memory, slow information processing, deficits in executive functions, and visuospatial impairments. The corpus callosum consists of several distinct parts, including the rostrum, genu, body, and splenium. The corpus callosum is a common target in MS, often exhibiting focal demyelinating lesions and atrophy in the early stages of the disease. Therefore, studies have been directed toward investigating the corpus callosum. Interleukin-6 (IL-6) is a multifunctional cytokine expressed in most tissues involved in inflammatory processes and is involved in regulating the immune response. In fact, this protein has a multifunctional role. That is, while it plays a role in creating inflammation, it is also involved in preventing inflammation. Abnormally high concentrations of IL-6 may give rise to excessive inflammation and increased MS disease activity. Furthermore, increased IL-6 levels can disrupt the clearance of pathogenic microbial agents that have played a role in T cell activity and may be covertly involved in the progression of MS. IL-10 is a type of regulatory cytokine secreted by Th2 cells and is an anti-inflammatory cytokine whose function leads to the cessation of inflammation and lesions in MS. According to research, systemic levels of IL-10 decrease before the recurrence and activation of MS and gradually increase at the beginning of the recovery phase.
IL-10 is secreted by regulatory T cells (Tregs) with anti-inflammatory properties and can inhibit the production of pro-inflammatory cytokines produced by macrophages and T cells. The IL-6 gene consists of 5 exons, 4 introns, and a proximal promoter region located on the 7p21 chromosomal locus in humans. This study aimed to determine the effects of IL-10 (-1082/-819) and IL-6 (-174) gene polymorphisms on corpus callosum changes in women with MS.
Methods
This case-control study was conducted on 40 women with MS aged 20-40 years referring to Golestan and Kowsar Magnetic Resonance Imaging (MRI) centers in Gorgan, Iran and 20 women without MS, autoimmune or inflammatory diseases over 40 years in 2015.
The disease in the case group was diagnosed by a neurologist, and after the diagnosis, blood samples were collected from the volunteers. The control group was confirmed by a specialist physician to be free of any autoimmune or inflammatory diseases.
The inclusion criteria for the case group included a diagnosis of MS and an age range of 20 to 40 years. For the control group, the criteria were the absence of MS, autoimmune, or inflammatory diseases, and an age range over 40 years.
Ten mL of blood was taken from the subjects. Blood samples were stored in 15-mL sterile Falcon tubes containing ethylenediaminetetraacetic acid (EDTA) anticoagulant, and DNA was extracted using the phenol-chloroform method. Samples were amplified using the sequence specific primer-polymerase chain reaction (SSP-PCR) method. This method was used for genotyping single nucleotide polymorphisms (SNPs).
To ensure the reliability of PCR results, a primer named human growth hormone (HGH) was utilized as an internal control. PCR products were electrophoresed on a 1.5% agarose gel containing safe stain and their results were visualized using a gel documentation system (Gel doc).
The diagnosis of MS was confirmed based on T2-weighted imaging and fluid-attenuated inversion recovery (FLAIR) sequences. For morphometric measurements of the corpus callosum, midsagittal images (T1-weighted imaging) and Syngo Fast View software were used. The corpus callosum indices measured in both case and control groups included rostrum width (a), splenium width (b), body width (c), anteroposterior length (d), maximum height (e), the ratio of body width to anteroposterior length (c/d), and the ratio of body width to maximum height (c/e).
Results
The mean rostrum width of the corpus callosum (in cm) was determined to be 6.110±2.01 in the case group and 10.170±2.42 in the control group. A statistically significant decrease in the rostrum width was observed in the case group compared to the control group (P<0.001).
The mean splenium width of the corpus callosum (in cm) was determined to be 7.035±1.59 in the case group and 11.595±1.44 in the control group. A statistically significant decrease in the splenium width was observed in the case group compared to the control group (P<0.001).
The mean body width of the corpus callosum (in cm) was determined to be 3.425±1.07 in the case group and 6.055±0.87 in the control group. A decrease in the body width of the corpus callosum was observed in the case group compared to the control group (P<0.001).
No significant statistical correlation was found between the anteroposterior length and height of the corpus callosum in the case group compared to the control group. However, a significant decrease was observed in the ratio of body width to anteroposterior length, as well as in the ratio of body width to maximum height of the corpus callosum in the case group compared to the control group (P<0.001).
Following tests and obtaining various IL-6, IL-10 (-819), and IL10
(-1082) genotypes, no significant statistical correlation was found between interleukin genotypes in the case and control groups.
No significant correlation was found between the various genotypes of IL-6, IL-10 (-819), and IL-10 (-1082) and alterations in the dimensions of different parts of the corpus callosum, including rostrum width, splenium width, body width, the ratio of body length to anteroposterior length, and the ratio of body length to maximum height between the case and control groups. Furthermore, no significant statistical difference was observed in the CC, AC, and AA genotypes of IL-10 at location -819 and rostrum width of the corpus callosum between the case and control groups.
Reductions in the variables of rostrum width, splenium width, body width, the ratio of body width to anteroposterior length, and the ratio of body width to maximum height were statistically significant in both the case and control groups (P<0.05).
None of the factors demonstrated a statistically significant association with MS. Only a decrease in splenium width was significantly associated with the occurrence of MS (P<0.009, odds ratio [OR]=2.35, 95% confidence interval [CI]=4.51-1.22).
Conclusion
There is no correlation between morphometric changes of reduced corpus callosum dimensions and the changes in IL-6, IL-10(-819), and IL10 (-1082) genotypes in patients with MS.
Ethical Statement
This study was approved by the Ethics Committee of Golestan University of Medical Sciences (IR.GOUMS.REC.1395.153).
Funding
This article has been extracted from the master’s thesis of Ms. Maryam Abolqazi in Anatomy at the Faculty of Medicine, Golestan University of Medical Sciences.
Conflicts of Interest
No conflict of interest.
Acknowledgement
The authors would like to thank Kowsar and Izadi Comprehensive MRI centers, the MS Association of Golestan Province, and all participants in the study.
Key message: There was no relationship between the morphometric changes of reduced corpus callosum and the changes in IL-6, IL-10 (-819), and IL-10 (-1082) genotypes in patients with MS.