Immune cell transcript modules reveal leukocyte heterogeneity in synovial biopsies of seronegative spondylarthropathy patients

RAB5C, SYNJ1, and RNF19B promote male ankylosing spondylitis by regulating immune cell infiltration

Background

This study aimed to identify the key genes related to male ankylosing spondylitis (AS) and to analyze the role of immune cell infiltration in the pathological process of this disease.

Methods

The AS dataset was downloaded from the Gene Expression Omnibus (GEO) public database, and the data of male healthy controls (M_HC) and male AS patients (M_AS) were extracted. R software was used to identify differentially expressed genes (DEGs). Functional and pathway enrichment analysis of the DEGs was performed. A protein-protein interaction (PPI) network was constructed, and the hub genes were screened out. All expression profile data were analyzed by weighted correlation network analysis (WGCNA) to screen out the hub genes, which were then intersected with the hub genes from the PPI network to obtain the key genes. Finally, the difference in immune cell infiltration in the two sets of samples was evaluated with CIBERSORT, and the correlation between the key genes and infiltrating immune cells was analyzed.

Results

A total of 689 DEGs were obtained, of which 395 genes were up-regulated and 294 genes were down-regulated. Functional and pathway enrichment analysis showed that DEGs were mainly enriched in pathways related to immune response. Based on the PPI analysis, five clusters with high scores were selected. Through WGCNA, 14 gene modules were obtained. The green module with the highest correlation was selected and intersected with the cluster previously obtained to obtain three key genes, RAB5C, SYNJ1, and RNF19B. Immune infiltration analysis found that monocytes and gamma delta T cells may be involved in the process of AS. Also, RAB5C, SYNJ1, and RNF19B are all related to increased levels of monocytes and macrophages.

Conclusions

RAB5C, SYNJ1, and RNF19B are key DEGs expressed in M_AS and may play a role in the disease’s occurrence and development through regulating immune cell functions.

Different Contributions of CDKAL1, KIF21B, and LRRK2/MUC19 Polymorphisms to SAPHO Syndrome, Rheumatoid Arthritis, Ankylosing Spondylitis, and Seronegative Spondyloarthropathy

OBJECTIVES

Synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome, rheumatoid arthritis (RA), ankylosing spondylitis (AS), and seronegative spondyloarthropathy (SPA) are autoimmune diseases of unknown etiology, which share some clinical manifestations in common. Previous family-based investigations support genetic contributions to the susceptibility of these diseases. The current study evaluated whether three previously reported AS-associated single-nucleotide polymorphisms (SNPs), rs6908425 T>C in CDKAL1, rs11584383 T>C near KIF21B, and rs11175593 C>T near LRRK2/MUC19, have any genetic overlap across multiple autoimmune diseases including SAPHO syndrome, RA, AS, and SPA.

MATERIALS AND METHODS

Genomic DNA was obtained from 71 SAPHO, 125 RA, 67 AS, and 35 SPA Han Chinese patients, as well as 104 healthy controls. SNPs were genotyped by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Genotype and allele frequencies were analyzed using chi-square test.

RESULTS

rs6908425 T>C in CDKAL1 was significantly different between SAPHO cases and healthy controls (odds ratios = 2.056, 95% confidence intervals: 1.211-3.490; p = 0.007), but no SNPs were associated with the risk of developing RA, AS, or SPA (p > 0.05). Analysis of genotype distributions showed similar results. A significant difference was only found in the genotype frequency of rs6908425 in SAPHO cases (p = 0.004); no significant differences were detected among patients with RA, AS, and SPA (p > 0.05).

CONCLUSIONS

Our results suggest that rs6908425 in CDKAL1 is associated with the risk of developing SAPHO in Han Chinese populations. People who carry the risk allele T of rs6908425 might be more prone to developing SAPHO syndrome.

Single Cell Analysis of Leukocyte Protease Activity Using Integrated Continuous-Flow Microfluidics

Leukocytes are the essential cells of the immune system that protect the human body against bacteria, viruses, and other foreign invaders. Secretory products of individual leukocytes, such as matrix metalloproteinases (MMPs) and a disintegrin and metalloproteinase (ADAMs), are critical for regulating the inflammatory response and mediating host defense. Conventional single cell analytical methods, such as flow cytometry for cellular surface biomarker studies, are insufficient for performing functional assays of the protease activity of individual leukocytes. Here, an integrated continuous-flow microfluidic assay is developed to effectively detect secretory protease activity of individual viable leukocytes. Leukocytes in blood are first washed on-chip with defined buffer to remove background activity, followed by encapsulating individual leukocytes with protease sensors in water-in-oil droplets and incubating for 1 h to measure protease secretion. With this design, single leukocyte protease profiles under naive and phorbol 12-myristate 13-acetate (PMA)-stimulated conditions are reliably measured. It is found that PMA treatment not only elevates the average protease activity level but also reduces the cellular heterogeneity in protease secretion, which is important in understanding immune capability and the disease condition of individual patients.