Collagen in rheumatoid arthritis

LncRNA-mRNA co-expression analysis revealed 8 core lncRNAs in rheumatoid arthritis of collagen-induced arthritis rats

BACKGROUNDS

Rheumatoid arthritis (RA) is a chronic inflammatory and autoimmune disease. Current studies suggest that long noncoding RNAs (lncRNAs) may be key regulators in pathogenesis.

METHODS

Analyzed lncRNAs and mRNAs using microarrays to find key differentially expressed lncRNAs in RA. GO and KEGG enrichment analysis together with coding non-coding co-expression (CNC) network was used for comprehensive analysis. Verify that their expression levels are consistent with the chip results by qRT-PCR.

RESULTS

There are 268 differentially expressed lncRNAs (DELs) and 286 differentially expressed mRNAs (DEMs). We found 8 core lncRNAs through the CNC network. Eight highly significantly differentially expressed lncRNAs corrected with microarray profiles. The functions and associated pathways of significantly differentially expressed lncRNAs were predicted by GO and KEGG analysis. They may be involved in the pathogenesis of RA.

CONCLUSION

The differential expression profiles of lncRNAs and mRNAs in the collagen-induced arthritis rat model preliminarily predicted functions through comprehensive analysis. However, its exact role and specific mechanism remain to be further studied.

Effects of aging and exercise training on the histological and mechanical properties of articular structures in knee joints of male rat

The impact of aging on joints can have a profound effect on an individual's functioning. Our objectives were to assess the histological and mechanical properties of the knee joint capsule and articular cartilage with aging, and to examine the effects of exercise on age-related changes in the knee joint. 2-year-old Wistar rats were divided into a sedentary control group and an exercise-trained group. 10-week-old animals were used to investigate the changes with aging. The joint capsule and cartilage were evaluated with histological, histomorphometric, immunohistochemical, and mechanical analyses. Severe degenerative changes in articular cartilage were observed with aging, whereas exercise apparently did not have a significant effect. The articular cartilage of aged rats was characterized by damage to the cartilage surface, cell clustering, and an abnormal cartilage matrix. Histomorphometric analysis further revealed changes in cartilage thickness as well as a decreased number of chondrocytes. Aging led to stiffness of the articular cartilage and reduced the ability to dissipate the load and distribute the strain generated within the joint. Joint stiffness with aging was independent of capsular stiffness and synovitis was not a characteristic feature of the aging joint. This study confirms that aging alone eventually leads to joint degeneration in a rat model. The lack of recovery in aging joint changes may be due to several factors, such as the duration of the intervention and the regeneration ability of the cartilage.

Expression patterns of collagen types I and III in the capsule of a rat knee contracture model

Our objective was to determine the changes in expression of collagen types I and III in the capsule of a rat knee contracture model. The unilateral knee joints of adult male rats were rigidly immobilized at 150 degrees of flexion using a rigid plastic plate and screws for 3 days, 1, 2, 4, 8, and 16 weeks (immobilized group). Sham-operated animals had holes drilled in the femur and tibia with screws inserted without a plate (control group). The expression patterns of collagen types I and III in the anterior and posterior capsule were evaluated by in situ hybridization (ISH), quantitative real-time polymerase chain reaction (qPCR), immunohistochemistry (IHC), and Western blotting (WB). Expressions of collagen types I and III were decreased after immobilization compared to the control group by ISH and qPCR. The expression was not changed after immobilization compared to the control group by IHC and WB. The expression of mRNA and protein levels of collagen types I and III were not increased after immobilization, which indicated that accumulation of the two types of collagen was not the etiology of joint contracture. Another process, such as capsule and synovial adhesions, may be one possible cause of joint contracture.

Preparative procedures and purity assessment of collagen proteins

Collagens represent a large family (25 members identified so far) of closely related proteins. While the preparative procedures for the members that are ubiquitous and present in tissues in large quantities (typically fibre and network forming collagens types I, II, III, IV and V) are well established, the procedures for more recently discovered minor collagen types, namely those possessing large non-collagenous domain(s) in their molecule, are mostly micropreparative and for some collagenous proteins even do not exist. The reason is that the proof of their existence is based on immunochemical staining of tissue slices and nucleic database searching. Methods of preparation and identification of constituting alpha-polypeptide chains as well as collagenous and non-collagenous domains are also reviewed. Methods for revealing non-enzymatic posttranslational modifications (particularly of the fibre forming collagen types) are briefly described as well.

High collagen type I and low collagen type III levels in knee joint contracture: an immunohistochemical study with histological correlate

We studied the levels of collagen type I and type III in the knee joints of rats immobilized for periods of 2, 4, 16 and 32 weeks and sham-operated controls. The intensities of immunostaining of the anterior and posterior synovial intima, anterior and posterior subintima, and patellar tendon were graded on a scale from 0 to 3. We found higher type I collagen levels in immobilized legs than in sham-operated legs in the anterior subintima after 4 and 16 weeks (mean score 2.1 vs 1.3, 2.2 vs 1.3, respectively) and posterior subintima after 2, 4 and 16 weeks of immobility (2.4 vs 1.7, 2.3 vs 1.5, 2.2 vs 1.3, respectively). Lower type III collagen levels were found in immobilized legs than in sham-operated legs in the anterior synovial intima after 32 weeks (1.3 vs 2.3), and posterior synovial intima and posterior subintima after 16 weeks of immobility (1.4 vs 2.8, 1.2 vs 1.7, respectively). The higher type I collagen levels in the subintima combined with lower type III suggests that the contracture process is marked by fibrosis, not new tissue proliferation. In this respect, contractures differ from granuloma, scar tissue and the pannus of inflammatory arthritis.

Characterization of rabbit stromal fibroblasts derived from red and yellow bone marrow

Rabbit stromal fibroblasts subcultured from red and yellow bone marrow and implanted beneath the renal capsule form ossicles the hemic cellularity of which mirrors the cellularity of the marrow used for culture. Although the cultured red and yellow marrow cells are similar in fine-structural appearance, they differ strikingly in enzymatic content of alpha-naphthylbutyrate esterase, which is abundant only in the cells derived from yellow marrow. Other observers (20, 21) have proposed that stromal fibroblasts are preadipocytes, and this data suggests that those derived from yellow marrow have the phenotype of more differentiated adipocytes. On the other hand, fibroblasts derived from red and yellow bone marrow show no differences in their profiles of procollagen synthesis. Both types of fibroblasts secrete type III procollagen as the major species, with a I/III ratio of 1:3; in contrast, rabbit dermal fibroblasts have a prominent peak of type I procollagen. The similarity of stromal cells derived from red and yellow bone marrow in procollagen synthesis suggests that the collagen part of the extracellular matrix is not the only basis for their intrinsic difference in capacity for hematopoiesis.

Characterization of the aortic collagens in guinea pigs with chronic vitamin C deficiency

Marginal vitamin C deficiency lasting 19 weeks caused hypercholesterolemia and hypertriglyceridemia in guinea pigs. In the thoracic aorta of deficient animals a moderate decline of type I and an increase of type III collagen was observed. Both types of collagen isolated from deficient aortas proved to be slightly underhydroxylated.

The effect of immobilization on the types of collagen synthesized in periarticular connective tissue

The distribution of collagen types was studied in control and immobilized periarticular connective tissue to test the hypothesis that inflammatory tissue is the basis of the contracture process. The hypothesis derives from the fact that Type III collagen is prominent in inflammatory processes. The content of Type I and Type III collagen was determined by standard differential salt precipitation of the pepsin solubilized collagen, followed by resolution of the subunits on CM-cellulose. Analysis of the peptide fragments produced by cyanogen bromide was performed and their distribution determined by SDS gel electrophoresis. The collagen of control and immobilized periarticular connective tissue proved to be entirely Type I. Type III was not present. The periarticular connective tissue contracture process, therefore, is different from the intraarticular process in which fibrofatty connective tissue proliferation is prominent.

Ways of collagen separation in pathologically altered tissue

A system of chromatographic methods using two successive DEAE-cellulose chromatographic steps and two successive separations on Bio-Gel A-1.5 m has been worked out for the separation of individual collagen types. The success of the procedure is based on the preliminary removal of proteoglycans during the first DEAE-cellulose run. Alternatively it is possible to replace chromatographic steps, following the removal of proteoglycans, with fraction precipitation.