Effects of isolated rheumatoid synovial cells on cartilage degradation in vitro

Role of N-Carboxybutyl Chitosan in the Repair of the Meniscus

N-Carboxybutyl chitosan obtained from crustacean chitin was used to assist the spontaneous tissue repair of the meniscus, which is usually of extreme difficulty. Results indicate that this natural modified polysaccharide is well-tolerated at the articular synovial level. It also favors and stimulates the repair processes which do not take place spontaneously in the meniscus. N-Carboxybutyl chitosan, therefore, plays a role which helps in repairing meniscal lesions.

Modulation of fibroblast-mediated cartilage degradation by articular chondrocytes in rheumatoid arthritis

OBJECTIVE

To determine the role of chondrocytes and factors released from chondrocytes in cartilage destruction by fibroblast-like synoviocytes (FLS) derived from patients with rheumatoid arthritis (RA).

METHODS

RA FLS from 2 patients were implanted into SCID mice, together with fresh articular cartilage or with cartilage that had been stored for 24 hours at 4 degrees C or at 37 degrees C. The invasion of the same RA FLS into the fresh and stored cartilage was compared histologically using a semiquantitative scoring system. In addition, we investigated whether protein synthesis in chondrocytes affects the invasion of RA FLS in vitro. A 3-dimensional cartilage-like matrix formed by cultured chondrocytes was labeled with 35S. After formation of the cartilage-like matrix, protein synthesis was blocked with cycloheximide. The invasion of RA FLS from 6 patients into cycloheximide-treated and untreated matrix was assessed by measuring the released radioactivity in coculture with and without interleukin-1beta (IL-1beta) and tumor necrosis factor alpha (TNFalpha).

RESULTS

The SCID mouse experiments showed a significant invasion of RA FLS into the cartilage (overall mean score 3.2) but revealed significant differences when the invasion of the same RA FLS into fresh and stored cartilage was compared. RA FLS that were implanted with fresh articular cartilage showed a significantly higher invasiveness than those implanted with pieces of cartilage that had been stored for 24 hours (overall mean score 2.3). Storage at 37 degrees C and 4 degrees C resulted in the same reduction of invasion (35% and 37%, respectively). In the in vitro experiments, RA FLS rapidly destroyed the cartilage-like matrix. Blocking of chondrocyte protein biosynthesis significantly decreased the invasion of RA FLS, as shown by a decreased release of radioactivity. Addition of IL-1beta, but not TNFalpha, to the cocultures partially restored the invasiveness of RA FLS.

CONCLUSION

These data underline the value of the SCID mouse in vivo model of rheumatoid cartilage destruction and demonstrate that chondrocytes contribute significantly to the degradation of cartilage by releasing factors that stimulate RA FLS. Among those, IL-1beta-mediated mechanisms might be of particular importance.

Histopathological changes in rabbit craniomandibular joint associated with experimentally induced anterior disk displacement (ADD)

Several studies have shown that anterior disk displacement (ADD) of human temporomandibular joint (TMJ) can lead to cellular and extracellular alterations in the disk proper, bilaminar zone (BZ), condyle, articular eminence and synovial membrane. Due to lack of an animal model for this disease, it is not known whether the mechanical displacement of the disk could lead to the observed histopathological changes. The purpose of this experiment was to investigate the histopathological changes that occur in the rabbit craniomandibular joint (CMJ) following surgical induction of ADD. The right CMJ was exposed surgically and the discal attachments were severed except for the BZ attachments. Then the disk was displaced anteriorly and sutured to the zygomatic arch. The left joint served as surgical control. The CMJs were removed after 24 h, 1 week, 2 weeks or 6 weeks and stained with H&E or modified Masson stain. The results showed neovascularization, cell clustering and fibrillation of the displaced disk. The BZ showed marked fibrosis. The condyle showed subchondral hemorrhage and fibrosis followed by osteoarthritic changes in the articular cartilage. The articular eminence showed chondrocytic clustering and an increase in the amount of chondroid bone. Synovial membrane exhibited marked hyperplasia. We concluded that surgical induction of ADD in the rabbit CMJ leads to cellular and extracellular alterations in the disk proper, BZ, condyle, articular eminence and synovial membrane similar to those described previously in human ADD. It appears that the mechanical trauma resulting from ADD could lead to a cascade of reparative and degenerative changes of the affected joints similar to those described for osteoarthritis.

Inhibition of the effects of rheumatoid synovial fluid cells on chondrogenesis and cartilage breakdown in vitro: possible therapeutical conclusions. A morphological--biochemical study

Short-term co-cultivation of blastemal cells from 12-day-old mouse limb buds and human rheumatoid synovial fluid cells in high density cultures (Trowell culture system) resulted, depending on when co-cultivation started, either in (1) an inhibition of chondrogenesis (co-cultivation right from the start) or in (2) an extensive breakdown of cartilaginous matrix (co-cultivation after formation of embryonic cartilage). These synovial effects were markedly impeded if Avarol (a dioxygenase inhibitor) was applied singly or in combination with PAI-2 (a u-PA-inhibitor). PAI-2 alone, however, had no effect on the synovial-induced inhibition of chondrogenesis, but produced a pronounced inhibitory effect on matrix breakdown. The effects of both inhibitors were studied electron microscopically and biochemically (determination of sulfated-glycosaminoglycans in the high density cultures by Alcian Blue binding assay). The results of this study are consistent with the presumption that rheumatoid synovial cells are capable of inhibiting chondrogenesis and enhancing the breakdown of the cartilaginous matrix. Amongst others, the possible mediators involved are prostaglandins and plasminogen activators. The response to the inhibitors Avarol and PAI-2 is compatible with their mode of action. The chondroprotective action of these substances may be useful in developing potential antirheumatic drugs.