**4. The localization of exoglycosidases in joint tissues**

Pugh and Walker (Pugh 1961), using histochemical techniques, reported that the source of HEX activity in synovial fluid is from cells of the synovial membrane. Others (Shikhman et al. 2000; Ortutay et. al. 2003) have suggested that chondrocytes of RA patients activated by IL 1β (interleukin-1β) may be a source of HEX activity in synovial fluid. Relating to this, it has been observed that damage to the joint reduces the volume of cartilage and increases a proliferation of synovial membrane (Fig. 3).

Profiles of the exoglycosidases in the synovial membrane of the knee joint of patients with RA, JIA and a control group are presented in Fig. 4.

Fig. 4. The activity of exoglycosidases in the synovial tissue of the knee joint of patients with RA and JIA.

Normal and inflamed synovial tissues have similar patterns of exoglycosidases activity with a significant predominance of HEX activity (Popko et.al.2006). HEX activity in the synovial tissue of RA and JIA patients was approximately 10-fold higher than in the synovial tissue of the reference group. The increase in activity of GluA, GAL, MAN and FUC in synovial tissue of RA and JIA patients (in comparison with reference groups) was moderate, i.e. no more than doubled.

Synovial fibroblast-like cells and chondrocytes may be regarded as a source of mediators of joint destruction in RA and JIA. Synoviocytes and chondrocytes secrete proteolytic enzymes and exoglycosidases, especially HEX, that are crucial for the degradation of cartilage. The destructive phenotypes of the synovial fibroblasts-like cell and chondrocytes in RA are probably regulated by inflammatory cytokines released by the pannus connected to the cartilage.

Lysosomal Glycosidases in Degradation of Human Articular Cartilage 103

In Ex In Ex In Ex In Ex In Ex In Ex

Fig. 6. Exoglycosidases activity of RA/JIA synovial fibroblast in the intra (In) / extracellular

IL-1 and TNF-α (tumor necrosis factor-α) are key proinflammatory cytokines whose

We have established a profile of exoglycosidases in cell cultures stimulated by IL-1β of

Stimulation by IL-1β cultured synoviocytes taken from patients with ACL, JIA and RA causes much higher increases in activity of HEX and HEX A than remaining exoglycosidases (Fig. 7). On Fig. 7 one can see that the increase in HEX activity after IL-1β stimulation is more pronounced in the intracellular compartment of synoviocytes derived from rheumatoid patients than in ACL-injury, amounting 189.44 % increase (in comparison to untreated cultures) in synoviocytes from JIA, and 127.97 % in synoviocytes of RA patients. We noted a 201.18 % increase in HEX-A activity (in comparison to untreated cultures) in stimulated synoviocytes from JIA, and a 128.03 % increase in synoviocytes of patients with RA. In extracellular compartment of cultured rheumatoidal synoviocytes, stimulation by IL-1β cause only 33.4-72.44 % increases in HEX and HEX A activities. In extracellular compartment of cultured synoviocytes derived from injured knees of ACL patients, after stimulation by IL-1β the highest increase (121.80 %) was observed in HEX A activity. The mechanism of selective stimulation of HEX by IL-1β is not known. Shikhman et al. (2000) suggested that cytokines are involved in secretion of HEX from chondrocytes and stated that IL-1β could selectively up-regulate HEX synthesis and facilitate intra-compartmental transport of HEX from lysosomes/endosomes into the extracellular space, by modifying the

concentration significantly increases in rheumatoid synovial fluid and joint tissues.

inflamed (RA, JIA), and post-injury human synoviocytes (Popko et al. 2008) (Fig. 7).

HEX A β-GluA β-GAL α-MAN α-FUC

RA JIA

0

HEX (total)

(Ex) compartment, expressed as pKat/3-5x105 cells.

mannose-6-phosphate receptor system.

50

100

150

200

The activity of exoglycosidases ( pkat/3-5x 105

 cell )

250

300

350

400

450

The high activity of exoglycosidases in synovial tissue of RA and JIA patients (Popko et al.2006) suggest the value of synovectomy in treatment of rheumatoid diseases (Fig. 5).

Fig. 5. Arthroscopic synovectomy a knee of patient with JIA.

We recommend the usefulness of synovectomy in patients with RA and JIA, as the removal of diseased synovial tissue (Fig. 5) could slow down the destructive process of the joint cartilage, and allow regeneration of a normal synovial membrane.
