Infection of synoviocytes with HTLV-I induces telomerase activity

To investigate the mechanism of synovial hyperplasia by human T-lymphotropi c virus type I (HTLV-1) infection, the enzymatic activity of telomerase and expression of telomerase-related factors in HTLV-I infected synoviocytes w ere examined. Cultured synoviocytes obtained from four patients with osteoa rthritis (OA) and four with traumatic joint disease (TJD) were infected by HTLV-1. Telomerase activity was detected by telomeric repeat amplification protocol (TRAP) assay. Expression of telomerase-related mRNAs such as telom erase reverse transcriptase (hTERT), telomerase RNA component (hTERC), and telomeric repeat binding factor 2 (TRF2) were also examined. Telomerase act ivity was detected in all HTLV-1-infected synoviocytes but not in uninfecte d synoviocytes. A remarkable induction of hTERT mRNA was observed in four o f eight HTLV-I-infected synoviocytes, whereas expressions of hTERC, TRF2, a nd TEP-1 mRNAs were not changed. Our results clearly demonstrate that HTLV- I upregulates telomerase activity in synoviocytes probably via upregulation of hTERT activity. These findings suggest that telomerase activation in sy noviocytes has an important role in upregulated proliferative activity of H AAP synoviocytes.