ADAMTS-1 activity influence Collagen type I processing in osteoblastic cells

Objectives: Our aim was to show if the ADAMTS-1 protein (A Disintegrin And Metalloprotease with ThromboSpondin repeats) could be involved in activities regarded as MMP activity. ADAMTS-1 is a member of a family of secreted multi-domain neutral endopeptidases and has a protease domain similar to the protease domains of MMP's. Methods: Human osteosarcoma SAOS-2 cells were transfected with two different constructs, wild type ADAMTS-1 (wtATS) or a catalyticly inactive version (pmATS). Screening for ADAMTS-1 activity were done through western blotting of conditioned media (CM), extra cellular matrix (ECM) and cell extracts of pmATS and wtATS cells with an antibody recognising the collagen Pro-a1 type I C-telopeptide. Immuno electron microscopy (iEM) was used to analyze mouse femur osteoids labelled with ADAMTS-1 antibody. The antibody was blocked with its antigen as a control. Gold markers associated to collagen type I were counted and analyzed with FisherLs exact statistical test. Results: wtATS cells released more collagen type I fragments into the cell media compared to cells expressing the pmATS. Also less collagen type I was detected in the ECM from wtATS cells but cell associated collagen type I showed no difference between cells expressing either inactive or active ADAMTS-1. iEM showed more markers associated to collagen I fibrils in the mouse femur osteoid labelled with the specific ADAMTS-1 antibody compared with the control, statistical significant p-value. Conclusion: In this study we show a indication that ADAMTS-1 is associated to collagen type I fibrils in bone through iEM of mouse femur osteoid and that ADAMTS-1 activity induce release of type I collagen fragments into conditioned media of cultured osteoblastic cells. Furthermore we show that ADAMTS-1 activity induce fibrilar collagen breakdown and this also indicates a role for ADAMTS-1 in bone remodelling.