Adhesion molecules in gonarthrosis and knee prosthesis aseptic loosening follow-up: possible therapeutic implications

Cytokine production following experimental implantation of xenogenic dermal collagen and polypropylene grafts in mice

AIM

We earlier showed that xenogenic Pelvicol (Bard, Olen, Belgium) implants induce a lesser inflammatory response than Prolene (Johnson and Johnson, Dilbeek, Belgium). The purpose of this study was to determine cytokine profiles in the host immune responses to Pelvicol in a mouse model. The hypothesis was that Pelvicol would induce a "T-helper2" (Th2) rather than T-helper1 (Th1) type of inflammatory response.

METHODS

Mice were implanted subcutaneously with Pelvicol or Prolene and the graft sites were harvested at 3 to 28 days. Histopathology was done and cytokine levels were determined by immunohistochemistry and RT-PCR. Flow cytometry was used to identify which cell population contributed to the observed cytokine production profiles.

RESULTS

Pelvicol induced a decreased inflammation and displayed an increase in IL-10 and TGF-beta, but reduce of TNF-alpha and IFN-gamma, indicating a Th2 type dominated response as examined by immunohistochemistry and RT-PCR. Flow cytometry showed that the monocytes/maceophages were the main cell population responsible for production of these cytokines. Monocytes/maceophages from Pelvicol explants showed upregulated expression of IL-10 while Prolene explants expressed TNF-alpha.

CONCLUSION

Pelvicol induced a Th2 type cytokine-dominated immune response after subcutaneous implantation in mice.

Involvement of ICAM-1 in bone metabolism: a potential target in the treatment of bone diseases?

Bone diseases such as osteoporosis, osteoarthritis and rheumatoid arthritis (RA) affect a great proportion of individuals, with debilitating consequences in terms of pain and progressive limitation of function. Existing treatment of these pathologies has been unable to alter the natural evolution of the disease and, as such, a clearer understanding of the pathophysiology is necessary in order to generate new treatment alternatives. One therapeutic strategy could involve the targeting of intercellular adhesion molecule-1 (ICAM-1; CD54). In bone, ICAM-1 is expressed at the surface of osteoblasts (Obs) and its counter-receptor, leukocyte function-associated antigen-1 (LFA-1; CD11a), at the surface of osteoclast (Oc) precursors. ICAM-1 blockade between the Ob and the pre-Oc results in an inhibition of Oc recruitment and a modulation of inflammation, which could potentially help in controlling disease activity in bone pathologies. So far, clinical studies on ICAM-1 blockade in bone diseases have been limited to RA. A better understanding of the implication of this adhesion molecule in Ob/Oc interactions and inflammatory mediation in the bone pathological state, however, is needed. As new discoveries on the role of this adhesion molecule are being reported, ICAM-1 could become a potential target for other bone diseases as well.

Expression of ICAM-1 by osteoblasts in healthy individuals and in patients suffering from osteoarthritis and osteoporosis

OBJECTIVES

To describe the pattern of expression of intercellular adhesion molecule-1 (ICAM-1) at the surface of human osteoblasts (Ob) recovered from normal (control), osteoporotic (OP), and osteoarthritic (OA) bone. To relate ICAM-1 expression in OA Ob with interleukin-6 (IL-6) and prostaglandin E2 (PGE2) production.

MATERIALS AND METHODS

Trabecular bone specimens were taken from patients suffering from OA of the hip (n = 19) or knee (n = 19) or from hip fracture caused by osteoporosis (n = 10). Control bone specimens came from the posterosuperior iliac crest (n = 5) and from the femoral condyle of organ donors (n = 6). Bone explants were digested with collagenase and cultured. Ob were obtained after 6 weeks. ICAM-1 expression was studied by immunocytology. IL-6 and PGE2 were evaluated by standard ELISA.

RESULTS

Average ICAM-1 expression was different between control and OP bone (P < 0.02). Separation of specimens into high and low ICAM-1 expression showed a significant difference between high and low ICAM-1 expressors. The distribution of specimens after subclassification into high or low ICAM-1 expression groups revealed only 18.2% of patients in the high expression group for the controls, compared to 70% for OP bone (P < 0.03), 52.6% for hip OA and 47.4% for knee OA. IL-6 and PGE2 levels in OA Ob from both groups were found to be significantly elevated with high ICAM-1 expression compared to low ICAM-1 expression.

CONCLUSION

The results show that ICAM-1 expression in human bone seems to be pathology-dependent and correlates with IL-6 and PGE2 production, at least in OA individuals. This implies that ICAM-1 could discriminate functionally different populations of Ob and possibly alter the clinical evolution of the disease.