The responses of extrinsic fibroblasts infiltrating the devitalised patellar tendon to IL-1beta are different from those of normal tendon fibroblasts.

In order to clarify the role of cytokines in the remodelling of the grafted tendon for ligament reconstruction we compared the responses to interleukin (IL)-1beta, platelet-derived growth factor (PDGF)-BB and transforming growth factor (TGF)-beta1 of extrinsic fibroblasts infiltrating the frozen-thawed patellar tendon in rats with that of the normal tendon fibroblasts, in regard to the gene expression of matrix metalloproteinase (MMP)-13, using Northern blot analysis. We also examined, immunohistologically, the local expression of IL-1beta, PDGF-BB, and TGF-beta1 in fibroblasts infiltrating the frozen-thawed patellar tendon. Northern blot analysis showed that fibroblasts derived from the patellar tendon six weeks after the freeze-thaw procedure in situ showed less response to IL-1beta than normal tendon fibroblasts with respect to MMP-13 mRNA gene expression. The immunohistological findings revealed that IL-1beta was over-expressed in extrinsic fibroblasts which infiltrated the patellar tendon two and six weeks after the freeze-thaw procedure in situ, but neither PDGF-BB nor TGF-beta1 was over-expressed in these extrinsic fibroblasts. Our findings indicated that IL-1beta had a close relationship to matrix remodelling of the grafted tendon for ligament reconstruction, in addition to the commencement of inflammation during the tissue-healing process.