[Effect of diclofenac on human osteoblasts and their stromal precursors in vitro in relation to arthroplasty]

Results of animal experiments have demonstrated that the osseous integration of non-cemented prostheses can, at the very least temporarily, be impaired by the application of non-steroidal antiphlogistic agents (such as diclofenac). It is the objective of this study to examine whether there is a direct influence of diclofenac used in usual clinical dosages (3 times 50 mg daily) on bone cells and their progenitor cells which would explain the observed slow integration of the prostheses.

To investigate this, cultivated human in vitro osteoblasts and stromal bone marrow cells were incubated with increasing doses of the medications. Our study focused on the effect of diclofenac application on proliferation and functional metabolism in both cell lines. The measurable maximal plasma concentration 2 h after the application of one tablet Voltaren 50 reached 1.6 micrograms/ml. This correlated with diclofenac concentrations between 1 and 10 ml found in our experiments. The detected values were correlated to the control group (0 microgram/ml diclofenac).

The drug effect upon osteoblasts was higher than on progenitor cells. The proliferation of in vitro stromal bone marrow cells, compared to untreated cells, was found to be decreased. We observed a decrease to 82% at a diclofenac concentration of 1 microgram/ml, Osteoblasts exhibited a decrease to 97.5% at the same concentration. The DNA synthesis increased to 118% in stromal bone marrow cells, in osteoblasts to 144%. In contrast, we detected a neglectible decrease to 92% in the collagen synthesis of osteoblasts compared to untreated cells. The synthesis of osteocalcin by osteoblasts increased to 119%. The alkaline phosphatase activity was found to be decreased to 88% in stromal bone marrow cells and increased in osteoblasts to 111%.

Temporary inhibiting effects on osseous integration in non-cemented prosthesis by diclofenac could be caused by a disturbance in the anabolic bone metabolism, exhibited by an increase of osteoblastic osteocalcin expression. Osteocalcin as a known negative regulator of the osteoneogenesis is most likely inhibiting the collagen matrix deposition.