Inhibition of cyclooxygenase by indomethacin modulates osteoblast responseto titanium surface roughness in a time-dependent manner

Prostaglandin E-2 (PGE(2)) and transforming growth factor-beta1 (TGF-beta ( 1)) production are increased in cultures of osteoblasts grown on rough surf aces and prostaglandins are involved in osteoblast response to surface roug hness. In the present study, we examined the effect of inhibiting cyclooxyg enase on this response. MG63 osteoblast-like cells were cultured on cpTi di sks with R-a values of 0.60 mum (PT), 3.97 mum (SLA), and 5.21 mum (TPS) in the presence or absence of 10(-7) M indomethacin. Treatment was begun on d ays 1, 2, 3, or 4 after seeding, and all cultures were harvested on day 5. Indomethacin decreased PGE(2) release by the cells to less than 50% of basa l levels when the cells were cultured on plastic. Cell number decreased wit h increasing surface roughness and indomethacin treatment abrogated the sur face roughness effect over time. Alkaline phosphatase specific activity (AL P) increased with surface roughness; after one day with indomethacin, ALP w as decreased on smooth surfaces, but increased on rough surfaces. Over time , ALP decreased on all surfaces examined and remained greater than plastic only in cultures on TPS. Indomethacin also caused a time-dependent decrease in osteocalcin production on rough surfaces, eventually abrogating the inc reases due to surface roughness, but had no effect on osteocalcin productio n on smooth surfaces. TGF-beta (1) levels in the cell layer and media were sensitive to surface roughness; on rougher indomethacin causes a time-depen dent abrogation of the response, but has no effect on proliferation, osteoc alcin release, or TGF-beta (1) levels on smooth surfaces. surfaces, TCF-bet a (1) shifted from the media to the matrix. Indomethacin reduced TGF-beta ( 1) levels over time, but the surface roughness effect was still evident at 4 days. This indicates that prostaglandin production mediates the effects o f surface roughness, since indomethacin causes a time-dependent abrogation of the response, but has no effect on profileration, osteocalin release, or TGF-beta (1) levels on smooth surfaces. Indomethacin's effect was not imme diate, suggesting that clinical protocols could be designed that would redu ce inflammation without preventing osteoblastic differentiation. The effect of indomethacin was not complete, since TCF-beta (1) and ALP remained elev ated on rough surfaces, suggesting that pathways or factors other than pros tanoids are involved. TCF-beta (1) is preferentially stored in the matrix, acting on the cells through autocrine signaling, and may contribute to ALP even in the presence of indomethacin. These results demonstrate the importa nce of local factors in the autocrine regulation of osteogenesis and the po tential for factors released in response to surface morphology to act in a paracrine manner.