Inhibition of cyclooxygenase by indomethacin modulates osteoblast response to titanium surface roughness in a time‐dependent manner

Abstract

Prostaglandin E2 (PGE2) and transforming growth factor-beta 1 (TGF-beta 1) production are increased in cultures of osteoblasts grown on rough surfaces and prostaglandins are involved in osteoblast response to surface roughness. In the present study, we examined the effect of inhibiting cyclooxygenase on this response. MG63 osteoblast-like cells were cultured on cpTi disks with Ra values of 0.60 micron (PT), 3.97 microns (SLA), and 5.21 microns (TPS) in the presence or absence of 10(-7) M indomethacin. Treatment was begun on days 1, 2, 3, or 4 after seeding, and all cultures were harvested on day 5. Indomethacin decreased PGE2 release by the cells to less than 50% of basal levels when the cells were cultured on plastic. Cell number decreased with increasing surface roughness and indomethacin treatment abrogated the surface roughness effect over time. Alkaline phosphatase specific activity (ALP) increased with surface roughness; after one day with indomethacin, ALP was 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 increases due to surface roughness, but had no effect on osteocalcin production on smooth surfaces. TGF-beta 1 levels in the cell layer and media were sensitive to surface roughness; on rougher surfaces, TGF-beta 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 of surface roughness, since indomethacin causes a time-dependent abrogation of the response, but has no effect on proliferation, osteocalcin release, or TGF-beta 1 levels on smooth surfaces. Indomethacin's effect was not immediate, suggesting that clinical protocols could be designed that would reduce inflammation without preventing osteoblastic differentiation. The effect of indomethacin was not complete, since TGF-beta 1 and ALP remained elevated on rough surfaces, suggesting that pathways or factors other than prostanoids are involved. TGF-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 importance of local factors in the autocrine regulation of osteogenesis and the potential for factors released in response to surface morphology to act in a paracrine manner.

Osteoblasts preferentially adhere to peaks on micro-structured titanium

“…Tailored experiments have since proved that cells are indeed capable to translate geometric cues into intracellular signals that then can affect cell fate and activity 7,9,26,27) . More specifically micro-rough surfaces were demonstrated to enhance the expression of osteoblast-specific genes such as alkaline phosphatase, osteoprotegerin or osteocalcin 2,25,28,29) , thus attracting the attention of the scientific world as good candidates for endosseous devices because of their improved integration in bone 30) . The use of recent tools such as FIB has allowed for unprecedented insights into how cells adhere to their substrate, providing a way to better understand the role of cell forces in adhesion to microtextured surfaces 16) .…”

Pulsed electromagnetic fields enhance BMP‐2 dependent osteoblastic differentiation of human mesenchymal stem cells

“…38 For example, osteoblasts exhibit greater response to BMP-2 when cultured on surfaces with micron-scale roughness. 39 In addition, they produce higher levels of growth factors and cytokines that regulate osteogenesis including PGE2, which is required for their differentiation, 40,41 and osteoprotegerin, 42 which can modulate osteoclastic bone resorption. 43 Similarly, osteoblastic differentiation of bone marrow stromal cells and fetal rat calvarial cells is also surface dependent, [44][45][46] but the role of surface properties on differentiation of isolated human MSCs was not previously examined.…”

Pretreatment of bone with osteoclasts affects phenotypic expression of osteoblast‐like cells

“…Approximately 20'% of total TGF-PI produced by the MG63 cells on plastic is in the cell layer. When MG63 cells are cultured on Ti surfaces, this increases with increasing roughness (Ti-S, 30%; Ti-R, 42%) [41]. Whether this is true for MG63 cells cultured on bone wafers is not known, however.…”