Porous tantalum stimulates the proliferation and osteogenesis of osteoblasts from elderly female patients.

Porous tantalum (Ta) implants have been successful in various orthopedic procedures for patients with compromised bone-forming abilities. Previous studies demonstrated that human osteoblast (HOB) cultures from older female patients produced less bone on implant materials in vitro compared to HOBs from age-matched male and younger female patients. In this study, the responses of HOBs from younger (< 45) and older (> 60 years old) female patients were compared on Ta, titanium fiber mesh (TFM) and tissue culture plastic. Adhesion, proliferation, and mineralization were greater in cells from younger patients than from older patients. Cell adhesion was slightly higher on Ta than TFM or plastic. However, Ta highly stimulated cell proliferation with a 4- and 6-fold increase compared to TFM for cells from younger and older patients, respectively, and 12- and 16-fold increase in proliferation compared to cells on plastic (p ≤ 0.001). At 3 weeks, mineralization was significantly higher on Ta compared to TFM for HOBs from older patients (p ≤ 0.05). Expression levels of bone matrix markers demonstrated differences dependent on age and substrate. Scanning electron micrographs revealed HOBs covering the surfaces and entering the pores of both Ta and TFM. In conclusion, tantalum greatly stimulates cell proliferation, and improves the ability of HOBs from older patients to form bone.

The in vitro response of human osteoblasts to polyetheretherketone (PEEK) substrates compared to commercially pure titanium.

Polyetheretherketone (PEEK) is used as an alternative to titanium in medical devices. Previous in vitro studies examining PEEK have differed in their choice of polymer variant [PEEK or carbon-fiber reinforced PEEK (CFR-PEEK)], source of polymer (some of which are no longer available or for implantation) and cell type. While all studies demonstrated favorable cytocompatibility of the PEEK material, no studies are available which reflect the current state of the art of the material. Here, we use different forms of the only implantable grade PEEK available. These are compared with commercially pure titanium (cpTi) Grade 1 using a human primary osteoblast model. Sample materials were presented as industrially relevant surfaces. Machined or injection molded PEEK and CFR-PEEK were evaluated along with polished (Ra=0.200microm) and rough (Ra=0.554microm) cpTi. Osteoblast adhesion at 4h on injection molded variants of PEEK (Ra=0.095microm) and CFR-PEEK (Ra=0.350microm) material was comparable to titanium. Machined variants of PEEK (Ra=0.902microm) and CFR-PEEK (Ra=1.106microm) materials were significantly less. Proliferation at 48h determined by [(3)H]-thymidine incorporation was the greatest on the smoothest of all materials, the injection molded unfilled PEEK, which was significantly higher than the rough titanium control. The machined unfilled PEEK had the lowest DNA synthesis. RT-PCR for alkaline phosphatase, Type I collagen and osteocalcin normalized to glyceraldehyde-3-phosphate dehydrogenase revealed different patterns of mRNA levels. High mRNA levels for Type I collagen showed that CFR-PEEK stimulated osteoblast differentiation, whilst injection molded unfilled PEEK was less differentiated. Machined unfilled PEEK had comparable message levels of bone matrix proteins as rough titanium. All material variants permitted a degree of mineralization. Scanning electron microscopy at 3 days and 2 weeks in differentiation medium showed that human osteoblasts were well spread on all the different substrates. The varied response reported here at different time points during the study suggests that material formulation (unfilled PEEK or CFR-PEEK), subjection to industrial processing, surface roughness and topography may all influence the cellular response of osteoblasts to PEEK. Thus, differences in human osteoblast responses were found to the various samples of PEEK, but implantable grade PEEK, in general, was comparable in vitro to the bone forming capacity of rough titanium.