Porous tantalum stimulates osteogenesis in osteoblast cultures from elderly patients

Previous work in our lab demonstrated that in vitro responses of human osteoblasts to orthopaedic and dental materials depend on patients' sex and age. Recently developed porous tantalum (Ta) and fiber-mesh Ti-6Al-4V (Ti) (Zimmer, Warsaw, IN) demonstrate improved biomechanical properties and in vivo biocompatibility, however there is no sex- and age-dependent study on these materials. Objective: compare the phenotypic expression of human osteoblasts from young and old female patients to Ta and Ti. Methods: Osteoblasts from young (<45 yrs) and old (>60 yrs) orthopaedic female patients were cultured on Ti and Ta discs, and control tissue-culture plastic (P). Cell adhesion at 4 h, proliferation at 48 h, and calcification, RT-PCR and phalloidin assays at 3 weeks were performed. Results: 76%, 50% and 62% of osteoblasts from young patients adhered to Ta, Ti and P, respectively, compared to 58%, 40% and 43% of osteoblasts from old patients. Osteoblasts from young and old patients demonstrated more adhesion to Ta than to Ti (p = 0.000036 and 0.0001, respectively). DNA synthesis was higher on Ta compared to Ti for osteoblasts from both young and old patients (4 and 6 times greater and p = 0.00016 and 0.00026, respectively). Calcium content was higher on Ta compared to Ti for young and old patients (p = 0.03 and 0.004, respectively). RT-PCR showed similar levels of Type I collagen and alkaline phosphatase on all substrates. Osteocalcin levels were significantly lower on Ta and Ti than P. Phalloidin labeling of the actin-based cytoskeleton demonstrated cuboidal cells on Ta compared to elongated cells on Ti. Conclusions: The ability of porous tantalum to stimulate osteoblast adhesion, proliferation and mineralization from older patients suggests that it is a promising implant material, especially in patients with reduced capacity to make bone.

Supported by Ruth Jaclkson Orthopaedic Society Grant to Dr. Hakim-Zargar.