P15. Human mesenchymal stem cells exhibit increased proliferation on rough titanium substrates

Abstract

BACKGROUND CONTEXT In the majority of orthopaedic surgeries, osseointegration between an implant and surrounding bone is crucial to achieving short- and long-term stability of the implant. Since an implant's surface properties directly influence the cellular response at the cell-material interface, a number of techniques exist to modify the surface characteristics of titanium (Ti)-based implants, with the objective of achieving improved osseointegration of the implant and surrounding bone. Many of these processes, such as grit-blasting and acid-etching, create a roughened surface in a random, poorly controlled manner. Conversely, subtractive laser-etching allows for controlled, intentionally designed micro- and nano-scale features to be imparted on a Ti surface. Biomimetic surface modifications can be created utilizing this technique. The biological reactions in response to a roughened, laser-etched Ti-based implant is not well understood. PURPOSE The objective of this study was to evaluate the effect of a roughened, laser-etched Ti6Al4V, substrate designed to mimic the trabecular-like structure of bone, on the cellular behavior of human bone-marrow derived mesenchymal stem cells (BM-MSCs). STUDY DESIGN/SETTING In vitro cell culture study. OUTCOME MEASURES Cell growth and proliferation rate over 7 days of culture were measured using the alamarBlue™ (AB) cell viability kit. At 4 hours, 3 days and 7 days of culture, the redox reaction, in which AB is reduced by the cells, was measured by absorbance readings at 570 and 600 nm. The percent of AB reduction has previously been shown to relate directly to the number of viable cells. METHODS Average 3D surface roughness (Sa) of the TAV substrates was characterized using 3D stereoscopic reconstruction of images from a scanning electron microscope. BM-MSCs were cultured for 7 days in a 24-well plate at a seeding density of 20,000 cells/well on the following substrates: tissue culture polysterene (TCPS), sTAV, rTAV (n=10 per group). Cells were given 4 hours to attach, after which cell media was changed and the TAV substrates were moved to a separate well plate to remove any unattached cells. At 4 hours, 3 days and 7 days of culture, the reduction percentage of AB was measured. The cell proliferation rate was calculated as the rate of change in average AB reduction from the 4 hour to 7 day time points. RESULTS Theaverage roughness of the sTAV and rTAV substrates were 0.36±0.06 μm and 36.3±1.5 μm, respectively. Significantly more AB reduction was found with rTAV substrates compared to sTAV at all time points (p CONCLUSIONS This study found increased cell proliferation on a rough, laser-etched TAV surface designed specifically to mimic the surface morphology of bone when compared to a smooth TAV substrate. This data confirms that surface roughness was increased in a controlled manner, by orders of magnitude, through subtractive laser-etching. It was found that this technique was successful in modifying cellular behavior and resulted in increased BM-MSC proliferation. Future work should investigate how laser-etched rTAV influences cell phenotype, as well as the short- and long-term cellular response. FDA DEVICE/DRUG STATUS Unavailable from authors at time of publication.