Effects of setting bone cement on tissue-engineered bone graft: a potential barrier to clinical translation?

BACKGROUND Strategies to improve mechanical strength, neovascularization, and the regenerative capacity of allograft include both the addition of skeletal stem cells and the investigation of novel biomaterials to reduce and ultimately obviate the need for allograft altogether. Use of bone cement is a common method of stabilizing implants in conjunction with impacted allograft. Curing cement, however, can reach temperatures in excess of 70°C, which is potentially harmful to skeletal stem cells. The aim of this study was to investigate the effects of setting bone cement on the survival of human adult skeletal stem cells within tissue-engineered allograft and a novel allograft substitute. METHODS Milled allograft and a polymer graft substitute were seeded with skeletal stem cells, impacted into a graduated chamber, and exposed to curing bone cement. Sections were removed at 5-mm increments from the allograft-cement interface. A quantitative WST-1 assay was performed on each section as a measure of remaining cell viability. A second stage of the experiment involved assessment of methods to potentially enhance cell survival, including pretreating the allograft or polymer by either cooling to 5°C or coating with 1% Laponite, or both. RESULTS There was a significant drop in cellular activity in the sections taken from within 0.5 cm of the cement interface in both the allograft and the polymer (p < 0.05), although there was still measurable cellular activity. Pretreatment methods did not significantly improve cell survival in any group. CONCLUSIONS While the addition of bone cement reduced cellular viability of tissue-engineered constructs, this reduction occurred only in close proximity to the cement and measurable numbers of skeletal stem cells were observed, confirming the potential for cell population recovery.