Tissue response to a novel bone adhesive implanted subcutaneously in rats: A histological and gene expression analysis

Median sternotomy provides access to the heart and surrounding valves for cardiothoracic surgery. However, complications arise such as micro-motion and separation between the two sternal halves. To prevent these complications, the use of a bone adhesive has been proposed to augment the mechanical union of the two sternal halves when combined with wire cerclage. Our group has developed a bone adhesive for sternal fixation, utilizing a glass polyalkenoate cement (GPC) based on a zinc silicate ionomeric glass (mole fraction: SiO2:0.48, ZnO:0.36, CaO:0.12, SrO:0.04). Here we present the first soft-tissue biological safety assessment of this novel Sr/Zn-GPC, where we implanted the material subcutaneously in rats for 6 and 12 weeks. Polymethyl-methacrylate (PMMA) bone cement was used as a baseline control with respect to inflammation and biocompatibility. Histological assessment revealed no adverse tissue reaction nor ectopic bone formation in response to the novel material. Additionally, relative expression of pro-inflammatory and osteogenic genes (Col1a1, SOX9, Runx2, IL-1, IL-6, and TNF-alpha) was assessed in the tissue surrounding implants and revealed no significant differences in expression between the Sr/Zn-GPC and PMMA implants.