In vitro and in vivo osteogenic cell response to high temperature exposure

Aim. To evaluate the response of mesenchymal stromal/stem cells (MSCs) in vitro and the status of bone cells (osteoblasts, osteocytes) during regeneration of the femoral bone after local thermoablation at 55–60 °C. Materials and methods. Morphology and viability (MTT assay) of human adipose tissue-derived MSCs were analyzed after incubation at 37 °C or 56 °C for 0–60 minutes. In vivo , a heating cuff was applied to the femur of anesthetized rabbits, and intraoperative thermoablation was performed for 30 minutes (bone marrow canal temperature: 55–60 °C). Bone tissue was histologically examined (hematoxylin – eosin and Einarson staining) immediately and 14 days post-treatment. Quantitative morphometry was implemented in ImageJ, with subsequent statistical analysis performed in R. Results . In vitro , signs of massive MSC death were observed after 15 minutes of heating; at 30 minutes, viable fibroblast-like cells were nearly absent. In vivo , local thermoablation caused direct death of osteoblasts and osteocytes, evidenced by morphological signs of apoptosis and necrosis, as well as impaired DNA/RNA synthesis. Morphological and molecular markers of cellular damage significantly increased by day 14 post-treatment. Conclusion. Moderate thermoablation (55–60 °C) exerts significant direct and delayed damaging effects on osteogenic cells, from stem to mature forms. These findings are relevant for combined treatment of tumor and metastatic bone lesions.