Bupivacaine, ropivacaine, and morphine: comparison of toxicity on human hamstring-derived stem/progenitor cells

Bupivacaine, ropivacaine, and morphine are commonly administered intraarticularly after anterior cruciate ligament (ACL) reconstruction. However, their effects on human tendon stem/progenitor cells (TSPC) have not been studied. Therefore, this study investigates the cytotoxicity of these analgetics on TSPC. Cells were isolated from human hamstring grafts of 3 female (age 15, 16 and 59) and 2 male patients (age 16 and 47). Cells were incubated using 0.5% bupivacaine, 0.5/0.75% ropivacaine, and 0.025% morphine. Cell viability was assessed after 0.5, 2, and 6 h using live/dead assay. Metabolic activity and apoptosis were measured by WST- and Annexin-V-FACS-assay after 2 h. Cell viability remained unchanged after 0.5 h in all groups, while treatment with bupivacaine and 0.5/0.75% ropivacaine resulted in a complete cell loss after 6 h. Contrarily, morphine showed no cytotoxic effect. Cell viability and metabolism were significantly reduced after treatment with bupivacaine (22.1; 8.3%) and 0.75% ropivacaine (56.5; 23.8%), while 0.5% ropivacaine and morphine showed no significant difference compared with controls. Apoptosis was significantly induced after incubation with bupivacaine (58.1%) and 0.75% ropivacaine (26.2%), whereas 0.5% ropivacaine only led to a slight induction compared with morphine and controls. Clinically administered concentrations of bupivacaine (0.5%) and ropivacaine (0.75%) have a significant cytotoxic effect on human TSPC in vitro, while ropivacaine in a concentration of 0.5% has a mild but not significant effect on apoptosis and cell metabolism. In contrast, morphine does not affect cell survival, metabolism, or apoptosis. Knowing that morphine provides comparable to even prolonged pain reduction after ACL reconstruction, the presented in vitro study suggests morphine as a potentially less toxic analgetic drug for intraarticular application in clinical practice.