Comprehensive analysis of local anesthetics affecting adipose stem cells, in vitro.

BACKGROUND: Fat grafting represe nts a common technique to treat volume deficits, e.g. for breast augmentation. Therein, adipose stem cells (ASCs) hold a great regenerative capacity, because of their differentiation capability and, more importantly, their secretory activity. Thus, the survival of ASCs is of great significance during perioperative harvesting. Various local anesthetics are commonly applied during fat grafting procedures. Historically, these substances are known to impair cellular viability, which would affect graft survival and its final outcome. However, the exact extent of local anesthetics' impact on ASC biology is rather unknown.

METHODS: We analyzed the short- and long-term effects of four different local anesthetics, i.e., lidocaine, mepivacaine, ropivacaine, bupivacaine at increasing concentrations (0.1 nM - 10 mM) on primary human ASC proliferation and metabolic activity, evaluated by crystal violet staining and the PrestoBlue assay, respectively. Trilinear differentiation was assessed by OilRedO stain to measure adipogenesis, SafraninO and cresolphthalein labeling was used for chondrogenic and osteogenic differentiation. Supernatants were used to analyze cytokine (IL-6/ -8, VEGF, HGF) secretion by ELISA.

RESULTS: Bupivacaine at >100 µM demonstrated the strongest anti-proliferative short- and long-term effects, whereas lidocaine and ropivacaine did not affect cell numbers. Mepivacaine evoked reciprocal results regarding cell count at >1 mM. Each compound impaired differentiation into the adipogenic, chondrogenic and osteogenic lineage. Furthermore, secretion of HGF and IL-8 was significantly reduced by local anesthetic exposure, whereas the levels restored after substances were washed out.

CONCLUSION: Depending on our in vitro data, lidocaine, mepivacaine and ropivacaine could be applied at concentrations of 1 - 10 mM without affecting ASC survival. Contrariwise, bupivacaine at concentrations >100 µM should be administered with great caution. However, the differentiation of ASCs and the ASC's secretome might already be decreased by each local anesthetic at 1 mM.