Inflammation Increases Neuronal Sensitivity to General Anesthetics.

BACKGROUND: Critically ill patients with severe inflammation often exhibit heightened sensitivity to general anesthetics; however, the underlying mechanisms remain poorly understood. Inflammation increases the number of γ-aminobutyric acid type A (GABAA) receptors expressed on the surface of neurons, which supports the hypothesis that inflammation increases up-regulation of GABAA receptor activity by anesthetics, thereby enhancing the behavioral sensitivity to these drugs. METHODS: To mimic inflammation in vitro, cultured hippocampal and cortical neurons were pretreated with interleukin (IL)-1ß. Whole cell patch clamp methods were used to record currents evoked by γ-aminobutyric acid (GABA) (0.5 µM) in the absence and presence of etomidate or isoflurane. To mimic inflammation in vivo, mice were treated with lipopolysaccharide, and several anesthetic-related behavioral endpoints were examined. RESULTS: IL-1ß increased the amplitude of current evoked by GABA in combination with clinically relevant concentrations of either etomidate (3 µM) or isoflurane (250 µM) (n = 5 to 17, P < 0.05). Concentration-response plots for etomidate and isoflurane showed that IL-1ß increased the maximal current 3.3-fold (n = 5 to 9) and 1.5-fold (n = 8 to 11), respectively (P < 0.05 for both), whereas the half-maximal effective concentrations were unchanged. Lipopolysaccharide enhanced the hypnotic properties of both etomidate and isoflurane. The immobilizing properties of etomidate, but not isoflurane, were also increased by lipopolysaccharide. Both lipopolysaccharide and etomidate impaired contextual fear memory. CONCLUSIONS: These results provide proof-of-concept evidence that inflammation increases the sensitivity of neurons to general anesthetics. This increase in anesthetic up-regulation of GABAA receptor activity in vitro correlates with enhanced sensitivity for GABAA receptor-dependent behavioral endpoints in vivo.

Scaffold-free cartilage tissue engineering with a small population of human nasoseptal chondrocytes.

OBJECTIVE: Cartilage tissue engineering is a promising approach to provide suitable materials for nasal reconstruction; however, it typically requires large numbers of cells. We have previously shown that a small number of chondrocytes cultivated within a continuous flow bioreactor can elicit substantial tissue growth, but translation to human chondrocytes is not trivial. Here, we aimed to demonstrate the application of the bioreactor to generate large-sized tissues from a small population of primary human nasoseptal chondrocytes. STUDY DESIGN: Experimental study. METHODS: Chondrocytes were cultured in the bioreactor using different medium compositions, with varying amounts of serum and with or without growth factors. Resulting engineered tissues were analyzed for physical properties, biochemical composition, tissue microstructure, and protein localization. RESULTS: Bioreactor-cultivated constructs grown with serum and growth factors (basic fibroblast growth factor and transforming growth factor beta 2) had greater thickness, as well as DNA and glycosaminoglycan (GAG) contents, compared to low serum and no growth factor controls. These constructs also showed the most intense proteoglycan and collagen II staining. CONCLUSION: The combination of bioreactor conditions, serum, and growth factors allowed the generation of large, thick scaffold-free human cartilaginous tissues that resembled the native nasoseptal cartilage. There also may be implications for patient selection in future clinical applications of these engineered tissues because their GAG content decreased with donor age. LEVEL OF EVIDENCE: NA. Laryngoscope, 127:E91-E99, 2017.