Tissue oxygen partial pressure as a viability metric for ex vivo brain tissue slices.

BACKGROUND

Despite the prevalent use of the ex vivo brain slice preparation in neurophysiology research, a reliable method for judging tissue viability - and thus suitability of a slice for inclusion in an experiment - is lacking. The utility of indirect electrophysiological measures of tissue health is model-specific and needs to be used cautiously. In this study, we verify a more direct test of slice viability, based on tissue oxygen consumption rate.

NEW METHOD

We hypothesised that the minimum intra-slice partial pressure of oxygen (pO) would correlate with tissue oxygen consumption rate, providing an accessible method for reliably assessing tissue viability status. Using mouse brain cortex slices, we measured tissue oxygen consumption rate using a Fick's law diffusion-consumption model applied to full intra-tissue pO profiles and compared this to pO and 2,3,5-triphenol tetrazolium chloride (TTC) viability staining.

RESULTS

Tissue pO correlated strongly with oxygen consumption rate in both neurophysiological active and quiescent tissue (in "no-magnesium" and "normal" artificial cerebrospinal fluid, respectively) (R =49.7% and 42.1%, respectively). Both correlated with TTC viability stain. Oxygen consumption rate was positively related to the frequency of seizure-like event activity in no-magnesium artificial cerebrospinal fluid (R = 44.8%).

COMPARISON WITH EXISTING METHODS

While measurement of tissue oxygen levels and oxygen consumption is not new, intra-tissue pO is a novel approach to assess brain slice viability.

CONCLUSION

The results confirm that tissue oxygen minimum pO is a robust metric for estimating tissue viability status - the lower the pO, the healthier the tissue.