Transport-related effects on intrinsic and synaptic properties of human cortical neurons: A comparative study.

Transporting human brain tissue blocks or slices from the operating theatre or on-site laboratory to an off-site laboratory may affect sample integrity for electrophysiological studies. In this study, we investigated how a 30-40 min transport influenced the intrinsic, synaptic and morphological properties of human cortical neurons. Electrophysiological recordings were performed on layer 2/3 (L2/3) pyramidal cells and fast-spiking (FS) interneurons from acute human cortical slices (n = 200 neurons from 32 surgeries, in which 112 neurons passed quality control for further analyses). Recordings were performed on-site at RWTH Aachen University Hospital and off-site at the Research Centre Jülich, which are approximately 40 km apart. Action potential (AP) firing patterns remained largely preserved across both recording sites, but several differences were observed. Off-site recorded pyramidal cells showed a depolarised resting membrane potential and a lowered rheobase current. In off-site recorded FS interneurons, we found a narrower AP half-width and an increased AP amplitude, suggesting altered ion channel kinetics and/or neuromodulatory environment. Additionally, a significant reduction in large rhythmic depolarisations and the amplitudes of spontaneous excitatory postsynaptic potentials in off-site recorded FS interneurons indicated an altered synaptic efficacy. Although overall dendritic architecture was preserved, the dendritic spine densities in apical oblique and apical tuft dendrites of off-site recorded pyramidal cells were also reduced. These findings emphasise the need for optimised transport conditions to preserve synaptic integrity, network activity and neuronal morphology. Standardised protocols are crucial for ensuring reliable and reproducible results in studies of human cortical function and structure. KEY POINTS: Effects of transportation on neuronal properties: Brief transportation of human brain tissue retains many key neuronal properties, while still exhibiting measurable alterations in certain intrinsic, synaptic and morphological properties. Mechanical stress and neuromodulator dysfunction may underlie alterations: These changes are likely due to the combined effects of mechanical stress and altered neuromodulator signalling during transportation. Advancing understanding of cortical function and structure: This research provides valuable insights into the impact of transportation on human brain tissue, advancing our understanding of cortical function and structure and highlighting the importance of optimising transport protocols to preserve tissue integrity and neuronal function.