Screening of Neuroprotective Drugs

Example for the Use of Pathological Cell Stretchers:

Assessing Long Term Potentiation in Organotypic Hippocampal Slice Cultures (OHSCs) after TBI

Organotypic hippocampal slice culture (OHSC) models maintain the structural integrity of the hippocampus and provide a system to examine interactions between various cell types. Long-term potentiation (LTP), which serves as an in vitro cellular model for learning and memory through synaptic plasticity, is diminished after repeated mild injuries. This research emphasizes the critical role of using stretchable microelectrode arrays (sMEAs) within the MEASSuRE platform to identify LTP impairments—particularly the decline in synaptic plasticity—following traumatic brain injury (TBI). The application of this system for neuroprotective drug screening is promising, as it enables researchers to assess how various compounds could mitigate the observed deficits in synaptic plasticity. Drug screening in this context allows for the testing of potential neuroprotective drugs aimed at alleviating LTP impairment.

After injury, induction of LTP through high frequency stimulation does not increase magnitude of response that is seen in sham injured OHSCs

Methods

OHSCs obtained from the hippocampi of P8-10 Sprague-Dawley rats were placed on stretchable microelectrode arrays (sMEAs) and maintained in an incubator for at least 10 days. Spontaneous activity and stimulus response (SR) curves were recorded using the Electrophysiology Module of the MEASSuRE system. Each slice (one per sMEA) was then exposed to a moderate biaxial stretch injury (average strain: 16.2%, strain rate: 16.8 s-1) using the Mechanics Module of MEASSuRE, while control slices underwent a sham injury. Actual tissue strains were verified through high-speed video recordings using the Imaging Module of MEASSuRE. Twenty-four hours post-injury, a second set of recordings for spontaneous activity and SR curves was performed. To assess plasticity, long-term potentiation (LTP) was induced by delivering 3 rounds of 100 pulses at 100 Hz, separated by 10-second intervals, applied once at i50. LTP percentage values were determined by measuring the magnitude of responses 50-60 minutes after plasticity induction, normalized against the last 10 minutes of baseline activity.

Results

There was no significant change in the overall firing rate, spontaneous activity magnitude, SR parameters, or the average number of bursts before and after the injury. However, a notable reduction in the spike length of the average burst was observed following the injury (7.78 ± 0.71 vs. 5.94 ± 0.16, N = 10-12 slices, *p<0.05). LTP deficits 24 hours post-injury were pronounced (48.06 ± 13.50 vs. -3.62 ± 2.79%, N = 4 slices, **p<0.01, see Figure) when compared to baseline measurements.

Conclusions

Stretchable microelectrode arrays (sMEAs) offer a distinctive approach to monitor electrical activity within the same OHSCs both before and after injury. In this instance, significant LTP deficits were observed post-injury, demonstrating the potential of this model for evaluating therapeutic interventions for TBI in vitro. This model also holds significant promise for neuroprotective drug screening applications, where it can serve as an effective tool to assess the efficacy of potential neuroprotective drugs in mitigating synaptic damage. Future studies could focus on expanding the use of this platform in drug screening for other neurological disorders, emphasizing its versatility in identifying beneficial treatments.