Localization of the hydrogen sulfide and oxytocin systems at the depth of the sulci in a porcine model of acute subdural hematoma

Abstract

In the porcine model discussed in this review, the acute subdural hematoma was induced by subdural injection of autologous blood over the left parietal cortex, which led to a transient elevation of the intracerebral pressure, measured by bilateral neuromonitoring. The hematoma-induced brain injury was associated with albumin extravasation, oxidative stress, reactive astrogliosis and microglial activation in the ipsilateral hemisphere. Further proteins and injury markers were validated to be used for immunohistochemistry of porcine brain tissue. The cerebral expression patterns of oxytocin, oxytocin receptor, cystathionine-γ-lyase and cystathionine-β-synthase were particularly interesting: these four proteins all co-localized at the base of the sulci, where pressure-induced brain injury elicits maximum stress. In this context, the pig is a very relevant translational model in contrast to the rodent brain. The structure of the porcine brain is very similar to the human: the presence of gyri and sulci (gyrencephalic brain), white matter to grey matter proportion and tentorium cerebelli. Thus, pressure-induced injury in the porcine brain, unlike in the rodent brain, is reflective of the human pathophysiology.

Keywords: animal modeling; brain edema; cystathionine-β-synthase; cystathionine-γ-lyase; gyrencephalic brain; immunohistochemistry; intensive care unit; large animal model; neuromonitoring; oxytocin receptor.

Figure 1

Pressure distribution in the cerebral cortex after ASDH. (A) In the lissencephalic cerebral cortex, pressure increase in response to ASDH is distributed evenly. (B) In the gyrencephalic cerebral cortex, pressure increase in response to ASDH is conducted along the sulci, with maximum pressure at the base of the sulci. The size of the lissencephalic brain in comparison to the gyrencephalic brain is overestimated. ASDH: Acute subdural hematoma.

Figure 2

Schematic depiction of the brain within the skull. (A) In the rodent brain, the vestigial tentorium cerebelli can mitigate an elevation of intracranial pressure. (B) In the human (and porcine) brain, elevated intracranial pressure is confined to the cerebrum by the rigid tentorium cerebelli. The size of the rodent brain in comparison to the human brain is overestimated.

Figure 3

Schematic depiction of animal intensive care unit concepts. (A) The mouse intensive care unit (MICU) allows for monitoring and resuscitation of the animal during critical illness studies. A. mes. sup.: Superior mesenteric artery. Reprinted with permission from Guillon et al., 2019 (creative commons license, https://creativecommons.org/licenses/by/4.0/). (B) Additional multimodal brain monitoring in the acute subdural hematoma (ASDH) model in the pig intensive care unit (PICU) comprising the same ICU setup as the MICU. Reprinted with permission from Datzmann et al., 2021 (reprinted with permission from the American Association of Neurological Surgeons).

Figure 4

Protein expression in the gyrencephalic cerebral cortex after ASDH. Albumin extravasation, nitrotyrosine (Nitro.) formation and reactive astrogliosis were observed around the ASDH induction site (Datzmann et al., 2021). OT, OTR, CSE, CBS co-localized around the base of the sulci, where the maximum pressure-induced injury occurs (Denoix et al., 2020). In the parenchyma, OT, OTR and CBS expression were elevated in the injured compared to the contralateral hemisphere. In the contralateral hemisphere, OTR and CSE expression were constitutive (Denoix et al., 2020). GFAP expression was limited to the white matter, albumin extravasation and nitrotyrosine formation were not detected (Datzmann et al., 2021). ASDH: Acute subdural hematoma; CBS: cystathionine-β-synthase; CSE: cystathionine-γ-lyase; GFAP: glial fibrillary acidic protein; OT: oxytocin; OTR: oxytocin receptor.