A neurovascular component of futile reperfusion after ischemic stroke

An acute ischemic stroke (AIS) is a devastating event that hit each year millions of people and one third of them die. Although macrovascular recanalization strategies have greatly revolutionised stroke management, microvascular blood flow to the brain may still be impaired. Half of recanalized patients have neurological deficits causing them to be dependent in daily living and the futile reperfusion can be the cause. Large infarcts and severe neurological deficits can develop despite recanalized and “open” large intracerebral vessels. On a microvascular level, this may be explained by pre-capillary vasospasm affecting blood flow and its pattern. The mechanism behind this ischemia-induced constriction of pericytes and pre-capillary arterioles is unknown. We propose that this is a result of unconventional mechanisms that are potentiated by ischemia and aim to characterize them. We hypothesize that;

• Ischemia-induced factors sensitize the contractile machinery of pericytes and smooth muscle cells to intracellular calcium. We suggest the involvement of Src kinase and phospholipase C pathways, as well as the voltage-gated calcium channels.
• Endothelial signaling via the inward-rectifying potassium channels keeps pre-capillary sphincters open and enables an optimal perfusion. Thus, optimization of this signaling will improve cerebral perfusion.
• Red blood cells are an important regulator of cerebral microcirculation, because their rheological properties and as an important source of NO. These modify under ischemic conditions suggesting a potential intervention target as an ischemic conditioning.

Pharmacological tools to manipulate with these pathways are available, but detailed molecular characterization of potentially involved signalling pathways is necessary for specific and targeted implementation to AIS therapy.  
After having resolve the macrovascular problem in AIS treatment, we need mechanistic insight behind futile reperfusion on the microvascular level to suggest therapeutic strategies to protect the brain against ischemic damage and to improve stroke outcome. Addressing the microvasculature after thrombectomy signifies a new paradigm in AIS treatment.
This is translational research that is based on various rodent models of AIS but is aligned with the studies from our clinical collaborators and thus, includes patient data. The comprehensive experimental protocols include spatial omics analyses, expression studies, pharmacological interventions in awake murine models. State-of-art brain imaging, e.g., laser speckle contrast imaging and two-photon microscopy, is a core technique in the project. A broad collaboration with the local hospital and leading international experts ensures the success of this project.

The candidate must hold PhD degree in natural science or medicine. Experience within cardiovascular physiology, molecular biology, neuroscience and/or transport physiology will be an advantage. The candidate should preferably have experience with:

• chronic animal experimental models and animal surgery, and hold the FELASA certificate
• microdissection and organ bath studies
• brain imaging
• Matlab and R software
• expression analyses, including Western blot, immunohistochemistry and omics.

The group has a long-standing expertise in animal experimental model research combining the neurological and cardiovascular abnormalities, and in studying their comorbidities. In vivo assessment of blood pressure and organ perfusion control in anaesthetized and awake rodents, organ bath experiments and expression studies are ongoing in the group. The host group has a close collaboration with several membrane transport and neuroscience groups at the Department and in the University Hospital. Specifically, the group expertise include;

• Laser Speckle Contrast Imaging in awake and anaesthetized rodents
• Brain slices to assess parenchymal arteriole diameter and intracellular calcium responses to neuronal excitation
• Telemetry: blood pressure, blood glucose, biopotentials (ECG, EEG), activity and body temperature
• Metabolic studies, e.g., glucose/insulin tolerance test and oximetry (Oroboros).
• Ischemic stroke, chronic stress, migraine, hypertension and diabetes rodent models.
• Patch clamp, sharp electrode membrane potential and ion-selective electrode measurements.
• Small artery myography and Langendorff heart preparation.
• Intracellular Ca2+, H+ imaging with ion selective dyes.
• Protein and PCR lab.
• Spatial transcriptomics and proteomics.