Functionally distinct pericyte subsets differently regulate amyloid-ß deposition in patients with Alzheimer's disease.

Although the concept that the blood-brain barrier (BBB) plays an important role in the etiology and pathogenesis of Alzheimer's disease (AD) has become increasingly accepted, little is known yet about how it actually contributes. We and others have recently identified a novel functionally distinct subset of BBB pericytes (PCs). In the present study, we sought to determine whether these PC subsets differentially contribute to AD-associated pathologies by immunohistochemistry and amyloid beta (Aß) peptidomics. We demonstrated that a disease-associated PC subset (PC2) expanded in AD patients compared to age-matched, cognitively unimpaired controls. Surprisingly, we found that this increase in the percentage of PC2 (%PC2) was correlated negatively with BBB breakdown in AD patients, unlike in natural aging or other reported disease conditions. The higher %PC2 in AD patients was also correlated with a lower Aß42 plaque load and a lower Aß42:Aß40 ratio in the brain as determined by immunohistochemistry. Colocalization analysis of multicolor confocal immunofluorescence microscopy images suggests that AD patient with low %PC2 have higher BBB breakdown due to internalization of Aß42 by the physiologically normal PC subset (PC1) and their concomitant cell death leading to more vessels without PCs and increased plaque load. On the contrary, it appears that PC2 can secrete cathepsin D to cleave and degrade Aß built up outside of PC2 into more soluble forms, ultimately contributing to less BBB breakdown and reducing Aß plaque load. Collectively our data shows functionally distinct mechanisms for PC1 and PC2 in high Aß conditions, demonstrating the importance of correctly identifying these populations when investigating the contribution of neurovascular dysfunction to AD pathogenesis.

Factors Associated with Refractory Severe Hypertension in Patients with Preeclampsia.

OBJECTIVE: This study aimed to identify factors associated with refractory severe hypertension that does not resolve after an initial dose of antihypertensive medication in patients with preeclampsia. STUDY DESIGN: This was a retrospective study of all pregnant and postpartum individuals with a diagnosis of preeclampsia, superimposed preeclampsia, HELLP (hemolysis, elevated liver enzymes, low platelet) syndrome, or eclampsia who delivered at 22 weeks or greater at a single academic institution from 2010 to 2020. Inclusion criteria were patients with preeclampsia who developed severe hypertension (systolic pressure ≥160 mm Hg or diastolic pressure ≥110 mm Hg) and received antihypertensive medications for acute severe hypertension. We defined refractory severe hypertension as a systolic blood pressure of ≥160 mm Hg or a diastolic blood pressure of ≥110 mm Hg that did not improve after receiving the initial treatment. To evaluate for factors associated with refractory severe hypertension, we developed multivariable modified Poisson regression using all variables with p-value <0.1 on bivariable analysis and calculated adjusted relative risks (aRRs) with 95% confidence intervals (95% CIs). RESULTS: Of 850, 386 (45.4%) had refractory severe hypertension and 464 (54.6%) responded to the initial antihypertensive medications. Factors associated with refractory severe hypertension included higher body mass index (BMI), chronic hypertension, and higher systolic pressure. Every 5 kg/m2 increase in BMI was associated with a 7% increased risk of refractory severe hypertension (aRR = 1.07; 95% CI: 1.02-1.12). Every 10 mm Hg increase in systolic blood pressure was associated with a 10% increased risk of refractory severe hypertension (aRR = 1.10; 95% CI: 1.04-1.17). Chronic hypertension was associated with a 25% increased risk of refractory severe hypertension (aRR = 1.25; 95% CI: 1.01-1.56) in the diastolic pressure model. CONCLUSION: Refractory severe hypertension was associated with elevated BMI, chronic hypertension, and higher systolic blood pressure. KEY POINTS: · Risk factors for refractory severe hypertension are not well-known.. · Almost half of the patients had refractory severe hypertension.. · Higher BMI, chronic hypertension, and higher systolic pressure were the risk factors.. · These patients would require closer follow-up and prompt response to vital signs..

Understanding the Heterogeneity of Human Pericyte Subsets in Blood-Brain Barrier Homeostasis and Neurological Diseases.

Pericytes are increasingly recognized as being important in the control of blood-brain barrier permeability and vascular flow. Research on this important cell type has been hindered by widespread confusion regarding the phenotypic identity and nomenclature of pericytes and other perivascular cell types. In addition, pericyte heterogeneity and mouse-human species differences have contributed to confusion. Herein we summarize our present knowledge on the identification of pericytes and pericyte subsets in humans, primarily focusing on recent findings in humans and nonhuman primates. Precise identification and definition of pericytes and pericyte subsets in humans may help us to better understand pericyte biology and develop new therapeutic approaches specifically targeting disease-associated pericyte subsets.