Canine leptomeningeal organ culture: a new experimental model for cerebrovascular beta-amyloidosis

Human cerebral collateral arteriole function in subjects with normal cognition, mild cognitive impairment, and dementia

Clinical and preclinical studies have suggested a link between cardiovascular disease and dementia disorders, but the role of the collateral brain circulation in cognitive dysfunction remains unknown. We aimed to test the hypothesis that leptomeningeal arteriole (LMA) function and response to metabolic stressors differ among subjects with dementia, mild cognitive impairment (MCI), and normal cognition (CN). After rapid autopsy, LMAs were isolated from subjects with CN ( n = 10), MCI ( n = 12), or dementia [ n = 42, Alzheimer's disease (AD), vascular dementia (VaD), or other dementia], and endothelial and smooth muscle-dependent function were measured at baseline and after exposure to β-amyloid (2 μM), palmitic acid (150 μM), or medin (5 μM) and compared. There were no differences among the groups in baseline endothelial function (maximum dilation to acetylcholine, CN: 74.1 ± 9.7%, MCI: 67.1 ± 4.8%, AD: 74.7 ± 2.8%, VaD: 72.0 ± 5.3%, and other dementia: 68.0 ± 8.0%) and smooth muscle-dependent function (CN: 93.4 ± 3.0%, MCI: 83.3 ± 4.1%, AD: 91.8 ± 1.7%, VaD: 91.7 ± 2.4%, and other dementia: 87.9 ± 4.9%). There was no correlation between last cognitive function score and baseline endothelial or smooth muscle-dependent function. LMA endothelial function and, to a lesser extent, smooth muscle-dependent function were impaired posttreatment with β-amyloid, palmitic acid, and medin. Posttreatment LMA responses were not different between subjects with CN/MCI vs. dementia. Baseline responses and impaired vasoreactivity after treatment with metabolic stressors did not differ among subjects with CN, MCI, and dementia. The results suggest that the cognitive dysfunction in dementia disorders is not attributable to differences in baseline brain collateral circulation function but may be influenced by exposure of the vasculature to metabolic stressors.

Design and validation of a novel splashing bioreactor system for use in mitral valve organ culture

Previous research in our lab suggested that heart valve tissues cultured without mechanical stimulation do not retain their in vivo microstructure, i.e., cell density decreased within the deep tissue layers and increased at the periphery. In this study, a splashing rotating bioreactor was designed to apply mechanical stimulation to a mitral valve leaflet segment. Porcine valve segments (n = 9-10 per group) were cultured in the bioreactor for 2 weeks (dynamic culture), negative controls were cultured without mechanical stimulation (static culture), and baseline controls were fresh uncultured samples. Overall changes in cellularity and extracellular matrix (ECM) structure were assessed by H&E and Movat pentachrome stains. Tissues were also immunostained for multiple ECM components and turnover mediators. After 2 weeks of culture, proliferating cells were distributed throughout the tissue in segments cultured in the bioreactor, in contrast to segments cultured without mechanical stimulation. Most ECM components, especially collagen types I and III, better maintained normal expression patterns and magnitudes (as found in baseline controls) over 2 weeks of dynamic organ culture compared to static culture. Lack of mechanical stimulation changed several aspects of the tissue microstructure, including the cell distribution and ECM locations. In conclusion, mechanical stimulation by the bioreactor maintained tissue integrity, which will enable future in vitro investigation of mitral valve remodeling.