Pericyte Contractile Responses to Endothelin-1 and Aβ Peptides: Assessment by Electrical Impedance Assay

Human iPSC-derived pericyte-like cells carrying APP Swedish mutation overproduce beta-amyloid and induce cerebral amyloid angiopathy-like changes

BACKGROUND

Patients with Alzheimer's disease (AD) frequently present with cerebral amyloid angiopathy (CAA), characterized by the accumulation of beta-amyloid (Aβ) within the cerebral blood vessels, leading to cerebrovascular dysfunction. Pericytes, which wrap around vascular capillaries, are crucial for regulating cerebral blood flow, angiogenesis, and vessel stability. Despite the known impact of vascular dysfunction on the progression of neurodegenerative diseases, the specific role of pericytes in AD pathology remains to be elucidated.

METHODS

To explore this, we generated pericyte-like cells from human induced pluripotent stem cells (iPSCs) harboring the Swedish mutation in the amyloid precursor protein (APPswe) along with cells from healthy controls. We initially verified the expression of classic pericyte markers in these cells. Subsequent functional assessments, including permeability, tube formation, and contraction assays, were conducted to evaluate the functionality of both the APPswe and control cells. Additionally, bulk RNA sequencing was utilized to compare the transcriptional profiles between the two groups.

RESULTS

Our study reveals that iPSC-derived pericyte-like cells (iPLCs) can produce Aβ peptides. Notably, cells with the APPswe mutation secreted Aβ1-42 at levels ten-fold higher than those of control cells. The APPswe iPLCs also demonstrated a reduced ability to support angiogenesis and maintain barrier integrity, exhibited a prolonged contractile response, and produced elevated levels of pro-inflammatory cytokines following inflammatory stimulation. These functional changes in APPswe iPLCs correspond with transcriptional upregulation in genes related to actin cytoskeleton and extracellular matrix organization.

CONCLUSIONS

Our findings indicate that the APPswe mutation in iPLCs mimics several aspects of CAA pathology in vitro, suggesting that our iPSC-based vascular cell model could serve as an effective platform for drug discovery aimed to ameliorate vascular dysfunction in AD.

Pericytes in Alzheimer's disease: Key players and therapeutic targets

Alzheimer's disease (AD) is a devastating neurodegenerative disorder that leads to progressive cognitive decline and neuropathological changes. Pericytes, which are vessel mural cells on the basement membrane of capillaries, play a crucial role in regulating cerebrovascular functions and maintaining neurovascular unit integrity. Emerging research substantiates the involvement of pericytes in AD. This review provides a comprehensive overview of pericytes, including their structure, origin, and markers and various functions within the central nervous system. Emphatically, the review explores the intricate mechanisms through which pericytes contribute to AD, including their interactions with amyloid beta and apolipoprotein E, as well as various signaling pathways. The review also highlights potential for targeted pericyte therapy for AD, with a focus on stem cell therapy and drug treatments. Future research directions include the classification of pericyte subtypes, studies related to aging, and the role of pericytes in exosome-related mechanisms in AD pathology. In conclusion, this review consolidates current knowledge on the pivotal roles of pericytes in AD and their potential as therapeutic targets, providing valuable insights for future research and clinical interventions aimed at addressing the impact of AD on patients' lives.

Pericyte in retinal vascular diseases: A multifunctional regulator and potential therapeutic target

Retinal vascular diseases (RVDs), in particular diabetic retinopathy, retinal vein occlusion, and retinopathy of prematurity, are leading contributors to blindness. The pathogenesis of RVD involves vessel dilatation, leakage, and occlusion; however, the specific underlying mechanisms remain unclear. Recent findings have indicated that pericytes (PCs), as critical members of the vascular mural cells, significantly contribute to the progression of RVDs, including detachment from microvessels, alteration of contractile and secretory properties, and excessive production of the extracellular matrix. Moreover, PCs are believed to have mesenchymal stem properties and, therefore, might contribute to regenerative therapy. Here, we review novel ideas concerning PC characteristics and functions in RVDs and discuss potential therapeutic strategies based on PCs, including the targeting of pathological signals and cell-based regenerative treatments.

Induced pluripotent stem cell derived pericytes respond to mediators of proliferation and contractility

BACKGROUND

Pericytes are multifunctional contractile cells that reside on capillaries. Pericytes are critical regulators of cerebral blood flow and blood-brain barrier function, and pericyte dysfunction may contribute to the pathophysiology of human neurological diseases including Alzheimers disease, multiple sclerosis, and stroke. Induced pluripotent stem cell (iPSC)-derived pericytes (iPericytes) are a promising tool for vascular research. However, it is unclear how iPericytes functionally compare to primary human brain vascular pericytes (HBVPs).

METHODS

We differentiated iPSCs into iPericytes of either the mesoderm or neural crest lineage using established protocols. We compared iPericyte and HBVP morphologies, quantified gene expression by qPCR and bulk RNA sequencing, and visualised pericyte protein markers by immunocytochemistry. To determine whether the gene expression of neural crest iPericytes, mesoderm iPericytes or HBVPs correlated with their functional characteristics in vitro, we quantified EdU incorporation following exposure to the key pericyte mitogen, platelet derived growth factor (PDGF)-BB and, contraction and relaxation in response to the vasoconstrictor endothelin-1 or vasodilator adenosine, respectively.

RESULTS

iPericytes were morphologically similar to HBVPs and expressed canonical pericyte markers. However, iPericytes had 1864 differentially expressed genes compared to HBVPs, while there were 797 genes differentially expressed between neural crest and mesoderm iPericytes. Consistent with the ability of HBVPs to respond to PDGF-BB signalling, PDGF-BB enhanced and a PDGF receptor-beta inhibitor impaired iPericyte proliferation. Administration of endothelin-1 led to iPericyte contraction and adenosine led to iPericyte relaxation, of a magnitude similar to the response evoked in HBVPs. We determined that neural crest iPericytes were less susceptible to PDGFR beta inhibition, but responded most robustly to vasoconstrictive mediators.

CONCLUSIONS

iPericytes express pericyte-associated genes and proteins and, exhibit an appropriate physiological response upon exposure to a key endogenous mitogen or vasoactive mediators. Therefore, the generation of functional iPericytes would be suitable for use in future investigations exploring pericyte function or dysfunction in neurological diseases.

The contribution of β-amyloid, Tau and α-synuclein to blood-brain barrier damage in neurodegenerative disorders

Central nervous system (CNS) accumulation of fibrillary deposits made of Amyloid β (Aβ), hyperphosphorylated Tau or α-synuclein (α-syn), present either alone or in the form of mixed pathology, characterizes the most common neurodegenerative diseases (NDDs) as well as the aging brain. Compelling evidence supports that acute neurological disorders, such as traumatic brain injury (TBI) and stroke, are also accompanied by increased deposition of toxic Aβ, Tau and α-syn species. While the contribution of these pathological proteins to neurodegeneration has been experimentally ascertained, the cellular and molecular mechanisms driving Aβ, Tau and α-syn-related brain damage remain to be fully clarified. In the last few years, studies have shown that Aβ, Tau and α-syn may contribute to neurodegeneration also by inducing and/or promoting blood-brain barrier (BBB) disruption. These pathological proteins can affect BBB integrity either directly by affecting key BBB components such as pericytes and endothelial cells (ECs) or indirectly, by promoting brain macrophages activation and dysfunction. Here, we summarize and critically discuss key findings showing how Aβ, Tau and α-syn can contribute to BBB damage in most common NDDs, TBI and stroke. We also highlight the need for a deeper characterization of the role of these pathological proteins in the activation and dysfunction of brain macrophages, pericytes and ECs to improve diagnosis and treatment of acute and chronic neurological disorders.

Emerging Links between Cerebral Blood Flow Regulation and Cognitive Decline: A Role for Brain Microvascular Pericytes

Cognitive impairment associated with vascular etiology has been of considerable interest in the development of dementia. Recent studies have started to uncover cerebral blood flow deficits in initiating cognitive deterioration. Brain microvascular pericytes, the only type of contractile cells in capillaries, are involved in the precise modulation of vascular hemodynamics due to their ability to regulate resistance in the capillaries. They exhibit potential in maintaining the capillary network geometry and basal vascular tone. In addition, pericytes can facilitate better blood flow supply in response to neurovascular coupling. Their dysfunction is thought to disturb cerebral blood flow causing metabolic imbalances or structural injuries, leading to consequent cognitive decline. In this review, we summarize the characteristics of microvascular pericytes in brain blood flow regulation and outline the framework of a two-hit hypothesis in cognitive decline, where we emphasize how pericytes serve as targets of cerebral blood flow dysregulation that occurs with neurological challenges, ranging from genetic factors, aging, and pathological proteins to ischemic stress.

Pericyte dysfunction is a key mediator of the risk of cerebral ischemia

Pericytes are critical yet understudied cells that are a central component of the neurovascular unit. They are connected to the cerebrovascular endothelium and help control vascular contractility and maintain the blood-brain barrier. Pericyte dysfunction has the potential to mediate many of the deleterious vascular consequences of ischemic stroke. Current therapeutics are designed to be administered after stroke onset and limit damage, but there are few options to target vascular risk factors pre-ischemia which likely contribute to stroke outcomes. Here, we focus on the role of pericytes in health and disease, and discuss how pericyte dysfunction can increase the risk of ischemic injury. Additionally, we note that despite the importance of pericytes in cerebrovascular disease, there are relatively few current therapeutic options that target pericyte function.

Vasa Vasorum in Saphenous Vein for CABG: A Review of Morphological Characteristics

This short article discusses selected scanning electron microscope and transmission electron microscope features of vasa vasorum including pericytes and basement membrane of the human saphenous vein (SV) harvested with either conventional (CON) or no-touch (NT) technique for coronary artery bypass grafting. Scanning electron microscope data shows the general damage to vasa vasorum of CON-SV, while the transmission electron microscope data presents ultrastructural features of the vasa in more detail. Hence there are some features suggesting pericyte involvement in the contraction of vasa blood vessels, particularly in CON-SV. Other features associated with the vasa vasorum of both CON-SV and NT-SV preparations include thickened and/or multiplied layers of the basement membrane. In some cases, multiple layers of basement membrane embrace both pericyte and vasa microvessel making an impression of a "unit" made by basement membrane-pericyte-endothelium/microvessel. It can be speculated that this structural arrangement has an effect on the contractile and/or relaxing properties of the vessels involved. Endothelial colocalization of immunoreactive inducible nitric oxide synthase and endothelin-1 can be observed (with laser confocal microscope) in some of the vasa microvessels. It can be speculated that this phenomenon, particularly of the expression of inducible nitric oxide synthase, might be related to structurally changed vasa vessels, e.g., with expanded basement membrane. Fine physiological relationships between vasa vasorum endothelium, basement membrane, pericyte, and perivascular nerves have yet to be uncovered in the detail needed for better understanding of the cells'specific effects in SV preparations for coronary artery bypass grafting.

Imaging the time course, morphology, neuronal tissue compression, and resolution of cerebral microhemorrhages in mice using intravital two-photon microscopy: insights into arteriolar, capillary, and venular origin

Cerebral microhemorrhages (CMHs, microbleeds), a manifestation of age-related cerebral small vessel disease, contribute to the pathogenesis of cognitive decline and dementia in older adults. Histological studies have revealed that CMHs exhibit distinct morphologies, which may be attributed to differences in intravascular pressure and the size of the vessels of origin. Our study aimed to establish a direct relationship between the size/morphology of CMHs and the size/anatomy of the microvessel of origin. To achieve this goal, we adapted and optimized intravital two-photon microscopy-based imaging methods to monitor the development of CMHs in mice equipped with a chronic cranial window upon high-energy laser light-induced photodisruption of a targeted cortical arteriole, capillary, or venule. We assessed the time course of extravasation of fluorescently labeled blood and determined the morphology and size/volume of the induced CMHs. Our findings reveal striking similarities between the bleed morphologies observed in hypertension-induced CMHs in models of aging and those originating from different targeted vessels via multiphoton laser ablation. Arteriolar bleeds, which are larger (> 100 μm) and more widely dispersed, are distinguished from venular bleeds, which are smaller and exhibit a distinct diffuse morphology. Capillary bleeds are circular and smaller (< 10 μm) in size. Our study supports the concept that CMHs can occur at any location in the vascular tree, and that each type of vessel produces microbleeds with a distinct morphology. Development of CMHs resulted in immediate constriction of capillaries, likely due to pericyte activation and constriction of precapillary arterioles. Additionally, tissue displacement observed in association with arteriolar CMHs suggests that they can affect an area with a radius of ~ 50 μm to ~ 100 μm, creating an area at risk for ischemia. Longitudinal imaging of CMHs allowed us to visualize reactive astrocytosis and bleed resolution during a 30-day period. Our study provides new insights into the development and morphology of CMHs, highlighting the potential clinical implications of differentiating between the types of vessels involved in the pathogenesis of CMHs. This information may help in the development of targeted interventions aimed at reducing the risk of cerebral small vessel disease-related cognitive decline and dementia in older adults.

Brain pericyte biology: from physiopathological mechanisms to potential therapeutic applications in ischemic stroke

Pericytes play an indispensable role in various organs and biological processes, such as promoting angiogenesis, regulating microvascular blood flow, and participating in immune responses. Therefore, in this review, we will first introduce the discovery and development of pericytes, identification methods and functional characteristics, then focus on brain pericytes, on the one hand, to summarize the functions of brain pericytes under physiological conditions, mainly discussing from the aspects of stem cell characteristics, contractile characteristics and paracrine characteristics; on the other hand, to summarize the role of brain pericytes under pathological conditions, mainly taking ischemic stroke as an example. Finally, we will discuss and analyze the application and development of pericytes as therapeutic targets, providing the research basis and direction for future microvascular diseases, especially ischemic stroke treatment.

Integrating network pharmacology analysis and pharmacodynamic evaluation for exploring the active components and molecular mechanism of moutan seed coat extract to improve cognitive impairment

Paeonia suffruticosa (Moutan) is a traditional medicinal plant in China. Its seed coat is rich in resveratrol oligomer, especially suffruticosol B (SB). Previous studies had shown that the seed coat extracts of Paeonia suffruticosa (PSCE) had good cholinesterase inhibitory activity and neuroprotective effect, but the effective dose range was unknown, and the pharmacodynamic components and molecular mechanism of PSCE had not been discussed. The current study aimed to screen the pharmacodynamic components in PSCE and investigate the improvement effect of PSCE and the selected SB on scopolamine-induced cognitive dysfunction in mice and its mechanism. The results of high-throughput sequencing and bioinformatics analysis showed that suffruticosol B (SB) and trans-gnetin H (GH) might be the main active components of PSCE; PSCE might improve cognitive dysfunction through p53, HIF-1, MAPK, and PI3K-Akt signaling pathways, while SB and GH might improve cognitive dysfunction through HIF-1 signaling pathway. SB and GH had good molecular docking activity with the target of HIF-1 signaling pathway. The pharmacodynamic activities of PSCE and SB were further verified by behavioral experiments. PSCE and SB could improve the recognition ability of familiar and new objects and shorten the escape latency in the Morris Water Maze test (PSCE 120 mg∙kg-1, p < 0.05; SB 60 mg∙kg-1, p < 0.01); PSCE and SB could increase Ach and GSH levels, enhance the activities of ChAT, SOD and CAT, decrease the levels of IL-1β, IL-6, and TNF-α, and decrease the activity of AChE. In conclusion, the results indicated that PSCE might exert pharmacodynamic activity through multiple components, targets, and pathways, and SB and GH might be the main active components of PSCE. PSCE and SB might improve cognitive dysfunction by regulating cholinergic, antioxidant, and anti-inflammatory effects. These results indicated that PSCE and SB might be potential anti-AD drug candidates, providing a scientific basis for the development and utilization of Moutan bark.

Pathological changes within the cerebral vasculature in Alzheimer's disease: New perspectives

Cerebrovascular disease underpins vascular dementia (VaD), but structural and functional changes to the cerebral vasculature contribute to disease pathology and cognitive decline in Alzheimer's disease (AD). In this review, we discuss the contribution of cerebral amyloid angiopathy and non‐amyloid small vessel disease in AD, and the accompanying changes to the density, maintenance and remodelling of vessels (including alterations to the composition and function of the cerebrovascular basement membrane). We consider how abnormalities of the constituent cells of the neurovascular unit – particularly of endothelial cells and pericytes – and impairment of the blood‐brain barrier (BBB) impact on the pathogenesis of AD. We also discuss how changes to the cerebral vasculature are likely to impair Aβ clearance – both intra‐periarteriolar drainage (IPAD) and transport of Aβ peptides across the BBB, and how impaired neurovascular coupling and reduced blood flow in relation to metabolic demand increase amyloidogenic processing of APP and the production of Aβ. We review the vasoactive properties of Aβ peptides themselves, and the probable bi‐directional relationship between vascular dysfunction and Aβ accumulation in AD. Lastly, we discuss recent methodological advances in transcriptomics and imaging that have provided novel insights into vascular changes in AD, and recent advances in assessment of the retina that allow in vivo detection of vascular changes in the early stages of AD.