Role Of Pericytes Research Articles

Screening Activity of Brain Cancer-Derived Factors on Primary Human Brain Pericytes

Background/Objectives: Brain cancers offer poor prognoses to patients accompanied by symptoms that drastically impact the patient and their family. Brain tumours recruit local non-transformed cells to provide trophic support and immunosuppression within the tumour microenvironment, supporting tumour progression. Given the localisation and supportive role of pericytes at the brain vasculature, we explored the potential for brain pericytes to contribute to the brain cancer microenvironment. Methods: To investigate this, primary brain pericytes were treated with factors commonly upregulated in brain cancers. Immunofluorescent labelling identified changes to brain pericyte cell signalling, cytometric bead array measured inflammatory secretion, and flow cytometry investigated brain pericyte phagocytosis. Results: The TGFβ superfamily cytokines TGFβ and GDF-15 activated SMAD2/3 and inhibited C/EBP-δ, revealing a potential mechanism behind the pleiotropic action of TGFβ on brain pericytes. IL-17 induced secretion of IL-6 without activating NFκB, STAT1, SMAD2/3, or C/EBP-δ signalling pathways. IL-27 and IFNγ induced STAT1 signalling and significantly reduced brain pericyte phagocytosis. The remaining brain cancer-derived factors did not induce a measured response, indicating that these factors may act on other cell types or require co-stimulation with other factors to produce significant effects. Conclusions: We identify several brain cancer-secreted factors which alter relevant brain pericyte functions. This reveals mechanisms through which brain tumours may regulate brain pericyte activity and these data start to uncover the supportive role these cells may play in brain cancers.

Different gene expression patterns between mouse and human brain pericytes revealed by single-cell/nucleus RNA sequencing

AimsPericytes in the brain play important roles for microvascular physiology and pathology and are affected in neurological disorders and neurodegenerative diseases. Mouse models are often utilized for pathophysiology studies of the role of pericytes in disease; however, the translatability is unclear as brain pericytes from mouse and human have not been systematically compared. In this study, we investigate the similarities and differences of brain pericyte gene expression between mouse and human. Our analysis provides a comprehensive resource for translational studies of brain pericytes. MethodsWe integrated and compared four mouse and human adult brain pericyte single-cell/nucleus RNA-sequencing datasets derived using two single-cell RNA sequencing platforms: Smart-seq and 10×. Gene expression abundance and specificity were analyzed. Pericyte-specific/enriched genes were assigned by comparison with endothelial cells present in the same datasets, and mouse and human pericyte transcriptomes were subsequently compared to identify species-specific genes. ResultsAn overall concordance between pericyte transcriptomes was found in both Smart-seq and 10× data. 206 orthologous genes were consistently differentially expressed between human and mouse from both platforms, 91 genes were specific/up-regulated in human and 115 in mouse. Gene ontology analysis revealed differences in transporter categories in mouse and human brain pericytes. Importantly, several genes implicated in human disease were expressed in human but not in mouse brain pericytes, including SLC6A1, CACNA2D3, and SLC20A2. ConclusionsThis study provides a systematic illustration of the similarities and differences between mouse and human adult brain pericytes.

The Hidden Hand in White Matter: Pericytes and the Puzzle of Demyelination.

Disruption of myelin, the fatty sheath-insulating nerve fibers in the white matter, blocks or slows the rapid transmission of electrical signals along nerve cells and contributes to several neurodegenerative diseases such as multiple sclerosis. Traditionally, research has focused on neuronal dysfunction as the primary factor, including autoimmunity, infections, inflammation, and genetic disorders causing demyelination. However, recent insights emphasize the critical role of pericytes, non-neuronal cells that regulate blood flow and maintain the health of blood vessels within white matter. This Perspective explores the principal mechanisms through which pericyte dysfunction contributes to damage and demyelination, including impaired communication with neurons (neurovascular uncoupling), excessive formation of scar tissue (fibrosis), and the infiltration of detrimental substances from the bloodstream. Understanding these mechanisms of pericyte-driven demyelination may lead to the creation of new therapeutic strategies for tackling a range of neurodegenerative conditions.

The Role of Pericytes in Inner Ear Disorders: A Comprehensive Review.

Inner ear disorders, including sensorineural hearing loss, Meniere's disease, and vestibular neuritis, are prevalent conditions that significantly impact the quality of life. Despite their high incidence, the underlying pathophysiology of these disorders remains elusive, and current treatment options are often inadequate. Emerging evidence suggests that pericytes, a type of vascular mural cell specialized to maintain the integrity and function of the microvasculature, may play a crucial role in the development and progression of inner ear disorders. The pericytes are present in the microvasculature of both the cochlea and the vestibular system, where they regulate blood flow, maintain the blood-labyrinth barrier, facilitate angiogenesis, and provide trophic support to neurons. Understanding their role in inner ear disorders may provide valuable insights into the pathophysiology of these conditions and lead to the development of novel diagnostic and therapeutic strategies, improving the standard of living. This comprehensive review aims to provide a detailed overview of the role of pericytes in inner ear disorders, highlighting the anatomy and physiology in the microvasculature, and analyzing the mechanisms that contribute to the development of the disorders. Furthermore, we explore the potential pericyte-targeted therapies, including antioxidant, anti-inflammatory, and angiogenic approaches, as well as gene therapy strategies.

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

BackgroundPatients 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.MethodsTo 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.ResultsOur 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.ConclusionsOur 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.

Role of pericytes in regulating penile angiogenesis and nerve regeneration.

Pericytes are multifunctional mural cells that surround the abluminal wall of endothelial cells and are associated with vascular development, vascular permeability, and angiogenesis. Additionally, pericytes demonstrate stem cell-like properties and contribute to neuroinflammatory processes. Pericytes have been extensively studied in the central nervous system. However, specific mechanisms underlying its involvement in various physiological and pathological conditions, especially in erectile dysfunction (ED), remain poorly understood. Advancements in in vitro and in vitro techniques, such as single-cell RNA sequencing, are expanding our understanding of pericytes. Recent studies have shown that pericyte dysfunction is considered an important factor in the pathogenesis of vascular and neurological ED. Therefore, this study aims to analyze the specific role of pericytes in ED, focusing on diabetic and neurogenic ED. This article provides a comprehensive review of research findings on PubMed from 2000 to 2023, concerning pericyte dysfunction in the process of ED, offering valuable insights, and suggesting directions for further research.

Abstract Tu061: Pericyte-mediated perivascular fibrosis in the pressure-overloaded heart is dependent on TGF-β signaling and is restrained by ITGB1.

Background: Pericytes exhibit remarkable phenotypic plasticity and have been implicated in the pathogenesis of fibrosis. Cardiac pericytes are involved in repair and fibrotic remodeling of the infarcted heart; however, their role in the cardiomyopathy induced by pressure overload is not known. We hypothesized that cardiac pericytes may contribute to remodeling of the pressure-overloaded heart by converting into fibroblasts and we examined the molecular signals mediating pericyte activation. Methods and Results: Transverse aortic constriction (TAC) protocols were performed to study the role of pericytes in the pressure-overloaded heart. Using fibroblast:pericyte dual reporter mice and lineage tracing experiments with the inducible NG2 CreER mice (to track pericytes) combined with PDGFRa EGFP reporter mice (to reliably label fibroblasts), we found no pericyte to fibroblast conversion in the pressure-overloaded heart. scRNA-seq demonstrated that pericyte lineage cells do not express fibroblast identity genes after TAC but acquire a fibrogenic phenotype expressing high levels of matricellular genes, growth factors, adhesion molecules and integrins. Bioinformatic analysis identified transforming growth factor (TGF)-b and integrin beta-1 (ITGB1) as important upstream regulators of the transcriptional profile of pericytes after TAC. Pericyte-specific loss of transforming growth factor beta receptor 2 (TGFBR2) attenuated dysfunction and perivascular fibrosis after TAC. In contrast, pericyte-specific ITGB1 loss had deleterious effects increasing mortality, promoting dysfunction, inducing microvascular rarefaction and stimulating a pro-inflammatory and fibrogenic pericyte phenotype. Conclusions: In the pressure-overloaded heart, pericytes acquire a fibrogenic phenotype without converting to fibroblasts. Pericyte-specific activation of TGF-β pathways mediates perivascular myocardial fibrosis after TAC. In contrast, pericyte-specific ITGB1 signaling exerts protective actions, preserving microvascular structure, attenuating inflammation and inhibiting fibrosis.

Irisflorentin improves functional recovery after spinal cord injury by protecting the blood–spinal cord barrier and promoting axonal growth

Spinal cord injury (SCI) induces the disruption of the blood–spinal cord barrier (BSCB) and the failure of axonal growth. SCI activates a complex series of responses, including cell apoptosis and endoplasmic reticulum (ER) stress. Pericytes play a critical role in maintaining BSCB integrity and facilitating tissue growth and repair. However, the roles of pericytes in SCI and the potential mechanisms underlying the improvements in functional recovery in SCI remain unclear. Recent evidence indicates that irisflorentin exerts neuroprotective effects against Parkinson's disease; however, whether it has potential protective roles in SCI or not is still unknown. In this study, we found that the administration of irisflorentin significantly inhibited pericyte apoptosis, protected BSCB integrity, promoted axonal growth, and ultimately improved locomotion recovery in a rat model of SCI. In vitro, we found that the positive effects of irisflorentin on axonal growth were likely to be mediated by regulating the crosstalk between pericytes and neurons. Furthermore, irisflorentin effectively ameliorated ER stress caused by incubation with thapsigargin (TG) in pericytes. Meanwhile, the protective effect of irisflorentin on BSCB disruption is strongly related to the reduction of pericyte apoptosis via inhibition of ER stress. Collectively, our findings demonstrate that irisflorentin is beneficial for functional recovery after SCI and that pericytes are a valid target of interest for future SCI therapies.

Modern view on the role of pericytes in the microcirculation

Pericytes were discovered about 150 years ago and their name can be translated as enveloping cells. The location of pericytes on the outer wall of capillaries, the presence of appendages and close contact with neighboring endothelial cells of the capillaries resulted in the hypothesis of their participation in the capillary blood flow control. Over the last years, a large number of publications confirming this hypothesis have appeared. Moreover, the data accumulated to date indicate that pericytes are multifunctional cells and play a significant and sometimes key role in such processes as regulation of tissue blood flow, functioning of the blood-brain barrier, angiogenesis, vascular remodeling, and immune responses. The participation of pericytes in the pathogenesis of certain diseases has been shown and the potential for their use as targets for therapeutic effects has been demonstrated.

Signaling Role of Pericytes in Vascular Health and Tissue Homeostasis.

Pericytes are multipotent cells embedded within the vascular system, primarily surrounding capillaries and microvessels where they closely interact with endothelial cells. These cells are known for their intriguing properties due to their heterogeneity in tissue distribution, origin, and multifunctional capabilities. Specifically, pericytes are essential in regulating blood flow, promoting angiogenesis, and supporting tissue homeostasis and regeneration. These multifaceted roles draw on pericytes' remarkable ability to respond to biochemical cues, interact with neighboring cells, and adapt to changing environmental conditions. This review aims to summarize existing knowledge on pericytes, emphasizing their versatility and involvement in vascular integrity and tissue health. In particular, a comprehensive view of the major signaling pathways, such as PDGFβ/ PDGFRβ, TGF-β, FOXO and VEGF, along with their downstream targets, which coordinate the behavior of pericytes in preserving vascular integrity and promoting tissue regeneration, will be discussed. In this light, a deeper understanding of the complex signaling networks defining the phenotype of pericytes in healthy tissues is crucial for the development of targeted therapies in vascular and degenerative diseases.

Single-cell transcriptome analysis of cavernous tissues reveals the key roles of pericytes in diabetic erectile dysfunction.

Erectile dysfunction (ED) affects a significant proportion of men aged 40-70 and is caused by cavernous tissue dysfunction. Presently, the most common treatment for ED is phosphodiesterase 5 inhibitors; however, this is less effective in patients with severe vascular disease such as diabetic ED. Therefore, there is a need for development of new treatment, which requires a better understanding of the cavernous microenvironment and cell-cell communications under diabetic condition. Pericytes are vital in penile erection; however, their dysfunction due to diabetes remains unclear. In this study, we performed single-cell RNA sequencing to understand the cellular landscape of cavernous tissues and cell type-specific transcriptional changes in diabetic ED. We found a decreased expression of genes associated with collagen or extracellular matrix organization and angiogenesis in diabetic fibroblasts, chondrocytes, myofibroblasts, valve-related lymphatic endothelial cells, and pericytes. Moreover, the newly identified pericyte-specific marker, Limb Bud-Heart (Lbh), in mouse and human cavernous tissues, clearly distinguishing pericytes from smooth muscle cells. Cell-cell interaction analysis revealed that pericytes are involved in angiogenesis, adhesion, and migration by communicating with other cell types in the corpus cavernosum; however, these interactions were highly reduced under diabetic conditions. Lbh expression is low in diabetic pericytes, and overexpression of LBH prevents erectile function by regulating neurovascular regeneration. Furthermore, the LBH-interacting proteins (Crystallin Alpha B and Vimentin) were identified in mouse cavernous pericytes through LC-MS/MS analysis, indicating that their interactions were critical for maintaining pericyte function. Thus, our study reveals novel targets and insights into the pathogenesis of ED in patients with diabetes.

Single-cell transcriptome analysis of cavernous tissues reveals the key roles of pericytes in diabetic erectile dysfunction

Erectile dysfunction (ED) affects a significant proportion of men aged 40–70 and is caused by cavernous tissue dysfunction. Presently, the most common treatment for ED is phosphodiesterase 5 inhibitors; however, this is less effective in patients with severe vascular disease such as diabetic ED. Therefore, there is a need for development of new treatment, which requires a better understanding of the cavernous microenvironment and cell-cell communications under diabetic condition. Pericytes are vital in penile erection; however, their dysfunction due to diabetes remains unclear. In this study, we performed single-cell RNA sequencing to understand the cellular landscape of cavernous tissues and cell type-specific transcriptional changes in diabetic ED. We found a decreased expression of genes associated with collagen or extracellular matrix organization and angiogenesis in diabetic fibroblasts, chondrocytes, myofibroblasts, valve-related lymphatic endothelial cells, and pericytes. Moreover, the newly identified pericyte-specific marker, Limb Bud-Heart (Lbh), in mouse and human cavernous tissues, clearly distinguishing pericytes from smooth muscle cells. Cell-cell interaction analysis revealed that pericytes are involved in angiogenesis, adhesion, and migration by communicating with other cell types in the corpus cavernosum; however, these interactions were highly reduced under diabetic conditions. Lbh expression is low in diabetic pericytes, and overexpression of LBH prevents erectile function by regulating neurovascular regeneration. Furthermore, the LBH-interacting proteins (Crystallin Alpha B and Vimentin) were identified in mouse cavernous pericytes through LC-MS/MS analysis, indicating that their interactions were critical for maintaining pericyte function. Thus, our study reveals novel targets and insights into the pathogenesis of ED in patients with diabetes.

The Role of Pericytes in Lipopolysaccharide-Induced Murine Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a heterogeneous clinical syndrome that is most commonly triggered by infection-related inflammation. Lung pericytes can respond to infection and act as immune and proangiogenic cells; moreover, these cells can differentiate into myofibroblasts in nonresolving ARDS and contribute to the development of pulmonary fibrosis. Here, we aimed to characterize the role of lung cells, which present characteristics of pericytes, such as peri-endothelial location and expression of a panel of specific markers. A murine model of lipopolysaccharide (LPS)-induced resolving ARDS was used to study their role in ARDS. The development of ARDS was confirmed after LPS instillation, which was resolved 14 days after onset. Immunofluorescence and flow cytometry showed early expansion of neural-glial antigen 2+ β-type platelet-derived growth factor receptor+ pericytes in murine lungs with loss of CD31+ β-type platelet-derived growth factor receptor+ endothelial cells. These changes were accompanied by specific changes in lung structure and loss of vascular integrity. On day 14 after ARDS onset, the composition of pericytes and endothelial cells returned to baseline values. LPS-induced ARDS activated NOTCH signaling in lung pericytes, the inhibition of which during LPS stimulation reduced the expression of its downstream target genes, pericyte markers, and angiogenic factors. Together, these data indicate that lung pericytes in response to inflammatory injury activate NOTCH signaling that supports their maintenance and in turn can contribute to recovery of the microvascular endothelium.

Carbenoxolone mitigates extensive fibrosis formation in PLP-induced EAE model and multiple sclerosis serum-exposed pericyte culture.

Multiple sclerosis (MS) is one of the most common causes of disability in young adults. Nearly, 85% of MS cases start with attacks and remissions, classified as relapsing-remitting multiple sclerosis (RRMS). With repeating attacks, MS causes brain-spinal cord atrophy and enhanced disability as disease progresses. PLP-induced EAE is one of the most established models for pathophysiology and treatment of RRMS. Recent studies demonstrated the possible role of pericytes in perivascular and intra-lesional fibrosis in PLP-induced EAE, whose importance remains elusive. Hence, we have investigated the possible role of pericytes in fibrosis formation and amelioration with a hemichannel blocker, Carbenoxolone (CBX). PLP-induced experimental autoimmune encephalitis (EAE) model is used and the effect of CBX is investigated. Clinical scores were recorded and followed. Perivascular Collagen 1 and 3 accumulations were demonstrated as markers of fibrosis in the spinal cord. To delineate the role of pericytes, human brain vascular pericytes (HBVP) were incubated with the sera of MS patients to induce in-vitro MS model and the fibrosis formation was investigated. In the PLP induced in-vivo model, both intracerebroventricular and intraperitoneal CBX have significantly mitigated the disease progression followed by clinical scores, demyelination, and fibrosis. Moreover, CBX significantly mitigated MS-serum-induced fibrosis in the HBVP cell culture. The study demonstrated two important findings. First, CBX decreases fibrosis formation in both in-vivo and in-vitro MS models. Secondly, it improves neurological scores and decreases demyelination in the EAE model. Therefore, CBX can be potential novel therapeutic option in treating Multiple Sclerosis.

The fate and role of the pericytes in myocardial diseases.

The adult mammalian heart contains a large population of pericytes that play important roles in homeostasis and disease. In the normal heart, pericytes regulate microvascular permeability and flow. Myocardial diseases are associated with marked alterations in pericyte phenotype and function. This review manuscript discusses the role of pericytes in cardiac homeostasis and disease. Following myocardial infarction (MI), cardiac pericytes participate in all phases of cardiac repair. During the inflammatory phase, pericytes may secrete cytokines and chemokines and may regulate leukocyte trafficking, through formation of intercellular gaps that serve as exit points for inflammatory cells. Moreover, pericyte contraction induces microvascular constriction, contributing to the pathogenesis of 'no-reflow' in ischemia and reperfusion. During the proliferative phase, pericytes are activated by growth factors, such as transforming growth factor (TGF)-β and contribute to fibrosis, predominantly through secretion of fibrogenic mediators. A fraction of pericytes acquires fibroblast identity but contributes only to a small percentage of infarct fibroblasts and myofibroblasts. As the scar matures, pericytes form a coat around infarct neovessels, promoting stabilization of the vasculature. Pericytes may also be involved in the pathogenesis of chronic heart failure, by regulating inflammation, fibrosis, angiogenesis and myocardial perfusion. Pericytes are also important targets of viral infections (such as SARS-CoV2) and may be implicated in the pathogenesis of cardiac complications of COVID19. Considering their role in myocardial inflammation, fibrosis and angiogenesis, pericytes may be promising therapeutic targets in myocardial disease.

Pericyte signaling via soluble guanylate cyclase shapes the vascular niche and microenvironment of tumors

Pericytes and endothelial cells (ECs) constitute the fundamental components of blood vessels. While the role of ECs in tumor angiogenesis and the tumor microenvironment is well appreciated, pericyte function in tumors remains underexplored. In this study, we used pericyte-specific deletion of the nitric oxide (NO) receptor, soluble guanylate cyclase (sGC), to investigate via single-cell RNA sequencing how pericytes influence the vascular niche and the tumor microenvironment. Our findings demonstrate that pericyte sGC deletion disrupts EC–pericyte interactions, impairing Notch-mediated intercellular communication and triggering extensive transcriptomic reprogramming in both pericytes and ECs. These changes further extended their influence to neighboring cancer-associated fibroblasts (CAFs) and tumor-associated macrophages (TAMs) through paracrine signaling, collectively suppressing tumor growth. Inhibition of pericyte sGC has minimal impact on quiescent vessels but significantly increases the vulnerability of angiogenic tumor vessels to conventional anti-angiogenic therapy. In conclusion, our findings elucidate the role of pericytes in shaping the tumor vascular niche and tumor microenvironment and support pericyte sGC targeting as a promising strategy for improving anti-angiogenic therapy for cancer treatment.

Abstract 1455: In vitro blood brain barrier model for evaluation of brain metastasis

Abstract Introduction: Brain metastasis significantly reduces the patient's quality of life and survival, but there are only a few choices of treatment for brain metastasis. The research for brain metastasis is difficult because of its complex and unique microenvironment, including blood-brain barrier (BBB). The BBB maintains strong cell adhesion of the vascular endothelial cells (ECs) to protect the brain parenchyma. The BBB is composed of three cell types: vascular endothelial cells, pericytes, and astrocytes. As the role of pericytes in maintaining the BBB function has become more evident, the reconstituted models of the BBB in which ECs, pericytes, and astrocytes are seeded on the front and back of the insert membrane have gotten our attention. In the field of cancer, the role of not only ECs but also wall cells, corresponding to pericytes in the brain, has been focused on. In this study, we aimed to create the in vitro BBB models and elucidate the interaction of the BBB and the metastasizing cancer cells. Methods: We applied a reconstituted model of the BBB consisting of ECs, pericytes, and astrocytes of human immortalized cells (Ito R, et al. Mol Pharm 2019) and created the co-culture system for evaluating brain metastasis. We constructed four co-culture systems and compared the migration ability of MDA231 in those models: EPA model (ECs, pericytes, and astrocytes), E0A model (ECs and astrocytes), EP0 model (ECs and pericytes), and E00 model (ECs only). We also analyzed the migration ability of the pairs of parental and brain metastatic (BrM) cell lines. Results: The BBB reconstituted model (EPA model), in which ECs were co-cultured with pericytes and astrocytes, showed higher trans-epithelial electrical resistance and lower permeability than the other co-culture models. When cancer cells were seeded, the EPA model strongly inhibited metastatic invasion of cancer cells compared to the other models. It suggests that both pericytes and astrocytes are essential for regulating cancer cell invasion. In addition, when the BrM cells of MDA231 and Ex3LL were seeded, the BrM cells invaded the EPA model more easily than the parental cells. It indicates that this model can reproduce in vivo brain vascular functions. Conclusion: We created the BBB reconstituted model which mimics the brain vascular microenvironment. This model reproduced the in vivo BBB function to protect brain from cancer cells and evaluated the brain metastatic ability of the cancer cells. Using this model, we showed that pericytes and astrocytes were essential for the BBB barrier function against the cancer cells. We need further investigation to elucidate the mechanism of brain metastasis using this BBB model. Citation Format: Shoko Noda-Narita, Atsu Aiba. In vitro blood brain barrier model for evaluation of brain metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1455.

Pericyte activation accompanied by peritubular capillaries dysfunction and pericyte-to-myofibroblast transition is associated with renal fibrosis in diabetic nephropathy.

Tubulointerstitial renal fibrosis is an essential feature of diabetic nephropathy (DN). Pericytes play a critical role in microvascular diseases and renal fibrogenesis. However, the role of pericytes in DN remains unclear. Herein, we aimed to explore the properties and possible mechanisms of pericytes in renal fibrosis in DN. We used multiplex immunofluorescence staining to evaluate the location and expression of activated pericytes and to assess capillary dilation and interstitial fibrosis in the kidneys of db/db mice. Pericytes were co-stained for alpha-smooth muscle actin (α-SMA) to determine which ones differentiate into myofibroblasts in db/db mice. Expression of CD34 and platelet-derived growth factor receptor beta (PDGFR-β) was assessed in kidney tissue from patients with DN by immunohistochemical staining. We found that cell staining for nerve/glial antigen 2 (NG2)+ and PDGFR-β+ was greater in the kidneys of db/db mice than in those of db/m mice. There was impaired pericyte coverage of blood vessels and capillary dilation in the renal interstitium. These changes were accompanied by increased collagen I staining and an increase in the number of pericytes with profibrotic phenotypes, as identified by increased NG2+/PDGFR-β+/α-SMA+ and decreased NG2+/PDGFR-β+/α-SMA- staining. In DN patients, expression of PDGFR-β was stronger and there was loss of CD34 compared with the findings in control patients with minor glomerular lesions. In this study, we demonstrated that pericyte activation accompanied by peritubular capillary dysfunction and pericytemyofibroblast transition is associated with renal fibrosis in DN.

THE ROLE OF PERICYTES IN REGULATING CARTILAGE DEGRADATION AND FIBROSIS

Pericytes are contractile, motile cells that surround the capillary. Recent studies have shown that pericytes promoted joint fibrosis and induced subchondral bone angiogenesis, indicating the role of pericytes in osteoarthritis (OA). However, whether pericytes are involved in regulating inflammatory and catabolic response, as well as fibrotic repair of cartilage is still unclear. Here we used 2D and 3D models to investigate the communication of pericytes and chondrocytes under inflammatory osteoarthritis conditions.CD34-CD146+ pericytes were isolated and sorted from human bone marrow. Human OA chondrocytes were isolated from OA joints. In 2D studies, monolayer cultured chondrocytes were treated +/- pericyte conditioned media, +/- 1ng/ml IL1β for 24h. In 3D studies, pericytes and chondrocytes were cultured within fibrin gel in 3D polyurethane scaffolds, separately or combined for 7 days, followed by treatment of +/- IL1β for another 7 days (Fig 2A). The inflammatory response, catabolic activity and expression of fibrosis markers of chondrocytes and pericytes were measured by ELISA and/or q-rtPCR.Pericytes had weak inflammatory, catabolic and fibrotic response to IL1β (data not shown). The 2D study showed that pericyte conditioned media promoted inflammation, catabolism and fibrosis markers of chondrocytes, in the absence of IL1β treatment (Figure 1). However, study in 3D showed that coculture of chondrocytes and pericytes reduced the inflammatory and catabolic response of chondrocytes to IL1β and induced fibrosis markers in chondrocytes (Figure 2).Pericytes are involved in regulating inflammatory response, catabolic response and fibrosis of chondrocytes. The opposite results from 2D and 3D experiments indicate the variety of the regulatory role of pericytes in the interaction with chondrocytes within different culture models. The underlying mechanism is under evaluation with on-going studies.AcknowledgementsThis study was funded by SINPAIN project, from European Union's Horizon Europe research and innovation programme under Grant Agreement NO. 101057778. Funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union. Neither the European Union nor the granting authority can be held responsible for them.For any figures or tables, please contact the authors directly.

The role of pericyte in ocular vascular diseases.

Pericytes are located in the stromal membrane of the capillary outer wall and contain endothelial cells (ECs). They are pivotal in regulating blood flow, enhancing vascular stability, and maintaining the integrity of the blood-retina barrier (BRB)/blood-brain barrier (BBB). The pluripotency of pericytes allows them to differentiate into various cell types, highlighting their significance in vascular disease pathogenesis, as demonstrated by previous studies. This potential enables pericytes to be a potential biomarker for the diagnosis and a target for treatment of vascular disorders. The retina, an essential part of the eyeball, is an extension of cerebral tissue with a transparent refractive medium. It offers a unique window for assessing systemic microvascular lesions. Routine fundus examination is necessary for patients with diabetes and hypertension. Manifestations, such as retinal artery tortuosity, dilation, stenosis, and abnormal arteriovenous anastomosis, serve as typical hallmarks of retinal vasculopathy. Therefore, studies of ocular vascular diseases significantly facilitate the exploration of systemic vascular diseases.