Adventitial Cells Research Articles

Establishment of bone marrow and hematopoietic niches in vivo by reversion of chondrocyte differentiation of human bone marrow stromal cells

Human bone marrow stromal cells (BMSCs, also known as bone marrow-derived “mesenchymal stem cells”) can establish the hematopoietic microenvironment within heterotopic ossicles generated by transplantation at non-skeletal sites. Here we show that non-mineralized cartilage pellets formed by hBMSCs ex vivo generate complete ossicles upon heterotopic transplantation in the absence of exogenous scaffolds. These ossicles display a remarkable degree of architectural fidelity, showing that an exogenous conductive scaffold is not an absolute requirement for bone formation by transplanted BMSCs. Marrow cavities within the ossicles include erythroid, myeloid and granulopoietic lineages, clonogenic hematopoietic progenitors and phenotypic HSCs, indicating that complete stem cell niches and hematopoiesis are established. hBMSCs (CD146+ adventitial reticular cells) are established in the heterotopic chimeric bone marrow through a unique process of endochondral bone marrow formation, distinct from physiological endochondral bone formation. In this process, chondrocytes remain viable and proliferate within the pellet, are released from cartilage, and convert into bone marrow stromal cells. Once explanted in secondary culture, these cells retain phenotype and properties of skeletal stem cells (“MSCs”), including the ability to form secondary cartilage pellets and secondary ossicles upon serial transplantation. Ex vivo, hBMSCs initially induced to form cartilage pellets can be reestablished in adherent culture and can modulate gene expression between cartilage and stromal cell phenotypes. These data show that so-called “cartilage differentiation” of BMSCs in vitro is a reversible phenomenon, which is actually reverted, in vivo, to the effect of generating stromal cells supporting the homing of hematopoietic stem cells and progenitors.

High proliferative potential endothelial colony-forming cells contribute to hypoxia-induced pulmonary artery vasa vasorum neovascularization

Angiogenic expansion of the vasa vasorum (VV) is an important contributor to pulmonary vascular remodeling in the pathogenesis of pulmonary hypertension (PH). High proliferative potential endothelial progenitor-like cells have been described in vascular remodeling and angiogenesis in both systemic and pulmonary circulations. However, their role in hypoxia-induced pulmonary artery (PA) VV expansion in PH is not known. We hypothesized that profound PA VV neovascularization observed in a neonatal calf model of hypoxia-induced PH is due to increased numbers of subsets of high proliferative cells within the PA adventitial VV endothelial cells (VVEC). Using a single cell clonogenic assay, we found that high proliferative potential colony-forming cells (HPP-CFC) comprise a markedly higher percentage in VVEC populations isolated from the PA of hypoxic (VVEC-Hx) compared with control (VVEC-Co) calves. VVEC-Hx populations that comprised higher numbers of HPP-CFC also demonstrated markedly higher expression levels of CD31, CD105, and c-kit than VVEC-Co. In addition, significantly higher expression of CD31, CD105, and c-kit was observed in HPP-CFC vs. the VVEC of the control but not of hypoxic animals. HPP-CFC exhibited migratory and tube formation capabilities, two important attributes of angiogenic phenotype. Furthermore, HPP-CFC-Co and some HPP-CFC-Hx exhibited elevated telomerase activity, consistent with their high replicative potential, whereas a number of HPP-CFC-Hx exhibited impaired telomerase activity, suggestive of their senescence state. In conclusion, our data suggest that hypoxia-induced VV expansion involves an emergence of HPP-CFC populations of a distinct phenotype with increased angiogenic capabilities. These cells may serve as a potential target for regulating VVEC neovascularization.

Tgfbr2 disruption in postnatal smooth muscle impairs aortic wall homeostasis

TGF-β is essential for vascular development; however, excess TGF-β signaling promotes thoracic aortic aneurysm and dissection in multiple disorders, including Marfan syndrome. Since the pathology of TGF-β overactivity manifests primarily within the arterial media, it is widely assumed that suppression of TGF-β signaling in vascular smooth muscle cells will ameliorate aortic disease. We tested this hypothesis by conditional inactivation of Tgfbr2, which encodes the TGF-β type II receptor, in smooth muscle cells of postweanling mice. Surprisingly, the thoracic aorta rapidly thickened, dilated, and dissected in these animals. Tgfbr2 disruption predictably decreased canonical Smad signaling, but unexpectedly increased MAPK signaling. Type II receptor-independent effects of TGF-β and pathological responses by nonrecombined smooth muscle cells were excluded by serologic neutralization. Aortic disease was caused by a perturbed contractile apparatus in medial cells and growth factor production by adventitial cells, both of which resulted in maladaptive paracrine interactions between the vessel wall compartments. Treatment with rapamycin restored a quiescent smooth muscle phenotype and prevented dissection. Tgfbr2 disruption in smooth muscle cells also accelerated aneurysm growth in a murine model of Marfan syndrome. Our data indicate that basal TGF-β signaling in smooth muscle promotes postnatal aortic wall homeostasis and impedes disease progression.

Brain mesenchymal stem cells: The other stem cells of the brain?

Multipotent mesenchymal stromal cells (MSC), have the potential to differentiate into cells of the mesenchymal lineage and have non-progenitor functions including immunomodulation. The demonstration that MSCs are perivascular cells found in almost all adult tissues raises fascinating perspectives on their role in tissue maintenance and repair. However, some controversies about the physiological role of the perivascular MSCs residing outside the bone marrow and on their therapeutic potential in regenerative medicine exist. In brain, perivascular MSCs like pericytes and adventitial cells, could constitute another stem cell population distinct to the neural stem cell pool. The demonstration of the neuronal potential of MSCs requires stringent criteria including morphological changes, the demonstration of neural biomarkers expression, electrophysiological recordings, and the absence of cell fusion. The recent finding that brain cancer stem cells can transdifferentiate into pericytes is another facet of the plasticity of these cells. It suggests that the perversion of the stem cell potential of pericytes might play an even unsuspected role in cancer formation and tumor progression.

Neurohistopathological Findings of the Effects of Amprolium on the Brain and Spinal Cord Changes in the a Animal Model

The aim of the study was to evaluate the polioencephalomalacia induced with amprolium in goats: pathologic changes of the central nervous system. Eight apparently healthy goats of 6 to 9 weeks of age were drenched with amprolium (200 mg/kg body weight) till the development of clinical signs. Three goats of the same age group were drenched with tap water only and these served as controls. Amprolium drenched goats were allowed to die after the onset of clinical signs and control goats were euthanised after the death of amprolium fed goats. At the time of development of typical clinical signs of Cerebrocortical Necrosis (CCN) the goats were killed and necropsied and a complete histopathologic examination was performed. At necropsy of the four goats, large necrotic lesion was found in the cerebral cortex, and tissue thiamine levels decreased significantly, especially in cerebrum and cerebellum. However, the brain as a whole in all experimental animals, exhibited moderate to severe congestion, oedema and numerous small yellowish foci of varying sizes scattered on the surface of the cerebral hemispheres. Microscopic changes in the brain were limited to gray matter structures of cerebral and cerebellar cortex, caudal colliculi of mid brain, thalamus, cerebellum and spinal cord. There was shrinkage of neurons, perivascular and pericellular edema, necrosis of neurons, satellitosis, glial nodule, gliosis, middle laminar necrosis and deep laminar edema. Blood vessel walls were thickened due to hypertrophy and hyperplasia of endothelial and adventitial cells. Swollen and prominent capillary epithelium, satellitosis, presence of ghost cells, gliosis and perivascular cuffing were also observed but only in some of the animals. In the cerebellar cortex, there was degeneration of Purkinje cells. The caudal colliculi of mid brain showed bilateral malacia. To the best of our knowledge, these researchers questioned the hypothesis that the amprolium could be the major factor causing polioencephalomalacia. This is the first documentation of Amprolium-Induced cerebrocortical necrosis on goat in Iran.

Prospective isolation of human bone marrow stromal cell subsets: A comparative study between Stro-1-, CD146- and CD105-enriched populations

Stro-1 has proved an efficacious marker for enrichment of skeletal stem and progenitor cells although isolated populations remain heterogeneous, exhibiting variable colony-forming efficiency and osteogenic differentiation potential. The emerging findings that skeletal stem cells originate from adventitial reticular cells have brought two further markers to the fore including CD146 and CD105 (both primarily endothelial and perivascular). This study has compared CD146-, CD105- and Stro-1 (individual and in combination)-enriched human bone marrow stromal cell subsets and assessed whether these endothelial/perivascular markers offer further selection over conventional Stro-1. Fluorescent cell sorting quantification showed that CD146 and CD105 both targeted smaller (2.22% ± 0.59% and 6.94% ± 1.34%, respectively) and potentially different human bone marrow stromal cell fractions compared to Stro-1 (16.29% ± 0.78%). CD146+, but not CD105+, cells exhibited similar alkaline phosphatase–positive colony-forming efficiency in vitro and collagen/proteoglycan deposition in vivo to Stro-1+ cells. Molecular analysis of a number of select osteogenic and potential osteo-predictive genes including ALP, CADM1, CLEC3B, DCN, LOXL4, OPN, POSTN and SATB2 showed Stro-1+ and CD146+ populations possessed similar expression profiles. A discrete human bone marrow stromal cell fraction (2.04% ± 0.41%) exhibited positive immuno-labelling for both Stro-1 and CD146. The data presented here show that CD146+ populations are comparable but not superior to Stro-1+ populations. However, this study demonstrates the critical need for new candidate markers with which to isolate homogeneous skeletal stem cell populations or skeletal stem cell populations which exhibit homogeneous in vitro/in vivo characteristics, for implementation within tissue engineering and regenerative medicine strategies.

Embryonic rat vascular smooth muscle cells revisited - a model for neonatal, neointimal SMC or differentiated vascular stem cells?

BackgroundThe A10 and A7r5 cell lines derived from the thoracic aorta of embryonic rat are widely used as models of non-differentiated, neonatal and neointimal vascular smooth muscle cells in culture. The recent discovery of resident multipotent vascular stem cells within the vessel wall has necessitated the identity and origin of these vascular cells be revisited. In this context, we examined A10 and A7r5 cell lines to establish the similarities and differences between these cell lines and multipotent vascular stem cells isolated from adult rat aortas by determining their differentiation state, stem cell marker expression and their multipotency potential in vitro.MethodsVascular smooth muscle cell differentiation markers (alpha-actin, myosin heavy chain, calponin) and stem cell marker expression (Sox10, Sox17 and S100β) were assessed using immunocytochemistry, confocal microscopy, FACS analysis and real-time quantitative PCR.ResultsBoth A10 and A7r5 expressed vascular smooth muscle differentiation, markers, smooth muscle alpha - actin, smooth muscle myosin heavy chain and calponin. In parallel analysis, multipotent vascular stem cells isolated from rat aortic explants were immunocytochemically myosin heavy chain negative but positive for the neural stem cell markers Sox10+, a neural crest marker, Sox17+ the endoderm marker, and the glia marker, S100β+. This multipotent vascular stem cell marker profile was detected in both embryonic vascular cell lines in addition to the adventitial progenitor stem cell marker, stem cell antigen-1, Sca1+. Serum deprivation resulted in a significant increase in stem cell and smooth muscle cell differentiation marker expression, when compared to serum treated cells. Both cell types exhibited weak multipotency following adipocyte inductive stimulation. Moreover, Notch signaling blockade following γ-secretase inhibition with DAPT enhanced the expression of both vascular smooth muscle and stem cell markers.ConclusionsWe conclude that A10 and A7r5 cells share similar neural stem cell markers to both multipotent vascular stem cells and adventitial progenitors that are indicative of neointimal stem-derived smooth muscle cells. This may have important implications for their use in examining vascular contractile and proliferative phenotypes in vitro.

Vascular Stem Cells in Vascular Remodeling and Diseases

BACKGROUND: Blood vessels are a source of stem and progenitor cells, which likely contribute to a variety of vascular processes and diseases. Emerging concepts in this field could influence therapeutic approaches to diseases of blood vessels such as atherosclerosis.CONTENT: Vascular Stem Cells (VSCs) field is only beginning to emerge, and thus, many issues regarding VSCs’s identity and function remain poorly understood. In fact, even after decades of intensive research, Mesenchymal Stem Cells (MSC), which is suggested to be VSCs, is still having many outstanding issues of its own. And, on top of this, likewise decades-long intensive pericyte research has not been able resolve the identity issue. While favors Adventitial Progenitor Cells (APCs) over pericytes as the likely VSC candidate, it should be pointed out that currently the opposite view (i.e., pericytes as VSCs) is more prevalent, and many excellent reviews, including a recent one, have discussed this issue extensively.SUMMARY: It has been postulated that, within the vasculature, APCs could differentiate into pericytes (CD34- CD31- CD140b+ SMA-), endothelial cells (CD34+ CD31+ CD140b- SMA-), and smooth muscle cells (SMCs) (CD34- CD31- CD140b- SMA+); and during tissue expansion or repair, APCs could also differentiate into tissue-specific cell types (e.g., muscle and fat) Thus, in vitro, APCs fulfill all criteria for being VSCs. Meanwhile, in vivo evidence is still limited and will require further investigation.KEYWORDS: vascular stem cells, VSC, mesenchymal stem cells, MSC, endothelial progenitor cells, EPC, adventitial progenitor cells, APC

NFAT signalling and the differentiation of coronary smooth muscle cells

Development of the heart is complex and cells with different embryonic origins participate in cardiac organogenesis. The first and second heart fields deliver cells to generate the atrial and ventricular chambers and also participate in venous inflow and arterial outflow tract formation. There are also important cellular contributions from two extra-cardiac cell populations, i.e. cardiac neural crest cells and the pro-epicardium.1 The neural crest cells populate the outflow tract, are involved in septation of the arterial pole into the aorta and pulmonary trunk, and contribute to the smooth muscle layer of these large vessels. The pro-epicardium forms at the venous pole of the heart as a cauliflower-like cluster, which establishes contact to the myocardial surface and through proliferation and migration rapidly invest the myocardium to establish the epicardium. The embryonic epicardium gives rise to epicardium-derived cells (EPDCs) that undergo epithelial mesenchymal transformation (EMT) and migrate into the myocardial wall to participate in coronary artery formation and to differentiate into interstitial and perivascular fibroblasts ( Figure 1 ).4 Figure 1 Model of coronary smooth muscle differentiation by calcineurin/NFAT signalling. The adult myocardium consists of three tissue layers, i.e. the endocardium, myocardium, and epicardium. In the embryo, cells from the epicardium undergo EMT and form a migratory cell population, which has been termed epicardium-derived cells (EPDC). These cells will migrate into the subepicardium or into the ventricular wall and give rise to interstitial or adventitial fibroblasts and smooth muscle cells of the coronary arteries, while their contribution to the coronary endothelium is uncertain. The epicardium secretes signals (IGF2, PDGF), which stimulate myocardial proliferation resulting in chamber wall expansion, whereas the …

Natural history of mesenchymal stem cells, from vessel walls to culture vessels.

Mesenchymal stem/stromal cells (MSCs) can regenerate tissues by direct differentiation or indirectly by stimulating angiogenesis, limiting inflammation, and recruiting tissue-specific progenitor cells. MSCs emerge and multiply in long-term cultures of total cells from the bone marrow or multiple other organs. Such a derivation in vitro is simple and convenient, hence popular, but has long precluded understanding of the native identity, tissue distribution, frequency, and natural role of MSCs, which have been defined and validated exclusively in terms of surface marker expression and developmental potential in culture into bone, cartilage, and fat. Such simple, widely accepted criteria uniformly typify MSCs, even though some differences in potential exist, depending on tissue sources. Combined immunohistochemistry, flow cytometry, and cell culture have allowed tracking the artifactual cultured mesenchymal stem/stromal cells back to perivascular anatomical regions. Presently, both pericytes enveloping microvessels and adventitial cells surrounding larger arteries and veins have been described as possible MSC forerunners. While such a vascular association would explain why MSCs have been isolated from virtually all tissues tested, the origin of the MSCs grown from umbilical cord blood remains unknown. In fact, most aspects of the biology of perivascular MSCs are still obscure, from the emergence of these cells in the embryo to the molecular control of their activity in adult tissues. Such dark areas have not compromised intents to use these cells in clinical settings though, in which purified perivascular cells already exhibit decisive advantages over conventional MSCs, including purity, thorough characterization and, principally, total independence from in vitro culture. A growing body of experimental data is currently paving the way to the medical usage of autologous sorted perivascular cells for indications in which MSCs have been previously contemplated or actually used, such as bone regeneration and cardiovascular tissue repair.

Accumulation of eosinophils, mast cells, and basophils in the spleen and the coronary arteries in anaphylactic deaths: is the Kounis hypersensitivity associated syndrome present?

In a very interesting study published in Forensic Science,Medicine, and Pathology [1] it was found that measure-ment of eosinophils and mast cells in the spleen combinedwith serum tryptase measurement could diagnose anaphy-laxis and anaphylactic death with a high degree of cer-tainty. The authors stated that anaphylactic death cannot bediagnosed by autopsy alone or by counting mast cells in thelung and airways because these methods have failed to giveconsistent results. The search for other tissues infiltrated byallergic inflammatory cells could prove of paramountimportance in diagnosing anaphylactic sudden death. Theyrecommended that splenic tissue should be sampled forimmunohistochemical examination in all cases of unwit-nessed sudden death.Eosinophils, mast cells, and basophils are importanteffector cells in the allergic response and they have beenimplicated in the pathogenesis of anaphylaxis. Whilediagnosing the cause of sudden death is a challenging taskfor both physicians and forensic pathologists, anaphylacticetiology is rarely suspected. Frequently, sudden death casesare attributed to myocardial involvement, but unrecognizedanaphylaxis may accompany up to 13 % of sudden unex-pected deaths in adults [2]. There is experimental andclinical evidence that anaphylaxis is frequently associatedwith myocardial involvement due to coronary artery spasmand thrombosis manifesting as Kounis type I and Kounistype II variant [3]. Some experiments have shown thatanaphylactic cardiac damage is not due to peripheralvasodilation but is the result of the action of anaphylacticmediators on the coronary vasculature [4]. Clinically, thereare patients with anaphylactic cardiac shock who do notrespond to fluid replacement but need anti-allergic andcurrent myocardial infarction protocol treatment, thusdenoting that the heart and especially the coronary arteriesare primarily affected [5, 6]. However, differentiatingglobal myocardial hypoperfusion from a primary cardiacmyocardial suppression due to mast cell mediator action isclearly challenging and combined myocardial suppressionand peripheral vasodilatation might occur simultaneously.There are reports of sudden death due to coronary arteryspasm in which the coronary arteries are involved. In apatient with repeated episodes of coronary spasm, who diedsuddenly following cessation of his treatment, the numberof adventitial mast cells was found to be increased [7]. Inthis patient, histologic sections in all three major coronaryarteries, including the area of spasm, were stained withtoluidine blue and showed increased mast cells. In the samereport, two additional subjects with sudden cardiac deathalso had increased mast cells in their coronary arteries withthe highest counts in atherosclerotic and hemorrhagic pla-ques. Furthermore, coronary arteries of cardiac patients arehyper-reactive and contain stores of amines deriving frominflammatory cells that are the main culprits in inducingcoronary spasm [8]. Type I and type II variants of theKounis syndrome have led to coronary artery spasm andsudden death in two patients with drug-eluting stents. It is

Development of renal renin-expressing cells does not involve PDGF-B-PDGFR-βsignaling

Apart from their endocrine functions renin-expressing cells play an important functional role as mural cells of the developing preglomerular arteriolar vessel tree in the kidney. The recruitment of renin-expressing cells from the mesenchyme to the vessel wall is not well understood. Assuming that it may follow more general lines of pericyte recruitment to endothelial tubes we have now investigated the relevance of the platelet-derived growth factor (PDGF)-B-PDGFR-β signaling pathway in this context. We studied renin expression in kidneys lacking PDGFR-β in these cells and in kidneys with reduced endothelial PDGF-B expression. We found that expression of renin in the kidneys under normal and stimulated conditions was not different from wild-type kidneys. As expected, PDGFR-β immunoreactivity was found in mesangial, adventitial and tubulo-interstitial cells but not in renin-expressing cells. These findings suggest that the PDGF-B-PDGFR-β signaling pathway is not essential for the recruitment of renin-expressing cells to preglomerular vessel walls in the kidney.

Development and pathologies of the arterial wall.

Arteries consist of an inner single layer of endothelial cells surrounded by layers of smooth muscle and an outer adventitia. The majority of vascular developmental studies focus on the construction of endothelial networks through the process of angiogenesis. Although many devastating vascular diseases involve abnormalities in components of the smooth muscle and adventitia (i.e., the vascular wall), the morphogenesis of these layers has received relatively less attention. Here, we briefly review key elements underlying endothelial layer formation and then focus on vascular wall development, specifically on smooth muscle cell origins and differentiation, patterning of the vascular wall, and the role of extracellular matrix and adventitial progenitor cells. Finally, we discuss select human diseases characterized by marked vascular wall abnormalities. We propose that continuing to apply approaches from developmental biology to the study of vascular disease will stimulate important advancements in elucidating disease mechanism and devising novel therapeutic strategies.

The interaction of transient receptor potential melastatin 7 with macrophages promotes vascular adventitial remodeling in transverse aortic constriction rats

Transient receptor potential melastatin 7 (TRPM7), a novel channel kinase, has been recently identified in the vasculature. However, its regulation and function in vascular diseases remain poorly understood. To address this lack of knowledge, we sought to examine whether TRPM7 can mediate the vascular remodeling process induced by pressure overload in the right common carotid artery proximal to the band (RCCA-B) in male Sprague-Dawley rats with transverse aortic constriction (TAC). The contribution of TRPM7 to amplified vascular remodeling after TAC was tested using morphometric and western blot analyses. Pressure overload-induced vascular wall thickening, especially in the adventitia, was readily detected in RCCA-B. The TRPM7 level was increased with a simultaneous accumulation of macrophages in the adventitia of RCCA-B, whereas the anti-inflammatory molecule annexin-1, a TRPM7 downstream target, was decreased. After the addition of the TRPM7 inhibitor 2-aminoethoxydiphenyl borate (2-APB), significant reductions in macrophage accumulation as well as the expression of monocyte chemotactic protein-1, SM-22-α and collagen I were observed, whereas annexin-1 was rescued. Finally, in cultured vascular adventitial fibroblasts treated with macrophage-conditioned medium, there were marked increases in the expression of TRPM7 and SM-22-α with a concurrent reduction in annexin-1 expression; these effects were largely prevented by treatment with 2-APB and specific anti-TRPM7 small interfering RNA. Our findings provide the first demonstration of the potential regulatory roles of TRPM7 in the vascular inflammation, pressure overload-mediated vascular adventitial collagen accumulation and cell phenotypic transformation in TAC rats. The targeting of TRPM7 has potential therapeutic importance for vascular diseases.

Correction

HomeCirculationVol. 128, No. 11Correction Free AccessCorrectionPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessCorrectionPDF/EPUBCorrection Originally published10 Sep 2013https://doi.org/10.1161/CIR.0b013e3182a8c0d6Circulation. 2013;128:e174This article corrects the followingInfusion of Light Chains From Patients With Cardiac Amyloidosis Causes Diastolic Dysfunction in Isolated Mouse HeartsAdventitial Cells Do Not Contribute to Neointimal Mass After Balloon Angioplasty of the Rat Common Carotid ArteryIn the articles by De Leon et al, “Adventitial Cells Do Not Contribute to Neointimal Mass After Balloon Angioplasty of the Rat Common Carotid Artery” (Circulation. 2001;104:1591–1593) and Liao et al, “Infusion of Light Chains From Patients With Cardiac Amyloidosis Causes Diastolic Dysfunction in Isolated Mouse Hearts” (Circulation. 2001;104:1594–1597), which published in the October 2, 2001 issue of the journal, the DOIs were missing for both articles. The DOIs are as follows:De Leon et al, “Adventitial Cells Do Not Contribute to Neointimal Mass After Balloon Angioplasty of the Rat Common Carotid Artery” (Circulation. 2001;104:1591–1593)DOI: 10.1161/01.cir.0000433836.90987.c6Liao et al, “Infusion of Light Chains From Patients With Cardiac Amyloidosis Causes Diastolic Dysfunction in Isolated Mouse Hearts” (Circulation. 2001;104:1594–1597)DOI: 10.1161/01.cir.0000433837.98610.85The current online versions of the manuscripts have been corrected. Previous Back to top Next FiguresReferencesRelatedDetailsRelated articlesInfusion of Light Chains From Patients With Cardiac Amyloidosis Causes Diastolic Dysfunction in Isolated Mouse HeartsRonglih Liao, et al. Circulation. 2001;104:1594-1597Adventitial Cells Do Not Contribute to Neointimal Mass After Balloon Angioplasty of the Rat Common Carotid ArteryHector De Leon, et al. Circulation. 2001;104:1591-1593 September 10, 2013Vol 128, Issue 11 Advertisement Article InformationMetrics © 2013 American Heart Association, Inc.https://doi.org/10.1161/CIR.0b013e3182a8c0d6 Originally publishedSeptember 10, 2013 PDF download Advertisement

18F-FDG Uptake Assessed by PET/CT in Abdominal Aortic Aneurysms Is Associated with Cellular and Molecular Alterations Prefacing Wall Deterioration and Rupture

Rupture of abdominal aortic aneurysms (AAAs) leads to a significant morbidity and mortality in aging populations, and its prediction would be most beneficial to public health. Spots positive for uptake of (18)F-FDG detected by PET are found in 12% of AAA patients (PET+), who are most often symptomatic and at high rupture risk. Comparing the (18)F-FDG-positive site with a negative site from the same aneurysm and with samples collected from AAA patients with no (18)F-FDG uptake should allow the discrimination of biologic alterations that would help in identifying markers predictive of rupture. Biopsies of the AAA wall were obtained from patients with no (18)F-FDG uptake (PET0, n = 10) and from PET+ patients (n = 8), both at the site positive for uptake and at a distant negative site of the aneurysmal wall. Samples were analyzed by immunohistochemistry, quantitative real-time polymerase chain reaction, and zymography. The sites of the aneurysmal wall with a positive (18)F-FDG uptake were characterized by a strikingly increased number of adventitial inflammatory cells, highly proliferative, and by a drastic reduction of smooth muscle cells (SMCs) in the media as compared with their negative counterpart and with the PET0 wall. The expression of a series of genes involved in the maintenance and remodeling of the wall was significantly modified in the negative sites of PET+, compared with the PET0 wall, suggesting a systemic alteration of the aneurysmal wall. Furthermore, a striking increase of several matrix metalloproteinases (MMPs), notably the MMP1 and MMP13 collagenases, was observed in the positive sites, mainly in the adventitia. Moreover, PET+ patients were characterized by a higher circulating C-reactive protein. Positive (18)F-FDG uptake in the aneurysmal wall is associated with an active inflammatory process characterized by a dense infiltrate of proliferating leukocytes in the adventitia and an increased circulating C-reactive protein. Moreover, a loss of SMC in the media and alterations of the expression of genes involved in the remodeling of adventitia and collagen degradation potentially participate in the weakening of the aneurysmal wall preceding rupture.

Abstract 318: The Role of Adventitial Resident Sca-1+ Progenitor Cells in Angiotensin II-induced Aortic Stiffening

Recent studies have shown that the adventitia contains arterial progenitor cells expressing the stem cell antigen-1 marker (Sca-1). These Sca-1 + cells function as stem/progenitor cells that have been reported to transform into smooth muscle cells and promote neo-intimal formation. We have previously found a striking deposition of adventitial collagen in the setting of experimental hypertension in mice. This fibrotic layer of collagen contributes to aortic stiffening and potentially loss of the windkessel effect, promoting systolic hypertension. Because collagen deposition occurs at the site of Sca1 + cells, we therefore hypothesized that Sca-1 + progenitor cells might serve as a source of adventitial collagen. Using confocal microscopy, we first found a dramatic increase of Sca-1 + cells in angiotensin II-treated vessels in the advential and peri-adventitial region, with no increase in CD68 + cells. These Sca-1 + cells represented approximately one fourth of total adventitial cells. Flow cytometry indicated that Sca-1 + CD31 - cells were tripled in the aortas of angiotensin II-treated mice (5.6±1.6 ×10 3 vs. 15.9±2.4 ×10 3 cells/per aorta sham vs. angiotensin II, p<0.05). We then isolated aortic Sca-1 + cells in sham and angiotensin II-treated mice using magnetic-activated cell sorting (MACS) and found collagen 1a1 gene was upregulated more than 7 fold in these cells (0.94±0.17 vs. 7.27±1.22, sham vs. angiotensin II, p<0.01). In addition, we did not see any obvious microvessel staining for Sca-1 in the adventitia, indicating these cells did not arise from the vasa vasorum. In summary, resident Sca-1 + progenitor cells likely contribute to adventitial collagen deposition and promote angiotensin II-induced aortic stiffening.

Coronary adventitial cells are linked to perivascular cardiac fibrosis via TGFβ1 signaling in the mdx mouse model of Duchenne muscular dystrophy

In Duchenne muscular dystrophy (DMD), progressive accumulation of cardiac fibrosis promotes heart failure. While the cellular origins of fibrosis in DMD hearts remain enigmatic, fibrotic tissue conspicuously forms near the coronary adventitia. Therefore, we sought to characterize the role of coronary adventitial cells in the formation of perivascular fibrosis. Utilizing the mdx model of DMD, we have identified a population of Sca1+, PDGFRα+, CD31−, and CD45− coronary adventitial cells responsible for perivascular fibrosis. Histopathology of dystrophic hearts revealed that Sca1+ cells extend from the adventitia and occupy regions of perivascular fibrosis. The number of Sca1+ adventitial cells increased two-fold in fibrotic mdx hearts vs. age matched wild-type hearts. Moreover, relative to Sca1−, PDGFRα+, CD31−, and CD45− cells and endothelial cells, Sca1+ adventitial cells FACS-sorted from mdx hearts expressed the highest level of Collagen1α1 and 3α1, Connective tissue growth factor, and Tgfβr1 transcripts. Surprisingly, mdx endothelial cells expressed the greatest level of the Tgfβ1 ligand. Utilizing Collagen1α1-GFP reporter mice, we confirmed that the majority of Sca1+ adventitial cells expressed type I collagen, an abundant component of cardiac fibrosis, in both wt (71%±4.1) and mdx (77%±3.5) hearts. In contrast, GFP+ interstitial fibroblasts were PDGFRα+ but negative for Sca1. Treatment of cultured Collagen1α1-GFP+ adventitial cells with TGFβ1 resulted in increased collagen synthesis, whereas pharmacological inhibition of TGFβR1 signaling reduced the fibrotic response. Therefore, perivascular cardiac fibrosis by coronary adventitial cells may be mediated by TGFβ1 signaling. Our results implicate coronary endothelial cells in mediating cardiac fibrosis via transmural TGFβ signaling, and suggest that the coronary adventitia is a promising target for developing novel anti-fibrotic therapies.

Membrane potential differences and viability of grapevine root cells treated with HgCl<sub>2</sub>

The effect of mercury (Hg) on the electrophysiological and permeability properties of grapevine adventitious root cells was examined. In short-term experiments, the apical segments of adventitious roots were treated with different concentrations of mercury (0.01 µmol/L to 2 µmol/L HgCl<sub>2</sub>), and trans-membrane electrical potential differences (E<sub>M</sub>) were monitored in root cortical cells, localized in distinct root zones. Based on Hg-induced decrease of E<sub>M</sub>, we can confirm that the depolarization of the membrane is an instant Hg-response and the extent of E<sub>M</sub> decrease is not only time- and concentration dependent, but also related to the developmental stage of cells and their localization on root axis. The sensitivity of root cells to Hg declined in the direction of cell division zone > cell elongation zone > absorption zone. Long-term treatment of roots with 2 µmol/L mercury showed that Hg-induced decrease of E<sub>M</sub> was accompanied by an increase of K<sup>+</sup> efflux and a decrease of the diffusion potential (E<sub>D</sub>) values. Application of fusicoccin (H<sup>+</sup>-ATPase activator) to the root medium caused an immediate hyperpolarization of the membrane in control and Hg-treated cells. Laser scanning confocal microscopy analysis confirmed that Hg reduced cell viability, which was accompanied with the occurrence of cell death hallmarks, like condensation of protoplasts, nuclei fragmentation and deposition of granular material.

β1-Integrin Is Essential for Vasoregulation and Smooth Muscle Survival In Vivo

Integrins contribute to vascular morphogenesis through regulation of adhesion and assembly of the extracellular matrix. However, the role of β1-integrin in the mature vascular wall is less clear. We sought to determine the function of β1-integrin in mature smooth muscle cells in vivo using a loss of function approach by crossing a tamoxifen-inducible sm22αCre line to a floxed β1-integrin transgenic line. Adult mice lacking smooth muscle β1-integrin survived only 10 weeks post induction. The deletion of β1-integrin resulted in profound loss of vasomotor control. Histological analysis revealed progressive fibrosis in arteries with associated apoptosis of smooth muscle cells, which was not rescued by adventitial stem cells. Smooth muscle cell apoptosis was detected in arteries with dead cells replaced primarily by collagen. Despite the catastrophic effects on vascular smooth muscle, the deleted visceral smooth muscle remained viable with the exception of a short portion of the colon, indicating that vascular but not visceral smooth muscle is particularly sensitive to changes in β1-integrin. This study reveals an essential function of β1-integrin in the maintenance of vasomotor control and highlights a critical role for β1-integrin in vascular, but not visceral, smooth muscle survival.