Dapagliflozin attenuates residual cardiac remodeling after surgical ventricular reconstruction in mice with an enlarged heart after myocardial infarction

BACKGROUND

Severe heart failure refractory to conventional therapy requires alternative treatment modalities. Surgical ventricular reconstruction (SVR) has been used to reverse cardiac remodeling in post-myocardial infarction (MI) patients with large left ventricular (LV) aneurysm, however, residual LV remodeling and dysfunction remain postoperatively. It is unclear whether SVR recovers response to drug treatment and whether the sodium-glucose co-transporter 2 inhibitor dapagliflozin (DAPA) reverses residual LV remodeling after SVR.

METHODS

Adult male C57 mice were subjected to MI or sham surgery. Four-week later, MI mice with LV aneurysm underwent modified SVR or second open-chest sham operation and were randomized to DAPA or vehicle for four-week. Cardiac remodeling, LV function, and the underlying mechanisms were evaluated by echocardiography, invasive LV hemodynamic measurements, mRNA sequencing, and bioinformatics analysis.

RESULTS

SVR significantly decreased LV volume; increased myocardial strain, LV pressure change rates and end-systolic elastance; and decreased heart-to-body weight ratio and myocardial fibrosis. However, significant residual cardiac remodeling remained. DAPA significantly attenuated residual cardiac remodeling and improved LV function in SVR mice but did not have curative effects in non-SVR mice. Of the 1532 genes differentially expressed in SVR and MI mice, 1037 were associated with cardiac metabolism; Src, Crebbp, Fn1, Grb2, and Mapk14 were the top 5 hub genes. Unlike sham surgery, MI upregulated those 5 genes, and treatment with SVR + DAPA normalized their expression.

CONCLUSIONS

SVR restores therapeutic response in the post-MI heart with large LV aneurysm, and DAPA attenuates residual cardiac remodeling after SVR by normalizing some cardiac metabolism-related hub genes.

A Dual Role of Heme Oxygenase-1 in Angiotensin II-Induced Abdominal Aortic Aneurysm in the Normolipidemic Mice

Abdominal aortic aneurysm (AAA) bears a high risk of rupture and sudden death of the patient. The pathogenic mechanisms of AAA remain elusive, and surgical intervention represents the only treatment option. Heme oxygenase-1 (HO-1), a heme degrading enzyme, is induced in AAA, both in mice and humans. HO-1 was reported to mitigate AAA development in an angiotensin II (AngII)-induced model of AAA in hyperlipidemic ApoE^-/- mice. Since the role of hyperlipidaemia in the pathogenesis of AAA remains controversial, we aimed to evaluate the significance of HO-1 in the development and progression of AAA in normolipidemic animals. The experiments were performed in HO-1-deficient mice and their wild-type counterparts. We demonstrated in non-hypercholesterolemic mice that the high-dose of AngII leads to the efficient formation of AAA, which is attenuated by HO-1 deficiency. Yet, if formed, they are significantly more prone to rupture upon HO-1 shortage. Differential susceptibility to AAA formation does not rely on enhanced inflammatory response or oxidative stress. AAA-resistant mice are characterized by an increase in regulators of aortic remodeling and angiotensin receptor-2 expression, significant medial thickening, and delayed blood pressure elevation in response to AngII. To conclude, we unveil a dual role of HO-1 deficiency in AAA in normolipidemic mice, where it protects against AAA development, but exacerbates the state of formed AAA.

IL-27 receptor-regulated stress myelopoiesis drives abdominal aortic aneurysm development

Abdominal aortic aneurysm (AAA) is a prevalent life-threatening disease, where aortic wall degradation is mediated by accumulated immune cells. Although cytokines regulate inflammation within the aorta, their contribution to AAA via distant alterations, particularly in the control of hematopoietic stem cell (HSC) differentiation, remains poorly defined. Here we report a pathogenic role for the interleukin-27 receptor (IL-27R) in AAA, as genetic ablation of IL-27R protects mice from the disease development. Mitigation of AAA is associated with a blunted accumulation of myeloid cells in the aorta due to the attenuation of Angiotensin II (Ang II)-induced HSC expansion. IL-27R signaling is required to induce transcriptional programming to overcome HSC quiescence and increase differentiation and output of mature myeloid cells in response to stress stimuli to promote their accumulation in the diseased aorta. Overall, our studies illuminate how a prominent vascular disease can be distantly driven by a cytokine-dependent regulation of bone marrow precursors.

Rosuvastatin- and Heparin-Loaded Poly(l-lactide- co-caprolactone) Nanofiber Aneurysm Stent Promotes Endothelialization via Vascular Endothelial Growth Factor Type A Modulation

This study explored a new rosuvastatin calcium- and heparin-loaded poly(l-lactide- co-caprolactone) (PLCL) scaffold for covered stents for treating aneurysms. The mechanism of rosuvastatin-induced endothelialization via vascular endothelial growth factor (VEGF)-A elevation was further explored. Rosu50, Rosu75, Rosu100, and phosphate-buffered saline (PBS) nanofibrous scaffolds were fabricated by coaxial electrospinning and observed by electron microscopy. Anticoagulation and pro-endothelialization properties were tested. Sixteen rabbits were selected for an in vivo assay and underwent microsurgery to establish a carotid aneurysm model. The animals were treated with covered stents and followed for 4 months using digital subtraction angiography (DSA), electron microscopy, and histology. Rosuvastatin-treated human umbilical vein endothelial cell (HUVEC) viability, function, and VEGF-A modulation were further studied to elucidate the pro-endothelialization mechanism of rosuvastatin. Our study demonstrates that rosuvastatin and heparin can be incorporated into PLCL nanofibers via electrospinning. Rosu100 nanofiber scaffolds exhibited significant anticoagulation properties. The viability of HUVECs transferred to Rosu100 nanofiber scaffolds was increased significantly. In vivo, DSA revealed that the Rosu100 group had better outcomes than the PBS group. In addition, the Rosu100 stents induced more integrated endothelialization. Further study demonstrated that rosuvastatin promoted HUVEC viability and function in vitro. The effects of rosuvastatin may be attributed to an elevation in VEGF-A. We demonstrated that rosuvastatin- and heparin-loaded PLCL-covered stents show favorable anticoagulation and pro-endothelialization properties in vitro and in vivo in a rabbit aneurysm model. VEGF-A elevation played a crucial role in rosuvastatin-promoted endothelialization. This work provides an additional option for treating cerebral aneurysms with covered stents.

Recombinant human SDF-1α administration accelerates aneurysm neck reendothelialization in rabbit saccular aneurysm after flow diverter treatment

Reendothelialization in the aneurysm neck is pivotal to vascular repair for intracranial aneurysm after flow diverter (FD) implantation. Recombinant human stromal cell-derived factor 1α (rhSDF-1α) is a vital chemoattractant to stem cells and potentially facilitates reendothelialization. Here, we sought to investigate the therapeutic effects of intravenous administration of rhSDF-1α and uncover its potential mechanism for promoting aneurysm neck reendothelialization. Recombinant pET32a-186 plasmid was transformed into Escherichia coli to produce the rhSDF-1α protein with biological activity. FD was implanted into the elastase-induced saccular aneurysm in New Zealand white rabbits. rhSDF-1α (50 μg/kg/day) was intravenously administrated for consecutive 7 days after FD implantation. After these procedures, aneurysms were harvested after 2 or 4 weeks. Scanning electron microscopy was used to measure the neointima thickness and count the endothelial-like cells at aneurysm neck. Four weeks later, the mRNA levels of endothelial markers in the neointima at aneurysm neck were examined. Migration assay showed that rhSDF-1α could induce migration of endothelial progenitor cells in a dose-dependent manner. Two weeks after stent implantation, follow-up angiography showed partial aneurysm occlusion in one of each group and total aneurysm occlusion in 17 saccular aneurysm rabbits (9 of the rhSDF-1α group and 8 of the control group). No significant change of neointima thickness at aneurysm neck was observed. Intriguingly, more endothelial-like cells were observed at aneurysm neck in the rhSDF-1α group at 2 weeks (55 vs 13 cells per high-power field) and 4 weeks (104 vs 60 cells per high-power field). The mRNA levels of Tie-2, VE-cadherin, KDR and E-selectin were significantly enhanced compared with those of the control group. These results showed that intravenous administration of rhSDF-1α can accelerate reendothelialization in the aneurysm neck after FD implantation. Our study reveals an important role of rhSDF-1α in inducing aneurysm occlusion and suggests that it achieves its function through modulating the reendothelialization.

Defective Connective Tissue Remodeling in Smad3 Mice Leads to Accelerated Aneurysmal Growth Through Disturbed Downstream TGF-β Signaling

Aneurysm-osteoarthritis syndrome characterized by unpredictable aortic aneurysm formation, is caused by SMAD3 mutations. SMAD3 is part of the SMAD2/3/4 transcription factor, essential for TGF-β-activated transcription. Although TGF-β-related gene mutations result in aneurysms, the underlying mechanism is unknown. Here, we examined aneurysm formation and progression in Smad3^-/- animals. Smad3^-/- animals developed aortic aneurysms rapidly, resulting in premature death. Aortic wall immunohistochemistry showed no increase in extracellular matrix and collagen accumulation, nor loss of vascular smooth muscle cells (VSMCs) but instead revealed medial elastin disruption and adventitial inflammation. Remarkably, matrix metalloproteases (MMPs) were not activated in VSMCs, but rather specifically in inflammatory areas. Although Smad3^-/- aortas showed increased nuclear pSmad2 and pErk, indicating TGF-β receptor activation, downstream TGF-β-activated target genes were not upregulated. Increased pSmad2 and pErk staining in pre-aneurysmal Smad3^-/- aortas implied that aortic damage and TGF-β receptor-activated signaling precede aortic inflammation. Finally, impaired downstream TGF-β activated transcription resulted in increased Smad3^-/- VSMC proliferation. Smad3 deficiency leads to imbalanced activation of downstream genes, no activation of MMPs in VSMCs, and immune responses resulting in rapid aortic wall dilatation and rupture. Our findings uncover new possibilities for treatment of SMAD3 patients; instead of targeting TGF-β signaling, immune suppression may be more beneficial.

[INSULIN-LIKE GROWTH FACTOR 1 UNDER CONDITIONS OF THE BRAIN VASCULAR DISEASES.]

The system insulin-like growth factors (IGF) occupies an important place in the development and growth of the central nervous system (CNS). Gene expression of insulin-like growth factor I (IGF-1) and IGF-1 receptor are represented in all parts of the brain and are heavily concentrated in the cerebral vessels. IGF-1 is involved in neuro-, angiogenesis, in the stimulation of cell proliferation, and repair responses to damage for both the central and peripheral nervous system. IGF- 1 exerts antioxidant, anti-inflammatory and protective effects on the CNS. The review discusses the importance and the role of IGF-I in vascular diseases of the brain, in particular, aneurysms, the ischemic stroke, the aneurysmal subarachnoid hemorrhage, as well as neuroprotection.

The role of perivascular adipose tissue in vasoconstriction, arterial stiffness, and aneurysm

Since the "rediscovery" of brown adipose tissue in adult humans, significant scientific efforts are being pursued to identify the molecular mechanisms to promote a phenotypic change of white adipocytes into brown-like cells, a process called "browning". It is well documented that white adipose tissue (WAT) mass and factors released from WAT influence the vascular function and positively correlate with cardiac arrest, stroke, and other cardiovascular complications. Similar to other fat depots, perivascular adipose tissue (PVAT) is an active endocrine organ and anatomically surrounds vessels. Both brown-like and white-like PVAT secrete various adipokines, cytokines, and growth factors that either prevent or promote the development of cardiovascular diseases (CVDs) depending on the relative abundance of each type and their bioactivity in the neighboring vasculature. Notably, pathophysiological conditions, such as obesity, hypertension, or diabetes, induce the imbalance of PVAT-derived vasoactive products that promote the infiltration of inflammatory cells. This then triggers derangements in vascular smooth muscle cells and endothelial cell dysfunction, resulting in the development of vascular diseases. In this review, we discuss the recent advances on the contribution of PVAT in CVDs. Specifically, we summarize the current proposed roles of PVAT in relationship with vascular contractility, endothelial dysfunction, neointimal formation, arterial stiffness, and aneurysm.

The role of prostaglandin E2 in human vascular inflammation

Prostaglandins (PG) are the product of a cascade of enzymes such as cyclooxygenases and PG synthases. Among PG, PGE2 is produced by 3 isoforms of PGE synthase (PGES) and through activation of its cognate receptors (EP1-4), this PG is involved in the pathophysiology of vascular diseases. Some anti-inflammatory drugs (e.g. glucocorticoids, nonsteroidal anti-inflammatory drugs) interfere with its metabolism or effects. Vascular cells can initiate many of the responses associated with inflammation. In human vascular tissue, PGE2 is involved in many physiological processes, such as increasing vascular permeability, cell proliferation, cell migration and control of vascular smooth muscle tone. PGE2 has been shown to contribute to the pathogenesis of atherosclerosis, abdominal aortic aneurysm but also in physiologic/adaptive processes such as angiogenesis. Understanding the roles of PGE2 and its cognate receptors in vascular diseases could help to identify diagnostic and prognostic biomarkers. In addition, from these recent studies new promising therapeutic approaches like mPGES-1 inhibition and/or EP4-antagonism should be investigated.

Cathepsin S deficiency results in abnormal accumulation of autophagosomes in macrophages and enhances Ang II-induced cardiac inflammation

BACKGROUND

Cathepsin S (Cat S) is overexpressed in human atherosclerotic and aneurysmal tissues and may contributes to degradation of extracellular matrix, especially elastin, in inflammatory diseases. We aimed to define the role of Cat S in cardiac inflammation and fibrosis induced by angiotensin II (Ang II) in mice.

METHODS AND RESULTS

Cat S-knockout (Cat S(-/-)) and littermate wild-type (WT) C57BL/6J mice were infused continuously with Ang II (750 ng/kg/min) or saline for 7 days. Cat S(-/-) mice showed severe cardiac fibrosis, including elevated expression of collagen I and α-smooth muscle actin (α-SMA), as compared with WT mice. Moreover, macrophage infiltration and expression of inflammatory cytokines (tumor necrosis factor α, transforming growth factor β and interleukin 1β) were significantly greater in Cat S(-/-) than WT hearts. These Ang II-induced effects in Cat S(-/-) mouse hearts was associated with abnormal accumulation of autophagosomes and reduced clearance of damaged mitochondria, which led to increased levels of reactive oxygen species (ROS) and activation of nuclear factor-kappa B (NF-κB) in macrophages.

CONCLUSION

Cat S in lysosomes is essential for mitophagy processing in macrophages, deficiency in Cat S can increase damaged mitochondria and elevate ROS levels and NF-κB activity in hypertensive mice, so it regulates cardiac inflammation and fibrosis.

[Angiomatoid fibrous histiocytoma: report of 5 cases with review of literature]

OBJECTIVE

To study the clinicopathologic features, immunophenotype and differential diagnosis of angiomatoid fibrous histiocytoma (AFH).

METHODS

The clinicopathologic features of 5 cases of AFH were analyzed. Immunohistochemical study was carried out and the literature was reviewed.

RESULTS

There were a total of 3 males and 2 females. The average age of patients was 21.4 years old. The average duration of symptoms was 13 months. The patients primarily presented with a slowly enlarging painless deep dermal or subcutaneous mass. The mass was located in the head and neck region in 3 cases, elbow in 1 case and foot in 1 case. The patients underwent complete resection of the tumor, with no adjuvant chemotherapy and/or radiotherapy given. During a period of follow up for 10 to 29 months, all of them had no recurrence or distant metastasis. Gross examination showed that the tumor was well-circumscribed and had a grey-colored cut surface, with focal hemorrhagic cystic changes. The average tumor dimension was 1.9 cm. Histologically, the tumor was composed of histiocytoid or spindly cells arranged in nodular pattern. Fibrillary neuropil-type intercellular material was identified in all cases and a fibrous pseudocapsule surrounded by lymphocytes and plasma cells was demonstrated in 3 cases. Immunohistochemical study showed that all of them were positive for vimentin and negative for S-100 protein, pan-cytokeratin, CD34 and CD31. Three of the cases expressed desmin and CD68. Two cases were epithelial membrane antigen and CD99-positive.

CONCLUSIONS

AFH is a rare tumor of intermediate malignant potential. Definitive diagnosis requires thorough histologic examination and clinical correlation. Immunohistochemistry is also helpful for diagnosis and differential diagnosis. Wide local excision with post-operative follow up is the main modality of treatment.

Absence of TGFbeta signaling in embryonic vascular smooth muscle leads to reduced lysyl oxidase expression, impaired elastogenesis, and aneurysm

To address the requirement for TGFbeta signaling in the formation and maintenance of the vascular matrix, we employed lineage-specific mutation of the type II TGFbeta receptor gene (Tgfbr2) in vascular smooth muscle precursors in mice. In both neural crest- and mesoderm-derived smooth muscle, absence of TGFbeta receptor function resulted in a poorly organized vascular elastic matrix in late-stage embryos which was prone to dilation and aneurysm. This defect represents a failure to initiate formation of the elastic matrix, rather than a failure to maintain a preexisting matrix. In mutant tissue, lysyl oxidase expression was substantially reduced, which may contribute to the observed pathology.

Cathepsin cysteine proteases in cardiovascular disease

Extracellular matrix (ECM) remodeling is one of the underlying mechanisms in cardiovascular diseases. Cathepsin cysteine proteases have a central role in ECM remodeling and have been implicated in the development and progression of cardiovascular diseases. Cathepsins also show differential expression in various stages of atherosclerosis, and in vivo knockout studies revealed that deficiency of cathepsin K or S reduces atherosclerosis. Furthermore, cathepsins are involved in lipid metabolism. Cathepsins have the capability to degrade low-density lipoprotein and reduce cholesterol efflux from macrophages, aggravating foam cell formation. Although expression studies also demonstrated differential expression of cathepsins in cardiovascular diseases like aneurysm formation, neointima formation, and neovascularization, in vivo studies to define the exact role of cathepsins in these processes are lacking. Evaluation of the feasibility of cathepsins as a diagnostic tool revealed that serum levels of cathepsins L and S seem to be promising as biomarkers in the diagnosis of atherosclerosis, whereas cathepsin B shows potential as an imaging tool. Furthermore, cathepsin K and S inhibitors showed effectiveness in (pre) clinical evaluation for the treatment of osteoporosis and osteoarthritis, suggesting that cathepsin inhibitors may also have therapeutic effects for the treatment of atherosclerosis.

Endovascular treatment of aneurysms: healing mechanisms in a Swine model are associated with increased expression of matrix metalloproteinases, vascular cell adhesion molecule-1, and vascular endothelial growth factor, and decreased expression of tissue inhibitors of matrix metalloproteinases

BACKGROUND AND PURPOSE

The mechanism of aneurysm healing after coiling remains poorly understood. The purpose of the study was to obtain a better understanding of the cellular and molecular events that are associated with aneurysm healing after endovascular coiling in a swine aneurysm model.

MATERIALS AND METHODS

Twenty sidewall aneurysms were created surgically in common carotid arteries in 10 swine. These aneurysms were embolized immediately after creation by using platinum coils by endovascular means. Two and 12 weeks after implantation, aneurysm samples were collected for histologic and biochemical analysis.

RESULTS

All aneurysms were completely or nearly completely occluded angiographically at the time of embolization and at follow-up. At 2 weeks, aneurysm cavities were filled with inflammatory cells and myofibroblasts. At 12 weeks, aneurysm cavities were filled with richly vascularized fibrous tissue and disorganized collagen bundles. The expression of matrix metalloproteinase (MMP)-2 and -9 was found to be elevated at 2 weeks. Expression remained greater than that in control tissue at 12 weeks but was significantly decreased compared with the earlier time point. Expression of tissue inhibitors of MMPs (TIMPs) was diminished at both time points. Expression of vascular cell adhesion molecule-1 (VCAM-1) and vascular endothelial growth factor (VEGF) was elevated at both 2 weeks and 12 weeks. Endothelial nitric oxide synthase expression was not different from that in controls. Transforming growth factor-beta expression was elevated at 2 weeks only.

CONCLUSION

The coil occlusion in this model that is prone to heal is associated with increased expression of MMP-2, MMP-9, VCAM-1, and VEGF, and decreased expression of TIMPs.

[Evaluation of oxidative stress in experimental rabbit aneurysms]

OBJECTIVE

To evaluate the roles of oxidative stress in the generation and development of aneurysms.

METHODS

Five terminal aneurysms and 8 lateral aneurysms were rebuilt on rabbits, and 6 normal artery vessels were prepared as control. The levels of malondialdehyde (MDA), superoxide dismutase (SOD), and anti-reactive oxygen species unit (anti-ROS unit) were measured with chemical methods.

RESULTS

The levels of MDA in terminal and lateral aneurysms were (33.85 +/- 8.66) and (27.87 +/- 5.78) nmol/mg prot, respectively, which were significantly higher than (10.91 +/- 2.72) nmol/mg prot in control group (P < 0.01). The levels of SOD in terminal and lateral aneurysms were (28.30 +/- 3.58) and (33.00 +/- 8.09) U/mg prot, respectively, which were significantly lower than (127.27 +/- 38.72) U/mg prot in control group (P < 0.01). The levels of anti-ROS unit in terminal and lateral aneurysms were (47.86 +/- 5.00) and (62.64 +/- 13.87) U/ mg prot, respectively, which were significantly lower than (116.94 +/- 9.22) U/mg prot in control group (P < 0.01). No significant differences were shown between terminal aneurysm and lateral aneurysm in MDA and SOD except anti-ROS unit (P = 0.014). MDA had negative correlations with both SOD and anti-ROS unit, and the correlation coefficients were -0. 830 and -0. 852, respectively.

CONCLUSION

Oxidative stress may play an important role in the development of aneurysms. Oxidative stress seems similar among various aneurysms.

A case of spontaneous splenorenal shunt associated with splenic artery aneurysm

A case of large spontaneous splenorenal (S-R) shunt accompanied with splenic artery aneurysm is reported in this paper. The large blood vessel, a shunt, anatomizing the splenic vein and left renal vein is macroscopically found during the autopsy of a 71-year-old male, accompanied with liver cirrhosis and splenomegaly. Though there are many reports demonstrating medical imaging, anatomical findings are relatively poor besides describing and illustrating the appearances of the S-R shunt, the splenic artery aneurysm and related branches of the splenic vein and left renal vein, the embryologic and pathogenetic origins of these anomalies are also discussed with the description of the relationship between the S-R shunt and the splenic artery aneurysm.

Vitamin k epoxide reductase: a protein involved in angiogenesis

Vitamin K epoxide reductase (VKOR) is a newly identified protein which has been reported to convert the epoxide of vitamin K back to vitamin K, a cofactor essential for the posttranslational gamma-carboxylation of several blood coagulation factors. We found that the gene is expressed ubiquitously including vascular endothelial cells, smooth muscle cells, fibroblasts and cardiomyocytes, and is overexpressed in 11 tumor tissues on microarray. Stable transfection of VKOR cDNA into tumor cell line A549 and H7402 did not promote the cell proliferation. These results promoted us to hypothesize that VKOR may also be involved in angiogenesis. To test this hypothesis, the expression of VKOR was studied in different vascular cells in developmental and pathologic heart tissues. The effects of overexpression and suppressing expression of VKOR on endothelial cell proliferation, migration, adhesion, and tubular network formation were explored. We found that VKOR expression in arteries was prominent in vascular endothelial cells and was high in the ventricular aneurysm tissue of human heart and human fetal heart. In vitro studies showed that overexpression of VKOR slightly but significantly stimulated human umbilical vein endothelial cell proliferation (by 120%), migration (by 118%), adhesion (by 117%), as well as tubular network formation. Antisense to VKOR gene inhibited the proliferation (by 67%), migration (by 64%), adhesion (by 50%), and tubular network formation. Our findings support the impact of VKOR in the process of angiogenesis; hence, the molecule may have a potential application in cardiovascular disease and cancer therapy.

Metalloproteinases in Development and Progression of Vascular Disease

Remodeling of the vascular wall plays a role in many physiological processes, but also in the pathogenesis of major cardiovascular diseases such as restenosis and atherosclerosis. Remodeling requires proteolytic activity to degrade components of the extracellular matrix; this can be generated by the matrix metalloproteinase(MMP) system alone or in concert with the fibrinolytic (plasminogen/plasmin) system. Several lines of evidence suggest that the MMP system plays a role in vascular smooth muscle cell migration and neointima formation after vascular injury. In atherosclerotic lesions, active MMPs may contribute to plaque destabilisation by degrading extracellular matrix components, but may also promote aneurysm formation by proteolytic degradation of the elastic lamina. The MMP system may therefore represent a potential therapeutic target for treatment of restenosis or atherosclerosis.

Proteoglycans in Atherosclerosis and Restenosis

The proteoglycan versican is one of several extracellular matrix (ECM) molecules that accumulate in lesions of atherosclerosis and restenosis. Its unique structural features create a highly interactive molecule that binds growth factors, enzymes, lipoproteins, and a variety of other ECM components to influence fundamental events involved in vascular disease. Versican is one of the principal genes that is upregulated after vascular injury and is a prominent component in stented and nonstented restenotic lesions. The synthesis of versican is highly regulated by specific growth factors and cytokines and the principal source of versican is the smooth muscle cell. Versican interacts with hyaluronan, a long chain glycosaminoglycan, to create expanded viscoelastic pericellular matrices that are required for arterial smooth muscle cell (ASMC) proliferation and migration. Versican is also prominent in advanced lesions of atherosclerosis, at the borders of lipid-filled necrotic cores as well as at the plaque-thrombus interface, suggesting roles in lipid accumulation, inflammation, and thrombosis. Versican influences the assembly of ECM and controls elastic fiber fibrillogenesis, which is of fundamental importance in ECM remodeling during vascular disease. Collectively, these studies highlight the critical importance of this specific ECM component in atherosclerosis and restenosis.

Different expression of MMPs/TIMP-1 in human atherosclerotic lesions. Relation to plaque features and vascular bed

BACKGROUND

Proteolytic imbalance might determine arterial remodeling and plaque destabilization in atherosclerotic vessels. The aim of this study was to examine differences in the patterns of metalloproteinases (MMPs) and MMP inhibitor (TIMP-1) expression in advanced human atheromas, both in relation to the plaque features and the vascular bed involved.

METHODS AND RESULTS

Immunohistochemistry for MMP-1, -3, -9 and TIMP-1 as well as the collagen content were measured in vascular sections from patients undergoing peripheral revascularization (carotid n=11, femoral n=23) and aorto-coronary bypass surgery (mammary arteries n=20, as controls). Increased expression of all MMPs was detected in atherosclerotic as compared with control sections (P<0.01). Aneurysmal plaques showed a significant increase of MMP-1 and-3 and a reduction in total collagen (P<0.05) in relation to occlusive lesions. Calcification areas in atherosclerotic plaques were consistently associated with increased TIMP-1 expression (P<0.01). Finally, MMP-9 expression was higher in occlusive lesions from carotid than femoral arteries (P<0.01).

CONCLUSIONS

Aneurysm lesions expressed higher MMP-1 and-3 expression than occlusive plaques, and MMP-9 was mainly detected in carotid as compared with femoral arteries. TIMP-1 was associated with arterial calcification. These differences in the MMPs/TIMP-1 expression might determine the evolution of advanced atherosclerotic plaques and contribute to its vulnerability.

Non-uniform distribution of lesions and biochemical abnormalities within the retina of diabetic humans

OBJECTIVE

Microaneurysms, acellular capillaries, pericyte ghosts, and thickening of retinal capillary basement membrane are characteristic of diabetic retinopathy, and are believed to be sequelae of excessive blood glucose. Previous studies by us in dogs demonstrated that lesions of diabetic retinopathy were not uniformly distributed across the retina, but were significantly more numerous in the superior/temporal areas of the retina. In the present study, the distribution of these lesions and the biochemical abnormalities postulated to play a role in their pathogenesis have been evaluated in retinas collected at autopsy from diabetic patients.

METHODS

Retinas were divided into quadrants (nasal, temporal, superior, inferior), the vasculature exposed by the trypsin-digest method, and the frequency of the lesions compared among the quadrants. Homogenates taken from the mid-retina of nasal and temporal quadrants of retina were used to explore regional differences in expression of Glut1, PKCbeta, and iNOS (Western blots) and caspases (enzymatic activity).

RESULTS

Microaneurysms, acellular capillaries and pericyte ghosts were not uniformly distributed across the retina, and were significantly more numerous in the temporal retina than in the nasal retina (P < 0.05). In contrast, the thickness of retinal capillary basement membrane was not found to differ significantly across the retina. In our limited study, activity of the pro-inflammatory protease, caspase 1, was the only biochemical abnormality where there was both a significant diabetes-induced alteration in activity and also a significant difference between retinal quadrants. Expression of the glucose transporter, Glut1, was significanlty decreased in diabetes, but there was no significant difference in expression between the quadrants. Expression of iNOS was increased only in temporal retina in diabetes (but no significant difference between quadrants), and PKCbeta tended to be greater than normal in both temporal and nasal retina.

CONCLUSIONS

Retinal microvascular disease does not develop uniformly across the retina of diabetic patients, even though the different regions are exposed to the same level of hyperglycemia.

High levels of serum soluble CD27 correlated with renal dysfunction

CD27 is expressed on lymphocytes, but also on renal tubules. On the damaged renal tubules, CD27 is cleaved into soluble CD27 (sCD27) and cytoplasmic tail CD27. Renal tubule apoptosis is induced by the CD27 ligand, Siva, binding to the truncated tail CD27. Theoretically, serum sCD27 should be a marker of renal tubule apoptosis. Serum sCD27 levels were measured by ELISA in 274 patients at University Hospital School of Medicine, Japan. Among 73 males and 63 females with high plasma creatinine levels, 68 (93%) males and 51 (81%) females showed high serum sCD27 values (>or=500 U/ml). In the 42 males with plasma creatinine levels of 1.18-5.00 mg/dl and the 55 females with plasma creatinine levels of 0.83-4.65 mg/dl, the correlation coefficients between plasma creatinine and sCD27 were 0.605 and 0.469, respectively. SCD27 was a more sensitive marker of renal tubule apoptosis than plasma creatinine. Of 138 patients with normal plasma creatinine, 42 showed high serum sCD27 levels (>or=500 U/ml). Among the 42 patients, 19 patients had high blood urea nitrogen and 11 patients showed plasma creatinine elevations 3-11 days later. Nine patients with hemolysis and 39 patients with aneurysms had clearly higher sCD27 levels of 1633+/-483 U/ml and 905+/-437 U/ml, respectively, than normal values of 215+/-57 U/ml ( n=27) ( P value >or=0.001). Vasodilators, hypotensors, diuretics, and drugs for gout, arrhythmia, thrombosis, and diabetes were prescribed in 40%, 37%, 33%, 13%, 8%, 8%, and 5% of the 78 patients analyzed with high sCD27 levels (>or=500 U/ml). In total, 59 (76%) patients were prescribed at least one of the drugs. In conclusion, serum sCD27 was a more sensitive indicator of renal tubule apoptosis than plasma creatinine, especially during the early stage of apoptosis. Tubule apoptosis with high serum sCD27 levels was found in patients with glomerular vascular injuries.

Mechanism of vasculitis and aneurysms in Kawasaki disease: role of nitric oxide

NO in vivo has both beneficial and nonbeneficial effects depending on site and concentration. Peroxynitrite, resulting from the reaction of NO with superoxide radical, causes cellular damage. Nitrotyrosine, end product of NO's toxic effects on cellular proteins, is a stable compound that can be used to detect evidence of harmful quantities of NO. We sought to detect nitrotyrosine in coronary arterioles of DBA/2 mice injected intraperitoneally with Lactobacillus casei cell wall. The inflammatory response induced occurred in perivascular fashion and involved mainly macrophages. It was variable according to time points, being severe on days 10 and 14 and mild to moderate on days 3 and 7. Few basal inflammatory cells appeared in controls injected with phosphate-buffered saline. Western immunoblots of homogenized hearts on days 10 and 14 demonstrated specific nitrated proteins. Immunohistochemistry of frozen sections of diseased hearts showed positive immunoreactivity for nitrotyrosine in coronary arterioles at the same time points. These findings were absent in the controls. We also determined the expression of inducible nitric oxide synthase (iNOS) in controls on days 10 and 14. iNOS colocalized with nitrotyrosine in perivascular macrophages and coronary arterioles of treated mice. Additionally, aneurysms were found on day 10 and intracardiac hemorrhage with consequent death on day 14. These observations supply evidence that NO through its reactive product, peroxynitrite, and its antigen/tissue marker, nitrotyrosine, is directly involved in coronary arteritis and aneurysm development in mice models of Kawasaki disease (KD). This article shows that macrophages are central to this and bolsters the likelihood of L. casei being the cause of KD.

Systemic production of vascular endothelial growth factor and fms-like tyrosine kinase-1 receptor in acute Kawasaki disease

BACKGROUND

Increased vascular permeability is an important event during the initial process of Kawasaki disease (KD). One potential responsible candidate for the induction of vascular hyperpermeability is vascular endothelial growth factor (VEGF).

METHODS AND RESULTS

We investigated the expression of VEGF and its receptors (flt-1, KDR) in acute KD tissues at 7 days to 5 weeks of illness. Neuropilin-1, which enhances the binding of VEGF(165) to KDR, was also studied. Abundant expression of VEGF and flt-1 was documented immunohistochemically in many organs from acute KD, including heart and lung. VEGF and flt-1 were colocalized in all vessels that showed edema. These molecules resided in endothelium and vascular media and also in migrating smooth muscle cells in neointima and infiltrating macrophages. Compared with controls, coronary vessels of acute KD had upregulation of VEGF and flt-1 but not KDR or neuropilin-1. KDR was expressed by vessels at 7 days of illness but not later in the illness. Plasma proteins were more extensively bound to the extracellular matrix in coronary vessels in acute KD than controls. Furthermore, elevation of serum VEGF levels was correlated with low serum albumin in acute KD (n=220, r=-0.53, P<0.001).

CONCLUSIONS

These findings suggest that VEGF and flt-1 are upregulated in blood vessels in many organs of acute KD. Expression of KDR was limited to the early stage of acute KD. The roles of VEGF in acute KD may involve promotion of vascular permeability and macrophage activation. Low serum albumin may indicate overproduction of VEGF in acute KD.

Initial steps in the unifying theory of the pathogenesis of artery aneurysms

OBJECTIVES

The objective of this study was to investigate the changes in histology and proteolysis and the role of apoptosis in the development of peripheral artery aneurysms.

METHODS

Eighteen popliteal, 6 abdominal aortic, 10 iliac, 2 carotid, and 6 femoral artery aneurysm specimens were obtained from patients undergoing elective surgical repair. All were males with ages 48 to 93 (mean 71 years). Normal controls were obtained from patients matched for age, sex, and major risk factors. Vascular smooth muscle cells (VSMC), macrophages, T lymphocytes, and apoptosis-regulating molecules were detected immunohistochemically. Detection of apoptosis was by TUNEL assay. Proteolytic activity was determined by 10% gelatin gel zymography.

RESULTS

Paucity of VSMCs, increased amount of inflammatory infiltrate, and fragmentation of elastic lamellae were observed in aneurysmal tissues as compared to normal arteries (P < 0.02). There is increased gelatinolytic activity at 92, 84, 72, and 67 kDa in the aneurysmal tissues. There are fewer CD68+ macrophages and T cells in the media of controls than in the aneurysms (P = 0.01). Apoptosis is significantly high in aneurysm tissues (P < 0.01) and the degree of apoptosis was in the order AAA>FAA>PAA>IAA>CAA. There is increased expression of Bax, CPP-32, Fas, and p53 in PAA specimens as compared to normal popliteal arteries (P < 0.05).

CONCLUSIONS

These data confirm the apparent architectural disruption and loss of VSMCs that are hallmarks of aneurysm development, in peripheral artery aneurysms. Apoptosis and signaling molecules capable of initiating cell death may play a significant role in the pathogenesis of all aneurysms. Our data suggest a common etiology between the various types of aneurysms.

Persistence of atherosclerotic plaque but reduced aneurysm formation in mice with stromelysin-1 (MMP-3) gene inactivation

To investigate a potential role for stromelysin-1 (MMP-3) in the development and progression of atherosclerotic lesions and aneurysm formation, mice with a deficiency of apolipoprotein E (ApoE(-/-):MMP-3(+/+))) or with a combined deficiency of apoE and MMP-3 (ApoE(-/-):MMP-3(-/-)) were kept on a cholesterol-rich diet for 30 weeks. Atherosclerotic lesions throughout the thoracic aorta were significantly larger in ApoE(-/-):MMP-3(-/-) than in ApoE(-/-):MMP-3(+/+) mice (P<0.05) and contained more fibrillar collagen (P<0.01). Aneurysms in the thoracic and abdominal aortas were less frequent in ApoE(-/-):MMP-3(-/-) than in ApoE(-/-):MMP-3(+/+) mice (8.5+/-1.7% vs 14+/-2.1% of sections, mean+/-SD, P<0.01). Immunocytochemistry revealed enhanced accumulation of macrophages in atherosclerotic lesions of ApoE(-/-):MMP-3(+/+) mice (P<0.01) and expression of urokinase-type plasminogen activator (u-PA) and MMP-3 colocalizing with macrophages. Zymography confirmed the presence of u-PA and MMP-3 activity in extracts of atherosclerotic aortas. These data suggest that plasmin, generated by macrophage-secreted u-PA, activates pro-MMP-3 produced by accumulated macrophages. MMP-3 activity may then contribute to a reduction of plaque size, possibly by degradation of matrix components, and promote aneurysm formation by degradation of the elastica lamina.

Extracellular matrix remodeling in the vascular wall

The extracellular matrix provides a structural framework essential for the functional properties of vessel walls. The three dimensional organization of the extracellular matrix molecules--elastin, collagens, proteoglycans and structural glycoproteins--synthesized during fetal development--is optimal for these functions. Early in life, the vessel wall is subjected to injury: lipid deposition, hypoxia, enzyme secretion and reactive oxygen species production during inflammatory processes, and the extracellular matrix molecules are hydrolyzed by proteases--matrix metalloproteinases, leukocyte elastase, etc. In uninjured arteries and veins, some proteases are constitutively expressed, but through the control of their activation and/or their inhibition by inhibitors, these proteases have a very low activity. During the occurrence of vascular pathologies--atherosclerosis, hypertension, varicosis, restenosis, etc.--the balance between proteases and their inhibitors is temporally destroyed through the induction of matrix metalloproteinase gene expression or the secretion of enzymes by inflammatory cells. Smooth muscle cells, the most numerous cells in vascular walls, have a high ability to respond to injury through their ability to synthesize extracellular matrix molecules and protease inhibitors. However, the three dimensional organization of the newly synthesized extracellular matrix is never functionally optimal. In some other pathologies--aneurysm--the injury overcomes the responsive capacity of smooth muscle cells and the quantity of extracellular matrix decreases. In conclusion, care should be taken to maintain the vascular extracellular matrix reserve and any therapeutic manipulation of the protease/inhibitor balance must be perfectly controlled, because an accumulation of abnormal extracellular matrix may have unforeseen adverse effects.

High accumulation of plasminogen and tissue plasminogen activator at the flow surface of mural fibrin in the human arterial system

PURPOSE

We assessed the fibrinolytic activity of the organized mural thrombus lining of aneurysms and prosthetic grafts.

METHODS

Between May 1995 and April 1998, the full-thickness mural thrombi of aneurysms and the pseudointima lining of vascular grafts were obtained from 12 patients, ranging from 55 to 78 years in age, who underwent elective surgery. These included five aortic arch aneurysms, four abdominal aortic aneurysms, and three patent synthetic vascular grafts. The specimens were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE)/immunoblot and immunohistochemistry for human plasmin/plasminogen, tissue plasminogen activator (tPA), and fibrin degradation product (D-dimer).

RESULTS

In the SDS-PAGE/immunoblot, 25- and 27-kd bands appeared specifically in experimental fibrin plates after limited digestion by plasmin and were also recognized in the mural thrombi. The presence of bands at 25 and 27 kd, which were most prominent in sections near the flow surface layer, was consistent with the hypothesis that the mural fibrin was digested by the endogenous plasmin. Apparent immunoreactivity was found at the flow surface of the masses at a thickness of 10 to 400 micrometer suggesting the presence of a plasminogen and tPA-rich layer, with D-dimer as a consequential product of fibrinolysis.

CONCLUSION

The hypothesis that fibrin surfaces in the arterial system acquire fibrinolytic activity because of digestion by circulating endogenous plasmin was confirmed; this may contribute to the antithrombogenicity of these flow surfaces.

Renal involvement of thrombotic thrombocytopenic purpura: special reference to the glomeruloid structures

We report the case of a 9-year-old girl with biopsy-proven renal thrombotic microangiopathy in thrombotic thrombocytopenic purpura (TTP), with particular reference to the glomeruloid structures. The renal biopsy sample from this TTP patient revealed platelet thrombus deposition, a glomeruloid structure and aneurysm with relative sparing of the glomeruli. The glomeruloid structure displayed a proliferation of mainly capillary-sized channels lined by Factor VIII-related, antigen-positive plump endothelial cells embedded in the edematous connective tissue. These glomeruloid vessels communicated with the aneurysmal segment at the end portion of the arteriolar branch. We believe that the glomeruloid structures in TTP represent not merely organization or recanalization of thrombus but rather active angiogenesis through aneurysmal dilation in the arteriolized vessel, probably initiated by platelet agglutination.

Ultrastructural changes in a case of mucoid degeneration of the brachial artery

An electron microscopic (EM) description of mucoid degeneration of the brachial artery in a 67 year old man is presented. In this case, the affected artery showed mucoid degeneration of the intima and media circumferentially, dissecting and destroying the muscle fibres. Ultrastructurally, mucoid degenerating muscle cells showed numerous large mucin-containing vesicles in the cytoplasm. Cells were widely separated by large accumulation of mucoid material, which appeared to penetrate the extracellular collagen fibre bundles. Most of the nuclei of the smooth muscle cells displayed typical necrotic changes undergoing dissolution or having already broken up into discrete fragments. This case of intimo-medial degeneration (IMMD) suggests that the condition could arise spontaneously anywhere in the inner coats of the arterial system away from the vessels that are close to synovial joints. This is a rare presentation of IMMD of arteries, which has been described mainly in the aorta and its major branches.

Demonstration of microaneurysms at the interlobular arteries of the kidneys in microscopic polyangiitis: a three-dimensional study

Aneurysms, mostly saccular, of the medium-sized muscular arteries are frequently encountered in classic polyarteritis nodosa, whereas their occurrence in smaller arteries is unclear. The objective of this study is to clarify the three-dimensional morphology of the small-sized muscular arteries involved in microscopic polyangiitis (MPA). Six autopsy cases of MPA of the acute inflammatory stage were chosen. Using serial paraffin-embedded sections of the kidney, vasculitic lesions observed in the interlobular arteries were three-dimensionally reconstructed. All of the 19 lesions showed microaneurysms, of which 18 were sausage-shaped and the other was saccular. In the former type, average outer diameter at the most expanded point was 235.4 +/- 83.8 microm (mean +/- SD), which was 2.78 +/- 0.73 times that of an uninvolved adjacent arterial diameter. The major axis-minor axis ratio in a cross-aneurysmal section was 1.17 +/- 0.16, indicating rather regular centrifugal expansion of the aneurysm. The aneurysmal length was 742.7 +/- 254.8 microm. These sausage-type aneurysms showed whole circumferential vasculitic involvement, whereas the saccular-type aneurysm contained an uninvolved arterial portion. In both types, the luminal spaces showed similar three-dimensional features to the outer surface of microaneurysms It was concluded that the interlobular arteries of the kidneys in MPA were characterized by formation of microaneurysms, most of which were sausage-shaped

Clinicopathologic findings in congenital aneurysms of the great vessels

We describe the clinical, histopathologic, and angiographic findings in four children with congenital abnormalities of the great vessels of unknown cause, comprising either single or multiple arterial aneurysms, aortic/arterial dilatation, vessel tortuosity, or combinations of these abnormalities. Two children had early and severe respiratory distress due to aneurysmal compression of the trachea. All children had diffuse dilatation of several arteries, and two children also had tortuosity of multiple arteries. Progression of these abnormalities was clearly evident in one child, in whom diffuse vessel irregularity and tortuosity affected intra-abdominal, and intra and extra-cranial arteries. One child died at 5 years, while the other three have undergone successful surgical repair in the first 3 months of life and are now well, between age 2.5 and 7 years. The phenotype of each child appears unique but all have in common the rare finding of aneurysms of the aorta and main pulmonary artery. Congenital aortic aneurysms did not occur as an isolated finding in any of these children.

Multiple defects in type III collagen synthesis are associated with the pathogenesis of abdominal aortic aneurysms

Confluent skin fibroblast cultures were prepared from 40 patients diagnosed with and surgically treated for an abdominal aortic aneurysm. An analysis of secreted type I and type III collagen in the media of these fibroblast preparations revealed reduced secretion of type III collagen from six patients. DNA sequence analysis of the entire coding domain of the pro alpha 1 (III) collagen mRNA in skin fibroblast RNA from these six patients revealed a C to T substitution at nucleotide 607 in one of the probands that would result in the replacement of a leucine residue with phenylalanine in the second position of the first tripeptide repeat in the triple-helical domain of type III collagen. Allele-specific hybridization analysis of genomic DNA from this proband and family members indicated that this non-glycine substitution probably contributed to the aneurysmal phenotype in this patient. No coding sequence mutations were found in the other five patients. It is clear from this study, therefore, that aberrant synthesis of type III collagen, as a consequence of both a coding sequence mutation and other factors contributing to reduced secretion of type III procollagen, will result in the development of an aortic aneurysm in a significant percentage of patients with this disease.

Changes in phospholipids and acetylcholinesterase during early phase of injury to spinal cord--an experimental study in rats

Injury to spinal cord was produced in rats by the clip compression technique by placing the aneurysm clip extradurally for 30 seconds. The traumatised spinal segment and the adjoining upper segment were used for biochemical estimations. Motor function of the injured rats was evaluated using the inclined plane. Phospholipid phosphorus values were significantly decreased in the injured spinal segment at 24 hrs. AchE activity was also decreased in the traumatised segment one week after injury. Dexamethasone and verapamil reversed the changes in AchE activity at the end of one week. At the one week assessment period, aneurysm clipped rats showed a decrease in the maximum angle in the inclined plane. Dexamethasone and verapamil treated rats showed improvement in the neurologic function, neurologic recovery was better in the dexamethasone treated group.

Aneurysmal and haemangiopericytoma-like fibrous histiocytoma

AIM

To describe the clinicopathological features of 33 aneurysmal fibrous histiocytomas (AFH), including five cases with a haemangiopericytoma-like pattern.

METHODS

Thirty three cases of AFH were studied by using routine histology and immunohistochemistry for factor XIIIa, the "cell activity marker" E9 (anti-metallothionein), NK1C3 (CD57), smooth muscle actin (SMA), factor VIII, ulex europaeus agglutinin, JC70A (CD31), and QBEND10 (CD34). The time dependent variation in histopathological features was evaluated by statistical methods (Pearson chi 2, likelihood ratio chi 2).

RESULTS

Of the AFHs, 29 of 33 occurred on the extremities of adults (age range 30 to 50 years), six of which were associated with rapid growth, probably caused by trauma, and pain. Twenty one lesions were thought to be vascular and/or melanocytic lesions, including two melanomas, because of a bluish-black and/or cystic appearance. Histologically, large areas of haemorrhage, up to 50% of the tumour bulk, lacking an endothelial lining were seen in otherwise typical fibrous histiocytomas. Five cases resembled nodular stages of Kaposi's sarcoma. Variable haemosiderin deposition in histiocytes (18/33) and giant cells (11/33) was suggestive of haemosiderotic histiocytoma. A haemangiopericytoma-like pattern was seen in five otherwise indistinguishable cases. On immunohistochemistry, variable reactivity was seen for factor XIIIa (18/30), with E9 (18/30), NK1C3 (19/30), and for SMA (14/30), but labelling for vascular markers was not detected. Early lesions without iron deposition were factor XIIIa positive; late lesions with iron deposition were factor XIIIa negative. Labelling for SMA correlated with prominent sclerosis.

CONCLUSION

AFHs, including a haemangiopericytoma-like variant, have a characteristic time dependent histological and immunophenotypic profile, clearly different from nodular type Kaposi's sarcoma.

Failure of elastin or collagen as possible critical connective tissue alterations underlying aneurysmal dilatation

Previous studies in the authors' laboratory have demonstrated that degradation of arterial elastin produces vessel dilatation, decreased vessel distensibility, and vessel elongation which can cause tortuosity. By contrast, degradation of collagen produces increased vessel distensibility and rupture. However, neither degradation of elastin nor of collagen produced the true gross enlargement characteristic of human aneurysms. The present study was performed to identify the connective tissue critical to aneurysm formation. Vessel dimensions were measured repeatedly in human arteries during progressive enzymatic degradation. Experiments were performed on six intact human common, external and internal iliac arteries, and two aneurysmal human common iliac arteries. The vessels were mounted in vitro and subjected to pressure steps up to 200 mmHg while diameters were measured. Repeated pressure-diameter curves were obtained for up to 18 h during treatment with elastase or collagenase. Degradation of elastin produced moderate dilatation (6-10% at 100 mmHg) with decreased vessel distensibility; this occurred as the load was shifted to remaining collagen. Degradation of collagen produced greater dilatation (10-23% at 100 mmHg), increased distensibility, and vessel rupture. These findings suggest that the critical element in both the gross enlargement and rupture of aneurysms resides in collagen. They also suggest that, in vessels obtained from patients with a family history of aneurysms, defects should be sought in: (i) the structure of collagen; (ii) increased susceptibility of collagen to degradation by endogenous mechanisms; (iii) increased endogenous collagenolytic activity; or (iv) decreased inhibition of endogenous collagenolytic activities.

Changes in collagen fibril morphology in experimental aneurysms and arteriovenous fistulae in sheep

To investigate the effect of haemodynamic stress on collagen fibril morphology, the ultrastructure of intimal and adventitial collagen in the walls of experimental saccular aneurysms and in the veins of arteriovenous fistulae in sheep was compared with that of adventitial collagen from control veins. Ultrastructurally the collagen fibril is usually described as having a regular round profile in cross-section and a diameter dependent on collagen function and location in the blood vessel wall. The collagen fibrils in the intimal proliferation from both experimental models showed increased variation in shape and size when compared with adventitial collagen. These abnormally shaped collagen fibrils resemble those seen in inherited connective tissue disorders and in blood vessels from aged animals, suggesting that the collagen changes can be acquired and can be produced experimentally in blood vessels subjected to augmented haemodynamic stress.

Extraaortic intimomedial mucoid degeneration: a clinicopathological study

Six black patients with extraaortic intimomedial mucoid degeneration of the major arterial branches of the aorta are reported. Five patients presented with aneurysmal dilatation of the arterial wall as a result of the intimomedial mucoid degeneration, and the sixth patient had superimposed occlusive thrombosis. The ages ranged from twenty to fifty years. Five patients were female. Two were hypertensive. All patients in this study underwent reconstructive vascular surgery. The clinical and histopathologic findings are discussed.

The Charcôt-Bouchard aneurysm controversy: impact of a new histologic technique

For over a century a controversy has existed about the prevalence and significance of Charcôt-Bouchard (C-B) aneurysms, especially regarding their relationship to intracerebral hemorrhage (ICH) in man. We reassessed C-B aneurysms by staining thick brain sections from 35 hypertensives and 20 normotensives with the alkaline phosphatase (AP) endothelial stain followed by light microscopy and high-resolution microradiography. Charcôt-Bouchard aneurysms were conspicuously absent in both groups which included four cases of hypertensive ICH. The three-dimensional perspective and enhanced ability to trace vessels with these techniques helped to identify arteriolar coils and twists that can be mistaken for aneurysms when demonstrated by injection methods. Routine brain pathologic sections from 2,800 autopsies over a decade showed rare examples of parenchymal aneurysms. We conclude that elimination in our study of a) injection artifacts and b) misinterpretations shows that C-B aneurysms are uncommon and have little relationship to ICH. Despite this, and in view of the original contribution of Charcôt and Bouchard, the occasional examples of brain parenchymal aneurysms should continue to bear their names.

[Pathogenesis of acquired abdominal aortic aneurysms]

Abdominal aortic aneurysms are the result of a destructive process of the aortic media. The incidence of abdominal aortic aneurysms is increasing but the reasons remain unknown. The mechanical and structural characteristics of the abdominal aorta explain the frequency of acquired aneurysms at this location. Classically, atherosclerosis is the main etiologic factor, but the abdominal aortic aneurysm is distinguishable from the aged aorta and occlusive atherosclerotic disease by the apparent absence of a reparative process. Some authors have tried to differentiate aneurysmal disease from occlusive atherosclerotic disease. Atherosclerosis could lead to plaque and stenosis or, in some unknown circumstances, to atrophy of the media and aneurysmal dilation. Proteolytic enzymes within the aortic wall play an important role in the destruction of the extracellular matrix of the aortic wall. Plasmin could locally worsen the proteolysis. Inflammatory cells might be responsible for these proteolytic activities. Calcium could play a role in the activation of inflammatory cells. Genetic markers and familial grouping have been reported by several authors. The discovery of constitutional or acquired factors that could lead to activation of degradative phenomena within the aortic wall will facilitate the identification of patients at risk, and improve screening of asymptomatic aneurysms.

Distribution of type IV collagen, laminin, nidogen and fibronectin in the haemodynamically stressed vascular wall

Changes in the extracellular matrix of haemodynamically stressed blood vessel walls were studied by immunofluorescence histochemistry in venous-pouch aneurysms fashioned on the site of the common carotid artery of nine sheep. Tissues from the thickened walls of the experimental aneurysms were examined from 11 to 98 months post-operatively for changes in the distribution of the basement membrane components type IV collagen, laminin, nidogen and fibronectin. In the younger aneurysms, there was an increase of the basement membrane components in the thickened area. Very little basement membrane was detected in older aneurysms. Diffuse staining for fibronectin was noted in aneurysms of all ages. Thick deposits of basement membrane material were observed in calcified tissues. The changes in the matrix proteins were similar to alterations occurring during the development of atherosclerosis in human vascular tissue.

Type VI collagen in experimental atherosclerosis

Diffuse intercellular immunofluorescence staining of type VI collagen was found in the experimentally thickened vascular wall and in control blood vessel tissues as well, superimposed by more intense staining around basement membranes. While the basement membrane staining disappeared in advanced mural thickenings, the diffusely distributed network of type VI collagen remained.

X-ray microanalysis of mineralized matrix vesicles of experimental saccular aneurysms

An energy dispersive X-ray microanalytical study was designed to examine the mineral deposits in matrix vesicles found in the walls of experimental aneurysms from two rabbits (103 and 1071 days postoperatively) and two sheep aneurysms (234 and 1202 days postoperatively). The freeze-substitution technique was adopted for use to retain inorganic ions in situ. Numerous, various sized extracellular electron-dense structures, believed to be matrix vesicles were observed. Size histograms for the mineralized vesicles showed that the proportion of smaller vesicles was higher in the older animals. A total of 370 vesicles were analyzed. Calcium and phosphorus with small amounts of magnesium were identified. No particular calcium phosphate mineral was dominant with the mean Ca/P molar ratio for all animals falling in the 1.1-1.2 range. Correlation coefficients for interrelationships between calcium, phosphorus, magnesium, and size were weak except for calcium vs phosphorus which was close to one, consistent with some type of calcium phosphate being the major constituent of the mineralized vesicles. Smaller electron-dense particles, probably mitochondrial granules were seen in some smooth muscle cells; a small number were analyzed and contained calcium and phosphorus (mean Ca/P molar ratio of 0.86) but no magnesium.

An experimental model of calcification in the vessel wall

Multiple angiolytic changes of the mesenteric arteries due to administration of vast amounts of Na2EDTA into the peritoneal cavity of guinea pigs have already been demonstrated by Yamaguchi et al. (1981 a, b). In this experiment, one week after Na2EDTA administration calcium lactate was administered in the same manner. As a result calcium deposition was observed in the intimal elastic fibers, in and at the collagenous fibers and intermuscular spaces of lytic and ensuing dilatated areas of the vascular wall. This suggests that dystrophic calcification might be induced by conjugation of calcium ions to the free negative charges of acid mucopolysaccharides (aMPS) which are the main component of the above structural elements.