Temporal Artery Specimens Research Articles

Upregulated Cytoskeletal Proteins Promote Pathological Angiogenesis in Moyamoya Disease.

Moyamoya disease (MMD) is a rare progressive vascular disease that leads to intracranial internal carotid artery stenosis and eventual occlusion. However, its pathogenesis remains unclear. The purpose of this study is to explore the role of abnormally expressed proteins in the pathogenesis of MMD. Data-independent acquisition mass spectrometry identifies the differentially expressed proteins in MMD serum by detecting the serum from 60 patients with MMD and 20 health controls. The differentially expressed proteins were validated using enzyme linked immunosorbent assays. Immunofluorescence for superficial temporal artery and middle cerebral artery specimens was used to explore the morphological changes of vascular wall in MMD. In vitro experiments were used to explore the changes and mechanisms of differentially expressed proteins on endothelial cells. Proteomic analysis showed that a total of 14 726 peptides and 1555 proteins were quantified by mass spectrometry data. FLNA (filamin A) and ZYX (zyxin) proteins were significantly higher in MMD serum compared with those in health controls (Log2FC >2.9 and >2.8, respectively). Immunofluorescence revealed an intimal hyperplasia in superficial temporal artery and middle cerebral artery specimens of MMD. FLNA and ZYX proteins increased the proportion of endothelial cells in S phase and promoted their proliferation, angiogenesis, and cytoskeleton enlargement. Mechanistic studies revealed that AKT (serine/threonine kinase)/GSK-3β (glycogen synthase kinase 3β)/β-catenin signaling pathway plays a major role in these FLNA- and ZYX-induced changes in endothelial cells. This study provides proteomic data on a large sample size of MMD. The differential expression of FLNA and ZYX in patient with MMD and following in vitro experiments suggest that these upregulated proteins are related to the pathology of cerebrovascular intimal hyperplasia in MMD and are involved in MMD pathogenesis, with diagnostic and therapeutic ramifications.

Age-related histopathological findings in temporal arteries.

Giant cell arteritis (GCA) is a systemic vasculitis affecting medium and large arteries in patients aged over 50 years. Involvement of temporal arteries (TA) can lead to complications such as blindness and stroke. While the diagnostic gold standard is temporal artery biopsy (TAB), comorbidities and age-related changes can make interpretation of such specimens difficult. This study aims to establish a baseline of TA changes in subjects without GCA to facilitate the interpretation of TAB. Bilateral TA specimens were collected from 100 consecutive eligible postmortem examinations. Subjects were divided into four age groups and specimens semiquantitatively evaluated for eccentric intimal fibroplasia, disruption and calcification of the internal elastic lamina (IEL), medial attenuation and degree of lymphocytic inflammation of the peri-adventitia, adventitia, media and intima. The individual scores of intimal fibroplasia, IEL disruption and medial attenuation were added to yield a 'combined score (CS)'. Seventy-eight 78 decedents were included in the final analysis following exclusion of 22 individuals for either lack of clinical information or inability to collect TA tissue. A total of 128 temporal artery specimens (50 bilateral from individual decedents, 28unilateral) were available for examination. Intimalproliferation, IEL loss, IEL calcification and CS increased with age in a statistically significant fashion. Comparison of the oldest age group with the others showed statistically significant differences, although this was not uniformly preserved in comparison between the three youngest groups. Senescent arterial changes and healed GCA exhibit histological similarity and such changes increase proportionally with age. The CS demonstrates significant association with age overall and represents a potential avenue for development to 'normalise' TA biopsies from older individuals.

The sensitivity of temporal artery biopsy in the detection of giant cell arteritis is independent of tissue length

Abstract Introduction/Objective Giant cell arteritis (GCA) is the most common vasculitis of the elderly, and the most common primary systemic vasculitis overall, with an annual incidence of 200/million. The long term sequelae, namely vision loss and stroke, are permanent and devastating. While GCA is often treated empirically based on clinical presentation, panarteritis on temporal artery biopsy is required for diagnosis. However, these biopsies have the tendency to be falsely negative due to skip lesions, a common feature of GCA. Therefore, we set out to determine whether longer biopsy specimens were more sensitive in the detection of GCA. Methods/Case Report A census of temporal artery biopsies performed with the indication of clinical symptoms of GCA was taken at our institution. The patient age, sex, biopsy laterality, biopsy length, and pathological diagnosis were recorded for each cataloged sample. Statistical significance of difference in biopsy length was tested using an unpaired t-test in R 4.1.0. Results (if a Case Study enter NA) A total of 114 temporal artery specimens were biopsied from 94 different patients with the indication of GCA and assigned a definitive positive or negative diagnosis. Of the 94 patients, 54 were female and 40 were male. Of the total pathological specimens, 11 were positive and 103 were negative. The overall average length of biopsy specimens was 2.13 cm with a standard deviation of 0.65 cm. The average positive biopsy was 2.26 cm long, and the average negative was 2.12 cm, an insignificant difference (0.14 cm, t = 0.7, p = 0.43). In 25 patients, biopsies were taken from both the left and right temporal arteries. Of those patients, 2 were positive for GCA and the remaining 23 were negative. Interestingly, the biopsy result in every case was identical between the left and right samples; we found no instances of pathological evidence of GCA in only one of the two samples from the same patient. Conclusion According to data taken at our institution, there is no indication to lengthen the biopsy requirements from the existing 1.5 cm. However, we have demonstrated evidence that it may be unnecessary to biopsy both temporal arteries in a single patient. Larger studies would be required to confirm our findings.

Glucocorticoid Effects on Tissue Residing Immune Cells in Giant Cell Arteritis: Importance of GM-CSF.

Giant cell arteritis (GCA) is a systemic granulomatous vasculitis clinically characterized by a prompt response to glucocorticoid therapy. Dendritic cells (DCs) play a central role in the pathogenesis of the disease and are increased in temporal arteries from GCA patients. The aim of this study was to determine the effects of glucocorticoid therapy on granulomatous infiltrates and on peripheral DCs of GCA patients. Immunohistochemical staining of temporal artery specimens from 41 GCA patients revealed a rapid reduction of the number of DCs after initiation of glucocorticoid treatment. TUNEL staining was performed to quantify apoptotic S100+ DC, CD3+ T cells, and CD68+ macrophages in the granulomatous infiltrates. An increase of apoptotic cells up to 9 ± 2% after 4–5 days of glucocorticoid therapy and up to 27 ± 5% (p < 0.001, compared to earlier timepoints) after 6–10 days was detected. A decrease of CCL19 and CCL21 expression was observed after starting glucocorticoid therapy. Granulocyte-macrophage colony-stimulating factor (GM-CSF) expression also significantly decreased under glucocorticoid therapy. No GM-CSF expression was detected in the control specimens. Glucocorticoid therapy leads to a rapid, time-dependent reduction of DCs in temporal arteries from GCA patients and reduction of mediators for cell migration. Our data suggest GM-CSF as a novel therapeutic target of GCA.

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β-amyloid wall deposit of temporal artery in subjects with spontaneous intracerebral haemorrhage.

BackgroundCerebral Amyloid Angiopathy has been indicated as an important cause of spontaneous non-hypertensive intracerebral haemorrhage (ICH).Aimsto analyze the presence of β-amyloid deposit in the temporal artery of consecutive patients with ICH in comparison to control subjects and its relation to APO-E haplotype frequency.MethodsWe enrolled consecutive patients admitted to Neurosurgery Ward of University Hospital “P. Giaccone” of Palermo with a diagnosis of spontaneous non hypertensive ICH and as control 12 subjects without brain haemorrhage. Biopsy of superficial temporal artery has been performed and β-amyloid deposit was quantified.ResultsAmong 25 subjects with ICH, 10 (40%) had APOE epsilon 2 allele and among these subjects 7 (70%) showed amyloid accumulation on temporal artery specimens, 8 (32%) subjects had APOE epsilon 3 allele and among these subjects only 2 (25%) showed amyloid accumulation on temporal artery specimens, whereas 7 (28%) had APOE epsilon 4 allele and of these, 7 (100%) showed amyloid accumulation on temporal artery specimens. At multivariable logistic regression analysis for the presence of amyloid, predictive factors for the presence of amyloid in temporal artery biopsies were: age, hypertension, intralobar site of haemorrhage, APOE epsilon 2 and APOE epsilon 4 alleles.DiscussionOur findings of a higher frequency of amyloid deposition in temporal artery specimens in subjects with spontaneous intracerebral haemorrhage indicate a possible role of temporal artery as a possible diagnostic site of biopsy in subjects at high risk to develop intracranial haemorrhage related to Cerebral Amyloid Angiopathy.

Temporal small arterial inflammation is common in patients with giant cell arteritis

Giant cell arteritis (GCA) primarily involves medium-to-large arteries. Small-vessel inflammation is a recognized phenomenon occurring in association with GCA. However, its significance is poorly elucidated. Histologic sections and medical records of105 temporal artery specimens were retrospectively reviewed between 2008 and 2017 to examine associated clinical manifestations and laboratory data including antinuclear antibody and p-antineutrophilic cytoplasmic antibody titers. Immunohistochemical staining for CD4 and CD8 was performed in select cases to assess the nature of the inflammatory response. Seventy-eight patients meeting the diagnostic criteria of temporal arteritis were included in the analysis. Twenty-eight specimens demonstrated temporal arteritis with small arterial inflammation (SAI), and 50 specimens showed temporal arteritis without SAI. Eight (28.6%) of 28 patients with SAI presented with jaw claudication, whereas 5 (17.9%) were febrile at presentation. In contrast, in 50 patients without SAI, jaw claudication and fever were seen in 11 and 2 cases, respectively (P = .01 and P = .0047, respectively). No statistically significant difference was noted between other symptoms and laboratory indices between the 2 groups. Elevated p-antineutrophilic cytoplasmic antibody titers in GCA may be associated with concomitant polymyalgia rheumatica or treatment-resistant disease. We also identified a higher count of CD4 and CD8 T cells in SAI cases, although the ratio of CD4/CD8 T lymphocytes was within normal limits. In conclusion, simultaneous involvement of arterioles and medium- to large-sized arteries is common in GCA and may be associated with treatment-refractory disease. Documentation of small arterial involvement in GCA will help the clinicians to manage the disease more effectively.

Comparative transcriptome analysis reveals involvement of TLR-2 signaling in the pathogenesis of intracranial aneurysm

In this study, we collected and analyzed 15 aneurysmal and 17 superficial temporal artery (STA) specimens from 32 Chinese patients with intracranial aneurysm. Total RNA was extracted and reverse transcribed to cDNA, and genome-wide expression profiling was performed by using the Affymetrix Human Genome U133 Plus 2.0 Array which allows a total number of 38,500 genes to be analyzed at the same time. Real-time RT-PCR was performed to verify the expression level of 8 selected genes. We found significant up-regulation of the TLR-2 gene. This result suggests that TLR-2 plays a key role in the formation of intracranial aneurysm in a Chinese population. To our knowledge, this study is the first to use the Human Genome U133 Plus 2.0 Array to analyze the gene expression profiles in Chinese patients with intracranial aneurysm.

Temporal artery biopsies; do they make the cut?

Background and AimsTemporal artery biopsy is the gold standard investigation for giant cell arteritis. Guidelines recommend that specimens should measure no less than 1 cm and ideally more than 2 cm in length, as this influences the likelihood of biopsy positivity. This audit investigates the extent to which temporal artery biopsies acquired in our hospital meet these guidelines.MethodsHistopathology reports for all temporal artery biopsies performed at University Hospital Ayr between January 2011 and June 2013 were examined.ResultsFifty-six temporal artery biopsy specimens showed a range in length from 0.5 cm to 3.1 cm, with a mean of 1.4 cm. Thirty-seven biopsies measured ≥1 cm (66%) and 13 were ≥2 cm (23%). Therefore, 19 samples (34%) did not meet the recommended standard. Just seven biopsies showed features of giant cell arteritis, with six of these measuring ≥1 cm in length (86%).ConclusionThe guidelines for temporal artery specimens are not being met at our centre. Furthermore, biopsies measuring ≥1...

Temporal artery biopsies: do they make the cut?

Temporal artery biopsy is the gold standard investigation for giant cell arteritis. Guidelines recommend that specimens should measure no less than 1 cm and ideally more than 2 cm in length, as this influences the likelihood of biopsy positivity. This audit investigates the extent to which temporal artery biopsies acquired in our hospital meet these guidelines. Histopathology reports for all temporal artery biopsies performed at University Hospital Ayr between January 2011 and June 2013 were examined. Fifty-six temporal artery biopsy specimens showed a range in length from 0.5 cm to 3.1 cm, with a mean of 1.4 cm. Thirty-seven biopsies measured ≥1 cm (66%) and 13 were ≥2 cm (23%). Therefore, 19 samples (34%) did not meet the recommended standard. Just seven biopsies showed features of giant cell arteritis, with six of these measuring ≥1 cm in length (86%). The guidelines for temporal artery specimens are not being met at our centre. Furthermore, biopsies measuring ≥1 cm are much more common in the small group of positive results. This validates the minimum recommended biopsy length and displays the importance of achieving this standard. We suggest changes to increase the number of biopsies meeting these guidelines, improving the accuracy of this invasive test.

Ephrin B2 and EphB4 selectively mark arterial and venous vessels in cerebral arteriovenous malformation

Ephrin type B receptor 4 (EphB4, Eph receptor) selectively binds ephrin B2 (Eph ligand). EphB4/ephrin B2 is involved in embryonic vessel development, vascular remodelling and pathological vessel formation in adults (including tumour angiogenesis). Binding of vascular endothelial growth factor (VEGF)-A to the endothelial-specific receptor VEGF receptor-2 is the main extracellular signal triggering angiogenic response. Little is known about the role of EphB4/ephrin B2 during angiogenesis and arteriovenous plasticity in cerebral arteriovenous malformation (cAVM). This study investigated EphB4 and ephrin B2 expression in cAVM. Haemorrhagic (H-AVM) and nonhaemorrhagic (NH-AVM) specimens of AVM nidus, obtained after microsurgical cAVM resection, and normal superficial temporal artery (STA) specimens, were analysed retrospectively. VEGF-A, EphB4 and ephrin B2 expression were studied by immunohistochemistry and immunoblotting. In cAVM (10 H-AVM; 10 NH-AVM), VEGF-A was immunocytochemically localized to endothelial cells; strong endothelial cell staining was found for EphB4 in veins and ephrin B2 in arteries. Normal STA (n = 10) did not express EphB4 or ephrin B2. EphB4 and ephrin B2 expression was greater in H-AVM than in NH-AVM. Endothelial cells are more active in H-AVM than NH-AVM. EphB4 and ephrin B2 play important roles in neovascularization and arteriovenous differentiation/plasticity. These data provide new insights into the aetiology of cAVM and lay a foundation for further study. The notch pathway induced by VEGF-A may be a key signalling pathway in this process.

A3.33 Increased rho-kinase activity in temporal artery biopsies from patients with giant cell arteritis

Background/PurposeROCKs are implicated in the pathogenesis of many vascular diseases. ROCK activation is associated with Th17 differentiation and production of Th17-associated cytokines, IL-17 and IL-21. Th17 cells and related cytokines...

Upregulation of Cyclooxygenase-2 (COX-2) and Microsomal Prostaglandin E 2 Synthase-1 (mPGES-1) in Wall of Ruptured Human Cerebral Aneurysms

Cyclooxygenase-2 (COX-2) and Microsomal Prostaglandin E2 Synthase-1 (mPGES-1) catalyze isomerization of the cyclooxygenase product PGH2 into PGE2. Deletion of COX-2/mPGES-1 suppresses carotid artery atherogenesis and angiotensin II-induced aortic aneurysms formation, and attenuates neointimal hyperplasia after vascular injury in mice. The upregulation of COX-2/mPGES-1 in the wall of ruptured human cerebral aneurysms is not known. Ten patients with intracranial aneurysms (5 ruptured and 5 nonruptured) underwent microsurgical clipping. During the procedure, a segment of the aneurysm dome was resected and immunostained with monoclonal antibodies for COX-1, COX-2, and mPGES-1. A segment of the superficial temporal artery was also removed and immunostained with monoclonal antibodies for COX-1, COX-2, and mPGES-1. All 10 aneurysm tissues stained positive for mPGES-1 monoclonal antibody. Expression of mPGES-1 was more abundant in ruptured aneurysm tissue than in nonruptured aneurysms, based on a semiquantitative grading. None of the superficial temporal artery specimens expressed mPGES-1. COX-2 was upregulated in the same distribution as was mPGES-1. COX-1 was present constitutively in all tissues. COX-2/mPGES-1 are expressed in the wall of human cerebral aneurysms and more abundantly so in ruptured aneurysms than in nonruptured. We speculate that the protective effect of aspirin against rupture of cerebral aneurysms may be mediated in part by inhibition of COX-2/mPGES-1.

MMP-12, a novel matrix metalloproteinase associated with giant cell arteritis

MMP-12, a novel matrix metalloproteinase associated with giant cell arteritis

PP22. GLUCOCORTICOIDS INHIBIT APOPTOSIS OF PERIPHERAL CD1C+ DENDRITIC CELLS AND CAUSE A DOWN-REGULATION OF THE CHEMOKINE LIGANDS CCL19 AND CCL21 IN GRANULOMATOUS INFILTRATES IN TEMPORAL ARTERIES FROM PATIENTS WITH GIANT CELL ARTERITIS

Background: Giant cell arteritis (GCA) is a systemic granulomatous vasculitis and characterized by a prompt response to glucocorticoid therapy. Earlier studies demonstrated that dendritic cells (DC) play a major role in the pathogenesis of GCA. Due to apoptosis glucocorticoid therapy leads to a rapid, time-dependent normalization of DC in temporal arteries from GCA patients. The aim of this study was to detemine glucocorticoid regulated genes in DC of GCA patients and whether glucocorticoid influences chemokines like CCL19 and CCL21 which promote DC migration from the blood stream into the granulomatous lesions. Methods: Affymetrix U95Av2 arrays were used to determine glucocorticoid regulated genes in CD1c+ peripheral blood DC from 10 GCA patients. Immunohistochemical staining was performed on 38 paraffin-embedded consecutive temporal artery specimens from 21 patients with GCA to quantify CCL19 and CCL21 positive cells in granulomatous infiltrates. Results: DNA microarray analysis of CD1c+ peripheral blood DC from glucocorticoid treated GCA patients indicated a down-regulation of caspases 1 and 3, the caspase like apoptosis regulatory protein (CLARP), BAX delta, FAS and FADD was seen. Bcl2 and the inhibitor of apoptosis protein (IAP1) were up-regulated. In temporal arteries from GCA patients glucocorticoid rapidly down-regulated CCL 19 and CCL21 in granulomatous infiltrates. After one day of glucocorticoid therapy 13% (n = 12) of all mononucleated cells in the graulomatous infiltrates express CCL19. The number of CCL19+ cells decreases from 8% after two days (n = 7) to 5% (n = 4) after 7 days of glucocorticoid therapy. A significant down-regulation of CCL19 was already found between day 1 and day 3 of glucocorticoid treatment (p = 0.0032). CCL21+ cells decreased in the same manner under glucocorticoid exposure. Conclusions: Glucocorticoids lead to an inhibition of CD1c+ DC apoptosis in the peripheral blood of GCA patients. Additionally, a time-dependent down-regulation of CCL19 and CCL21 in temporal arteries was found and this might account for an inhibition of DC imigration in temporal artery tissue in GCA.

Silent versus cranial giant cell arteritis. Initial presentation and outcome of 50 biopsy-proven cases

Background The objective of the present study was to compare the silent form of giant cell arteritis (GCA) to the classic cephalic form of the disease. Methods We conducted a retrospective study based on a chart review of 50 consecutive, biopsy-proven GCA, recorded at a department of internal medicine. We sought to distinguish a silent form, defined by a prolonged inflammatory syndrome or fever of unknown origin with the absence of cephalic signs, polymyalgia rheumatica, or large artery involvement, from an overt “classic” cranial temporal arteritis. Results The prevalence of the silent form of GCA was 46% in our study. Abnormal temporal arteries were more frequent in the cephalic group. The silent GCA group had higher C-reactive protein levels ( p < 0.05), a higher platelet count ( p < 0.05), and lower serum albumin ( p < 0.05). There was no significant difference in temporal artery specimens in the two groups. Clinical relapses tended to be more frequent, and patients free of corticosteroids tended to be less frequent, in the cephalic group, though the difference was not statistically significant. Conclusions The silent and cephalic forms of GCA could have distinct clinical and biological patterns and different outcomes. The limitation of our study was its retrospective design. Further studies are required to determine if this distinction is useful in treating GCA patients.

Arterial wall production of cytokines in giant cell arteritis: results of a pilot study using human temporal artery cultures.

Giant cell arteritis (GCA) is a subacute periarteritis predominantly affecting segments of the external carotids of elderly patients. Vasculitic lesions in GCA samples might be characterized by in situ production of cytokines mRNA, indicative of macrophage and T-cell activation. However, whether the cytokine production of vessels with arteritis differs from that of vessels exposed to inflammatory conditions that originate peripheral to the vessel remains unknown. We investigated cytokine and soluble receptor cytokine production in blood samples and cultures of human temporal arteries from 22 consecutive patients (mean age 77 +/- 6 years) further investigated for possible diagnosis of GCA: 7 patients had GCA and 15 had neither GCA nor vasculitis but had other inflammatory, infectious, or malignant diseases (controls). The production of cytokines and soluble cytokine receptors in the supernatants of cultures of 3-mm segments of temporal artery specimens, before and after lipopolysaccharide (LPS) stimulation (10 ng/ml and 10 microg/ml) and in serum, was quantified using sandwich enzyme-linked immunosorbent assay (ELISA). Cytokine production by temporal arteries increased significantly and in a dose-dependent manner (p <.01) after LPS stimulation in all patients studied, suggesting that the system is methodologically functional. Despite a large interindividual variation, we found similar differences in cytokine production before and after stimulation by 10 ng/ml and 10 microg/ml LPS between both groups: temporal arteries of GCA patients produced more interleukin (IL)-1beta (p <.05) and IFNgamma (nonsignificant) and less tumor necrosis factor (TNF)alpha (p <.05) and IL-6 (nonsignificant) than temporal arteries of controls. The levels of TNFalpha (p <.05) and IL-6 soluble receptor (p <.05) were significantly lower in GCA patients as compared with controls in blood samples, whereas levels of cytokines in temporal artery and in blood samples were not significantly correlated at the individual level in both groups. The present pilot study, which requires further confirmation on a larger number of well-defined patients with GCA, suggests that a specific arterial cytokine production profile might exist in GCA (high IL-1beta +/- IFNgamma and low TNFalpha), addresses the question of the mechanisms by which IL-1beta and TNFalpha might be differentially regulated at the level of the arterial cell wall, and supports the view that cultures of the temporal artery might be an interesting tool for evaluating the role of cytokines in GCA pathogenesis.

Detection of Chlamydia pneumoniae in giant cell vasculitis and correlation with the topographic arrangement of tissue-infiltrating dendritic cells.

Recent studies suggest that giant cell arteritis (GCA) may be an antigen-driven disease. Since Chlamydia pneumoniae has been identified in arterial vessel walls, it was hypothesized that this organism might be associated with GCA. Fourteen paraffin-embedded temporal artery biopsy specimens from 9 patients with GCA were examined by immunohistochemistry and by polymerase chain reaction (PCR) for the presence of C pneumoniae; for 5 patients, specimens were available from both the left and right arteries. Four temporal artery specimens from 3 patients with polymyalgia rheumatica (PMR) and 9 temporal artery specimens from 5 patients without GCA or PMR served as controls. C pneumoniae was detected by both immunohistochemistry and PCR in 6 GCA patient samples. One GCA patient sample was immunopositive only; another was PCR positive only. Thus, C pneumoniae was found in 8 of 9 GCA patients. One of 4 control samples from the PMR patients was immunopositive, but PCR negative, for C pneumoniae. The C pneumoniae-positive PMR patient also had respiratory symptoms. The remaining 9 control samples were negative for C pneumoniae by both immunohistochemistry and PCR. Immunohistochemistry showed that bacteria predominate in the adventitial layer of temporal arteries, in granulomatous infiltrates. Dendritic cells were examined by immunohistochemistry for their presence and localization in consecutive temporal artery specimens, and showed a strong topographic relationship with C pneumoniae. Like the bacterium, dendritic cells predominate in the adventitial layer of the arteries. C pneumoniae was found in temporal artery specimens from most GCA patients, in 1 specimen from a PMR patient, and in no other control specimens; thus, it may play a role in the pathogenesis of the disease. Dendritic cells may represent the antigen-presenting cells in this situation.

Tissue-destructive macrophages in giant cell arteritis.

Giant cell arteritis (GCA) is an inflammatory vasculopathy in which T cells and macrophages infiltrate the wall of medium and large arteries. Clinical consequences such as blindness and stroke are related to arterial occlusion. Formation of aortic aneurysms may result from necrosis of smooth muscle cells and fragmentation of elastic membranes. The molecular mechanisms of arterial wall injury in GCA are not understood. To identify mechanisms of arterial damage, gene expression in inflamed and unaffected temporal artery specimens was compared by differential display polymerase chain reaction. Genes differentially expressed in arterial lesions included 3 products encoded by the mitochondrial genome. Immunohistochemistry with antibodies specific for a 65-kDa mitochondrial antigen revealed that increased expression of mitochondrial products was characteristic of multinucleated giant cells and of CD68+ macrophages that cluster in the media and at the media-intima junction. 4-Hydroxy-2-nonenal adducts, products of lipid peroxidation, were detected on smooth muscle cells and on tissue infiltrating cells, in close proximity to multinucleated giant cells and CD68+ macrophages. Also, giant cells and macrophages with overexpression of mitochondrial products were able to synthesize metalloproteinase-2. Our data suggest that in the vascular lesions characteristic for GCA, a subset of macrophages has the potential to support several pathways of arterial injury, including the release of reactive oxygen species and the production of metalloproteinase-2. This macrophage subset is topographically defined and is also identified by overexpression of mitochondrial genes. Because these macrophages have a high potential to promote several mechanisms of arterial wall damage, they should be therapeutically targeted to prevent blood vessel destruction.

Giant Cell Vasculitis Is a T Cell-Dependent Disease

Giant cell arteritis (GCA) is a systemic vasculitis that preferentially targets medium-sized and large arteries. The etiopathogenesis of the syndrome is not known, and because of the paucity of information concerning the mechanisms of blood vessel wall damage, treatment options are limited. Clues to pathogenic events in this arteritis may derive from understanding the function of tissue-infiltrating cells. Arterial injury in GCA is associated with the formation of granulomas that are composed of T cells, activated macrophages, and multinucleated giant cells. To examine the role of T cells, we implanted inflamed temporal arteries from patients with GCA into severe combined immunodeficiency (SCID) mice and studied whether the vascular lesions were T cell-dependent. Temporal artery specimens from patients with GCA were engrafted into SCID mice. The histomorphologic appearance of fresh arteries and grafts retrieved from the mice was compared by two-color immunohistochemistry, and the functional profile of tissue-infiltrating cells was analyzed by semiquantifying cytokine transcription with a polymerase chain reaction (PCR)-based assay system. The repertoire of tissue-infiltrating T cells was assessed for the presence of dominant T cell populations by using T cell receptor beta-chain-specific PCR followed by sequencing. To investigate the role of T cells in the activation of tissue-infiltrating macrophages, T cells were depleted from the arterial grafts by treating the mice with T cell-specific antibodies and the production of monokines was monitored. To demonstrate the disease relevance of T cells expanding in the implants, T cells were isolated from tissue segments and adoptively transferred into mice implanted with syngeneic arteries. The in situ production of lymphokines was then determined. The inflammatory infiltrate penetrating all layers of the arterial wall persisted in the xenotransplants, indicating that the inflammatory foci represent independent functional units. Similar quantities of T cell- and macrophage-derived cytokines were detected in fresh and engrafted tissue. However, the diversity of tissue-infiltrating T cells decreased following implantation. T cells with identical T cell receptors were expanded in different mice that had been engrafted with tissue fragments from the same patient, indicating that T cell survival in the arterial wall was a nonrandom process. To confirm the disease relevance of these T cells, T cell depletion and reconstitution experiments were performed. Antibody-mediated elimination of T cells from the xenotransplants resulted in the attenuation of the production of the monokines, IL-1 beta and IL-6. Adoptive transfer of syngeneic tissue-derived T cells, but not of peripheral blood T cells, into engrafted SCID mice enhanced the transcription of IL-2 and IFN-gamma in the implanted arteries. The vascular lesions of GCA are maintained in human artery-mouse chimeras, indicating that all cellular and noncellular components necessary for the disease are present in the temporal artery. Activation of tissue-infiltrating T cells and macrophages depends upon an infrequent subpopulation of lesional T cells that have a survival advantage in the xenotransplants. The selective proliferation of these T cells in the arteries suggests that there is recognition of a locally expressed antigen. Therefore, these T cells should be candidate targets for the development of novel therapeutic strategies in GCA.