Magnetically labeled secretin retains receptor affinity to pancreas acinar cells

To clarify the mechanisms of restenosis, restenotic human tissue specimens obtained by directional coronary atherectomy (DCA) in 43 patients were immunohistochemically analysed for cell proliferation and deposition of PG-M/versican, an important extracellular matrix proteoglycan of the vessel wall. The patients were classified into five groups according to the period after percutaneous transluminal coronary angioplasty (PTCA): 0-1 month (N = 6), 1-3 months (N = 12), 3-6 months (N = 11), more than 6 months (N = 6) and de novo lesions (N = 8). The tissue specimens were of 35 restenotic lesions following PTCA and eight primary stenotic lesions with no prior PTCA. Total cell numbers in the atherectomy specimens increased significantly up to 3 months after PTCA. Most cells were alpha-smooth muscle actin (alpha-SMA)-positive. To evaluate cell proliferation, the specimens were immunostained for Ki-67 antigen (clone MIB-1). A significant increase in the positive ratio was observed up to 1 month after PTCA, although the labelling index was less than 1 per cent at every stage. The deposition of PG-M/versican, as analysed by immunohistochemistry, was greatest during the period 1-3 months after primary angioplasty, when restenosis detected by angiography progresses most actively. These results suggest that the peak of cell proliferation in the neointima occurs earlier than angiographic restenosis and that the deposition of PG-M/versican may be a major factor in restenosis following angioplasty.     

Proliferative activity in peripheral and coronary atherosclerotic plaque among patients undergoing percutaneous revascularization

We evaluated the proliferative activity of human atherosclerotic lesions associated with active symptoms of ischemia, by assessing the expression of the proliferating cell nuclear antigen (PCNA). We confirmed in vitro that PCNA, an essential component of the DNA synthesis machinery, is selectively expressed in proliferating human vascular smooth muscle cells. 37 atherosclerotic lesions (18 primary and 19 restenotic) retrieved by directional atherectomy from either coronary or peripheral arteries were then studied for the expression of PCNA, using in situ hybridization or immunohistochemistry. Among plaques studied by in situ hybridization, 7 out of 11 primary and 11 out of 11 restenotic lesions contained PCNA-positive cells. The mean rate of proliferation (percent of PCNA-positive cells) was 7.2 +/- 10.8% in primary lesions and 20.6 +/- 18.2% in restenotic lesions (P < 0.05). Among specimens studied by immunohistochemistry, five out of seven primary and eight out of eight restenotic lesions contained proliferating cells. The mean rate of proliferation was again higher in the restenotic (15.2 +/- 13.6%) than primary (3.6 +/- 3.5%) lesions (P < 0.05). Proliferating cells were detected as late as 1 yr after angioplasty. We conclude that cellular proliferation is a feature of atherosclerotic lesions which are associated with symptoms of ischemia, but that it is more prominent in restenosis compared to primary lesions. These findings have implications for therapies aimed at limiting lesion growth, particularly after percutaneous revascularization.     

Binding of the NG2 proteoglycan to type VI collagen and other extracellular matrix molecules

Previous studies have suggested that the NG2 proteoglycan interacts with type VI collagen. We have further characterized this interaction using a solid phase binding assay in which purified NG2 was shown to bind to pepsin-solubilized type VI collagen. In addition, NG2 bound a recombinant alpha2 (VI) collagen chain but did not appreciably bind to the recombinant alpha1 (VI) chain or the N-terminal domain of alpha3 (VI) (N9-N2). Binding of NG2 to type VI collagen was shown to be concentration-dependent and saturable and to depend mainly on the NG2 core protein, since chondroitinase-treated NG2 bound the collagen as well as undigested samples. In addition, the binding studies revealed several other possible ligands for NG2, including type II collagen, type V collagen, tenascin, and laminin. Binding of the proteoglycan to these molecules was also shown to be mediated by domains contained within the NG2 core protein. The ability of NG2 to bind to these extracellular matrix molecules was compared with that of the chondroitin sulfate proteoglycan decorin, revealing an almost identical binding pattern of the two proteoglycans to the different collagen types. In addition, decorin was found to effectively inhibit the ability of NG2 to bind to collagen, thus suggesting that the two proteoglycans may bind to some of the same regions on the collagen substrates. In contrast, decorin did not bind tenascin and was ineffective in inhibiting the binding of NG2 to tenascin or laminin, indicating that NG2 may bind these two molecules using a separate domain that is distinct from its collagen binding region.     

Molecular anatomy of the perivascular sheath in human placental stem villi: the contractile apparatus and its association to the extracellular matrix

In previous studies, we have shown that smooth muscle cells and myofibroblast subpopulations of the perivascular stem villous sheath of the human placenta contain focal adhesion plaques and talin immunoreactivity. The close association of these cells to elastic and collagen fibres have led to the assumption of a functional myofibroelastic unit within the perivascular stem villous sheath. Interactions between the extracellular matrix and smooth muscle cells depend on a variety of structural protein assemblies. In the present study, we examined, by immunocytochemistry, whether the molecular assembly of extracellular matrix proteins and molecules of focal adhesions, known to be essential for signal transduction in smooth muscle cells, are also found in smooth muscle cells of the perivascular stem villous sheath of the human placenta. Vascular and extravascular smooth muscle cells were immunoreactive for alpha-actinin, vinculin, paxillin and tensin, the integrin chains alpha1 and beta1, and the basement membrane components laminin and heparan/-chondroitin sulfate proteoglycan perlecan. pp125(FAK) did not react. In the extracellular matrix of blood vessel walls and the perivascular stem villous sheath, we found immunoreactivity of fibronectin and collagen types I, VI and undulin (collagen type XIV). From our data we conclude that within the perivascular stem villous sheath, there exists a system of signal transduction molecules, indicating a cross talk between the smooth muscle cells of this sheath and their surrounding extracellular matrix.     

Isolation and characterization of chondroitin sulfate proteoglycans from embryonic quail that influence neural crest cell behavior

The movement of neural crest cells is controlled in part by extracellular matrix. Aggrecan, the chondroitin sulfate proteoglycan from adult cartilage, curtails the ability of neural crest cells to adhere, spread, and move across otherwise favorable matrix substrates in vitro. Our aim was to isolate, characterize, and compare the structure and effect on neural crest cells of aggrecan and proteoglycans purified from the tissues through which neural crest cells migrate. We metabolically radiolabeled proteoglycans in E2.5 quail embryos and isolated and characterized proteoglycans from E3.3 quail trunk and limb bud. The major labeled proteoglycan was highly negatively charged, similar in hydrodynamic size to chick limb bud versican/PG-M, smaller than adult cartilage aggrecan but larger than reported for embryonic sternal cartilage aggrecan. The molecular weight of the iodinated core protein was about 400 kDa, which is more than reported for aggrecan but less than that of chick versican/PG-M. The proteoglycan bore chondroitin sulfate glycosaminoglycan chains of 45 kDa, which is larger than those of aggrecan. It lacked dermatan sulfate, heparan sulfate, or keratan sulfate chains. It bound to collagen type I, like aggrecan, but not to fibronectin (unlike versican/PG-M), collagen type IV, or laminin-1 in solid-phase assays and it bound to hyaluronate in gel-shift assays. When added at concentrations between 10 and 30 microg/ml to substrates of fibronectin, trunk proteoglycan inhibited neural crest cell spreading and migration. Attenuation of cell spreading was shown to be the most sensitive and titratable measure of the effect on neural crest cells. This effect was sensitive to digestion with chondroitinase ABC. Similar cell behavior was also produced by aggrecan and the small dermatan sulfate proteoglycan decorin; however, 30-fold more aggrecan was required to produce an effect of similar magnitude. When added in solution to neural crest cells which were already spread and migrating on fibronectin, the embryonic proteoglycan rapidly and reversibly caused complete rounding of the cells, being at least 30-fold more potent than aggrecan in this activity.     

Biglycan, decorin, and versican protein expression patterns in coronary arteriopathy of human cardiac allograft: distinctness as compared to native atherosclerosis

BACKGROUND: Histochemical staining has demonstrated previously dramatic deposits of glycosaminoglycans associated with prominent lipid accumulations in thickened vessel walls of allograft coronary arteries. In this study, we characterized the amount, distribution, and types of proteoglycan in the walls of coronary arteries from human cardiac allografts and from native atherosclerotic (NA) controls as part of a strategy to understand the pathogenesis of transplant arteriopathy (TA). METHOD: We used polyclonal rabbit antibodies against human biglycan, decorin, and versican localize the proteoglycan molecules in standardized transverse sections of the proximal left anterior descending and right coronary arteries. Slides were scored in a blinded fashion for intensity of proteoglycan staining (0 to 6+) and for localization in the vessel walls. RESULTS: Unique patterns of proteoglycan distribution were present in TA and NA. Biglycan was particularly prominent in intima and evolving atheromata in severely diseased TA coronary arteries, but not in NA. Decorin was present mainly in adventitia of all vessels and in the intima of NA. Prominent versican accumulation occurred in intima and media of TA coronaries, associated with smooth muscle cells and foam cells. There was a reciprocal pattern of biglycan and decorin staining. Versican colocalized with biglycan. Intimal biglycan and versican deposits were positively correlated to the extent of luminal narrowing in TA. CONCLUSION: The distinctive staining patterns for biglycan, decorin and versican in both native and allograft disease indicate that the synthesis and distribution of these proteoglycans are regulated by different local mechanisms in different atheromatous diseases.     

Neointimal tissue response at sites of coronary stenting in humans: macroscopic, histological, and immunohistochemical analyses

BACKGROUND: Experimental animal studies have shown that coronary stenting induces neointimal proliferation. However, the histopathological events after coronary stenting in humans have not been studied systematically. METHODS AND RESULTS: We investigated 11 stented coronary arteries (9 Palmaz-Schatz stents, 1 Wiktor stent, and 1 ACS Multi-Link stent) obtained from 11 patients who had died 2 days to 21 months after stenting. We focused on gross, histological, and immunohistochemical aspects of the repair processes. Two patients developed symptoms of restenosis. Serial sections were stained with antibodies against smooth muscle cells (SMCs), macrophages, and endothelial cells. At 9 and 12 days after stenting, the stent sites showed thrombus formation with early formation of neointima composed of abundant macrophages and alpha-actin-negative spindle cells. From 64 days on, all sites with stenting showed a distinct layer of neointima, albeit to varying degrees. In nonrestenotic lesions, neointimal thickening was markedly less than in restenotic lesions but without qualitative differences; the neointima contained macrophages but was composed predominantly of alpha-actin-positive SMCs. CONCLUSIONS: These observations strongly support the concept that neointimal proliferation in humans is a process of staged redifferentiation of SMCs, which may cause in-stent stenosis. Moreover, the exuberant neointimal proliferation with accumulation of macrophages and extensive neovascularization at sites of stent restenosis suggests a role for organization of mural thrombus.     

Evidence that implicates the parathyroid hormone-related peptide in vascular stenosis. Increased gene expression in the intima of injured carotid arteries and human restenotic coronary lesions

Proliferation of vascular smooth muscle cells (VSMCs) is considered to be one key event underlying the pathophysiology of restenosis after angioplasty. The parathyroid hormone-related peptide (PTHrP) and its receptor, a local autocrine and paracrine regulator of cellular growth in a variety of normal cell types, have been reported in the vicinity of VSMCs. To investigate how PTHrP might be involved in the process of neointimal formation after balloon angioplasty, we examined PTHrP expression in balloon-denuded rat carotid arteries and human coronary arteries that had been retrieved by directional atherectomy. In rat carotid arteries, the RNase protection assay and in situ hybridization demonstrated that PTHrP mRNA expression increased fourfold to sixfold 1 to 7 days after denudation and continued for 28 days, coincident with downregulation of PTH/PTHrP receptor mRNA expression. In situ hybridization and immunohistochemistry revealed that PTHrP expression in balloon-denuded carotid arteries was mainly localized to the neointima. To confirm the involvement of the PTHrP in human coronary artery restenotic lesions, immunohistochemical analysis of human coronary atherectomy specimens (23 primary and 10 restenotic lesions) was then performed. The number of intimal cells that expressed PTHrP protein was significantly higher in restenotic (407 +/- 53 cells/mm2; range, 143 to 739) than in stable angina (50 +/- 12 cells/mm2; range, 18 to 132; P<.05) or unstable angina (129 +/- 16 cells/mm2; range, 21 to 232; P<.05) specimens. These data demonstrate that PTHrP gene expression in VSMCs markedly increases during neointimal formation, supporting the hypothesis that PTHrP may play an important role in vascular stenosis as a regulator of VSMC proliferation.     

Neonatal estrogen stimulates proliferation of periductal fibroblasts and alters the extracellular matrix composition in the rat prostate

The purpose of this study was to examine whether changes in extracellular matrix (ECM) molecules are associated with the growth inhibition and differentiation defects of the prostate gland following neonatal exposure to estradiol. Using immunocytochemistry (ICC), laminin and collagen IV were localized to the basement membrane (BM) as well to the basal lamina of the periductal smooth muscle of the control developing prostates. In contrast, fibronectin and collagen III were localized throughout the stromal ECM. Exposure to neonatal estrogen altered the staining profile for specific ECM molecules. In the estrogenized rats, a thick layer of cells negative for laminin and collagen IV was observed adjacent to the BM. Electron microscopy and ICC for alpha-actin, fibronectin, and vimentin identified this multicellular layer of periductal cells as differentiated fibroblasts. Peripheral to these fibroblasts, actin-positive smooth muscle formed a second layer of periductal stromal cells. PCNA labeling showed that estrogen exposure increased the fibroblast proliferation. Because many periductal fibroblasts were positive for estrogen receptor alpha (ER alpha) in estrogenized rats, a direct effect of estradiol on their proliferation is suggested. Gelatinolytic gels revealed that estrogen exposure did not alter the activity of matrix metalloproteinases associated with tissue remodeling during prostate morphogenesis. However, the periductal fibroblast layer in estrogenized prostates was devoid of urokinase- and tissue-plasminogen activator, which may potentially alter the localized proteolysis involved in matrix remodeling. It is proposed that proliferation of a multicellular layer of periductal fibroblasts in estrogenized prostates results in a physical barrier that constrains branching morphogenesis and blocks paracrine communications between smooth muscle and epithelial cells which normally regulate differentiation.     

Expression of collagen, interstitial collagenase, and tissue inhibitor of metalloproteinases-1 in restenosis after carotid endarterectomy

Extracellular matrix is the principal component of the fibrous caps of atherosclerotic plaques and intimal hyperplastic lesions of reconstructed arteries. Interstitial collagen form an important part of the matrix, and the balance between collagen synthesis and degradation by interstitial collagenase (matrix metalloproteinase-1, MMP-1) may determine whether plaques rupture or vessels develop stenosis. We examined type I procollagen gene expression in human atherosclerotic and restenotic carotid arteries using in situ messenger RNA (mRNA) hybridization and the expression of MMP-1 and its endogenous inhibitor (tissue inhibitor of metalloproteinases-1, TIMP-1) by immunohistochemistry. Compared with normal arteries, atherosclerotic plaques bed increased expression of immunoreactive MMP-1 and TIMP-1 with modest increase of type 1 procollagen mRNA. Early restenotic lesions (< 1.5 years) contained abundant type I procollagen mRNA but little immunoreactive MMP-1 and TIMP-1. Late restenotic lesions (> 4 years) resembled atheroma and exhibited increased immunoreactive MMP-1 and TIMP-1 as well as abundant type I procollagen mRNA. Compared with atherosclerotic plaques, type I procollagen is increased and MMP-1 is decreased in early restenotic lesions. MMP-1 and TIMP-1 expressions are upregulated in lesions with a clear atheroma. These findings suggest that the balance between proteolysis and matrix synthesis may influence both the stability of atheromatous plaques and the development of restenotic lesions.     

Apoptosis in restenosis versus stable-angina atherosclerosis: implications for the pathogenesis of restenosis

Decreases in programmed cell death (apoptosis) may contribute to restenotic hyperplasia by prolonging the life span of intimal cells. Apoptotic events were compared in restenotic versus primary lesions, by using atherectomy samples from 16 restenotic and 30 primary human peripheral and coronary lesions from patients presenting with stable angina. We used transmission electron microscopy to identify apoptosis, quantify its frequency, distinguish apoptosis from necrosis, and relate these events to cellular composition. Smooth muscle cell (SMC) density was higher in restenotic versus primary lesions (P<0.0001), whereas the number of macrophages was significantly reduced (P<0.01) and the number of lymphocytes was lower, but not significantly (P=0.06). As the main finding, restenotic lesions contained fewer apoptotic cells compared with primary lesions (3% versus 13%, P=0.002), whereas no differences were found for cellular necrosis. With regard to cell type, the lower frequency of apoptotic cells observed in restenotic tissue was attributable to both SMCs and macrophages. The key finding of less apoptosis in restenotic versus primary lesions was in agreement with terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) analysis (2% versus 9%, P<0.001). For all lesions analyzed, significant inverse correlations were observed between the density of SMCs and the frequency of apoptotic cell death (r=-0.60, P<0.001) as well as the density of SMCs and that of macrophages (r=-0.74, P<0.001). No relationship was seen between the frequency of apoptosis and the density of macrophages. In conclusion, the data of the present study indicate that a low level of apoptosis may be an important mechanism leading to restenotic intimal lesion development after interventional procedures.     

Early morning dystonia in Parkinson''s disease

Proliferation of arterial smooth muscle cells has held center stage as the culprit in restenosis for almost two decades. Many strategies for combating restenosis target smooth muscle replication. However, none have proven beneficial in clinical trials. Indeed, inhibition of smooth muscle proliferation in human patients might produce the undesired effect of destabilizing vulnerable atherosclerotic plaques because these cells furnish the collagen responsible for the biomechanical strength of the plaque. Actually, in some cases the benefit of angioplasty may depend on stimulating smooth muscle replication and collagen elaboration, converting an "unstable" to a more stable plaque. Moreover, recent clinical and experimental evidence suggests that restenosis depends less on neointimal hyperplasia than on constrictive remodeling (i.e., advential scarring, producing a smaller lumen), a process independent of smooth muscle replication. The recognition that plaques vulnerable to disruption often do not produce flow-limiting stenoses highlights a need for reassessment of the strategies to treat or prevent the acute coronary syndromes. We should strive to treat aggressively risk factors such as hyperlipidemia whose control appears to stabilize plaques. Trials are even underway comparing such risk factor management with coronary artery intervention. If we could identify potentially unstable atheroma before they are evident, clinically, we might even contemplate angioplasty of nonsignificant stenoses to induce smooth muscle cell proliferation and reinforce the plaque's fibrous cap. This proposal may seem preposterous, yet we perform "primary" angioplasty every day in patients with an acute myocardial infarction whose "culprit" lesions underlying the thrombus are often not critical. Our knowledge of the biology of restenosis has lagged behind our practice of coronary intervention. Advances in understanding the biology of the complications of interventional therapy, hand in hand with technical advances, should help us to devise more rational and enduring approaches to benefiting our patients.     

Role of insulin-like growth factor binding proteins in the control of IGF actions

The insulin-like growth factor binding proteins have been shown to modify IGF actions. IGFBP-5 binds to extracellular matrix (ECM) and its ability to potentiate IGF activity is dependent upon the amount that is ECM associated. To determine the specific regions of IGFBP-5 that are required for ECM association, site directed mutagenesis has been used to prepare several forms of IGFBP-5. Mutants that have had the amino acids between positions 201 and 218 altered have been useful. Mutation of the lysine 211 resulted in no change in the affinity of IGFBP-5 for ECM or heparin Sepharose; however, it resulted in a major reduction in affinity for IGF-I following heparin binding. Other mutations which disrupted heparin binding also resulted in loss of this affinity shift. Most distruptive were mutations of amino acids 211, 214, 217 and 218 and 202, 206 and 207. Mutation of residues 201 plus 202 had some effect, but substitution for 207, 211, 217 and 218 had no effect. When binding to intact ECM was analyzed, similar results were obtained. This suggests that amino acids 202, 206 and 214 are definitely involved in heparin and ECM binding. When binding to proteoglycans such as tenascin and heparin sulfate proteoglycan was analyzed, similar results were obtained. IGFBP-5 also binds to other proteins in ECM, including type IV collagen and plasminogen activator inhibitor-I. Specific antisera for plasminogen activator inhibitor-1 can coprecipitate IGFBP-5. IGFBPs are degraded by specific proteases. Three proteases that degrade IGFBP-2, -4 and -5 have been characterized. They are serine proteases that cleave these proteins at basic residues. Although several well characterized serine proteases cleave IGFBP-4 or -5, the proteases in cell conditioned media appear to be distinct.     

Detection of nptII (kanamycin resistance) genes in genomes of transgenic plants by marker-rescue transformation

The microfibrillar proteins fibulin-1 and fibulin-2 were previously identified as prominent components of the endocardial cushion tissue (ECT) during heart development and shown to persist in adult valves and septa. Immunogold staining has now been used to compare their localization in embryonic (days 9-11) and adult mouse heart with that of fibronectin and the chondroitin sulphate proteoglycan versican. All four proteins were deposited in the ECT, which consists of a hyaluronan-rich, mainly unstructured matrix, but were barely detectable in myocardial basement membranes or within endocardial cells. Digestion with hyaluronate lyase selectively released the fibulins and versican but not fibronectin from the ECT. Yet neither of the two fibulins bound to hyaluronan in solid-phase assays, in contrast to versican. In the adult heart valve, all four proteins could be detected close to cross-striated collagen fibrils or microfibrils, but only versican was lost upon exposure to hyaluronate lyase. The data indicate that fibulins are associated with the hyaluronan-matrix of ECT through a bridge of versican, but that this association changes upon valve development to another supramolecular, presumably microfibrillar organization based on fibronectin and/or fibrillins.     

Heparan sulfate proteoglycans as adhesive and anti-invasive molecules. Syndecans and glypican have distinct functions

ARH-77 cells do not adhere to type I collagen and readily invade into collagen gels, but following expression of the transmembrane heparan sulfate proteoglycan syndecan-1, they bind collagen and fail to invade. We now show that cells transfected with syndecan-2 or syndecan-4 also bind collagen and are non-invasive. In contrast, cells transfected with the glycosylphosphatidylinositol-anchored proteoglycan glypican-1 do not bind to collagen and remain invasive, even though glypican- and syndecan-expressing cells have similar surface levels of heparan sulfate, and their proteoglycans have similar affinities for collagen. Analysis of cells expressing syndecan-1-glypican-1 chimeric proteoglycans reveals that inhibition of invasion requires the extracellular domain of syndecan but not its transmembrane or cytoplasmic domain. Surprisingly, cells bearing a chimera composed of the glypican extracellular domain fused to the syndecan transmembrane and cytoplasmic domains bind to collagen but remain invasive, implying that adhesion to collagen is not by itself sufficient to inhibit invasion. Apparently, the extracellular domain of syndecan-1, presumably by interacting with cell-surface signal transducing molecules, directly regulates complex cell behaviors such as motility and invasiveness. These results also show for the first time that syndecans and glypicans can have distinct functions, even when expressed by the same cell type.     

Binding of human phospholipase A2 type II to proteoglycans. Differential effect of glycosaminoglycans on enzyme activity

Phospholipase A2 acting on low density lipoproteins in the extracellular arterial intima may form proinflammatory lipid mediators. Human nonpancreatic secretory phospholipase A2 has three regions that may associate with sulfated glycosaminoglycans. The apoB-100 molecule in low density lipoproteins also has glycosaminoglycan binding regions that could mediate its retention in the arterial intima. Here we report that human nonpancreatic phospholipase A2 isolated from a transfected cell line binds to glycosaminoglycans secreted by cultured human arterial smooth muscle cells. A gel mobility shift assay showed that the affinity of phospholipase A2 for glycosaminoglycans from a heparan sulfate/chondroitin sulfate proteoglycan was higher than for chondroitin sulfate glycosaminoglycans from a larger versican-like proteoglycan. Affinity chromatography confirmed these results. All glycosaminoglycans tested, at concentrations up to 100 microM, increased the activity of phospholipase A2 toward phosphatidylcholine liposomes. Above this concentration, heparan sulfate and heparin inhibited the enzyme. Heparin and chondroitin 6-sulfate increased phospholipase A2 activity on low density lipoproteins up to 4-fold at 100 microM, whereas heparan sulfate had no effect. The results indicate that human nonpancreatic secretory phospholipase A2 interacts with proteoglycans via their glycosaminoglycan moiety and that the enzyme activity may be modulated by the association of the enzyme and its substrate to the sulfated polysaccharides.     

Upregulation of IGF-I and collagen I mRNA in human atherosclerotic tissue is not accompanied by changes in type 1 IGF receptor or collagen III mRNA: an in situ hybridization study

BACKGROUND: Immunoreactive insulin-like growth factor-I (IGF-I) has recently been localized to vascular smooth muscle cells in coronary atherectomy plaques, but it remains unclear whether these cells are the source of this growth factor. We therefore investigated the gene expression of this factor, and the expression of the genes for its receptor and two types of collagen known to be regulated by IGF-I, in vascular tissue samples from patients with atherosclerosis or restenosis. METHODS: Gene expression and localization were investigated by in situ hybridization, using 35S-labelled complementary RNA probes specific for IGF-I, its type a receptor, collagen I, and collagen III. The cellular composition of the tissue samples was determined by immunohistochemistry using antibodies specific for smooth muscle cells and macrophages. RESULTS: IGF-I and collagen I messenger RNAs were found in areas containing smooth muscle cells and macrophages, but collagen III and type 1 IGF receptor gene expression could not be detected in any tissue samples. CONCLUSION: IGF-I appears to be involved in the progression of the atherosclerotic plaque, even at an advanced stage, but preliminary data from two restenotic plaques indicate that it may not be involved in the later stages of restenosis.     

A premenopausal woman presenting with acute myocardial infarction of three different coronary vessels within 1 year: role of lipoprotein(a)

A premenopausal female patient presented with acute myocardial infarction of 3 different coronary vessels at different times within 1 year. These events were caused not by restenotic lesions after balloon angioplasty but by new lesions, which were successfully treated by primary angioplasty. Although she had a history of hypertension, type IIB hyperlipidemia, and diabetes, they had been well-controlled on medication. An elevated serum lipoprotein(a) level may have played a role in this rapid angiographic progression.     

Coronary artery restenosis after balloon angioplasty in humans is associated with circumferential coronary constriction

Therapies that inhibit intimal hyperplasia do not prevent restenosis after coronary artery balloon angioplasty, suggesting that additional mechanisms may be responsible for restenosis in humans. Using an intravascular ultrasound (Hewlett-Packard Sonos Intravascular Imaging System). 3.5F, 30-MHz (Boston Scientific) monorail imaging catheter, we studied 17 patients with clinical and angiographic restenosis at an average (mean +/- SD) of 7 +/- 6 months after balloon angioplasty (13 men age, 71 +/- 10 years; 12 left anterior descending coronary arteries, 4 right coronary arteries, and 1 left circumflex coronary artery) The lumen area (L.A), vessel wall area (VWA), and total cross-sectional area (CSA) within the external elastic lamina were measured at the restenosis site and at proximal and distal reference sites, which were defined as adjacent segments with the least amount of plaque. Consistent with coronary angiography findings, decreased LA at the restenotic site was detected in all 17 patients. The unique finding was that total CSA at the restenotic site was significantly decreased compared with both proximal and distal reference sites (10.1 +/- 2.4 versus 14.8 +/- 3.2 mm2 and 10.1 +/- 2.4 versus 13.8 +/- 3.1 mm2, respectively, P < .001), whereas VWA (intima plus media) was slightly increased at the angioplasty site compared with both proximal and distal reference sites (8.0 +/- 2.3 versus 7.6 +/- 2.3 mm2 and 8.0 +/- 2.3 versus 6.7 +/- 2.3 mm2, respectively, P = NS). Eighty-three percent of the loss in LA at the restenotic site was due to constriction of the total CSA, while the increase in VWA at the restenotic site accounted for only a 17% loss in LA. We then compared these results with the morphology of coronary artery segments in 14 patients without restenosis. These coronary artery segments had been previously treated with balloon angioplasty (7 +/- 5 months). Unlike that in restenotic lesions, the total CSA within the external elastic lamina at the sites of previous angioplasty was similar to that in distal and proximal reference sites (P = NS). Significant and consistent reduction in arterial CSA, with a minor increase in VWA, characterizes human coronary lesions that cause angiographic restenosis. These data suggest that in humans, "recoil" and/or vascular contraction with healing in response to balloon injury is a major contributor to restenosis after balloon angioplasty.