Determination of the layer-specific distributed collagen fibre orientations in human thoracic and abdominal aortas and common iliac arteries.

The established method of polarized microscopy in combination with a universal stage is used to determine the layer-specific distributed collagen fibre orientations in 11 human non-atherosclerotic thoracic and abdominal aortas and common iliac arteries (63 ± 15.3 years, mean ± s.d.). A dispersion model is used to quantify over 37 000 recorded fibre angles from tissue samples. The study resulted in distinct fibre families, fibre directions, dispersion and thickness data for each layer and all vessels investigated. Two fibre families were present for the intima, media and adventitia in the aortas, with often a third and sometimes a fourth family in the intima in the respective axial and circumferential directions. In all aortas, the two families were almost symmetrically arranged with respect to the cylinder axis, closer to the axial direction in the adventitia, closer to the circumferential direction in the media and in between in the intima. The same trend was found for the intima and adventitia of the common iliac arteries; however, there was only one preferred fibre alignment present in the media. In all locations and layers, the observed fibre orientations were always in the tangential plane of the walls, with no radial components and very small dispersion through the wall thickness. A wider range of in-plane fibre orientations was present in the intima than in the media and adventitia. The mean total wall thickness for the aortas and the common iliac artery was 1.39 and 1.05 mm, respectively. For the aortas, a slight thickening of the intima and a thinning of the media in increasingly distal regions were observed. A clear intimal thickening was present distal to the branching of the celiac arteries. All data, except for the media of the common iliac arteries, showed two prominent collagen fibre families for all layers so that two-fibre family models seem most appropriate.

Perivascular adipose tissue modulates vascular function in the human internal thoracic artery.

OBJECTIVE: Recent studies have shown that perivascular adipose tissue from the rat aorta secretes a substance that can dilate the aorta. The purpose of the present study was to examine whether this vasodilator is also present in human internal thoracic arteries. METHODS: Vascular function of human internal thoracic arteries with and without perivascular adipose tissue was assessed with wire myography, and morphology was examined with light microscopy. RESULTS: The presence of perivascular adipose tissue attenuated the maximal contraction to U 46619 and the contraction to phenylephrine (1 micromol/L) by 37% and 24%, respectively. Transfer of the solution incubated with a perivascular adipose tissue-intact vessel (donor) to a vessel without perivascular adipose tissue (recipient) induced a significant relaxation (36%) in the recipient artery precontracted with phenylephrine. Transfer of incubation solution with perivascular adipose tissue alone also induced a relaxation response in the recipient vessel (37%). The relaxation of the recipient artery induced by the transfer of incubation solution from the donor (artery with intact perivascular adipose tissue or perivascular adipose tissue alone) was absent in vessels precontracted by KCl (60 mmol/L) and was prevented by calcium-dependent potassium channel blockers (tetraethylammonium chloride, 1 mmol/L; iberiotoxin, 100 nmol/L), but not by the voltage-dependent potassium channel blocker 4-aminopyridine (1 mmol/L) and the adenosine triphosphate-dependent potassium channel blocker glibenclamide (10 micromol/L). CONCLUSIONS: Perivascular adipose tissue in human internal thoracic arteries releases a transferable relaxation factor that acts through the activation of calcium-dependent potassium channels. Because perivascular adipose tissue is often removed in coronary artery bypass grafting, retaining perivascular adipose tissue might be helpful in reducing the occurrence of vasospasm of the graft vessels.

Comparison of deposits of versican, biglycan and decorin in saphenous vein and internal thoracic, radial and coronary arteries: correlation to patency.

BACKGROUND: Matrix proteoglycans versican, biglycan and decorin are important determinants of vessel-wall structure and pathology. Thickened myxoid intimas typical of restenosis and early atherosclerosis are enriched in versican and biglycan, proteoglycans that promote proliferation and migration of smooth muscle cells and bind lipoproteins. In contrast, compact fibrous intimas are characterized by decorin. OBJECTIVE: To compare the distribution patterns of these matrix proteoglycans, and changes induced by organ culture in coronary artery, saphenous vein, internal thoracic artery (ITA), and radial artery, and correlate differences to patency. METHODS: Vessels were collected at the time of bypass surgery and heart transplantation and either fixed for immunohistochemistry or prepared for organ culture. Vessels in culture were labelled with [3H]-glucosamine and processed for autoradiography and immunohistochemistry. Distribution patterns for proteoglycans and radio-labelling were determined morphometrically. RESULTS: Distribution profiles in coronary artery and saphenous vein were similar, with relatively high levels of subendothelial versican and biglycan and low levels of decorin. In culture subendothelial incorporation of [3H]-glucosamine and immunostaining for versican and biglycan, but not decorin, were significantly increased. In contrast, the thin intima of the ITA was relatively enriched in decorin compared with the medial layers and in culture intimal staining for decorin increased markedly compared with a modest increase for biglycan and no change for versican. There was an even distribution in radial artery of all three proteoglycans across the intima without subendothelial accumulations. In culture there was an increase in staining intensity for proteoglycans of the radial artery. Neither the ITA nor radial artery exhibited an increase in subendothelial incorporation of [3H]-glucosamine in culture. CONCLUSIONS: The distributions of proteoglycans, and responses to culture correlate to the known differences in patency between grafted saphenous vein and ITA and predict that the radial artery will outperform the saphenous vein but might not be as good as the ITA for long-term patency.

Tissue concentrations of endothelins and functional effects of endothelin-receptor activation in human arteries and veins.

In the present study, the tissue content and functional effects of endothelin-1 and endothelin-3 were examined in human vessels of importance in coronary bypass operations. Human coronary arteries (i.e., the left anterior descending coronary artery) were obtained from eight cardiac valve donors within 6 hours after death, pulmonary arteries were perioperatively obtained from 15 patients operated on because of lung tumors, and internal thoracic arteries and great saphenous and cephalic veins were obtained at coronary bypass operations from a total of 28 patients. Endothelin-1 and endothelin-3 content was quantified by radioimmunoassay. For functional experiments, the vessels were mounted in organ baths for recordings of isometric contractions in response to endothelin-1, endothelin-3, and the endothelinA-receptor agonist sarafotoxin 6c. In all vessels investigated, the endothelin-1 content was higher than that of endothelin-3. The highest levels were found in the left anterior descending coronary artery, followed in declining order by the internal thoracic artery, pulmonary artery, saphenous vein, and cephalic vein. Endothelin-1 contracted all vessels in a concentration-dependent fashion. This effect was enhanced in the left anterior descending and internal thoracic arteries by inhibition of nitric oxide and prostaglandin formation. The contractile effect was attenuated in a concentration-dependent fashion in all vessels by incubation with the endothelinA-receptor blocker BQ-123. Furthermore, contractions evoked by endothelin-1 in the left anterior descending coronary and pulmonary arteries were antagonized by the combined endothelinA- and endothelinB-receptor blocker bosentan. Endothelin-3 contracted the left anterior descending coronary and pulmonary arteries and the saphenous vein, but not the internal thoracic artery, in a BQ-123-sensitive fashion. However, after inhibition with nitric oxide or prostaglandin, endothelin-3 also contracted the internal thoracic artery, and the response in the left anterior descending coronary artery was enhanced. Sarafotoxin 6c evoked a BQ-123-sensitive contraction of the left anterior descending coronary artery. It is concluded that endothelinA receptors mediate the major portion of the vasoconstriction observed on exposure to endothelin-1, endothelin-3, and sarafotoxin 6c in the left anterior descending coronary, pulmonary, and internal thoracic arteries and the saphenous vein. Furthermore, endothelinB-receptor activation, with subsequent formation of nitric oxide or prostaglandin (or both), counteracts the vasoconstrictor response to endothelin in the left anterior descending coronary and internal thoracic arteries, but not in the pulmonary artery or saphenous vein. The present findings therefore suggest that endothelinA-receptor antagonism might prove beneficial in preventing possible endothelin-induced coronary graft spasm.

Fixation of bioprosthetic tissues with monofunctional and multifunctional polyepoxy compounds.

Collagen from a native tissue is fixed with a polyepoxy compound (PC) for use as a new biologic prosthetic material. Prior studies have shown that this biomaterial has comparable properties with collagen fixed with glutaraldehyde (GA), and thus has great promise for biomedical applications. A prior kinetic study indicated that the reaction between the functional groups of collagen and the multifunctional epoxy EX-313 is a 2.5th-order reaction. The purpose of this study was to understand the mechanism of the amino acid-PC reactions in a fixation process. Bovine arteries were fixed with a monofunctional PC (EX-131) and a multifunctional PC (EX-313) as a function of fixation time. A sequential fixation with a second fixative was used to identify the available remaining reactive sites from a prior fixation. The denaturation temperature (Td) was measured on each sample. Because the denaturation temperature is a direct indication of crosslinking of individual amino acids with the fixative, the increase in Td of a subsequent fixation may be indicative of the available remaining amino acids. The fixation index was measured on each sample to reflect the increase of fixation completion in a sequential fixation process. The fixation index and crosslink data also revealed that the reactive amino acids for EX-131 and EX-313 may not be exactly the same. The data in this study suggest that a monofunctional fixative can pre-react with the amino acids of collagen to effectively block further fixation of collagen with a second fixative. This amino acid masking may be associated with collagen branching. Collagen branching and its effect on denaturation temperature are described.

A pathohistological and biochemical study of arteriosclerosis in the internal thoracic artery, a vessel commonly used as a graft in coronary artery bypass surgery.

Pathohistological and biochemical studies were conducted on the severity of arteriosclerosis in the internal thoracic artery (ITA), an artery commonly used for coronary artery bypass grafting (CABG). For the pathohistological examination, 26 bilateral ITAs and 13 left anterior descending coronary arteries (LADs) obtained in full length from 13 autopsy cases, none of which had died of arteriosclerotic heart disease, were used. The ratio of the thickness of the intima to that of the media (R) was used as the index for arteriosclerosis. ITAs and LADs were classified as grades I to IV according to the value of R. The R of the ITAs was approximately 1/10 that of the LADs (P < 0.01). Most ITAs showed a low arteriosclerotic grade, with no variation in arteriosclerosis along their length and a low R in all segments. No difference was found between right and left ITAs. Biochemical examination was conducted on 12 ITAs and 11 LADs, obtained from 12 different and unselected autopsy cases. The lipid content in the vascular wall was determined to evaluate the severity of arteriosclerosis, with the following results: Total cholesterol, 5.5 +/- 1.8 and 17.8 +/- 13.6 micrograms/mg wet weight (P < 0.05); triglyceride, 90.4 +/- 90.3 and 114.4 +/- 117.2 micrograms/mg wet weight (n.s.); and phospholipid, 7.4 +/- 3.9 and 11.2 +/- 3.9 micrograms/mg wet weight (P < 0.05), respectively, for the ITAs and LADs. These findings thus demonstrate that arteriosclerosis of the ITA in Japanese people is very mild, compared to that of the LAD in the same individuals.

Producción comparativa de prostaciclina en arteria epigástrica inferior, arteria mamaria interna y vena safena: implicancias en el pronóstico de la revascularización miocárdica / Prostacycline production by the inferior epigastric artery, compared to the internal mammary artery and the saphenous vein

Se usó un sistema in vitro para medir la producción de PG12 en anillos aislados de la arteria mamaria interna, la arteria epigástrica inferior y la vena safena obtenidos en 5 pacientes durante cirugía de revascularización. La muestras fueron incubadas en solución Krebs'Ringer a pH 7.4. Por radioinmuoensayo (Amersham) se midió el 6-keto-PGF la, metabolito de PG12 en alicuotas del sobrenadante. La producción de arterias epigástrica fue 12,5 2,0 ng/mg/30 min, la de arteria mamaria interna 9,3 1,7 y la de vena safena5,1 0,7 (p 0,01). Por lo tanto, la arteria epigástrica inferior produce PG12 en cantidades similares a las de la arteria mamaria interna y considerablemente mayores que las de la vena safena. Ello podría traducirse en un mejor pronóstico de los puentes coronarios efectuados con arteria epigástrica comparados con las de la vena safena