Intimal thickening of human femoral arteries with special regard to elastin, Part 1. Diffuse intimal thickening due to growth and age

High accumulation of minerals in the human arteries of lower limb

To elucidate accumulation of minerals in the human arteries, the relative contents (RCs) of minerals in the arteries of the upper and lower limbs were analyzed by inductively coupled plasma atomic emission spectrometry. It was found that the RCs of calcium and phosphorus in the femoral and popliteal arteries of the lower limb increased with aging, whereas those in the axillary and radial arteries of the upper limb did not increase with aging. This result indicates that higher accumulation of calcium and phosphorus occurs in the arteries of the lower limb with aging as compared with that in the arteries of the upper limb, and the prevalence of arteriosclerosis increases in the arteries of the lower limb with aging but not in the arteries of the upper limb.

High accumulation of elements in the human femoral artery

The relative contents (RCs) of elements in the femoral arteries as well as the thoracic aorta, coronary, basilar, and radial arteries from 26 subjects within the age range between 55 and 92 yr old, were analyzed by inductively coupled plasma atomic emission spectrometry. The RCs of calcium and phosphorus in the femoral arteries started to increase before the age of 60 yr. The RCs of magnesium increased after the age of 70 yr. However, the RCs of sulfur did not change significantly within the age range between 55 and 92 yr. With regard to localization of the mineral accumulations in the femoral arterial wall, it was found that the accumulations of calcium and phosphorus occurred only in the tunica media, only in the tunica intima, or in both the tunica media and the tunica intima. The manner of accumulation of calcium and phosphorus in the femoral arterial wall was different from that in the aortic wall. The average RCs of calcium in the 26 specimens were the highest in the femoral artery, followed in descending order by the thoracic aorta, coronary, basilar, and radial arteries. The average RCs of phosphorus were highest in the thoracic aorta, followed by the coronary, femoral, basilar, and radial arteries. It is noted that the accumulation of mineral elements never occurred uniformly in all the arteries.

Changes in morphology of elastin fibers during development of the tunica intima of monkey aorta

The normal development of elastin fibers in the thoracic aorta was studied in fetal, young, and adult monkeys. Tissue was examined by scanning electron microscopy (SEM) after NaOH treatment and by transmission electron microscopy (TEM). The NaOH treatment of fixed tissues effectively removed collagen fibers and enabled three-dimensional visualization of the elastin fibers. In intact fetal aortae, the internal elastic lamina (IEL) was situated immediately beneath the endothelium. This IEL consisted of superficial, longitudinally arranged bundles of elastin fibrils and an underlying solid sheet containing round fenestrations. In neonates, diffuse intimal thickening was observed. In the young and young-adult monkeys, the aortae exhibited intimal thickening with slender but split IEL. One of the most important findings of this study was that elastin fibers in the intimal thickening, as well as smooth muscle cells, ran in a longitudinal fashion. This was in contrast with the elastic laminae of the media which were mainly oriented circumferentially. Subendothelial elastin fibers in this intimal thickening combined with longitudinally arranged microfibrils which formed close associations with endothelial stress fibers. In some adult monkey aortae with well-developed intimal thickening, a complex meshwork of slender elastin fibers was also found beneath the endothelium. The development of the intimal elastin fibers is discussed in relation to hemodynamic forces.

Vascular nature of pre-eclampsia

The etiology of preeclampsia is not known. There are some partial well established mechanisms like decreased refractoriness to vasoactive agents, reduced placental and artery wall production of prostacyclin, increased production of thromboxane, and luminal trophoblast invasion of spiral arteries. We propose that it would be of primary importance to elucidate the role of uterine artery as an early pathway of preeclamptic disease. Defective hypertrophy of the uterine artery during pregnancy may give way to stretching, distortion and narrowing of the arterial lumen. The rate of growth of the pregnant uterus may not be synchronous with the expected hypertrophy of the uterine artery, thus jeopardizing the blood flow in its branches, such as arcuate and spiral arteries. This disturbance may cause non invasion by the trophoblast of the spiral arteries and subsequent placental hypoxia. Exaggerated uterine volume, like multiple pregnancy, hydatiform mole and hydramnios, may facilitate preeclampsia by demanding more blood supply from an inadequate uterine artery. The prevalence of preeclampsia in primiparous women can be understood, since additional pregnancies will find the uterine arteries already elongated, at least to some extent.

Spontaneous arterial lesions: their possible role in arteriosclerosis

Spontaneous lesions of the arterial wall involving the internal elastic lamellae and variable amounts of the intima are described in the spontaneously hypertensive rat caudal, renal, and mesenteric arteries. A simple model for producing similar circumferential lesions in rat and rabbit carotid arteries has been developed and the subsequent repair of these lesions is described. Two types of circumferential lesion can be produced by the application of 50-160 g of longitudinally applied tension. Small lesions can be up to 400 micron in length and are characterized by the loss of a small area of endothelium and rupture of the internal elastic lamellae. No demonstrable damage to the media is detected in these lesions. Larger lesions can be up to 1 mm in length and are characterized by the loss of endothelium and rupture of the internal as well as a variable number of medial elastic lamellae. Little, if any, damage to the medial smooth muscle cells is observed although the extracellular matrix is often disrupted. Small lesions are completely reendothelialized within 24 hr and larger lesions within 7-10 days. Both large and small lesions repair without the formation of an intimal thickening of smooth muscle cells, despite quite marked damage to the media of the larger lesions.

Regeneration of the arterial wall in microporous, compliant, biodegradable vascular grafts after implantation into the rat abdominal aorta. Ultrastructural observations

The ultrastructure of a new type of vascular graft, prepared from a mixture of polyurethane (95 weight %) and poly-L-lactic acid (5 weight %), was examined six weeks after implantation into the abdominal aorta of rats. These microporous, compliant, biodegradable, vascular grafts function as temporary scaffolds for the regeneration of the arterial wall. Smooth muscle cells, covering the grafts, regenerated a neo-media underneath an almost completely regenerated endothelial layer (neo-intima). These smooth muscle cells varied in morphology from normal smooth muscle cells to myofibroblasts. They were surrounded by elastic laminae and collagen fibers. Macrophages, epithelioid cells, multinucleated giant cells, fibroblasts and capillaries were present in the disintegrating graft lattices. The epithelioid cells and multinucleated giant cells engulfed polymer particles of the disintegrating grafts. The regeneration of the endothelial and smooth muscle cells is similar to the natural response of arterial tissue upon injury. The presence of macrophages, epithelioid cells, multinucleated giant cells, fibroblasts and capillaries in the graft lattices resembles the natural response of tissue against foreign body implants. Both of these responses result in the formation of a neo-artery that possesses sufficient strength, compliance and thromboresistance to function as a small caliber arterial substitute.