The pathology of the early and late stages of primary pulmonary hypertension

In vitro effect of oestradiol on thymidine uptake in pulmonary vascular smooth muscle cell: role of the endothelium

1. The effect of different concentrations of oestradiol-17 beta (3-300 nM) on [3H]-thymidine uptake was studied in segments from canine pulmonary artery, and cultures of rat pulmonary vascular smooth muscle cells (VSMC). 2. Incubation with oestradiol-17 beta for 24 h, potentiated in a concentration-dependent manner [3H]-thymidine uptake in VSMC cultures. 3. Oestradiol-17 beta potentiated thymidine uptake by pulmonary arterial segments but only when the endothelium had been removed. Autoradiography showed dense incorporation of radioactive thymidine in the vascular smooth muscle cells of the media. 4. The non-steroidal oestrogen, stilboestrol (300 nM), also significantly potentiated [3H]-thymidine uptake, in both VSMC cultures and pulmonary artery segments. Testosterone was ineffective at a similar concentration. 5. Pre-incubation of the pulmonary VSMC with the anti-oestrogen tamoxifen (1 microM) antagonized the potentiating effect of oestradiol-17 beta on [3H]-thymidine incorporation. The effect of tamoxifen was less pronounced in pulmonary arterial segments. 6. These data suggest that oestrogen may promote proliferation of pulmonary VSMC. Endothelial injury or dysfunction may be an important factor in the expression of the oestrogenic effect. 7. We speculate that plasma oestrogen may be a contributing factor to the proliferative lesion observed in certain forms of pulmonary vascular injury in women.

Dynamic aspects of regulatory lung peptides in chronic hypoxic pulmonary hypertension

Male Sprague-Dawley rats were placed in hypobaric hypoxia for 17-21 d (FIO2 10%) to establish pulmonary hypertension (PH) and control rats were kept in normobaric room air. Right mean atrial and ventricular pressures (PRA, PRV) were recorded, left ventricular (LV) blood was collected, and lungs were perfused with heparinized saline. Hearts were removed to evaluate right ventricular (RV) hypertrophy (RV/(LV+septum)%). Peptides were quantitated with radioimmunoassay in lung tissue extracts and plasma. Wet lung weight, PRA, PRV, and RV/(LV+S)% were higher and body weight was lower in hypoxia rats, and lung morphometry revealed increased arterial medial thickness (MT/OD%) and elastification of arterioles and capillaries. Lung tissue CGRP, PYY, gamma 2-MSH, and SOM were higher in PH rats and ANP was unchanged. Blood AVP, CGRP, PYY, VIP, and SOM were reduced in PH rats and ANP was unchanged. Lung levels of PYY and SOM correlated significantly with the time in hypoxia and with all parameters examined and CGRP and gamma 2-MSH correlated with all but medial thickness. PYY had the highest correlation of the peptides with body weight, PRV, and RV/(LV+S)%, and SOM the highest with time in hypoxia, wet lung weight, PRA, MT/OD%, and elastification of arterioles and capillaries. Blood peptides correlated inversely with these parameters. ANP had the overall weakest correlations and CGRP, PYY, and SOM had the highest. SOM correlated the highest with arterial medial hypertrophy, PRV, RV hypertrophy, and elastification of peripheral capillaries. VIP correlated the highest of the blood peptides with body weight and wet lung weight. Statistically significant correlations do not necessarily imply causal relationships. The putative roles of these peptides in pulmonary function are discussed.

Clinical and pathologic manifestations of pulmonary vascular disease in the toxic oil syndrome

The toxic oil syndrome in Spain affected greater than 20,000 people. In the initial stages, it was characterized by a respiratory distress syndrome with myalgias and eosinophilia. Pulmonary hypertension developed in 20% of the patients and in many, it has spontaneously regressed. Nevertheless, in a small subgroup, it has progressed to a malignant course of cor pulmonale, leading rapidly to death. Clinical and pathologic features of 40 patients with severe pulmonary hypertension due to the toxic oil syndrome are presented (32 female and 8 male patients; mean age 26 +/- 13 years). The study began in June 1981, which was near the onset of the toxic oil epidemic, and ended in December 1987, greater than 6 years later. The pulmonary hypertension is clinically and pathologically indistinguishable from primary pulmonary hypertension. Direct endothelial injury by the toxic agent is proposed as the initial trigger of this type of pulmonary hypertension, but an interaction between the toxic agent and specific individual susceptibility is probably required in its pathogenesis.

Primary pulmonary hypertension in adults

Primary pulmonary hypertension is an enigmatic disease found predominantly in young women, but it also affects a significant number of middle-aged and elderly males and females. Its onset, characterized by progressively worsening dyspnea, fatigue, and chest pain, is insidious. Three distinct histopathologic subtypes have been identified, and the natural history of the disease process has been well-defined. Pharmacologic treatment options have, in general, been disappointing, and it appears that heart-lung transplantation will be applied only to a small minority of young patients with primary pulmonary hypertension in the near future. We review the histopathology, evaluation, treatment, and prognosis of primary pulmonary hypertension.

Modulation of actin isoform expression in alveolar myofibroblasts (contractile interstitial cells) during pulmonary hypertension

Lungs of 37 patients with pulmonary hypertension (PHT), 5 normal human lungs, and 30 normal rat lungs, were studied using immunohistochemical stainings for actin, alpha-smooth muscle (alpha-SM) actin and desmin. The type of PHT was determined on clinicopathologic grounds (in 17 cases by catheterism); 20 patients had precapillary and 17 postcapillary PHT. In normal lungs, myofibroblasts, ie, contractile interstitial cells (CIC), distributed in alveolar septa, were not stained by alpha-SM actin antibodies. Only around the venules, were cells labeled by this antibody present. Furthermore, there were bundles of alpha-SM actin-positive cells around the openings of air sacculi into the alveolar ducts. In precapillary PHT, the distribution and immunostaining properties of interstitial cells remained unchanged; alpha-SM actin-positive cells were observed in thickened arterial intima and in plexiform lesions. In postcapillary PHT secondary to heart failure, to mitral stenosis, or in veno-occlusive disease, many interstitial cells in the alveolar septa were decorated by alpha-SM actin antibodies but not with desmin. The authors propose that, in postcapillary PHT, mechanical stretch due to capillary congestion may be responsible for the generation of cells that express an actin isoform associated with smooth muscle.

The ultrastructure of plexogenic pulmonary arteriopathy

The lungs from 16 cases of plexogenic pulmonary arteriopathy obtained at heart-lung transplantation, half of which had primary pulmonary hypertension, were examined by electron microscopy. From these the probable pathogenesis of pulmonary arterial intimal fibrosis in plexogenic pulmonary arteriopathy was deduced. The earliest detectable change was migration of smooth muscle cells from the media, through the internal elastic lamina into the intima. These cells collected beneath the endothelium and lost many of their myofilaments to become myofibroblasts. They were associated with ground substance but scanty collagen fibrils. As the quantity of interstitial collagen increased, the myofibroblasts reverted to a muscular structure, became elongated, and assumed a regular, circumferential orientation. This later stage coincided with the development of plexiform lesions. At both early and later stages, the muscular pulmonary arteries were contracted but not markedly so, and muscular evaginations were not seen. On the other hand, the cellular intimal proliferations developed early and were occlusive. This suggests that occlusion of small pulmonary arterial vessels by myofibroblasts may be at least as important as vasoconstriction in the early elevation of the pulmonary vascular resistance in primary pulmonary hypertension.

Pulmonary endocrine cells in hypertensive pulmonary vascular disease

A study was made of the number of pulmonary endocrine cells, immunoreactive for gastrin-releasing peptide (bombesin) or calcitonin, in the terminal bronchioles of 39 cases of pulmonary vascular disease. In 25 of these, the form of vascular disease was plexogenic pulmonary arteriopathy, primary in 12 and secondary in 13, while the remaining 14 subjects had a wide range of other varieties of hypertensive pulmonary vascular disease. We found that pulmonary endocrine cells, especially those containing bombesin, were increased in number in both the primary and secondary forms of plexogenic pulmonary arteriopathy but not in other varieties of pulmonary hypertension. The prominent bombesin-containing cells were found in cases with cellular plexiform lesions but occurred even more prominently at an earlier stage when vascular smooth muscle cells were migrating from the inner media into the intima.

Pulmonary vasodilation with prostacyclin in primary and secondary pulmonary hypertension

Twenty-three patients with pulmonary hypertension underwent right cardiac catheterization and measurement of their response to a short-term infusion of prostacyclin. Pulmonary vasodilation with a greater than 20 percent fall in PVR occurred in all five patients with primary pulmonary hypertension where the predominant lesions were plexogenic; in three out of five patients where the predominant lesions were thrombotic; in three out of five patients with pulmonary hypertension and obstruction of proximal vessels; in three out of five patients with COPD; in both patients with pulmonary fibrosis due to sarcoidosis; and in the one patient with pulmonary veno-occlusive disease, where the pulmonary vasodilation was offset by a fall in arterial oxygen content. Prostacyclin is a safe and effective drug to use for testing the response of the pulmonary circulation to a vasodilator in pulmonary hypertension due to different causes. Short-term testing for a vasodilator response, with a view to instituting long-term therapy, should not be restricted to those patients with primary pulmonary hypertension due to plexogenic pulmonary arteriopathy.

Pulmonary blood vessels and endocrine cells in subacute infantile mountain sickness

A male infant of 16 months, of the Han race, died from subacute infantile mountain sickness in Lhasa (3600 m). At necropsy there was right ventricular hypertrophy secondary to muscularization of the pulmonary arteries and arterioles thought to have been induced by hypobaric hypoxia. In addition, there was intimal proliferation of myofibroblasts in the pulmonary arterioles, venules and veins. There were increased numbers within the bronchioles of pulmonary endocrine cells, containing calcitonin and bombesin, which could be related to hypoxia or trophic effects on the pulmonary vasculature. The relation of delayed effects of hypoxia to primary pulmonary hypertension is considered in this study.

Neuroendocrine cell populations in normal human lungs: a quantitative study

Pulmonary neuroendocrine cells, identified by their positive immunochemical reaction for neurone specific enolase, were readily demonstrable and uniformly distributed in 15 pairs of normal adult human lungs. About 65% contained gastrin releasing peptide and nearly all the rest contained calcitonin. Leucine-enkephalin was not found. Serotonin containing cells were few, and cells immunoreactive for adrenocorticotrophin and antidiuretic hormone were absent. About one in 10 cells was argyrophilic, and costorage of peptides was not seen.

Ultrastructure of early plexogenic pulmonary arteriopathy

A lung biopsy specimen from a young woman with the clinical features of primary pulmonary hypertension showed grade 2 plexogenic pulmonary arteriopathy. Electron microscopy revealed 'dark', electron-dense smooth muscle cells in the inner part of the media of muscular pulmonary arteries. Many of these transformed myocytes had migrated into the lumens of pulmonary arteries and arterioles which they occluded. This migration of smooth muscle cells was associated with a substantial increase in the number of pulmonary endocrine cells in the bronchioles containing bombesin and calcitonin.