Morphological changes in the umbilical arteries of babies born to pre-eclamptic mothers: an ultrastructural study

Placenta (1984), 5, 419-426

Morphological Changes in the Umbilical Arteries of Babies Born to Pre-eclamptic Mothers: an Ultrastructural Study C. D A D A K a, W. U L R I C H b & H. S I N Z I N G E R c a 2nd Department of Obstetrics and Gynaecology, b Department of Pathology, and ~ Atherosclerosis Research Group (ASF) at the Department of Medical Physiology, University of Vienna, Vienna, Austria

INTRODUCTION Recently, Asmussen and Kjeldsen (i 975) reported that human umbilical arterial morphology is markedly altered in babies born to smoking mothers. Several authors have also noted that prostacyclin (PGI2), the most potent vasodilator and inhibitor of platelet aggregation known so far, is formed in decreased amounts in the vascular wall in smokers (Wennmalm, I978; Masotti et al, I98o ). In earlier studies we have shown a decreased synthesis of prostacyclin by the umbilical arteries of babies born to smoking and pre-eclamptic mothers (Dadak et al, i98i , I982). Morphological and biochemical findings in human umbilical arteries are of special importance in so far as they are an indication of vascular damage which may lead to a disturbed arterial flow; they may also be indicative of abnormalities throughout the whole fetal arterial system. It was the aim of this study to investigate, in babies born to pre-eclamptic mothers, arterial morphology at an ultrastructural level.

MATERIALS AND METHODS We examined the umbilical arteries of babies from ten normal pregnancies and those of ten babies delivered to mothers suffering from pre-eclampsia. Table i gives the mean values of age, duration of pregnancy, the mothers' systolic and diastolic blood pressures, fetal weights, Apgar scores, pH of umbilical arterial and venous blood, and the duration of pre--eclamptic symptoms. The range of maternal systolic blood pressures was I6O to 2io m m H g (2I. 3 kPa to 27.9 kPa), and the range of diastolic blood pressures was 9o to i 15 m m H g (I i. 9 kPa to I5.3 kPa); hence, only severe cases ofpre--eclampsia, as defined by the American Committee of Maternal Welfare, were included in the study group. All patients were Caucasians, and there were no differences in socio-economic status between the two groups. All babies in the normal group were from spontaneous vaginal deliveries; in the pre-eclamptic group five babies were delivered by caesarean section, two by forceps and three by normal spontaneous vaginal delivery. Smokers and patients with diabetes mellitus or other diseases were excluded from the study. Rings of umbilical cord were taken immediately after delivery, one at a constant distance from 4x9

420

C. Dadak, W. Ulrich, H. Sinzinger TaMe i. Clinical data of patient groups

Patient group Normal n

Age Duration of pregnancy (weeks) Duration of pre-echmpsia (weeks) Systolic BP (mmHg) Diastolic BP (mmHg) Birthweight (g) Apgar i' Apgar 5' pH of umbilical arterial blood pH of umbilical venous blood

Pre--eclamptic

IO

IO

25.4 4- 5.8 39.2 4- 2.o -i x8.7 4- 8.3 73.3 4- 6.4 3235.7 4- 503 . i 8.5 4- 1.8

25.3 + 5.3 38.7 + 2.3 7.8 + 4.8 177.I + 2o.6 ioi. 4 + 11 .i 2855.7 -+ 697.0 7 A +_2.3 8.1)__+I "9 7.22 4- o.o5 7.29 _+o.o4

9.6 4- i-5

7.24 4- o.o7 7.32 4- 0.o7

t h e fetal i n s e r t i o n (2o c m ) a n d t h e o t h e r xo c m f r o m t h e p l a c e n t a l i n s e r t i o n site. T h e s e w e r e t r a n s f e r r e d to 2. 5 p e r c e n t b u f f e r e d (o. i p e r c e n t c a c o d y l a t e , p H 7.4) g l u t a r a l d e h y d e . O s m i u m f e r r o c y a m i d e was u s e d for p o s t f i x a t i o n . A f t e r e m b e d d i n g in E p o n 812, t h i n s e c t i o n s w e r e c u t o n a n L K B - 4 8 o 2 A u l t r a m i c r o t o m e , s t a i n e d a c c o r d i n g to R e y n o l d s (i 963) a n d e x a m i n e d o n a Z e i s s EM 9 S electron microscope. The morphological findings were evaluated semiquantitatively ( T a b l e 2).

RESULTS Morphological

findings

I n u m b i l i c a l a r t e r i e s o b t a i n e d f r o m b a b i e s b o r n to p r e - - e c l a m p t i c m o t h e r s , t h e e n d o t h e l i a l cell ( E C ) l i n i n g was m a r k e d l y a l t e r e d . T h e e n d o t h e l i a l cells t e n d e d to p r o t r u d e i n t o t h e l u m e n , to s h o w a focal loss o f i n t e r c e l l u l a r j u n c t i o n s , a n d to f o r m a n i n c r e a s e d n u m b e r o f i n t r a l u m i n a l c y t o p l a s m i c b l e b s . S o m e o f t h e cells w e r e e n l a r g e d , o c c a s i o n a l l y a l m o s t b a l l o o n - l i k e , b e c a u s e o f

Table 2. Semiquantitative morphological data on umbilical arteries

Morphological findings Rough endoplasmic reticulum in EC Mitochondria in EC Metabolically activated SMC Lipid vacuoles in SMC Glycogen storage in SMC Multivesicular bodies Myelinoid bodies (subendotheliai) Lysosomes and large phagosomes in EC and SMC Basement membrane thickening Detachment of EC Oedema in subendothelial space

Pre-eclamptic arteries

Normal arteries

+ + + + + + + + + + + + + + + + + + + +

++ ++

+ + + + + +

+

++ +

EC = endothelial cells; SMC = smooth muscle cells. + + + + = ioo per cent of cases; + + + = 51~9 per cent of cases; + + = 26--5o per cent of cases; + = 25 per cent of cases.

Ultrastructure of Umbilical Arteries

4zl

distension of an abundant, clearly excessive, rough endoplasmic reticulum (Figure z, cf. Figure i). The cytoplasm of the endothelial cells contained many large, tightly packed mitochondria and numerous lysosomes and phagosomes (Figure 3). In the oedematous sub-intimal space a number of irregularly arranged smooth muscle cells (SMC) were found; these showed signs of metabolic activation (Figure 4), an increase in rough endoplasmic reticulum, Golgi apparatus and glycogen granules being noted. Focal glycogen accumulation, also seen in the endothelial cells, was often associated with intracytoplasmic lipid droplets. In some areas the endothelial cells had become detached and SMC covered the luminal surface of the vessel wall (Figure 5)Increased amounts of basement membrane material, in relation to both endothelial cells and smooth muscle cells, were noted. A further conspicuous finding was the increased number of multivesicular bodies in the endothelial cells and the presence of myelinoid bodies in the subendothelial space close to the endothelial cell membrane and in the cytoplasm of smooth muscle cells (Figures 2, 3, 6). No quantitative or qualitative morphological differences between the two segments, at the fetal and placental ends of the cord, could be detected. Morphological

Figure I. Electron micrographof normal umbilicalartery wall with regularshapedendothelial cells and intact surface lining. • 57oo.

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C. Dadak, W. Ulrich, H. Sinzinger

Figure 2. Protrusion of endothelialcells(EC) into the vascularlumen (L), enrichment in rofighendoplasmicreticulum.

Note alsomultivesicularbodies(arrowheads)in endothelialcellsand massiveglycogenstoragein subendothelialsmooth muscle cells (SMC). • io 4oo.

findings from normal umbilical arteries and umbilical arteries from babies of pre-eclamptic patients are compared and summarized in Table 2.

DISCUSSION T h e morphological alterations in the vessel wall in umbilical arteries from babies born to smoking mothers have been attributed to a decreased oxygen tension in fetal blood (Asmussen, I982 ). We thus assume that a similar mechanism might be responsible for the ultrastructural findings in the umbilical arteries of babies of pre-eclamptic women. Proliferation of smooth muscle cells, increased lipoprotein uptake and decreased lipoprotein degradation are all changes observed in vascular tissue cultured under hypoxic conditions (Chamley-Campbell, Campbell and Ross, 1979). In some areas severe hypoxic damage to endothelial cells leads to their detachment and the replacement of endothelial cells by subintimal smooth muscle cells which

Ultrastructure of Umbilical Arteries

4z3

Figure 3. Endothelial cells (EC) containing many lysosomesand multivesicularbodies (arrowheads). x io 4oo.

form a neointima (Schwartz, Stemerman and Benditt, I975). An increase in rough endoplasmic reticulum is a typical feature of metabolically activated smooth muscle cells which are capable of synthesizing large amounts of collagen and other connective tissue elements. The focally thickened basement membrane may be the result of an increased collagen synthesis. A distension of endoplasmic reticulum in endothelial cells has previously been observed by Asmussen and Kjeldsen (i 975) in umbilical vessels injured by tobacco smoking. I f one takes into consideration the fact that mitochondria are the cellular sites for oxidative phosphorylation and ATP production, their accumulation in endothelial cells may indicate an accelerated cellular turnover. The presence of large phagosomes might also correspond to this fact. Myelinoid bodies, as a pathological finding in umbilical arteries, have not been reported previously. Their occurrence in the subendothelial space may indicate a disturbance of the lipid metabolism within the vessel wall. Myelinoid bodies are a consequence of an accumulation of lipid substances (Ghadially, I982). However, enzymatic defects of injured cells might be responsible for the diminished breakdown of lipid residues (Ghadially, 1982). The alterations mentioned above may be the result of a disturbance in arterial blood flow which results in fetal hypoxia during pregnancies complicated by pre-eclampsia. The reduced fetal oxygen tension may, as in experimental studies, lead in cases of mild hypoxia to an increase of fetal arterial pressure with enhanced umbilical blood flow, but severe fetal hypoxia results in vasoconstriction of the umbilical vessels

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C. Dadak, W. Ulrich, H. Sinzinger

Figure 4. Activatedsmoothmusclecell(SMC) in the intimaofan umbilicalartery showingincreasedroughendoplasmic

reticulum and many Golgi areas. Note also the glycogenstorage (G) in another smooth musclecell in the vicinity. x I9 30o.

(Dawes, I962 ). Behrman et al (197 o) reported that in cases of fetal distress consequent upon a gradual reduction in maternal arterial oxygen tension the umbilical blood flow was significantly reduced. Possibly, umbilical vasoconstriction is due to a loss of endothelial cells and a subsequent deficiency of prostacyclin.

SUMMARY The umbilical arteries of babies from ten normal pregnancies and from ten babies born to preeclamptic mothers were studied. Ultrastructurally, there were marked abnormalities of umbilical arterial morphology in the pre-eclamptic group. A loss of intercellular junctions, distension of the endoplasmic reticulum and an increase in cell organelles in the endothelial cells

Ultrastructure of Umbilical Arteries

425

Figure 5. Area of de-endothelialization. A smooth muscle cell (SMC) covers the luminal surface, x 4o00.

leading to a partial de--endothelialization was noted. S m o o t h m u s c l e cells s h o w e d the m o r p h o l o g i c a l features o f m e t a b o l i c activation. T h e s e u l t r a s t r u c t u r a l findings c a n b e a t t r i b u t e d to fetal hypoxia a n d to d i s t u r b a n c e s in cellular lipid m e t a b o l i s m ; they suggest t h a t t h e r e m a y b e a n a b n o r m a l fetal arterial blood flow in m a t e r n a l pre--eclampsia.

REFERENCES Asmussen, L (I 982) Ultrastructure of human umbilical arteries from newborn children of smoking and non-smoking mothers. Acta Pathologica, Microbiologica et Immunologiea Scandinavica, Section A, 9o, 375-383Asmussen, 1. & Kjeldsen, K. (I975) Intimal ultrastructure of human umbilical arteries. Observations of arteries from newborn children of smoking and non-smoking mothers. Circulation Research, 36, 579-589 . Behrman, R. E., Lees, M. H., Peterson, E. N. et al (197o) Distribution of the circulation in the normal and asphyxiated fetal primate. American Journal of Obstetrics and Gynecology, io8, 956-969. Chamley-Campbell, J., Campbell, G. R. & Ross, R. (1979) The smooth muscle cell in culture. Physiological Reviews, 59, I'-61. Dadak, Ch., Leithner, Ch., Sinzinger, H. & Silberbauer, K. (i98i) Diminished prostacyclin-formation in umbilical arteries of babies born to women who smoke. Lancet, i, 94.

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Figure 6. Myelinoid bodies in the subendothelial space (arrowheads). Note also proliferating endothelium (EC) with enlarged nuclei. • xo 4oo.

Dadak, Ch., Kefalides, A., Sinzinger, H. & Weber, G. 0982) Reduced umbilical artery prostacyclin formation in complicated pregnancies. American Journal of Obstetrics and Gynecology, I44, 792-795. Dawes, G. S. (t962) The umbilical circulation. American Journal of Obstetrics and Gynecology, 84, 1634-1648. Ghadially, F. N. (i982) Myelin figures and myelinosomes. In Ultrastructural Pathology of the Cell and Matrix. end Edition, pp. 458-464. Sevenoaks, UK: Butterworths. Masotti, G., Poggesi, L., Galanti, G. et al (198o) Cigarette smoking lowers circulating prostacyclin and prostacyclin produced by vessel wall in man. XII. World Congress of Anglology, Athens I98O, abstract 343. Reynolds, E. S. (1963) The use of lead citrate at high pH as an electron-opaque stain in electron microscopy. Journal of Cell Biology, x7, 208. Schwartz, S. M., Stemerman, M. B. & Benditt, E. P. (t975) The aortic intima. II. Repair of the aortic lining after mechanical denudation. American Journal of Pathology, 8t, 15-42. Wennmalm, A. (1978) Effects of nicotine on cardiac prostaglandin and platelet thromboxane synthesis. BritishJournal of Pharmacology, 64, 559-563-