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Zytoplasmatische tubuloretikuläre Komplexe und Kernsphäridien in Zellen rötelninfizierter menschlicher Embryonen und Feten

1975; Elsevier BV; Volume: 155; Issue: 2 Linguagem: Inglês

10.1016/s0005-8165(75)80187-9

0005-8165

G. Kistler,

Virus-based gene therapy research

The range of single or multiple defects which might develop in the human embryo or fetus after an intra-uterine rubella infection has been documented by means of a large number of epidemiological, clinical and pathological investigations. Newborns with congenital rubella carry a number of defects, some of which could be the direct result of a virus-induced, intra-uterine vascular damage. In rubella-infected embryos and fetuses, vascular lesions are the most frequently observed histopathological finding. These changes have already been systematically investigated by means of the light microscope. Ultrastructural data are, however, not available at present. The placentae and fetuses from 20 women with serologically confirmed rubella infection manifesting 2 to 15 weeks post menstruationem were investigated histologically and virologically. The products of conceptus from 16 women with legal abortion for psychiatric reasons served as controls. Fragments of the major organs from all the control cases and from 18 out of the 20 rubella cases were available for serial sectioning and light microscopic observation. Other fragments of the major organs from the 16 control fetuses and from all the 20 rubella cases were investigated electron microscopically by standard procedures (glutaraldehyde- and osmium-tetroxide fixation; dehydration in ethanols and propylenoxide; embedding in Epon; contrast-enhancement with lead citrate and uranyl acetate). In addition, homogenates of organ fragments (usually placenta, kidney, lung, heart and brain) from 16 out of the 20 fetuses from mothers with rubella in pregnancy were inoculated into cultures of Vero monkey kidney cells. The cultures were assayed for the presence of rubella virus by immunofluorescence and by conventional electron microscopy. The supernatants were checked by immuno-electron microscopy using human and rabbit rubella antisera. Rubella virus was isolated from various organs of 81% of the fetuses tested from mothers with rubella in pregnancy. The virus was identified a) by a positive immunofluorescence reaction in the Vero cell cultures which had been inoculated with the fetal organ homogenates, b) by the presence of typical rubella virus particles in thin sections prepared from the infected cell cultures and c) by the formation of virus-antibody complexes in the supernatants from these cultures after the addition of human or animal rubella antisera. Light microscopically, 72% of the fetuses derived from rubella-infected mothers revealed pathological changes. In the decidual parts of the placenta, perivascular and periglandular mononuclear infiltrates were usually present. The fetal organs displayed multifocal bleedings of variable degree. No inflammatory reaction was detected in the affected tissues. In the blood vessels and in the endocardium, focal swelling and necrosis as well as focal absence of endothelial cells were noted. The vessel lumina contained thrombi and emboli which consisted of pycnotic nuclei, cell debris and an eosinophilic fibrillar material. Such alterations were never detected in the organs of the control fetuses. Electron microscopically, 17 of the 20 fetuses (= 85%) obtained from mothers with rubella in pregnancy were found to display nuclear and cytoplasmic alterations in various cell types. A small proportion of vascular endothelial cells of practically all tissues contained an increased number of nuclear bodies (up to 7) as well as cytoplasmic tubulo-reticular complexes of variable size. Occasionally, such complexes were also observed in fibroblasts of the kidneys, in glioblasts of the cerebrum as well as in cytotrophoblast cells. They were formed by and situated within enlarged cisternae of the rough endoplasmic reticulum and consisted of branched tubuli with a diameter of approximately 25nm. Some of the endothelia containing these structures were heavily damaged, the cells displaying loss of the cytoplasmic ground substance, dilatation of the ER-cisternae and swelling of the mitochondria. All fetuses, from which rubella virus could be isolated in the cell cultures, displayed endothelial and other cells containing tubuloreticular structures, although mature rubella virus particles were not observed in thin sections of any of the fetal organs. In contrast, no tubuloreticular structures were noted in fetuses from which rubella virus could not be isolated. In the tissues of the control fetuses, these cytoplasmic alterations were never observed. Our data confirm the results of previous studies which have shown that in women with serologically proven rubella in early pregnancy, a generalized infection of the embryo or fetus is common, the risk being approximately 80%. In contrast to the still widespread opinion that the risk of a fetal damage is restricted to maternal infections occuring within the first 3 gestational months, our findings show that rubella manifesting in the mother as late as 15 weeks post menstruationem might lead to a transplacental infection. The presence of tubuloreticular complexes (TRC) in various cell types of 85% of the fetuses from mothers with rubella in pregnancy is a rather surprising finding. Since these structures have been described in a variety of postnatal pathological conditions such as virus infections, collagen diseases and malignancies, they cannot be regarded as rubella-specific. The regular occurence of TRC in the rubella-infected fetuses investigated as well as their absence in the control material indicates, however, that these alterations of the endoplasmic reticulum represent a special type of reaction of various cell types to the infection. The involvement of these structures in the pathogenesis of the rubella cardio-and vasculopathy is furthermore demonstrated by the detection of TRC-containing endothelial cells which were heavily damaged or even necrobiotic. It is probable that the emboli and thrombi which are regularly observed in intra-uterine viral infections result from the shedding of such dying endothelial cells into the vascular lumen. The TRC-containing cells of the rubella-infected fetuses display an increased number of nuclear bodies. These organelles have been described in a variety of fetal, postnatal, human and animal cells as well as in normal and pathological tissues. An increase in their number has been correlated with a metabolic hyperactivity of the cell. It is interesting to note that the number of nuclear bodies per cell is also increased in endothelia of patients with lupus erythematodes disseminatus who have often high titers of rubella (and measles) antibodies in their serum. The endothelial cells of these patients contain tubuloreticular complexes so regularly, that these structures are considered to be pathognomonic. No inflammatory reactions are observed in the tissues of the rubella-infected human fetuses. In the blood vessels, however, a small number of mononuclear cells is found to have phagocytosed necrobiotic cells — presumably endothelial cells — as well as cell debris. Zwanzig Feten und Plazenten von Müttern, die in graviditate an serologisch gesicherten Röteln erkrankt waren, wurden histologisch und virologisch untersucht. Von 18 dieser Feten konnten lichtmikroskopische Serienschnitte durch verschiedene Organe hergestellt werden. In 13 Fällen (= 72%)) ließen sich Gefäß-Schädigungen in Form multifokaler Endothelzellverluste, intravasaler Thromben und Emboli sowie multipler Parenchymblutungen feststellen. Die wichtigsten Organe der 20 Feten wurden elektronenmikroskopisch untersucht. Bei 17 Feten (= 85%) enthielten Gefäß-Endothelzellen praktisch aller Gewebe nebst Sphäridien in den Kernen (sog. nuclear bodies) tubuloretikuläre Komplexe variabler Größe, die in erweiterten Zisternen des rauhen endoplasmatischen Retikulum lagen und aus verzweigten Tubuli von ca. 25 nm Durchmesser bestanden. Vereinzelt ließen sich nuclear bodies und solche Komplexe auch in Fibroblasten der Niere, in Glioblasten des Großhirns sowie in Zytotrophoblastzellen der Plazenta beobachten. In der Regel zeigten Zellen mit tubuloretikulären Komplexen keine schwerwiegenden pathologischen Veränderungen. Da solche Strukturen jedoch auch in massiv geschädigten Zellen nachzuweisen waren, muß angenommen werden, daß dem endoplasmatischen Retikulum bei der Pathogenese der rötelnbedingten Gefäß-Läsionen eine entscheidende Rolle zukommt. Reife, aus Kern und Hülle bestehende Rötelnviruspartikel waren elektronenmikroskopisch in keinem der untersuchten fetalen Organe zu beobachten. Aus Homogenisaten verschiedener Organe von 16 Feten wurde das Virus jedoch in 13 Fällen (= 81%) isoliert und mittels indirekter Immunofluoreszenz, Elektronenmikroskopie und Immuno-Elektronenmikroskopie identifiziert. Alle Feten mit einem positiven Virusnachweis in der Zellkultur wiesen tubuloretikuläre Komplexe auf. Aus den Organen der 3 Feten ohne diese Strukturen wurde hingegen kein Virus isoliert. In den Geweben von 16 Kontrollfeten ungefähr gleicher Altersverteilung (Interruptio aus psychiatrischer Indikation) wurden tubuloretikuläre Komplexe nie festgestellt. Der Nachweis solcher Veränderungen des endoplasmatischen Retikulum in Zellen fetaler Organe kann daher als Indiz für das Bestehen eines intrauterinen Virusinfektes dienen. Die funktionelle Bedeutung der tubuloretikulären Komplexe, die auch bei verschiedenen postnatalen Virusinfekten sowie bei Kollagenosen und malignen Tumoren vorkommen, bleibt jedoch noch abzuklären.