Summary:
Aim: The splenic parenchymal microenvironment plays an important role in
haematopoietic activity during the second trimester gestation, period in which
extramedullary haematopoiesis takes place in the spleen of the developing
foetus. Extracellular matrix (ECM) structural glycoproteins (tenascin, laminin
and entactin) have been identified as part of this microenvironment by
promoting haematopoietic progenitor/stem cells for further maturation,
proliferation and differentiation in the final and different haematopoietic
lineages. Also, ECM molecules play important roles during lymphoid tissue
embryogenesis, regulating many cell functions in central and peripheral
lymphoid organs such as lymphocytic differentiation, migration and activation.
Chorioamnionitis is by far the most common form of placental inflammation in
which, ascending infective microorganisms, usually bacteria, ascend into the
uterus from the vagina producing an inflammatory reaction in the foetal
membranes, umbilical cord, and ultimately within the foetus itself.
The objective of the retrospective study was to determine the effects of
chorioamnionitis on the ECM structural glycoporoteins (tenascin, entactin and
laminin) of the developing human foetal spleen, and how these changes can
influence the haematopoiesis and the development of the immune component of
this organ. Our findings are correlated with the equivalents of foetuses
without evidence of chorioamnionitis.
Material and Methods: After elective induced pregnancy termination due to
chorioamnionitis, paraffin-embedded specimens from the spleen of ninety human
foetuses with their respective foetal membranes were investigated by
immunohistochemical technique for the presence of ECM structural glycoproteins
(tenascin-C, entactin and laminin), haematopoietic and lymphoid cells. Thirty
foetuses corresponded to the 10th to 12th gestational week (end of first
trimester), thirty to 16th to 24th week of gestation (second trimester) and
further thirty to the 25th to 32nd gestational week (third trimester).
Specimens of human foetal spleen with their respective foetal membranes from
thirty cases of voluntary abortion due to other causes except for
chorioamnionitis, were examined also as control subjects. Conventional
histological examination of the relative foetal membranes revealing changes of
acute chorioamnionitis, was performed.
Results: Our results showed at the end of the first trimester of development in
both of our cases (chorioamnionitis and those after voluntary abortions) no
quantitative variations to the expression of the ECM glycoproteins (tenascin-C,
entactin and laminin) of the foetal parenchyma. During the second and third
trimester, the cases featuring changes of acute chorioamnionitis showed a
decreased number of the above proteins in comparison with the control subjects
checked at the same period. Regarding haematopoietic lineages, we did not find
any quantitative variation, in both of our cases (chorioamnionitis and those
after voluntary abortions), at the end of the first trimester. However, during
the second and third trimester an increase of granulopoiesis and CD34
progenitor/stem haematopoietic cells was observed, whereas the immune system of
the spleen during the third trimester demonstrated a decrease of both B and T
lymphocytes, in comparison with the results of the control subjects.
Conclusions: These results suggest that circulating products of bacterial
growth such as toxins and cytokines, generated during chorioamnionitis, seem to
influence ECM structural glycoproteins synthesis and release in the foetal
splenic parenchyma by reducing them, and probably causing further disorders of
haematopoiesis and lymphopoiesis.
Keywords:
Consequences, Horioamnionitis , Structural ECM, Fetus, Spleen
