Fetal Parotid Gland Structural Remodeling In Case Of Intrauterine Growth Retardation
Authors: Morozov Sergiy , Reshetnikova Olga 
Published: October 2013

The important biological role of saliva in maintaining of the homeostasis of the oral cavity environment, preventing infection and tooth decay is widely accepted. Salivary glands insufficiency may violate the balance between health and disease. Clinical data indicated that the destruction, agenesis and aplasia of salivary gland commonly followed with hypo salivation, low salivary flow, which resulted in severe caries and periodontal disease. Salivary gland dysfunction also frequently found in preterm and low birth weight newborns. But the information about structural background of abnormal salivation in early childhood is still limited. A presence of any correlation between salivary glands’ structural development and intrauterine restrictions of fetal growth (IUGR) is unclear. The aim of present study was to determine morphological and morphometric peculiarities of human parotid gland in case of IUGR at late gestation.  Material and methods Parotid glands of twenty human fetuses 20-22 weeks of gestation with diagnosed IUGR from late abortions material were compared with ten fetal glands in cases of induced abortions due to psychological reasons (control group). Tissue samples were immersion-fixed in 10% buffered formalin solution, embedded in paraffin wax.  Histological slides were stained routinely with hematoxylin & eosin, with Van Gieson's Stain.  Microscopical examination was performed on magnification x 40 and x 100. Stereometric study by point count method at magnification x 40 allowed finding out volume fractions (VF) of gland’s parenchyma and stroma. VF of lobule’s components (gland’s wall, gland’s lumen, duct’s wall, duct’s lumen, vessels, intralobular connective tissue) were registered at magnification x100. Morphometry of the secretory portion of the parotid gland was conducted on the Zeiss microscope with the help of the AxioVision Rel.4.8 program. The mature (differentiated) end pieces were measured, including their area (in mkm2), width, height, perimeter (all in mkm). Similar measurements were done in the foci of immature secretory ends of a gland. Additionally the mean height of the epithelial cells layer within the mature secretory end pieces was measured. The differences were analyzed by methods of mathematical statistics using the software Microsoft Excel; data was compared with control measurements by Student’s t-test.Results The results of present research have shown the delayed differentiation of fetal parotid gland’s parenchymal components in case of IUGR. The parenchymal VF did not reach control values.  Furthermore, VF of lobule’s components was also decreased. Ducts lumens appeared to be significantly narrower than at physiological gestation. Interlobular and intralobular connective tissue stroma, in contrast to the controls, occupied vast areas, and their volume fraction was increased. Deficit of the parenchymal components of the gland was enhanced by slower maturation of glands.  In cases with IUGR, differentiated glands occupied smaller area, with reduced width, height and perimeter. Epithelium lining the differentiated glands is characterized by significantly lower height compared to the control group. Delayed differentiation resulted in  higher proportion of immature glands. Their area, width, height and perimeter increased. IUGR was also accompanied with a variety of pathological changes. Conclusion Present evidences suggest that IUGR leads to impaired growth and maturation of the parotid gland. Structural immaturity and lack of differentiated parenchymal elements of the organ may form the basis of its secretory function’s lesion. The finding tends to support the hypothesis that the mechanism behind the increased risk of dental pathology in preterm, low birth weight and retarded children is centred at structural and functional immaturity of salivary gland.