MORPHOFUNCTIONAL FEATURES OF THE PLACENTA IN PREGNANT WOMEN WITH TUBERCULOSIS

The quality of the placental complex has a significant impact on the harmonious development of the fetus in the womb. Paradoxically, descriptions of placental pathology in patients with tuberculosis (TB) are scarce. Objective : To study the morphology of the placenta in pregnant women with TB. Methods : The morphology of the 26 placentas was evaluated in this study, out of which 15 were from women with various forms and localizations of TB (main group), while 11 were from healthy pregnant women (control group). The placentas were evaluated macroscopically. Central and peripheral zones of the placenta and umbilical cord were sampled and embedded in paraffin. Histological slides were stained with hematoxylin-eosin and examined using an Olympus CX-21 microscope with a Universal Infinity Optical System (UIS2). Results : Women in the main group were significantly more commonly underweight (p<0.01) compared to the control group. They also showed a significantly higher frequency of decompensated chronic placental insufficiency (PI), increased share of immature intermediate differentiated villi, dystrophic and degenerative changes in the placenta (foci of dystrophic calcification, afunctional syncytial nodules), and circulatory disorders (ischemic necrosis, fibrinoid in the intervillous space). Foci of calcification and infarctions in the villi embedded in fibrinoid were also significantly more common in the main group. Compensatory changes included pronounced angiomatosis, hypervascularization of villi, an increase in the number of terminal villi, the formation of synticiocapillary membranes, and functional syncytial nodules. Conclusion : TB in pregnant women leads to morphological and functional changes in the placenta (delayed villous maturation, disorders of the uteroplacental circulation) and the development of more severe forms of chronic PI. The compensatory changes in the placenta might not sustain the required level of its blood supply, which results in deterioration of the perinatal outcomes (intrauterine growth restriction – IUGR).


Introduction
The placenta may be considered to be one the most important organs of the human body, which, during its temporary existence, takes on the functions that are later taken over by different organs, such as the lungs, intestines, kidneys, etc.In recent years, more pathologists, obstetricians, and pediatricians have started recognizing its real significance and taking an interest in its study [1][2][3][4].The harmonious development of the fetus in the womb is greatly dependent on the structure of the placental complex.Paradoxically, descriptions of placental pathology in pregnant women with TB are scarce, although the placenta is easily accessible for examination, and its study is safe for both the fetus and the mother [5][6][7][8].
Histologically, infection is usually recognized by inflammatory changes.Kashchenko-Hofbauer cells which are fetal macrophages of the human placenta, are present in the stroma of the chorionic villi starting from three weeks of the gestational age.Some studies have shown that these cells not only control villi remodeling and differentiation, and other functions of the placenta but also play an important role in the control of infection during pregnancy.In the full-term placenta, the number of Kashchenko-Hofbauer cells increases when the level of pro-inflammatory cytokines, such as IL-6, MCP-1, and IP-10, elevates [1,3,9].
The pathology of the placenta in TB is described as placentitis with caseous granulomas of the villi and decidual tissue.Even if the placenta is severely affected by the TB infection, the transmission of Mycobacterium TB to the fetus may hardly take place.Cases of placental TB are described, in some of which an acute abscess-like inflammatory reaction with an abundance of acid-fast mycobacteria is observed, with prominent histiocytic and neutrophilic response with myeloperoxidase, mediated by the innate immune system, causing acute villitis and intervillitis [8,[10][11][12][13].
Specific pathological changes in the placenta result in IUGR.In patients with active forms of respiratory TB, a decrease in the average weight and thickness of the placenta is accompanied by the low birth weight of the newborns [9,11,14].
There is also an opinion that Mycobacteria TB can potentially damage the placental barrier, penetrate into the placenta, and infect the fetus.Trivedi N et al (2020) report a case of placental TB diagnosed by histological examination.The changes were characterized by focal caseating granulomatous reaction with Langhans giant cells and acid-fast bacilli on the Ziehl-Neelson stain.Placental TB was expressed mainly by neutrophilic and histiocytic reaction in the form of villitis and intervillitis, which contributed more to tissue damage than to defense, and led to intrauterine fetal death [10].
Valdoshova SSh Morphology of the placenta in tuberculosis syncytial nodes, fibrinoid degeneration, stromal fibrosis, hypervascularization of villi were observed in 33.33% of TB cases compared to 8-11% in the control group (p>0.05)[12].When caseous lesions rupture into the amniotic cavity, there is a high risk of developing a congenital form of fetal infection as a result of aspiration of its contents, as some authors note in their works on the atypical manifestation of a specific process [3,15].PI is not an uncommon syndrome in obstetrics [16,17].Impaired placental angiogenesis and differentiation of the villi in pulmonary TB, revealed by immaturity of the villi, lead to chronic PI.Infection interferes with compensatory morphological mechanisms in the placenta, as a result of which the maternal-placental-fetal relationship is disrupted, which is clinically manifested by complicated fetal outcomes.The level of fetal complications is directly proportional to the prevalence and severity of the infectious process [18,19].
Other researchers describe impairment of vascularization of the placental villi, the formation of sclerosed and avascular terminal villi in the placentas of women with an active pulmonary TB, which is accompanied by decompensated PI.With fetal hypoxia, the number of terminal villi in the placenta increases.Morphological changes in the placenta include infarctions, fibrin deposits, immaturity of the villi, villitis, and atherosclerosis of the spiral arteries.Compensatory processes are not able to fully sustain placental blood flow, which ultimately leads to IUGR [20][21][22][23].
Based on the above literature data, it may be concluded that the study of the morphological features of placentas in pregnant women with TB remains theoretically and practically relevant.

Purpose of the study
The study of the morphology of the placenta of women suffering from TB during pregnancy.

Methods
Macro-and microscopic studies of the placenta and fetal membranes were carried out in the Pathomorphology and Immunohistochemistry of Human Tumors Department, Republican Cancer Research Center.A total of 26 placentas were studied, of which 15 were from women with TB (the main group) and 11from healthy women (the control group).
Criteria for inclusion in the main study group were: TB diagnosed during pregnancy or pregnancy developed on the background of anti-TB therapy.
Criteria for exclusion from the groups: TB treatment completed before the current pregnancy; severe concomitant somatic pathology.
All sampled placentas and umbilical cords were examined macroscopically.Placentas were weighed; their volume was calculated with the volume displacement method.Samples taken from eight central and peripheral parts of the placenta (Milovanov AP et al, 1991) were embedded in paraffin.Histological slides were examined using an Olympus CX-21 microscope with a UIS2 optical system.
The severity of damage was considered mild, moderate, or severe.The level of PI was assessed using the classification of Kolobov VA et al, 2011 [24].
All patients gave informed consent for the pathological examination of the placenta.
The obtained data were processed using IBM SPSS Statistics 26.0 (IBM, USA) and Statistica 10.0 (StatSoft Inc., USA) software.Quantitative indicators were presented as the mean value and its standard deviation (M±σ), and qualitative indicators were presented as shares (%).For multiple comparisons of quantitative indicators, the Kruskal-Wallis test was used, for post-hoc analysis and comparison of paired values, the Mann-Whitney test was used.Comparison of qualitative indicators was carried out according to the χ 2 criterion, and in cases where at least one field of the four-field table had a value less than 10, the Yates correction was applied.The null hypothesis was rejected at a significance level of p<0.05.

Results and discussion
Тhe age of pregnant women ranged from 20 to 44 years.The mean age of women in the main group was 27.4±5.7 years, and in the control group -24.4±3.5 years (p>0.05;U=319.0;Z=1.89).
TB was diagnosed in the first trimester of pregnancy in 4 (27%) women, in the second -in 5 (33%), and in the third -in 1 (7%).In 5 (33%) women it was diagnosed before the current pregnancy, the study was conducted on the background of anti-TB therapy.
The average body mass index was 19.3±1.9 kg/m 2 in the main group and 23.2±3.2kg/m 2 in the control group (p=0.003;U=249.0;Z=-2.89).The distribution of body mass indexes is shown in Fig. 1.
As follows from Fig. 1, underweight (<18.9 kg/m 2 ) significantly prevailed in the main group compared to the control group (p=0.043;χ2=3.35).A normal mass index (19.0-24.9kg/m 2 ) was observed in the main and control groups with approximately the same frequency; overweight (25.0-29.9kg/m 2 ) was observed only in the control group.
As follows from Fig. 2, eccentric insertion of the umbilical cord prevailed over the central one in both groups, however, it was more common in the control group, although the difference was statistically insignificant (p>0.05;χ 2 =0.07) (Fig. 2).
Fig. 3 demonstrates the distribution of umbilical cord nodes in both groups.
As follows from Fig. 3, nodes of the umbilical cord were detected somewhat more often in the main group (53%) than in the control group (36%) (p>0.05;χ 2 =0.21).

Валдошова СШ Морфология плаценты при туберкулёзе
The median thickness of the placenta in the main group was 2.0 cm, and in the control group -3.0 cm, but the difference was not statistically significant (p>0.05).Placenta volume measurements are shown in Fig. 4. In the main group, it was insignificantly reduced compared to the control group (p>0.05;U=42.0;Z=-1.68).
Evaluation of villous maturity showed that in 46.7% of placentas in the main group immature intermediate villi dominated; while in the control group, mature intermediate villi dominated over immature in all cases.
The formation of functionally inactive synticial nodules (67% in the main group vs. 45% in the control group, p>0.05), placental circulatory disorders (ischemic necrosis, fibrinoid thrombi in the intervillous space) were indicators of chronic PI (Fig. 5).
Table 1 presents data on the prevalence of degenerative and dystrophic changes in the placentas of postpartum women in both groups.As follows from Table 1, all parameters were insignificantly more frequent in the main group than in the control one (p>0.05).
Fatty degeneration was observed in 13% of cases in the main group and was absent in the control group.
Table 2 presents data on placental circulatory disorders in the studied groups.
As follows from Table 2, all indicators of placental circulatory disorders were more common in the main group.However, only the detection rate of infarctions in the stroma of the villi was statistically significantly higher in the main group (p<0.05).
Hyperplasia of the terminal villi, as a compensatory reaction, was more frequently observed in the control group.On the other hand, the resulting hyperplasia of the terminal villi leads to a narrowing of the intervillous space, which causes placental circulatory disorders [20].
Hypervascularization of the villi and the formation of functionally active syncytial nodules contributed to the compensation of chronic PI, which was more pronounced in the control group (55% vs. 33%, p>0.05; χ 2 =0.46).

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of the main group than in the control one (86% vs. 20%, p=0.045; χ 2 =5.18).Fig. 8 shows a microphotograph of the placenta with a subcompensated form of PI.
As can be seen on Fig. 8, intermediate differentiated immature villi, hemorrhages in the intervillous space, foci of necrosis (infarctions), chorionic villi embedded in fibrin, and vascular plethora are seen on this micrograph of the placenta in the main group.
Scarce Kashchenko-Hofbauer cells, or synticial macrophages of the villous chorion (Fig. 9), were present in the placentas of both groups, while they formed clusters in one of the placentas in the main group.
It should be noted that Kashchenko-Hoffbauer cells provide immune defense associated with the antigen-presenting function [9].
Histological examination did not reveal specific TB granulomas in any placenta of the main group, in contrast to the described cases [25].Signs of inflammation of the decidual tissue in the form of focal infiltration by segmented neutrophils were found in 27% of cases in the main group, versus 9% in the control group (p>0.05;χ 2 =0.04) (Fig. 10).

Литература
Valdoshova SSh Morphology of the placenta in tuberculosis and volume, degenerative and dystrophic lesions, and circulatory disorders, contributed to the development of more pronounced forms of PI.Chronic PI was diagnosed in all patients of the main group and in most women in the control group, however, its decompensated form was observed statistically significantly more often in patients with TB.Hypervascularization of the villi, the formation of functionally active synticial nodules and synticiocapillary membranes, and angiomatosis were a defense reaction, but it was not able to fully sustain blood supply and compensate for the manifestations of PI, which ultimately led to worse perinatal outcomes (IUGR, a decrease in the size of the body of newborns).