Telomere homeostasis in trophoblasts and in cord blood cells from pregnancies complicated with preeclampsia.

BACKGROUND: Telomeres are nucleoprotein structures, essential for chromosome stability and cell survival. Telomeres are progressively shortened with each cell division and by environmental factors. Telomere loss has been linked to age and stress-induced premature senescence. Dysfunctional telomeres tend to form aggregates, which consist of the end-to-end fusion of telomeres. Telomere elongation is carried out by telomerase, which is a specific reverse transcriptase capable of adding telomeric repeats to chromosome termini. The TERC gene encodes the RNA template of the telomerase. Another compensatory mechanism that is enhanced in response to telomere shortening and senescence is the telomere capture (TC). Telomere shortening and elevated aggregate formation have been observed in trophoblasts from pregnancies complicated with preeclampsia (PE). OBJECTIVE: We opted to study mechanisms of telomere shortening in trophoblasts from pregnancies complicated with PE and to assess telomere length and homeostasis in fetal cord blood cells from PE pregnancies. STUDY DESIGN: Placental specimens and cord blood samples from uncomplicated pregnancies and from pregnancies complicated with PE were collected. Staining with 4',6-diamidino-2-phenylindole was used to assess nuclear fragmentation: senescence-associated heterochromatin foci (SAHF). Fluorescence in situ hybridization was used to evaluate TERC gene copy number and TC. Telomere length and aggregate formation were assessed in cord blood using quantitative fluorescence in situ hybridization. Nonparametric Kruskal-Wallis and Mann-Whitney U tests were applied to test the differences between the study groups. RESULTS: Nine samples from pregnant patients with PE without intrauterine growth restriction and 14 samples from uncomplicated pregnancies that served as controls were collected. In cord blood cells, no differences were observed in telomere length, aggregate formation, TERC copy number, TC, or SAHF between PE and controls. In PE trophoblasts the percentage of cells with SAHF was higher in PE trophoblasts compared to controls (56.8 SD = 10.5% vs 35.2 SD = 10.7%, P = .028). The percentage of cells with abnormal TERC copy number was increased in PE trophoblasts compared to controls (31 ± 3.6% vs 12.97 SD = 5%, P = .004) as well as the percentage of cells with TC (27.4 SD = 9.4% vs 16 SD = 4.67%, P = .028). CONCLUSION: We suggest that telomere shortening in PE trophoblasts is linked to cellular increased senescence. Alterations in telomere homeostasis mechanisms are present in such cases. These findings support the role of telomeres in the pathogenesis of trophoblastic dysfunction in PE. The lack of telomere shortening, modified telomere homeostasis mechanisms, and increased senescence in cord blood from pregnancies complicated with PE suggests that these processes are probably restricted primarily to the placenta.

Telomere homeostasis in placentas from pregnancies with uncontrolled diabetes.

OBJECTIVE: Diabetes during pregnancy causes an intrauterine environment that influences lifetime sickness of the mother and the fetus. There is a correlation between diabetes and telomere shortening; however, very little is known about telomere homeostasis in the placenta. We aimed to study the telomerase complex in placentas and in cord blood leukocytes from patients with poorly controlled diabetes. METHODS: Biopsies from 16 third-trimester placentas and cord blood samples from pregnancies complicated with uncontrolled diabetes and from 16 gestational age-matched controls from uncomplicated pregnancies were examined. The expression of hTERT (human telomerase reverse transcriptase) was evaluated by immunohistochemistry and by RT-RCR. TERC gene copy number and telomere capture were evaluated by FISH. RESULTS: Telomerase expression was significantly lower in the diabetic placentas, both the protein (17.8 ± 2.8% cellular staining vs. 37 ± 5.32%, P = 0.012) and the mRNA levels (0.42 ± 0.03 folds, P = 0.022). Lower expression of TERC gene copy number were shown in the diabetic placentas compared to the healthy controls (1.7 ± 0.8% vs. 3.7 ± 1.6%, P = 0.035). We also detected higher percentage of cells with telomere capture among the diabetic trophoblasts compared to the healthy controls (19.8 ± 5.12% vs. 9.6 ± 3.65%, P = 0.038). Those differences were not observed in cord blood leukocytes from the same samples. CONCLUSIONS: Uncontrolled diabetes during pregnancy disrupts telomere-telomerase homeostasis in the trophoblasts. These changes may increase the risk for metabolic diseases in adulthood among offspring of pregnancies complicated by gestational diabetes mellitus as part of intrauterine programming. These variations were not observed in cord blood leukocytes, which imply different telomere homeostasis mechanisms in fetal cord blood.

Amniocytes from aneuploidy embryos have enhanced random aneuploidy and signs of senescence - can these findings be related to medical problems?

OBJECTIVES: Genomic aneuploidy is a common cause of human genetic disorders. Individuals with aneuploidy tend to develop malignancies. Recent studies correlated aneuploidy with early aging, senescence and organ dysfunction. This study investigated potential explanations for these increased risks by evaluating random aneuploidy and senescence rates in amniocytes from fetuses with aneuploidy. METHODS: The rates of random aneuploidy in amniocytes from normal pregnancies were evaluated and compared to amniocytes from fetuses with trisomies 21, 18 and 47,XXY using a FISH technique with X+Y, 9 and 18 probes. Senescence was evaluated by calculating the percentage of amniocytes with fragmented nuclei: senescence associated heterochromatin foci (SAHF), using DAPI staining. RESULTS: Significantly increased rates of cells with aneuploidy were observed in trisomies 18 and 21, and 47,XXY (p<0.001) compared to the control group for the somatic and sex chromosomes. Increased rates of amniocytes with SAHFs were observed among the trisomy samples compared to the control group. CONCLUSIONS: Higher incidence of random aneuploidy and senescence were observed in amniocytes from fetuses with trisomy. These findings might explain the greater lifetime tendency to develop malignancies and diseases related to early aging in these individuals.