Telomeres and replicative cellular aging of the human placenta and chorioamniotic membranes

Abstract

Recent hypotheses propose that the human placenta and chorioamniotic membranes (CAMs) experience telomere length (TL)-mediated senescence. These hypotheses are based on mean TL (mTL) measurements, but replicative senescence is triggered by short and dysfunctional telomeres, not mTL. We measured short telomeres by a vanguard method, the Telomere shortest length assay, and telomere-dysfunction-induced DNA damage foci (TIF) in placentas and CAMs between 18-week gestation and at full-term. Both the placenta and CAMs showed a buildup of short telomeres and TIFs, but not shortening of mTL from 18-weeks to full-term. In the placenta, TIFs correlated with short telomeres but not mTL. CAMs of preterm birth pregnancies with intra-amniotic infection showed shorter mTL and increased proportions of short telomeres. We conclude that the placenta and probably the CAMs undergo TL-mediated replicative aging. Further research is warranted whether TL-mediated replicative aging plays a role in all preterm births.

Figure 1

Mean telomere length (kb) in different tissues at full-term, measured using Southern blotting (SBmTL) and TeSLA (TeSmTL). Grey lines connect measurements on different tissues of the same mother–offspring pair (n = 13), markers show average ± SE. samples: maternal blood (MB), umbilical cord blood (UCB), amniotic membrane (AM), chorionic membrane (CM), Placenta.

Figure 2

Proportion of cells with telomere dysfunction induced foci (TIF) at 18-weeks of gestation (n = 10) and at term (n = 18), in the placenta and the chorioamniotic membranes (CAMs). Note that at 18 weeks the CAMs could not be separated and hence the measurements are for the chorionic membrane (CM) and amniotic membrane (AM) combined, i.e., CAMs. Lines connect measurements in different tissues from the same donor, and dots show means ± SE.

Figure 3

Telomere length in the placenta at 18-weeks of gestation (n = 10) and at full term (n = 22). Southern blot mean telomere length (SBmTL) (a); TeSLA mean telomere length (TeSmTL) (b); proportion of telomeres shorter than 3.0 kb (TeSLA measurements) (c). NS, not significant; ***P < 0.001.

Figure 4

Telomere length in the chorioamniotic membranes (CAMs) at 18-weeks of gestation (n = 10) and at full term (n = 13). Southern blot mean telomere length (SBmTL) (a); TeSLA mean telomere length (TeSmTL) (b); proportion of telomeres shorter than 3.0 kb (TeSLA measurements) (c). Note that at 18 weeks the measurements are for the chorionic membrane (CM) and amniotic membrane (AM) combined, i.e., CAMs, since the two could not be separated. At term the two membranes could be separated (AM, squares; CM, circles), but boxplot is for the membranes pooled. *P < 0.05; **P < 0.01; ***P < 0.001.

Figure 5

Correlation between telomere dysfunction induced foci (TIF) and TeSLA mTL (TeSmTL). Placenta (a); chorioamniotic membranes (CAMs) (b). For both panels (a) and (b) open data symbols: samples at 18-week gestation, filled data symbols: samples at term. For panel (b), chorionic membrane (CM, black circles), amniotic membrane (AM, black squares). For panel (a) correlation (R² = 0.52, n = 20, P < 0.001) between TeSmTL and proportion of TIF, and P = 0.41 (n = 27) for panel (b).

Figure 6

Mean telomere length by Southern blotting (SBmTL) and by the TeSLA (TeSmTL) for different pregnancy outcomes in the placenta (a) and the chorioamniotic membranes (CAMs) (b). Pregnancy outcomes (Groups): small for gestational age (SGA), pre-term birth (PTB), pre-term birth with intra-amniotic infection (PTBI). *P < 0.05; ***P < 0.001. n = 9 for each group.