Systemic and placental α-klotho: Effects of preeclampsia in the last trimester of gestation

Abstract

Introduction: α-klotho is an anti-aging protein, potentially important in preeclampsia (PE). Produced by kidney, brain and placenta, and by mRNA splicing is both a full-length membrane-bound and a truncated soluble protein in the circulation. The membrane-bound protein is an obligate co-receptor for fibroblast growth factor 23 (FGF23) and its action on receptor (FGFR), but ADAM proteinases also cause its shedding. The aims of this study were to investigate levels of maternal plasma, placental, and fetal membrane α-Klotho and their association with placental accelerated villous maturation (AVM) in PE. In addition, placental and membrane levels of ADAM17 and FGFR were measured in the same patients.

Methods: Maternal blood, placenta and fetal membranes from 61 women (31 with PE and 30 controls) between 32 and 40 weeks gestation were collected. Plasma α-klotho was measured by ELISA, and quantitative immunohistochemistry used for α-klotho, ADAM17 and FGFR1 in tissues. Placental AVM was histologically assessed.

Results: Maternal plasma levels of α-Klotho were higher in PE compared to controls (p = 0.01) and patients with the highest levels had significantly less AVM (p = 0.03). α-Klotho, ADAM17, and FGFR were all present in syncytiotrophoblast and cytotrophoblast of membranes. Between 32 and 40 weeks gestation, all placental levels decreased in controls respectively (p = 0.04, p = 0.004, p = 0.05), but not in PE. Fetal membrane levels were unchanged.

Discussion: Maternal plasma α-Klotho was increased in PE and its levels associated with reduced placental AVM. Changes in placental α-Klotho, ADAM17, and FGFR suggest their involvement in the pathophysiology of PE.

Keywords: Accelerated villous maturation; Hypertension; Klotho; Preeclampsia; Pregnancy.

Conflict of interest statement

Conflict of interest

All the authors have no conflict of interest.

Copyright © 2016 Elsevier Ltd. All rights reserved.

Figures

Fig. 1

α-klotho in plasma, placenta, and fetal membranes in control patients (32–40 weeks). A–C. Examples of placentas immunostained for α-klotho (A) preterm (B) term (C) negative control. α-klotho localized to the syncytiotrophoblast (ST) and cytotrophoblast (CY). D–F. Examples of fetal membranes: (D) preterm (E) term (F) negative control. α-klotho localized to the chorionic cytotrophoblast (CC) and decidua (dd) with darker staining in the chorion. G. maternal plasma α-klotho (dotted line, open circles) slightly increased with gestational age, placental α-klotho (solid line, closed triangles) significantly decreased (p = 0.04). H. Chorionic cytotrophoblast (dotted line, open circles) and decidua (solid line, closed triangles), significantly more in the chorion compared to decidua (p≤0.0001). Original magnification 400×.

Fig. 2

Maternal and placental α-klotho in PE and controls (32–40 weeks). A. maternal plasma α-klotho was significantly higher in patients with PE (p = 0.01). B. as a function of gestational age (solid line, closed triangles) showed no significant change. Controls (dotted line from Fig. 1G for comparison). C. Placental α-klotho was not significantly different in PE. D. as a function of gestational age, α-klotho failed to decline in PE (solid line, closed triangles) compared to controls (dotted line from Fig. 1G for comparison).

Fig. 3

ADAM17 in placenta and fetal membranes in PE and controls (32–40 weeks). A–C. Examples of placentas immunostained for ADAM17 from (A) preterm (B) term (C) negative control. ADAM17 localized to the syncytiotrophoblast (ST). D–F. Examples of fetal membranes from controls (D) preterm (E) term (F) negative control. ADAM17 localized predominantly to the chorionic cytotrophoblast (CC) and in some cells of decidua (dd). G. Placental ADAM17 was significantly higher in PE (p = 0.008). H. as a function of gestational age, showed a significant decrease in controls (p = 0.004; dotted line, open circles) and no decline in PE (solid line, closed triangles). Original magnification 400×.

Fig. 4

FGFR1 in placenta and fetal membranes in PE and controls (32–40 weeks). A–C. Examples of placentas immunostained for FGFR1 from controls (A) preterm (B) term (C) negative control. FGFR1 localized to the syncytiotrophoblast (ST). D–F. Examples of fetal membranes from controls (D) preterm (E) term (F) negative control. FGFR1 localized to the chorionic cytotrophoblast (CC) with light staining in decidua (dd). G. Placental FGFR1 was not significantly different from controls. H. as a function of gestational age it significantly decreased in controls (p = 0.05; dotted line, open circles) but failed to decline in PE (solid line, closed triangles). Original magnification 400×.

Fig. 5

α-Klotho and placental accelerated villous maturation (AVM). A–D show H&E stained placentas from PE consistent with AVM. A. Preterm: Low power view reveals small terminal villi (TV, green arrows) with decreased amounts of stroma, longitudinal forms (LF, black arrows), and reduced branching (100×). B. High power section highlights small tertiary villi with a single capillary or absent capillaries (arrows, 200×). C. Term: Villi are not as small or thin as in the preterm placenta, and accentuated Tenney-Parker change (TP, black arrows) can be appreciated on low power (100×). D. High power magnification highlights the accentuated syncytial knots with villous adhesion, characteristic of TP (arrows, 200×). E. Normal term control showing wider villi with normal branching (100×). F. Syncytial knotting is not accentuated (200×). G. Maternal α-klotho was significantly higher in PE when there was no AVM (p = 0.03), controls showed no significant difference. H. Placental α-klotho was not different in patients with PE or controls with or without AVM.