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

Evaluation of maternal serum fibroblast growth factor-23 levels in fetal growth restriction and gestational hypertensive disease

OBJECTIVE

The objective of this study was to determine serum fibroblast growth factor-23 levels in preeclampsia, eclampsia, gestational hypertension, and the presence of fetal growth restriction subgroups.

METHODS

A total of 55 pregnant women with planned cesarean section were included in this cross-sectional study. They were divided into two groups, namely, control (25) and gestational hypertensive disease (30). The gestational hypertensive disease group was evaluated by dividing it into three subgroups (preeclampsia, eclampsia, and gestational hypertension) according to the clinical and laboratory findings of the disease and two subgroups (presence of fetal growth restriction and absence of fetal growth restriction) according to the birth weight percentile. Demographic parameters, obstetric history, physical examination findings, and laboratory values were evaluated.

RESULTS

Demographic parameters and obstetric history were similar between the two groups, while gestational week of delivery was lower in the gestational hypertensive disease group (p=0.002). Laboratory parameters and serum fibroblast growth factor-23 (pg/mL) values were similar between the two groups. In the subgroup analysis for gestational hypertension, preeclampsia, and eclampsia, there was no statistically significant difference in serum fibroblast growth factor-23 levels between gestational hypertension, preeclampsia, eclampsia, and control groups. In the subgroup analysis based on the presence of fetal growth restriction, serum fibroblast growth factor-23 levels were similar to the control group in the gestational hypertensive disease absence of fetal growth restriction, while serum fibroblast growth factor-23 levels and serum calcium levels were statistically significantly lower in the gestational hypertensive disease with the presence of fetal growth restriction (p=0.044 and p<0.001, respectively).

CONCLUSION

Serum fibroblast growth factor-23 levels are similar between pregnancies complicated with gestational hypertensive disease and normotensive pregnancies. However, serum fibroblast growth factor-23 levels were found to be lower in pregnancies complicated with gestational hypertensive disease with the presence of fetal growth restriction.

Decreased Alpha Klotho Expression in Placentas Exposed to Severe Maternal Vascular Malperfusion

BACKGROUND

Placental maternal vascular malperfusion (MVM) is characterized by accelerated villous maturation and has been associated with a decrease in the antiaging protein, alpha-klotho (AK). Our aim was to characterize AK protein and gene expression in the placenta and fetal organs.

METHODS

We utilized 2 cohorts. First, we characterized AK protein expression in an autopsy cohort where cases were defined as MVM as the cause of fetal death compared to a stillborn control population. Second, we characterized placental and umbilical cord blood AK gene expression in a liveborn population with and without MVM.

RESULTS

We found decreased protein expression in the villous trophoblastic cells of placentas exposed to severe MVM and decreased AK gene expression in placental tissue exposed to MVM. We did not see any statistically significant differences in fetal organ or umbilical cord blood AK expression based on the presence or absence of MVM. Furthermore, in liveborn infants, we also found increased odds of preterm birth with lower placental AK expression.

CONCLUSIONS

Decreased AK gene and protein expression in the placenta in the setting of MVM is consistent with the theory of placental aging in MVM and is associated with increased odds of preterm birth.

Decreased FGF23 inhibits placental angiogenesis via the ERK1/2-EGR-1 signaling pathway in preeclampsia

PURPOSE

This study aimed to investigate the expression of fibroblast growth factor 23 (FGF23) in pregnant women with preeclampsia and elucidate its role in promoting placental angiogenesis through the ERK1/2-EGR-1 signaling pathway.

METHODS

Serum FGF23 levels were measured by ELISA in healthy pregnant women and patients with preeclampsia during the first, second, and third trimesters of pregnancy. Wound healing, Transwell, and tube formation assays were performed to investigate the effects of FGF23 on cell migration, invasion and tube formation. The expression of vascular endothelial growth factor A (VEGF-A) and its upstream signaling molecules, p-ERK, and EGR-1, in placental tissues was detected by RT-qPCR and western blotting. Additionally, the effect of FGF23 on VEGF-A, p-ERK, and EGR-1 expression was further explored in vitro.

RESULTS

Serum FGF23 levels increased with gestational age. During the third trimester, the control group exhibited a more pronounced increase in FGF23 levels than the preeclampsia group. Administering exogenous FGF23 promoted trophoblast cell migration, invasion and enhanced tube formation in vascular endothelial cells. The expression levels of VEGF-A, p-ERK, and EGR-1 in the placental tissues were significantly lower in the preeclampsia group than in the control group. In vitro experiments confirmed that FGF23 up-regulated VEGF-A expression through the p-ERK/EGR-1 signaling pathway.

CONCLUSION

The serum level of FGF23 decreased in pregnant women with preeclampsia, inhibiting the ERK1/2-EGR-1 pathway and resulting in decreased expression of VEGF-A, thereby inhibiting placental angiogenesis. This could be a potential mechanism involved in the progression of preeclampsia.

Impact of Aging and Cellular Senescence in the Pathophysiology of Preeclampsia

The incidence of hypertensive disorders of pregnancy is increasing, which may be due to several factors, including an increased age at pregnancy and more comorbid health conditions during reproductive years. Preeclampsia, the most severe hypertensive disorder of pregnancy, has been associated with an increased risk of future disease, including cardiovascular and kidney diseases. Cellular senescence, the process of cell cycle arrest in response to many physiologic and maladaptive stimuli, may play an important role in the pathogenesis of preeclampsia and provide a mechanistic link to future disease. In this article, we will discuss the pathophysiology of preeclampsia, the many mechanisms of cellular senescence, evidence for the involvement of senescence in the development of preeclampsia, as well as evidence that cellular senescence may link preeclampsia to the risk of future disease. Lastly, we will explore how a better understanding of the role of cellular senescence in preeclampsia may lead to therapeutic trials. © 2023 American Physiological Society. Compr Physiol 13:5077-5114, 2023.

Association of genetically-predicted placental gene expression with adult blood pressure traits

OBJECTIVE

Blood pressure is a complex, polygenic trait, and the need to identify prehypertensive risks and new gene targets for blood pressure control therapies or prevention continues. We hypothesize a developmental origins model of blood pressure traits through the life course where the placenta is a conduit mediating genomic and nongenomic transmission of disease risk. Genetic control of placental gene expression has recently been described through expression quantitative trait loci (eQTL) studies which have identified associations with childhood phenotypes.

METHODS

We conducted a transcriptome-wide gene expression analysis estimating the predicted gene expression of placental tissue in adult individuals with genome-wide association study (GWAS) blood pressure summary statistics. We constructed predicted expression models of 15 154 genes from reference placenta eQTL data and investigated whether genetically-predicted gene expression in placental tissue is associated with blood pressure traits using published GWAS summary statistics. Functional annotation of significant genes was generated using FUMA.

RESULTS

We identified 18, 9, and 21 genes where predicted expression in placenta was significantly associated with systolic blood pressure (SBP), diastolic blood pressure (DBP), and pulse pressure (PP), respectively. There were 14 gene-tissue associations (13 unique genes) significant only in placenta.

CONCLUSIONS

In this meta-analysis using S-PrediXcan and GWAS summary statistics, the predicted expression in placenta of 48 genes was statistically significantly associated with blood pressure traits. Notable findings included the association of FGFR1 expression with increased SBP and PP. This evidence of gene expression variation in placenta preceding the onset of adult blood pressure phenotypes is an example of extreme preclinical biological changes which may benefit from intervention.

Preeclampsia and its relationship to pathological brain aging

The development of preeclampsia during pregnancy may have long-term effects on brain aging in women. Associations between preeclampsia and vascular dementia have been established, however the connection between preeclampsia and Alzheimer's disease has not been as thoroughly explored. Both preeclampsia and Alzheimer's disease have been associated with misfolded amyloid beta proteins and inflammation; due to these similarities, in this minireview, we examined the potential links between a history of preeclampsia and the development of dementia. We also discussed how hypertensive disorders of pregnancy may relate to both normal brain aging and dementia to highlight the need for additional research regarding the long-term cognitive effects of preeclampsia on the brain.

Role of ADAM and ADAMTS Disintegrin and Metalloproteinases in Normal Pregnancy and Preeclampsia

Normal pregnancy (NP) involves intricate processes starting with egg fertilization, proceeding to embryo implantation, placentation and gestation, and culminating in parturition. These pregnancy-related processes require marked uteroplacental and vascular remodeling by proteolytic enzymes and metalloproteinases. A disintegrin and metalloproteinase (ADAM) and ADAM with thrombospondin motifs (ADAMTS) are members of the zinc-dependent family of proteinases with highly conserved protein structure and sequence homology, which include a pro-domain, and a metalloproteinase, disintegrin and cysteine-rich domain. In NP, ADAMs and ADAMTS regulate sperm-egg fusion, embryo implantation, trophoblast invasion, placental angiogenesis and spiral arteries remodeling through their ectodomain proteolysis of cell surface cytokines, cadherins and growth factors as well as their adhesion with integrins and cell-cell junction proteins. Preeclampsia (PE) is a serious complication of pregnancy characterized by new-onset hypertension (HTN) in pregnancy (HTN-Preg) at or after 20 weeks of gestation, with or without proteinuria. Insufficient trophoblast invasion of the uterine wall, inadequate expansive remodeling of the spiral arteries, reduced uteroplacental perfusion pressure, and placental ischemia/hypoxia are major initiating events in the pathogenesis of PE. Placental ischemia/hypoxia increase the release of reactive oxygen species (ROS), which lead to aberrant expression/activity of certain ADAMs and ADAMTS. In PE, abnormal expression/activity of specific ADAMs and ADAMTS that function as proteolytic sheddases could alter proangiogenic and growth factors, and promote the release of antiangiogenic factors and inflammatory cytokines into the placenta and maternal circulation leading to generalized inflammation, endothelial cell injury and HTN-Preg, renal injury and proteinuria, and further decreases in uteroplacental blood flow, exaggeration of placental ischemia, and consequently fetal growth restriction. Identifying the role of ADAMs and ADAMTS in NP and PE has led to a better understanding of the underlying molecular and vascular pathways, and advanced the potential for novel biomarkers for prediction and early detection, and new approaches for the management of PE.

Orally-active, clinically-translatable senolytics restore α-Klotho in mice and humans

BACKGROUND

α-Klotho is a geroprotective protein that can attenuate or alleviate deleterious changes with ageing and disease. Declines in α-Klotho play a role in the pathophysiology of multiple diseases and age-related phenotypes. Pre-clinical evidence suggests that boosting α-Klotho holds therapeutic potential. However, readily clinically-translatable, practical strategies for increasing α-Klotho are not at hand. Here, we report that orally-active, clinically-translatable senolytics can increase α-Klotho in mice and humans.

METHODS

We examined α-Klotho expression in three different human primary cell types co-cultured with conditioned medium (CM) from senescent or non-senescent cells with or without neutralizing antibodies. We assessed α-Klotho expression in aged, obese, and senescent cell-transplanted mice treated with vehicle or senolytics. We assayed urinary α-Klotho in patients with idiopathic pulmonary fibrosis (IPF) who were treated with the senolytic drug combination, Dasatinib plus Quercetin (D+Q).

FINDINGS

We found exposure to the senescent cell secretome reduces α-Klotho in multiple nonsenescent human cell types. This was partially prevented by neutralizing antibodies against the senescence-associated secretory phenotype (SASP) factors, activin A and Interleukin 1α (IL-1α). Consistent with senescent cells' being a cause of decreased α-Klotho, transplanting senescent cells into younger mice reduced brain and urine α-Klotho. Selectively removing senescent cells genetically or pharmacologically increased α-Klotho in urine, kidney, and brain of mice with increased senescent cell burden, including naturally-aged, diet-induced obese (DIO), or senescent cell-transplanted mice. D+Q increased α-Klotho in urine of patients with IPF, a disease linked to cellular senescence.

INTERPRETATION

Senescent cells cause reduced α-Klotho, partially due to their production of activin A and IL-1α. Targeting senescent cells boosts α-Klotho in mice and humans. Thus, clearing senescent cells restores α-Klotho, potentially opening a novel, translationally-feasible avenue for developing orally-active small molecule, α-Klotho-enhancing clinical interventions. Furthermore, urinary α-Klotho may prove to be a useful test for following treatments in senolytic clinical trials.

FUNDING

This work was supported by National Institute of Health grants AG013925 (J.L.K.), AG062413 (J.L.K., S.K.), AG044271 (N.M.), AG013319 (N.M.), and the Translational Geroscience Network (AG061456: J.L.K., T.T., N.M., S.B.K., S.K.), Robert and Arlene Kogod (J.L.K.), the Connor Group (J.L.K.), Robert J. and Theresa W. Ryan (J.L.K.), and the Noaber Foundation (J.L.K.). The previous IPF clinical trial was supported by the Claude D. Pepper Older Americans Independence Centers at WFSM (AG021332: J.N.J., S.B.K.), UTHSCA (AG044271: A.M.N.), and the Translational Geroscience Network.

ADAM and ADAMTS disintegrin and metalloproteinases as major factors and molecular targets in vascular malfunction and disease

A Disintegrin and Metalloproteinase (ADAM) and A Disintegrin and Metalloproteinase with Thrombospondin Motifs (ADAMTS) are two closely related families of proteolytic enzymes. ADAMs are largely membrane-bound enzymes that act as molecular scissors or sheddases of membrane-bound proteins, growth factors, cytokines, receptors and ligands, whereas ADAMTS are mainly secreted enzymes. ADAMs have a pro-domain, and a metalloproteinase, disintegrin, cysteine-rich and transmembrane domain. Similarly, ADAMTS family members have a pro-domain, and a metalloproteinase, disintegrin, and cysteine-rich domain, but instead of a transmembrane domain they have thrombospondin motifs. Most ADAMs and ADAMTS are activated by pro-protein convertases, and can be regulated by G-protein coupled receptor agonists, Ca²⁺ ionophores and protein kinase C. Activated ADAMs and ADAMTS participate in numerous vascular processes including angiogenesis, vascular smooth muscle cell proliferation and migration, vascular cell apoptosis, cell survival, tissue repair, and wound healing. ADAMs and ADAMTS also play a role in vascular malfunction and cardiovascular diseases such as hypertension, atherosclerosis, coronary artery disease, myocardial infarction, heart failure, peripheral artery disease, and vascular aneurysm. Decreased ADAMTS13 is involved in thrombotic thrombocytopenic purpura and microangiopathies. The activity of ADAMs and ADAMTS can be regulated by endogenous tissue inhibitors of metalloproteinases and other synthetic small molecule inhibitors. ADAMs and ADAMTS can be used as diagnostic biomarkers and molecular targets in cardiovascular disease, and modulators of ADAMs and ADAMTS activity may provide potential new approaches for the management of cardiovascular disorders.

Phosphate, Calcium, and Vitamin D: Key Regulators of Fetal and Placental Development in Mammals

Normal calcium and bone homeostasis in the adult is virtually fully explained by the interactions of several key regulatory hormones, including parathyroid hormone, 1,25 dihydroxy vitamin D3, fibroblast growth factor-23, calcitonin, and sex steroids (estradiol and testosterone). In utero, bone and mineral metabolism is regulated differently from the adult. During development, it is the placenta and not the fetal kidneys, intestines, or skeleton that is the primary source of minerals for the fetus. The placenta is able to meet the almost inexhaustible needs of the fetus for minerals by actively driving the transport of calcium and phosphorus from the maternal circulation to the growing fetus. These fundamentally important minerals are maintained in the fetal circulation at higher concentrations than those in maternal blood. Maintenance of these inordinately higher fetal levels is necessary for the developing skeleton to accrue sufficient minerals by term. Importantly, in livestock species, prenatal mineralization of the skeleton is crucial for the high levels of offspring activity soon after birth. Calcium is required for mineralization, as well as a plethora of other physiological functions. Placental calcium and phosphate transport are regulated by several mechanisms that are discussed in this review. It is clear that phosphate and calcium metabolism is intimately interrelated and, therefore, placental transport of these minerals cannot be considered in isolation.

Advanced maternal age causes premature placental senescence and malformation via dysregulated α-Klotho expression in trophoblasts

Advanced maternal age (AMA) pregnancy is associated with higher risks of adverse perinatal outcomes, which may result from premature senescence of the placenta. α-Klotho is a well-known antiaging protein; however, its expression and effect on the placenta in AMA pregnancies have not yet been fully elucidated. The expression patterns of α-Klotho in mouse and human placentas from AMA pregnancies were determined by Western blotting and immunohistochemistry (IHC) staining. α-Klotho expression in JAR cells was manipulated to investigate its role in trophoblastic senescence, and transwell assays were performed to assess trophoblast invasion. The downstream genes regulated by α-Klotho in JAR cells were first screened by mRNA sequencing in α-Klotho-knockdown and control JAR cells and then validated. α-Klotho-deficient mice were generated by injecting klotho-interfering adenovirus (Ad-Klotho) via the tail vein on GD8.5. Ablation of α-Klotho resulted in not only a senescent phenotype and loss of invasiveness in JAR cells but also a reduction in the transcription of cell adhesion molecule (CAM) genes. Overexpression of α-Klotho significantly improved invasion but did not alter the expression of senescence biomarkers. α-Klotho-deficient mice exhibited placental malformation and, consequently, lower placental and fetal weights. In conclusion, AMA results in reduced α-Klotho expression in placental trophoblasts, therefore leading to premature senescence and loss of invasion (possibly through the downregulation of CAMs), both of which ultimately result in placental malformation and adverse perinatal outcomes.

Role of Klotho in the Development of Essential Hypertension

Klotho has antiaging properties, and serum levels decrease with physiological aging and aging-related diseases, such as hypertension, cardiovascular, and chronic kidney disease. Klotho deficiency in mice results in accelerated aging and cardiovascular injury, whereas Klotho supplementation slows down the progression of aging-related diseases. The pleiotropic functions of Klotho include, but are not limited to, inhibition of insulin/IGF-1 (insulin-like growth factor 1) and WNT (wingless-related integration site) signaling pathways, suppression of oxidative stress and aldosterone secretion, regulation of calcium-phosphate homeostasis, and modulation of autophagy with inhibition of apoptosis, fibrosis, and cell senescence. Accumulating evidence shows an interconnection between Klotho deficiency and hypertension, and Klotho gene polymorphisms are associated with hypertension in humans. In this review, we critically review the current understanding of the role of Klotho in the development of essential hypertension and the most important underlying pathways involved, such as the FGF23 (fibroblast growth factor 23)/Klotho axis, aldosterone, Wnt5a/RhoA, and SIRT1 (Sirtuin1). Based on this critical review, we suggest avenues for further research.

Novel mineral regulatory pathways in ovine pregnancy: I. phosphate, klotho signaling, and sodium-dependent phosphate transporters

Appropriate mineralization of the fetal skeleton requires an excess of phosphate in the fetus compared to the mother. However, mechanisms for placental phosphate transport are poorly understood. This study aimed to identify phosphate regulatory pathways in ovine endometria and placentae throughout gestation. Suffolk ewes were bred with fertile rams upon visual detection of estrus (Day 0). On Days 9, 12, 17, 30, 70, 90, 110, and 125 of pregnancy (n = 3-14/Day), ewes were euthanized and hysterectomized. Phosphate abundance varied across gestational days in uterine flushings, allantoic fluid, and homogenized endometria and placentae (P < 0.05). The expression of mRNAs for sodium-dependent phosphate transporters (SLC20A1 and SLC20A2) and klotho signaling mediators (FGF7, FGF21, FGF23, FGFR1-4, KL, KLB, ADAM10, and ADAM17) were quantified by qPCR. Day 17 conceptus tissue expressed SLC20A1, SLC20A2, KLB, FGF7, FGF21, FGF23, FGFR1, and FGFR2 mRNAs. Both sodium-dependent phosphate transporters and klotho signaling mediators were expressed in endometria and placentae throughout gestation. Gestational day influenced the expression of SLC20A1, ADAM10, ADAM17, FGF21, FGFR1, and FGFR3 mRNAs in both endometria and placentae (P < 0.05). Gestational day influenced endometrial expression of FGF7 (P < 0.001), and placental expression of FGF23 (P < 0.05). Immunohistochemistry confirmed that both FGF23 and KL proteins were expressed in endometria and placentae throughout gestation. The observed spatiotemporal profile of KL-FGF signaling suggests a potential role in the establishment of pregnancy and regulation of fetal growth. This study provides a platform for further mechanistic investigation into the role for KL-FGF signaling in the regulation of phosphate transport at the ovine maternal-conceptus interface.

Lower urinary α-Klotho is associated with lower angiotensin-(1-7) and higher blood pressure in young adults born preterm with very low birthweight

Early-life factors including preterm birth and VLBW increase the risk of hypertension, but the mechanisms remain poorly understood. Reductions in the anti-aging protein α-klotho are associated with hypertension, possibly due to angiotensin (Ang) II activation, but the mechanisms are incompletely understood and clinical evidence is lacking. The association of α-klotho with the alternative Ang-(1-7) pathway, which counteracts Ang II to lower BP, is undescribed. We hypothesized that lower urinary α-klotho is associated with higher BP and lower urinary Ang-(1-7) in preterm-born VLBW young adults. In a cross-sectional analysis of data from a prospective cohort of 141 preterm-born VLBW young adults, we assessed the associations among urinary α-klotho/creatinine, Ang II/creatinine, Ang-(1-7)/creatinine, Ang II/Ang-(1-7), and BP using generalized linear models adjusted for age and hypertensive pregnancy and conducted a sensitivity analysis in 32 term-born young adults. Among those born preterm, lower α-klotho/creatinine was associated with higher systolic BP (adjusted β (aβ): -2.58 mm Hg, 95% CI -4.99 to -0.17), lower Ang-(1-7)/creatinine (ln aβ: 0.1, 0.04-0.16), and higher Ang II/Ang-(1-7) (ln aβ: -0.14, -0.21 to -0.07). In term-born participants, α-klotho/creatinine was inversely associated with Ang II/creatinine (ln aβ: -0.15, -0.27 to -0.03) and Ang II/Ang-(1-7) (ln aβ: -0.15, -0.27 to -0.03). In preterm-born young adults with VLBW, lower urinary α-klotho/creatinine was associated with higher SBP, lower urinary Ang-(1-7)/creatinine, and higher urinary Ang II/Ang-(1-7). Reduced renal α-klotho expression could lead to renal Ang-(1-7) suppression as a novel mechanism for the development of hypertension among individuals born preterm with VLBW.

Cord blood alpha klotho is decreased in small for gestational age preterm infants with placental lesions of accelerated aging

BACKGROUND

Intrauterine growth restriction is often accompanied by placental vascular disease, of which histologic maternal vascular malperfusion is prominent. Maternal vascular malperfusion is characterized by accelerated villous maturation consistent with placental aging. Alpha klotho is an anti-aging protein produced by the placenta. We hypothesize that cord blood alpha klotho varies with maternal vascular malperfusion and small for gestational age infants through dysregulated angiogenesis.

METHODS

Nested case-control study of 54 preterm infants (N = 22 small for gestational age infants, 32 appropriate for gestational age infants, mean gestational age = 33.7 ± 2.7 weeks) and validation sample (N = 39) from a longitudinal birth cohort at Prentice Women's Hospital, Chicago, IL. Cord blood alpha klotho was measured via enzyme-linked immunoassay; concentrations were linked to multiplex data of cord blood angiogenic growth factors.

RESULTS

Median cord blood alpha klotho was decreased in small for gestational age infants (1200 [859, 2083] pg/mL) versus controls (3193 [1703, 3963] pg/mL; p < 0.01) and with severe maternal vascular malperfusion (1170 [760, 2645] pg/mL; P < 0.01), consistent with validation sample. Alpha klotho was decreased with maternal vascular malperfusion sublesions signifying accelerated villous maturation, including increased syncytial knots (1230 [805, 3606] pg/mL; p < 0.05) and distal villous hypoplasia (1170 [770, 3390] pg/mL; p < 0.05). Among 15 angiogenic markers, alpha klotho correlated directly with angiopoietin-2 (beta-coefficient = 2.6, p = 0.01).

CONCLUSIONS

Cord blood alpha klotho is decreased with small for gestational infants and maternal vascular malperfusion sublesions of accelerated placental villous maturation, and correlated with angiopoietin-2. Alpha klotho may play a role in vascular-mediated accelerated placental aging leading to intrauterine growth restriction.

Klotho Gene and Protein in Human Placentas According to Birth Weight and Gestational Age

Introduction: Fetal growth restriction may be the consequence of maternal, fetal, or placental factors. The insulin-like growth factors (IGFs) are major determinants of fetal growth, and are expressed in the mother, fetus and placenta in most species. Previously we reported higher placental protein content of IGF-I, IGF-IR, and AKT in small (SGA) compared with those from appropriate for gestational age (AGA) placentas. The protein Klotho, has been reported in placenta and may regulate IGF-I activity. In this study we determined Klotho gene expression and protein immunostaining in term (T-SGA y T-AGA) and preterm (PT-SGA y PT-AGA) human placentas. In addition, we assessed the effect of Klotho on the IGF-IR and AKT activation induced by IGF-I. Methods: Placentas (n = 1 17) from 32 T-SGA (birth weight (BW) = -1.74 ± 0.08 SDS), 37 T-AGA (BW = 0.12 ± 0.12 SDS), 20 PT-SGA (BW = -2.08 ± 0.14 SDS), and 28 PT-AGA (BW = -0.43 ± 0.13 SDS) newborns were collected. mRNA expression by RT-PCR in the chorionic (CP) and basal (BP) plates of the placentas, and the presence of Klotho was evaluated by immunohistochemistry (integral optical density, IOD). In addition, we developed placental explants that were incubated with IGF-I in the presence or absence of Klotho. Results: We found a lower mRNA expression and protein immunoreactivity of Klotho in the CP of SGA (term and preterm) compared with AGA placentas. We also observed a significant reduction in IGF-IR tyrosine activation induced by IGF-I 10 nM when preincubated with 2.0 nM of Klotho (2.4 ± 0.5 arbitrary units vs. 1.3 ± 0.3 AU), and similar results we observed on AKT and ERK_42/44 activation. Conclusion: We describe for the first time that Klotho mRNA and protein varies according to fetal growth and gestational age. In addition, Klotho appears to down-regulate the activation induced by IGF-I on IGF-IR and AKT, suggesting that Klotho may be regulating IGF-I activity in human placentas according to intrauterine fetal growth.

Tissue expression and source of circulating αKlotho

αKlotho (Klotho), a type I transmembrane protein and a coreceptor for Fibroblast Growth Factor-23, was initially thought to be expressed only in a limited number of tissues, most importantly the kidney, parathyroid gland and choroid plexus. Emerging data may suggest a more ubiquitous Klotho expression pattern which has prompted reevaluation of the restricted Klotho paradigm. Herein we systematically review the evidence for Klotho expression in various tissues and cell types in humans and other mammals, and discuss potential reasons behind existing conflicting data. Based on current literature and tissue expression atlases, we propose a classification of tissues into high, intermediate and low/absent Klotho expression. The functional relevance of Klotho in organs with low expression levels remain uncertain and there is currently limited data on a role for membrane-bound Klotho outside the kidney. Finally, we review the evidence for the tissue source of soluble Klotho, and conclude that the kidney is likely to be the principal source of circulating Klotho in physiology.

Protective proteins and telomere length in placentas from patients with pre-eclampsia in the last trimester of gestation

INTRODUCTION

Visfatin/nicotinamide phosphoribosyltransferase (Nampt), an enzyme involved in energy metabolism and sirtuins, SIRT1 and SIRT3, which are NAD-dependent deacetylases, are critical for cellular function. All three either regulate or are regulated by intracellular NAD+ levels and therefore available cellular energy, important for placental cell survival and successful pregnancy. This study investigates whether these protective proteins are involved in the placental pathophysiology of pre-eclampsia (PE) and if they are associated with 8-oxo-deoxyguanosine (8OHdG), a marker of oxidative damage or with placental telomere length.

METHODS

Maternal blood and placental samples were collected from 31 patients with PE and 30 controls between 31 and 40 weeks gestation. Quantitative immunohistochemistry was performed on placental specimens for visfatin/Nampt, SIRT1, SIRT3, and nuclear 8OHdG. Plasma visfatin was measured by ELISA and telomere length by Southern blot analysis of telomere restriction fragments.

RESULTS

Visfatin/Nampt and SIRT1 in syncytiotrophoblast decreased in PE compared to controls (p < 0.0001, p = 0.004 respectively). SIRT3 decreased in PE most significantly at preterm (p = 0.002). 8OHdG was only significantly lower in preterm controls compared to term controls (p = 0.01) and correlated with SIRT1 in all samples (r = 0.27). Telomere length was not different in PE and controls.

DISCUSSION

Decreased visfatin/Nampt, SIRT1 and SIRT3 in syncytiotrophoblast in PE suggests a lack of placental reserve in metabolic energy efficiency, increased inflammation, and lower resistance to environmental stressors. However, there was little effect on nuclear function, or evidence of genomic DNA damage, which would lead to cellular senescence and death.