The expression and potential functions of placental myostatin

TGFβ signalling: a nexus between inflammation, placental health and preeclampsia throughout pregnancy

BACKGROUND

The placenta is a unique and pivotal organ in reproduction, controlling crucial growth and cell differentiation processes that ensure a successful pregnancy. Placental development is a tightly regulated and dynamic process, in which the transforming growth factor beta (TGFβ) superfamily plays a central role. This family of pleiotropic growth factors is heavily involved in regulating various aspects of reproductive biology, particularly in trophoblast differentiation during the first trimester of pregnancy. TGFβ signalling precisely regulates trophoblast invasion and the cell transition from cytotrophoblasts to extravillous trophoblasts, which is an epithelial-to-mesenchymal transition-like process. Later in pregnancy, TGFβ signalling ensures proper vascularization and angiogenesis in placental endothelial cells. Beyond its role in trophoblasts and endothelial cells, TGFβ signalling contributes to the polarization and function of placental and decidual macrophages by promoting maternal tolerance of the semi-allogeneic foetus. Disturbances in early placental development have been associated with several pregnancy complications, including preeclampsia (PE) which is one of the severe complications. Emerging evidence suggests that TGFβ is involved in the pathogenesis of PE, thereby offering a potential target for intervention in the human placenta.

OBJECTIVE AND RATIONALE

This comprehensive review aims to explore and elucidate the roles of the major members of the TGFβ superfamily, including TGFβs, bone morphogenetic proteins (BMPs), activins, inhibins, nodals, and growth differentiation factors (GDFs), in the context of placental development and function. The review focusses on their interactions within the major cell types of the placenta, namely trophoblasts, endothelial cells, and immune cells, in both normal pregnancies and pregnancies complicated by PE throughout pregnancy.

SEARCH METHODS

A literature search was carried out using PubMed and Google Scholar, searching terms: 'TGF signalling preeclampsia', 'pregnancy TGF signalling', 'preeclampsia tgfβ', 'preeclampsia bmp', 'preeclampsia gdf', 'preeclampsia activin', 'endoglin preeclampsia', 'endoglin pregnancy', 'tgfβ signalling pregnancy', 'bmp signalling pregnancy', 'gdf signalling pregnancy', 'activin signalling pregnancy', 'Hofbauer cell tgfβ signalling', 'placental macrophages tgfβ', 'endothelial cells tgfβ', 'endothelium tgfβ signalling', 'trophoblast invasion tgfβ signalling', 'trophoblast invasion Smad', 'trophoblast invasion bmp', 'trophoblast invasion tgfβ', 'tgfβ preeclampsia', 'tgfβ placental development', 'TGFβ placental function', 'endothelial dysfunction preeclampsia tgfβ signalling', 'vascular remodelling placenta TGFβ', 'inflammation pregnancy tgfβ', 'immune response pregnancy tgfβ', 'immune tolerance pregnancy tgfβ', 'TGFβ pregnancy NK cells', 'bmp pregnancy NK cells', 'bmp pregnancy tregs', 'tgfβ pregnancy tregs', 'TGFβ placenta NK cells', 'TGFβ placenta tregs', 'NK cells preeclampsia', 'Tregs preeclampsia'. Only articles published in English until 2023 were used.

OUTCOMES

A comprehensive understanding of TGFβ signalling and its role in regulating interconnected cell functions of the main placental cell types provides valuable insights into the processes essential for successful placental development and growth of the foetus during pregnancy. By orchestrating trophoblast invasion, vascularization, immune tolerance, and tissue remodelling, TGFβ ligands contribute to the proper functioning of a healthy maternal-foetal interface. However, dysregulation of TGFβ signalling has been implicated in the pathogenesis of PE, where the shallow trophoblast invasion, defective vascular remodelling, decreased uteroplacental perfusion, and endothelial cell and immune dysfunction observed in PE, are all affected by an altered TGFβ signalling.

WIDER IMPLICATIONS

The dysregulation of TGFβ signalling in PE has important implications for research and clinical practice. Further investigation is required to understand the underlying mechanisms, including the role of different ligands and their regulation under pathophysiological conditions, in order to discover new therapeutic targets. Distinguishing between clinically manifested subtypes of PE and studying TGFβ signalling in different placental cell types holistically is an important first step. To put this knowledge into practice, pre-clinical animal models combined with new technologies are needed. This may also lead to improved human research models and identify potential therapeutic targets, ultimately improving outcomes for affected pregnancies and reducing the burden of PE.

GDF-8 improves in vitro implantation and cryo-tolerance by stimulating the ALK5-SMAD2/3 signaling in bovine IVF embryo development

Transforming growth factor-beta (TGF-β) plays a critical role in regulating trophoblast invasion and proliferation. Growth differentiation factor-8 (GDF-8) is a member of the TGF-β superfamily and is categorized as a myostatin subtype. It is primarily a secreted protein synthesized in skeletal muscle cells. It is expressed in the placenta, reproductive tissues, and cells. In this study, we investigated the role of GDF-8 in the development and hatching rate of bovine embryos. We noted a notable elevation (p < 0.05) in the development and hatching rates compared to the control embryos. Furthermore, the GDF-8 group showed a significantly improved total cell number (p < 0.05) and an increase in trophectoderm ratio inner cell mass (trophectoderm: inner cell mass) cells (p < 0.001) compared to the control group. Additionally, blastocysts treated with GDF-8 exhibited significantly higher mRNA levels of caudal-type homeobox 2 (CDX2) (p < 0.05). The trophoblast invasion area was significantly larger in the GDF-8 group than in the control group (p < 0.01). Furthermore, qRT-PCR analysis revealed significantly higher mRNA levels (p < 0.05) of matrix metalloproteinases 9 (MMP9) and follistatin-like 3(FSTL3), both of which are associated with the ALK5-SMAD2/3 signaling pathway, in the GDF-8 group than those in the control group. The mRNA expression levels of genes related to tight junctions (TJ) and adherent junctions were higher in the GDF-8 group than those in the control group (p < 0.05). After 24 h of thawing, blastocysts were analyzed using 4-kDa FITC-dextran, which revealed a higher TJ integrity in the GDF-8 group (p < 0.01). Thus, GDF-8 plays a crucial role in bovine embryonic development, in vitro implantation, and cryotolerance.

Roles of bone morphogenetic proteins in endometrial remodeling during the human menstrual cycle and pregnancy

BACKGROUND

During the human menstrual cycle and pregnancy, the endometrium undergoes a series of dynamic remodeling processes to adapt to physiological changes. Insufficient endometrial remodeling, characterized by inadequate endometrial proliferation, decidualization and spiral artery remodeling, is associated with infertility, endometriosis, dysfunctional uterine bleeding, and pregnancy-related complications such as preeclampsia and miscarriage. Bone morphogenetic proteins (BMPs), a subset of the transforming growth factor-β (TGF-β) superfamily, are multifunctional cytokines that regulate diverse cellular activities, such as differentiation, proliferation, apoptosis, and extracellular matrix synthesis, are now understood as integral to multiple reproductive processes in women. Investigations using human biological samples have shown that BMPs are essential for regulating human endometrial remodeling processes, including endometrial proliferation and decidualization.

OBJECTIVE AND RATIONALE

This review summarizes our current knowledge on the known pathophysiological roles of BMPs and their underlying molecular mechanisms in regulating human endometrial proliferation and decidualization, with the goal of promoting the development of innovative strategies for diagnosing, treating and preventing infertility and adverse pregnancy complications associated with dysregulated human endometrial remodeling.

SEARCH METHODS

A literature search for original articles published up to June 2023 was conducted in the PubMed, MEDLINE, and Google Scholar databases, identifying studies on the roles of BMPs in endometrial remodeling during the human menstrual cycle and pregnancy. Articles identified were restricted to English language full-text papers.

OUTCOMES

BMP ligands and receptors and their transduction molecules are expressed in the endometrium and at the maternal-fetal interface. Along with emerging technologies such as tissue microarrays, 3D organoid cultures and advanced single-cell transcriptomics, and given the clinical availability of recombinant human proteins and ongoing pharmaceutical development, it is now clear that BMPs exert multiple roles in regulating human endometrial remodeling and that these biomolecules (and their receptors) can be targeted for diagnostic and therapeutic purposes. Moreover, dysregulation of these ligands, their receptors, or signaling determinants can impact endometrial remodeling, contributing to infertility or pregnancy-related complications (e.g. preeclampsia and miscarriage).

WIDER IMPLICATIONS

Although further clinical trials are needed, recent advancements in the development of recombinant BMP ligands, synthetic BMP inhibitors, receptor antagonists, BMP ligand sequestration tools, and gene therapies have underscored the BMPs as candidate diagnostic biomarkers and positioned the BMP signaling pathway as a promising therapeutic target for addressing infertility and pregnancy complications related to dysregulated human endometrial remodeling.

Snail mediates GDF-8-stimulated human extravillous trophoblast cell invasion by upregulating MMP2 expression

BACKGROUND

Extravillous trophoblast (EVT) cell invasion is a tightly regulated process that requires for a normal pregnancy. The epithelial-mesenchymal transition (EMT) has been implicated in EVT cell invasion. Growth differentiation factor-8 (GDF-8), a member of the transforming growth factor-beta (TGF-β) superfamily, is expressed in the human placenta and promotes EVT cell invasion by upregulating the expression of matrix metalloproteinase 2 (MMP2). However, the underlying molecular mechanism of GDF-8-induced MMP2 expression remains undetermined. Therefore, the present study aims to examine the role of Snail and Slug, the EMT-related transcriptional regulators, in GDF-8-stimulated MMP2 expression and cell invasion in HTR-8/SVneo human EVT cell line and primary cultures of human EVT cells.

METHODS

HTR-8/SVneo and primary cultures of human EVT cells were used to examine the effect of GDF-8 on MMP2 expression and explore the underlying mechanism. For gene silencing and overexpression, the HTR-8/SVneo cell line was used to make the experiments more technically feasible. The cell invasiveness was measured by Matrigel-coated transwell invasion assay.

RESULTS

GDF-8 stimulated MMP2 expression in both HTR-8/SVneo and primary EVT cells. The stimulatory effect of GDF-8 on MMP2 expression was blocked by the inhibitor of TGF-β type-I receptors, SB431542. Treatment with GDF-8 upregulated Snail and Slug expression in both HTR-8/SVneo and primary EVT cells. The stimulatory effects of GDF-8 on Snail and Slug expression were blocked by pretreatment of SB431542 and siRNA-mediated knockdown of SMAD4. Interestingly, using the siRNA knockdown approach, our results showed that Snail but not Slug was required for the GDF-8-induced MMP2 expression and cell invasion in HTR-8/SVneo cells. The reduction of MMP2 expression in the placentas with preeclampsia (PE) was also observed.

CONCLUSIONS

These findings discover the physiological function of GDF-8 in the human placenta and provide important insights into the regulation of MMP2 expression in human EVT cells. Video Abstract.

Myostatin: a multifunctional role in human female reproduction and fertility - a short review

Myostatin (MSTN) is member of the transforming growth factor β (TGF-β) superfamily and was originally identified in the musculoskeletal system as a negative regulator of skeletal muscle growth. The functional roles of MSTN outside of the musculoskeletal system have aroused researchers' interest in recent years, with an increasing number of studies being conducted in this area. Notably, the expression of MSTN and its potential activities in various reproductive organs, including the ovary, placenta, and uterus, have recently been examined. Numerous studies published in the last few years demonstrate that MSTN plays a critical role in human reproduction and fertility, including the regulation of follicular development, ovarian steroidogenesis, granule-cell proliferation, and oocyte maturation regulation. Furthermore, findings from clinical samples suggest that MSTN may play a key role in the pathogenesis of several reproductive disorders such as uterine myoma, preeclampsia (PE), ovary hyperstimulation syndrome (OHSS), and polycystic ovarian syndrome (PCOS). There is no comprehensive review regarding to MSTN related to the female reproductive system in the literature. This review serves as a summary of the genes in reproductive medicine and their potential influence. We summarized MSTN expression in different compartments of the female reproductive system. Subsequently, we discuss the role of MSTN in both physiological and several pathological conditions related to the female fertility and reproduction-related diseases.

Enhanced Muscle Fibers of Epinephelus coioides by Myostatin Autologous Nucleic Acid Vaccine

Epinephelus coioides is a fish species with high economic value due to its delicious meat, high protein content, and rich fatty acid nutrition. It has become a high-economic fish in southern parts of China and some other Southeast Asian countries. In this study, the myostatin nucleic acid vaccine was constructed and used to immunize E. coioides. The results from body length and weight measurements indicated the myostatin nucleic acid vaccine promoted E. coioides growth performance by increasing muscle fiber size. The results from RT-qPCR analysis showed that myostatin nucleic acid vaccine upregulated the expression of myod, myog and p21 mRNA, downregulated the expression of smad3 and mrf4 mRNA. This preliminary study is the first report that explored the role of myostatin in E. coioides and showed positive effects of autologous nucleic acid vaccine on the muscle growth of E. coioides. Further experiments with increased numbers of animals and different doses are needed for its application to E. coiodes aquaculture production.

Myostatin increases human trophoblast cell invasion by upregulating N-cadherin via SMAD2/3-SMAD4 Signaling

Placental insufficiency disorders are major obstetric complications that share a common phenomenon of poor placental trophoblast cell invasion and remodeling of uterine tissues. Myostatin is a transforming growth factor (TGF)-β superfamily member well-known for its important role in muscle growth control. Myostatin is also produced in the placenta and has been shown to regulate some trophoblast functions. However, its roles in placental development are still poorly understood. In this study, we tested the hypothesis that myostatin increases trophoblast cell invasion by upregulating N-cadherin via SMAD2/3-SMAD4 signaling. Primary and immortalized (HTR8/SVneo) trophoblast cells were used as study models. Matrigel-coated transwell invasion assays were used to study the effects of recombinant human myostatin on trophoblast cell invasion. RT-qPCR and Western blot were used to measure myostatin effects on N-cadherin mRNA and protein levels, respectively. Small inhibitor molecules as well as siRNA-mediated knockdown were used to block myostatin receptor and downstream signaling, respectively. Data were analyzed either by unpaired Student T test or one-way ANOVA followed by Newman Keuls test for multiple group comparisons. Myostatin significantly increased primary and HTR8/SVneo trophoblast cell invasion. Moreover, myostatin upregulated N-cadherin mRNA and protein levels in a time dependent manner in both study models. These effects were blocked by inhibition of TGF-β type I receptors as well as siRNA-mediated knockdown of SMAD2/3 combined or common SMAD4. Importantly, myostatin-induced trophoblast cell invasion was abolished by knockdown of N-cadherin, SMAD2/3 or SMAD4. Myostatin may increase human trophoblast cell invasion by upregulating N-cadherin via SMAD2/3-SMAD4 signaling.

Regulatory Role and Potential Importance of GDF-8 in Ovarian Reproductive Activity

Growth differentiation factor-8 (GDF-8) is a member of the transforming growth factor-beta superfamily. Studies in vitro and in vivo have shown GDF-8 to be involved in the physiology and pathology of ovarian reproductive functions. In vitro experiments using a granulosa-cell model have demonstrated steroidogenesis, gonadotrophin responsiveness, glucose metabolism, cell proliferation as well as expression of lysyl oxidase and pentraxin 3 to be regulated by GDF-8 via the mothers against decapentaplegic homolog signaling pathway. Clinical data have shown that GDF-8 is expressed widely in the human ovary and has high expression in serum of obese women with polycystic ovary syndrome. GDF-8 expression in serum changes dynamically in patients undergoing controlled ovarian hyperstimulation. GDF-8 expression in serum and follicular fluid is correlated with the ovarian response and pregnancy outcome during in vitro fertilization. Blocking the GDF-8 signaling pathway is a potential therapeutic for ovarian hyperstimulation syndrome and ovulation disorders in polycystic ovary syndrome. GDF-8 has a regulatory role and potential importance in ovarian reproductive activity and may be involved in folliculogenesis, ovulation, and early embryo implantation.

Placental Transcriptome Adaptations to Maternal Nutrient Restriction in Sheep

Placental development is modified in response to maternal nutrient restriction (NR), resulting in a spectrum of fetal growth rates. Pregnant sheep carrying singleton fetuses and fed either 100% (n = 8) or 50% (NR; n = 28) of their National Research Council (NRC) recommended intake from days 35–135 of pregnancy were used to elucidate placentome transcriptome alterations at both day 70 and day 135. NR fetuses were further designated into upper (NR NonSGA; n = 7) and lower quartiles (NR SGA; n = 7) based on day 135 fetal weight. At day 70 of pregnancy, there were 22 genes dysregulated between NR SGA and 100% NRC placentomes, 27 genes between NR NonSGA and 100% NRC placentomes, and 22 genes between NR SGA and NR NonSGA placentomes. These genes mediated molecular functions such as MHC class II protein binding, signaling receptor binding, and cytokine activity. Gene set enrichment analysis (GSEA) revealed significant overrepresentation of genes for natural-killer-cell-mediated cytotoxicity in NR SGA compared to 100% NRC placentomes, and alterations in nutrient utilization pathways between NR SGA and NR NonSGA placentomes at day 70. Results identify novel factors associated with impaired function in SGA placentomes and potential for placentomes from NR NonSGA pregnancies to adapt to nutritional hardship.

Roles of TGF-β Superfamily Proteins in Extravillous Trophoblast Invasion

Following embryo implantation, extravillous trophoblasts (EVTs) invade the maternal decidua to a certain extent during early pregnancy, which is critical for normal placentation and successful pregnancy in humans. Although sharing a similar protein structure, the transforming growth factor-β (TGF-β) superfamily members exert divergent functions in regulating EVT invasion, which contributes to a relative balance of TGF-β superfamily proteins in precisely modulating this process at the maternal-fetal interface during the first trimester of pregnancy. This review details recent advances in our understanding of the functions of TGF-β superfamily members and their corresponding receptors, signaling pathways, and downstream molecular targets in regulating human EVT invasion from studies using various in vitro or ex vivo experimental models. Also, the relevance of these discoveries about TGF-β superfamily members to adverse pregnancy outcomes is summarized. The application of 3D culture trophoblast organoids, single-cell sequencing, and microfluidic assays in EVT invasion studies will help better reveal the molecular mechanisms through which TGF-β superfamily members regulate human EVT invasion, shedding light on the development of innovative strategies for predicting, diagnosing, treating, and preventing adverse human pregnancy outcomes related to EVT invasion dysfunction.

GDF8 Promotes the Cell Invasiveness in Human Trophoblasts by Upregulating the Expression of Follistatin-Like 3 Through the ALK5-SMAD2/3 Signaling Pathway

Growth differentiation factor 8 (GDF8) and its antagonist follistatin-like 3 (FSTL3) are expressed in the placenta during early pregnancy. These two factors may have a role to play in the regulation of normal placentation. However, whether GDF8 can regulate the expression of FSTL3 in human trophoblasts remains to be elucidated. In this study, we aimed to investigate the effects of GDF8 on the expression of FSTL3 and the underlying molecular mechanisms using human trophoblasts as a study model. Our results showed that GDF8 significantly upregulates the expression and production of FSTL3, which further promotes cell invasiveness in immortalized extravillous cytotrophoblast cells and primary extravillous cytotrophoblast cells obtained from human first-trimester placentae. Additionally, using an siRNA-mediated knockdown approach, we found that this regulatory effect is most likely mediated by the ALK5-Sma- and Mad-related protein (SMAD)2/3-induced signaling pathway. These findings deepen our understanding of the functional roles of GDF8 and FSTL3 in the regulation of cell invasiveness of trophoblasts.

Molecular characterization, expression analysis of myostatin gene and its negative regulation by miR-29b-3p in Chinese concave-eared frogs (Odorrana tormota)

The molecular characteristics, expression patterns and functions of the amphibian myostatin (MSTN) gene are unknown. Here, we isolated a full-length Odorrana tormota MSTN cDNA sequence of 1701 bp (Ot-MSTN), containing a putative N-terminal signal peptide, a TGF-β propeptide domain and an active peptide. Ot-MSTN was expressed in 9 selected tissues examined, and the highest level of expression was in thigh muscle, followed by brain and female gonadal tissue. The expression of Ot-MSTN in multiple O. tormota tissues supported that the activities of MSTN may be not limited to skeletal muscle. Ot-MSTN expression was decreased from stage 31 to stage 40, while the growth rate was increased. The expression of Ot-MSTN in adult male frogs increased with age, indicating that adult male frogs may inhibit the continued hypertrophy of thigh muscle fibers and decrease the growth rate of thigh muscle to ensure muscles do not grow too large. Luciferase reporter assays showed that miR-29b-3p directly targeted the 3'-UTR of Ot-MSTN. miR-29b-3p expression in the thigh muscle of 2 yrs. females who grew faster was significantly lower than that of the slow-growing 2 yrs. male individuals, which showed an opposite trend with Ot-MSTN expression. In addition，miR-29b-3p expression reversed trends of Ot-MSTN expression at different developmental stages in thigh muscle. Therefore, these data indicate that miR-29-3p may negatively regulate the expression of MSTN and regulate thigh muscle growth and development in O. tormota.

Molecular Cloning, Identification, and Expression Patterns of Myostatin Gene in Water Buffalo (Bubalus Bubalis)

Myostatin (MSTN), also named growth differentiation factor 8 (GDF8), is a transforming growth factor-β (TGF-β) family member with a key role in the negative regulation of skeletal muscle growth. However, its role in ovarian folliculogenesis remains unclear. To provide us with a basis for understanding this role, we cloned MSTN and examined its expression patterns in water buffalo (Bubalus bubalis). The complete ORF of the water buffalo MSTN gene is 1,128 nucleotides, which encode a 375 amino acid protein and sharing 99% identity at the deducted amino acid level with that of Bos taurus. Protein sequence analysis showed that MSTN is a weakly acerbic extracellular protein, consisting of signal peptides at 18-19 sites, a TGF-β propeptide, and a TGF-β domain. RT-PCR analyses demonstrated that water buffalo MSTN was expressed in multiple tissues but not limited to muscle. Immunohistochemistry staining confirmed the presence of MSTN in oocytes and granulosal cells. To our knowledge, this is the first study to confirm the expression of MSTN in the water buffalo ovary, suggesting an additional role of MSTN in water buffalo folliculogenesis, along with its role in skeletal muscle growth regulation. Further study of the regulatory mechanism of MSTN in water buffalo reproduction is warranted.

ABBREVIATIONS

MSTN, myostatin; ORF, open reading frame.

Expression of Myostatin in Intrauterine Growth Restriction and Preeclampsia Complicated Pregnancies and Alterations to Cytokine Production by First-Trimester Placental Explants Following Myostatin Treatment

Preeclampsia (PE) and intrauterine growth restriction (IUGR) are major obstetric health problems. Higher levels of T-helper (Th) 1 (proinflammatory) cytokines have been observed in pregnancies complicated with PE and IUGR; this is in contrast to the predominant Th2 (anti-inflammatory) cytokine environment found in uncomplicated pregnancies. Myostatin is best known as a negative regulator of muscle development and reportedly has a role in fat deposition, glucose metabolism, and cytokine modulation (outside the placenta). Myostatin concentrations in plasma and protein expression in placental tissue are significantly higher in women with PE. Expression of myostatin in IUGR and PE-IUGR and the effect of this protein on the cytokine production from the placenta is unknown. In the current study, significant differences were identified in the expression of myostatin in pregnancies complicated with IUGR, PE, and PE with IUGR. Furthermore, cytokine production by first-trimester placental tissues was altered following myostatin treatment.

Myostatin in the placentae of pregnancies complicated with gestational diabetes mellitus

INTRODUCTION

Gestational diabetes mellitus (GDM) is characterised by maternal glucose intolerance and insulin resistance during pregnancy. Myostatin, initially identified as a negative regulator of muscle development may also function in the regulation of placental development and glucose uptake. Myostatin expression in placentae of GDM complicated pregnancies is unknown. However, higher myostatin levels occur in placentae of pregnancies complicated with preeclampsia. We hypothesise that myostatin will be differentially expressed in GDM complicated pregnancies.

METHODS

Myostatin concentrations (ELISA) were evaluated in plasma of presymptomatic women who later developed GDM and compared to plasma of normal glucose tolerant (NGT) women. Furthermore, myostatin protein expression (Western blot) was studied in placentae of pregnant women with GDM (treated with diet or insulin) compared to placentae of NGT women.

RESULTS

No significant difference in myostatin concentration was seen in plasma of pre-symptomatic GDM women compared to NGT women. In placenta significant differences in myostatin protein expressions (higher precursor; p < 0.05and lower dimer: p < 0.005) were observed in GDM complicated compared to NGT pregnancies. Furthermore, placentae of GDM women treated with insulin compared to diet have higher dimer (p < 0.005) and lower precursor (p < 0.05). Compared to lean women, placentae of obese NGT women were lower in myostatin dimer expression (p < 0.05).

DISCUSSION

Myostatin expression in placental tissue is altered under stress conditions (e.g. obesity and abnormal glucose metabolism) found in pregnancies complicated with GDM. We hypothesise that myostatin is active in these placentae and could affect glucose homoeostasis and/or cytokine production thereby altering the function of the placenta.