Enhancing placental function – my first publication explained

Enhancing placental function  – my first publication explained

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Four years after my Masters of Research in Maternal and Fetal Health at The University of Manchester, our paper is finally published in Theranostics which means I have my first science journal publication! As other scientists will know, this is a very exciting moment in our science journey.

 

The title is “Placental Homing Peptide-microRNA Inhibitor Conjugates for Targeted Enhancement of Intrinsic Placental Growth Signaling”. What does that mean?! In simple terms, it’s all about targeting the placenta in order to enhance its function by delivering therapeutic molecules to it. Science journals can be very inaccessible to non-scientists but it is so important we relay our scientific findings to the public. I’m going to talk about why an earth we did this research, how we did it, our results and what they mean… and hopefully it all makes sense and you’ve learnt something new!

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The background…

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Many serious pregnancy complications such as pre-eclampsia (high blood pressure and protein present in the urine), fetal growth restriction (FGR; baby is smaller than average) and macrosomia (baby is larger than average) develop as a result of suboptimal growth and development of the placenta. The placenta is the interface between mother and baby for nutrient transfer.

These conditions can lead to preterm delivery which in turn can cause complications. Babies who are born too early have an increased risk of developing cardiovascular and metabolic diseases, but there are currently no treatments available during pregnancy. Administration of a drug via an injection in human pregnancy can cause dangerous side effects and disturbances to the fetus’ development (teratogenicity). We all take pain killers for headaches from time-to-time right? You just pop them into your mouth, and the drug circulates throughout your whole body. This means at the site of pain, the drug is more diluted but may also result in unwanted effects.

This paper is therefore all about trying to target the placenta specifically with a therapeutic to improve placental growth and development. The human placenta has two different layers: the outer syncytium, which is the site of nutrient transfer, and the underlying layer of proliferating cytotrophoblasts (CTB). These CTBs are important for growth and supporting nutritional demands of the growing fetus. These cells divide, and fuse with the syncytium.

  • Low proliferation of CTB = FGR and pre-eclampsia
  • High proliferation of CTB = macrosomia

The rate of growth/proliferation is affected by various hormones and growth factors, but also regulated by small RNA molecules called microRNAs (miRs). These regulate gene expression and consequently alter various biological processes such as cell proliferation. miR-145 and miR-675 are known to cause a reduction in placental growth, and so inhibiting these could improve placental growth in the pregnant women. But how does this get around the issue of teratogenicity? Well, our group have shown it’s possible to deliver a therapeutic molecule, which is packaged in lipids (a liposome), specifically to the placenta with minimising unwanted effects in the mother and fetus. This is done by using a specific placental homing peptide conjugate (a link of small molecules that form the foundations of proteins) which selectively binds to the placental surface. Think of it as a molecular postcode for the placenta!

structure miR inhibitor

So, put two and two together and in this paper we tried to use placental homing peptides to deliver miR-145 and miR-675 inhibitors directly to the placenta with the aim to enhance placental growth.

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What did we do?

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Testing the safety of miR inhibitor delivery

Ensuring that the miR inhibitors can be used as a clinical intervention for poor placental growth and development means prior safety testing. We need to make sure that their delivery doesn’t cause detrimental effects. We exposed pregnant mice to either a short or longer-term treatment of a fluorescent-labelled non-specific inhibitor. With a fluorescence microscope we visualised the presence and localisation of it (miR inhibitor in green) within the mouse placenta. Localisation of the miR inhibitor was found in the short-term treatment and also in the longer term one too.Results2 - fluor distribution writing

The miR inhibitor was not found in fetal tissues which is great! However, we found it localised in some of the maternal tissues suggesting a possibility of off-target effects – something that would need to be investigated further. The non-specific miR inhibitor didn’t cause a change to fetal or placental weight, litter size or the present of fetal abnormalities, so this indicates that it’s tolerated well in pregnancy… phew!

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Testing specific miR inhibitors in mice

Pregnant mice were either injected with a control solution (PBS), the non-specific (scrambled) inhibitor, or the treatments miR-675 inhibitor or miR-145 inhibitor.

Placental weight:

The miR-675 inhibitor did significantly increase placental weight. However, miR-145 did not. Despite this, interestingly a statistical test confirmed that it did reduce variability in placental weight. No placentas fell below the 10th weight centile for either inhibitor, which suggests they have growth-promoting effects.

Fetal weight:

Both miR-675 and miR-145 inhibitors increased fetal weight but the non-specific inhibitor altered the fetal weight distribution as well. At the moment, we aren’t too sure why. One potential reason could be species-specific effects, but if you want to geek out, check out the discussion section of the paper (link below) where other suggestions are discussed!

Results4 - placetnal fetal weight writing

We also tested the two specific miR inhibitors for any changes in litter size and number of miscarriages. Neither had an effect therefore further suggesting that this novel treatment is safe to use in pregnant mice, another step in the right direction!

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Testing the specific inhibitors in human tissue

Placental explants, which are chunks of fresh tissue, from first trimester (early pregnancy) and term (end of pregnancy) were cultured in the miR-675 inhibitor or miR-145 inhibitor with or without the placental homing peptide added on.  Both miR-675 and miR-145 with the peptide significantly increased the placental CTB cell proliferation, but so did their equivalents without the homing peptide, which was interesting. This enhanced cell proliferation was only found in first trimester placental samples.

Results5 - human prolif writing

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Summary

Without getting bogged down in all the intense sciencey discussion of this data (again, feel free to view the link for the actual paper below if you would like to read some more), what can we conclude from this study?

  • We provide evidence that the use of these homing peptides have a favourable therapeutic profile during pregnancy – they appear safe to use!
  • It’s the first piece of evidence for targeted delivery of a miR inhibitor to the placenta.
  • A homing peptide-miRNA inhibitor can be used to increase human placental growth in early pregnancy, which means it should be possible to manipulate the expression of those pesky placental miRs which contribute to pre-eclampsia and FGR.
  • This study suggests that these novel therapeutics may provide a new strategy for targeted treatment of compromised placental development and function.

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Of course further research is required to push the therapeutic potential of placental homing peptide-microRNA inhibitors further in the hope they will enter clinical trials in the future, but this study provides some really interesting data. Watch this space!

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You can find the original paper here!

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This was a much more science-heavy blog post than I normally write. Would you like more science explained posts?

Please comment below as always to let me know what you thought. Your feedback really is valuable to me. It helps me to grow as a science blogger and get the information out there that you like to read!

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Dose up on that vitamin D

Dose up on that vitamin D

 

Time to talk a bit of science, time to talk vitamin D!

In my very first post “Are you what your mother ate?” I gave you an outline of the overall concept of my PhD research and I mentioned how vitamin D levels in the mother are thought to affect the baby’s skeletal muscle development and function. So, today I’m going to focus on this wonderful molecule and why you need to get a regular vitamin D fix!

Vitamin D seems to be a hot topic in science at the moment, so I’m sure you’ve heard of it before. But why is it so important?

 

 

What is vitamin D and why is it important for me?

 

Vitamin D is a fat-soluble hormone that your body needs in order for it to function well and for you to be healthy. Research has shown that vitamin D acts at multiple sites around the body to cause various physiological effects important to us. Some major roles of vitamin D include:

 

 

Bone health

One of the first discoveries for the importance of vitamin D was its role in providing bone health. Calcium and phosphorus are two minerals that are essential for the development of strong bones. Vitamin D helps with the absorption of these two minerals for good bone metabolism and as a result an increase in bone density [1]. If you ever saw the TV adverts for Petits Filous yoghurts, then this explains why they were advertising the combination of calcium and vitamin D in their products!

bone

 

Brain development

The levels of vitamin D can impact the brain in various ways. Lower levels at birth have been associated with reduced cortical thickness (the cortex is the largest part of the human brain) and nerve growth. Neurotransmitter expression and consequently dopaminergic signalling are also linked with vitamin D levels, and this means various neurological process such as motor control and memory can be affected [2]. Neurological disorders, for example multiple sclerosis, have also been linked to vitamin D deficiency.brain

 

Immune system

Research suggests that vitamin D enhances the immune system and helps fight off those infections! Various cell types in the immune system are able to synthesize and respond to vitamin D. Without getting bogged down in the complexity of immunology, vitamin D helps in combatting bacterial infections by producing two proteins called cathelicidin and defensins which have antiseptic roles. Vitamin D supplementation has also been found to improve autoimmune diseases [3].immune

 

Heart/circulatory system

The role in the cardiovascular system is not so clear. Vitamin D status is thought to be important for cardiovascular health, and epidemiological studies have found an association between vitamin D deficiency and cardiovascular risk. Some studies suggest that vitamin D has protective effects in the cardiovascular system, and higher levels have been associated with a lower risk of coronary heart disease. However, the therapeutic benefit of vitamin D supplementation to treat this specifically has not yet been proven, and so research is ongoing… watch this space! [4] heart

 

Muscle function

Yay finally skeletal muscle – this is what I work on! Like other tissues, various components of the vitamin D signalling pathway have been found to be expressed in skeletal muscle, which in itself suggests that vitamin D plays a role in muscle development and function. Human studies have found that higher vitamin D levels in the blood are associated with an increase in muscle mass, strength, performance and a lower risk of falling [5, 6, 7]. It’s also thought that vitamin D regulates the expression of proteins important for muscle contraction, and therefore muscle force production. Vitamin D supplementation in elderly patients has found to increase the number and size of a specific type of muscle fibre, the type-II fibres [8], and an increase in muscle strength [9]. So here’s a take home message for you… if you want strong muscles get that vitamin D in you!muscle

 

 

How do we get vitamin D?

 

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There are two types of vitamin D: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Vitamin D is a unique vitamin. It’s pretty cool actually, our bodies can make our own vitamin D but we need a starting point – the sun! Those almighty UVB rays convert a molecule called 7-dehydrocholesterol in the skin to vitamin D3, and exposing our bare skin to the sun is an efficient way of increasing vitamin D levels. But warning! Just a short amount of sun exposure is enough for your body to make vitamin D so be careful and don’t burn!

 

As it’s the winter months we’re all wrapped up in our knitted jumpers and big scarfs. Unless you have a holiday booked to go and soak up some winter sun in the tropics, we’re pretty much covered up head to toe, and this means no skin exposure to direct sunlight. So how else can you get your dose of vitamin D? Exposure to sunlight is not the only way for our bodies to get vitamin D. We can get it through dietary supplements (I personally love the myvitamins range) and foods such as oily fish, red meat, eggs, cheese and fortified products.

 

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The vitamin D you get from the sun, dietary supplements or the food you eat then gets processed by the liver. The enzyme 25-hydroxylase converts the vitamin D into 25(OH)D, and this is the substance that’s measured when assessing vitamin D levels in the blood. This is then sent to various tissues (particularly the kidney) where an enzyme 1α-hydroxylase converts 25(OH)D into the active form 1,25(OH)2D. It is this activated vitamin D molecule that is then able to bind to its vitamin D receptor in order to perform its roles. You can see the vitamin D biosynthesis pathway below!

 

vit-d-biosynthesis

 

 

Vitamin D deficiency

 

What if I’m not getting enough vitamin D? Vitamin D deficiency (VDD) is when your body doesn’t have adequate vitamin D. It’s highly prevalent worldwide, with variation across populations. Having VDD can result in impaired bone, neurological, cardiovascular, immune and muscle health as detailed above, so it’s vital that you get your vitamin D fix.

VDD is also very common in pregnancy ((less than 25-50 nmol/L 25(OH)D)) and ranges from 5-70% in pregnant women across many populations. It has been linked to various obstetrical complications, affecting both the mother and baby’s health. So ladies, make sure you’re getting that all important vitamin D in your diet! Or even better, enjoy the sunshine – with caution of course!

 

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So there we are, an overview of why everyone should be mindful of getting enough vitamin D! I’ll be doing another blog post linking all of this back to why I’m researching maternal vitamin D deficiency and the effect it has on the baby’s muscle function. So I’ll let you absorb all of this wonderful information and come back soon with the whole Developmental Origins of Health and Disease (DOHaD) side of it, so look out for that one! 

 

If you want to learn more about vitamin D, then the Vitamin D Council website is a good place to start!

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Are you what your mother ate?

dohad-life-trajectory
Adapted from DOHaD

It’s near impossible to escape the news headlines concerning the rise in obesity, but despite this it’s hard to ignore all that delicious sugary and full-fat goodness lining the supermarket shelves. Obesity is known to increase the risk of developing health complications such as type-II diabetes and cardiovascular disease. On other end of the nutritional spectrum, undernutrition and deficiencies in various vitamins and minerals (e.g. vitamin D, calcium, iron) can also be detrimental to an individual’s wellbeing. However, how your body develops and functions is not necessarily all about your lifestyle and what food you put in your own body. There is increasing evidence that the mother’s diet before and during pregnancy can also affect the child’s health in later life.

Developmental Origins of Health and Disease

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The Developmental Origins of Health and Disease (DOHaD) hypothesis suggests that the environment a baby is exposed to during pregnancy affects the long-term health of the offspring via physiological adaptations during pregnancy, which carry on into adult life. Interesting right?! So this hypothesis arose from numerous epidemiological studies in human populations worldwide, which found that a low birth weight was a risk factor for developing various diseases in adult life. Results from the Hertfordshire Cohort Study found that a low birth weight was linked to an increased risk of high systolic blood pressure [1], coronary heart disease [2], type-II diabetes [3] and osteoporosis [4].

Skeletal muscle is key

Skeletal muscle is one of the main sites for glucose handling. Having good skeletal muscle health is important for whole body metabolic function, strength and also mobility/stability. What a mother ate whilst she was pregnant may impact on her baby’s muscle function in adulthood, and so my PhD is exploring how various diets during pregnancy can affect skeletal muscle development and function in the offspring.

Maternal diet and the life trajectory of skeletal muscle

The intrauterine environment is believed to be important for the development and growth of skeletal muscle, which consequently determines peak muscle mass and strength in adult life, and as a result impacts on its decline with ageing – see the figure below!

Studies have found a link between birth size and adult muscle mass and strength. Low birth weight (an indicator of poor maternal conditions during pregnancy) and a reduction in muscle strength was found in a study of 717 elderly men and women born in Hertfordshire between 1920 and 1930 [5]. This same relationship has also been observed in other studies of varying age groups, and all of these findings suggest that a suboptimal maternal environment during pregnancy may increase the risk of muscle wasting and impaired skeletal muscle function in later life.

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Life course model of muscle growth and decline with ageing. Adapted from here.

Studies investigating the effect of maternal overnutrition or undernutrition have observed differences in the offspring muscle. A research group based at The Royal Veterinary College in London found that feeding female rats a high-fat/high-sugar diet during pregnancy impaired offspring muscle development. In 21-day old pups they found a decreased number and size of muscle fibres, and an increase in the amount of fat deposited within the muscle [6]. Another group based at King’s College London found that feeding an obesogenic diet in pregnancy caused reduced activity levels and decreased muscle mass in young mouse offspring [7]. On the other end of the scale, researchers from my lab group at The University of Southampton found that nutrient restriction in the mother before implantation or in the later phase of pregnancy also coincided with a reduction in the triceps brachii muscle fibre density in the fetal sheep [8].

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But what nutritional drivers might alter this trajectory?

conceptual-framework

To explore this whole concept further my PhD is mainly focusing on how vitamin D deficiency in the pregnant mother affects offspring muscle. Vitamin D deficiency is highly prevalent in pregnant women, as well as the rest of the population. It is known to be important for various physiological processes such as calcium handling and bone formation, but research suggests that this vitamin is also important for skeletal muscle. Interestingly, vitamin D deficiency is associated with obesity as the increased fat tissue is thought to sequester vitamin D so it can’t be used by the body. So, to make it a little more complex (because PhDs are never straight forward!) I’m also looking at a high-fat pregnancy model to explore the relationship between obesity, vitamin D and muscle.

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Well there you have it, the overall concept of my PhD! In future posts I’ll be divulging into the more specifics of the experimental models I’ve been using and revealing some of my findings so far, so watch this space!

Take home message: you might not be the only one who’s affected by what you eat and the lifestyle you choose!

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