Adult skates can spontaneously repair cartilage injuries
Researchers have found that adult skates have the ability to spontaneously repair injured cartilage, using a type of cartilage stem cell. Human cartilage has very limited capacity for repair, and the finding may lead to new stem cell treatments for human cartilage injuries.
Published today in the journal eLife, the study identified a new type of cartilage stem cell in the skeleton of adult skates, Leucoraja erinacea. These cells enable skates to keep making new cartilage throughout their life, so their skeleton can keep growing and any cartilage injuries can be repaired.
Current stem cell therapies for cartilage repair in humans are not very effective because lab-engineered cartilage from adult stem cells has a tendency to start turning into bone. Previously, no animal has been found to have the ability to make new cartilage during adulthood that stays as cartilage, rather than turning into bone, or have the ability to spontaneously repair injured cartilage.
“Cartilage injury in humans – for example because of osteoarthritis or a sports injury – is a huge problem, and a huge economic burden,” said Dr Andrew Gillis from the University of Cambridge’s Department of Zoology and the Marine Biological Laboratory in Woods Hole, USA, who led the research.
“We are tremendously excited to find that skates can spontaneously repair injured cartilage, and to have an insight into how this happens. It paves the way for developing better treatments to repair cartilage injuries in humans, which are currently very limited in their effectiveness.”
Cartilage cells within the fin cartilage of a skate hatchling
Cartilage cells within the fin cartilage of a skate hatchling
The cartilage stem cells, called chondroprogenitors, were found in the fibrous tissue, called the perichondrium, which wraps around cartilage in the adult skate. By labelling these stem cells with a fluorescent marker, the researchers could trace the cells they created - and found that they ended up as cartilage in the adult skeleton. These cells were also shown to express genes that control cartilage development.
Fin cartilage of a skate embryo, showing expression of the gene encoding collagen (green) in cartilage cells
Fin cartilage of a skate embryo, showing expression of the gene encoding collagen (green) in cartilage cells
This study found that embryonic development of cartilage in the skate closely mirrors that in humans, but unique features of the adult skate skeleton – including the presence of cartilage stem cells in the perichondrium – facilitate the continued growth of cartilage throughout life.
Most cartilage in humans is formed as the skeleton first develops, and this is later replaced by bone. By the time adulthood is reached, cartilage only exists in a few places in the body such as the joints. Human cartilage has no blood or nerve supply, and it has no resident stem cell population, so it has very limited capacity for repair.
Osteoarthritis is a debilitating deterioration of joint cartilage, with symptoms ranging from stiffness and joint pain to complete immobility. It can severely impact quality of life, and has an extremely high economic burden, so there is great interest in identifying novel therapeutic strategies to promote joint cartilage repair.
The researchers warn that taking ‘shark cartilage’ tablets should not be considered as a cure for joint pain or any other illness, as there is no scientific evidence that they work.
Their next step is to understand the molecular mechanisms that allow this specialised stem cell type to make cartilage as a stable tissue in adult skate. They hope this will allow them to manipulate human stem cells to behave in a similar way, and enhance their ability to generate stable cartilage for transplantation and repair.
This research was funded by Wellcome, the Royal Society, the Isaac Newton Trust and the Fisheries Society of the British Isles.
Reference: Marconi, A. et al: ‘Adult chondrogenesis and spontaneous cartilage repair in the skate, Leucoraja erinacea’, ELife, May 2020, DOI: 10.7554/eLife.53414
Image credits: Andrew Gillis
TopBuilt with Shorthand Summary:Researchers have found that adult skates have the ability to spontaneously repair injured cartilage, using a type of cartilage stem cell. Human cartilage has very limited capacity for repair, and the finding may lead to new stem cell treatments for human cartilage injuries.
Image: Affiliation (schools and institutions): Department of ZoologySchool of Biological SciencesExternal Affiliations: Marine Biological LaboratoryWoods HolePeople (our academics and staff): Andrew GillisSection: ResearchNews type: NewsStudy identifies 275 ways to reduce spread of coronavirus following lockdown
The study identified 275 ways to reduce transmission of the coronavirus. Medical possibilities were not considered. It does not offer recommendations: a shortlist of the most appropriate options for specific regions and contexts should be considered in the context of their likely effectiveness, cost, practicality and fairness.
“There’s increasing pressure to re-open the economy and get people back to work and out of isolation. But if we return to operating as we did before the pandemic, there will be a second wave of the virus. All activities will need to be considered individually, and phased back in carefully, depending on the risk they pose to spreading the virus,” said Professor William Sutherland in the University of Cambridge’s Department of Zoology, who led the study.
Strict lockdown measures are proving to be effective in controlling the spread of coronavirus in many countries, but are putting a major strain on the population’s mental and physical health, and on the economy. Mass vaccination is not likely before the second half of 2021.
Measures such as physical distancing, enhancing personal hygiene and reducing contamination are likely to remain central elements of all control strategies for some time. The study, which has not been peer reviewed, lists the range of practical options available to achieve these measures, including:
• Café owners could open outdoor areas only at first, and wipe down tables - spaced well apart - after each customer.
• Access to public parks could be restricted to different age groups at different times of day, with gates left open so they don’t need to be touched, and users asked to walk on the right side of the pavement or clockwise around large open spaces.
• Petrol stations could become fully contactless, with attendants serving customers who pay from inside their car.
• Patients with doctors’ appointments could be asked to wait in their car outside the surgery until called in.
• School classes could be split into smaller groups with dedicated teachers, who only go into school one week in every three.
“It’s basically about how to stop people hanging around together, and phasing in activities starting with the ones that are the safest. Making this happen will be up to the people responsible for every element of society,” says Sutherland.
Identifying, assessing and applying a wide range of options could enable some of the stricter lockdown conditions to be lifted earlier, and make the transition period shorter, say the researchers. The ultimate aim of a successful transition is to achieve ‘Resilient Normality’ - a new way of existing in the world that makes us less susceptible to future pandemics.
Information was gathered by a method called Solution Scanning, which uses a wide range of sources to identify a range of options for a given problem. Sources included experts in a variety of fields, crowdsourcing on social media, and published research.
“In starting a process of decision-making or guidance-production, it’s sensible to be aware of the range of possible options. Policy makers and practitioners must decide which strategies are appropriate to phase in at different stages of the transition from lockdown,” said Sutherland.
The list of potential options is available online at https://covid-19.biorisc.com
This research was funded by The David and Claudia Harding Foundation, Arcadia and MAVA.
Reference (preprint)
Sutherland, W.J. et al: ‘Informing management of lockdowns and a phased return to normality: a Solution Scan of non-pharmaceutical options to reduce SARS-CoV-2 transmission.’ 2020. DOI: 10.17605/OSF.IO/CA5RH
Phased re-opening of schools, businesses and open spaces should be considered alongside a range of practical ways to keep people physically apart, say the authors of a new study on how lockdown can be eased without a resurgence of coronavirus infections.
Policy makers and practitioners must decide which strategies are appropriate to phase in at different stages of the transition from lockdownWilliam SutherlandMabel Amber from Pixabay
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The world's their fish finger
fish finger
Smothered in ketchup or squished into a sandwich, there’s one tasty convenience food that’s hard to resist. With over 1.5 million of them eaten every day in Britain, fish fingers are one of the nation’s favourite foods. Now two Cambridge researchers believe that a twist on this 1950’s creation might help address the challenge of sustainably feeding our global population.
David Willer and Dr David Aldridge are on a mission to work out how to look after our planet and people’s health at the same time. Zoologists in the University of Cambridge Conservation Research Institute, they want to demonstrate that bivalve shellfish – oysters, scallops, mussels and clams – can be a source of affordable, sustainable and nutritious food.
“In the developed world, over two billion people eat too many calories but not enough nutrients to stay healthy,” says Willer, “and a billion people in the developing world don’t have access to enough food. We believe bivalves are the answer!”
Better for the planet“This is about providing people with food that is environmentally sustainable but also nutrient dense,” says Willer. “We know that meat and fish have a greater environmental impact than plant-based foods. But the environmental footprint of bivalve aquaculture is even lower than many arable crops in terms of greenhouse gas emissions, land and freshwater use.”
Bivalves sit right at the bottom of the food chain. They are filter feeders, and eat whatever is suspended in the water, which is usually either decaying organic matter or algae. This is in stark contrast to salmon farming, which takes five kilos of wild fish for every kilo of salmon produced. Willer says that if just 25% of this ‘carnivorous fish’ aquaculture was replaced with an equivalent quantity of protein from bivalve aquaculture, 16.3 million tonnes of CO2 emissions could be saved annually – equivalent to half the annual emissions of New Zealand.
Bivalves offer other environmental benefits too. Farming them has many benefits on marine ecosystems including the provision of nursery habitats for fish, coastal protection, and helping to clean up waterways by filtering out nuisance algae and suspended sediments.
Room to growAcross the world there is a huge area of coastline suitable for growing bivalve shellfish – an estimated 1,500,000 square kilometres, equivalent to over six times the total area of the United Kingdom. Willer says that developing just one percent of this could produce enough bivalves to fulfil the protein requirements of over one billion people.
“The regions of the world where there’s a lot of available coastline include places where people need extra sources of protein in their diets, such as the west coast of Africa, and Asia,” says Willer. In developing countries like these, where populations are growing, there are high levels of malnutrition because people are not getting the key nutrients and the energy they need from traditional diets.
Bivalves have a higher protein content (per kcal) than beef. They are high in many key nutrients that humans need, including vitamin A, iodine and zinc, and omega-3 fatty acids. A small quantity eaten regularly is a far more efficient way of getting required levels of these nutrients compared with eating a large variety of plant crops, all of which require land and resources to produce.
The safety issueThe challenge for the researchers is to increase the productivity of bivalve farming, while at the same time raising safety standards. Their work focuses on oysters and other bivalves at the hatchery stage, where they are grown for a year before being put into open sea – on ropes or in cages – to grow to full size.
“At the moment, bivalve hatcheries are very small scale and pretty basic,” says Willer. “Farmers grow algae to feed the oysters in big tanks using lots of light and energy. The tanks get contaminated all the time, so a lot of the feed is bad quality or gets wasted. This is the main cause of bacterial disease in shellfish. For a farmer working alone, it’s a difficult venture.”
One of the reasons why some people won’t eat mussels, oysters and other bivalves is fear of food poisoning – of which there have been some high profile cases, including a recent gastroenteritis epidemic in Brittany. Oysters in particular tend to be eaten raw, so anything harmful within them – most commonly norovirus – is not killed before they’re consumed by humans.
Taking controlWiller and Aldridge’s solution is to change the bivalve feed. They have developed a specially formulated diet for the shellfish that enables farmers to take better control of their hatcheries.
“We call it a ‘microencapsulated BioBullet’,” says Aldridge. “It contains algae, just like the algae being used in the hatcheries now, except ours is grown on a commercial scale and then powdered down and sterilised. As well as preventing the introduction of diseases into hatcheries, our new method is about 100 times more efficient than the current one in terms of energy use, carbon emissions and cost.”
The fact that the algae is sourced from the waste streams of other aquaculture systems gives this method an additional environmentally friendly credential. The approach has attracted funding from European Institute of Innovation and Technology’s Food programme (EIT Food) – an initiative working to make the food system more sustainable, healthy and trusted.
Microencapsulation involves putting the powdered algae inside a type of miniature eggshell made from vegetable oil, and adding a coating to make it buoyant and palatable. Other nutrients can be added as required, to alter the nutritional value or even palatability to the shellfish and ultimately the dietary benefits to human consumers.
This creates the potential to address particular nutrient deficiencies in a consumer population. Any nutrient or vitamin is far more easily absorbed by the body when it is integrated into a protein and fat source, rather than being in supplement form.
When bivalves are harvested they are held in tanks for a week before being sent to market. Clean water is run through the tanks to flush out the contents of their guts. At this stage, anything fed to the shellfish will remain in their gut cavity and be eaten by the consumer.
“The additives are where things get really interesting,” says Willer. “One of the unique things about shellfish is that when you eat one, you eat the entire organism – including the gut. The microencapsulated diet allows either a flavouring or nutrient to be delivered at the final stage of shellfish production so it stays within the bivalve when it’s harvested.”
Oyster hatchery. Credit: University of Maryland Center for Environmental Science on Flickr
Oyster hatchery. Credit: University of Maryland Center for Environmental Science on Flickr
The microencapsulated BioBullets. Credit: David Willer.
The microencapsulated BioBullets. Credit: David Willer.
Magnification of the microencapsulated BioBullets. Each particle is less than 100µm in diameter.
Magnification of the microencapsulated BioBullets. Each particle is less than 100µm in diameter.
Oyster in a clean water tank. Credit: Oregon State University on Flickr.
Oyster in a clean water tank. Credit: Oregon State University on Flickr.
Commercial developmentWiller and Aldridge have been collaborating closely with a shellfish company in Whitstable, Kent – a town defined by the oysters it has produced since Roman times – to develop their microencapsulated diet into a saleable product. In addition, Aldridge and another team member, Dr Camilla Campanati, have tested products in commercial settings in Spain, achieving remarkable results.
“Mediterranean mussel spat reared on our BioBullets grew just as fast and survived just as well as mussels fed with the leading commercial alternative, an algal concentrate,” says Aldridge, “but our products cost ten times less than this alternative and are much easier to handle and store.” The results of an independent consumer panel are very encouraging too: mussels fed on BioBullets were deemed just as tasty and attractive as mussels produced by conventional methods.
“It’s surprising how little research has been done on this,” says Willer. “A few people tried to make a type of microencapsulated feed in the 1980s but it didn’t work, partly because the technology wasn’t available. We hope that with the recent successful trials of our new forms of microencapsulated diets, and continued refinement, it won’t be long before the concept goes mainstream and drives the expansion of the bivalve industry on a huge scale.”
The final hurdleThere is just one last challenge to overcome before bivalves could help to feed the world. “They’re not actually a food many people tend to like,” admits Willer, “and I think that’s probably one of the biggest challenges. We can increase the production of a very sustainable food, but if no-one eats it, it’s pointless.”
Diets have changed a lot since the 19th century when oysters in Britain were cheap and eaten in large quantities, mostly by the poorest in society. Today, oysters and other bivalve shellfish are perceived as luxury foods in the Western world – but only by those who relish the salty, slippery sensation of slurping them down.
Rather than trying to convince the rest of us to change our dietary preferences, Willer and Aldridge are looking at novel ways to make bivalves more palatable – essentially by disguising them. One idea is to swap out fish – which is often sourced unsustainably – for processed clam meat in a new form of ‘bivalve fishfinger.”
“Climate change is an impending pressure, and this pressure extends to our food supply,” says Aldridge. “We need to make fairly rapid changes to people’s diets, and trying to encourage huge cultural shifts just isn’t going to work. I think modifying things people are familiar with is the best way to make bivalves into a more acceptable product.” Microencapsulated diets really could be the start of a revolution.
This research is funded by a BBSRC studentship to David Willer, the EIT Food Project MIDSA to David Aldridge, and BioBullets Ltd.
Additional photo credits (top to bottom): Fish fingers (anon); Clams by Andrew Yee on Flickr; Mussels by fancyday on Pixabay; Coastline in Senegal by Peter Harrison on Flickr; Whitstable by Mariuz Kluzniak on Flickr and by Judith on Flickr; Mussels by G. Morel on Flickr; Plate of oysters by Jameson Fink on Flickr; Oysters by Jean Louis Tosque on Pixabay.
TopBuilt with Shorthand Summary:Smothered in ketchup or squished into a sandwich, there’s one tasty convenience food that’s hard to resist. Now two Cambridge researchers believe that a twist on the classic fish finger might help address the challenge of sustainably feeding our global population.
Image: Affiliation (schools and institutions): School of the Biological SciencesDepartment of ZoologyUniversity of Cambridge Conservation Research Institute (UCCRI)People (our academics and staff): David AldridgeDavid WillerSubject (including Spotlight on ... where applicable): Sustainable EarthGlobal food securityfishSection: ResearchNews type: FeaturesWatching TV helps birds make better food choices
Seeing the ‘disgust response’ in others helps them recognise distasteful prey by their conspicuous markings without having to taste them, and this can potentially increase both the birds’ and their prey’s survival rate.
The study, published in the Journal of Animal Ecology, showed that blue tits (Cyanistes caeruleus) learned best by watching their own species, whereas great tits (Parus major) learned just as well from great tits and blue tits. In addition to learning directly from trial and error, birds can decrease the likelihood of bad experiences - and potential poisoning - by watching others. Such social transmission of information about novel prey could have significant effects on prey evolution, and help explain why different bird species flock together.
“Blue tits and great tits forage together and have a similar diet, but they may differ in their hesitation to try novel food. By watching others, they can learn quickly and safely which prey are best to eat. This can reduce the time and energy they invest in trying different prey, and also help them avoid the ill effects of eating toxic prey,” said Liisa Hämäläinen, formerly a PhD student in the University of Cambridge’s Department of Zoology (now at Macquarie University, Sydney) and first author of the report.
This is the first study to show that blue tits are just as good as great tits at learning by observing others. Previously, scientists thought great tits were better, but had only looked at learning about tasty foods. This new work shows that using social information to avoid bad outcomes is especially important in nature.
Many insect species, such as ladybirds, firebugs and tiger moths have developed conspicuous markings and bitter-tasting chemical defences to deter predators. But before birds learn to associate the markings with a disgusting taste, these species are at high risk of being eaten because they stand out.
“Conspicuous warning colours are an effective anti-predator defence for insects, but only after predators have learnt to associate the warning signal with a disgusting taste,” said Hämäläinen. “Before that, these insects are an easy target for naive, uneducated predators.”
Blue tits and great tits forage together in the wild, so have many opportunities to learn from each other. If prey avoidance behaviour spreads quickly through predator populations, this could benefit the ongoing survival of the prey species significantly, and help drive its evolution.
The researchers showed each bird a video of another bird’s response as it ate a disgusting prey item. The TV bird’s disgust response to unpalatable food - including vigorous beak wiping and head shaking - provided information for the watching bird. The use of video allowed complete control of the information each bird saw.
The ‘prey’ shown on TV consisted of small pieces of almond flakes glued inside a white paper packet. In some of the packets, the almond flakes had been soaked in a bitter-tasting solution. Two black symbols printed on the outsides of the packets indicated palatability: tasty ‘prey’ had a cross symbol that blended into the background, and disgusting ‘prey’ had a conspicuous square symbol.
The TV-watching birds were then presented with the different novel ‘prey’ that was either tasty or disgusting, to see if they had learned from the birds on the TV. Both blue tits and great tits ate fewer of the disgusting ‘prey’ packets after watching the bird on TV showing a disgust response to those packets.
Birds, and all other predators, have to work out whether a potential food is worth eating in terms of benefits – such as nutrient content, and costs – such as the level of toxic defence chemicals. Watching others can influence their food preferences and help them learn to avoid unpalatable foods.
“In our previous work using great tits as a ‘model predator’, we found that if one bird sees another being repulsed by a new type of prey, then both birds learn to avoid it in the future. By extending the research we now see that different bird species can learn from each other too,” said Dr Rose Thorogood, previously at the University of Cambridge’s Department of Zoology and now at the University of Helsinki’s HiLIFE Institute of Life Science in Finland, who led the research. “This increases the potential audience that can learn by watching others, and helps to drive the evolution of the prey species.”
This research was funded by the Natural Environment Research Council UK and the Finnish Cultural Foundation.
Reference
Hämäläinen, L. et al, ‘Social learning within and across predator species reduces attacks on novel aposematic prey’, Jan 2020, Journal of Animal Ecology. DOI: 10.1111/1365-2656.13180
By watching videos of each other eating, blue tits and great tits can learn to avoid foods that taste disgusting and are potentially toxic, a new study has found.
By watching others, blue tits and great tits can learn quickly and safely which prey are best to eat.Liisa HämäläinenNataba, Adobe Stock imagesGreat tit and blue tit. Credit: Nataba, Adobe Stock images
The text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright ©University of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.