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Scientists restore missing frog limbs

frog in a biodome
frog in a biodome Image credit: dailymail.co.uk

Scientists have gone ‘hopping mad’ using a five-drug cocktail on frogs so the amphibians can regrow missing limbs.

Over a period of 18 months adult frogs were able to restore their legs until they were ‘almost fully functional’ when applied in a silicone wearable was attached to the wounds.

In the human world it is not possible to redevelop functioning limbs for patients who have lost legs or arms due to amputation or illnesses such as diabetes.

But the study conducted by professionals at Tufts University in Medford, Massachusetts and Havard University’s Wyss Institute in Boston, Massachusetts could bring new hope.

Nirosha Murugan, research affiliate at the Allen Discovery Center at Tufts Uni said: 'It's exciting to see that the drugs we selected were helping to create an almost complete limb.

'The fact that it required only a brief exposure to the drugs to set in motion a months-long regeneration process suggests that frogs and perhaps other animals may have dormant regenerative capabilities that can be triggered into action.'

African clawed frogs (Xenopus laevis) with missing limbs were sealed under a BioDome (a silicone cap) with a silk protein gel loaded with the five-drug cocktail for 24 hours.

Within 18 months the frogs had regrown their legs with boneless toes enabling them to be able to swim.

Animals such as frogs, which live in water, have the ability to regenerate – the BioDome recreated their environment to rebuild their missing limbs without damaging their scar tissue.

The cocktail was formed from drugs which helped the process by tampering down inflammation, preventing scarring by producing collagen (the most abundant protein in human bodies) and growing new nerve blood vessels, nerve fibre and muscle.

Most of the frogs regained almost full capability of at least some of their limbs with several ‘toes’.

David Kaplan at Tufts Uni said: 'Mammals and other regenerating animals will usually have their injuries exposed to air or making contact with the ground, and they can take days to weeks to close up with scar tissue.

'Using the BioDome cap in the first 24 hours helps mimic an amniotic-like environment which, along with the right drugs, allows the rebuilding process to proceed without the interference of scar tissue.' 

Humans have the ability to close wounds with new tissue growth and our livers can regenerate to a full size, even if half of the organ is missing – but we are unable to restore a complex limb such as an arm or a leg.

As a substitute the human body forms scar tissue over major injuries to prevent blood loss which puts a stop to any further development.

The next step is to regrow more complex frog limbs with normal digits, muscular features and detailed skeletal.

The five-drug cocktail contained - BDNF (Brain Derived Neurotrophic Factor), 1,4-DPCA (1,4-dihydrophenonthrolin-4-one-3carboxylicacid), RD5 (resolvin D5), GH (growth hormone) and RA (retinoic acid)