Organs grown inside your ‘personal pig’, and even a new penis made from a finger… How every part of your body could soon be REPLACEABLE

When I was a child, there was a TV show called The Six Million Dollar Man. In the opening credits, test pilot Steve Austin crashed his supersonic aircraft into the Tarmac. All seemed lost. But ‘we can rebuild him,’ said an unidentified, optimistic narrator. ‘Better than he was before. Better. Stronger. Faster.’

Cut to sped-up footage of actor Lee Majors in a red tracksuit, running, then scanning the horizon with his bionic eye.

At the time, in the mid-1970s, this was science fiction. Fast forward to today and it seems closer to reality – with headlines declaring superhuman prosthetics that can do everything from fold origami to rock climbing, while everything from brain cells to kidneys can be grown in the lab.

Indeed, much of the new ‘buzz’ in research is around regeneration: parts of the body grown from our own cells or animal cells. And some experts believe we are just over ten years from bio-printing our own organs.

It poses the question: are we nearing the moment when scientists can create a truly replaceable you?

I spent two years exploring the world of regenerative medicine for my new book, Replaceable You, and here are the most fascinating developments…

‘Personal pigs’ for parts 

Already, gene-edited pig hearts, kidneys and livers have been transplanted into patients with failing organs, buying them time until a healthy, human organ is available.

For example, in March 2024, a gene-edited pig kidney was given to a patient at Massachusetts General Hospital, in the US, with a second transplant on another patient the following month. Both patients survived about seven weeks but, sadly it wasn’t enough time to find new human organs for them.

Such is the progress in this area – known as xenotransplantation – that one specialist told me the ‘ultimate goal [is to] have your own personal pig’.

In other words, a pig with genes edited to match your own: skin, kidneys, heart, ready to use, like a car kept for parts.

I meet Professors Shaoping Deng and Yi Wang, experts in xenotransplantation, in Chengdu, China, to to find out more.

Professor Yi describes the ‘personal pig’ idea as chimerism – ‘using the pig to grow human organs’. A chimera is a mixture of two animals, a creature previously confined to mythology.

Scientists, then, are making pigs that are literally part-human.

Gene-editing techniques such as CRISPR – technology that precisely cuts into DNA to remove or add genetic material – makes it possible to significantly tweak a pig’s genetic blueprint.

The process goes something like this. You start with a pig blastocyst, the earliest stage of an embryo. Using CRISPR, knock out some genes, making it so the pig is now unable to grow, say, a kidney. This leaves an open developmental space.

If you then introduce some human pluripotent stem cells – which have the potential to develop into whatever they are instructed to – those cells will thrive in this empty space and, it is hoped, grow into a human organ. Ideally, the cells would come from the person who needs the organ, to avoid rejection. And the pig’s immune system wouldn’t reject the human organ growing inside it because the organ has always been a part of that pig.

But could pigs function normally with human organs?

Hopefully, Dengke Pan, founder of Chinese gene-editing company ClonOrgan, tells me, ‘but we are still in the laboratory stage’.

Penis transplants

I ALSO travelled to Tbilisi, Georgia, to find out more about a report in the Russian surgical journal Khirurgiia, titled ‘Finger transplant in the creation and reconstruction of the penis’.

Author Iva Kuzanov, a Georgian plastic surgeon, used a patient’s middle finger to reconstruct their penis, which had been amputated due to cancer. He is thought to have performed this surgery four or five times since. One of Dr Kuzanov’s surgical colleagues told me more. ‘We take this finger,’ he said, touching the middle digit of his left hand, ‘from here to here’, tracing a path from his fingertip to his wrist.

Skin from the underarm is used as a covering and the finger supplies the rigidity (and they choose the middle finger because it’s the longest digit). This gives the advantage of the body being less likely to reject it.

As with the standard implant surgery, the urethra is threaded through the surgically created penis, and the nerves and blood supply are reattached too.

Photographs show that most of the man’s penis had been amputated following cancer, leaving penetration or peeing while standing impossible. Surgery restores both functions.

The man in the photos was 60 at the time of the operation. His wife, 30, ‘was very happy’, I am told.

My Georgian hosts were unclear about whether it is possible to achieve orgasm. But I later read about other studies which suggest that while the absence of the glans penis (the tip of the penis that contains nerves needed for sexual pleasure) in the surgically created penis results in weak orgasms and ejaculations, in time ‘erotic zones’ develop on the new organ and the orgasm approaches ‘normal intensity’.

Super prosthetics

JUDY Berna, a 58-year-old writer from Colorado, US, asked to have her left foot cut off in 2004, when she was 37. That was because her foot was ‘a mess of flesh and bones but few working nerves’, she says. She was born with spina bifida and as she grew up, her foot became more twisted, resulting in infections and surgeries.

She watched people with prosthetic limbs effortlessly managing things she struggled with.

But it took decades to find a surgeon willing to amputate. ‘“It still has healthy tissue,” is what they said to me,’ she recalls. ‘I’d go, “Yes, but I can’t walk on it”.’

Now an amputee with a prosthetic leg, she can do so much more than walk. This is because there are now prosthetic lower limbs with specific attachments for rock-climbing and surfing; blades for running, basketball and football.

Arm prosthetics include attachments for holding the kit for everything from archery to table tennis and fishing to uneven bars, billiards and weightlifting. There are also swim fins and handlebar adapters for mountain bikes.

Musicians can buy adapters that grip drumsticks, violin bows and guitar picks. Most recently, they designed an adaptive device for folding origami. And Judy knows a prosthetist who made a mop foot for his wife.

Printed organs

I visit Adam Feinberg, a professor of biomedical engineering at Carnegie Mellon University in Pennsylvania, US, to see if printing body parts is as far along as it seems.

I’d read of a clinical trial involving a 3D bioprinted ear – to be precise, the outer part.

The complexity of the task is enormous. To function, any variety of muscle cells, for instance, needs to be ‘printed’ in a precise manner.

In the deltoid muscle in the shoulder, cells are arranged in a fan shape. This is partly what gives the shoulder its impressively broad range of motion.

For human bioprinting, the ‘ink’ is made from live human cells and a mixture of proteins that are found in our extracellular matrix (the fluid that surrounds our cells and provides the nutrients they need to function and grow).

Using 3D data from a patient’s MRI scans, the printer would lay down the various inks in the structure required for each tissue type.

Anyone could potentially benefit. The idea is, if you need any new ‘bit’ of yourself, they could print it – from collagen patches for healing wounds to entire organs.

In Professor Feinberg’s lab, I see the work printing the trickiest architecture of all: heart muscle.

Cardiomyocytes – cells responsible for the heartbeat – are arranged in a helix shape around the heart’s chambers. As the organ beats, it not only squeezes but also twists slightly – a bit like wringing a wet towel. This maximises the volume of blood pumped with each beat.

Alignment is especially important with heart muscle because without it, the cells’ electrical impulses don’t fire rhythmically and nothing, pumping-wise, is achieved. Scientists managed to recreate the heart constructs that beat in a co-ordinated manner – a huge achievement.

I ask Professor Feinberg when he thinks science will arrive at the point of implanting entire functional bioprinted organs into patients. A decade plus, is his answer.

Fish skin for burns

At Massachusetts General Hospital’s burns unit, I watched a medical intern plane a skin graft from a patient’s thigh which was a third of a millimetre thick – so slim you could have posted it with a first-class stamp.

Taking a graft from a patient to be used on another area of their body is called autografting. However, with a major burn, surgeons quickly run out of graftable skin.

But as Dr Jeremy Goverman, a plastic surgeon at the hospital, told me, while waiting for more skin to regrow on a burns victim, a xenograft – skin from another species – can be used.

Temporary grafts protect wounds from infection and make changing bandages less painful for patients.

Dr Goverman tells me he has used Icelandic cod skin grafts, which appear to reduce inflammation.

He’s slightly equivocal about the fish skin trend, which started in Brazil with tilapia skin, despite many of his colleagues rhapsodising about it. ‘It worked well,’ he says, ‘but they were using it on second-degree burns.’ The difference between second and third-degree burns is substantial – rather like Richter earthquake numbers, one step up doesn’t sound like much, but in terms of the damage wrought, it’s substantial.

Adapted from Replaceable You by Mary Roach (Oneworld Publications, £18.99), published on October 2.

© Mary Roach 2025. To order a copy for £17.09 (offer valid 14/10/2025; UK P&P free on orders over £25) go to mailshop.co.uk/books or call 020 3176 2937.

New hair for bald heads

You can now create new, healthy cells – your own – from scratch, thanks to pluripotent stem cells. Dr Kevin D’Amour, chief scientific officer at Stemson Therapeutics, a biotech firm specialising in cell engineering, says this is the future.

So what are pluripotent stem cells? As an embryo, you were a blob of them: master cells able to turn into specialist cells – some became blood cells, some bone, some nerves.

In 2006, Shinya Yamanaka, a researcher at Kyoto University, figured out a way to regress adult, specialised cells to pluripotent stem cells, or iPS cells.

Researchers have now worked out how to take iPS cells and instruct them to become, in theory, whatever type of cell a patient needs. Clinical trials are under way with iPS-derived retinal cells, pancreatic cells and heart cells, putting medicine on the brink of reversing conditions such as diabetes, heart failure and even baldness.

Dr D’Amour is working on prompting iPS cells to become dermal papilla cells and keratinocytes, the building blocks of human hair follicles.

He says: ‘We are not talking about growing whole organs in a lab. That’s a long way off.’ However, he evisages a future where people will have iPS cells created and then banked, much the same way people today store sperm and eggs.