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Pigs, frogs and children who regrow fingers

Surprisingly, there is a scientific basis for the ability to regrow fingers - also in humans

Leaf-tailed gecko - sheds its tail and regrows it. Illustration:
Leaf-tailed gecko - sheds its tail and regrows it. Illustration:

Lee Spibak was a simple worker in a hobby shop, until his finger accidentally got caught in the flames of a toy plane. The result was not amusing: Spibak lost almost two centimeters of his finger. His doctors were sure that the story of the lost finger would end in the trash can. That is, if it could be found at all.

"We don't know where the piece went." Spibak admitted later in an interview.

The wounded man did not lose hope. In his grief, he turned to his brother, who also happened to be the owner of a tissue restoration company. The good brother sent him an extraordinary powder - "fairy dust", in Spibak's own language. Spibak dipped the stump in the powder every day, for ten days.

And the finger, miraculously, grew back.

"Already the second time I put the powder on, I could see growth. Every day it got longer. Finally, it closed and was for the finger," said Spibak[1]. "It took about four weeks before it completely closed... full sensation, full movement."

The secret in the powder? A substance extracted from the cells of the bladder wall of a pig. According to the company, it is an 'extracellular matrix': connective tissue that exists all over the body, and contains growth factors that guide the cells, well, to grow. Thanks to the powder, the cells in Spibak's finger avoided the formation of scar tissue, and concentrated on rapidly dividing and differentiating into the right type of cells, in order to restore the nerves, bone, skin - and even the nail.

Surprisingly, there is a scientific basis for the ability to regrow fingers - also in humans.

Dr. Christopher Allen, of the University of Washington Hand Medicine Center, was not thrilled when he had to treat an eight-year-old girl who lost the tip of her finger in an accident. The girl slipped her finger in the wheel of her brother's bicycle, and a few seconds later was rushed to the hospital with the tip of the finger lying in a bag of ice.

Alan tried to reconnect the blood vessels in the finger and its amputated friend, but was unable to make the necessary connection. He decided to make a 'biological bandage', at the behest of surgeons. Simply put: he stuck the tip of his finger on the stump and hoped for the best.

"The girl returned within a few weeks with the old fingertip in the bag, and a new fingertip on her palm." Allen said in an interview with NPR. It was much better than anything I could have given her…”[2]

That eight-year-old girl joins certain animals in her impressive ability to grow organs - salamanders, snails and frog tadpoles, among others. All of these are able to regrow fingers, legs and even parts of their heads. In the seventies it was proven for the first time that human children are also able to regenerate parts of the body - at least their fingers[3]. There is only one important condition for success in the task: the nail cannot be completely severed. At least a small part of the nail must remain on the finger.


A group of researchers led by Mayumi Ito from New York University provided a clue to solving the mystery about a decade ago. She recognized that under the base of the nail of mice there are groups of stem cells. Stem cells are cells that are capable of continuing to divide and differentiate into different cell types throughout most of a person's life. If the fingers are amputated, but the stem cells still remain at the end of the stump, then they are able to work vigorously to restore the injury[4]. The same principle, apparently, also applies to children.

It is important to clarify that salamanders and other amphibians exhibit a much more impressive capacity for recovery than that of human children or non-human mice. The reason, apparently, is that amputations in those super-regeneratives do not create scar tissue as can be found in humans. Instead, the cells in the area of ​​the amputation send chemical messages to the nerves that begin to regrow, while other cells in the area lose their shape and function in order to regrow in the ways expected of them to complete the missing limb.[5]. None of this happens in humans - young, old or at all.

Or maybe yes?

Does Spibak's story show that there is a way to help adults and even the elderly regenerate their fingers? No wonder the press was filled with excitement at the significance of the study. As written in the BBC -

"... the powder may prove to be a medical breakthrough on a massive scale."

Unfortunately, there are always people who just have to ruin a good story.

The sensational results attracted the attention of David Baty and Ben Goldcaire. The first was an investigative journalist from the Guardian. The second - has industry experience in detonating pseudo-medical illusions. The suspicion of the two was aroused in the face of the impressive story. They went through the various coverages in the media and realized that the journalists repeated the same quotes, which they apparently copied from the original BBC article. At this point, the suspect had already gotten out of bed and started jogging.

Batty interviewed an expert in the field of plastic surgery of the hand, who declared the story ridiculous from start to finish. He reviewed the photos shared with the press, and determined that the injury did not appear to be serious in the first place.

"It's a ridiculous story - absurd and extreme," said Professor Simon Cai. "It seems that it was a completely normal injury to the tip of the finger, with healing that is not at all unusual. All wounds undergo a repair process. It's junk science.”[6]

Goldcare, an expert on fabricated claims in the field of medicine, added and clarified that -

"... Wounded fingers do heal, sometimes badly, sometimes well, just like scratches and wounds on the rest of the body. The BBC said that "the nerves, the tissue, the blood vessels, the skin" grew back. Yes. All over the country as we speak. The body is an amazing thing."

A bit more research revealed that although the story made headlines in 2008, it appeared in the news for the first time as early as 2007, in exactly the same form: same quotes, same characters. And all this when the injury itself happened and he recovered, apparently two years before, in 2005[7].

The company that produced the powder - AceLL - still exists and was even purchased last year by another large pharmaceutical company[8]. This means that there is probably some truth to Spibak's story, even though it is covered with excessive enthusiasm by the media. But how true? No one is sure of that.

"There is no clinical evidence to support the claims." Kai concluded. "If you could regenerate such body parts, the first place you would contact is a serious scientific magazine... because it would be a revolution worthy of a Nobel Prize."

The good news? Now, almost 15 years after Spibak, such an article was published in a serious scientific journal.

So far we have reviewed studies (and a story) from the last fifteen years. Now we will move on to a study that was published in January 2022 in a "serious scientific magazine". Not just serious, but from the creator of Science - one of the most important magazines in the scientific world[9].

The researchers conducted their experiments on adult frogs. This is an important distinction, because tadpoles are able to regenerate limbs just like salamanders. After reincarnating into adult frog form, they lose the ability to immortalize. Adult frogs are simply unable to regrow their legs, much like the hairless apes we know so well.

In order to start research, the scientists had to find frogs without a right leg. Miraculously, they located 115 such frogs in their laboratory, who happily volunteered for the experiment. A third of the frogs received special treatment: the researchers put a tiny device on the stump that fed the wound with five growth factors known to encourage wound renewal. The other third received only the device, without the growth factors. The last third received no treatment of any kind and had to continue living their lives without even hope for the growth of a new leg.

The facility, it must be admitted, was certainly not very comfortable for the frogs, but they had to endure its presence for only 24 hours. It was then removed from the stumps, and the amphibians could return to their monotonous lives. The researchers continued to follow all three populations for a year and a half, to understand if the short treatment really helped.

From the fact that I am covering this study, you can understand that the answer was yes. Very positive, actually. Among the frogs that received the device with the growth factors, a significant delay in wound closure was evident. Apparently this is a harmful result, but the full meaning was that instead of a scar being formed, the cells in the area could go back to divide and differentiate and recreate the limb. Throughout the year-and-a-half after the amputation, they lengthened the bone in the area and grew muscles, nerves and blood vessels around it.

The frogs could use their regrown legs to stand, swim and exert force on their environment. They even regained their senses. The frogs in the control groups, on the other hand, grew only a useless 'thorn', which was completely devoid of sensory ability.

"As far as we could measure, there were no differences compared to the uninjured limb," said Michael Levine, one of the scientists involved in the study. The regenerated fingers were indeed shorter than usual, but the limbs were still in growth stages at the time the experiment was reported, and it is possible that the fingers would eventually reach their original length.

All this, as mentioned, following a 24-hour treatment immediately after the injury.

It will certainly not be surprising to reveal that the researchers are currently testing the same approach in mammals as well, in the hope that one day it will be possible to use it in humans as well. As they conclude in the last sentence of the serious scientific article -

"It may be possible to identify and utilize principles identified in organisms with advanced regenerative capacity, in order to activate dormant routines... to regrow limbs in humans."[10]

This article took us on a complete journey through the worlds of finger rehabilitation. We started with an employee in a toy store whose finger re-grows (or not, or yes) thanks to "fairy dust", we continued with children who are genuinely able to regrow their limbs and we ended up with rehabilitation facilities for frogs that can eventually reach humans as well.

For me, all these are just repetitions of variations we see in nature. We know that there are animals that can regrow their organs by reprogramming the cells in the area of ​​the injury. Once this fact is clear, there is no reason why we cannot reproduce it in humans as well. For this we will need a more advanced scientific understanding than the one that exists today regarding tissue restoration, and more advanced technologies in the field of genetic engineering (probably) or even in the transmission of messages to cells.

Will we get the scientific insights we need? The technologies we need?

If you think not, then you probably also believe that science and technology are not going to advance anywhere. that we have, in fact, reached the end of the road. Tens of thousands of researchers investing their days and nights in the field of tissue engineering, are not going to reach results of any kind. That millions of researchers in the field of artificial intelligence, which already produces for us computer models that describe the way the cells in the body work, are about to raise their hands and undergo vocational training as street cleaners (whose dignity is in its place, but most of them will not bring the breakthroughs we need).

All this, of course, is not going to happen. The researchers continue to explore vigorously, the engineers continue to develop new technologies for us, and the artificial intelligence only improves in its capabilities and jumps forward the science and technology in every field. It will take a real catastrophe - on the level of World War III and a bit more - to stop the progress in this area and in general.

The real question is: when will all these scientific and technological achievements come together in a way that will allow humans to regrow complex tissues? in a year? decade? fifty years?

I will leave it to the readers to try to answer the question, but here is a small recommendation from me: be optimistic.

Big things still await us... in the future.









[9] Specifically, in Science Advances magazine, which enjoys an impact factor of 14.136


post Scriptum. - Thanks to SparkBeyond, whose artificial intelligence engine helped in conducting the research and collecting and collating the relevant scientific articles. (Full disclosure: I work for a company)

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