If you lose your teeth, you can use medicine to grow them back. This new research may benefit many people in the future.

Maybe the teeth that fall out can grow back in the future!

When I get old and all my teeth fall out, I will definitely start to envy sharks, because sharks' teeth have the ability to regenerate . Even if their teeth fall out, they can still continue to grow new teeth as replacements.

Unfortunately, mammals, including humans, have long lost the ability to regenerate teeth during evolution, because the eating habits of mammals require us to have a more complex tooth structure than fish, and losing the ability to regenerate teeth is a trade-off we must make for this. Some rodents, such as mice, only grow one set of teeth in their lifetime. Once they lose a tooth due to injury or disease, they lose that tooth forever and will not grow a new one.

The situation for us humans is a little better, because we still have one chance to replace our teeth . When we are infants, we first grow deciduous teeth, which accompany us as we grow up, and then gradually fall out and are gradually replaced by new permanent teeth. These permanent teeth will accompany us for the rest of our lives. If we accidentally lose permanent teeth, there will be no new teeth growing to replace them (this is generally the case, but we will mention some special cases in which permanent teeth continue to grow later).

Copyrighted images of children changing teeth. Reproduction and use may cause copyright disputes.

Currently, people who are missing teeth due to various problems can only be treated and supplemented through dentures, dental implants and other methods, but a new drug recently developed by Japanese scientists is expected to allow patients with missing teeth to grow new teeth directly.

One gene can influence the number of teeth

" It's every dentist's dream to help people grow new teeth . I've been working on this idea since I was a graduate student," said Katsuyuki Takahashi, the researcher who led the study and chief researcher and director of dental and oral surgery at Kitano Hospital, Osaka City Institute of Medical Research, in an interview with Japan's Mainichi Shimbun.

There are many people in the world who are born with missing teeth. These people will struggle with basic abilities such as chewing, swallowing and speaking from an early age , which can have a huge negative impact on their growth. Congenital tooth loss can be caused by genetic defects or environmental factors in early development, such as viral infections.

Human teeth composition Image source: wikimedia

Takahashi has been looking for ways to treat these congenitally toothless patients. After obtaining a bachelor's degree in dentistry, Takahashi came to Kyoto University in Japan in 1991 to pursue graduate studies in molecular biology, and then went to the United States to study.

At that time, researchers around the world have discovered some genes related to tooth loss. Once these genes are deleted in mice, they will lose their teeth. This gave Takahashi an idea: " Just a change in a gene can affect the number of teeth . If we take it as a research target, it may be possible to change the number of human teeth."

After the replacement of teeth, it is possible to grow teeth

Around 2005, Takahashi returned to Japan to continue his research at Kyoto University, and soon it seemed he had found the answer in a disorder that was the opposite of tooth loss: some humans and mammals have more teeth than normal, a condition called hyperdontia, which may be caused by a genetic defect.

Image of a patient with "too many teeth": Takahashi et al, 2013

Previously, researchers found that mice lacking the gene for synthesizing the USAG-1 protein had an increased number of teeth . After years of research, Takahashi's research team has figured out the mechanism. They believe that the extra teeth of many patients with "excessive teeth" may come from the human "third dentition".

Deciduous teeth belong to the "first dentition" and permanent teeth (except molars) belong to the "second dentition". Normally, no more teeth will grow after these two rows of teeth. However, some scientists believe that humans have the potential to continue growing teeth in addition to deciduous teeth and permanent teeth. Some studies have found that humans and some mammals have the potential to develop epithelial anlage for new teeth on the tongue side of permanent teeth, but under normal circumstances, they will gradually die during growth and will not actually develop into new teeth.

Humans and mice have the potential to grow additional dentition. Image credit: Takahashi et al, 2020

The function of the USAG-1 protein is to inhibit the growth of the "third dentition" . It can inhibit two crucial proteins in the process of tooth development: bone morphogenetic protein (BMP) and Wnt. Many people or mice with "excessive teeth" symptoms are due to defects in the gene encoding USAG-1. BMP and Wnt signals cannot be effectively inhibited, and some teeth belonging to the new dentition grow out .

The idea of ​​allowing edentulous patients to grow teeth by inhibiting the function of USAG-1 Image source: Takahashi et al, 2020

Takahashi realized that if the function of USAG-1 protein could be artificially targeted and blocked, would there be a chance for people with missing teeth to grow teeth again? Therefore, in a study published in Science Advances in 2018, Takahashi's team successfully developed a neutralizing antibody that can inhibit the binding of USAG-1 to BMP, and successfully made mice and ferrets grow normal teeth without any side effects.

Ferret growing new teeth. Image credit: Takahashi et al, 2018

Now, they have further developed TR035, a tooth growth drug for human use , which has been approved by relevant Japanese agencies and will conduct Phase I clinical trials from September 2024 to August 2025. They will recruit men aged 30 to 65 with one or more missing molars for a single-dose, double-blind, placebo-controlled trial to confirm the safety of the drug. Next, they will recruit patients aged 2 to 7 with 4 or more congenitally missing teeth to explore the effect of the drug.

Research progress Image source: Ravi et al, 2023

According to the Daily News, the research team believes that this drug will not only help people born without teeth grow teeth in the future, but also help those who have lost teeth due to tooth decay or injury to grow teeth again. According to the plan, the drug is expected to be available on the market in 2030.

I hope it can help many people in the future. Maybe when I get old, I won't have to envy sharks anymore.

References

[1]https://www.kitano-hp.or.jp/info/20240503

[2]https://www.kitano-hp.or.jp/section/dental/clinical-trial

[3]https://www.sciencedirect.com/science/article/pii/S2352320423000044?via%3Dihub

[4]https://inflammregen.biomedcentral.com/articles/10.1186/s41232-020-00130-x

[5]https://mainichi.jp/english/articles/20230609/p2a/00m/0sc/026000c

[6]https://mainichi.jp/english/articles/20240503/p2a/00m/0sc/012000c

[7]https://www.intechopen.com/chapters/43101

[8]https://www.science.org/doi/10.1126/sciadv.abf1798#elettersSection

[9]https://journals.sagepub.com/doi/10.1177/0022034519858282#bibr28-0022034519858282

[10]https://www.sciencedirect.com/science/article/abs/pii/S1084952113001420?via%3Dihub

Planning and production

Source: Global Science (ID: huanqiukexue)

Author: Dong Yuan

Editor: Zhong Yanping

Proofread by Xu Lailinlin

The cover image and the images in this article are from the copyright library

Reprinting may lead to copyright disputes