BackA burst of light
A laser fired for a few minutes can regrow teethand perhaps a variety of other tissues
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They have occupied 14 years of Praveen Arany’s life, but the life-giving molecules last no more than a nano second, or about a billionth of a second.
These short-lived molecules are born—or die just as quickly—in the course of a five-minute burst of laser light, setting in motion a complex series of events (described on Thursday in the journal Science Translational Medicine) that ends 12 weeks later with part of a regrown tooth in rats.
Arany, 37, who got his basic dental degree from Belgaum, Karnataka, and his PhD from Harvard University, is a clinical investigator at the US National Institutes of Health (NIH), where he has now begun the groundwork for clinical trials—translating his technique of growing dentin, one of the hard tissues that constitutes teeth, from mice to humans. If it works, it could make fillings and crowns obsolete.
“We are very excited," Arany, the lead researcher on the study and a retired Indian naval officer’s son, told me. The excitement stems from the fact that the US Food and Drug Administration (FDA) clears with relative ease medical devices that are not biological, or based on living matter, which throws up significant regulatory and practical barriers.
Recent research involving tissue regeneration focuses on stem, or master, cells, an area of great promise, controversy and difficulty. The cells are mostly manipulated in petri dishes, dabbed with molecules called growth factors and reintroduced into the body to become specialized tissue. Arany and his colleagues devised a technique that uses a laser to directly stimulate growth factors inside dental tissue. When laser light hits dentin, it leads to the birth of reactive oxygen species (ROS), molecules that live for a fraction of a second, long enough to urge amino acids—genetic building blocks—in a protein called transforming growth factor-beta (TGF-b) to start the process of rebuilding tissue.
Arany and his colleagues are focused on teeth, but the implications are wider. “(They) have now built on work of others to demonstrate use of lasers to activate proteins that can direct stem cells to produce new tissue," said Jeffrey Karp, co-director of the Centre for Regenerative Therapeutics of Harvard’s Brigham and Women’s Hospital who is not associated with the study. “Use of light as part of a regenerative therapy approach could have broad implications and be rapidly translated to the clinic given its likelihood to be safely employed in many clinical settings."
Arany’s long-time collaborator and mentor concurs. “Beyond that application (tooth defects), this approach may also be useful for the regeneration of a variety of other tissues where TGF-b plays a significant role, including skin regeneration," David Mooney, a Harvard professor of bioengineering, explained to me. That regeneration, if it can be done with lasers, could include heart, lung and skin tissue, all of which have TGF-b. It plays critical roles in many biological processes, including the differentiation of cells into specific tissues, wound healing and various human diseases.
The process sounds simple. It is anything but. As Arany’s long road to success indicates, the details are critical. His research first formed part of a dissertation submitted to the Rajiv Gandhi University of Health Sciences, Bangalore, and he confesses that even after recent success his only diversion from work is family and a bit of badminton (he once played for Harvard).
The laser Arany and colleagues use is finely calibrated. If it isn’t it could easily be destructive or useless. For instance, the ROS born in laser light, as he explained, “either degrade or react very quickly".
The use of concentrated beams of light, lasers, as a cutting and healing tool in medicine spans nearly half a century. Laser equipment could once fill a room, now many are hand-held. Their great advantage is precise and bloodless surgery—lasers cauterize as they cut. They clear clogged arteries, reshape corneas and rejoin detached retinas, remove birthmarks and in dentistry, drilling into cavities and root canals.
However, getting light to do your bidding in creating dentin entails knowledge fetched across disciplines. Arany’s work requires, as is often the case these days, a melding of medical disciplines. He is a dentist, biologist, pathologist and tissue engineer. He did post-doctoral work at the Indian Institute of Science, Bangalore, the US National Cancer Institute in Maryland and Harvard. While at Harvard, he acquired three degrees, which the university allows under its integrated life sciences programme. After cutting his teeth—so to say—working at a laboratory run by Harvard’s Mooney, Arany now runs a lab of his own at NIH, where he hopes those 14 years of research will finally make it to the market.
Light is already a great healer. If Arany and his colleagues have their way, it may not be long before it becomes a spark for regenerating life.
Samar Halarnkar is a Bangalore-based journalist. This is a fortnightly column that explores the cutting edge of science and technology. Comments are welcome at frontiermail@livemint.com. To read Samar Halarnkar’s previous columns, go to www.livemint.com/frontiermail -
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