PULLMAN, Wash. – The secret to youthful looks and scar repair may lie in the microscopic skin structures humans share with pigs and grizzly bears, but surprisingly not in monkeys.

These ridge-and-valley-like skin microstructures (called Lethe protuberances) were thought to form during fetal development, but researchers at Washington State University’s College of Veterinary Medicine have discovered that they actually develop shortly after birth and have identified key molecular signals that drive their development.

The survey results are Published in Nature magazinecould lead to new treatments aimed at reversing or slowing skin aging and improving wound and scar repair.

“These structures deteriorate with age. Now we know how they form and have a blueprint to guide future repair of the structures,” said Ryan Driskell, associate professor in the School of Veterinary Medicine’s Department of Molecular Biosciences and lead author of the paper. “Most scientists thought these skin bumps formed during early embryonic development, which explains why no one really understood their origin.”

Lethe’s ridges act like biological “Velcro,” Driskell said, helping to maintain elasticity and strength while anchoring the outer layer of skin, or epidermis, to the dermal layer below. These bumps flatten with age, making the skin thinner and more susceptible to sagging and damage.

Despite its importance, research has been held back for decades by a major obstacle: the wrong animal models.

“When most people look at the skin of different animals, they notice the differences in their fur. But the reticular ridges are beneath the surface of the skin, so it wasn’t until we looked closer that we discovered that animals with thicker skin, such as pigs, grizzly bears, and dolphins, have them just like we do,” said Sean Thompson, a doctoral student in Driskel’s lab and lead author of the study. “In contrast, common biomedical models of humans, such as mice and non-human primates, are furry and lack reticular ridges.”

Grizzly bears have provided evolutionary data suggesting that body size determines skin structure, but bears’ unique ecology has made it impossible to track the day-to-day development of their reticular ridges. This led the team to a pig with a developmental timeline that researchers could accurately monitor.

The research team worked with local farmers to collect skin tissue samples from pigs at different stages of development and showed that the reticular ridges eventually form after birth.

“We expected this structure to be established before birth, so it was a surprise to see it emerge afterwards,” Driskell said. “That timing changes the way we think about how skin structure is built and why it can impact later in life.”

Using advanced genetic mapping techniques, the research team also identified bone morphogenetic protein (BMP) signaling, a key biological pathway that is activated to form these structures. This pathway acts as a set of molecular instructions that guide how cells communicate and organize into complex tissues. As reticular ridges disappear with age, reactivating BMP signaling could help restore youthful skin and improve scar repair, as well as lead to new treatments for conditions such as psoriasis.

“The fact that BMP signaling drives web ridges is interesting because it has important translational potential,” said Maksim Plikas, a professor at the University of California, Irvine and co-author of the paper. “The use of BMP proteins has already been approved by the FDA for orthodontic applications, and the use of BMP proteins in aging skin and scars has been mapped.”

The discovery could also help improve livestock health and adaptability to different climates. Understanding how these traits are formed can help researchers explore ways to breed pigs and other livestock with skin characteristics suited to different conditions.

Driskell has applied for a provisional patent related to his team’s discovery.

The study involved a partnership between WSU’s Center for Bear Research, Education and Conservation and local farmers and producers, as well as clinical collaborators from the University of Washington Institute of Birth Defects and Spokane Dermatology. This was supported through the National Institutes of Health and the USDA Agricultural Research Service’s Resilient Livestock Initiative.