For centuries, the inability to regrow lost limbs or repair damaged joints has been treated as a fixed biological fact for humans and other mammals. A new study from Texas A&M suggests it may not be.
Researchers at the Texas A&M College of Veterinary Medicine and Biomedical Sciences developed a sequential treatment that triggered the regeneration of bone, joint structures and ligaments in mammals. The results, published in Nature Communications, are not perfect. But the team believes the approach could reduce scarring and improve tissue repair after amputations far sooner than full limb regeneration becomes possible.
The central question the study addresses is one Dr. Ken Muneoka, a professor in the Department of Veterinary Physiology and Pharmacology, has spent his career on. "Why some animals can regenerate and others, particularly humans, can't is a big question that has been asked since Aristotle," he said.
The answer, his team found, may lie not in what humans lack but in what their cells are being told to do.
When mammals are injured, cells called fibroblasts rush to seal the wound. They form scar tissue quickly, which helps the animal survive. In regenerative species like salamanders, those same cell types organize differently. Instead of forming scar tissue, they build a blastema, a temporary structure that acts as a kind of biological scaffold for regrowing lost tissue. "It's as if these cells can move in two different directions," Muneoka said. "They could either make a scar or make a blastema."
The Texas A&M team designed a treatment to redirect that decision. The first step applied fibroblast growth factor 2, known as FGF2, after a wound had already closed and initial healing was complete. This timing was deliberate. The researchers let the body finish its normal response, then intervened. FGF2 stimulated the formation of a blastema-like structure, something that does not naturally occur in mammals after this kind of injury.
Several days later, a second growth factor was applied: bone morphogenetic protein 2, or BMP2. This signal told the newly organized cells what to build. "You first shift the cells away from scarring," Muneoka said, "and then you provide the signals that tell them what to build."
One of the more striking implications of the research is what it does not require. Many current approaches in regenerative medicine focus on introducing external stem cells to an injury site. This study suggests that may be unnecessary. The cells already present in the wound can be redirected. The capacity for regeneration, the researchers argue, is not absent in mammals. It is simply suppressed.
The study also challenges a long-standing assumption that regenerative ability is unique to certain species due to some fundamental genetic difference. If mammalian fibroblasts can be coaxed into blastema formation through targeted growth factor signaling, the gap between salamanders and humans may be a matter of biochemical instruction rather than biological impossibility.
Muneoka and his colleagues acknowledge the results are incomplete. Regenerated structures were not perfect replicas of the original tissue. But the team sees near-term clinical value in the approach even before full regeneration is achievable. Reducing fibrosis and improving the quality of healing after traumatic injury or amputation are meaningful goals in their own right. The two-step method offers a potential path toward both.
