Lessons from antlers

Yunzhi Peter Yang, PhD, professor of orthopaedic surgery, envisions a future where surgeons can print the structures needed to rebuild the human skeleton.

His lab develops 3D-printing technology to combine biodegradable scaffolds that have bonelike mechanical stability with soft hydrogel components loaded with stem cells or growth factors.

He is designing these systems to recapitulate the spatial organization of cells involved in skeleton formation, biological cues within native tissues — including bone, tendon and muscle — and complex tissue interfaces such as bone-tendon and bone-cartilage junctions.

He has collaborated with Stuart Goodman, MD, PhD, the Robert L. and Mary Ellenburg Professor in Surgery, for nearly a decade on National Institutes of Health-funded grants to study biodegradable metals — an effort to build implants that do their structural job and then dissolve, leaving nothing behind to complicate future surgery. 

This approach has already moved from bench to turf: When a young racehorse in Kentucky developed a life-threatening bone tumor in its jaw and faced euthanasia, Yang’s team custom-fabricated a device to fill the defect.

Six months later, the bone had healed completely, and the horse raced competitively. The Food and Drug Administration has since given the technology Breakthrough Device Designation — fast-tracking the review process for promising medical devices addressing serious unmet clinical needs. 

Yang has also spent over a decade studying deer antlers — among the fastest-growing tissues in nature, capable of adding an inch per day — whose stem cells reside in the periosteum, the same bone-encasing membrane that gives bone its regenerative advantage over cartilage.

He believes the mechanisms behind antler growth, which is both extraordinarily rapid and precisely controlled, holds clues for human tissue repair. “If we can discover a mechanism where they grow fast but without forming cancer, that would be huge,” he said. 

His goal is a hybrid bioprinting system able to fabricate entire limbs — skin, muscle, cartilage and bone together — tailored to individual patients.