To investigate, yang and his lab to a deer farm in california where they collected samples of early antler tissue, which is primarily made up of skeletal stem cells. Antlers grow from the top down; as they grow, a reservoir of stem cells remains at the top of the antlers, continuing to proliferate. In early development, antler tissue is soft, making cell sampling an easy task for Yang and harmless for the buck. Only in the second stage of development does the antler mineralize and become rigid.
Back in the lab, the scientists used a variety of techniques to decipher the genetics behind antler growth, including analyzes of RNA, a molecule that helps carry out specific gene instructions, and gene knock-down and over-expression studies, which hinder gene function or rev up, respectively. Comparative RNA analyzes between stem cells in human antlers and human stem cells from bone marrow led to a collection of genes that seem to have a unique expression in antlers. From that pool, he narrowed the search by tampering with gene function, watching how different levels of gene expression expressed in mouse cells.
In mouse cells, Yang saw that when the clock was decommissioned, the bone tissue could grow quiet, just not as quickly; only when uhrf1 fully functional did the scientists see the rapid cell proliferation characteristics of antler growth. Likewise, when s100a10 was overexpressed, calcium deposits increased and the engineered cells more rapidly became mineralized.
It is worth studying just out of pure curiosity, but there is no doubt about it, "Yang said.
Applying antique genetics to humans
The researchers hope their insights into antler genes might inform new approaches to treating diseases like osteoporosis. In healthy bones, two types of cells – osteoblasts and osteoclasts – work as opposing forces. Osteoblasts produce new bone tissue, while osteoclasts break down old bone. The two cell types work in a yin and yang style to continuously form and degrade bone to maintain balanced bone structure. In osteoporosis, osteoclast function overtakes osteoblasts, and the bone starts to break down.
This allows for rapid bone regeneration in human beings such as osteoporosis, "Yang said.
Yang plans to continue researching multiple types of to confirm that clock and s100a10 back speedy antler growth across species. In addition, in human cell lines, while continuing to parse how ufh1 and s100a10 work on a molecular level, looking into possible functional pathways.
"There's a lot of work being done, but this could be a unique model of bone regeneration, and our initial work has started to lay a foundation for future studies," Yang said.
Other Stanford co-authors of the paper are postdoctoral scholars Dan Wang, PhD, and Bin Zhang, PhD; Norma Neff, PhD, former DNA sequencing core director; former undergraduate researcher Rashmi Sharma; William Maloney, MD, the Boswell Professor of Orthopedic Surgery and Chair; and professor of bioengineering and applied physics Stephen Quake, PhD.
Peter Yang is a member of Stanford Bio-X, the Stanford Cardiovascular Institute, Stanford ChEM-H, the Stanford Child Health Research Institute and the Stanford Neurosciences Institute,
Scientists from the Tenth People's Hospital of Tongji University, Calico Life Sciences and the State Key Lab for Molecular Biology of Special Economic Animals also contributed to the study.
The Department of Defense, the Boswell Foundation and the AO Foundation, grants R01AR057837, R01AR057837, R01DE021468 and S10RR027431.
Stanford's Department of Orthopedic Surgery also supported the work.