The ability to regenerate lost body parts is unevenly distributed among higher organisms. Among vertebrates, some amphibians are able to replace lost limbs completely, while mammals are unable to regenerate complex appendages. The only exception to this rule is the annual replacement of deer antlers. The annual regrowth of these structures is the only example of regeneration of a complete, anatomically complex appendage in a mammal, and antlers are therefore of high interest to regeneration biologists.
The epimorphic regeneration of appendages may involve progenitor cells created through reprogramming of differentiated cells or through the activation of resident stem cells. Reporting in this week’s PLoS ONE in a study funded by the German Research Society, Hans J. Rolf and colleagues from the University of Goettingen and University of Hildesheim (Germany) emphasize that deer antler growth and regeneration might be reduced to a stem cell-based process.
Their results strongly support the view that the growth of primary antlers as well as the annual process of antler regeneration depend on the periodic activation of mesenchymal stem cells. Understanding the mechanisms behind this unique regeneration process could have an important impact on the emerging field of regenerative medicine.
Deer antlers are cast and regenerated from permanent bony protuberances of the frontal bones, called pedicles. After antler casting, the bone wound on the top of the pedicle is bordered by the pedicle periosteum and the pedicle skin. Wound healing and epithelialization as well as formation of an antler bud occur very rapidly and, in larger species like the red deer (Cervus elaphus), the new antler elongates at an average rate of about 1 cm per day.
As early as the second half of the 20th century antler biologists recognized that exploring the mechanisms of antler regeneration may provide crucial insights to better understand why mammals are unable to regenerate amputated limbs. For years, the source of the cells that give rise to the regenerating antler has been a matter of controversy. Recently, it has been hypothesized that antler regeneration is a stem cell based process and most workers in the field consider the periosteum of the pedicle to be the source of the cells forming the regenerating antler.
However, thus far direct evidence for the existence of stem/progenitor cells in the pedicle periosteum and the growing antler was lacking. As part of an ongoing research project, Rolf and colleagues searched for the presence of cells positive for known stem/progenitor cell markers in pedicles and growing antlers of fallow deer (Dama dama). In addition, they isolated and cultivated stem/progenitor cells derived from the deer antler/pedicle and investigated their proliferation and differentiation properties.
The most important finding of the present study is the demonstration of STRO-1+ cells in different locations of the primary and regenerating antler as well as in the pedicle of fallow deer. The experiments described by Rolf and colleagues strongly support the view that the annual antler regeneration indeed represents a stem cell-based process. Their results are consistent with the hypothesis that the regenerating antler is build up by the progeny of mesenchymal stem/progenitor cells located in the cambial layer of the pedicle periosteum.
It has recently been shown that stem cell populations exist in "niches" — specific anatomical locations that regulate how the stem cells participate in tissue generation, maintenance and repair. Rolf and colleagues assume that such a "stem cell niche" is located in the cambial layer of the periosteum and that the regeneration of antlers is dependent on the periodic activation of these stem cells.
Even though different groups have recently found clues to the presence of stem cells/progenitor cells in the pedicle periosteum as well as in primary and regenerating antlers, the present paper for the first time provided crucial evidence for the existence of stem cells in these areas. It has been shown that fallow deer antler cells positive for different stem cell markers can be sorted and cultivated as “pure” cultures.
These cells were able to differentiate in vitro along the osteogenic and adipogenic lineages. Together, the findings of the present study suggest that not only limited tissue regeneration, but also extensive appendage regeneration in a postnatal mammal can occur as a stem cell-based process. Therefore, deer antlers as a research model might be of great interest not only for veterinarians or deer biologists but also for stem cell researchers, tissue engineers, cell biologists and basic researchers in medical disciplines.
Citation: Rolf HJ, Kierdorf U, Kierdorf H, Schulz J, Seymour N, et al. (2008) Localization and Characterization of STRO-1+ Cells in the Deer Pedicle and Regenerating Antler. PLoS ONE 3(4): e2064. doi:10.1371/journal.pone.0002064
Source: Public Library of Science
Related stories:
Want a reason to love your lower belly fat? It's rich in stem cells
Fat removed from the lower abdomen and inner thigh through liposuction was found to be an excellent source of stem cells, with higher stem cell concentrations than other areas of the body, reports a Brazilian-based study in August's
Plastic and Reconstructive Surgery, the official medical journal of the American Society of Plastic Surgeons (ASPS). This is the first study of its kind to examine whether fat tissues from different areas of the body vary in stem cell concentration.
Scientists identify cells for spinal-cord repair
A researcher at MIT's Picower Institute for Learning and Memory has pinpointed stem cells within the spinal cord that, if persuaded to differentiate into more healing cells and fewer scarring cells following an injury, may lead to a new, non-surgical treatment for debilitating spinal-cord injuries.
Researchers prove that insulin-producing cells can give rise to stem-like cells in-vitro
The question of whether insulin-producing cells of the pancreas can regenerate is key to our understanding of diabetes, and to the further development of regenerative therapies against the disease. Dr Rosenberg from the McGill University Health Centre (MUHC) and McGill University together with Dr Bernard Massie from the Centre hospitalier de l'Université de Montréal (CHUM) have just concluded that they can. The results of their study have been published in the July issue of the journal
Laboratory Investigation.
The genetics of the white horse unraveled
The white horse is an icon for dignity which has had a huge impact on human culture across the world. An international team led by researchers at Uppsala University has now identified the mutation causing this spectacular trait and show that white horses carry an identical mutation that can be traced back to a common ancestor that lived thousands of years ago. The study is interesting for medical research since this mutation also enhance the risk for melanoma. The paper is published on July 20 on the website of
Nature Genetics.
Stem Cell Chicken and Egg Debate Moves to Unlikely Arena: The Testes
Logic says it has to be the niche. As air and water preceded life, so the niche, that hospitable environment that shelters adult stem cells in many tissues and provides factors necessary to keep them young and vital, must have emerged before its stem cell dependents.
Researchers grow human blood vessels in mice from adult progenitor cells
For the first time, researchers have successfully grown functional human blood vessels in mice using cells from adult human donors — an important step in developing clinical strategies to grow tissue, researchers report in
Circulation Research: Journal of the American Heart Association.
Study identifies cells for spinal-cord repair
(PhysOrg.com) -- A researcher at MIT’s Picower Institute for Learning and Memory has pinpointed stem cells within the spinal cord that, if persuaded to differentiate into more healing cells and fewer scarring cells following an injury, may lead to a new, non-surgical treatment for debilitating spinal-cord injuries.
Probing Question: Fishhooks of addiction
When the American writer Theodore Roethke taught at Penn State from 1936 to 1943, he was known for three things: being a good poet, coaching the men’s tennis team, and falling down drunk, perhaps the latter more than the former. Roethke, a brilliant and tortured man, knew well the seduction of drink and the agony of addiction. In his poem “Journey Into the Interior,” Roethke writes, “In the long journey out of the self, / There are many detours, washed-out interrupted raw places / Where the shale slides dangerously / And the back wheels hang almost over the edge / At the sudden veering, the moment of turning.”
