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Histological studies of bone formation during pedicle restoration and early antler regeneration in roe deer and fallow deer.

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THE ANATOMICAL RECORD PART A 273A:741–751 (2003)
Histological Studies of Bone
Formation During Pedicle
Restoration and Early Antler
Regeneration in Roe Deer
and Fallow Deer
UWE KIERDORF,1* ELKE STOFFELS,2 DIETER STOFFELS,2
HORST KIERDORF,3 THOMAS SZUWART,4 AND GÜNTER CLEMEN2
1
Institute of General and Systematic Zoology, Justus Liebig University of Giessen,
Giessen, Germany
2
Institute of Animal Evolution and Ecology, University of Münster,
Münster, Germany
3
Department of Biology, University of Hildesheim, Hildesheim, Germany
4
Clinical Anatomy, Anatomical Institute, University of Münster, Münster, Germany
ABSTRACT
The purpose of the present study was to examine the process of bone formation in the regenerating cranial
appendages of roe deer (Capreolus capreolus) and fallow deer (Dama dama) during the early postcasting period. After
the antlers are cast, osteoclastic and osteoblastic activities lead to a smoothing of the pedicle’s separation surface, a
strengthening of the pedicle bone, and a partial restoration of the distal pedicle portion that was lost along with the cast
antler. Initially, bone formation occurs by intramembranous ossification, but early during the regeneration process
cartilage is formed at the tips of the cranial appendages, and is subsequently replaced by bone in a process of
endochodral ossification. Shortly after the antlers are cast, the cambium layer of the periosteum in the distal pedicle is
markedly enlarged, which suggests that the periosteum serves as a cell source for the bone-forming tissue covering the
exposed pedicle bone. The histological findings of our study are consistent with the view that the bony component of the
regenerating cranial appendages of deer is largely derived from the pedicle periosteum. Based on findings in other bone
systems, we speculate that stem cells that can undergo both osteogenic and chondrogenic differentiation are present in
the pedicle periosteum. The early onset of chondrogenesis in the regeneration process is regarded as an adaptation to
the necessity of producing a huge volume of bone within a short period. This parallels the situation in other cases of
chondrogenesis in membrane bones. Anat Rec Part A 273A:741–751, 2003. © 2003 Wiley-Liss, Inc.
Key words: deer; antler; pedicle; regeneration; periosteum; intramembranous ossification; endochondral ossification; cartilage
Antlers are periodically cast and regrown cephalic appendages of deer. Since the replacement of antlers constitutes the only case of regeneration of a complete bony
appendage in mammals (Goss, 1984, 1992; Bubenik,
2001), this developmental process deserves special attention. Antlers do not grow directly from the top of the deer
skull; rather, they are cast and regenerate from the apices
of permanent protuberances of the frontal bones, the
pedicles.
There is considerable evidence supporting the notion
that the timing of the antler cycle is closely linked to
seasonal fluctuations in concentrations of circulating sex
steroids—particularly testosterone (Wislocki et al., 1947;
Goss, 1968; Suttie et al., 1995). Thus, premature casting of
hard antlers can be induced by castration (Wislocki et al.,
1947; Lincoln, 1971; Goss et al., 1992; Kierdorf et al.,
©
2003 WILEY-LISS, INC.
1995), as well as by the administration of compounds that
inhibit LH and thus testosterone release (medroxyprogesterone acetate), or interfere with both the release of testosterone and its action at the receptor level (cyproterone
acetate) (Muir et al., 1982; Bubenik et al., 1987; Kierdorf
*Correspondence to: Uwe Kierdorf, Institute of General and
Systematic Zoology, Justus Liebig University of Giessen, Heinrich-Buff-Ring 26-32, D-35392 Giessen, Germany.
E-mail: kierdorf@lindlar.de
Received 4 November 2002; Accepted 5 May 2003
DOI 10.1002/ar.a.10082
742
KIERDORF ET AL.
et al., 1993; Suttie et al., 1995). On the other hand, antler
casting can be postponed by administration of testosterone or estradiol to deer carrying hard antlers (Goss, 1968).
These findings suggest that antler casting is triggered by
a decrease in testosterone levels. Antler casting itself is
preceded by the action of numerous osteoclasts that erode
the bony connection between the antler and pedicle along
the future separation plane (Goss et al., 1992).
The histogenesis of antlers during the more advanced
stages of antler regeneration has been investigated in
considerable detail. These studies demonstrated that antler bone is formed by both endochondral and intramembranous ossification (Gruber, 1937; Banks, 1974; Banks
and Newbrey, 1983a, b; Price et al., 1996). Antler elongation occurs in distal growth zones, where mesenchymal
cells sequentially proliferate and differentiate into chondroblasts and chondrocytes. The highly vascularized antler cartilage is then mineralized, eroded by chondro-/osteoclasts, and replaced by bone. Thus, bone is formed by an
endochondral process. However, at the periphery of the
antler, a sleeve of bone is formed via direct, intramembranous ossification by osteoblasts derived from the osteogenic (cambium) layer of the periosteum.
So far, less attention has been given to the histogenetic
processes that occur shortly after antlers are cast, i.e.,
during the closure of the casting wound at the apex of the
pedicle and the earliest stages of antler regrowth (Gruber,
1937; Wislocki, 1942; Waldo and Wislocki, 1951; Goss et
al., 1992). However, a detailed knowledge of these events
is crucial to obtain a better understanding of antler regeneration, and to compare it with other restorative or regenerative processes in vertebrates. Therefore, the purpose of
the present study was to characterize the process of bone
formation during pedicle restoration and early antler regeneration, using light and electron microscopy.
MATERIALS AND METHODS
Animals and Tissue Sampling
The tissues studied originated from four adult roe bucks
(Capreolus capreolus; specimens R1–R4, used only for
light microscopy), and one juvenile fallow buck (Dama
dama; specimen F, used for light and electron microscopy)
that were killed quite shortly after their antlers were cast
(but at different developmental stages; for details, see the
Results section). The four roe bucks were wild animals
that were shot during hunting operations outside the normal hunting season (normally, roe bucks are shot only
during the hard antler stage). Their heads were cut off and
kept frozen until further processing for light microscopy.
The fallow buck was a farm animal that was killed by a
shot in the head and subsequent exsanguination after its
first (spike) antlers were cast. The tissues from this buck
were sampled and fixed immediately after death for both
light and electron microscopy.
In the roe bucks, the pedicles and a portion of the
adjacent frontal region were removed from the heads with
a bone saw, and fixed by immersion in either 3.5% buffered formalin or Bouin’s solution. In two of the animals,
the complete pedicles were cut in the median-sagittal
plane. In the other two specimens, the pedicles were longitudinally split into four segments by two sections oriented in a median-sagittal and a coronal plane, respectively, using an electric saw equipped with a water-cooled
diamond blade. Afterwards, the pedicle segments were
removed from the skull by a horizontal section. In order
not to dislodge the overlying soft tissues from the pedicle
bone during sampling, incisions down to the bone were
made with a scalpel prior to sawing. These incisions were
kept open during sampling, and care was taken to ensure
that the saw cuts exactly followed the incision lines.
Tissue samples from the fallow buck were obtained in a
similar way as described for the roe deer. Sectioning was
performed under constant rinsing with Sørensen’s buffer
(pH 7.4). For light microscopy, a medial and a lateral
pedicle half were fixed in Bouin’s solution. The remaining
two halves from the contralateral side, designated for
electron microscopy, were each further sectioned into
smaller pieces and fixed in a cold (4°C), phosphate-buffered (pH 7.4) paraformaldehyde-glutaraldehyde-osmium
mixture (Hatae et al., 1986).
Light Microscopy
The tissue samples were decalcified in a saturated aqueous EDTA solution for up to 8 weeks, followed by thorough
rinsing first in tap water and then in distilled water. Part
of the material was shock-frozen (–15°C) and sectioned at
8 –10 ␮m with a frozen-section microtome (type 1206;
Reichert-Jung, Nussloch, Germany). The remaining samples were dehydrated in a graded series of isopropanol,
transferred into butanol, and embedded in paraplast wax
or fibrowax (Plano Co., Wetzlar, Germany). The embedded
tissue blocks were sectioned at 6 –10 ␮m, and the sections
stained with either hemalum-eosin (HE), Heidenhain’s
azan, or alcian blue (pH 2.5)-PAS. Photographs of the
stained sections were taken with a photomicroscope (Axioskop 2, Zeiss, Jena, Germany).
Electron Microscopy
Tissue samples for transmission electron microscopy
(TEM) were thoroughly rinsed with Sørensen’s buffer, dehydrated in a graded series of ethanol, transferred into
acetone, and embedded in Durcupan (Fluka Chemie,
Deisenhofen, Germany). Semithin sections (1–2 ␮m) were
cut with an ultramicrotome (Reichert-Jung Ultracut),
stained with a 1% toluidine blue-borax solution, and studied by light microscopy. Ultrathin sections were cut with
diamond knives, stained with lead citrate (5 min) and
uranyl acetate (30 min), and studied with a Zeiss EM 900
transmission electron microscope, operated at an accelerating voltage of 50 keV.
RESULTS
Specimens R1 and R2 (Largely Unhealed
Casting Wound)
Since the findings in these two specimens were similar,
they are described together. Healing of the casting wounds
had just started in the peripheral portions of the pedicles
in both bucks; however, most of the top of the bony pedicle
was still a wound area covered by a scab (Fig. 1a). Between the scab and the pedicle bone, a fibrocellular tissue
(granulation tissue) was present. This tissue layer was
continuous with the connective tissue in the marrow
spaces between the spicules of pedicle bone. Numerous
leukocytes were present in the scab as well as in the
granulation tissue, especially its distal portion. The skin
bordering on the casting wound formed a tumescent rim.
Starting from this rim, the epidermis had just begun to
reepithelialize the wound area (Fig. 1a). At the leading
edge, a thin epidermal sheet was migrating beneath the
PEDICLE RESTORATION AND ANTLER REGENERATION
Fig. 1. Pedicles of roe bucks shortly after antler casting. a: Separation surface of pedicle with numerous, often pointed bone spicules
(asterisks). A layer of granulation tissue (G) is present between the scab
(S, partially lost during histological processing) and the pedicle bone.
The epidermis (E) has just begun to reepithelialize the wound area. C,
cambium layer of pedicle periosteum; D, dermis; arrow, sebaceous
gland; arrowhead, epidermal papilla. Specimen R1: HE (⫻26, bar ⫽ 500
743
␮m). b: Peripheral area of pedicle bone. Bundles of collagen fibers
(Sharpey’s fibers, arrows) connect periosteum and pedicle bone. C,
cambium layer of pedicle periosteum; F, fibrous layer of pedicle periosteum; P, pedicle bone. Specimen R2: HE (⫻105, bar ⫽ 100 ␮m). c:
Resorption of pedicle bone (asterisks) by osteoclasts (arrowheads).
Specimen R1: HE (⫻83, bar ⫽ 100 ␮m).
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KIERDORF ET AL.
scab. In this region, the epidermis did not possess papillae; however, closely behind the migration front, epidermal papillae were already present that projected into the
underlying tissue (Fig. 1a). Also, new hair follicles and
sebaceous glands were formed. As is typical of antler velvet, no arrector pili muscles were associated with the hair
follicles.
The separation surfaces of the bony pedicles were uneven, with numerous projecting osseous spicules (Fig. 1a).
The pedicle stumps consisted of lamellar bone (Fig. 1b). In
the distal pedicle portion, numerous multinucleated osteoclasts were observed that were situated in Howship’s
lacunae and resorbing the pedicle bone (Fig. 1c). The marrow spaces in the distal pedicle were enlarged. No distinct
boundary existed between the connective tissue of the
marrow spaces deeper within the pedicle and that located
in the distal pedicle portion.
The thickness of the periosteum lining the pedicle bone
(especially that of the inner cambium layer) was markedly
increased in the distal compared to the proximal pedicle
portion (Fig. 1a and b). In more proximal pedicle portions,
bundles of collagen fibers (Sharpey’s fibers) connected
periosteum and bone (Fig. 1b). Bone resorption was observed also along the pedicle periphery, especially in specimen R2.
Specimen R3 (Early Pedicle Restoration)
In this specimen, the bony pedicle was already fully
covered by newly formed velvet skin, which consisted of a
multilayered epidermis and a dermis (Fig. 2a). However,
overt antler regrowth had not yet started. Beneath the
regenerated skin at the pedicle top was a cell- and fiberrich mesenchymal tissue, which was thicker in peripheral
areas than in more central ones, and was peripherally
continuous with the pedicle periosteum (Fig. 2a and b).
At the separation surface of the pedicle, the osseous
projections were much shorter and less pointed than in
specimens R1 and R2 (Fig. 2a). This smoothing of the bone
surface had apparently been brought about by combined
osteoclastic and osteoblastic activities. A few active osteoclasts were still present in the distal pedicle bone. However, the remaining bone surface was covered by osteoblasts, which had laid down a thin layer of new bone onto
the surface of the pedicle bone. Evidence for this consisted
of a seam of osteoid and the occurrence of osteocytes,
which had apparently just become incorporated into the
bone matrix (Fig. 2b). A few places also showed the formation of new, slender, osseous trabeculae extending from
the much thicker trabeculae of the pedicle stump (Fig. 2b).
As in specimens R1 and R2, large marrow spaces were
present in the distal pedicle bone (Fig. 2a). Some bone
formation was also observed along the sides of the pedicle.
In all cases, the new bone was formed by intramembranous ossification, and no signs of chondrogenesis were
observed.
Specimen F (Advanced Stage of Pedicle
Restoration)
Wound healing in this individual was almost complete.
Except for a scab-covered central area (approximately 5
mm in diameter), the pedicle top was covered by newly
formed velvet skin. The former separation surface was
slightly concave (Fig. 3a). In the distal pedicle bone, the
marrow spaces between the osseous trabeculae were enlarged.
The relatively thick osseous trabeculae of the pedicle
stump were continuous with much thinner, newly formed
trabeculae (Fig. 3a and b). The osteoid secreted by the
osteoblasts lining these newly formed trabeculae (Fig. 3c)
was undergoing rapid mineralization, and cells were observed that had just become entrapped in the collagenrich bone matrix as osteocytes (Fig. 3d). By this appositional bone formation, the trabeculae increased in
thickness. Occasionally, multinucleated osteoclasts eroding the newly formed bone were also observed. Thus, osteoblastic and osteoclastic activities occurred simultaneously.
The intertrabecular mesenchymal tissue contained bundles of collagen fibers oriented parallel to the slender
trabeculae, as well as numerous capillaries (Fig. 3c and e).
The newly formed osseous trabeculae were mainly oriented in a vertical direction (Fig. 3b and c).
Electron microscopy showed that the osteoblasts lining
the newly formed osseous trabeculae possessed an acentric nucleus consisting mainly of euchromatin, a well developed rough endoplasmic reticulum, Golgi vesicles and
secondary lysosomes, numerous mitochondria, and a
meshwork of intermediary filaments (Fig. 4a). The cells
were in contact with each other by long, slender processes.
The extracellular matrix contained high numbers of collagen fibers, and numerous mineralization foci were observed (Fig. 4a). The osteocytes were completely surrounded by mineralized matrix (Fig. 4b). The cells were
connected by cell processes lying in canaliculi, and possessed fewer mitochondria and a less developed rough
endoplasmic reticulum than the osteoblasts.
Distally, the zone of newly formed, slender osseous trabeculae merged into a cell-rich, fibrous, and highly vascularized mesenchymal tissue (Fig. 3a and e). Within this
tissue, cellular condensations associated with reticular
bundles of collagen fibers were present (Fig. 3e). The cells
within these condensations contained numerous mitochondria and a prominent rough endoplasmic reticulum
(Fig. 5). In the distal direction, the bundles of collagen
fibers became less prominent.
The extracellular matrix of the mesenchymal tissue did
not exhibit the alcianophilia, which histochemically characterizes the presence of acid mucosubstances of the cartilage matrix (not shown). This lack of alcianophilia suggested that chondrogenesis had not yet started in this
specimen. Peripherally, the mesenchymal tissue was continuous with the cambium layer of the periosteum (Fig.
3a).
Specimen R4 (Early Antler Regeneration)
In this specimen, the antlers had already regenerated to
a length of approximately 4 cm and were covered by velvet
skin. The pedicle bone and the proximal portion of the
regenerated antler were lined by a periosteum/perichondrium that was divided into an outer fibrous and an inner
cambium/cellular layer (Fig. 6a). In the distal direction,
both layers increased in thickness, and the layering itself
became less distinct. The tip of the regenerating antler
was capped by a highly vascularized hyperplastic perichondrium (not shown). Beneath this hyperplastic perichondrium, mesenchymal cells sequentially differentiated
into chondroblasts and chondrocytes. The chondrocytes
were arranged in mostly vertically oriented columnar
structures that were separated by a highly vascularized
mesenchymal tissue (Fig. 6b).
PEDICLE RESTORATION AND ANTLER REGENERATION
745
Fig. 2. Early pedicle restoration in a roe buck. a: The former casting
wound is completely covered by newly formed skin. Note the smoothing
of the pedicle bone’s separation surface compared to Figure 1. The
square indicates the region shown in b. C, cambium layer of pedicle
periosteum; F, fibrous layer of pedicle periosteum; asterisks, pedicle
bone. Specimen R3: HE (⫻22, bar ⫽ 500 ␮m). b: Higher magnification of
the pedicle region indicated by the square in a. Beginning bone formation on the surface of the pedicle bone (asterisk). Black arrows, thin layer
of osteoid; white arrows, osteocytes that were recently incorporated into
the osteoid; arrowhead, slender bony outgrowth extending from the
pedicle bone; Ob, seam of osteoblasts; P, pedicle periosteum. Specimen R3: HE (⫻180, bar ⫽ 50 ␮m).
Further proximally, the chondrocytes underwent hypertrophic changes, and the cartilage matrix became mineralized. The calcified cartilage was then eroded by multinucleated chondro-/osteoclasts, and woven bone was laid
down on the remnants of the cartilaginous trabeculae
(Fig. 6c). These combined chondroclastic and osteoblastic
activities were responsible for the formation of a primary
spongiosa, composed of bone and calcified cartilage. Further proximally, the primary spongiosa, whose trabeculae
no longer exhibited a preferential orientation, was converted into a secondary spongiosa consisting of lamellar
bone. Along the periphery of the growing antler, a sleeve
of bone was formed by intramembranous ossification from
the periosteum.
The present investigation provides histological information on pedicle restoration and early antler regeneration
in roe and fallow deer. Since the studied specimens represent different stages of this developmental process, we
combined the results to hypothetically reconstruct the
basic histogenetic events that occur during this period of
cephalic appendage regeneration in deer.
Shortly after the antlers were cast, ongoing osteoclastic
bone resorption was observed in the distal pedicle. Active
osteoclasts were also present along the pedicle periphery.
The bone resorption leading to antler casting occurs both
deep within the pedicle and along the pedicle periphery
DISCUSSION
746
KIERDORF ET AL.
(Gruber, 1937; Waldo and Wislocki, 1951; Wislocki and
Waldo, 1953; Goss et al., 1992). Osteoclastic activity is
most intense in a rather narrow layer, which corresponds
to the future separation plane. However, some bone resorption also occurs in other areas of the pedicle surface,
as was observed in the present study and in previous
studies by Gruber (1937) and Kierdorf U et al. (1994).
In accordance with the findings of Gruber (1937), the
present investigation showed that bone erosion in the
distal pedicle continues for some time after antler casting,
leading to a smoothing of the uneven separation surface.
However, osteoclastic activity is soon reduced, and the
histological picture is then dominated by bone formation.
In this way, the pedicle bone is strengthened, and a base
for the regenerating antler is formed. While initially osteoblastic activity is limited to a thickening of the preexisting osseous trabeculae of the pedicle stump, later new,
slender, osseous trabeculae extending from the separation
plane are also formed. The formation of a narrow zone of
delicate osseous trabeculae, which leads to a partial restoration of the distal pedicle portion lost along with the
cast antler, was described by Gruber (1937) in the roe deer
and by Wislocki (1942) in the white-tailed deer
(Odocoileus virginianus). Corroborating and extending
previous observations by Gruber (1937), the present study
demonstrated by both light and electron microscopy that
this narrow bone zone is formed by intramembranous
ossification.
During the later stages of cranial appendage regeneration, the ossification process in the distal portion of the
developing outgrowth is clearly an endochondral one, in
that cartilage is formed first and is subsequently replaced
by bone. This mode of bone formation corresponds to the
situation during more advanced stages of antler regrowth
(Gruber, 1937; Banks, 1974; Banks and Newbrey, 1983a,
b; Price et al., 1996).
There appears to be a parallel between the sequence of
events occurring in cranial appendage regeneration in
deer and in secondary bone repair in fractured mammalian long bones. For example, osteogenesis in the fracture
callus is likewise reported to include initial intramembranous bone formation mediated by cells undergoing primary osteoblastic differentiation, and secondary endochondral bone formation with chondrocytic differentiation
of progenitor cells and subsequent replacement of cartilage by bone (Yoo and Johnstone, 1998).
The origin of the cells forming the bony component of
the regenerating antler has been a matter of controversy
(Goss, 1985, 1995; Kierdorf and Kierdorf, 1992, 2001; Li
and Suttie, 2001). Based on histological studies in whitetailed deer, Wislocki (1942, p. 379) stated that, “one gains
Fig. 3. Advanced stage of pedicle restoration in a fallow buck. a:
Overview of regenerated cranial appendage. Newly formed slender osseous trabeculae (T) distal to the pedicle stump (asterisk). The zone of
the slender trabeculae is capped by mesenchymal tissue (M). D, dermis;
E, epidermis. The rectangles indicate the regions shown in b, c, and e.
Specimen F: Heidenhain’s azan (⫻6.4, bar ⫽ 1.25 mm). b: Higher magnification of the transition zone between the pedicle stump (asterisk) and
the newly formed osseous trabeculae (T). The mesenchymal tissue (M)
overlying the trabecular bone is seen in the upper left corner of the figure.
Specimen F, Heidenhain’s azan (⫻13.2, bar ⫽ 600 ␮m). c: Newly
formed, mostly vertically oriented osseous trabeculae (T) lined by osteoblasts (arrow). Note the presence of numerous capillaries (asterisk) in the
intertrabecular mesenchymal tissue. Specimen F: Heidenhain’s azan
(⫻53, bar ⫽ 150 ␮m). d: Higher magnification of a newly formed osseous
trabecula with some recently incorporated cells (osteocytes, black arrow). White arrows, osteoblasts; asterisk, mineralized bone matrix.
Specimen F: semithin section, toluidine blue-borax (⫻211, bar ⫽ 38 ␮m).
e: Cellular condensations and accompanying reticular bundles of collagen fibers (arrow) in the richly vascularized mesenchymal tissue overlying the zone of the newly formed osseous trabeculae. Asterisk, vascular
space. Specimen F: Heidenhain’s azan (⫻53, bar ⫽ 150 ␮m).
PEDICLE RESTORATION AND ANTLER REGENERATION
Fig. 4. Cells from the newly formed osseous trabeculae of the fallow
deer pedicle. a: Osteoblast from the periphery of a newly formed osseous trabecula. Note the richness of collagen fibers (cut at different
angles) in the extracellular matrix, and the occurrence of numerous foci
of mineralization (arrows) in that matrix. ER, rough endoplasmic reticulum; N, nucleus; arrowhead, cell process of osteoblast; asterisks, min-
747
eralized bone matrix. Transmission electron micrograph (⫻4,540, bar ⫽
2 ␮m). b: Osteocyte from a newly formed osseous trabecula. The cell is
embedded in mineralized bone matrix. M, mitochondrion; N, nucleus;
arrowhead, cell process of osteocyte. Transmission electron micrograph
(⫻6,600, bar ⫽ 2 ␮m).
748
KIERDORF ET AL.
Fig. 5. Cells from the cellular condensations in the fibrous mesenchymal tissue of the fallow deer pedicle
distal to the newly formed osseous trabeculae. The cells contain numerous mitochondria (M) and a prominent
rough endoplasmic reticulum (ER). N, nucleus; asterisks, bundles of collagen fibers in the extracellular matrix
cut at different angles (⫻4,800, bar ⫽ 2 ␮m).
the impression that it is the proliferating deeper portion of
the corium, rather than adjacent periosteal tissue, which
restores the surface of the pedicle and gives rise to the
osteogenic germinal bed.” However, based largely on the
morphological analysis of so-called double-head antlers,
other authors have proposed that the pedicle periosteum
is the (main) cell source for the osteogenic component of
the regenerating antler (Nitsche, 1898; Kierdorf and Kierdorf, 1992, 2001; Kierdorf U et al., 1994). Gruber (1937)
suggested that in addition to periosteal cells, cells originating from the marrow spaces of the pedicle also contribute to the osteogenic tissue that covers the separation
surface of the pedicle. Results of genetic labeling of cells
from the antlerogenic periosteum (i.e., the specialized
periosteum overlying the prospective pedicle region
(Hartwig and Schrudde, 1974; Goss and Powel, 1985))
indicate that the bony component of pedicles and first
antlers is derived from this periosteum (Li and Suttie,
2001). As yet, corresponding data for the regenerating
antler are not available.
The histological findings of the present study are consistent with the view that the bony component of the
regenerating cranial appendages of deer is, at least to a
large extent, derived from the pedicle periosteum. Shortly
after casting, the periosteum of the distal pedicle portion
(especially its cambium layer) is markedly increased in
thickness, which suggests that it serves as the major
source of osteogenic cells. However, some contribution of
endosteal cells or of cells originating from the marrow
spaces of the pedicle to the osteogenic tissue can not be
excluded.
Evidence from in vivo and in vitro studies on other
skeletal structures indicates that periosteal cells can un-
dergo both osteogenic and chondrogenic differentiation,
and that both osteoblast and chondroblast precursors are
located in the cambium layer of the periosteum (Fang and
Hall, 1997; Yoo and Johnstone, 1998; Ito et al., 2001).
Moreover, there is evidence to support the notion that a
common precursor population of both chondrogenic and
osteogenic cells exists in the periosteum (Fang and Hall,
1997; Ito et al., 2001). It may thus be speculated that also
in the case of cranial appendage regeneration in deer, the
pedicle periosteum is a source of both osteoblast and chondroblast progenitors, which originate from a common stem
cell population.
The histological findings of the present study indicate
that early postcasting bone is formed by intramembranous ossification; however, the process of bone formation
at the tip of the cranial appendage soon changes to an
endochondral one. This could be taken as indicating that
osteoblasts are initially recruited from the (hypothetical)
stem cell population residing in the periosteum, and that
later a chondrogenic pathway is followed. Further studies
are necessary to address this question of a potential sequential recruitment of osteoblast and chondroblast precursors from the periosteum in the case of cranial appendage regeneration in deer.
Chondrogenesis in membrane bones occurs wherever
and whenever rapid skeletal growth is required, and is
considered to be an adaptive response to local microenvironmental stimulation. Fang and Hall (1997) noted that
cartilage is the only skeletal tissue that has active cell
division, and chondrogenic differentiation therefore
achieves a larger volume of skeletal tissue within a
shorter period compared to osteogenesis. These authors
convincingly argued that the chondrogenic potential of
PEDICLE RESTORATION AND ANTLER REGENERATION
Fig. 6. Early regenerating antler of a roe buck. a: Middle portion of
regenerated antler. The cartilage (asterisks) is lined by a perichondrium
consisting of an inner cellular (C) and an outer fibrous layer (F). D, dermis;
E, epidermis; H, hair follicle; S, sebaceous gland; arrows, vascular
spaces. Specimen R4: Heidenhain’s azan (⫻26, bar ⫽ 500 ␮m). b:
Vertical columns of cartilage (C) separated by highly vascularized mes-
749
enchymal tissue. Arrowheads, vascular spaces. Specimen R4: Heidenhain’s azan (⫻80, bar ⫽ 100 ␮m). c: Zone of cartilage resorption and
replacement by bone. Asterisk, cartilage; arrows, newly formed bone;
arrowheads, multinucleated chondro-/osteoclasts; I, intertrabecular tissue. Specimen R4: Heidenhain’s azan (⫻160, bar ⫽ 50 ␮m).
750
KIERDORF ET AL.
membrane bone is retained for circumstances in which
such a rapid increase of bone volume is demanded—for
example, in the case of fracture repair. The pedicles of
deer are outgrowths from the frontals and as such represent membrane bones. Moreover, the rapidity of antler
growth, which leads to the formation of a huge volume of
bone within a seasonally fixed period of only a few months,
is without parallel in other skeletal structures in vertebrates. Thus it comes as no surprise that cartilage is
formed very early in the process of cranial appendage
regeneration, and that the pedicle periosteum is apparently capable of producing not only osteoblast precursors
but also chondroblast precursors.
There are certain parallels between antler regrowth and
the formation of the primary cranial appendages of deer
(i.e., the pedicles and first antlers) (Kierdorf and Kierdorf,
2002). Studies in fallow deer and red deer (Cervus elaphus) have demonstrated that in these species only the
very early stages of pedicle growth occur by intramembranous ossification, whereas most of the elongation is
brought about by proliferation of cartilage, which is subsequently replaced by bone in a process of endochondral
ossification (Kierdorf H et al., 1994; Li and Suttie, 1994;
Szuwart et al., 1994). Compared to fallow and red deer, in
the roe deer the onset of chondrogenesis occurs much
later, when the cranial outgrowths have already reached a
considerable height (Gruber, 1937). Since roe deer are
smaller than both fallow deer and red deer, and their
pedicles contain a much smaller volume of bone compared
to that in the other two species, this interspecies difference with regard to the start of cartilage formation during
cranial appendage development correlates with the view
that chondrogenesis by membrane bones is a specific
growth response when rapid formation of large volumes of
bone is required.
Based on studies in red deer, Li and Suttie (2000) proposed that the stimulus for the onset of cartilage formation during pedicle growth may be a mechanical pressure
on the underlying tissues caused by the stretched pedicle
skin (which results from the subdermal expansion of the
bony component of the pedicle). It seems unlikely that this
“pressure hypothesis” can be extended to also cover the
onset of chondrogenesis in the case of cranial appendage
regeneration in deer. In pedicle formation, a full-thickness
scalp skin is initially stretched by a subcutaneously expanding tissue mass, and only during later stages of development is this stretch released by neogenesis of skin (Li
and Suttie, 2000). In contrast, during cranial appendage
regeneration, growth of the bony component and rapid
new (velvet) skin formation occur simultaneously and in a
coordinated manner. It is therefore unlikely that the
newly formed velvet skin exerts any significant pressure
on the underlying tissues.
In conclusion, the present investigation revealed that
after antlers are cast, osteoclastic and osteoblastic activities lead to a smoothing of the separation surface, a
strengthening of the pedicle bone, and a partial restoration of the distal pedicle, thereby forming the base for
subsequent antler regeneration. Bone formation during
early cranial appendage regeneration initially occurs by
intramembranous ossification, while antler elongation is
later brought about by the proliferation of cartilage, which
is subsequently replaced by bone. The histological findings
of our study are consistent with the view that the bony
component of the regenerating antler is largely derived
from the cells of the pedicle periosteum. It is further
suggested that the cells originating from the pedicle periosteum can undergo both osteogenic and chondrogenic
differentiation, and that the early onset of chondrogenesis
is a reaction to the necessity of producing a huge volume of
bone within a short period.
LITERATURE CITED
Banks WJ. 1974. The ossification process of the developing antler in
the white-tailed deer (Odocoileus virginianus). Calcif Tissue Res
14:257–274.
Banks WJ, Newbrey JW. 1983a. Light microscopic studies of the
ossification process in developing antlers. In: Brown RD, editor.
Antler development in Cervidae. Kingsville: Caesar Kleberg Wildlife Research Institute. p 231–260.
Banks WJ, Newbrey JW. 1983b. Antler development as a unique
modification of mammalian endochondral ossification. In: Brown
RD, editor. Antler development in Cervidae. Kingsville: Caesar
Kleberg Wildlife Research Institute. p 279 –306.
Bubenik GA, Schams D, Coenen G. 1987. The effect of artificial
photoperiodicity and antiandrogen treatment on the antler growth
and plasma levels of LH, FSH, testosterone, prolactin and alkaline
phosphatase in the male white-tailed deer. Comp Biochem Physiol
87A:551–559.
Bubenik GA. 2001. Deer antlers—a wonder of nature: structure and
function of antlers, regulation of their development, and their potential in medicine. In: Sim JS, Sunwoo HH, Hudson RJ, Jeon BT,
editors. Antler science and product technology. Edmonton: Antler
Science and Product Technology Research Centre. p 3–13.
Fang J, Hall BK. 1997. Chondrogenic cell differentiation from membrane bone periostea. Anat Embryol 196:349 –362.
Goss RJ. 1968. Inhibition of growth and shedding of antlers by sex
hormones. Nature 220:83– 85.
Goss RJ. 1984. Epimorphic regeneration in mammals. In: Hunt TK,
Heppenstall RB, Pines E, Rovee D, editors. Soft and hard tissue
repair. New York: Praeger. p 554 –573.
Goss RJ. 1985. Tissue differentiation in regenerating antlers. R Soc N
Z Bull 22:229 –238.
Goss RJ, Powel RS. 1985. Induction of deer antlers by transplanted
periosteum I. Graft size and shape. J Exp Zool 235:359 –373.
Goss RJ. 1992. Regeneration versus repair. In: Cohen IK, Diegelmann
RF, Lindblad WJ, editors. Wound healing— biochemical and clinical
aspects. Philadelphia: Saunders. p 20 –39.
Goss RJ, Van Praagh A, Brewer P. 1992. The mechanism of antler
casting in the fallow deer. J Exp Zool 264:429 – 436.
Goss RJ. 1995. Future directions in antler research. Anat Rec 241:
291–302.
Gruber GB. 1937. Morphobiologische Untersuchungen am CervidenGeweih. Werden, Wechsel und Wesen des Rehgehörns. Nachr Ges
Wiss Göttingen, Math-Physik Kl NF Fachgr VI 3:9 – 63.
Hartwig H, Schrudde J. 1974. Experimentelle Untersuchungen zur
Bildung der primären Stirnauswüchse beim Reh (Capreolus capreolus L.). Z Jagdwiss 20:1–13.
Hatae T, Fujita M, Sagara H. 1986. Helical structure in the apical
tubules of several epithelia. Cell Tissue Res 244:39 – 46.
Ito Y, Fitzsimmons JS, Sanyal A, Mello MA, Mukherjee N, O’Driscoll
SW. 2001. Localization of chondrocyte precursors in periosteum.
Osteoarthritis Cartilage 9:215–223.
Kierdorf H, Kierdorf U. 1992. State of determination of the antlerogenic tissues with special reference to double-head formation. In:
Brown RD, editor. The biology of deer. New York: Springer-Verlag.
p 525–531.
Kierdorf H, Kierdorf U, Szuwart T, Gath U, Clemen G. 1994. Light
microscopic observations on the ossification process in the early
developing pedicle of fallow deer (Dama dama). Ann Anat 176:243–
249.
Kierdorf H, Kierdorf U. 2001. The role of the antlerogenic periosteum
for pedicle and antler formation in deer. In: Sim JS, Sunwoo HH,
Hudson RJ, Jeon BT, editors. Antler science and product technology. Edmonton: Antler Science and Product Technology Research
Centre. p 33–51.
PEDICLE RESTORATION AND ANTLER REGENERATION
Kierdorf U, Schultz M, Fischer K. 1993. Effects of an antiandrogen
treatment on the antler cycle of male fallow deer (Dama dama L.).
J Exp Zool 266:195–205.
Kierdorf U, Kierdorf H, Schultz M. 1994. The macroscopic and microscopic structure of double-head antlers and pedicle bone of Cervidae
(Mammalia: Artiodactyla). Ann Anat 176:251–257.
Kierdorf U, Kierdorf H, Knuth S. 1995. Effects of castration on antler
growth in fallow deer (Dama dama L.). J Exp Zool 273:33– 43.
Kierdorf U, Kierdorf H. 2002. Pedicle and first antler formation in
deer: anatomical, histological, and developmental aspects. Z Jagdwiss 48:22–34.
Li C, Suttie JM. 1994. Light microscopic studies of pedicle and early
first antler development in red deer (Cervus elaphus). Anat Rec
239:198 –215.
Li C, Suttie JM. 2000. Histological studies of pedicle skin formation
and its transformation to antler velvet in red deer (Cervus elaphus).
Anat Rec 260:62–71.
Li C, Suttie JM. 2001. Deer antlerogenic periosteum: a piece of postnatally retained embryonic tissue? Anat Embryol 204:375–388.
Lincoln GA. 1971. The seasonal reproductive changes in the red deer
stag (Cervus elaphus). J Zool 163:105–123.
Muir PD, Barrell GK, Sykes AR. 1982. Modification of antler growth
in red deer stags by use of a synthetic progestagen. Proc N Z Soc
Anim Prod 42:145–147.
Nitsche H. 1898. Studien über Hirsche (Gattung Cervus weitesten
Sinne). Heft I. Untersuchungen über mehrstangige Geweihe und
751
die Morphologie der Hufthierhörner im allgemeinen. Leipzig: W.
Engelmann. p 61.
Price JS, Oyajobi BO, Nalin AM, Frazer A, Russell GGR, Sandell LJ.
1996. Chondrogenesis in the regenerating antler tip in red deer:
expression of collagen types I, IIA, IIB, and X demonstrated by in
situ nucleic acid hybridization and immunocytochemistry. Dev Dyn
205:332–347.
Suttie JM, Fennessy PF, Lapwood KR, Corson ID. 1995. Role of
steroids in antler growth of red deer stags. J Exp Zool 271:120 –130.
Szuwart T, Gath U, Althoff J, Höhling HJ. 1994. Biochemical and
histological study of the ossification in the early developing pedicle
of the fallow deer (Dama dama). Cell Tissue Res 277:123–129.
Waldo CM, Wislocki GB. 1951. Observations on the shedding of the
antlers of Virginia deer (Odocoileus virginianus borealis). Am J
Anat 88:351–395.
Wislocki GB. 1942. Studies on the growth of deer antlers. I. On the
structure and histogenesis of the antlers of the Virginia deer
(Odocoileus virginianus borealis). Am J Anat 71:371– 415.
Wislocki GB, Aub JC, Waldo CM. 1947. The effects of gonadectomy
and the administration of testosterone proprionate on the growth of
antlers in male and female deer. Endocrinology 40:202–224.
Wislocki GB, Waldo CM. 1953. Further observations on the histological changes associated with the shedding of the antlers of the
white-tailed deer (Odocoileus viginianus borealis). Anat Rec 117:
353–376.
Yoo JU, Johnstone B. 1998. The role of osteochondral progenitor cells
in fracture repair. Clin Orthop Relat Res 355(Suppl):S73–S81.
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formation, deer, fallos, antler, restoration, regenerative, pedicle, studies, early, bones, roe, histological
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