Detection of growth factors and proto-oncogene mRNA in the growing tip of red deer (Cervus elaphus) antler using reverse-transcriptase polymerase chain reaction (RT-PCR)

IGF1R and LOX Modules Are Related to Antler Growth Rate Revealed by Integrated Analyses of Genomics and Transcriptomics

Deer antlers are organs of bone and have an extremely rapid growth rate. Thus far, the molecular mechanism underlying rapid antler growth has not been properly elucidated, and key genes driving this growth rate have not been fully identified. In this study, based on the newly assembled high-quality sika deer genome, we conducted an integrated analysis of genome-wide association analysis (GWAS) and weighted gene co-expression network analysis (WGCNA) using genome resequencing data from our previous GWAS, with weight and transcriptome sequencing data of faster- vs. slower-growing antlers of sika deer. The expressions of key genes were verified using Fragments Per Kilobase of transcript per Million fragments mapped (FPKM) in different tissue zones of the antler growth center, different types of sika deer tissues and antler tissues collected from faster and slower growth rates. The results show that a total of 49 genes related to antler growth rate were identified, and most of those genes were enriched in the IGF1R and LOX modules. The gene regulation network of antler growth rate through the IGF1R pathway was constructed. In conclusion, the integration of GWAS and WGCNA analyses had great advantages in identifying regulatory genes of complex antler growth traits over using singular methods individually, and we believe that our findings in the present study can provide further insight into unveiling the mechanism underlying extraordinary fast antler growth rate in particular, as well as the regulatory mechanism of rapid tissue proliferation in general.

Comparative transcriptome analysis of the main beam and brow tine of sika deer antler provides insights into the molecular control of rapid antler growth

Background

Deer antlers have become a valuable model for biomedical research due to the capacities of regeneration and rapid growth. However, the molecular mechanism of rapid antler growth remains to be elucidated. The aim of the present study was to compare and explore the molecular control exerted by the main beam and brow tine during rapid antler growth.

Methods

The main beams and brow tines of sika deer antlers were collected from Chinese sika deer (Cervus nippon) at the rapid growth stage. Comparative transcriptome analysis was conducted using RNA-Seq technology. Differential expression was assessed using the DEGseq package. Functional Gene Ontology (GO) enrichment analysis was accomplished using a rigorous algorithm according to the GO Term Finder tool, and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway enrichment analysis was accomplished with the R function phyper, followed by the hypergeometric test and Bonferroni correction. Quantitative real-time polymerase chain reaction (qRT-PCR) was carried out to verify the RNA levels for differentially expressed mRNAs.

Results

The expression levels of 16 differentially expressed genes (DEGs) involved in chondrogenesis and cartilage development were identified as significantly upregulated in the main beams, including transcription factor SOX-9 (Sox9), collagen alpha-1(II) chain (Col2a1), aggrecan core protein (Acan), etc. However, the expression levels of 17 DEGs involved in endochondral ossification and bone formation were identified as significantly upregulated in the brow tines, including collagen alpha-1(X) chain (Col10a1), osteopontin (Spp1) and bone sialoprotein 2 (Ibsp), etc.

Conclusion

These results suggest that the antler main beam has stronger growth capacity involved in chondrogenesis and cartilage development compared to the brow tine during rapid antler growth, which is mainly achieved through regulation of Sox9 and its target genes, whereas the antler brow tine has stronger capacities of endochondral bone formation and resorption compared to the main beam during rapid antler growth, which is mainly achieved through the genes involved in regulating osteoblast and osteoclast activities. Thus, the current research has deeply expanded our understanding of the intrinsic molecular regulation displayed by the main beam and brow tine during rapid antler growth.

ACE inhibitory peptides in standard and fermented deer velvet: an in silico and in vitro investigation

BACKGROUND

The use of deer velvet antler (DVA) as a potent traditional medicine ingredient goes back for over 2000 years in Asia. Increasingly, though, DVA is being included as a high protein functional food ingredient in convenient, ready to consume products in Korea and China. As such, it is a potential source of endogenous bioactive peptides and of 'cryptides', i.e. bioactive peptides enzymatically released by endogenous proteases, by processing and/or by gastrointestinal digestion. Fermentation is an example of a processing step known to release bioactive peptides from food proteins. In this study, we aimed to identify in silico bioactive peptides and cryptides in DVA, before and after fermentation, and subsequently to validate the major predicted bioactivity by in vitro analysis.

METHODS

Peptides that were either free or located within proteins were identified in the DVA samples by liquid chromatography-tandem mass spectrometry (LC-MS/MS) followed by database searching. Bioactive peptides and cryptides were identified in silico by sequence matching against a database of known bioactive peptides. Angiotensin-converting enzyme (ACE) inhibitory activity was measured by a colorimetric method.

RESULTS

Three free bioactive peptides (LVVYPW, LVVYPWTQ and VVYPWTQ) were solely found in fermented DVA, the latter two of which are known ACE inhibitors. However matches to multiple ACE inhibitor cryptides were obtained within protein and peptide sequences of both unfermented and fermented DVA. In vitro analysis showed that the ACE inhibitory activity of DVA was more pronounced in the fermented sample, but both unfermented and fermented DVA had similar activity following release of cryptides by simulated gastrointestinal digestion.

CONCLUSIONS

DVA contains multiple ACE inhibitory peptide sequences that may be released by fermentation or following oral consumption, and which may provide a health benefit through positive effects on the cardiovascular system. The study illustrates the power of in silico combined with in vitro methods for analysis of the effects of processing on bioactive peptides in complex functional ingredients like DVA.

The effects of CRISPR-Cas9 knockout of the TGF-β1 gene on antler cartilage cells in vitro

BACKGROUND

Deer antler is the only mammalian organ that can be completely regenerated every year. Its periodic regeneration is regulated by multiple factors, including transforming growth factor β (TGF-β). This widely distributed multi-functional growth factor can control the proliferation and differentiation of many types of cell, and it may play a crucial regulatory role in antler regeneration. This study explored the role of TGF-β1 during the rapid growth of sika deer antler.

METHODS

Three CRISPR-Cas9 knockout vectors targeting the TGF-β1 gene of sika deer were constructed and packaged with a lentiviral system. The expression level of TGF-β1 protein in the knockout cell line was determined using western blot, the proliferation and migration of cartilage cells in vitro were respectively determined using EdU and the cell scratch test, and the expression levels of TGF-β pathway-related genes were determined using a PCR array.

RESULTS

Of the three gRNAs designed, pBOBI-gRNA2 had the best knockout effect. Knockout of TGF-β1 gene inhibits the proliferation of cartilage cells and enhances their migration in vitro. TGF-β signaling pathway-related genes undergo significant changes, so we speculate that when the TGF-β pathway is blocked, the BMP signaling pathway mediated by BMP4 may play a key role.

CONCLUSIONS

TGF-β1 is a newly identified regulatory factor of rapid growth in sika deer antler.

Transcriptomic characterization elucidates a signaling network that controls antler growth

Deer antlers are amazing appendages with the fastest growth rate among mammalian organs. Antler growth is driven by the growth center through a modified endochondral ossification process. Thus, identification of signaling pathways functioning in antler growth center would help us to uncover the underlying molecular mechanism of rapid antler growth. Furthermore, exploring and dissecting the molecular mechanism that regulates antler growth is extremely important and helpful for identifying methods to enhance long bone growth and treat cartilage- and bone-related diseases. In this study, we build a comprehensive intercellular signaling network in antler growth centers from both the slow growth stage and rapid growth stage using a state-of-art RNA-Seq approach. This network includes differentially expressed genes that regulate the activation of multiple signaling pathways, including the regulation of actin cytoskeleton, calcium signaling, and adherens junction. These signaling pathways coordinately control multiple biological processes, including chondrocyte proliferation and differentiation, matrix homeostasis, mechanobiology, and aging processes, during antler growth in a comprehensive and efficient manner. Therefore, our study provides novel insights into the molecular mechanisms regulating antler growth and provides valuable and powerful insight for medical research on therapeutic strategies targeting skeletal disorders and related cartilage and bone diseases.

microRNA-18b modulates insulin-like growth factor-1 expression in deer antler cell proliferation by directly targeting its 3' untranslated region

Insulin-like growth factor-1 (IGF-1) is a multipromoter gene that has complex biological functions and plays an important role in Chinese sika deer antler cell differentiation and proliferation. microRNAs and their roles in deer antler growth have attracted much attention. In the present study, to investigate the effect of microRNAs on the regulation of IGF-1 during the rapid growth of antlers, miRNA GeneChip analysis and TargetScan Human software were used to screen microRNAs that bind to the 3' untranslated region (3'UTR) of IGF-1. The results indicated that a significantly differential expression of miR-18b was observed in cartilage and mesenchymal of antler tip tissue and the presence of miR-18b-binding sites within the IGF-1 3'UTR. A miR-18b mimic was then transfected into antler cartilage cells to overexpress miR-18b and the expression levels were quantified by real-time PCR. Real-time PCR showed that the expression level of miR-18b in transfected cells was significantly increased compared with the control group (p<0.01). Dual luciferase assays revealed that miR-18b decreased the fluorescence value of the luciferase reporter gene in the group transfected with the wild-type vector of IGF-1 3'UTR. In contrast, the relative luciferase activity in the group transfected with the mutant vector of IGF-1 3'UTR did not change obviously. MTT assays and cell cycle analyses confirmed that overexpression of the miR-18b mimic inhibited the proliferation of cartilage cells. In contrast, transfection of a miR-18b inhibitor increased the cell proliferation rate. Furthermore, Western blot analyses revealed that overexpression of miR-18b mimics downregulated the protein levels of IGF-1, while IGF-1 expression increased after transfection of miR-18b inhibitors. Taken together, our findings show that miR-18b is a potentially novel target in deer antler cell proliferation. miR-18b may modulate IGF-1 expression of sika deer antler.

Association between melatonin receptor 1A (MTNR1A) gene single-nucleotide polymorphisms and the velvet antler yield of Sika deer

Melatonin, a secretion from pineal gland is ambiguously considered as the key hormone involved in regulation of the antler cycle in Sika deer. To find out more about the roles of melatonin and its receptor gene, we carried out current study to investigate the association between polymorphisms in melatonin receptor 1A (MTNR1A) gene and the antler yield from Sika deer. A total of 251 Sika deer were analyzed in this study, of which consisted of Wusan Sika deer (n = 163) and Dongfeng Sika deer (n = 88). MTNRA gene was amplified by PCR and genotyped by Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Three polymorphism loci (C518T, C629G and C635T) were detected in exon2 of MTNR1A gene. The restriction site Ecol881 was used for C518T while a C629G polymorphism locus was digested with Mval restriction endonucleases. In Wusan Sika deer the allele frequencies of C and T were 0.637 and 0.363 for C518T, Also C and G alleles in C629G locus were 0.206 and 0.794. Genotypic frequencies of allele CC, CT and TT were 33.7, 59.9 and 6.4 % respectively, It showed 1.8, 37.4 and 60.7 % for frequencies of genotypes CC, CG and GG. In Dongfeng Sika deer the allele frequencies of C and T were 0.518 and 0.482 for C518T, C and G alleles were 0.375 and 0.625 for C629G. Genotypic frequencies were 10.6, 82.4 and 7.1 % for genotypes CC, CT and TT respectively, and they were 1.1, 72.7 and 26.2 % for genotypes CC, CG and GG. Among three SNPs, only C629G showed significant association (P < 0.05) with average antler yield in Wusan Sika deer, while no SNP was significant in Dongfeng Sika deer. These preliminary results implied that the identified SNPs of MTNR1A gene might influence the antler yield in Wusan Sika deer.

Deer Antler Extract Improves Fatigue Effect through Altering the Expression of Genes Related to Muscle Strength in Skeletal Muscle of Mice

Deer antler is a well-known traditional Chinese medicine used in Asian countries for the tonic and the improvement of aging symptoms. The present study was designed to investigate the antifatigue effect and mechanism of Formosan sambar deer tip antler extract (FSDTAE). The swimming times to exhaustion of mice administered FSDTAE (8.2 mg/day) for 28 days were apparently longer than those of the vehicle-treated mice in forced swim test. However, the indicators of fatigue, such as the reduction in glucose level and the increases in blood urea nitrogen and lactic acid levels, were not significantly inhibited by FSDTAE. Therefore, microarray analysis was further used to examine the anti-fatigue mechanism of FSDTAE. We selected genes with fold changes >2 or <-2 in skeletal muscle for pathway analysis. FSDTAE-affected genes were involved in 9 different signaling pathways, such as GnRH signaling pathway and insulin signaling pathway. All of the significantly expressed genes were classified into 8 different categories by their functions. The most enriched category was muscular system, and 6 upregulated genes, such as troponin I, troponin T1, cysteine and glycine-rich protein 2, myosin heavy polypeptide 7, tropomyosin 2, and myomesin family member 3, were responsible for the development and contraction of muscle. Real-time PCR analysis indicated that FSDTAE increased troponins mRNA expression in skeletal muscle. In conclusion, our findings suggested that FSDTAE might increase the muscle strength through the upregulation of genes responsible for muscle contraction and consequently exhibited the anti-fatigue effect in mice.

Detection of human insulin-like growth factor-1 in deer antler velvet supplements

RATIONALE

Reported incidents of the use of nutritional supplements containing deer antler velvet by athletes has increased significantly in recent years. The supplements have been reported to contain insulin-like growth factor-1 (IGF-1), which is a banned substance included on the World Anti-Doping Agency (WADA) prohibited list. The presence of deer and human IGF-1 was tested in six commercially available supplements.

METHODS

IGF-1 was extracted from the six deer antler velvet supplements using chloroform and acetonitrile precipitation methods. Ultra-performance liquid chromatography/tandem mass spectrometry (UPLC/MS/MS) methods were developed to measure intact IGF-1 protein and IGF-1 trypsin peptides using a triple quadrupole mass spectrometer. Five deer-specific and five human-specific multiple-reaction monitoring (MRM) transitions for intact IGF-1were measured as well as six deer-specific and seven human-specific MRM transitions for an IGF-1 trypsin peptide.

RESULTS

The peak area from each MRM transition was used to calculate the product ion ratios relative to the most abundant transition. Product ion ratios measured in the supplements were matched to ratios measured in purified protein standards. A match to human IGF-1 was identified for all the MRM transitions measured in four of the supplements tested.

CONCLUSIONS

The presence of a pharmaceutical protein, human IGF-1, was confirmed in four commercially available products sold as all natural, nutritional supplements. These methods can be used to screen additional products to further prevent the illegal sale of adulterated supplements.

Red Deer Antler Extract Accelerates Hair Growth by Stimulating Expression of Insulin-like Growth Factor I in Full-thickness Wound Healing Rat Model

In order to investigate and evaluate the effects of red deer antlers on hair growth in the full-thickness wound healing model, Sprague-Dawley rats were given incision wounds through the full thickness of their dorsal skin and deer antler was applied for 40 days. At specified intervals thereafter (4, 8, 16, 32 and 40 days), the animals were sacrificed and the wound site skins were excised, processed, and sectioned. At post-injury days 16, 32 and 40, longer and more active new hair appeared around the healing wound of antler-treated skin. Histological studies showed that the antler extract markedly increases the depth, size, and number of hair follicles. Expression of IGF-I (insulin-like growth factor) mRNA was detected by RT-PCR and real time RT-PCR. The result showed that the expression of IGF-I (days 16, 32, and 40) was obviously up-regulated in antler-treated skins compared to control skins. Similar results were seen in the ELISA analysis to quantify the IGF-I expression. These results support the notion that wound healing can cause hair growth by enhancing the expression of IGF-I. Deer antler extract appears to have the potential to promote hair growth and could be used in hair growth products.

Dietary supplementation of female rats with elk velvet antler improves physical and neurological development of offspring

Elk velvet antler (EVA) has a traditional use for promotion of general health. However, evidence of EVA effects at different lifestages is generally lacking. This paper investigated the effects of long-term maternal dietary EVA supplementation on physical, reflexological and neurological development of rat offspring. Female Wistar rats were fed standard chow or chow containing 10% EVA for 90 days prior to mating and throughout pregnancy and lactation. In each dietary group, 56 male and 56 female pups were assessed for physical, neuromotor, and reflexologic development postnatally. Among the examined physical developmental parameters, incisor eruption occurred one day earlier in pups nursing dams receiving EVA. Among neuromotor developmental parameters, duration of supported and unsupported standing was longer for pups nursing EVA supplemented dams. Acquisition of neurological reflex parameters (righting reflex, negative geotaxis, cliff avoidance acoustic startle) occurred earlier in pups nursing dams receiving EVA. Longterm maternal EVA supplementation prior to and during pregnancy and lactation accelerated certain physical, reflexologic, and neuromotor developmental milestones and caused no discernible adverse effects on developing offspring. The potential benefits of maternal EVA supplementation on postnatal development warrants further investigation to determine whether EVA can be endorsed for the promotion of maternal and child health.

Immunoregulatory cytokines are associated with protection from immunopathology following Mycobacterium avium subspecies paratuberculosis infection in red deer

Although the causative agent of Johne's disease, Mycobacterium avium subsp. paratuberculosis, is well known, the etiology of disease and the immune responses generated in response to infection are still poorly understood. Knowledge of definitive markers of protective immunity, infection, and the establishment of chronic granulomatous Johne's disease is necessary to advance vaccine and diagnostic development. We sought to profile the immune responses occurring within jejunal lymph nodes of experimentally challenged red deer (Cervus elaphus). Quantitative PCR was utilized to measure a range of cytokines, signaling molecules, and transcription factors involved in Th1, Th2, Treg, and Th17 immune responses. Significant differences in gene expression were observed between control, minimally diseased, and severely diseased animals, with severely diseased animals showing elevated proinflammatory transcripts and reduced anti-inflammatory transcripts. We identified a proinflammatory cytokine milieu of gamma interferon, interleukin-1α (IL-1α), and IL-17, which may contribute to the immunopathology observed during clinical Johne's disease and suggest that Th2 and Treg immune responses may play an important role in controlling the development of immunopathology in infected animals.

Gene expression of axon growth promoting factors in the deer antler

The annual regeneration cycle of deer (Cervidae, Artiodactyla) antlers represents a unique model of epimorphic regeneration and rapid growth in adult mammals. Regenerating antlers are innervated by trigeminal sensory axons growing through the velvet, the modified form of skin that envelopes the antler, at elongation velocities that reach one centimetre per day in the common deer (Cervus elaphus). Several axon growth promoters like NT-3, NGF or IGF-1 have been described in the antler. To increase the knowledge on the axon growth environment, we have combined different gene-expression techniques to identify and characterize the expression of promoting molecules not previously described in the antler velvet. Cross-species microarray analyses of deer samples on human arrays allowed us to build up a list of 90 extracellular or membrane molecules involved in axon growth that were potentially being expressed in the antler. Fifteen of these genes were analysed using PCR and sequencing techniques to confirm their expression in the velvet and to compare it with the expression in other antler and skin samples. Expression of 8 axon growth promoters was confirmed in the velvet, 5 of them not previously described in the antler. In conclusion, our work shows that antler velvet provides growing axons with a variety of promoters of axon growth, sharing many of them with deer's normal and pedicle skin.

Localization and characterization of STRO-1 cells in the deer pedicle and regenerating antler

The annual regeneration of deer antlers is a unique developmental event in mammals, which as a rule possess only a very limited capacity to regenerate lost appendages. Studying antler regeneration can therefore provide a deeper insight into the mechanisms that prevent limb regeneration in humans and other mammals, and, with regard to medical treatments, may possibly even show ways how to overcome these limitations. Traditionally, antler regeneration has been characterized as a process involving the formation of a blastema from de-differentiated cells. More recently it has, however, been hypothesized that antler regeneration is a stem cell-based process. Thus far, direct evidence for the presence of stem cells in primary or regenerating antlers was lacking. Here we demonstrate the presence of cells positive for the mesenchymal stem cell marker STRO-1 in the chondrogenic growth zone and the perivascular tissue of the cartilaginous zone in primary and regenerating antlers as well as in the pedicle of fallow deer (Dama dama). In addition, cells positive for the stem cell/progenitor cell markers STRO-1, CD133 and CD271 (LNGFR) were isolated from the growth zones of regenerating fallow deer antlers as well as the pedicle periosteum and cultivated for extended periods of time. We found evidence that STRO-1(+) cells isolated from the different locations are able to differentiate in vitro along the osteogenic and adipogenic lineages. Our results support the view that the annual process of antler regeneration might depend on the periodic activation of mesenchymal progenitor cells located in the pedicle periosteum. The findings of the present study indicate that not only limited tissue regeneration, but also extensive appendage regeneration in a postnatal mammal can occur as a stem cell-based process.

Expression and localization of insulin-like growth factor-I in four parts of the red deer antler

The expression and localization of insulin-like growth factor-I (IGF-I) in the four parts (tip, upper, mid and base) of the red deer antler has been extensively investigated. We used reverse transcriptase polymerase chain reaction (RT-PCR) and real-time reverse transcriptase polymerase chain reaction (real time RT-PCR), in situ hybridization, immunohistochemistry and Western blot techniques to localize IGF-I messenger ribonucleic acid (mRNA) and IGF-I peptide in the four parts of the antler. The specific sequence encoding IGF-I was detected by RT-PCR in all of the four specimens, and the 395 bp IGF-I sequence from the red deer antler was shown to have very high homology with human, goat and mouse IGF-I. In situ hybridization and immunohistochemistry results demonstrated that the expression of IGF-I occurred in chondrocytes and osteoblasts in the tip and upper parts of the antler. However, IGF-I was only detectable in osteoblasts around the bone in the mid and base parts. There were significant differences in the intensity of the signal obtained with the IGF-I probe in the tip, upper, mid and base tissues. The Western blot analysis also provided evidence that IGF-I expression was localized differentially in the four parts of the deer antler. This study indicates that antler tissue is an essential part of the IGF system, which is involved in the regulation of the growth of red deer antlers. The specific expression of IGF-I in the four parts of the deer antler suggests that the IGF-I molecule is present at significantly different levels throughout the deer antler development and regeneration processes. Localization of IGF-I in chondrocytes and osteoblasts suggests that IGF-I may play an important role in cartilage and bone formation. In addition, it may have a variety of biophysical effects that influence the rapid growth of deer antlers.

Gene expression dynamics in deer antler: mesenchymal differentiation toward chondrogenesis

Annual re-growth of deer antler represents a unique example of complete organ regeneration. Because antler mesenchymal cells retain their embryonic capacity to develop into cartilage or bone, studying antler development provides a natural system to follow gene expression changes during mesenchymal differentiation toward chondrogenic/osteogenic lineage. To identify novel genes involved either in early events of mesenchymal cell specialization or in robust bone development, we have introduced a 3 K heterologous microarray set-up (deer cDNA versus mouse template). Fifteen genes were differentially expressed; genes for housekeeping, regulatory functions (components of different signaling pathways, including FGF, TGFbeta, Wnt), and genes encoding members of the Polycomb group were represented. Expression dynamics for genes are visualized by an expression logo. The expression profile of the gene C21orf70 of unknown function is described along with the effects when over-expressed; furthermore the nuclear localization of the cognate protein is shown. In this report, we demonstrate the particular advantage of the velvet antler model in bone research for: (1) identification of mesenchymal and precartilaginous genes and (2) targeting genes upregulated in robust cartilage development.

A catalog for transcripts in the venom gland of the Agkistrodon acutus: identification of the toxins potentially involved in coagulopathy

Agkistrodon acutus is a special agkistrodon halys, only distributed in Southern China, with a few exceptions in Vietnam. It is a cherished element used in traditional Chinese medicine. In order to produce a global panorama of gene expression in the Agkistrodon acutus venom gland, a non-normalized cDNA library was constructed, and 8696 high quality 5' end expressed sequenced tags (ESTs) were sequenced and analyzed. The initial sequences were assembled into 2855 clusters. Of these clusters, only 45.60% clusters matched known sequence and 54.40% had no match to any known sequence in GenBank. Except for putative cellular proteins (1184 clusters), the remaining 118 clusters (40.16% of all ESTs) corresponded to sequences associated with diverse toxin function. According to expression abundance, the major toxin components were metalloproteinases (32.08%) and C-type lectin (5.22%), and other components including bradykinin-potentiating peptide (0.90%), serine proteases (0.51%), nucleotidase and nuclease (0.41%), phospholipase A2 (0.30%), disintegrin (0.05%), cytokine-like molecules (0.06%), and other proteins (0.63%). The majority of these components are thought to be responsible for coagulopathy after A. acutus bites. We have therefore generated a comprehensive catalog of the A. acutus venom gland described so far. Gene expression from the very specialized secretory tissue, especially for those involved in coagulopathy, can be surveyed and provide important information in finding novel toxins.

Deer antlers as a model of Mammalian regeneration

Deer antlers are cranial appendages that develop after birth as extensions of a permanent protuberance (pedicle) on the frontal bone. Pedicles and antlers originate from a specialized region of the frontal bone; the 'antlerogeneic periosteum' and the systemic cue which triggers their development in the fawn is an increase in circulating androgen. These primary antlers are then shed and regenerated the following year in a larger, more complex form. Antler growth is extremely rapid-an adult red deer can produce a pair of antlers weighing approximately 30kg in three months, and involves both endochondral and intramembranous ossification. Since antlers are sexual secondary characteristics, their annual cycles of growth have evolved to be closely coordinated to the reproductive cycle which, in temperate species, is linked to the photoperiod. Cessation of antler growth and death of the overlying skin (velvet) coincides with a rise in circulating testosterone as the autumn breeding season approaches. The 'dead' antlers remain attached to the pedicle until they are shed (cast) the following spring when circulating testosterone levels fall. In red deer, the species that we study, casting of the old set of antlers is followed immediately by growth of the new set. Although the anatomy of antler growth and the endocrine changes associated with it have been well documented, the molecular mechanisms involved remain poorly understood. The case for continuing to decipher them remains compelling, despite the obvious limitations of using deer as an experimental model, because this research will help provide insight into why humans and other mammals have lost the ability to regenerate organs. From the information so far available, it would appear that the signaling pathways that control the development of skeletal elements are recapitulated in regenerating antlers. This apparent lack of any specific 'antlerogenic molecular machinery' suggests that the secret of deers' ability to regenerate antlers lies in the particular cues to which multipotential progenitor/stem cells in an antler's 'regeneration territory' are exposed. This in turn suggests that with appropriate manipulation of the environment, pluripotential cells in other adult mammalian tissues could be stimulated to increase the healing capacity of organs, even if not to regenerate them completely. The need for replacement organs in humans is substantial. The benefits of increasing individuals' own capacity for regeneration and repair are self evident.

Proteome analysis of red deer antlers

Deer antlers are the only mammalian organs capable of repeated regeneration. Although antlers are known to develop from pedicles, which arise from antlerogenic cells of cranial periosteum, their developmental process is not fully elucidated. For example, while endocrine and environmental factors influence the antler development, it is still unclear which signaling pathways are involved in the transduction of such stimuli. To study the developmental process of antlers and identify proteins functioning in their growth, we have established proteome maps of red deer (Cervus elaphus) antlers. With two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization mass spectrometry, we analyzed more than 800 protein spots and identified approximately 130 individual proteins derived from the growing tip of antlers. The overall profile of the antler proteome was dissimilar to those of other types of tissue. Also comparison of proteomes derived from proximal bony tissue and the growing tip of antlers revealed substantial differences. Moreover several cell growth or signaling-related proteins are expressed exclusively in the growing tip, suggesting that these proteins function in the growth and differentiation of antlers. Currently, using the antler proteome maps, we are actively searching for the regulatory factor(s) that may control the antler development.

Exploring the mechanisms regulating regeneration of deer antlers

Deer antlers are the only mammalian appendages capable of repeated rounds of regeneration; every year they are shed and regrow from a blastema into large branched structures of cartilage and bone that are used for fighting and display. Longitudinal growth is by a process of modified endochondral ossification and in some species this can exceed 2 cm per day, representing the fastest rate of organ growth in the animal kingdom. However, despite their value as a unique model of mammalian regeneration the underlying mechanisms remain poorly understood. We review what is currently known about the local and systemic regulation of antler regeneration and some of the many unsolved questions of antler physiology are discussed. Molecules that we have identified as having potentially important local roles in antlers include parathyroid hormone-related peptide and retinoic acid (RA). Both are present in the blastema and in the rapidly growing antler where they regulate the differentiation of chondrocytes, osteoblasts and osteoclasts in vitro. Recent studies have shown that blockade of RA signalling can alter cellular differentiation in the blastema in vivo. The trigger that regulates the expression of these local signals is likely to be changing levels of sex steroids because the process of antler regeneration is linked to the reproductive cycle. The natural assumption has been that the most important hormone is testosterone, however, at a cellular level oestrogen may be a more significant regulator. Our data suggest that exogenous oestrogen acts as a 'brake', inhibiting the proliferation of progenitor cells in the antler tip while stimulating their differentiation, thus inhibiting continued growth. Deciphering the mechanism(s) by which sex steroids regulate cell-cycle progression and cellular differentiation in antlers may help to address why regeneration is limited in other mammalian tissues.

The effects of elk velvet antler consumption on the rat: development, behavior, toxicity and the activity of liver gamma-glutamyltranspeptidase

The effect of exposure to, followed by consumption of, a diet containing 10% powdered elk velvet antler (EVA) from the 18th day of gestation to the 88th day after birth was examined in male and female Fischer 344 rats. There were no teratogenic effects of EVA exposure in utero or differences in birth outcomes between pups born to regular chow fed and EVA chow fed dams. Growth curves of the EVA fed rats were identical to those of regular chow fed rats, as were developmental milestones of pinna development and eye-opening. Acoustical startle and righting reflexes, developmental and behavioral indices, were identical. Blood glucose levels were comparable in EVA chow fed and regular chow fed rats, indicating that EVA is without effect on glucose balance. There were no signs of toxicity in the EVA chow fed compared to regular chow fed rats as judged from plasma enzyme markers of liver damage: plasma levels of alanine aminotransferase were 50% lower in EVA chow fed rats compared to regular chow fed rats; and plasma levels of gamma-glutamyltranspeptidase (gammaGT) were the same. The activity of gammaGT displayed a decrease in the livers of EVA chow fed rats, more so in the male (22%) than in the female (14%), suggestive of an androgenic effect. A possible hepatobeneficial effect of the EVA induced decrease in liver gammaGT is discussed. In summary, dietary10% EVA chow is without long term effect on growth, development and behavior is non-toxic and may be hepatobeneficial.

Recapitulation of the parathyroid hormone-related peptide-Indian hedgehog pathway in the regenerating deer antler

Parathyroid hormone (PTH)-related peptide (PTHrP) and the PTH/PTHrP receptor (PPR) play an essential role in controlling growth plate development. The aim of the present study was to use the deer antler as a model to determine whether PTHrP and PPR may also have a function in regulating cartilage and bone regeneration in an adult mammal. Antlers are the only mammalian appendages that are able to undergo repeated cycles of regeneration, and their growth from a blastema involves a modified endochondral process. Immunohistochemistry was used to establish sites of localization of PTHrP and PPR in antlers at different stages of development. The pattern of Indian Hedgehog (IHH) and transforming growth factor-beta1 (TGF beta1) distribution was also investigated, because PTHrP expression in the developing limb is regulated by IHH and during embryonic growth plate formation TGF beta1 acts upstream of PTHrP to regulate the rate of chondrocyte differentiation. In the antler blastema (<10 days of development), PTHrP, PPR, and TGF beta1 were localized in epidermis, dermis, regenerating epithelium, and in mesenchymal cells but IHH expression was not detected. In the rapidly growing antler (weeks 4-8 of development), PTHrP, PPR, and TGF beta1 were localized in skin, perichondrium, undifferentiated mesenchyme, recently differentiated chondrocytes, and in perivascular cells in cartilage but not in fully differentiated hyperytrophic chondrocytes. IHH was restricted to recently differentiated chondrocytes and to perivascular cells in cartilage. In mineralized cartilage and bone, PTHrP, PPR, IHH, and TGF beta1 were immunolocalized in perivascular cells and differentiated osteoblasts. PTHrP and PPR were also present in the periosteum. TGF beta1 in vitro stimulated PTHrP synthesis by cells from blastema, perichondrium, and cartilage. The findings of this study suggest that molecules which regulate embryonic skeletal development and postnatal epiphyseal growth may also control blastema formation, chondrogenesis, and bone formation in the regenerating deer antler. This finding is further evidence that developmental signaling pathways are recapitulated during adult mammalian bone regeneration.

Sampling technique to discriminate the different tissue layers of growing antler tips for gene discovery

The utilization of a deer antler model to study gene expression in tissues undergoing rapid growth has been hampered by an inability to sample the different tissue types. We report here a standardized procedure to identify different tissue types in growing antler tips and demonstrate that it can help in the classification of expressed sequence tags (ESTs). The procedure was developed using observable morphological markers within the unstained tissue at collection, and was validated by histological assessments and virtual Northern blotting. Four red deer antlers were collected at 60 days of growth and the tips (top 5 cm) were then removed. The following observable markers were identified distoproximally: the dermis (4.86 mm), the subdermal bulge (2.90 mm), the discrete columns (6.50 mm), the transition zone (a mixture of discrete and continuous columns) (3.22 mm), and the continuous columns (8.00 mm). The histological examination showed that these markers corresponded to the dermis, reserve mesenchyme, precartilage, transitional tissue from precartilage to cartilage, and cartilage, respectively. The gene expression studies revealed that these morphologically identified layers were functionally distinct tissue types and had distinct gene expression profiles. We believe that precisely defining these tissue types in growing antler tips will greatly facilitate new discoveries in this exciting field.

Detection of growth factors in the testis of roe deer (Capreolus capreolus)

Roe deer is a seasonal breeder characterised by a short rutting season in summer. Mature males show synchronised cycles of testicular involution and recrudescence. Therefore, this species is a valuable model to study seasonal regulation of spermatogenesis in ruminants. It is hypothesised that a time-dependent production of testicular growth factors is required to regulate seasonal changes in testis growth and spermatogenesis. To identify potential candidates, total RNA from roe deer testis tissue was extracted at three different seasonal periods (April, August, December), and using RT-PCR the presence of several growth factors (aFGF, bFGF, IGF-I, IGF-II, TGF-alpha, TGF-beta1, TGF-beta3 and two isoforms of VEGF) was detected. Sequencing of the growth factor PCR fragments revealed a high sequence homology between cattle and roe deer. To further explore the expression patterns of the identified growth factors in roe deer their expression levels were standardised using glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene expression. The study demonstrates the expression of several growth factors in roe deer testis and supports the assumption of their seasonally diverse regulation. These results provide the basis to investigate the role of growth factors in the regulation of circannual changes of testicular activity.