Labeling studies on cortical bone formation in the antlers of red deer (Cervus elaphus)

Red deer (Cervus elaphus) antler myiasis caused by Prochyliza nigrimanus (Meigen 1826)

Antlers are bony structures that undergo regular annual growth, mineralisation and casting phases, representing only mammalian organs capable of full regeneration. Myiasis is infestation of live vertebrates with dipterous larvae. We sampled mineralised antlers from a red deer spiker stag 2 months after velvet shedding, divided it into three segments and fixed in 10% neutral buffered formalin. After demineralisation, samples were embedded in paraffin and sliced to a thickness of 6 µm. Tissue sections were stained with hematoxylin-eosin (HE), a modified staining to show the ossification process, toluidin blue and Masson's trichrome staining. Smears of liquid content from the antlers were made and stained with May-Grünwald Giemsa. Larvae were separated from segments and preserved in 70% ethanol for identification. Macroscopically, some parts of the antler tips were lacking the compact part. Microscopically, within the Haversian and Volkmann canals, a large number of bacteria, scarce protein content and remnants of red blood corpuscles were visible. In the area of cancellous bone, cross-sectioned larvae were present. A large quantity of bacteria and a few degraded red blood corpuscles were visible on the smear made of liquid from the antlers. For morphological identification, three larvae were examined: two were third-instar larvae (L3), while one was a first instar larva (L1). Based on the shape of the cephaloskeleton, L3 was identified as Prochyliza nigrimanus and confirmed using molecular tools. To the extent of the authors' knowledge, this is the first record of Prochyliza nigrimanus in non-casted hard red deer antlers and the first description of this species in Croatia.

Bone metabolism associated with annual antler regeneration: a deer insight into osteoporosis reversal

Osteoporosis, a metabolic disorder, remains challenging to treat due to limited understanding of its underlying mechanism. The annual cycle of "cyclic physiological osteoporosis (CPO)" and its full reversal in male deer represents a unique natural model for studying this condition. Deer antlers, weighing up to 25 kg/pair, derive over 60% of their mineral contents from deer skeleton during mineralization. Based on the literature, we propose to divide CPO and its reversal into two phases: Phase I (approximately 115 days): from hard antler casting to the end of antler linear growth, marked by simultaneous robust antler ossification and CPO development; and Phase II (up to 165 days): from end of Phase I to the onset of antler skin shedding, characterized by complete antler mineralization and CPO reversal. This review analyzes the paradoxical occurrence of robust antler ossification and skeleton CPO within the same endocrine microenvironment during phase I; total antler mineralization and full reversal of deer skeleton CPO in phase II. Furthermore, we will discuss potential insights for osteoporosis treatment using deer materials from the period of Phase II. Our goal is to identify novel substances and therapies that could be applied in clinical setting to effectively treat osteoporosis.

General Direct Anticancer Effects of Deer Growing Antler Extract in Several Tumour Cell Lines, and Immune System-Mediated Effects in Xenograft Glioblastoma

Deer antlers are the fastest growing tissue. Because they are based on proto-oncogenes, to avoid the risk of cancer, antlers evolved strong anticancer mechanisms, and thus their extract (DVA) is effective also against the few human tumours studied so far. We assessed whether DVA is a general anticancer compound by testing the direct effects in cells of different tumours: glioblastoma (GBM; lines U87MG and U251), colorectal (CRC; lines DLD-1, HT-29, SW480, and SW620), breast cancer (BRCA; lines MCF7, SKBR3, and PA00), and leukaemia (THP-1). DVA reduced the viability of tumours but not healthy cells (NHC; lines 293T and HaCaT). Mobility decreased at least for the longest test (72 h). Intraperitoneal/oral 200 mg DVA/kg administration in GBM xenograft mice for 28 d reduced tumour weight by 66.3% and 61.4% respectively, and it also reduced spleen weight (43.8%). In addition, tumours treated with DVA showed symptoms of liquefactive necrosis. Serum cytokines showed DVA up-regulated factors related to tumour fighting and down-regulated those related to inducing immune tolerance to the tumour. DVA shows general anticancer effects in the lines tested and, in GBM mice, also strong indirect effects apparently mediated by the immune system. DVA may contain a future anticancer medicine without secondary effects.

Bone resorption and formation in the pedicles of European roe deer (Capreolus capreolus) in relation to the antler cycle-A morphological and microanalytical study

We analyzed pedicle bone from roe bucks that had died around antler casting or shortly before or during the rutting period. Pedicles obtained around antler casting were highly porous and showed signs of intense osteoclastic activity that had caused the formation of an abscission line. Following the detachment of the antler plus a portion of pedicle bone, osteoclastic activity in the pedicles continued for some time, and new bone was deposited onto the separation plane of the pedicle stump, leading to partial pedicle restoration. Pedicles obtained around the rutting period were compact structures. The newly formed, often very large secondary osteons, which had filled the resorption cavities, exhibited a lower mineral density than the persisting older bone. The middle zones of the lamellar infilling frequently showed hypomineralized lamellae and enlarged osteocyte lacunae. This indicates a deficiency in mineral elements during the formation of these zones that occurred along with peak antler mineralization. We suggest that growing antlers and compacting pedicles compete for mineral elements, with the rapidly growing antlers being the more effective sinks. The competition between the two simultaneously mineralizing structures is probably more severe in Capreolus capreolus than in other cervids. This is because roe bucks regrow their antlers during late autumn and winter, a period of limited food and associated mineral supply. The pedicle is a heavily remodeled bone structure with distinct seasonal variation in porosity. Pedicle remodeling differs in several aspects from the normal bone remodeling process in the mammalian skeleton.

Extracellular Vesicles Derived From 3D Cultured Antler Stem Cells Serve as a New Drug Vehicle in Osteosarcoma Treatment

Extracellular vesicles (EVs) from antler reserve mesenchymal (RM) cells play an important role in the paracrine regulation during rapid growth of antler without forming a tumor; therefore, RM-EVs become novel materials for anti-tumor studies, such as osteosarcoma treatment. However, the problem of low production of RM-EVs in traditional 2D culture limits its mechanism research and application. In this study, we established an optimal 3D culture system for antler RM cells to produce EVs (3D-RM-EVs). Morphology and property of harvested 3D-RM-EVs were normal compared with EVs from conventional 2D culture, and the miRNA profile in them was basically the same through transcriptome sequencing analysis. Based on the same number of RM cells, the volume of the culture medium collected by 3D cultural system concentrated nearly 30 times, making it more convenient for subsequent purification. In addition, EVs were harvested 30 times in 3D cultural system, greatly increasing the total amount of EVs (harvested a total of 2-3 times in 2D culture). Although 3D-RM-EVs had a limited inhibitory effect on the proliferation of K7M2 cells, the inhibition effect of 3D-RM-EVs loaded drugs (Ifosfamide + Etoposide) were more significant than that of positive drug group alone (P < 0.05). Furthermore, in vivo studies showed that 3D-RM-EVs loaded drugs (Ifosfamide + Etoposide) had the most significant tumor inhibition effect, with decreased tumor size, and could slow down body weight loss compared with Ifosfamide + Etoposide (IFO + ET) group. These results demonstrated that 3D-RM-EVs were efficiently prepared from antler RM cells and were effective as drug vehicles for the treatment of osteosarcoma.

Concentration of Macroelements and Trace Elements in Farmed Fallow Deer Antlers Depending on Age

The mineral content of the antlers reflects the nutritional status and specific stage of bone growth in cervid males. Therefore, this research aimed to analyze the concentration of Ca, P, Mg, K, Na, Li, V, Cr, Mn, Co, Cu, Zn, Se and Mo in three characteristic antler positions selected based on the observation of fights between males. These were compared between farmed fallow deer (Dama dama) of different ages. The mineral compositions of tissues were analyzed using inductively coupled plasma mass spectrometry. The highest mean concentrations of macroelements (except K) were recorded in the youngest animals aged 2 or 3 years in the proximal position of the antlers. With age and distance from the skull, Ca, P, Mg and Na contents decreased, while K increased. Higher mean concentrations of most trace elements (Cr, Mn, Co, Cu, Zn) were recorded in 3-year-old animals in antler distal positions. With an increase in the age, body mass and antler mass of fallow deer, the concentration of Ca, P, Mg, K, Mn, Cu and Zn decreased (−0.414 ≤ R ≤ −0.737, p < 0.05) in the studied tissue, whereas Li increased (0.470 ≤ R ≤ 0.681, p < 0.05). The obtained results confirm that the antlers’ chemical composition changes with age, also changing the Ca:P ratio.

Distribution, structure, and mineralization of calcified cartilage remnants in hard antlers

Antlers are paired deciduous bony cranial appendages of deer that undergo a regular cycle of growth, death and casting, and constitute the most rapidly growing bones in mammals. Antler growth occurs in an appositional mode and involves a modified form of endochondral ossification. In endochondral bones, calcified cartilage is typically a transient tissue that is eventually completely replaced by bone tissue. We studied the distribution and characteristics of calcified cartilage in hard antlers from three deer species (Capreolus capreolus, Cervus elaphus, Dama dama), i.e., in antlers from which the skin (velvet) had been shed. Remnants of calcified cartilage were regularly present as part of the trabecular framework in the late formed, distal antler portions in all three species, whereas this tissue was largely or completely missing in the more proximal antler portions. The presence of calcified cartilage remnants in the distal antler portions is attributed to the limited antler lifespan of only a few months, which is also the reason for the virtual lack of bone remodeling in antlers. The calcified cartilage matrix was more highly mineralized than the antler bone matrix. Mineralized deposits were observed in some chondrocyte lacunae and occasionally also in osteocyte lacunae, a phenomenon that has not previously been reported in antlers. Using synchrotron radiation-induced X-ray fluorescence (SR-XRF) mapping, we further demonstrated increased zinc concentrations in cement lines, along the inner borders of incompletely formed primary osteons, along the walls of partly or completely mineral-occluded chondrocyte and osteocyte lacunae, and in intralacunar mineralized deposits. The present study demonstrates that antlers are a promising model for studying the mineralization of cartilage and bone matrices and the formation of mineralized deposits in chondrocyte and osteocyte lacunae.

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Remnants of calcified cartilage are regularly present in hard antlers of deer.

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Preservation of calcified cartilage is caused by the short lifespan of antlers.

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Calcified cartilage of antlers is more highly mineralized than antler bone.

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Mineralized deposits were observed in chondrocyte and osteocyte lacunae of antlers.

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SR-XRF showed increased Zn-concentration in cement lines and intralacunar deposits.

Factors affecting antler growth period and casting date in red deer

Antlers are unique structures because they grow rapidly and are cast annually, representing an important energetic and mineral cost for deer. Variables related to the timing of antler growth, such as date of antler casting and length of growth period, therefore, should be affected by somatic resources and availability of food. We examined the effects of body and antler weight, age, and climatic variables, on antler casting date and the period of time antlers were grown as well as possible random effects of individual, year, cohort, and pedigree, based on 244 antlers in a population of 109 males of Iberian red deer (Cervus elaphus) over a 17-year study from 1999 to 2016. Body weight affected casting date, with heavier males casting antlers earlier than lighter males. Antlers also grew faster and were cast earlier among older males than young males. Antler weight influenced casting date and the duration of the growth period: males with heavier antlers cast them earlier and grow them faster than males with light antlers. Nevertheless, age and antler weight interacted; as such, older males grew their antlers slower and delay casting date because they produce heavier antlers, in contrast to younger males, where those with the heaviest antlers grow them faster and cast first. The date of the end of antler growth also influenced casting date, so that antlers that took the longest to develop were cast later than those that finished growing early. We conclude that older and heavier males cast their antlers earlier and grow them faster than younger and lighter males, likely to correlate the subsequent antler growth with the spring peak in plant nutrients, but that this early development is limited physiologically by the size of the antlers.

The consequences of living longer-Effects of an experimentally extended velvet antler phase on the histomorphology of antler bone in fallow deer (Dama dama)

Antlers are periodically regenerated paired cranial appendages of male deer (both sexes in reindeer) that constitute the fastest-growing bones in the animal kingdom. The annual antler cycle of male deer is linked to testicular activity and largely controlled by seasonal fluctuations of testosterone concentrations in their blood. We studied the effects of an experimental doubling (to eight months) of the velvet antler phase, during which the antlers are covered by skin (velvet), on the histomorphology of antler bone in three adult fallow bucks. Extension of the velvet antler phase in the experimental animals had been caused by administration of the antiandrogen cyproterone acetate (CPA). The distal portions of the antlers from two of the CPA-treated bucks exhibited partial sequestration of the antler cortex, with the separation plane typically located along the border between cortex and spongiosa. It is hypothesized that this was caused by cortical necrosis due to severe ischemia during later stages of the extended velvet antler phase. In places, new cancellous bone had been deposited on the resorption surface of the spongiosa, indicating a regeneration process. Normal fallow deer antlers ("controls") from this and a previous study, that is, antlers with a timespan of about four months between onset of new antler growth and velvet shedding, exhibited no or only minor bone remodeling and still contained remnants of calcified cartilage in their distal portions. In contrast, the antlers of the three CPA-treated bucks showed evidence (secondary osteons and resorption cavities) of marked bone remodeling along their entire length and lacked remnants of calcified cartilage. Our results underscore that the typical histological features of antler bone reflect its short-lived nature. Antlers are not mechanically loaded during the velvet stage, and it is presently unclear what triggered remodeling activity in the antlers whose lifespan had been experimentally extended.

Comparison of the accumulation of macro- and microelements in the bone marrow and bone of wild and farmed red deer (Cervus elaphus)

Background

The cells of the entire body, including the skeletal system, especially of young animals, may derive from the bone marrow in which they multiply. Therefore, it is important to assess whether the diet and quality of life of deer have a significant impact on the elemental composition of bone and bone marrow, which can directly affect their health and growth. The aim of this study was to determine the concentrations of macro- (Ca, calcium, P, phosphorus, Mg, magnesium, K, potassium, Na, sodium) and microelements (Li, lithium, Cr, chromium, Mn, manganese, Co, cobalt, Cu, copper, Zn, zinc, Se, selenium, Mo, molybdenum, and Sn, tin) accumulated in the bone marrow and bones of deer (Cervus elaphus). The study was carried out on 15 young stags divided into two groups: farmed and wild animals. The concentrations of macro- and microelements were analysed using the inductively coupled plasma mass spectrometry technique. This research expands our knowledge on this topic, which so far has not been extensively studied.

Results

The mean content of K, Na, Zn and Se in the bone marrow of farmed animals was significantly higher than in wild deer, whereas the mean content of Ca, P, Mg, K, Na and Li in the bones was higher in wild animals than in farmed individuals (p < 0.05). In addition, the mean concentration of Cr, Mn, Cu, Se and Mo in the bones of the analysed animals differed significantly (p < 0.05) and was higher in the farmed deer. The mean concentration of Se in the bone marrow of wild deer decreased with the increase of the body weight (p < 0.05). In turn, the mean content of Mn in the bone marrow and of Mo in the bones of the animals was significantly positively correlated with the animals’ body weight (p < 0.05).

Conclusions

The obtained results indicated different levels of micro- and macro-components in the body of farmed and wild deer, though without clear and strong variations. Generally, the higher level of macronutrients in the bones of wild deer may be related to the higher physiological importance of these minerals for life activities in the natural environment and to the limited supply of balanced food. On the other hand, the higher levels of microelements in the tissues of farmed animals may result from their significantly better nutritional status in the first year of life, achieved through appropriate nutrition as well as diet supplementation of adult females.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-021-03041-2.

SWATH-MS Quantitative Proteomic Analysis of Deer Antler from Two Regenerating and Mineralizing Sections

Simple Summary

Deer antler is a unique and astonishing case of annual regeneration in mammalians. Several studies have pointed out the potential for use of velvet antler extract as a nutraceutical supplement, among others, because of its anti-cancer activity. The study of antler regeneration and growth allow us to identify the main proteins and regulatory pathways involved in cell differentiation and regeneration. For this purpose, two sections of antlers (tips and middle sections) using ribs as controls were analyzed from a proteomic point of view. A total of 259 proteins mainly associated with antioxidant mechanisms and Wnt signalling pathways could be responsible for deer antler regeneration and these proteins may be linked to human health benefits. Further studies should be focused on discovering which proteins from velvet antler extracts are associated with these beneficial effects.

Abstract

Antlers are the only organ in the mammalian body that regenerates each year. They can reach growth rates of 1–3 cm/day in length and create more than 20 cm²/day of skin in the antler tips (their growth centers). Previous proteomic studies regarding antlers have focused on antler growth centers (tips) compared to the standard bone to detect the proteins involved in tissue growth. However, proteins of cell differentiation and regeneration will be more accurately detected considering more growing tissues. Thus, we set out to compare proteins expressed in antler tips (the highest metabolism rate and cell differentiation) vs. middle sections (moderate cell growth involving bone calcification), using ribs as controls. Samples were obtained in mid-June with antlers’ phenology corresponding to the middle of their growth period. Quantitative proteomic analysis identified 259 differentially abundant proteins mainly associated with antioxidant metabolic mechanisms, protein formation and Wnt signalling pathway, meanwhile, the mid antler section was linked to blood proteins. The high metabolic rate and subsequent risk of oxidative stress also seem to have resulted in strong antioxidant mechanisms. These results suggest that redox regulation of proteins is a key factor in the model of deer antler regeneration.

The intriguing giant deer from the Bate cave (Crete): could paleohistological evidence question its taxonomy and nomenclature?

The research describes for the first time a possible case of pituitary gigantism in fossil mammals, precisely in deer. The pathology was detected in 2 long bones (tibia and metatarsus) belonging to an individual of an unusual large size found at the Bate cave (Rethymnon, Northern Crete). It formed the basis of Candiacervus major, the largest among the endemic deer species recorded in the Pleistocene-Early Holocene of Crete. Radiological and histomorphological examinations highlighted a reduction in cortical bone thickness and the presence of wide lacunae inside of the bone tissue. The pathological conditions suggest a pituitary gigantism diagnosis also supported by some morphological evidence, such as the extremely elongated distal part of the metatarsal diaphysis, the proportionally small proximal epiphysis, and some bone gracility. The diagnosis of a case of pituitary gigantism as presumed responsible for the extraordinary elongation of the tibia and the metatarsal bone is intriguing as they are, respectively, the paratype and the holotype of the C. major. The species represents a case of a deviation from the "island rule" in Pleistocene large mammals. The new evidence recommends a taxonomic and nomenclatural revision of this species. The main outcomes of this research are as follows: (i) a case of pituitary gigantism is described for the first time in an extinct mammal; (ii) it is underlined that paleohistology may provide interesting clues for disentangling taxonomic and nomenclatural issues; (iii) one of the very few cases of gigantism in insular mammals is being questioned.

Anti-tumour activity of deer growing antlers and its potential applications in the treatment of malignant gliomas

A recent study showed that antlers have evolved a high rate of growth due to the expression of proto-oncogenes and that they have also evolved to express several tumour suppressor genes to control the risk of cancer. This may explain why deer antler velvet (DAV) extract shows anti-tumour activity. The fast growth of antler innervation through the velvet in close association to blood vessels provides a unique environment to study the fast but non-cancerous proliferation of heterogeneous cell populations. We set out to study the anti-cancer effect of DAV in glioblastoma (GB) cell lines in comparison with temozolomide, a chemotherapeutic drug used to treat high-grade brain tumours. Here we report, for the first time, that DAV extract from the tip, but not from mid-parts of the antler, exhibits an anti-tumour effect in GB cell lines (T98G and A172) while being non-toxic in non-cancerous cell lines (HEK293 and HACAT). In T98G cells, DAV treatment showed reduced proliferation (37.5%) and colony-formation capacity (84%), inhibited migration (39%), induced changes in cell cycle progression, and promoted apoptosis. The anticancer activity of DAV extract as demonstrated by these results may provide a new therapeutic strategy for GB treatment.

Antiquity and fundamental processes of the antler cycle in Cervidae (Mammalia)

The origins of the regenerative nature of antlers, being branched and deciduous apophyseal appendages of frontal bones of cervid artiodactyls, have long been associated with permanent evolutionary precursors. In this study, we provide novel insight into growth modes of evolutionary early antlers. We analysed a total of 34 early antlers affiliated to ten species, including the oldest known, dating from the early and middle Miocene (approx. 18 to 12 million years old) of Europe. Our findings provide empirical data from the fossil record to demonstrate that growth patterns and a regular cycle of necrosis, abscission and regeneration are consistent with data from modern antlers. The diverse histological analyses indicate that primary processes and mechanisms of the modern antler cycle were not gradually acquired during evolution, but were fundamental from the earliest record of antler evolution and, hence, explanations why deer shed antlers have to be rooted in basic histogenetic mechanisms. The previous interpretation that proximal circular protuberances, burrs, are the categorical traits for ephemerality is refuted.

Bilateral antler sequestration above the coronet in a red deer (Cervus elaphus) stag-Insights into the process of antler casting

This paper reports a case of delayed velvet shedding and bilateral premature antler casting above the coronets in a young adult red deer stag from Germany. Based on the established role of testosterone in the control of the antler cycle, the antler abnormality is considered to have been the result of a (temporary) androgen deficiency. The basal surfaces (separation planes or seals) of the cast antlers were markedly concave. Scanning electron microscopy revealed that the separation plane was densely covered with Howship's lacunae, denoting intense osteoclastic activity along the border between the proximal (living) and distal (dead) antler portions. Our observations and those of previous studies indicate that antler casting does not occur at a pre-determined separation plane, but along the border between living and dead bone, regardless of the position of this border within the cranial appendages. This is a major difference to autotomy of (living) appendages at fixed breakage planes, as it occurs for instance in lizard tails.

Ultrasound speed in red deer antlers: a non–invasive correlate of density and a potential index of relative qualit

Deer antlers can be used as an index of individual performance both in ecological and productive contexts. Their quality is often measured only by their biometrical features, such as size, asymmetry or weight. Mechanic characteristics cannot normally be measured without destroying the antler and hence losing the commercial value of the trophies. Here, we studied ultrasonic velocities, density, and tensile strength across various sections of cast antlers of Iberian red deer (Cervus elaphus hispanicus). We found that the speed value depended on the section of the antler and the propagation direction. For antler sections, velocities were lowest for mid–beam and highest for brow tine. Results were similar for density and indirect tensile strength, probably related to differences in functionality among antler sections. Density explained most of the variability of ultrasound–speed. The time elapsed from antler shed affected density more than ultrasound speed. The indirect tensile strength showed a non–linear, decelerating relationship with ultrasound speed. We discuss the applications of ultrasound speed as a non–invasive tool to measure density and physical properties of antlers and antler sections, and their potential use as an index of quality.

What do rates of deposition of dental cementum tell us? Functional and evolutionary hypotheses in red deer

Cementum is a bone connective tissue that provides a flexible attachment for the tooth to the alveolar bone in many mammalian species. It does not undergo continuous remodelling, unlike non-dental bone, which combined with its growth pattern of seasonal layering makes this tissue uniquely suitable as a proxy for tracking changes in body repair investment throughout an animal´s life. We tested functional and sexual selection hypotheses on the rate of cementum deposition related to the highly polygynous mating strategy of red deer. We used a sample of 156 first lower molars from wild Scottish red deer of known age between 1 and 17 years old, approximately balanced by sex and age class. Cementum deposition on the inter-radicular pad increased with age at a constant average rate of 0.26 mm per year, with no significant differences between sexes. Cementum deposition was independent of (i) tooth wear, other than that associated with age, and (ii) enamel and dentine micro-hardness. The results partially supported the hypothesis that the main function of cementum is the repositioning of the tooth to maintain opposing teeth in occlusion. However, teeth that had more wear or males´ teeth that had faster rates of tooth wear than those of females did not present the expected higher rates of cementum deposition.

Formation, structure, and function of extra-skeletal bones in mammals

This review describes the formation, structure, and function of bony compartments in antlers, horns, ossicones, osteoderm and the os penis/os clitoris (collectively referred to herein as AHOOO structures) in extant mammals. AHOOOs are extra-skeletal bones that originate from subcutaneous (dermal) tissues in a wide variety of mammals, and this review elaborates on the co-development of the bone and skin in these structures. During foetal stages, primordial cells for the bony compartments arise in subcutaneous tissues. The epithelial-mesenchymal transition is assumed to play a key role in the differentiation of bone, cartilage, skin and other tissues in AHOOO structures. AHOOO ossification takes place after skeletal bone formation, and may depend on sexual maturity. Skin keratinization occurs in tandem with ossification and may be under the control of androgens. Both endochondral and intramembranous ossification participate in bony compartment formation. There is variation in gradients of density in different AHOOO structures. These gradients, which vary according to function and species, primarily reduce mechanical stress. Anchorage of AHOOOs to their surrounding tissues fortifies these structures and is accomplished by bone-bone fusion and Sharpey fibres. The presence of the integument is essential for the protection and function of the bony compartments. Three major functions can be attributed to AHOOOs: mechanical, visual, and thermoregulatory. This review provides the first extensive comparative description of the skeletal and integumentary systems of AHOOOs in a variety of mammals.

Ontogenetic changes of tissue compartmentalization and bone type distribution in the humerus of Soay sheep

We studied ontogenetic changes of histomorphological features and bone type distribution in the humeral midshaft region of Soay sheep from three postnatal age classes (13, 25, and 33 months). Our study demonstrated a marked change of bone type distribution in the humeri with age. In the cortical midshaft region of 13-month-old individuals, periosteal fibrolamellar bone was the dominating bone type. This indicates a rapid bone growth during the first year of life, which was only interrupted by a seasonal growth arrest in the animals' first winter. In individuals from the two older age classes, periosteal lamellar-zonal bone and intermediate fibrolamellar bone had been formed at the periosteal surface, and endosteal lamellar-zonal bone at the endosteal surface. These bone types are indicative of a reduced bone growth rate. A marked reduction in radial growth was already recorded in the 25-month-old individuals. Distribution and extent of secondary bone showed a marked bilateral symmetry in the humeri of individual sheep. The presence of secondary bone was largely restricted to the anterior (cranial) and the medial cortical areas. This characteristic distribution of remodeling activity within the humeral cortex of sheep is consistent with the view that remodeling activity is largely caused by compressive stress. Our study further demonstrated the presence of a considerable cortical drift in the sheep humeri over the study period, with endosteal resorption occurring predominantly in the posterior (caudal) quadrant and formation of a prominent endosteal lamellar pocket in the anterior (cranial) and medial cortical quadrants.

Effects of supplementation with different levels of calcium and phosphorus on mineral content of first antler, bone, muscle, and liver of farmed fallow deer (Dama dama)

Nutrition is one of the main factors influencing physiological processes, e.g., growth and antler development, in Cervidae. The aim of this study was to demonstrate a possible effect of supplementation with different levels of calcium (Ca) and phosphorus (P) on the mineral composition of antlers and bones, and its effect on the content of macroelements — Ca, potassium (K), magnesium (Mg), sodium (Na), and P — in the muscle tissue, liver, and blood of farmed fallow deer fawns. The results show a positive effect of increased doses of Ca and P on body weight at the age of 14 mo. Additionally, there was a significant increase in the content of Ca, Mg, Na, and P in antlers and Ca, Na, and P in bones. The muscle tissue was characterised by a significant increase only in the content of Na, whereas Ca, K, and P levels increased significantly in the liver. In turn, the serum P content decreased significantly. Adequate Ca and P supplementation exerts a positive effect on the mineral composition of bones and whole antlers of farmed fallow deer fawns, and it enhances the concentrations of macroelements in tissues, which may constitute a reservoir used for future development of antlers. It also has a positive effect on body weight.

Antlers - Evolution, development, structure, composition, and biomechanics of an outstanding type of bone

Antlers are bony appendages of deer that undergo periodic regeneration from the top of permanent outgrowths (the pedicles) of the frontal bones. Of the "less familiar" bone types whose study was advocated by John Currey to gain a better understanding of structure-function relationships of mineralized tissues and organs, antlers were of special interest to him. The present review summarizes our current knowledge about the evolution, development, structure, mineralization, and biomechanics of antlers and how their formation is affected by environmental factors like nutrition. Furthermore, the potential role of antlers as a model in bone biology and several fields of biomedicine as well as their use as a monitoring tool in environmental studies are discussed.

Effect of age on nutritional properties of Iberian wild red deer meat

BACKGROUND

This study assessed the effect of age (L, less than 27 months old; M, from 27 to 42 months old; H, 43 months and older) on the fatty acid profile, cholesterol content, amino acid composition and mineral content of 150 Iberian wild red deer meat samples.

RESULTS

Intramuscular fat content increased (P < 0.05) with age (0.05 vs 0.12 vs 0.34% for L, M and H groups respectively), while cholesterol content decreased (P < 0.05) as the slaughter age increased (52.78 vs 48.72 vs 45.34 mg per 100 g meat for L, M and H groups respectively). The slaughter age showed differences among groups for saturated fatty acids, with the highest content in older animals (30.41 vs 34.55 vs 38.21% for L, M and H groups respectively), whereas younger deer displayed the highest polyunsaturated fatty acid levels (50.05 vs 45.24 vs 37.55% for L, M and H groups respectively). The n-6/n-3 ratio was more favorable (P < 0.05) for young and medium ages compared with that for older animals. In contrast, amino acid profile and mineral content were only slightly affected by age.

CONCLUSION

As a general conclusion, wild red deer meat could be considered a good alternative to red meats for human consumption. © 2018 Society of Chemical Industry.

Digit Tip Injuries: Current Treatment and Future Regenerative Paradigms

Over the past several decades there has been a profound increase in the understanding of tissue regeneration, driven largely by the observance of the tremendous regenerative capacity in lower order life forms, such as hydra and urodeles. However, it is known that humans and other mammals retain the ability to regenerate the distal phalanges of the digits after amputation. Despite the increased knowledge base on model organisms regarding regenerative paradigms, there is a lack of application of regenerative medicine techniques in clinical practice in regard to digit tip injury. Here, we review the current understanding of digit tip regeneration and discuss gaps that remain in translating regenerative medicine into clinical treatment of digit amputation.

Evolution of blood serum mineral composition during antler growth and rut as consequence of Cu supplementation in captive red deer and its effects in mature antler composition

In the present study we assessed the effects of Cu supplementation and antler growth stage on mineral composition of serum and hard antler in red deer fed a balanced diet. Correlations between minerals were analysed for serum, for antlers, and between serum versus mature antler. Blood samples were drawn at Days –36, 54, 132 and 197 of the start of antler growth (SAG). Hard antlers were cut at Day 165 from SAG. The Cu supplemented group (n = 9) was injected with 0.83 mg Cu/kg of bodyweight, whereas the control group (n = 9) was injected with a physiological saline solution, both every 42 days between Days –36 (Cu supplied after blood sampling) and 132 from SAG. Supplementation with Cu increased (P &lt; 0.05) the contents of P and Cu in serum but did not affect the antler mineral profile. Serum contents of Mg, Na, S, B and Cu increased during the antler growth, whereas contents of K, Al and Fe decreased in the same period (P &lt; 0.001). At Day 54 from SAG in Cu group, serum P content correlated negatively with antler Ca content whereas Zn of serum and antler correlated positively (P &lt; 0.05). The maximum number of correlations between the mineral profile of serum and hard antler was achieved at Day 132 from SAG (3.3, 4.7 and 12.9% for Days –36, 54 and 132, respectively). In conclusion, the analysis of specific minerals in serum could be used to detect in advance some mineral deficiencies in the antler.

Sika deer antler as a novel model to investigate dental implant healing: A pilot experimental study

Dental implants are important tools for restoring the loss of teeth. The rapid growth and periodic regeneration of antlers make Sika deer a good and less invasive alternative model for studying bone remodelling in mammals. We developed a special loading device for antlers and analysed the bone reaction around unloaded implants and under immediate loading conditions until osseointegration occurred. In micro-computed tomography images, the density of antler tissue around the implants increased as the loading time increased. This finding was histologically confirmed by the good osseointegration observed in unloaded and loaded specimens. Antler tissue displays a similar healing process to human bone. The use of an antler model is a promising alternative for implant studies that does not require animal sacrifice.

The bony horncore of the common eland (Taurotragus oryx): composition and mechanical properties of a spiral fighting structure

Horns are permanent structures projecting from the head of bovids, consisting of a bony horncore covered with a layer of skin and then a sheath of keratinous material showing variability of growth intensity based on nutrition. From the point of view of the horn's mechanical properties, the keratin sheath has been widely studied, but only a few studies have considered the complete structure of the horn and fewer studies have focused on the bony horncore and its characteristics. The latter showed the important role of the bony core, when cranial appendages are subject to mechanical stress (as happens during fighting). The mechanical properties of bone material, along with its mineral profile, are also important, because they can show effects of different factors, such as nutrition and mineral deficiencies in diet. For this reason, eight horncores of captive common eland male were sampled at four positions along the vertical axis of the horn. The main aim was to study variation in mechanical properties and the mineral content along the vertical axis of the horncores. We further analysed whether the spiral bony ridge present on eland horncores differs in any of the studied properties from adjacent parts of the horncore. In other antelopes, spiral ridges on the horns have been proposed to increase grip during wrestling between males. Cross-sections of the horncores were performed at four positions along the longitudinal axis and, for each position, two bone bars were extracted to be tested in impact and bending. Moreover, in the first sampling position (the closest position to the base) two bars were extracted from the spiralled bony area. The resulting fragments were used to measure ash content, bone density and mineral content. Results showed that horn bone decreased along the vertical axis, in ash (-36%), density (-32%), and in impact work 'U' (marginally significant but large effect: -48%). The concentration of several minerals decreased significantly (Mg, Cr, Mn and Tl by -33%, -25%, -31%, -43%, respectively) between the basal and the uppermost sampling site. The bone tissue of the horncore spiral compared with non-spiral bone of the same position showed a lower ash content (53% vs. 57%), Mg and Mn; in addition to showing approximately half values in work to peak force 'W', bending strength 'BS' and 'U', but not in Young's modulus of elasticity 'E'. In conclusion, similarly to the results in a totally different fighting bony structure, the antlers, the horncore of eland shows advantageous parameters in bone tissue of the base in respect to the tip, with higher values for mechanical properties, density and mineral profile. Moreover, the spiral bone tissue showed lower material mechanical properties. Probably the spiral tissue of the horn may have a role in deflecting potential cross-sectional fractures during wrestling. In addition, it may serve to improve the grip during wrestling, and we propose that it may also prevent risk of rotation of sheath with respect to internal bone not only in this, but also in other straight bovid horns.

Expression and regulation of Angiopoietins and their receptor Tie-2 in sika deer antler

The cartilage vascularization and chondrocyte survival are essential for endochondral ossification which occurs in the process of antler growth. Angiopoietins (Ang) is a family of major angiogenic growth factors and involved in regulating the vascularization. However, the expression and regulation of Angs in the antler are still unknown. The aim of this study is to localize the expression of Ang-1, Ang-2 and their receptor Tie-2 in sika deer antler using in situ hybridization and focused on analyzing the regulation of testosterone, estrogen, all-trans-retinoic acid (ATRA) and 9cRA on their expression in antler chondrocytes. The results showed that Ang-1, Ang-2 and Tie-2 were highly expressed in antler chondrocytes. Administration of testosterone to antler chondrocytes led to a notable increase in the expression of Ang-1 and Tie-2, and a reduction in the expression of Ang-2. The similar result was also observed after estrogen treatment. In contrast, ATRA and 9cRA could inhibit the expression of Ang-1 in antler chondrocytes and heighten the expression of Ang-2. Simultaneously, ATRA could downregulate the expression of Tie-2 in antler chondrocytes at 12 and 24 h, while 9cRA upregulate the expression of Tie-2 at 3 and 6 h. Collectively, Ang-1, Ang-2 and Tie-2 are expressed in antler chondrocytes and their expression can be affected by testosterone, estrogen, ATRA and 9cRA.

Multiple osteochondromas of the antlers and cranium in a free-ranging white-tailed deer (Odocoileus virginianus)

This paper reports a case of multiple osteochondromas affecting the antlers and the left zygomatic bone of a free-ranging adult white-tailed buck (Odocoileus virginianus) from Georgia, USA. Along with a few postcranial bones, the antlered cranium of the individual was found in a severely weathered condition and devoid of any soft tissue. The antlers exhibited five pedunculated exostoses that were composed of cancellous bone and, in their peripheral portions, also mineralized cartilage. The largest of the exostoses, located on the right antler, had a maximum circumference of 55 cm. The exostosis arising from the zygomatic bone was broad-based and much smaller than the exophytic outgrowths on the antlers. Diagnosis of the exostoses as osteochondromas was based on their overall morphology, the normal bone structure in their stalk regions, and the continuity of their spongiosa and cortex with the respective components of the parent bones. Antleromas, i.e., pathological outgrowths developing on antlers as a result of insufficient androgen production, were excluded in the differential diagnosis, based on (1) the apparent maturity and, except for the tumors, normal shape of the antlers and (2) the fact that exostosis formation had also affected the zygomatic bone. Previously only a single case of solitary osteochondroma of an antler has been described in the scientific literature. The case presented here is the first report of multiple osteochondromas in a deer. As antlers are regularly collected as trophies, and huge numbers of them are critically inspected each year, the fact that thus far only two cases of antler osteochondromas have been reported suggests that these tumors are very rare.

Spatially offset Raman spectroscopy for photon migration studies in bones with different mineralization levels

This study provides a deeper understanding of bone's optical properties which is essential to the development of SORS-based diagnostic tools.

Organic and mechanical properties of Cervidae antlers: a review

There is a resurgence of interest in the study of deer antlers. Recent research advocates their potential for use in bone xenografts. Using this working hypothesis, we can formulate many questions: do antlers really present unique or interesting mechanical properties, and if so, which factors affect these properties? Many other issues, including tissue compatibility, could be discussed; however, this article will focus on the biomechanical features of antlers. This paper reviews some answers found within current published material, and could help determine the optimal selection of some antlers for further experimental studies and clinical trials. Some general elements like anatomy and histology of deer antlers are briefly summarised. This paper will attempt to define the fundamental differences between skeletal bone and antler bone in terms of their organic and mechanical properties. We will then compare the previously published data, which details the mechanical properties of antlers from different species of Cervidae, by reviewing several aspects such as: sex; geographical situation; morphology; hydration state; and mineral composition. Some findings emerge: mechanical properties do not vary with gender or latitude, and the most important determining factor appears to be the species, alongside morphology and use of antlers. The state of hydration and mineral composition also has an influence on the mechanical properties of Cervidae antlers.

Nutrition of antler growth in deer

Stags are susceptible to the effects of nutrition at several stages during their lives and during the antler cycle. Nutrition during the in utero, post-natal (suckling) and yearling stages influences the size of spike antlers, and, generally, there is a close relationship between bodyweight and antler weight in stags aged up to 5 years. While antler size is not greatly affected by nutrition during the growth of immature (velvet) antler, it is influenced by body size and condition at casting, i.e. at the beginning of new antler growth. Antler growth appears to have a high priority for nutrients, especially energy, protein and calcium. Antler growth in adult stags is little affected by diet protein concentrations over 7%, but supplements of protected protein or methionine may improve antler growth. Substantial amounts of calcium and phosphorus are sequestered in antlers as they become mineralised, and calcium is withdrawn from the skeleton in support of this. Feeding programs to obtain good antler growth involve recognising the periods when juvenile stags are susceptible to under-nutrition, and providing sufficient nutrients to re-establish adequate body condition in adult stags between the end of the rut and antler casting.

Calcium orthophosphates (CaPO4): occurrence and properties

The present overview is intended to point the readers' attention to the important subject of calcium orthophosphates (CaPO4). This type of materials is of the special significance for the human beings because they represent the inorganic part of major normal (bones, teeth and antlers) and pathological (i.e., those appearing due to various diseases) calcified tissues of mammals. For example, atherosclerosis results in blood vessel blockage caused by a solid composite of cholesterol with CaPO4, while dental caries and osteoporosis mean a partial decalcification of teeth and bones, respectively, that results in replacement of a less soluble and harder biological apatite by more soluble and softer calcium hydrogenorthophosphates. Therefore, the processes of both normal and pathological calcifications are just an in vivo crystallization of CaPO4. Similarly, dental caries and osteoporosis might be considered as in vivo dissolution of CaPO4. In addition, natural CaPO4 are the major source of phosphorus, which is used to produce agricultural fertilizers, detergents and various phosphorus-containing chemicals. Thus, there is a great significance of CaPO4 for the humankind and, in this paper, an overview on the current knowledge on this subject is provided.

Manganese Supplementation in Deer under Balanced Diet Increases Impact Energy and Contents in Minerals of Antler Bone Tissue

Bone ash, collagen, Ca and P composition, are considered the main factors affecting mechanical properties in bones. However, a series of studies in bone and antler have shown that some trace minerals, such as manganese, may play a role whose importance exceeds what may be expected considering their low content. A previous study showed that a reduction in manganese in antlers during a year of late winter frosts led to generalized antler breakage in Spain, which included a reduction of 30% of cortical thickness, 27% reduction in impact energy, and 10% reduction in work to peak force. Starting for this observation, we experimentally studied the effects of manganese supplementation in adults and yearling (yearlings) red deer under a balanced diet. Subjects were 29 deer of different age classes (adult n = 19, yearlings n = 10) that were divided in a manganese injected group (n = 14) and a control group (n = 15). Antler content in ashes and minerals, intrinsic mechanical properties and cross section structure were examined at 4 points along the antler beam. A one way ANOVA (mean per antler) showed that in yearlings, manganese supplementation only increased its content and that of Fe. However, in adults, Mn supplementation increased the mean content per antler of Ca, Na, P, B, Co, Cu, K, Mn, Ni, Se (while Si content was reduced), and impact work but not Young's modulus of elasticity, bending strength or work to peak force. A GLM series on characteristics in the uppermost part examined in the antler, often showing physiological exhaustion and depletion of body stores, showed also a 16% increase in work to peak force in the antlers of the treated group. Thus, manganese supplementation altered mineral composition of antler and improved structure and some mechanical properties despite animals having a balanced diet.

Evolutionary Physiology of Bone: Bone Metabolism in Changing Environments

Bone evolved to serve many mechanical and physiological functions. Osteocytes and bone remodeling first appeared in the dermal skeleton of fish, and subsequently adapted to various challenges in terrestrial animals occupying diverse environments. This review discusses the physiology of bone and its role in mechanical and calcium homeostases from an evolutionary perspective. We review how bone physiology responds to changing environments and the adaptations to unique and extreme physiological conditions.

Element concentrations and element ratios in antler and pedicle bone of yearling red deer (Cervus elaphus) stags-a quantitative X-ray fluorescence study

The present study compared the concentrations of different elements (Ca, P, Mg, Sr, Ba, K, S, Zn, Mn) as well as Ca/P, Ca/Mg, Sr/Ca, and Ba/Ca ratios in hard antler and pedicle bone of yearling red deer stags (n = 11). Pedicles showed higher concentrations of calcium and phosphorus and a higher Ca/Mg ratio than antlers, while antlers exhibited higher concentrations of potassium, sulfur, and manganese as well as higher Ca/P, Sr/Ca, and Ba/Ca ratios. The findings indicate that antlers are less mineralized and show less maturation of their bone mineral than pedicles. Antlers also showed a higher intrasample variation of mineralization than pedicles, which can be related to the shorter life span of the (deciduous) antlers compared to the (permanent) pedicles. It is suggested that antler bone formation is stopped before the theoretically possible degree of mineralization and mineral maturation is reached, resulting in antler biomechanical properties (high bending strength and work to fracture) that are well suited for their role in intraspecific fighting. It is further suggested that the differences in Sr/Ca and Ba/Ca ratios of antlers and pedicles are related to the dietary shift from milk to vegetation in combination with an increasing intestinal discrimination against Sr and Ba with age, resulting in a less marked difference in these ratios than would be expected based on the dietary shift alone. The findings of our study underscore the suitability of antlers and pedicles as models of bone mineralization and the influence of different animal-related and/or external factors on this process.

The structure of pedicle and hard antler bone in the European roe deer (Capreolus capreolus): a light microscope and backscattered electron imaging study

Deer antlers are deciduous bony structures that develop from permanent frontal outgrowths, the pedicles. While growth and bone architecture of antlers have been studied in greater detail, information on pedicle formation and structure is scarce. The present study provides information on the structure of pedicle and hard antler bone in the European roe deer. A pronounced seasonal variation in pedicle architecture was observed, with high porosity around antler casting and a very compact bone structure during the hard antler stage. These observations suggest a corresponding marked variation also in the biomechanical properties of the pedicles. The seasonally alternating extensive resorption and formation processes make the pedicles of older deer heavily remodeled structures. Pedicles increase in thickness by apposition of primary bone that subsequently becomes replaced by secondary osteons. The antler cortex of roe deer is largely composed of a tubular framework of woven bone trabeculae with some remnants of mineralized cartilage, and primary osteons that have filled in the intertrabecular spaces. Secondary osteons are scarce, denoting little remodeling in antlers, which can be related to their short lifespan. The occurrence of cement lines around primary osteons indicates resorption on the trabecular scaffold prior to infilling of the intertrabecular spaces. The outer cortex showed a higher autofluorescence and a more immature structure than the main cortex, suggesting that it was secondarily formed by periosteal activity. Pedicles and antlers constitute a functional entity, and future histological and/or biomechanical studies should therefore consider both components of the cranial appendages.

Effects of feed supplementation on mineral composition, mechanical properties and structure in femurs of Iberian red deer hinds (Cervus elaphus hispanicus)

Few studies in wild animals have assessed changes in mineral profile in long bones and their implications for mechanical properties. We examined the effect of two diets differing in mineral content on the composition and mechanical properties of femora from two groups each with 13 free-ranging red deer hinds. Contents of Ca, P, Mg, K, Na, S, Cu, Fe, Mn, Se, Zn, B and Sr, Young's modulus of elasticity (E), bending strength and work of fracture were assessed in the proximal part of the diaphysis (PD) and the mid-diaphysis (MD). Whole body measures were also recorded on the hinds. Compared to animals on control diets, those on supplemented diets increased live weight by 6.5 kg and their kidney fat index (KFI), but not carcass weight, body or organ size, femur size or cortical thickness. Supplemental feeding increased Mn content of bone by 23%, Cu by 9% and Zn by 6%. These differences showed a mean fourfold greater content of these minerals in supplemental diet, whereas femora did not reflect a 5.4 times greater content of major minerals (Na and P) in the diet. Lower content of B and Sr in supplemented diet also reduced femur B by 14% and Sr by 5%. There was a subtle effect of diet only on E and none on other mechanical properties. Thus, greater availability of microminerals but not major minerals in the diet is reflected in bone composition even before marked body effects, bone macro-structure or its mechanical properties are affected.