B. M. C. Gorissen

Trabecular bone of precocials at birth; are they prepared to run for the wolf(f)?

Bone is a dynamic tissue adapting to loading according to “Wolffs law of bone adaptation.” During very early life, however, such a mechanism may not be adequate enough to adapt to the dramatic change in environmental challenges in precocial species. Their neonates are required to stand and walk within hours after birth, in contrast to altricial animals that have much more time to adapt from the intrauterine environment to the outside world. In this study, trabecular bone parameters of the talus and sagittal ridge of the tibia from stillborn but full‐term precocials (calves and foals) were analyzed by micro‐CT imaging in order to identify possible anticipatory mechanisms to loading. Calculated average bone volume fraction in the Shetland pony (49–74%) was significantly higher compared to Warmblood foals (28–51%). Bovine trabecular bone was characterized by a low average bone volume fraction (22–28%), however, more directional anisotropy was found. It is concluded that anticipatory strategies in skeletal development exist in precocial species, which differ per species and are most likely related to anatomical differences in joint geometry and related loading patterns. The underlying regulatory mechanisms are still unknown, but they may be based on a genetic blueprint for the development of bone. More knowledge, both about a possible blueprint and its regulation, will be helpful in understanding developmental bone and joint diseases. J. Morphol. 277:948–956, 2016.

The development of locomotor kinetics in the foal and the effect of osteochondrosis

Summary Reason for performing study Foals stand and walk immediately after birth, but insight into the subsequent longitudinal development of their gait kinetics in the early juvenile phase and the possible influence of osteochondrosis thereon is lacking. Objectives To quantify gait kinetics in foals during the first half year of life, taking into account their osteochondrosis status. Study design Prospective, cohort study performed at a single stud farm. Methods Pressure plate measurements at walk and trot from 11 Dutch Warmblood foals during the first 24 weeks of life were used to determine body mass normalised peak vertical force, normalised vertical impulse and stance duration. Coefficients of variation of peak vertical force and stance duration were used as measures for gait maturity. Radiographs of tarsocrural and femoropatellar joints were taken at age 4–6 weeks and after 6 months to check for osteochondrosis. A linear mixed model was used to determine the effects of age, limb, presence of osteochondrosis and speed on gait parameters. Results Mean walking and trotting velocity increased over time as did stance duration and normalised vertical impulse, normalised peak vertical force values however remained relatively constant. During the first weeks of their life only the coefficient of variation of stance duration decreased significantly, while the coefficient of variation of peak vertical force did not. None of the foals was visibly lame, but the presence of osteochondrosis resulted in a temporarily but significantly reduced normalised peak vertical force. Main limitations This study is a relatively small sample size of one breed from a single stud farm. A stand‐alone pressure plate was used and body mass was estimated rather than measured. Conclusions Despite being precocious, foals need time to mature their gait. During growth, velocity at walk and trot increases, but normalised peak vertical force remains relatively constant. Although not visibly lame, a temporary reduction in normalised peak vertical force was detected in osteochondrosis positive foals using a pressure plate.

A rare anatomical variation: a case of a common celiacomesenteric trunk in a cat.

In this study, we present a cat with a common 1‐cm‐long celiacomesenteric trunk. The arteria hepatica branched off first from the separate arteria celiaca and gave rise to the arteria gastrica dextra and arteria gastroduodenalis. The main stem of the arteria celiaca then split into the arteria gastrica sinistra and the arteria lienalis. The arteria mesenterica cranialis extended ventrocaudally in the mesentery. This variation is due to developmental changes in the ventral splanchnic arteries, and they are quite varied. The basic architecture and perfused organs are comparable, which indicates that the presence of a common celiacomesenteric trunk is more related to individual development than to phylogeny or function.

The development of hoof balance and landing preference in the post-natal period

Summary Background Foals can follow the herd within hours of birth, but it has been shown that kinetic gait parameters and static balance still have to mature. However, development of dynamic balance has not been investigated. Objectives To objectively quantify landing and pressure pattern dynamics under the hoof during the first half year of life. Study design Prospective, cohort study performed at a single stud farm. Methods Pressure plate measurements at walk and trot from ten Dutch warmblood foals during the first 24 weeks of life were used to quantify toe‐heel and medial‐lateral hoof balance asymmetry indexes and to determine preferred landing strategy. Concurrently, radiographs of the tarsocrural and femoropatellar joints were taken at 4–6 weeks and after 6 months to check for osteochondrosis. A linear mixed model was used to determine the effects of time point, limb pair (front/hind), side (left/right) and osteochondrosis status of every foal. Results At 25% of stance duration at walk, front limbs were more loaded in the heel region in weeks 6–20 (P≤0.04), the medial‐lateral balance was more to the lateral side from week 6 onwards at both walk and trot (P≤0.04). Landing preference gradually changed in the same directions. Variability in pressure distribution decreased over time. (Subclinical) osteochondrosis did not influence any of the measured parameters. Main limitations This study is limited by the relatively small sample size only containing one breed from a single stud farm. Conclusions Dynamic hoof balance in new‐born foals is more variable and less oriented towards the lateral side of the hoof and to the heel than in mature horses. This pattern changes gradually during the first weeks of life. Knowledge of this process is essential for the clinician when considering interventions in this area in early life.

Trabecular and subchondral bone development of the talus and distal tibia from foal to adult in the warmblood horse

Horses are precocial animals and able to stand and walk within hours after birth. To cope with associated loading, intrauterine bone development has shown to be anticipative. This study provides further insight into the post‐natal development of structurally important features of trabecular and subchondral bone of the talus and sagittal ridge of the tibia of warm‐blooded horses. In all areas studied, the average bone volume fraction showed a gradual increase over time, which was the result of a significant increase in trabecular thickness, without significant changes in the degree of anisotropy. Similar to the mineralised part of the bone, collagen content, measured as average retardation using polarised light microscopy, increased significantly, but the degree of anisotropy of the collagen type I network did not. At birth, the subchondral bone layer had a more trabecular aspect, gradually changing to an even surface with only a few vascular canals at an age of 2 months. Presented results indicate the necessity for a stronger structure, but not for a different structural design after birth, providing further evidence for anticipatory bone development in the horse. More knowledge about the strategies used to cope with mechanical loading after birth might be helpful in understanding the developmental bone and joint diseases.

Hypoxia negatively affects senescence in osteoclasts and delays osteoclastogenesis

Cellular senescence, that is, the withdrawal from the cell cycle, combined with the acquirement of the senescence associated secretory phenotype has important roles during health and disease and is essential for tissue remodeling during embryonic development. Osteoclasts are multinucleated cells, responsible for bone resorption, and cell cycle arrest during osteoclastogenesis is well recognized. Therefore, the aim of this study was to investigate whether these cells should be considered senescent and to assess the influence of hypoxia on their potential senescence status. Osteoclastogenesis and bone resorption capacity of osteoclasts, cultured from CD14+ monocytes, were evaluated in two oxygen concentrations, normoxia (21% O2) and hypoxia (5% O2). Osteoclasts were profiled by using specific staining for proliferation and senescence markers, qPCR of a number of osteoclast and senescence‐related genes and a bone resorption assay. Results show that during in vitro osteoclastogenesis, osteoclasts heterogeneously obtain a senescent phenotype. Furthermore, osteoclastogenesis was delayed at hypoxic compared to normoxic conditions, without negatively affecting the bone resorption capacity. It is concluded that osteoclasts can be considered senescent, although senescence is not uniformly present in the osteoclast population. Hypoxia negatively affects the expression of some senescence markers. Based on the direct relationship between senescence and osteoclastogenesis, it is tempting to hypothesize that contents of the so‐called senescence associated secretory phenotype (SASP) not only play a functional role in matrix resorption, but also may regulate osteoclastogenesis.

Effects of long-term use of the preferential COX-2 inhibitor meloxicam on growing pigs

Meloxicam, a preferential COX-2 inhibitor, is a commonly used NSAID in pigs. Besides having potential side effects on the gastrointestinal tract, this type of drug might potentially affect osteogenesis and chondrogenesis, processes relevant to growing pigs. Therefore, the effects of long-term meloxicam treatment on growing pigs were studied. Twelve piglets (n=6 receiving daily meloxicam 0.4 mg/kg orally from 48 until 110 days of age; n=6 receiving only applesauce (vehicle control)) were subjected to visual and objective gait analysis by pressure plate measurements at several time points. Following euthanasia a complete postmortem examination was performed and samples of the talus and distal tibia, including the distal physis, were collected. Trabecular bone microarchitecture was analysed by microCT scanning, bone stiffness by compression testing and growth plate morphology using light microscopy. Animals were not lame and gait patterns did not differ between the groups. Pathological examination revealed no lesions compatible with known side effects of NSAIDs. Trabecular bone microarchitecture and growth plate morphology did not differ between the two groups. The findings of this in vivo study reduce concerns regarding the long-term use of meloxicam in young, growing piglets.