Age-dependent expression of osteochondrosis-related genes in equine leukocytes

Differential Expression of IGF1, IGFBP5, MSTN, and MYH1 Across Different Age Classes in American Quarter Horses

The objective of this study was to determine the influence of age on expression of insulin-like growth factor 1 (IGF1), insulin-like growth factor binding protein (IGFBP5), myostatin (MSTN), and myosin (MYH1) genes which are related to growth and muscle development in the American Quarter Horse. Thus, horses (n = 10) from weanling, yearling, 2-, 3-, and 10-year-old age classes were sampled and gene expression was assessed by RT-qPCR. ΔC_T was calculated using the hypoxanthine-guanine phosphoribosyltransferase gene as an internal normalizer. The generalized linear model was used to determine differentially expressed genes, by pairwise comparison between ages. Among technical replicates, the coefficient of variation ranged from 1.0 to 5.2% and was lower than the variation observed between biological replicates (2.1-12.9%). IGF1 demonstrated significantly lower expression in the 3-year-old age class than in weanlings and yearlings, but the 10-year-old age class displayed a significantly higher level than 2- and 3-year-old age classes. Expression of IGFBP5 was highest in weanlings compared with all other age classes. Expression of MSTN was significantly higher in weanlings than in other age classes, whereas 10-year-old horses had an intermediate level of expression, but significantly different from yearlings, 2- and 3-year-old fillies. Finally, expression of MYH1 was lower in 2- and 10-year-old horses than in weanlings and yearlings, whereas 3-year-old fillies demonstrated an intermediate level of expression. Differential expression patterns observed in this preliminary study provide insight into the physiological changes occurring throughout the life span of horses. These patterns could also help explain the variation in performance and endurance between individuals at different developmental stages.

Is Sclerostin Glycoprotein a Suitable Biomarker for Equine Osteochondrosis?

Osteochondrosis (OC) disease appears to be multifactorial in origin, including skeletal growth rates, nutrition, endocrinological factors, exercise, biomechanics, and other environmental factors. Endocrinological and metabolic factors seem to have an important role in the pathogeny of OC like the Wnt signaling pathway. One of the regulators in the Wnt signaling pathway is the sclerostin glycoprotein. The aim of this study was to investigate the sclerostin blood concentration according to the evolution of the disease, the environment, and the age but also its use as a possible biomarker for OC disease. Relation between age and sclerostin concentrations was calculated by a linear regression. A relation was found between age and sclerostin concentrations, but also a significant relation between age and the sclerostin concentrations was observed for two subgroups (OC affected and healthy). Evolution of the disease related to the sclerostin concentration was assessed with two logistic regressions (risk of developing OC and recovery of existing lesions), but not any significance was found. In conclusion, these results show that, despite the possible link of sclerostin with the OC pathogenesis through the Wnt pathway, circulating levels of this glycoprotein shall not be used as a biomarker for the disease. Besides, more studies are needed to fully understand the functions of sclerostin in the equine specie since it may play an important role in bone homeostasis.

Impact of feeding and housing on the development of osteochondrosis in foals-A longitudinal study

Osteochondrosis dissecans (OCD) is a developmental orthopedic disease caused by a failure of the endochondral ossification in epiphyseal plates and joint cartilage. This trouble may induce the presence of osteochondral fragments in the articulation, fissures or subchondral bone cysts in the growth cartilage. Occurrence of osteochondrosis is influenced by a complex interaction of different factors. Among these, the effect of the housing and the feeding of the foals during their first months of life, have been described as risk factors for the development of osteochondrosis. The aim of this study was to investigate the evolution of OCD lesions with a longitudinal study in 204 young foals from 6 to 18 months in comparison to the type of feeding and the type of housing conditions. These factors and OCD status were obtained by a questionnaire and radiological examination, respectively. This allowed dividing the foals into four groups according to the initial OCD status and the evolution of the condition. As a result, we found that foals fed with concentrates show a higher probability to develop OCD lesions (p=0.06), while foals not receiving concentrates, had a higher probability to heal from existing OCD lesions (p=0.001). This study supports the theory that management factors such as feeding or housing may influence the evolution of the osteochondrosis disease.