The differentiation of prehypertrophic into hypertrophic chondrocytes drives an OA-remodeling program and IL-34 expression.

OBJECTIVES: We hypothesize that chondrocytes from the deepest articular cartilage layer are pivotal in maintaining cartilage integrity and that the modification of their prehypertrophic phenotype to a hypertrophic phenotype will drive cartilage degradation in osteoarthritis. DESIGN: Murine immature articular chondrocytes (iMACs) were successively cultured into three different culture media to induce a progressive hypertrophic differentiation. Chondrocyte were phenotypically characterized by whole-genome microarray analysis. The expression of IL-34 and its receptors PTPRZ1 and CSF1R in chondrocytes and in human osteoarthritis tissues was assessed by RT-qPCR, ELISA and immunohistochemistry. The expression of bone remodeling and angiogenesis factors and the cell response to IL-1ß and IL-34 were investigated by RT-qPCR and ELISA. RESULTS: Whole-genome microarray analysis showed that iMACs, prehypertrophic and hypertrophic chondrocytes each displayed a specific phenotype. IL-1ß induced a stronger catabolic effect in prehypertrophic chondrocytes than in iMACs. Hypertrophic differentiation of prehypertrophic chondrocytes increased Bmp-2 (95%CI [0.78; 1.98]), Bmp-4 (95%CI [0.89; 1.59]), Cxcl12 (95%CI [2.19; 5.41]), CCL2 (95%CI [3.59; 11.86]), Mmp 3 (95%CI [10.29; 32.14]) and Vegf mRNA expression (95%CI [0.20; 1.74]). Microarray analysis identified IL-34, PTPRZ1 and CSFR1 as being strongly overexpressed in hypertrophic chondrocytes. IL-34 was released by human osteoarthritis cartilage; its receptors were expressed in human osteoarthritis tissues. IL-34 stimulated CCL2 and MMP13 in osteoblasts and hypertrophic chondrocytes but not in iMACs or prehypertrophic chondrocytes. CONCLUSION: Our results identify prehypertrophic chondrocytes as being potentially pivotal in the control of cartilage and subchondral bone integrity. Their differentiation into hypertrophic chondrocytes initiates a remodeling program in which IL-34 may be involved.

Energy and lipid metabolism gene expression of D18 embryos in dairy cows is related to dam physiological status.

We analyzed the change in gene expression related to dam physiological status in day (D)18 embryos from growing heifers (GH), early lactating cows (ELC), and late lactating cows (LLC). Dam energy metabolism was characterized by measurement of circulating concentrations of insulin, glucose, IGF-1, nonesterified fatty acids, ß-hydroxybutyrate, and urea before embryo flush. The metabolic parameters were related to differential gene expression in the extraembryonic tissues by correlation analysis. Embryo development estimated by measuring the length of the conceptuses and the proportion of expected D18 gastrulating stages was not different between the three groups of females. However, embryo metabolism was greatly affected by dam physiological status when we compared GH with ELC and GH with LLC but to a lesser extent when ELC was compared with LLC. Genes involved in glucose, pyruvate, and acetate utilization were upregulated in GH vs. ELC conceptuses (e.g., SLC2A1, PC, ACSS2, ACSS3). This was also true for the pentose pathway ( PGD, TKT), which is involved in synthesis of ribose precursors of RNA and DNA. The pathways involved in lipid synthesis were also upregulated in GH vs. ELC. Despite similar morphological development, the molecular characteristics of the heifers' embryos were consistently different from those of the cows. Most of these differences were strongly related to metabolic/hormone patterns before insemination and during conceptus free-life. Many biosynthetic pathways appeared to be more active in heifer embryos than in cow embryos, and consequently they seemed to be healthier, and this may be more conducive to continue development.

Genetic tools to improve reproduction traits in dairy cattle.

Fertility is a major concern in the dairy cattle industry and has been the subject of numerous studies over the past 20 years. Surprisingly, most of these studies focused on rough female phenotypes and, despite their important role in reproductive success, male- and embryo-related traits have been poorly investigated. In recent years, the rapid and important evolution of technologies in genetic research has led to the development of genomic selection. The generalisation of this method in combination with the achievements of the AI industry have led to the constitution of large databases of genotyping and sequencing data, as well as refined phenotypes and pedigree records. These resources offer unprecedented opportunities in terms of fundamental and applied research. Here we present five such examples with a focus on reproduction-related traits: (1) detection of quantitative trait loci (QTL) for male fertility and semen quality traits; (2) detection of QTL for refined phenotypes associated with female fertility; (3) identification of recessive embryonic lethal mutations by depletion of homozygous haplotypes; (4) identification of recessive embryonic lethal mutations by mining whole-genome sequencing data; and (5) the contribution of high-density single nucleotide polymorphism chips, whole-genome sequencing and imputation to increasing the power of QTL detection methods and to the identification of causal variants.

Gene selection heuristic algorithm for nutrigenomics studies.

Large datasets from -omics studies need to be deeply investigated. The aim of this paper is to provide a new method (LEM method) for the search of transcriptome and metabolome connections. The heuristic algorithm here described extends the classical canonical correlation analysis (CCA) to a high number of variables (without regularization) and combines well-conditioning and fast-computing in "R." Reduced CCA models are summarized in PageRank matrices, the product of which gives a stochastic matrix that resumes the self-avoiding walk covered by the algorithm. Then, a homogeneous Markov process applied to this stochastic matrix converges the probabilities of interconnection between genes, providing a selection of disjointed subsets of genes. This is an alternative to regularized generalized CCA for the determination of blocks within the structure matrix. Each gene subset is thus linked to the whole metabolic or clinical dataset that represents the biological phenotype of interest. Moreover, this selection process reaches the aim of biologists who often need small sets of genes for further validation or extended phenotyping. The algorithm is shown to work efficiently on three published datasets, resulting in meaningfully broadened gene networks.

Pre- and post-partum mild underfeeding influences gene expression in the reproductive tract of cyclic dairy cows.

Undernutrition before and after calving has a detrimental effect on the fertility of dairy cows. The effect of nutritional stress was previously reported to influence gene expression in key tissues for metabolic health and reproduction such as the liver and the genital tract early after calving, but not at breeding, that is, between 70 and 90 days post-partum. This study investigated the effects of pre- and post-partum mild underfeeding on global gene expression in the oviduct, endometrium and corpus luteum of eight multiparous Holstein cows during the early and middle phases of an induced cycle 80 days post-partum. Four control cows received 100% of energy and protein requirements during the dry period and after calving, while four underfed received 80% of control diet. Oestrous synchronization treatment was used to induce ovulation on D80 post-partum. Oviducts, ovaries and the anterior part of each uterine horn were recovered surgically 4, 8, 12 and 15 days after ovulation. Corpora lutea were dissected from the ovaries, and the endometrium was separated from the stroma and myometrium in each uterine horn. The oviduct segments were comprised of ampulla and isthmus. RNAs from ipsi- and contralateral samples were pooled on an equal weight basis. In each tissue, gene expression was assessed on a custom bovine 10K array. No differentially expressed gene (DEG) in the corpus luteum was identified between underfed and control, conversely to 293 DEGs in the oviduct vs 1 in the endometrium under a false discovery rate (FDR) < 0.10 and 1370 DEGs vs 3, respectively, under FDR < 0.15. Additionally, we used dedicated statistics (regularized canonical correlation analysis) to correlate the post-partum patterns of six plasma metabolites and hormones related to energy metabolism measured weekly between calving and D80 with gene expression. High correlations were observed between post-partum patterns of IGF-1, insulin, ß-hydroxybutyrate and the expression in the oviduct of genes related to reproductive system disease, connective tissue disorders and metabolic disease. Moreover, we found special interest in the literature to retinoic acid-related genes (e.g. FABP5/CRABP2) that might indicate abnormalities in post-partum tissue repair mechanisms. In conclusion, this experiment highlights relationships between underfeeding and gene expression in the oviduct and endometrium after ovulation in cyclic Holstein cows. This might help to explain the effect of mild undernutrition on fertilization failure and early embryonic mortality in post-partum dairy cows.

Effects of eccentric training on torque-angular velocity-power characteristics of elbow flexor muscles in older women.

The purpose of this study was to investigate the potential of eccentric training to improve elbow flexor muscle power in elderly subjects. Fourteen older female volunteers (age range 60-78 years) were randomly assigned into either a training group (TG) or a control group (CG). For the TG, the 21-session 7-week eccentric training program consisted of 5x6 eccentric muscle actions at 60-100% of concentric three maximal repetitions. Before and after training, maximal elbow flexions were performed against increasing inertia. Maximal isokinetic elbow flexions at four angular velocities (eccentric actions, -60 degrees s(-1), -30 degrees rads(-1); concentric actions, 30, 60 degrees s(-1)) and maximal isometric actions were also performed. Maximal power (Pmax) and an index of maximal shortening velocity (VImax)were determined. For all action conditions, the myoelectric activities of the biceps and the triceps brachii muscles were recorded and quantified as a root mean square (RMS) value. In the TG, maximal torque developed under isometric, isokinetic and inertial conditions increased significantly after training (ranging from 11 to 19%). Pmax and VImax also increased significantly (31.3 and 25.9%, respectively). These parameters remained unchanged in the CG. The RMS activity of the biceps and triceps muscles was not affected by eccentric training for all action conditions excepting the eccentric condition at -30 degrees s(-1) where the RMS activity of the biceps increased significantly. The gains in maximal torque, Pmax and VImax observed after training would result more from intramuscular modifications than from changes in muscular activity, except for eccentric condition at -30 degrees s(-1) where the torque gains could also be partly explained by a reduction in inhibition of the motor unit pool.

The influence of ageing on the force-velocity-power characteristics of human elbow flexor muscles.

The purpose of this study was to quantify the effects of ageing on the maximal power (P(max)) of the elbow flexor muscles and to determine the impact of velocity on the loss of power in older people. Sixteen elderly subjects (7 men and 9 women, age range 61-78 years) and 17 young subjects (11 men and 6 women, age range 18-27 years) participated in this study. Maximal elbow flexions were performed against increasing inertia. The maximal force (F(max)), maximal shortening velocity (V(max)), P(max), dynamic constants (a, b and a/F(max)), optimal force (F(opt)), optimal velocity (V(opt)) and V(opt)/V(max) were determined from Hill's equation. Myoelectrical activity (EMG) of the biceps and triceps muscles was quantified as an root mean square (RMS) value. F(max), V(max), P(max), F(opt), and V(opt) were significantly lower in elderly than in young subjects (28, 31, 45, 24 and 28% lower, respectively; p<0.05), whereas a/F(max) and V(opt)/V(max) were not different between the two age groups. In women, the greater decrease in P(max) appears to be more dependent on V(opt) than F(opt). In addition, V(max) decreased with age in women but not in men. The absence of significant differences between age groups in normalised RMS values indicates that P(max) and V(max) loss with increasing age could result more from changes in the properties of contractile element than from changes in muscular activity.

Compliance changes of the series elastic component of elbow flexor muscles with age in humans.

The purpose of this study was to determine the compliance of the series elastic component (SEC) of the elbow flexor muscles in young (n=13, mean age 21.5+/-2.5 years) and elderly (n=15, mean age 67.4+/-4.7 years) subjects. SEC compliance was determined using a quick-release method. Under isometric conditions, myoelectrical activity (EMG) of biceps and triceps muscles was quantified by the root mean square (RMS) value. The compliance index (CI) was defined as the slope of the regression of ln(NC) on ln(NF), where NC and NF are normalised compliance and force respectively. Maximal isometric force and neuromuscular efficiency (torque/RMS) were significantly greater in the young than in the elderly. Antagonist (triceps) co-activation was similar for both groups. The CI after quick-release movements was significantly greater in the young than in the elderly. These results suggest that the SEC compliance of the elbow flexors muscles decreases with age. This decrease in global compliance could be induced by changes both in the active and passive portions of the SEC. These findings may be of functional significance for everyday muscular activity in older people.