Tibial dyschondroplasia is closely related to suppression of expression of hypoxia-inducible factors 1α, 2α, and 3α in chickens

Thiram exposure induces tibial dyschondroplasia in broilers via the regulation effect of circ_003084/miR-130c-5p/BMPR1A crosstalk on chondrocyte proliferation and differentiation

Thiram, an agricultural insecticide, has been demonstrated to induce tibial dyschondroplasia (TD) in avian species. Circular RNA (circRNAs), a novel class of functional biological macromolecules characterized by their distinct circular structure, play crucial roles in various biological processes and diseases. Nevertheless, the precise regulatory mechanism underlying non-coding RNA involvement in thiram-induced broiler tibial chondrodysplasia remains elusive. In this study, we established a broiler model of thiram exposure for 10 days to assess TD and obtain a ceRNA network by RNA sequencing. By analyzing the differentially expressed circRNAs network, we id entify that circ_003084 was significantly upregulated in TD cartilage. Elevated circ_003084 inhibited TD chondrocytes proliferation and differentiation in vitro but promote apoptosis. Mechanistically, circ_003084 competitively binds to miR-130c-5p and prevents miR-130c-5p to decrease the level of BMPR1A, which upregulates the expression of apoptosis genes Caspase 3, Caspase 9, Bax and Bcl2, and finally facilitates cell apoptosis. Taken together, these findings imply that circ_003084/miR-130c-5p/BMPR1A interaction regulated TD chicken chondrocyte proliferation, apoptosis, and differentiation. This is the first work to reveal the mechanism of regulation of circRNA-related ceRNA on thiram-induced TD, offering a key reference for environmental toxicology.

Effect of BMP6 on the proliferation and apoptosis of chicken chondrocytes induced by thiram

The development of skeleton system is a complex biological process and be regulated by many transcription factors. Previous studies have shown that BMP6 is involved in skeleton development and other cells transforming to chondrocytes, but it is still not known whether do something to tibial dyschondroplasia (TD) broilers chondrocytes. In this study, RT-PCR revealed that the expression level of BMP6 in TD broiler chondrocytes at 7 days age was significantly decreased compared with normal group (P < 0.05). CCK-8 and EdU assay showed that the proliferation of cells transfected with interference BMP6 was significantly decreased compared with control siRNA, while cell proliferation was significantly increased after overexpression of BMP6. Meanwhile, the proportion of G0/G1 phase cells was significantly increased and the proportion of G2/M phase cells was significantly decreased after interference of BMP6 for 48 h in TD chicken chondrocytes (P < 0.05). In addition, flow cytometry analysis exhibited that interference BMP6 significantly increased apoptosis rate and necrotizing rate of cells. In conclusion, these results suggest that BMP6 plays a positive role in the growth and development of TD broiler chondrocytes. Our findings reveal a new target for TD prevention in broiler chickens.

Cellular, molecular and genetical overview of avian tibial dyschondroplasia

Tibial dyschondroplasia (TD) is an intractable avian bone disease that causes severe poultry economic losses. The pathogenicity of TD is unknown. Therefore, TD disease has not been evacuated yet. Based on continuous research findings, we have gone through the molecular and cellular insight into the TD and proposed possible pathogenicity for future studies. Immunity and angiogenesis-related genes expressed in the erythrocytes of chicken, influenced the apoptosis of chicken chondrocytes to cause TD. TD could be defined as the irregular, unmineralized and un-vascularized mass of cartilage, which is caused by apoptosis, degeneration and insufficient blood supply at the site of the chicken growth plate. The failure of angiogenesis attributed improper nutrients supply to the chondrocytes; ultimately, bone development stopped, poor calcification of cartilage matrix, and apoptosis of chondrocytes occurred. Recent studies explore potential signaling pathways that regulated TD in broiler chickens, including parathyroid hormone-related peptide (PTHrP), transforming growth factor β (TGF- β)/bone morphogenic proteins (BMPs), and hypoxia-inducible factor (HIF). Several studies have reported many medicines to treat TD. However, recently, rGSTA3 protein (50 μg·kg^-1) is considered the most proper TD treatment. The present review has summarized the molecular and cellular insight into the TD, which will help researchers in medicine development to evacuate TD completely.

Cartilage Homeostasis Affects Femoral Head Necrosis Induced by Methylprednisolone in Broilers

(1) Background: Since the large-scale poultry industry has been established, femoral head necrosis (FHN) has always been a major leg disease in fast-growing broilers worldwide. Previous research suggested that cartilage homeostasis could be taken into consideration in the cause of FHN, but the evidence is insufficient. (2) Methods: One-day-old broiler chickens were randomly divided into three groups, 16 broilers per group. The birds in group L were injected intramuscularly with methylprednisolone (MP) twice a week for four weeks (12.5 mg·kg⁻¹). The birds in group H were injected intramuscularly with MP (20 mg·kg⁻¹·d⁻¹) for 7 d (impulse treatment). The birds in group C were treated with sterile saline as a control group. Broilers were sacrificed at 42 and 56 d. Blood samples were collected from the jugular vein for ELISA and biochemical analysis. Bone samples, including femur, tibia, and humerus, were collected for histopathological analysis, bone parameters detection, and real-time quantitative PCR detection. (3) Results: The FHN broilers in group L and H both showed lower body weight (BW) and reduced bone parameters. In addition, the MP treatment resulted in reduced extracellular matrix (ECM) anabolism and enhanced ECM catabolism. Meanwhile, the autophagy and apoptosis of chondrocytes were enhanced, which led to the destruction of cartilage homeostasis. Moreover, the impulse MP injection increased the portion of birds with severer FHN, whereas the MP injection over a long period caused a more evident change in serum cytokine concentrations and bone metabolism indicators. (4) Conclusions: The imbalance of cartilage homeostasis may play a critical role in the development of FHN in broilers. FHN broilers induced by MP showed a more pronounced production of catabolic factors and suppressed the anabolic factors, which might activate the genes of the WNT signal pathway and hypoxia-inducible factors (HIFs), and then upregulate the transcription expression of ECM to restore homeostasis.

Role of Angiopoietin-like 4 on Bone Vascularization in Chickens Exposed to High-altitude Hypoxia

The aim of this study was to investigate the role and expression of a novel angiogenic factor (angiopoietin-like 4, ANGPTL4) in tibial growth plates of broiler chickens exposed to high-altitude hypoxia. One-day-old healthy broiler chickens (n = 120) were transported from lowland to a high-altitude hypoxic region (nearly 3,000 m above sea level) and were reared under hypoxic- (natural lower oxygen content) and normoxic conditions (nearly 21% oxygen content) for 14 days. The effect of hypoxia on angiogenesis in the tibial growth plates and hypoxia-inducible factor (HIF)-1α and ANGPTL4 expressions were determined by histological examination, quantitative reverse transcriptase polymerase chain reaction (qRT-PCR), western blot and enzyme-linked immunosorbent assay (ELISA) techniques. The increase in vascular distribution to the hypertrophic chondrocyte zone of tibial growth plates contributed to promoting growth and development of the tibia under hypoxic conditions, which was highly correlated with the upregulation of ANGPTL4 at both the mRNA and protein levels together with activation of HIF-1α under hypoxic conditions. These findings demonstrate that angiogenic factor ANGPTL4 upregulation is involved in tibial growth plate angiogenesis to promote the development of the tibia in broiler chickens under hypoxic conditions. They also suggest that ANGPTL4 may serve as a new molecular therapeutic target for ameliorating tibial dyschondroplasia chicken bone vascularization.