Hsp90 and angiogenesis in bone disorders—lessons from the avian growth plate

Baicalin inhibits apoptosis and enhances chondrocyte proliferation in thiram-induced tibial dyschondroplasia in chickens by regulating Bcl-2/Caspase-9 and Sox-9/Collagen-II expressions

Avian tibial dyschondroplasia (TD) is a skeletal disease affecting fast growing chickens, resulting in non-mineralized avascular cartilage. This metabolic disorder is characterized by lameness and reduced growth performance causing economic losses. The aim of this study was to investigate the protective effects of baicalin against TD caused by thiram exposure. A total of two hundred and forty (n = 240) one day-old broiler chickens were uniformly and randomly allocated into three different groups (n = 80) viz. control, TD, and baicalin groups. All chickens received standard feed, however, to induce TD, the TD and baicalin groups received thiram (tetramethylthiuram disulfide) at a rate of 50 mg/kg feed from days 4-7. The thiram induction in TD and baicalin groups resulted in lameness, high mortality, and enlarged growth-plate, poor production performance, reduction in ALP, GSH-Px, SOD, and T-AOC levels, and increased AST and ALT, and MDA levels. Furthermore, histopathological results showed less vascularization, and mRNA and protein expression levels of Sox-9, Col-II, and Bcl-2 showed significant downward trend, while caspase-9 displayed significant up-regulation in TD-affected chickens. After the TD induction, the baicalin group was orally administered with baicalin at a rate of 200 mg/kg from days 8-18. Baicalin administration increased the vascularization, and chondrocytes with intact nuclei, alleviated lameness, decreased GP size, increased productive capacity, and restored the liver antioxidant enzymes and serum biochemical levels. Furthermore, baicalin significantly up-regulated the gene and protein expressions of Sox-9, Col-II, and Bcl-2, and significantly down-regulated the expression of caspase-9 (p < 0.05). Therefore, the obtained results suggest that baicalin could be a possible choice in thiram toxicity alleviation by regulating apoptosis and chondrocyte proliferation in thiram-induced tibial dyschondroplasia.

Residue of thiram in food, suppresses immune system stress signals and disturbs sphingolipid metabolism in chickens

Thiram, a well-known sulfur containing organic compound is frequently and extensively used in agriculture because of high biological activity to control different pests. In certain cases, due to long persistence in the environment pesticides and other environmental contaminants induce undesirable toxic impacts to public health and environment. To ascertain the potential mechanisms of toxicity of thiram on different immune organs of broilers, a total of 100 one-day-old chicks were obtained and randomly divided into two groups including thiram group (50 mg/kg) and untreated control group. Thymus and spleen tissues were collected at the age of 14 days from the experimental birds. At necropsy level, thymus was congested, enlarged and hyperemic while spleen had no obvious lesions. The results on mechanisms (apoptosis and autophagy) of immunotoxicity showed significantly increased expression of bax, caspase3, cytc, ATG5, beclin1 and p62 in spleen of treated mice. Results indicated significantly decreased expression of m-TOR and bcl2 to activate apoptosis and autophagy. The expressions of bax, p53 and m-TOR were up-regulated in the thymus while the expressions of ATG5 and Beclin1 were down-regulated to mediate cell apoptosis and inhibit autophagy. The results on different metabolome investigation showed that the sphingolipid metabolism in the thymus of chicks exposed to thiram was disrupted resulting in up-regulation of metabolites related to cell membrane components such as SM, galactosylceramide and lactosylceramide. The results of our experimental research suggest that thiram can interfere with the sphingolipid metabolism in thymus and angiogenesis, inhibit the proliferation of vascular endothelial cells to induce potential toxic effects in chicken.

RACK1 mediates the advanced glycation end product-induced degradation of HIF-1α in nucleus pulposus cells via competing with HSP90 for HIF-1α binding

Hyperglycemia can drive advanced glycation end product (AGE) accumulation and associated nucleus pulposus cell (NPC) dysfunction, but the basis for this activity has not been elucidated. Hypoxia-inducible factor-1α (HIF-1α) is subject to cell-type-specific AGE-mediated regulation. In the current study, we assessed the mechanistic relationship between AGE accumulation and HIF-1α degradation in NPCs. Immunohistochemical staining of degenerated nucleus pulposus (NP) samples was used to assess AGE levels. AGE impact on NPC survival and glycolysis-related gene expression was assessed via 3-(4,5)-dimethylthiazol(-z-y1)-3,5-di-phenyltetrazolium bromide assay and quantitative reverse-transcription polymerase chain reaction (qRT-PCR), while HIF-1α expression in NPCs following AGE treatment was monitored via Western blot analysis and qRT-PCR. Additionally, a luciferase reporter assay was used to monitor HIF-1α transcriptional activity. The importance of the receptor for activated C-kinase 1 (RACK1) as a mediator of HIF-1α degradation was evaluated through gain- and loss-of-function experiments. Competitive binding of RACK1 and HSP90 to HIF-1α was evaluated via immunoprecipitation. Increased AGE accumulation was evident in NP samples from diabetic patients, and AGE treatment resulted in reduced HIF-1α protein levels in NPCs that coincided with reduced HIF-1α transcriptional activity. AGE treatment impaired the stability of HIF-1α, leading to its RACK1-mediated proteasomal degradation in a manner independent of the canonical PHD-mediated degradation pathway. Additionally, RACK1 competed with HSP90 for HIF-1α binding following AGE treatment. AGE treatment of NPCs leads to HIF-1α protein degradation. RACK1 competes with HSP90 for HIF-1α binding following AGE treatment, resulting in posttranslational HIF-1α degradation. These results suggest that AGE is an intervertebral disc degeneration risk factor, and highlight potential avenues for the treatment or prevention of this disease.

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.

The role of blood vessels in broiler chickens with tibial dyschondroplasia

Tibial dyschondroplasia (TD) is an intractable tibiotarsal bone disorder of rapid growing avian species, which leads to huge economic losses and compromised poultry welfare. However, the exact pathogenesis and treatment of TD remain largely unknown. Based on continuous research findings, we propose the TD pathogenesis hypothesis: during skeletal development of TD chickens, due to the absence of vasculature of proximal tibial growth plates (TGP), hypertrophic chondrocytes of the TGP are unable to complete calcification in normal bone development and less dead chondrocytes in the corresponding area can be timely transported through the blood vessels. Moreover, recent studies demonstrate that the TD formation mechanism gradually tends to a large number of dead chondrocytes in the TGP region or apoptosis occur due to various factors (such as, reduction of vascular invasion and blood cells, and increased weight or mechanical force of the tibia), while the reduction of blood vessels is insufficient to remove these chondrocytes and eventually leads to the TD formation. Recognizing the possible role of the blood vessels in the incidence of TD and can propose that the improvement in vasculature might be a novel therapeutic approach for ending TD in chickens.

Proteome Alterations in Equine Osteochondrotic Chondrocytes

Osteochondrosis is a failure of the endochondral ossification that affects developing joints in humans and several animal species. It is a localized idiopathic joint disorder characterized by focal chondronecrosis and growing cartilage retention, which can lead to the formation of fissures, subchondral bone cysts, or intra-articular fragments. Osteochondrosis is a complex multifactorial disease associated with extracellular matrix alterations and failure in chondrocyte differentiation, mainly due to genetic, biochemical, and nutritional factors, as well as traumas. This study describes the main proteomic alterations occurring in chondrocytes isolated from osteochondrotic cartilage fragments. A comparative analysis performed on equine osteochondrotic and healthy chondrocytes showed 26 protein species as differentially represented. In particular, quantitative changes in the extracellular matrix, cytoskeletal and chaperone proteins, and in cell adhesion and signaling molecules were observed in osteochondrotic cells, compared to healthy controls. Functional group analysis annotated most of these proteins in “growth plate and cartilage development”, while others were included in “glycolysis and gluconeogenesis”, “positive regulation of protein import”, “cell–cell adhesion mediator activity”, and “mitochondrion nucleoid”. These results may help to clarify some chondrocyte functional alterations that may play a significant role in determining the onset and progression of equine osteochondrosis and, being related, of human juvenile osteochondrosis.

Osthole: A Coumarin Derivative Assuage Thiram-Induced Tibial Dyschondroplasia by Regulating BMP-2 and RUNX-2 Expressions in Chickens

Avian tibial dyschondroplasia affects fast growing broiler chickens accounting for almost 30% of leg ailments in broilers. The present project was designed to assess the efficacy of osthole against avian tibial dyschondroplasia (TD). Two hundred and forty chickens were equally allocated into control, TD and osthole groups (n = 80). The TD and osthole group chickens were challenged with tetramethylthiuram disulfide (thiram) at 50 mg/kg of feed from 4–7 days, followed by osthole administration at 20 mg/kg orally to the osthole group only from 8–18 days. Thiram feeding resulted in lameness, increased mortality, and decreased production parameters, alkaline phosphatase (ALP), superoxide dismutase (SOD), total antioxidant capacity (T-AOC), and glutathione peroxidase (GSH-PX) levels, along with significantly increased aspartate aminotransferase (AST), alanine aminotransferase (ALT), malondialdehyde (MDA) levels, and growth plate size. Moreover, the genes and protein expressions of BMP-2 and RUNX-2 were significantly down-regulated in TD affected chickens (p < 0.05). Osthole administration showed promising results by alleviating lameness; increased ALP, SOD, T-AOC, and GSH-Px levels; and decreased the AST, ALT, and MDA levels significantly. It restored the size of the growth plate and significantly up-regulated the BMP-2 and RUNX-2 expressions (p < 0.05). In conclusion, the oxidative stress and growth plate anomalies could be assuaged using osthole.

Ligustrazine recovers thiram-induced tibial dyschondroplasia in chickens: Involvement of new molecules modulating integrin beta 3

Tetramethyl thiuram disulfide (thiram) is a dithiocarbamate, which is extensively used in agriculture as pesticide and fungicide for treating grains intended for seed purposes and also for storing food grains. One of the most evident and detrimental effect produced by thiram is tibial dyschondroplasia (TD) in many avian species, by feeding diets containing thiram, a growth plate cartilage disease. TD is characterized by the lack of blood vessels and impaired vascular invasion of the hypertrophic chondrocyte resulting in the massive cell death. This study investigated the effects of ligustrazine on the treatment and control of thiram induced-TD. A total of 210 chicks were divided into three equal groups (n = 70): control group (received standard diet), TD group (feed on thiram containing diet from day 3-7), and ligustrazine group (feed on thiram containing diet from day 3-7 and after that ligustrazine @ 30 mg/kg from day 8 to day 18). During the experiment, the lameness, production parameters, tibia bone indicators, pathological index changes and integrin beta 3 (ITGB3) expressions were examined. The results reveal that ligustrazine plays an important role in improving angiogenesis and decreasing chondrocytes damage in TD chicks via a new molecule modulating ITGB3. So, the administration of ligustrazine can be an important way to cope with the losses and costs associated with TD in commercial poultry farming and animal welfare issue due to environmental contamination of thiram.

Light-dark rhythms during incubation of broiler chicken embryos and their effects on embryonic and post hatch leg bone development

There are indications that lighting schedules applied during incubation can affect leg health at hatching and during rearing. The current experiment studied effects of lighting schedule: continuous light (24L), 12 hours of light, followed by 12 hours of darkness (12L:12D), or continuous darkness (24D) throughout incubation of broiler chicken eggs on the development and strength of leg bones, and the role of selected hormones in bone development. In the tibiatarsus and femur, growth and ossification during incubation and size and microstructure at day (D)0, D21, and D35 post hatching were measured. Plasma melatonin, growth hormone, and IGF-I were determined perinatally. Incidence of tibial dyschondroplasia, a leg pathology resulting from poor ossification at the bone’s epiphyseal plates, was determined at slaughter on D35. 24L resulted in lower embryonic ossification at embryonic day (E)13 and E14, and lower femur length, and lower tibiatarsus weight, length, cortical area, second moment of area around the minor axis, and mean cortical thickness at hatching on D0 compared to 12L:12D especially. Results were long term, with lower femur weight and tibiatarsus length, cortical and medullary area of the tibiatarsus, and second moment of area around the minor axis, and a higher incidence of tibial dyschondroplasia for 24L. Growth hormone at D0 was higher for 24D than for 12L:12D, with 24L intermediate, but plasma melatonin and IGF-I did not differ between treatments, and the role of plasma melatonin, IGF-I, and growth hormone in this process was therefore not clear. To conclude, in the current experiment, 24L during incubation of chicken eggs had a detrimental effect on embryonic leg bone development and later life leg bone strength compared to 24D and 12L:12D, while the light-dark rhythm of 12L:12D may have a stimulating effect on leg health.

Icariin: a Potential Compound for the Recovery of Tibial Dyschondroplasia Affected Chicken Via Up-Regulating BMP-2 Expression

BACKGROUND

Tibial dyschondroplasia (TD) is a skeletal disease of fast growing chicken and other avian species. It is characterized by an avascular and non-mineralized growth plate, which leads to a deformed tibial bone and lameness. Unfortunately, this disease is not only responsible for causing huge economic losses but also raises animal welfare concerns. Icariin is a flavonoid, which is isolated from Epimedium pubescens herb, and it has been used to cure different diseases including bone fractures and osteoporosis.

RESULTS

We designed this experiment to use icariin for the treatment of TD affect chickens; for this purpose, a total of 180 chicks were equally divided into three groups: control, TD and icariin. All the three groups were offered ad libitum same normal standard diet with an addition of thiram (50 mg/kg) from 3rd day to 7th day in TD and icariin group in order to induce TD in chickens. After the induction of TD, the chickens in icariin groups were fed standard diet with an addition of icariin at the rate of 10 mg/kg in drinking water to check the therapeutic effect of this flavonoid on TD. Our results showed that the icariin helped in restoring the TD lesion into a normal structure with significantly (P < 0.05) up-regulating the bone morphogenetic protein-2 (BMP-2) expression in the tibial growth plates (GP).

CONCLUSIONS

Icariin increased the vascular area in the growth plate and decreased the average TD score. In conclusion, this study shows that icariin is a potential compound for the recovery of TD affected chickens via up-regulating the BMP-2 expression without posing a threat of ingestion of toxic veterinary drug residues to human beings upon the consumption of treated chickens.

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.

Targeted cancer therapy through 17-DMAG as an Hsp90 inhibitor: Overview and current state of the art

Heat shock protein 90 (Hsp90) is an evolutionary preserved molecular chaperone which mediates many cellular processes such as cell transformation, proliferation, and survival in normal and stress conditions. Hsp90 plays an important role in folding, maturation, stabilization and activation of Hsp90 client proteins which all contribute to the development, and proliferation of cancer as well as other inflammatory diseases. Functional inhibition of Hsp90 can have a massive effect on various oncogenic and inflammatory pathways, and will result in the degradation of their client proteins. This turns it into an interesting target in the treatment of different malignancies. 17-dimethylaminoethylamino-17-demethoxygeldanamycin (17-DMAG) as a semi-synthetic derivative of geldanamycin, has several advantages over 17-Allylamino-17-demethoxygeldanamycin (17-AAG) such as higher water solubility, good bioavailability, reduced metabolism, and greater anti-tumour capability. 17-DMAG binds to the Hsp90, and inhibits its function which eventually results in the degradation of Hsp90 client proteins. Here, we reviewed the pre-clinical data and clinical trial data on 17-DMAG as a single agent, in combination with other agents and loaded on nanomaterials in various cancers and inflammatory diseases.

Effect of Icariin on Tibial Dyschondroplasia Incidence and Tibial Characteristics by Regulating P2RX7 in Chickens

Tibial dyschondroplasia (TD) is a disease of rapid growing chickens that occurs in many avian species; it is characterized by nonvascular and nonmineralized growth plates, along with tibia bone deformation and lameness. Icariin is widely used to treat bone diseases in humans, but no report is available regarding the effectiveness of icariin against avian TD. Therefore, this study was designed to determine its effect against TD. For this purpose, a total of 180 broiler chicks were distributed into three groups including control, TD, and icariin group. Control group was given a standard normal diet, while TD and icariin groups received normal standard diet containing 50 mg/kg thiram to induce TD from days 3 to 7 after hatch. After the induction of TD, the chicks of icariin group were fed with standard normal diet by adding 10 mg/kg icariin in water. Then morphological and production parameters analysis of tibial bone indicators, physiological index changes, and gene expression were examined. The results showed that icariin administration not only decreased the mortality but also mitigated the lameness and promoted the angiogenesis, which diminished the TD lesion and significantly increased the expression of P2RX7 (P < 0.05) in TD affected thiram induced chicks. In conclusion, present findings suggest that icariin has a significant role in promoting the recovery of chicken growth plates affected by TD via regulating the P2RX7. Our findings reveal a new target for clinical treatment and prevention of TD in broiler chickens.

Role and regulation of growth plate vascularization during coupling with osteogenesis in tibial dyschondroplasia of chickens

Tibial dyschondroplasia (TD) is the most-prevalent leg disorder in fast-growing chickens; it is intractable and characterized by abnormal endochondral bone formation of proximal tibial growth-plates (TGPs). Previous studies have shown that bone is a highly vascularized tissue dependent on the coordinated coupling between angiogenesis and osteogenesis, but the underlying mechanisms of bone formation and bone remodeling are poorly defined in TD chickens. Here, we observed that inhibition of vasculogenesis and angiogenesis remarkably impaired vascular invasion in the hypertrophic chondrocyte zone of the TGPs, resulting in the massive death of chondrocytes due to a shortage of blood vessels and nutrients. Moreover, the balance of the OPG (osteoprotegerin)/RANKL (receptor activator of nuclear factor-kB ligand) system is also severely disrupted during the osteogenesis process while coupling with angiogenesis, both of which eventually lead to abnormal endochondral bone formation in TD chickens. Thus, the process of vascular formation in endochondral bone appears to initiate the pathological changes in TD, and improvement of this process during coupling with osteogenesis may be a potential therapeutic approach to treat this intractable disease.

Icariin Ameliorate Thiram-Induced Tibial Dyschondroplasia via Regulation of WNT4 and VEGF Expression in Broiler Chickens

Tibial dyschondroplasia (TD) is main bone problem in fast growing poultry birds that effect proximal growth plate (GP) of tibia bone. TD is broadly defined as non-vascularized and non-mineralized, and enlarged GP with tibia bone deformation and lameness. Icariin (Epimedium sagittatum) is a traditional Chinese medicine, which is commonly practiced in the treatment of various bone diseases. Recently, many researcher reports about the beneficial effects of icariin in relation to various types of bone conditions but no report is available about promoting effect of icariin against TD. Therefore, current study was conducted to explore the ameliorating effect of icariin in thiram-induced TD chickens. A total of 180 broiler chicks were equally distributed in three groups; control, TD induced by thiram (50 mg/kg), and icariin group (treated with icariin @10 mg/kg). All groups were administered with normal standard diet ad libitum regularly until the end of experiment. The wingless-type member 4 (WNT4) and vascular endothelial growth factor (VEGF) genes and proteins expression were analyzed by quantitative real-time polymerase chain reaction and western blot analysis respectively. Tibial bone parameters, physiological changes in serum, antioxidant enzymes, and chicken growth performance were determined to assess advantage and protective effect of the medicine in broiler chicken. The expression of WNT4 was decreased while VEGF increased significantly (P < 0.05) in TD affected chicks. TD enhanced the GP, lameness, and irregular chondrocytes, while reduced the liver function, antioxidant enzymes in liver, and performance of chickens. Icariin treatment up-regulated WNT4 and down-regulated VEGF gene and protein expressions significantly (P < 0.05), restored the GP width, increased growth performance, corrected liver functions and antioxidant enzymes levels in liver, and mitigated the lameness in broiler chickens. In conclusion, icariin administration recovered GP size, normalized performance and prevented lameness significantly. Therefore, icariin treatments are encouraged to reduce the incidence of TD in broiler chickens.

Effect of tetramethylpyrazine on tibial dyschondroplasia incidence, tibial angiogenesis, performance and characteristics via HIF-1α/VEGF signaling pathway in chickens

Tibial dyschodroplasia (TD) is a most common pathological condition in many avian species that is characterized by failure of growth plate (GP) modeling that leads to the persistence of avascular lesion in the GP. Tetramethylpyrazine (TMP) is widely used to treat neurovascular disorders and pulmonary hypertension, but no report is available about promoting effect of TMP against TD. Therefore, a total of 210 broiler chicks were equally divided into three groups; Control, TD and TMP. During the experiment mortality rate, chicken performance indicators (daily weight, average daily feed intake, average daily weight gain and feed conversion ratio), tibia bone indicators (weight, length, width of tibial and the size of GP) in addition to gene expression of HIF-1α and VEGF were examined. The results showed that TMP administration restore the GP width, increase growth performance, and mitigated the lameness in broiler chickens. The expression of HIF-1α and VEGF increased significantly in TD affected thiram induced chicks. Whereas, TMP treatment down-regulated HIF-1α and VEGF genes and proteins expressions. The present study demonstrates that the TMP plays an important role in angiogenesis during the impairment and recovery of GP in TD via regulation of the HIF-1α/VEGF signaling pathway in chickens.

Oxygen Supplementation Ameliorates Tibial Development via Stimulating Vascularization in Tibetan Chickens at High Altitudes

Tibetan chickens (TBCs) living in high-altitude hypoxic environment, are characterized by delayed growth and small size as compared to low-altitude broiler chickens. Increasing evidences signify the beneficial effect of oxygen (O₂) supplementation in animal's body for regulating their body growth and organ development. However, it is still unclear that whether O₂ supplementation has an ameliorative and protective role in TBCs living at high altitude. In this study, we first found that O₂ supplementation not only increased the survival rate but also promoted the growth of TBCs associated with bone development. Importantly, we observed that the increase of vascular distribution in the tibial hypertrophic zone could contribute to promote growth and development of the tibia, which is highly correlated with the up-regulated expression level of vascular endothelial growth factor (VEGF)-A and VEGF receptor-1 (VEGFR1). Additionally, hypoxia inducible factor (HIF)-1ɑ also has a stimulative elevation by O₂ supplementation. These results were confirmed by histology, immunohistochemistry, qRT-PCR and Western blotting techniques. Altogether, these findings demonstrated that the up-regulation of VEGFA and its receptors are accompanied by proangiogeneic factor (HIF-1α) expression, which were required for angiogenesis to meliorate tibia development of TBCs in hypoxia-induced bone suppression that occurred during O₂ supplementation. Thus, O₂ supplementation may serve as a good applicant for promoting and meliorating bone development in juvenile high-altitude animals.

Tibial dyschondroplasia is highly associated with suppression of tibial angiogenesis through regulating the HIF-1α/VEGF/VEGFR signaling pathway in chickens

Tibial dyschondroplasia (TD) is an intractable poultry problem that is characterized by the appearance of non-vascularized and non-mineralized cartilage masses in tibial growth plates (TGPs). However, the role of angiogenesis inhibition in the occurrence of TD remains unknown. In this study, we found that, compared to low-altitude Arbor Acres chickens (AACs), high-altitude Tibetan chickens showed higher tibial vascular distributions that were accompanied by up-regulation of hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor A (VEGFA) and VEGF receptors. These observations provide insights into hypoxia-induced angiogenesis, which may be related to the absence of TD in high-altitude native Tibetan chickens. Importantly, hypoxia experiments also showed that during hypoxia, tibial angiogenesis was enhanced, which was due to pro-angiogenic factor up-regulation (including VEGFA, VEGFR1, VEGFR2, and IL-8), in AACs. Moreover, we observed that thiram-induced TD could strongly inhibit tibial angiogenesis in the hypertrophic zone through coordinated down-regulation of HIF-1α and pro-angiogenic factors, leading to a disruption in the blood supply to the TGP. Taken together, these findings reveal that the occurrence of TD is highly associated with inhibition of tibial angiogenesis through down-regulated expression of HIF-1α, VEGFA and VEGF receptors, which results in suppression of TGP development.

High altitude hypoxia as a factor that promotes tibial growth plate development in broiler chickens

Tibial dyschondroplasia (TD) is one of the most common problems in the poultry industry and leads to lameness by affecting the proximal growth plate of the tibia. However, due to the unique environmental and geographical conditions of Tibet, no case of TD has been reported in Tibetan chickens (TBCs). The present study was designed to investigate the effect of high altitude hypoxia on blood parameters and tibial growth plate development in chickens using the complete blood count, morphology, and histological examination. The results of this study showed an undesirable impact on the overall performance, body weight, and mortality of Arbor Acres chickens (AACs) exposed to a high altitude hypoxic environment. However, AACs raised under hypoxic conditions showed an elevated number of red blood cells (RBCs) and an increase in hemoglobin and hematocrit values on day 14 compared to the hypobaric normoxia group. Notably, the morphology and histology analyses showed that the size of tibial growth plates in AACs was enlarged and that the blood vessel density was also higher after exposure to the hypoxic environment for 14 days, while no such change was observed in TBCs. Altogether, our results revealed that the hypoxic environment has a potentially new role in increasing the blood vessel density of proximal tibial growth plates to strengthen and enhance the size of the growth plates, which may provide new insights for the therapeutic manipulation of hypoxia in poultry TD.

Differential expression of extracellular matrix metalloproteinase inducer (EMMPRIN/CD147) in avian tibial dyschondroplasia

Tibial dyschondroplasia (TD) is an avian bone disorder of different aetiologies that may be associated with lameness. The disorder is characterized by focal disruption of endochondral bone formation, with a lack of matrix proteolysis and an accumulation of non-mineralized avascular cartilage. The aim of this study was to determine the expression of extracellular matrix metalloproteinase inducer (EMMPRIN/CD147) in normal, thiram-induced TD lesions and in the process of recovery from TD in broiler chickens. An extracellular matrix (ECM) degrading enzyme, matrix metalloproteinase-9 (MMP-9), was selected to investigate the effects of CD147 in the degradation of ECM. Gene expression was analysed by quantitative real-time polymerase chain reaction and protein levels by immunohistochemistry and western blotting. The birds were divided into three groups: thiram fed; recovery; and controls. Genes encoding CD147 and MMP-9 were down-regulated during the development of the disease, and were up-regulated during recovery. Western blotting also showed lower protein levels of CD147 in TD, which increased during the recovery phase associated with ECM degradation and growth plate repair. The findings of this study suggest that ECM has a crucial role in the occurrence of TD and that CD147 appears to play a pivotal role in matrix proteolysis in the chicken, similar to that in other species.

Screening of differentially expressed genes in the growth plate of broiler chickens with tibial dyschondroplasia by microarray analysis

Background

Tibial dyschondroplasia (TD) is a common skeletal disorder in broiler chickens. It is characterized by the presence of a non-vascularized and unmineralized cartilage in the growth plate. Previous studies have investigated differential expression of genes related to cartilage development during latter stages of TD. The aim of our study was to identify differentially expressed genes (DEGs) in the growth plate of broiler chickens, which were associated with early stage TD. We induced TD using tetramethylthiuram disulfide (thiram) for 1, 2, and 6 days and determined DEGs with chicken Affymetrix GeneChip assays. The identified DEGs were verified by quantitative polymerase chain reaction (qPCR) assays.

Results

We identified 1630 DEGs, with 82, 1385, and 429 exhibiting at least 2.0-fold changes (P < 0.05) at days 1, 2, and 6, respectively. These DEGs participate in a variety of biological processes, including cytokine production, oxidation reduction, and cell surface receptor linked signal transduction on day 1; lipid biosynthesis, regulation of growth, cell cycle, positive and negative gene regulation, transcription and transcription regulation, and anti-apoptosis on day 2; and regulation of cell proliferation, transcription, dephosphorylation, catabolism, proteolysis, and immune responses on day 6. The identified DEGs were associated with the following pathways: neuroactive ligand-receptor interaction on day 1; synthesis and degradation of ketone bodies, terpenoid backbone biosynthesis, ether lipid metabolism, JAK-STAT, GnRH signaling pathway, ubiquitin mediated proteolysis, TGF-β signaling, focal adhesion, and Wnt signaling on day 2; and arachidonic acid metabolism, mitogen-activated protein kinase (MAPK) signaling, JAK-STAT, insulin signaling, and glycolysis on day 6. We validated seven DEGs by qPCR.

Conclusions

Our findings demonstrate previously unrecognized changes in gene transcription associated with early stage TD. The DEGs we identified by microarray analysis will be used in future studies to clarify the molecular pathogenic mechanisms of TD. From these findings, potential pathways involved in early stage TD warrant further investigation.

FGFR3 targeting strategies for achondroplasia

Mutations that exaggerate signalling of the receptor tyrosine kinase fibroblast growth factor receptor 3 (FGFR3) give rise to achondroplasia, the most common form of dwarfism in humans. Here we review the clinical features, genetic aspects and molecular pathogenesis of achondroplasia and examine several therapeutic strategies designed to target the mutant receptor or its signalling pathways, including the use of kinase inhibitors, blocking antibodies, physiologic antagonists, RNAi and chaperone inhibitors. We conclude by discussing the challenges of treating growth plate disorders in children.