Development of avian tibial dyschondroplasia: gene expression and protein synthesis

Morinda officinalis Polysaccharides Ameliorates Bone Growth by Attenuating Oxidative Stress and Regulating the Gut Microbiota in Thiram-Induced Tibial Dyschondroplasia Chickens

Tibial dyschondroplasia (TD) occurs in chickens and other fast-growing birds, affecting their cartilage growth and leading to reduced meat quality in broilers. Morinda officinalis polysaccharide (MOP) is one of the chief active components of Morinda officinalis, which promotes bone formation, inhibiting bone loss and having anti-oxidant and anti-inflammatory properties. A total of 120 AA chickens were randomly divided into the CON group (basal diet), TD group (100 mg/kg thiram + basal diet), and MOP group (100 mg/kg thiram + basal diet + water with 500 mg/kg MOP). The experiment lasted 21 days. The results showed that MOP could alleviates broiler lameness caused by TD, restore the morphological structure of tibial growth plate (TGP), increase tibial weight (p < 0.05), balance the disorder of calcium and phosphorus metabolism, and promote bone formation by increasing the expression of BMP-2, Smad4, and Runx2 genes In addition, MOP supplementation stimulated the secretion of plasma antioxidant enzymes (T-SOD and GSH-Px) by regulating the expression of SOD and GPX-1 genes, thereby enhancing the antioxidant capacity of TD broilers. Interestingly, we observed MOP can also improve gut microbiota by increasing the beneficial bacteria count and decreasing the harmful bacteria count. These findings indicated that MOP can regulate bone formation through the BMP/Smads signaling pathway, attenuating oxidative stress and regulating the gut microbiota of TD broilers, so as to achieve the effect of treating TD. This suggests that MOP might be a potential novel drug in the treatment of TD in chickens.

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.

Ameliorative effect of naringin against thiram-induced tibial dyschondroplasia in broiler chicken

Tetramethyl thiuram disulfide (thiram) is widely used in agricultural production as an insecticide and fungicide, which can also lead to tibial dyschondroplasia (TD) in poultry. TD is characterized by leg disorders and growth performance retardation, and no targeted drugs have been found to treat TD until now. Therefore, the objective of the present study was to explore the ameliorative effect of traditional Chinese medicine naringin on thiram-induced TD chickens. A total of 180 one-day-old Arbor Acres (AA) broiler chickens were randomly divided into three equal groups (n = 60): control group (standard diet), thiram-induced group (thiram 50 mg/kg from day 3 to day 7), and naringin-treated group (naringin 30 mg/kg from day 8 to day 18). During the 18-day experiment, the growth performance, tibial bone parameters, antioxidant property of liver, serum biochemical changes and clinical symptoms were recorded to evaluate the protective effect of naringin in thiram-induced TD broiler chickens. Additionally, mRNA expressions and protein levels of Ihh and PTHrP genes were determined via quantitative real-time polymerase chain reaction and western blot. Administration of naringin showed significant results by alleviating lameness, increased growth performance, recuperated growth plate (GP) width, and improved functions and antioxidant enzyme level of liver in broilers affected by TD. Moreover, naringin treatment restored the development of damaged tibia bone via downregulating Ihh and upregulating PTHrP mRNA and protein expressions. In conclusion, our study determines naringin could be used as an effective medicine to treat TD.

Plastrum Testudinis Extract Mitigates Thiram Toxicity in Broilers via Regulating PI3K/AKT Signaling

Tibial dyschondroplasia (TD) negatively affects broilers all over the world, in which the accretion of the growth plate (GP) develops into tibial proximal metaphysis. Plastrum testudinis extract (PTE) is renowned as a powerful antioxidant, anti-inflammatory, and bone healing agent. The current study was conducted to evaluate the efficacy of PTE for the treatment of thiram-induced TD chickens. Broilers (day old; n = 300) were raised for 3 days with normal feed. On the 4th day, three groups (n = 100 each) were sorted, namely, the control (normal diet), TD, and PTE groups (normal diet+ thiram 50 mg/kg). On the 7th day, thiram was stopped in the TD and PTE group, and the PTE group received a normal diet and PTE (30 mg/kg/day). Plastrum testudinis extract significantly restored (p < 0.05) the liver antioxidant enzymes, inflammatory cytokines, serum biochemicals, GP width, and tibia weight as compared to the TD group. The PTE administration significantly increased (p < 0.05) growth performance, vascularization, AKT (serine/threonine-protein kinase), and PI3K expressions and the number of hepatocytes and chondrocytes with intact nuclei were enhanced. In conclusion, PTE has the potential to heal TD lesions and act as an antioxidant and anti-inflammatory drug in chickens exposed to thiram via the upregulation of AKT and PI3K expressions.

Clinical efficiency and safety of Hsp90 inhibitor Novobiocin in avian tibial dyschondroplasia

Tibial dyschondroplasia (TD) is a bone defect of broilers and other poultry birds that disturbs growth plate and it causes lameness. Previously we evaluated differential expression of multiple genes involved in growth plate angiogenesis and reported the safety and efficacious of medicinal plant root extracted for controlling TD. In this study, clinical and protective effect of an antibiotic Novobiocin (Hsp90 inhibitor) and expression of Hsp90 and proteoglycan aggrecan was examined. The chicks were divided into three groups; Control, thiram-induced TD, and Novobiocin injected TD. After the induction of TD, the Novobiocin was administered through intraperitoneal route to TD-affected birds until the end of the experiment. The expressions and localization of Hsp90 were evaluated by qRT-PCR, immunohistochemistry (IHC) and western blot, respectively. Morphological, histological examinations, and serum biomarker levels were evaluated to assess specificity and protective effects of Novobiocin. The results showed that TD causing retarded growth, enlarged growth plate, distended chondrocytes, irregular columns of cells, decreased antioxidant capacity, reduced protein levels of proteoglycan aggrecan, and upregulated in Hsp90 expression (p < 0.05) in dyschondroplastic birds as compared with control. Novobiocin treatment restored growth plate morphology, reducing width, stimulated chondrocyte differentiation, sprouting blood vessels, corrected oxidative imbalance, decreased Hsp90 expressions and increased aggrecan level. Novobiocin treatment controlled lameness and improved growth in broiler chicken induced by thiram. In conclusion, the accumulation of the cartilage and up-regulated Hsp90 are associated with TD pathogenesis and irregular chondrocyte morphology in TD is along with reduced aggrecan levels in the growth plate. Our results indicate that Novobiocin treatment has potential to reduce TD by controlling the expression of Hsp90 in addition to improve growth and hepatic toxicity in broiler chicken.

Comparative analysis of gut microbial community in healthy and tibial dyschondroplasia affected chickens by high throughput sequencing

Tibial dyschondroplasia (TD) is a common skeletal problem of avian species. The cause and etiology of this disorder is still not clear. The intestinal bacterial community is a complex ecosystem and plays very important role in healthy life of human and animals. Many researchers have made the connection between diseases and alteration of gut microbiota. However, little is know about the role of gut microbiota in TD. The objective of this study was to explore the diversity and composition of small and large intestinal bacterial communities of TD chickens. The intestinal contests were collected from healthy and TD chickens at day 18 of the trail. The V3-V4 region of 16S rDNA was amplified and sequenced by high-throughput sequencing. Our results indicated that healthy chickens had higher abundance and diversity of gut microbiota than TD chickens but there was no significant difference (P > 0.05) among the gut microbiota of small and large intestine. However, the composition of bacterial communities were significantly different (P < 0.05) between healthy and TD chickens. The occurrence of gut pathogens associated with immunity and inflammation were much higher in the intestinal contests of TD chickens as compared to healthy ones. In summary, our results showed an interesting difference of gut microbiota between healthy and TD chickens, which provided a new thought about the pathogenesis of TD.

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.

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.

Correlation between broiler lameness and anatomical measurements of bone using radiographical projections with assessments of consistency across and within radiographs

Lameness represents a major welfare and production issue in the poultry industry with a recent survey estimating 27% of birds lame and 3% unable to walk by 40 d of age. A variety of factors may induce lameness and are typically grouped into 2 broad classes on the basis of being infectious or skeletal in nature with the latter accounting for the majority of cases. The current work sought to build upon a large body of literature assessing the anatomical properties of bone in lame birds. Our specific objectives sought to identify relationships between relevant anatomical properties of the tibia and metatarsus using digital quantification from radiographs of legs and a measure of walking difficulty. Resulting output was statistically analyzed to assess 1) observer reliability for consistency in placing the leg during the radiograph procedure and quantification of the various measures within a radiograph, 2) the relationship between the various measurements of anatomical bone properties and sex, bird mass, and gait score, and 3) the relationship between each measurement and leg symmetry. Our anatomical bone measures were found to be reliable (intra-rater and test-retest reliabilities < 0.75) within radiograph for all measures and 8 of the 10 measures across radiographs. Several measures of bone properties in the tibia correlated to difficulty walking as measured by gait score (P < 0.05), indicating greater angulations with increasing lameness. Of the measures that manifested a gait score × bird mass interaction, heavier birds appeared to exhibit less angulation with increasing difficulty walking with lighter birds the opposite. These interactions suggest possibilities for influencing effects of activity or feed intake on bone mineralization with the bone angulation observed. Our efforts agree with that of others and indicate that angulation of the tibia may be related to lameness, though subsequent efforts involving comprehensive measures of bird activity, growth rates, and internal bone structure will be needed if the validity of the measures are to be accepted.

The Ihh signal is essential for regulating proliferation and hypertrophy of cultured chicken chondrocytes

The Indian hedgehog (Ihh) signal plays a vital role in regulating proliferation and hypertrophy of chondrocytes. To investigate its function in postnatal chicken (Gallus gallus) chondrocytes, cyclopamine was used to inhibit Ihh signaling. The MTT and ALP assays revealed the downgrade-proliferation and upgrade-differentiation of chondrocytes. To further elucidate the mechanism, the mRNA expression levels of Ihh, parathyroid hormone related protein (PTHrP), Gli-2, Bcl-2, Bone Morphogenetic Protein 6 (BMP-6), type X collagen (Col X) and type II collagen (Col II) were detected by quantitative real-time RT-PCR analysis, and the protein expressions of Ihh, Col X, and Col II were determined using Western blot analysis. After the Ihh signal was blocked, chondrocytes demonstrated high expression levels of PTHrP and Col X and low levels of Gli-2, BMP-6, Bcl-2 and Col II although Ihh expression was increased. Based on these results, the Ihh signal is essential for balancing chicken chondrocyte proliferation and hypertrophy, and the regulatory function of PTHrP acts in an Ihh-dependent manner. Furthermore, BMP-6 and Bcl-2 played roles in maintaining the development of chondrocytes and may be downstream regulatory factors of Ihh signaling.

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

Thiram-induced tibial dyschondroplasia (TD) and vitamin-D deficiency rickets are avian bone disorders of different etiologies characterized by abnormal chondrocyte differentiation, enlarged and unvascularized growth plates, and lameness. Heat-shock protein 90 (Hsp90) is a proangiogenic factor in mammalian tissues and in tumors; therefore, Hsp90 inhibitors were developed as antiangiogenic factors. In this study, we evaluated the association between Hsp90, hypoxia, and angiogenesis in the chick growth plate. Administration of the Hsp90 inhibitor to TD- and rickets-afflicted chicks at the time of induction resulted in reduction in growth-plate size and, contrary to its antiangiogenic effect in tumors, a major invasion of blood vessels occurred in the growth plates. This was the result of upregulation of the VEGF receptor Flk-1, the major rate-limiting factor of vascularization in TD and rickets. In addition, the abnormal chondrocyte differentiation, as characterized by collagen type II expression and alkaline phosphatase activity, and the changes in hypoxia-inducible factor-1α (HIF-1α) in both disorders were restored. All these changes resulted in prevention of lameness. Inhibition of Hsp90 activity reduced growth-plate size, increased vascularization, and mitigated lameness also in TD chicks with established lesions. In summary, this is the first reported demonstration of involvement of Hsp90 in chondrocyte differentiation and growth-plate vascularization. In contrast to the antiangiogenic effect of Hsp90 inhibitors observed in mammals, inhibition of Hsp90 activity in the unvascularized TD- and rickets-afflicted chicks resulted in activation of the angiogenic switch and reinstated normal growth-plate morphology.

Identification of differentially expressed genes in the growth plate of broiler chickens with thiram-induced tibial dyschondroplasia

Tibial dyschondroplasia (TD) is characterized by expansion of the proximal growth plates of the tibiotarsus that fail to form bone, lack blood vessels, and contain non-viable cells. Thiram (a carbamate pesticide), when fed to young broiler chicks, induces TD with high regularity and precision. We used this experimental model to understand the cause of the defects associated with TD by selecting and identifying the genes differentially expressed in the TD growth plate of broiler chickens. Broiler chicks at 7 days of age were randomly divided into two groups. After fasting overnight, they were fed with regular diet (control) or the same diet containing 100 mg/kg thiram for 96 h to induce TD (thiram-fed). mRNA was purified from the growth plates of control and thiram-fed broilers. Forward and reverse-subtracted cDNA libraries were generated by suppression subtractive hybridization technology. Ten selected genes from cDNA libraries were identified by real-time quantitative polymerase chain reaction. All were differentially expressed in TD growth plates (P<0.05 or P<0.01). The levels of collagen type X (Col X), pro-alpha-1 collagen type I (Col I alpha1), collagen type IX (Col IX), NADH dehydrogenase (NADH DH), cytochrome C oxidase subunit III (COX III), enolase 1, alpha (ENO1), carbonic anhydrase II (CA2) and heat shock protein 90 (Hsp90) mRNA transcripts were up-regulated, while the expression levels of Matrilin 3 (MATN3) and chondromodulin-I (ChM-I) were down-regulated. Col I and Hsp90 were detected by immunohistochemistry at different stages. Given that these genes are involved in matrix formation, endochondral ossification, developmental regulation, electron transport in the mitochondrial respiratory chain and vascularization, our findings may provide new insights into understanding the pathogenesis of TD.

Ovocleidin (OC 116) is present in avian skeletal tissues

Ovocleidin (OC-116), a protein identified in eggshell matrix, was found to be expressed in avian growth plate chondrocytes. Because OC-116 has been reported to be a member of a family of related phosphoprotein genes clustered on avian chromosome 4, we expanded our search to other skeletal tissues. Using Western blotting, we found OC-116 in the matrix of chick cortical bone and laying hen medullary bone as well as in hypertrophic chondrocyte lysates. Furthermore, other members of this family (bone sialoprotein, dental matrix protein-1, and osteopontin) were also present in the eggshell matrix. Reverse transcription-PCR was used to confirm the presence of the OC-116 gene in bone tissues as well as the expression of bone sialoprotein and dental matrix protein-1 in uterine tissue. These results, in combination with those of other laboratories, show that this family of phosphoproteins is found in a wide variety of avian mineralized tissues.

Tibial dyschondroplasia 40 years later

Tibial dyschondroplasia is a disease of rapid growth rate that occurs in many avian species. It is characterized by an avascular lesion in which the life span of the growth plate chondrocyte is essentially doubled. A characteristic pattern of gene expression and gene product localization has emerged that mimics the pattern observed with endoplasmic reticulum (ER) stress in growth plate chondrocytes. This activates a cell-survival mechanism called autophagy. The initial phases of this mechanism appear to originate in the avascular transition zone of the growth plate. Because specific genes and gene products are associated with autophagy and ER stress, it should now be possible to identify the mechanisms involved in the development of this cartilage abnormality. The potential biochemical pathways responsible for initiating ER stress are discussed.

Effect of temperature during the incubation period on tibial growth plate chondrocyte differentiation and the incidence of tibial dyschondroplasia

Tibial dyschondroplasia (TD) is one of the most prevalent skeletal abnormalities in avian species, causing enormous economic losses and major animal welfare problems. Irregular cell differentiation of the chondrocytes that populate the growth plate has been hypothesized to be involved in the etiology of the disease. We evaluated the effect of incubation temperature at various stages of embryo development and bone formation on growth plate chondrocyte differentiation and the incidence of TD. Eggs were incubated either at a control temperature of 37.8 degrees C, or at 36.9 or 39 degrees C, each for 6 h/ d, during early (0 to 8 d) or late (10 to 18 d) embryo development. At 14 d of incubation and at hatch, tibias were collected and weighed, and their ash and calcium contents were determined. Growth plate chondrocyte differentiation was evaluated by alkaline phosphatase activity and collagen type II and osteopontin gene expression. In addition, the level of the heat-shock protein 90 (Hsp90) was evaluated by immunohistochemistry. The rest of the chicks were raised to 49 d and the incidence of TD was recorded. The incidence of TD increased only when the temperature was altered at the early stages of embryo development, and it was correlated with an increase in tibia ash but not with tibia weight or calcium content. Moreover, increased TD incidence was correlated with delayed chondrocyte differentiation. Early changes in incubation temperature caused an increase in the level of Hsp90 in articular and differentiated chondrocytes of the hypertrophic zone and in the numbers of distinct undifferentiated chondrocytes arranged in columns in the proliferative zone of the growth plate. In summary, the early stages of embryo development and bone formation are of utmost importantance for appropriate growth plate chondrocyte differentiation, and any temperature deviation will increase the subsequent incidence of TD. The increase in TD incidence is probably the result of delayed Hsp90-driven chondrocyte differentiation, supporting the hypothesis that TD is the result of abnormal chondrocyte differentiation.

Differential regulation of MMPs and matrix assembly in chicken and turkey growth-plate chondrocytes

Matrix metalloproteinases (MMPs) play a crucial role in growth-plate vascularization and ossification by processes involving proteolytic cleavage and remodeling of the extracellular matrix (ECM). Their regulation in the growth plate is crucial for normal vs. impaired matrix assembly. Tibial dyschondroplasia (TD), a prevalent skeletal abnormality in avian species, is characterized by the formation of a nonvascularized, nonmineralized plaque in the growth plate. Here, we show differential regulation of MMPs in cultured chondrocytes from chickens and turkeys; retinoic acid (RA) elevated MMP-2 activity in both species, but only in chicken did it induce MMP-9 activity. In contrast, phorbol 12-myristate 13-acetate (PMA) treatment induced MMP-9 activity in turkey chondrocytes but not in those of chicken. Moreover, we found different developmental patterns of TD in chickens and turkeys in-vivo as lower concentrations of, and shorter exposure to thiram were required in chicken than in turkey for TD induction. Growth-plate cartilage taken from thiram-induced lesions had lower gelatinolytic and caseinolytic activities compared with normal cartilage. Likewise, thiram reduced MMP-2 and MMP-13 activity in both chicken and turkey chondrocytes in vitro, although 10-fold higher concentrations were required for this effect in the latter. Finally, the combined treatments of RA or PMA with thiram induced MMP-9 activity in turkey but not in chicken chondrocytes. Furthermore, RA combined with thiram synergistically upregulated its activity in turkey but not chicken chondrocytes. Taken together, these results suggest that mechanisms of MMP regulation differ in the growth plates of these closely related avian species, resulting in altered matrix assembly as exemplified by TD development.

Mutation analysis of the aggrecan gene in chickens with tibial dyschondroplasia

Expression studies suggest that the incidence and severity of tibial dyschondroplasia (TD) in chickens, Gallus gallus, may be affected by the aggrecan gene, AGC 1. Here, results are described of a scan for single nucleotide polymorphisms (SNP) in AGC1 in genetic lines divergently selected for TD incidence in chickens. A total of 3,048 bp of DNA sequence obtained from amplicons produced by 4 primer-pairs designed from the GenBank AGC1 cDNA sequence were scanned for SNP. Among the 18 SNP detected and validated, only 2 were nonsynonymous. Allelic frequency differences between TD-affected and nonaffected birds were not statistically significant for all the SNP. The current results do not support an association of Gallus gallus AGC1 variation at the DNA level with the incidence of TD in chickens. The genomic resources described, however, including the SNP, could be useful in further evaluating AGC1 in other populations for association with TD or other skeletal abnormalities.

Changes in the Tibial Growth Plates of Chickens with Thiram-induced Dyschondroplasia

Tibial dyschondroplasia (TD) is a metabolic cartilage disease of young poultry in which endochondral bone formation is disrupted leading to the retention of a non-calcified, avascular plug of cartilage in the tibial growth plate. Chicks aged 7 days were fed either a control diet or one containing thiram 100 ppm for 48 h to induce TD. Cell multiplication in the growth plate was determined thereafter with bromodeoxyuridine (BrdU) labelling, and metabolic changes by measuring alkaline phosphatase (ALP), tartrate-resistant acid phosphatase (TRAP), and glutathione (GSH) activities. The effect on chondrocyte maturation was examined by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of gene expression. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) and DNA fragmentation were used to determine the effects of thiram on cell survival. The results showed that thiram-induced TD was not due to the multiplication of cells in the post-proliferative zones. Thiram did not affect ALP activity, which would have indicated a loss of calcification potential, but it reduced both TRAP and the glutathione concentrations, suggesting that the growth plate metabolism and remodelling functions were adversely affected. Thiram appeared to have no effect on the expression of type X collagen, transglutaminase, RUNX2, or matrix metalloproteinase-2 (MMP) genes suggesting that it did not alter the maturation potential of chondrocytes. On the contrary, the expressions of MMP-13 and vascular endothelial growth factor (VEGF) genes were "up-regulated," suggesting that thiram has pro-angiogenic activity. However, TUNEL assay showed that thiram induced endothelial cell apoptosis in the capillary vessels of the growth plates, as early as 10 days of age, when TD was not visually evident. The vascular death increased on subsequent days accompanied by massive death of chondrocytes in the transition zone of the growth plate. The induction of apoptosis in the growth plate was also demonstrated by DNA fragmentation. It was concluded that thiram induced TD not through an increase in the multiplication of chondrocytes in the transition zone and not by altering the expression of genes causing the arrest of chondrocytes in a prehypertrophic state, but by creating a metabolic dysfunction which led to the destruction of blood capillaries in the transition zone chondrocytes.

Weight loading young chicks inhibits bone elongation and promotes growth plate ossification and vascularization

The mechanical stimuli resulting from weight loading play an important role in mature bone remodeling. However, the effect of weight loading on the developmental process in young bones is less well understood. In this work, chicks were loaded with bags weighing 10% of their body weight during their rapid growth phase. The increased load reduced the length and diameter of the long bones. The average width of the bag-loaded group's growth plates was 75 ± 4% that of the controls, and the plates showed increased mineralization. Northern blot analysis, in situ hybridization, and longitudinal cell counting of mechanically loaded growth plates showed narrowed expression zones of collagen types II and X compared with controls, with no differences between the relative proportions of those areas. An increase in osteopontin (OPN) expression with loading was most pronounced at the bone-cartilage interface. This extended expression overlapped with tartarate-resistant acid phosphatase staining and with the front of the mineralized matrix in the chondro-osseous junction. Moreover, weight loading enhanced the penetration of blood vessels into the growth plates and enhanced the gene expression of the matrix metalloproteinases MMP9 and MMP13 in those growth plates. On the basis of these results, we speculate that the mechanical strain on the chondrocytes in the growth plate causes overexpression of OPN, MMP9, and MMP13. The MMPs enable penetration of the blood vessels, which carry osteoclasts and osteoblasts. OPN recruits the osteoclasts to the cartilage-bone border, thus accelerating cartilage resorption in this zone and subsequent ossification which, in turn, contributes to the observed phenotype of narrower growth plate and shorter bones.

Chondrocytes isolated from tibial dyschondroplasia lesions and articular cartilage revert to a growth plate-like phenotype when cultured in vitro

We report here a comparative study of the development and behavior of chondrocytes isolated from normal growth plate tissue, tibial dyschondroplasic lesions, and from articular cartilage. The objective of these studies was to determine whether the properties exhibited by chondrocytes in dysplasic lesions or in articular cartilage were due to their cellular phenotype, their environment, or both. We had previously analyzed the electrolytes and amino acid levels in the extracellular fluid of avian growth plate chondrocytes. Using these data, we constructed a culture medium (DATP5) in which growth plate cells essentially recapitulate their normal behavior in vivo. Here, we used DATP5 to examine the behavior of chondrocytes isolated from lesions of tibial dyschondroplasia (TD). We found that once isolated from lesion and grown in this supportive medium, dysplasic chondrocytes behaved essentially like normal growth plate cells. These findings suggest that the cause of TD is local factors operating in vivo to prevent these cells from developing normally. With respect to articular chondrocytes, our data indicate that they more closely retain normal protein and proteoglycan synthesis when grown in serum-free media. These cells readily induced mineral formation in vitro, both in the presence and absence of serum. However, in serum-containing media, mineralization was significantly enhanced when the cells were exposed to retinoic acid (RA) or osteogenic protein-1 (OP-1). Our studies support previous work indicating the presence of autocrine factors produced by articular chondrocytes in vivo that prevent mineralization and preserve matrix integrity. The lack of inhibitory factors and the presence of supporting factors are likely reasons for the induction of mineralization by articular chondrocytes in vitro.

Localization of osteopontin in oviduct tissue and eggshell during different stages of the avian egg laying cycle

The avian eggshell is an acellular bioceramic containing organic and inorganic phases that are sequentially assembled during the time the egg moves along the oviduct. As it has been demonstrated in other mineralized tissues, mineralization of the eggshell is regulated by extracellular matrix proteins especially the anionic side chains of proteoglycans. Among them, osteopontin has been found in the avian eggshell and oviduct. However, its precise localization in the eggshell or in different oviduct regions during eggshell formation, nor its function have been established. By using anti-osteopontin antibody (OPN 1), we studied its immunolocalization in the isthmus, red isthmus and shell gland of the oviduct, and in the eggshell during formation. In the eggshell, osteopontin was localized in the core of the non-mineralized shell membrane fibers, in the base of the mammillae and in the outermost part of the palisade. In the oviduct, OPN 1 was localized in the ciliated epithelial but not in the tubular gland cells of the isthmus, in the ciliated epithelial cells of the red isthmus, and in the non-ciliated epithelial cells of the shell gland. The occurrence of osteopontin in each of the oviduct regions, coincided with the concomitant presence of the egg in such region. Considering the reported inhibitory function of osteopontin in other mineralized systems, together with its main occurrence in the non-mineralized parts of the eggshell and at the outermost part of the shell, suggests that this molecule could be part of the mechanism regulating the eggshell calcification.

Discondroplasia tibial: mecanismos de lesão e controle

A discondroplasia tibial (DT) é atribuída a uma assincronia no processo de diferenciação dos condrócitos, levando à formação de uma camada de condrócitos pré-hipertróficos e de uma cartilagem na tíbia proximal que não é calcificada, mas é resistente à invasão vascular. Além disso, tem sido proposto que, na discondroplasia tíbial, a etapa final do processo de calcificação não ocorre devido ao fato de que os efetores de alguns genes, relacionados com o mecanismo de calcificação do disco de crescimento podem apresentar algumas de suas propriedades químicas ou biológicas alteradas e/ou não serem expressos. Nesse sentido, a compreensão do mecanismo de ação e o papel das biomoléculas e dos minerais relacionados com a discondroplasia tibial poderão contribuir para o conhecimento de doenças do tecido ósseo e estabelecer estratégias de prevenção e tratamento.

Collagen X expression in oviduct tissue during the different stages of the egg laying cycle

The purpose of this investigation was to study the expression of type X collagen in the hen's oviduct. Type X collagen is a short-chain collagen that is present in the fibers of eggshell membranes, and there is evidence to suggest that it contributes to structural integrity. In situ hybridization and Northern blot analysis were used to study the expression of this important matrix constituent. The results demonstrated that gene expression was predominantly in the tubular gland cells of the isthmus segment of the oviduct. In contrast to observations with other matrix proteins, such as parathyroid hormone-related peptide and osteopontin, gene expression did not fluctuate with the position of the egg in the oviduct.

Chondrocytes and longitudinal bone growth: the development of tibial dyschondroplasia

Growth plate cartilage is central to the process of bone elongation. Chondrocytes originating within the resting zone of the growth plate proceed through a series of intermediate phenotypes: proliferating, prehypertrophic and hypertrophic, before reaching a terminally differentiated state. Disruption of this chondrocyte maturational sequence causes many skeletal abnormalities in poultry such as tibial dyschondroplasia (TD), which is a common cause of deformity and lameness in the broiler chicken. Cell and matrix components of the growth plate have been studied in order to determine the cause(s) of the premature arrest of chondrocyte differentiation and retention of prehypertrophic chondrocytes observed in TD. Chondrocyte proliferation proceeds normally in TD, but markers of the differentiated phenotype, local growth factors, and the vitamin D receptor are abnormally expressed within the prehypertrophic chondrocytes above, and within, the lesion. Tibial dyschondroplasia is also associated with a reduced incidence of apoptosis, suggesting that the lesion contains an accumulation of immature cells that have outlived their normal life span. Immunolocalization studies of matrix components suggest an abnormal distribution within the TD growth plate that is consistent with a failure of the chondrocytes to fully hypertrophy. In addition, the collagen matrix of the TD lesion is highly crosslinked, which may make the formed lesion more impervious to vascular invasion and osteoclastic resorption. Recent studies have applied the techniques of differential display and semiquantitative reverse transcriptase-polymerase chain reaction to RNA obtained from discrete populations of growth plate chondrocytes of different maturational phenotypes. This strategy has allowed us to compare phenotypically identical cell fractions from normal and TD growth plates in an attempt to identify possible candidate genes for TD.

Gene expression and tibial dyschondroplasia

Tibial dyschondroplasia (TD) is a skeletal deformity associated with rapid growth in a number of avian species. The disease is the result of a disruption in the cascade of events that occur in the epiphyseal growth plate. Whereas the incidence of TD is susceptible to genetic selection, no specific genetic defect has been identified. Although there are extensive data describing the morphological and biochemical characteristics of the lesion, the mechanism of lesion formation is unknown. However, naturally occurring or induced genetic mutations in other species can provide important clues to possible mechanisms responsible for lesion development. Disruption of normal chondrocyte differentiation by constitutive activation of the parathyroid hormone/parathyroid hormone-related peptide (PTH/PTHrP) receptor, inactivation of the fibroblast growth factor receptor-3 (FGFR-3) receptor, and blocking vascular endothelial growth factor (VEGF) signaling all result in lesions that resemble TD. Impairment of vascular penetration due to the ablation of matrix metalloproteinase-9 (MMP-9) or tartrate-resistant acid phosphatase (TRAP) activity also results in similar cartilage abnormalities. We have integrated these observations with our current knowledge of TD to describe a hypothesis for the sequence of events responsible for the development of tibial dyschondroplastic lesions.

Expression patterns of chondrocyte genes cloned by differential display in tibial dyschondroplasia

Tibial dyschondroplasia (TD) appears to involve a failure of the growth plate chondrocytes within growing long bones to differentiate fully to the hypertrophic stage, resulting in a mass of prehypertrophic chondrocytes which form the avascular TD lesion. Many biochemical and molecular markers of chondrocyte hypertrophy are absent from the lesion, or show reduced expression, but the cause of the disorder remains to be identified. As differentiation to the hypertrophic state is impaired in TD, we hypothesised that chondrocyte genes that are differentially expressed in the growth plate should show altered expression in TD. Using differential display, four genes, B-cadherin, EF2, HT7 and Ex-FABP were cloned from chondrocytes stimulated to differentiate to the hypertrophic stage in vitro, and their differential expression confirmed in vivo. Using semi-quantitative RT-PCR, the expression patterns of these genes were compared in chondrocytes from normal and TD growth plates. Surprisingly, none of these genes showed the pattern of expression that might be expected in TD lesion chondrocytes, and two of them, B-cadherin and Ex-FABP, were upregulated in the lesion. This indicates that the TD phenotype does not merely reflect the absence of hypertrophic marker genes, but may be influenced by more complex developmental mechanisms/defects than previously thought.

Parathyroid receptor gene expression by epiphyseal growth plates in rickets and tibial dyschondroplasia

PTH/PTHrP receptor gene expression was evaluated in situ in avian epiphyseal growth plates taken from normal, rachitic and tibial dyschondroplasia (TD) afflicted chicks induced by thiram or by genetic selection. In the normal growth plates, PTH/PTHrP receptor gene expression was localized to the maturation zone as demonstrated by the expression of collagen type II (col II), osteopontin (OPN) genes and alkaline phosphatase activity (AP). In TD, either induced by thiram or by genetic selection, normal levels of PTH/PTHrP receptor gene expression were observed up to 21 days post-hatch. In rickets, on the other hand, no PTH/PTHrP receptor gene expression was observed in the growth plate from day 8 of a vitamin D-deficient diet. In cultured chondrocytes, PTH caused time-dependent down-regulation of its own receptor. These results suggest that alterations in the PTH/PTHrP receptor gene expression are associated with rickets but not with TD. The reduction in the PTH/PTHrP receptor gene expression in rickets may be due to the high plasma levels of PTH.