The role of the growth plate in longitudinal bone growth

Prg4-Expressing Chondroprogenitor Cells in the Superficial Zone of Articular Cartilage

Joint-resident chondrogenic precursor cells have become a significant therapeutic option due to the lack of regenerative capacity in articular cartilage. Progenitor cells are located in the superficial zone of the articular cartilage, producing lubricin/Prg4 to decrease friction of cartilage surfaces during joint movement. Prg4-positive progenitors are crucial in maintaining the joint's structure and functionality. The disappearance of progenitor cells leads to changes in articular hyaline cartilage over time, subchondral bone abnormalities, and the formation of ectopic ossification. Genetic labeling cell technology has been the main tool used to characterize Prg4-expressing progenitor cells of articular cartilage in vivo through drug injection at different time points. This technology allows for the determination of the origin of progenitor cells and the tracking of their progeny during joint development and cartilage damage. We endeavored to highlight the currently known information about the Prg4-producing cell population in the joint to underline the significance of the role of these cells in the development of articular cartilage and its homeostasis. This review focuses on superficial progenitors in the joint, how they contribute to postnatal articular cartilage formation, their capacity for regeneration, and the consequences of Prg4 deficiency in these cells. We have accumulated information about the Prg4+ cell population of articular cartilage obtained through various elegantly designed experiments using transgenic technologies to identify potential opportunities for further research.

Resveratrol Synergistically Promotes BMP9-Induced Osteogenic Differentiation of Mesenchymal Stem Cells

Background. Mesenchymal stem cells (MSCs) differentiate into osteocytes, adipocytes, and chondrocytes. Resveratrol and bone morphogenetic protein 9 (BMP9) are known osteogenic induction factors of MSCs, but the effect of both resveratrol and BMP9 on osteogenesis is unknown. Herein, we explored whether resveratrol cooperates with BMP9 to improve osteogenic induction. Methods. The osteogenic induction of resveratrol and BMP9 on C3H10T1/2 cells was evaluated by detecting the staining and activity of the early osteogenic marker alkaline phosphatase (ALP). In addition, the late osteogenic effect was measured by the mRNA and protein levels of osteogenic markers, such as osteopontin (OPN) and osteocalcin (OCN). To assess the bone formation function of resveratrol plus BMP9 in vivo, we transplanted BMP9-infected C3H10T1/2 cells into nude mice followed by intragastric injection of resveratrol. Western blot (WB) analysis was utilized to elucidate the mechanism of resveratrol plus BMP9. Results. Resveratrol not only enhanced osteogenic induction alone but also improved BMP9-induced ALP at 3, 5, and 7 d postinduction. Both the early osteogenic markers (ALP, Runx2, and SP7) and the late osteogenic markers (OPN and OCN) were significantly increased when resveratrol was combined with BMP9. The fetal limb explant culture further verified these results. The in vivo bone formation experiment, which involved transplanting BMP9-overexpressing C3H10T1/2 cells into nude mice, also confirmed that resveratrol synergistically enhanced the BMP9-induced bone formation function. Resveratrol phosphorylated adenosine monophosphate- (AMP-) activated protein kinase (AMPK) and stimulated autophagy, but these effects were abolished by inhibiting AMPK and Beclin1 using an inhibitor or siRNA. Conclusions. Resveratrol combined with BMP9 significantly improves the osteogenic induction of C3H10T1/2 cells by activating AMPK and autophagy.

Differentiation of Induced Pluripotent Stem Cells Into Chondrocytes: Methods and Applications for Disease Modeling and Drug Discovery

Induced pluripotent stem cell (iPSC) technology allows pathomechanistic and therapeutic investigation of human heritable disorders affecting tissue types whose collection from patients is difficult or even impossible. Among them are cartilage diseases. Over the past decade, iPSC-chondrocyte disease models have been shown to exhibit several key aspects of known disease mechanisms. Concurrently, an increasing number of protocols to differentiate iPSCs into chondrocytes have been published, each with its respective (dis)advantages. In this review we provide a comprehensive overview of the different differentiation approaches, the hitherto described iPSC-chondrocyte disease models and mechanistic and/or therapeutic insights that have been derived from their investigation, and the current model limitations. Key lessons are that the most appropriate differentiation approach is dependent upon the cartilage disease under investigation and that further optimization is still required to recapitulate the in vivo cartilage. © 2022 American Society for Bone and Mineral Research (ASBMR).

Growth Hormone and Insulin-Like Growth Factor Dysregulation in Pediatric Chronic Kidney Disease

Poor growth is a common finding in children with chronic kidney disease (CKD) that has been associated with poor long-term outcomes. The etiology of poor growth in this population is multifactorial and includes dysregulation of the growth hormone (GH) and insulin-like growth factor (IGF) axis. In this review, we describe the data on GH resistance or insensitivity and inappropriate levels or reduced bioactivity of IGF proposed as contributing factors of growth impairment in children with CKD. Additionally, we describe the theorized negative effect of metabolic acidosis, another frequent finding in pediatric CKD, on the GH/IGF axis and growth. Last, we present the current and potential therapies for the treatment of short stature in pediatric CKD that target the GH/IGF hormonal axis.

A novel in vitro assay to study chondrocyte-to-osteoblast transdifferentiation

PURPOSE

Endochondral ossification, which involves transdifferentiation of chondrocytes into osteoblasts, is an important process involved in the development and postnatal growth of most vertebrate bones as well as in bone fracture healing. To study the basic molecular mechanisms of this process, a robust and easy-to-use in vitro model is desirable. Therefore, we aimed to develop a standardized in vitro assay for the transdifferentiation of chondrogenic cells towards the osteogenic lineage.

METHODS

Murine chondrogenic ATDC5 cells were differentiated into the chondrogenic lineage for seven days and subsequently differentiated towards the osteogenic direction. Gene expression analysis of pluripotency, as well as chondrogenic and osteogenic markers, cell-matrix staining, and immunofluorescent staining, were performed to assess the differentiation. In addition, the effects of Wnt3a and lipopolysaccharides (LPS) on the transdifferentiation were tested by their addition to the osteogenic differentiation medium.

RESULTS

Following osteogenic differentiation, chondrogenically pe-differentiated cells displayed the expression of pluripotency and osteogenic marker genes as well as alkaline phosphatase activity and a mineralized matrix. Co-expression of Col2a1 and Col1a1 after one day of osteogenic differentiation indicated that osteogenic cells had differentiated from chondrogenic cells. Wnt3a increased and LPS decreased transdifferentiation towards the osteogenic lineage.

CONCLUSION

We successfully established a rapid, standardized in vitro assay for the transdifferentiation of chondrogenic cells into osteogenic cells, which is suitable for testing the effects of different compounds on this cellular process.

Assessing the safety of an epiphyseal plate biopsy in a translational lamb model

The literature demonstrates that obtaining a biopsy of the physis may be beneficial for diagnostic purposes. A small biopsy of the epiphyseal plate may allow for earlier detection of certain conditions and be used to monitor the healing of diseased and/or damaged physes. However, due to the fear of a growth arrest in a growing child, biopsies are not currently performed. In this study, we investigated the effects of a biopsy of the epiphyseal plate in 3-month-old lambs. A total of 4.2 mm biopsy samples were captured in the proximal tibiae and distal femora physes. The lambs were monitored 12- and 24-week post-biopsy. Computed tomography (CT) and micro-CT scans were obtained to determine if any angular deformities occurred, while scanning electron microscope (SEM) and histological analysis were utilized to assess the bone response due to the biopsy. The contralateral limbs served as unaltered controls for direct comparison within each lamb. The data demonstrated no signs of angular deformities following a 4.2 mm biopsy of the physis. Bone growth/elongation was confirmed by CT, SEM, and fluorochrome analyses and indicated that the lambs were in fact immature and still growing at the time of the biopsy. Clinical Significance: This investigation demonstrated that a small biopsy of the epiphyseal plate can be obtained safely without the cause of growth arrest and angular deformities. The ability to precisely diagnose, treat, and/or monitor at-risk children at an earlier timepoint by way of a biopsy sample could be an important advancement in regard to researching diseased and/or damaged physes.

Lactobacillus rhamnosus JYLR-005 Prevents Thiram-Induced Tibial Dyschondroplasia by Enhancing Bone-Related Growth Performance in Chickens

Tibial dyschondroplasia (TD) is a leg disorder caused by the abnormal development of the tibia in fast-growing poultry. Lactobacillus rhamnosus (L. rhamnosus) strains have been reported to have effects on increasing bone growth and improving osteoporosis in animals. However, whether L. rhamnosus JYLR-005 can improve bone growth in TD chickens remains unclear. In this study, we noted that L. rhamnosus JYLR-005 could not reduce the suppression of the production performance of TD broilers (p > 0.05) but had a slight protective effect on the broiler survival rate (χ² = 5.571, p = 0.062). However, for thiram-induced TD broiler chickens, L. rhamnosus JYLR-005 could promote tibia growth by increasing tibia-related parameters, including the tibia weight (day 11, p = 0.040), tibia length (day 15, p = 0.013), and tibia mean diameter (day 15, p = 0.035). Moreover, L. rhamnosus JYLR-005 supplementation improved the normal growth and development of the tibial growth plate by maintaining the morphological structure of the chondrocytes and restored the balance of calcium and phosphorus. Taken together, these findings provide a proof of principle that L. rhamnosus JYLR-005 may represent a therapeutic strategy to treat leg disease in chickens.

Amniotic fluid mesenchymal stromal cells from early stages of embryonic development have higher self-renewal potential

Amniotic fluid (AF) is a rich source of mesenchymal stromal cells (MSCs) that have the ability to differentiate into multiple lineages rendering them a promising and powerful tool for regenerative medicine. However, information regarding the differences among AFMSCs derived from different gestational stages is limited. In the present study, AFMSCs derived from 125 pregnant rats at four embryonic day (E) stages (E12, E15, E18, and E21) were isolated and cultured. The primary E15 cells were the smallest in size and the easiest to culture and usually grew in a spherical shape that resembled the growth morphology of embryonic stem cells (ESCs). Once adhered, the E12 and E15 AFMSCs grew faster and could be passaged more than 60 times while still maintaining a continuous proliferative state; however, AFMSCs derived from E18 and E21 could normally be maintained for only 10 passages. To identify the possible reasons for this difference, RT-qPCR was used to examine several genes associated with self-renewal ability and cell origin. The Sox2 expression levels indicated that AFMSCs from E12 and E15 possessed stronger self-renewal capability. The K19, Col2A1, FGF5, AFP, and SPC expression levels indicated there were mixed-population cells co-existing in the AFMSC culture. In conclusion, E15 cells were easier to culture than E12 cells, could be passaged more often, and had a higher Sox2 expression than E18 or E21 cells. The E15-derived AFMSCs had higher viability and proliferative capacity than cells from the later stages. Therefore, AF cells from the early stages could be a good choice for exploring potential treatments involving AFMSCs.

Warmth Prevents Bone Loss Through the Gut Microbiota

Osteoporosis is the most prevalent metabolic bone disease, characterized by low bone mass and microarchitectural deterioration. Here, we show that warmth exposure (34°C) protects against ovariectomy-induced bone loss by increasing trabecular bone volume, connectivity density, and thickness, leading to improved biomechanical bone strength in adult female, as well as in young male mice. Transplantation of the warm-adapted microbiota phenocopies the warmth-induced bone effects. Both warmth and warm microbiota transplantation revert the ovariectomy-induced transcriptomics changes of the tibia and increase periosteal bone formation. Combinatorial metagenomics/metabolomics analysis shows that warmth enhances bacterial polyamine biosynthesis, resulting in higher total polyamine levels in vivo. Spermine and spermidine supplementation increases bone strength, while inhibiting polyamine biosynthesis in vivo limits the beneficial warmth effects on the bone. Our data suggest warmth exposure as a potential treatment option for osteoporosis while providing a mechanistic framework for its benefits in bone disease.

NFI-C Is Required for Epiphyseal Chondrocyte Proliferation during Postnatal Cartilage Development

Stringent regulation of the chondrocyte cell cycle is required for endochondral bone formation. During the longitudinal growth of long bones, mesenchymal stem cells condense and differentiate into chondrocytes. Epiphyseal chondrocytes sequentially differentiate to form growth- plate cartilage, which is subsequently replaced with bone. Although the importance of nuclear factor 1C (Nfic) in hard tissue formation has been extensively studied, knowledge regarding its biological roles and molecular mechanisms in this process remains insufficient. Herein, we demonstrated that Nfic deficiency affects femoral growth-plate formation. Chondrocyte proliferation was downregulated and the number of apoptotic cell was increased in the growth plates of Nfic-/- mice. Further, the expression of the cell cycle inhibitor p21 was upregulated in the primary chondrocytes of Nfic-/- mice, whereas that of cyclin D1 was downregulated. Our findings suggest that Nfic may contribute to postnatal chondrocyte proliferation by inhibiting p21 expression and by increasing the stability of cyclin D1 protein.

Radial shock waves prevent growth retardation caused by the clinically used drug vismodegib in ex vivo cultured bones

In childhood medulloblastoma patients, the hedgehog antagonist vismodegib is an effective anti-cancer treatment but unfortunately induces irreversible growth arrests and growth impairment limiting its use in skeletally immature patients. We hypothesized that radial shock wave treatment (rSWT) may protect drug-induced growth impairment owing to its osteogenic effects. Fetal rat metatarsal bones were exposed to vismodegib (day 0–5; 100 nM) and/or rSWT (single session); other bones from day 1 were continuously exposed to a Gli1 antagonist (GANT61; 10 µM) and/or rSWT (single session). Control bones were untreated. The bone length was measured at intervals; histomorphometric analysis and immunostaining for PCNA, Gli1, and Ihh were performed on the sectioned bones. Bones treated with vismodegib showed impaired bone growth, reduced height of the resting-proliferative zone and reduced hypertrophic cell size compared to control. In vismodegib treated bones, a single session of rSWT partially rescued bone growth, increased the growth velocity, hypertrophic cell size, and restored growth plate morphology. Bones exposed to GANT61 showed impaired bone growth and disorganized growth plate while when combined with rSWT these effects were partially prevented. Locally applied rSWT had a chondroprotective effect in rat metatarsal bones and suggest a novel strategy to prevent growth impairment caused by vismodegib.

LPS-induced inflammation disorders bone modeling and remodeling by inhibiting angiogenesis and disordering osteogenesis in chickens

Inflammation plays a negative role in the growth and development of bone. However, the underlining mechanisms of inflammation caused abnormal bone development and even bone disease are still poorly understood, especially in chickens. In this study, we explored the influence of inflammation on bone formation in broilers for the first time by using lipopolysaccharide (LPS) to establish systemic inflammatory models in chickens with tibia as the research object. The measurements of production and tibial parameters showed an inefficient production performance and lower growth rate in LPS group. We also found a large amount of platelets, inflammatory cells in chickens' blood and higher levels of inflammatory factors in serum after LPS injection, meanwhile, increase in thrombus, chondrocyte nucleolysis, and osteoclasts and a reduction in blood vessels were observed in growth plate through histological observation. The qPCR analysis showed that the mRNA expression levels of NF-κB, TLR4, TF, TPO, and its receptor C-MPL enhanced, while VEGFA was inhibited in LPS group. In addition, in OPG/RANKL system, OPG was decreased while RANKL enhanced. It was also observed that the mRNA levels of MMP-9 and its inducing factor CD147 enhanced in LPS group. The western blot results were basically in consistent with mRNA test. Thus, we infer that inflammation can inhibit bone modeling and remodeling by affecting angiogenesis and osteogenesis, and result in negative effect on bone formation furtherly.

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.

The effect of bee pollen on bone biomechanical strength and trabecular bone histomorphometry in tibia of young Japanese quail (Coturnix japonica)

It has been demonstrated in numerous studies that bee pollen supplementation shows numerous positive effects on health. However, its impact on bones is largely unknown. The purpose of this study was to investigate the effect of bee pollen supplementation on the tibia biomechanical properties and bone morphometric measures using Japanese quail as an animal model. The experiment was arranged in a 2x2x2 factorial design, with sex, quail line (meat-type or egg-lying type), and bee pollen inclusion (0 or 10 g/kg of feed) as factors. The quails were one-day-old at the beginning of the experiment, they were euthanized after 42 days. Our study showed for the first time unfavorable effects of bee pollen on bones properties. Bee pollen supplementation negatively affected bone structure, irrespective of quails’ sex or line type. Bone length (P < 0.001), weight (P < 0.01), and mean relative wall thickness (P < 0.01) and mineralization (P < 0.05) were reduced by bee pollen treatment. For female quails, irrespective of line type, the decrease of yield load (P < 0.001), ultimate load (P < 0.01), yield stress (P < 0.001) and ultimate stress (P < 0.05) was noted. Analysis of growth plate in bone metaphysis showed that bee pollen supplementation slowed the process of bone maturation irrespective of sex (P < 0.05). On contrary, dietary bee pollen positively affected bone homeostasis of trabecular bone in bone metaphysis as bone mineral density increased in experimental groups (P < 0.05). In males, this was the result of the increase of trabecular thickness (P < 0.01), in females due to the reduction of trabecular space (P < 0.001). In conclusion, our results demonstrate that bee pollen (1.0%, 10 g/kg of feed) supplementation caused significant negative effects on the mechanical endurance of the tibia of quails, while showed beneficial effects on trabecular bone histomorphometry.

Identification and expression analysis of microRNAs in tibial growth plate of chicken through thiram toxicity

Thiram is a widely known tibial dyschondroplasia (TD) inducer. TD, a common metabolic cartilage disease, presents in rapidly growing poultry birds. There are evidences that miRNAs are involved in diverse aspects of normal skeletal development, but very less is known about the role of miRNAs in TD. Therefore, this study aimed to determine which genes and pathways show differential expression between TD suffered chickens and normal chickens. We collected growth plates from ten-days-old TD chickens and control chickens and performed high-throughput RNA sequencing (RNA-Seq). Afterwards, target prediction, GO annotation and KEGG pathway analysis were carried out to understand the role of DEMs (differentially expressed microRNAs). We obtained 96,884,760 and 94,574,290 clean reads and identified 17 significant DEMs between the TD and control groups. Functional enrichment analysis of DEMs indicated that the putative targets of miRNAs were remarkably enriched in bone-related pathways, such as Notch, MAPK and Autophagy. Overall, this study provides detailed understanding about the pathogenesis of thiram induced TD and new insights towards the molecular mechanism of miRNAs.

Androgens and Androgen Receptor Actions on Bone Health and Disease: From Androgen Deficiency to Androgen Therapy

Androgens are not only essential for bone development but for the maintenance of bone mass. Therefore, conditions with androgen deficiency, such as male hypogonadism, androgen-insensitive syndromes, and prostate cancer with androgen deprivation therapy are strongly associated with bone loss and increased fracture risk. Here we summarize the skeletal effects of androgens—androgen receptors (AR) actions based on in vitro and in vivo studies from animals and humans, and discuss bone loss due to androgens/AR deficiency to clarify the molecular basis for the anabolic action of androgens and AR in bone homeostasis and unravel the functions of androgen/AR signaling in healthy and disease states. Moreover, we provide evidence for the skeletal benefits of androgen therapy and elucidate why androgens are more beneficial than male sexual hormones, highlighting their therapeutic potential as osteoanabolic steroids in improving bone fracture repair. Finally, the application of selective androgen receptor modulators may provide new approaches for the treatment of osteoporosis and fractures as well as building stronger bones in diseases dependent on androgens/AR status.

Chlorogenic Acid Alleviates Thiram-Induced Tibial Dyschondroplasia by Modulating Caspases, BECN1 Expression and ECM Degradation

Chlorogenic acid (CGA) is a widely applied traditional Chinese medicine ingredient which can be used for the treatment of osteoporosis. In this experiment, we investigated the potential therapeutic effect of chlorogenic acid on thiram-induced tibial dyschondroplasia (TD) and explored the underlying mechanisms that have been rarely mentioned by others yet. Performance indicator analysis and tibial parameter analysis showed that CGA exhibited a definite positive effect on thiram-induced TD chickens. In order to further explore the mechanisms underlying the positive actions of CGA, apoptotic, autophagic genes and MMPs involved in matrix mineralization of growth plate were evaluated in this study. The results showed that CGA decreased the expression of pro-apoptotic genes caspases-3 and caspases-9, leading to the reduction of apoptotic cells accumulated in growth plate. In addition, CGA also increased the level of BECN1, an important gene involved in autophagy, which benefits the survival of abnormal cells. Furthermore, CGA also increased the expression of MMP-9, MMP-10, and MMP-13, which can directly affect the ossification of bones. Altogether, these results demonstrate that CGA possesses a positive therapeutic effect on thiram-induced TD via modulating the expression of caspases and BECN1 and regulating the degradation of ECM (extracellular matrix).

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.

Exogenous Vitamin D signaling alters skeletal patterning, differentiation, and tissue integration during limb regeneration in the axolotl

Urodele amphibians such as the axolotl regenerate complete limbs as adults, and understanding how the "blueprint", or pattern, of the regenerate is established and manipulated are areas of intense interest. Nutrient signaling plays an important role in pattern formation during regeneration. Retinoic acid signaling is the most characterized pathway during this process. Exogenous retinoic acid (RA) reprograms the pattern information in regenerating cells to a more posterior, ventral, and proximal identity. Vitamin D signaling shares several molecular similarities with RA and has been shown to alter pattern formation during zebrafish pectoral fin regeneration. To determine if exogenous Vitamin D signaling is capable of reprograming pattern in the axolotl limb blastema, we treated regenerating limbs with a potent Vitamin D agonist. Under the studied conditions, exogenous Vitamin D did not act in a manner similar to RA and failed to proximalize the pattern of the resulting regenerates. The Vitamin D treatment did result in several skeletal defects during regeneration, including carpal fusions along the A/P axis; failure to integrate the newly regenerated tissue with the existing tissue, formation of ectopic nodules of cartilage at the site of amputation, and altered bone morphology in uninjured skeletal tissue.

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.

INVERSE RELATIONSHIP BETWEEN FUNCTIONAL MATURITY AND EXPONENTIAL GROWTH RATE OF AVIAN SKELETAL MUSCLE: A CONSTRAINT ON EVOLUTIONARY RESPONSE

In this study, we investigate whether a tissue-level constraint can explain the general inverse relationship between growth rate and precocity of development in birds. On the whole, altricial (dependent) chicks grow three to four times faster than the less dependent, more able chicks of precocial species of similar adult mass. We suggest that an antagonism between growth and acquisition of mature function in skeletal muscle constrains postnatal growth and development in most species of birds. Altricial species, represented by European starlings in this study, hatch with skeletal muscle having low capacity for generating force but grow rapidly. Conversely, precocial species (northern bobwhite quail and Japanese quail), hatch with relatively mature skeletal muscle, especially in their legs, but grow more slowly. As development proceeds in all species, exponential growth rates decrease as muscles acquire adult levels of function. Among four variables associated with muscle function, exponential growth rate (EGR) was negatively correlated with pyruvate kinase activity (glycolysis), potassium concentration (electrical potential), and dry weight fraction (contractile proteins) in both pectoral and leg muscles but not with citrate synthase activity (aerobic metabolism) in either set of muscles. For pectoral muscle, these variables accounted for 87% of the total variation in EGR in all three species combined despite a twofold difference in growth rates between the starling and quail. EGRs of leg muscle (51% of variation accounted for) were less than predicted by the pectoral-muscle equation in quail during the early part of the postnatal period and in starlings during the late postnatal period. This result would not contradict a growth rate/maturity constraint hypothesis if EGRs were down-regulated for allometric or other considerations.

Effects of excess maternal thyroxin on the bones of rat offspring from birth to the post-weaning period

Objective To evaluate, in rat offspring, bone changes induced by excess maternal thyroxin during pregnancy and lactation, and to assess the reversibility of these changes after weaning. Material and methods Twenty Wistar rats were distributed in two groups, hyperthyroid and control, that were treated daily with L-thyroxin (50 mcg/animal) and placebo, respectively. The treatment was initiated seven days before mating and continued throughout pregnancy and lactation. From every female of each of the two groups, two offspring were euthanized after birth, two at 21 days of age (weaning), and two at 42 days of age (21 days after weaning). In newborns, the length of pelvic and thoracic limbs were measured, and in the other animals, the length and width of the femur and humerus were measured. Bones were dissected, decalcified, embedded in paraffin, and analyzed histomorphometrically. Results Excess maternal thyroxin significantly reduced the length of the pelvic limb in neonates. In 21-day-old individuals, excess maternal thyroxine reduced the length and the width of the femur and the humerus. It also increased thickness of the epiphyseal plate and the percentage of trabecular bone tissue. In 42-day-old individuals, there were no significant differences between groups in relation to the parameters evaluated in the previous periods. Conclusion Excess maternal thyroxine reduced growth in suckling rats both at birth and at weaning, and it also increased the percentage of trabecular bone tissue in 21-day-old animals. These changes, however, were reversible at 42 days, i.e., 21 days after weaning. Arch Endocrinol Metab. 2016;60(2):130-7.

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.

Dendritic polyglycerol anions for the selective targeting of native and inflamed articular cartilage

Dye-conjugated polyanions show high affinities toward native and inflamed cartilage dependent on the anionic moiety and the condition of the tissue.

Bone mineralization pathways during the rapid growth of embryonic chicken long bones

The uptake and transport of ions from the environment to the site of bone formation is only partially understood and, for the most part, based on disparate observations in different animals. Here we study different aspects of the biomineralization pathways in one system, the rapidly forming long bones of the chicken embryo. We mainly used cryo-fixation and cryo-electron imaging to preserve the often unstable mineral phases in the tissues. We show the presence of surprisingly large amounts of mineral particles located inside membrane-delineated vesicles in the bone forming tissue between the blood vessels and the forming bone surface. Some of these particles are also located inside mitochondrial networks. The surfaces of the forming bones in the extracellular space contain abundant aggregates of amorphous calcium phosphate particles, but these are not enveloped by vesicle membranes. In the bone resorbing region, osteoclasts also contain many particles in both mitochondrial networks and within vesicles. Some of these particles are present also between cells. These observations, together with the previously reported observation that CaP mineral particles inside membranes are present in blood vessels, leads us to the conclusion that important components of the bone mineralization pathways in rapidly forming chicken bone are dense phase mineral particles bound within membranes. It remains to be determined whether these mineral particles are transported to the site of bone formation in the solid state, fluid state or dissolve and re-precipitate.

Transport of membrane-bound mineral particles in blood vessels during chicken embryonic bone development

During bone formation in embryos, large amounts of calcium and phosphate are taken up and transported to the site where solid mineral is first deposited. The initial mineral forms in vesicles inside osteoblasts and is deposited as a highly disordered calcium phosphate phase. The mineral is then translocated to the extracellular space where it penetrates the collagen matrix and crystallizes. To date little is known about the transport mechanisms of calcium and phosphate in the vascular system, especially when high transport rates are needed and the concentrations of these ions in the blood serum may exceed the solubility product of the mineral phase. Here we used a rapidly growing biological model, the chick embryo, to study the bone mineralization pathway taking advantage of the fact that large amounts of bone mineral constituents are transported. Cryo scanning electron microscopy together with cryo energy dispersive X-ray spectroscopy and focused-ion beam imaging in the serial surface view mode surprisingly reveal the presence of abundant vesicles containing small mineral particles in the lumen of the blood vessels. Morphologically similar vesicles are also found in the cells associated with bone formation. This observation directly implicates the vascular system in solid mineral distribution, as opposed to the transport of ions in solution. Mineral particle transport inside vesicles implies that far larger amounts of the bone mineral constituents can be transported through the vasculature, without the danger of ectopic precipitation. This introduces a new stage into the bone mineral formation pathway, with the first mineral being formed far from the bone itself.

Super pharmacological levels of calcitriol (1,25-(OH)2D3) inhibits mineral deposition and decreases cell proliferation in a strain dependent manner in chicken mesenchymal stem cells undergoing osteogenic differentiation in vitro

The biologically active form of vitamin D₃, calcitriol (1,25-(OH)₂D₃), plays a key role in mineral homeostasis and bone formation and dietary vitamin D₃ deficiency is a major cause of bone disorders in poultry. Supplementary dietary cholecalciferol (25-hydroxyvitamin D, 25-OH), the precursor of calcitriol, is commonly employed to combat this problem; however, dosage must be carefully determined as excess dietary vitamin D can cause toxicity resulting in a decrease in bone calcification, hypercalcinemia and renal failure. Despite much research on the therapeutic administration of dietary vitamin D in humans, the relative sensitivity of avian species to exogenous vitamin D has not been well defined. In order to determine the effects of exogenous 1,25-(OH)₂D₃ during avian osteogenesis, chicken bone marrow-derived mesenchymal stem cells (BM-MSCs) were exposed to varying doses of 1,25-(OH)₂D₃ during in vitro osteogenic differentiation and examined for markers of early proliferation and osteogenic induction. Similar to humans and other mammals, poultry BM-MSCs were found to be highly sensitive to exogenous 1,25-(OH)₂D₃ with super pharmacological levels exerting significant inhibition of mineralization and loss of cell proliferation in vitro. Strain related differences were apparent, with BM-MCSs derived from layers strains showing a higher level of sensitivity to 1,25-(OH)₂D₃ than those from broilers. These data suggest that understanding species and strain specific sensitivities to 1,25-(OH)₂D₃ is important for optimizing bone health in the poultry industry and that use of avian BM-MSCs are a useful tool for examining underlying effects of genetic variation in poultry.

Mechanical activation of mammalian target of rapamycin pathway is required for cartilage development

Mechanical stress regulates development by modulating cell signaling and gene expression. However, the cytoplasmic components mediating mechanotransduction remain unclear. In this study, elimination of muscle contraction during chicken embryonic development resulted in a reduction in the activity of mammalian target of rapamycin (mTOR) in the cartilaginous growth plate. Inhibition of mTOR activity led to significant inhibition of chondrocyte proliferation, cartilage tissue growth, and expression of chondrogenic genes, including Indian hedgehog (Ihh), a critical mediator of mechanotransduction. Conversely, cyclic loading (1 Hz, 5% matrix deformation) of embryonic chicken growth plate chondrocytes in 3-dimensional (3D) collagen scaffolding induced sustained activation of mTOR. Mechanical activation of mTOR occurred in serum-free medium, indicating that it is independent of growth factor or nutrients. Treatment of chondrocytes with Rapa abolished mechanical activation of cell proliferation and Ihh gene expression. Cyclic loading of chondroprogenitor cells deficient in SH2-containing protein tyrosine phosphatase 2 (Shp2) further enhanced mechanical activation of mTOR, cell proliferation, and chondrogenic gene expression. This result suggests that Shp2 is an antagonist of mechanotransduction through inhibition of mTOR activity. Our data demonstrate that mechanical activation of mTOR is necessary for cell proliferation, chondrogenesis, and cartilage growth during bone development, and that mTOR is an essential mechanotransduction component modulated by Shp2 in the cytoplasm.

Effect of neutering and breed on femoral and tibial physeal closure times in male and female domestic cats

The timing of physeal closure is dependent upon many factors, including gonadal steroids, and previous studies have shown that early neutering delays physeal closure. Pelvic and femoral radiographs of 808 cats were analysed and physes at the greater trochanter, proximal femur, distal femur and proximal tibia were recorded as being open or closed. Date of birth, gender, neuter status and breed of cases were recorded. Each physis was analysed individually at a specific age. The number of male entire (ME), male neutered (MN), female entire (FE), female neutered (FN), pedigree and non-pedigree cases at each of these ages was recorded. The number of cases that were open or closed at each stated age were compared between the neutered and entire, the female and male, and the pedigree and non-pedigree groups using a Fischer's exact test, with P <0.05 being considered significant. Seven hundred and eighty-three radiographs were included: 359 MN, 95 ME, 237 FN and 92 FE. Ninety-six cats were pedigree and 687 were non-pedigree. A statistically significant effect was shown with physes closing later in MN than in ME cats for the greater trochanter (P = 0.0037), distal femur (P = 0.0205) and tibial tuberosity (P = 0.0003). No effect was shown for the proximal tibial or proximal femoral physes, nor for any physis when comparing FE with FN cats. No statistically significant effect of breed or sex was noted. Physeal closure will occur later in MN cats than in ME cats for the greater trochanteric, distal femoral and tibial tuberosity physes, and the potential clinical consequences of this should be evaluated further.

Bone circulatory disturbances in the development of spontaneous bacterial chondronecrosis with osteomyelitis: a translational model for the pathogenesis of femoral head necrosis

This review provides a comprehensive overview of the vascularization of the avian growth plate and its subsequent role in the pathogenesis of bacterial chondronecrosis with osteomyelitis (BCO, femoral head necrosis). BCO sporadically causes high incidences of lameness in rapidly growing broiler (meat-type) chickens. BCO is believed to be initiated by micro-trauma to poorly mineralized columns of cartilage cells in the proximal growth plates of the leg bones, followed by colonization by hematogenously distributed opportunistic bacteria. Inadequate blood flow to the growth plate, vascular occlusion, and structural limitations of the microvasculature all have been implicated in the pathogenesis of BCO. Treatment strategies have been difficult to investigate because under normal conditions the incidence of BCO typically is low and sporadic. Rearing broilers on wire flooring triggers the spontaneous development of high incidences of lameness attributable to pathognomonic BCO lesions. Wire flooring imposes persistent footing instability and is thought to accelerate the development of BCO by amplifying the torque and shear stress imposed on susceptible leg joints. Wire flooring per se also constitutes a significant chronic stressor that promotes bacterial proliferation attributed to stress-mediated immunosuppression. Indeed, dexamethasone-mediated immunosuppression causes broilers to develop lameness primarily associated with avascular necrosis and BCO. Prophylactic probiotic administration consistently reduces the incidence of lameness in broilers reared on wire flooring, presumably by reducing bacterial translocation from the gastrointestinal tract that likely contributes to hematogenous infection of the leg bones. The pathogenesis of BCO in broilers is directly relevant to osteomyelitis in growing children, as well as to avascular femoral head necrosis in adults. Our new model for reliably triggering spontaneous osteomyelitis in large numbers of animals represents an important opportunity to conduct translational research focused on developing effective prophylactic and therapeutic treatments.

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.

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.

Endochondral ossification process of the turkey (Meleagris gallopavo) during embryonic and juvenile development

The long bones of the developing skeleton arise from the process of endochondral ossification, which begins during the embryonic stages and resumes later in the growth plates located at the extremities of the long bones. This process includes commitment of cells to the chondrocytic lineage and further differentiation into hypertrophic chondrocytes, which subsequently undergo apoptosis and are replaced by osteoblasts laying down the trabecular bone. In this study we characterize, for the first time, the endochondral bone development of the turkey during embryonic and juvenile stages. Turkey tibias were collected on embryonic d 11, 14, and 18; and at 3 and 7 d posthatching, alcian blue and Von Kossa staining, alkaline phosphatase activity, and in situ expression of collagen types II and X were studied in these samples. We showed that the principles of bone development in the turkey follow the known vertebrate pattern, and that the initiation of ossification is related to the perichondrium and compact bone. These results increase the knowledge about this process in the turkey, which is an important animal in the agricultural industries.

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.

FGF upregulates osteopontin in epiphyseal growth plate chondrocytes: Implications for endochondral ossification

Fibroblast growth factor receptor 3 (FGFR3) signaling pathways are essential for normal longitudinal bone growth. Mutations in this receptor lead to various human growth disorders, including Achondroplasia, disproportionately short-limbed dwarfism, characterized by narrowing of the hypertrophic region of the epiphyseal growth plates. Here we find that FGF9, a preferred ligand for FGFR3 rapidly induces the upregulation and secretion of the matrix resident phosphoprotein, osteopontin (OPN) in cultured chicken chondrocytes. This effect was observed as early as two hours post stimulation and at FGF9 concentrations as low as 1.25 ng/ml at both mRNA and protein levels. OPN expression is known to be associated with chondrocyte and osteoblast differentiation and osteoclast activation. Unexpectedly, FGF9 induced OPN was accompanied by inhibition of differentiation and increased proliferation of the treated chondrocytes. Moreover, FGF9 stimulated OPN expression irrespective of the differentiation stage of the cells or culture conditions. In situ hybridization analysis of epiphyseal growth plates from chicken or mice homozygous for the Achondroplasia, G369C/mFGFR3 mutation demonstrated co-localization of OPN expression and osteoclast activity, as evidenced by tartarate resistant acid phosphatase positive cells in the osteochondral junction. We propose that FGF signaling directly activates OPN expression independent of chondrocytes differentiation. This may enhance the recruitment and activation of osteoclasts, and increase in cartilage resorption and remodeling in the chondro-osseus border.

Expression of chicken 75-kDa gelatinase B-like enzyme in perivascular chondrocytes suggests its role in vascularization of the growth plate

A newly cloned avian 75-kDa gelatinase B-like enzyme is expressed by the cells surrounding the blood vessels of the growth plate and upregulated by angiogenic substances in cultured chondrocytes. Despite its low homology to mammalian gelatinase-B, the avian 75-kDa seems to function similarly in the context of endochondral bone formation.

INTRODUCTION

Gelatinase B/metalloproteinase (MMP)-9, a zinc-dependent protease of the MMP family, is a key regulator in the final step of endochondral ossification. Recently an avian 75-kDa gelatinase B-like enzyme that shows low sequence similarity to the mammalian enzyme (59% on the protein level) was cloned and characterized. However, its expression pattern in the chicken growth plate and its role in bone formation have not, so far, been examined.

RESULTS

Based on the published sequence, we cloned a 700-bp fragment from cDNA of the chicken growth plate and studied its expression pattern in primary chondrocytes. Because the basal expression level of gelatinase B was almost undetectable, we induced its expression by different culturing conditions, the most dramatic induction achieved by treatment with retinoic acid, which is known as an inducer of vascular invasion in the epiphyseal plates. The gelatinolitic activity, checked by zymography, detected bands corresponding to the gelatinase A and B as well as a new high-molecular weight band of approximately 200 kDa. We further studied the expression pattern of gelatinase B by in situ hybridization. The gelatinase B was expressed by the cells surrounding the blood vessels penetrating the growth plate and by chondrocytes located in the front of these vascular invasions in the borders between the bone and the cartilage, resembling the expression of mouse gelatinase B in the growth plate. The induction of rickets by a vitamin D-deficient diet reduced the expression levels of gelatinase B in the growth plate of 12-day-old chickens but did not affect the expression of gelatinase A mRNA.

CONCLUSION

The chicken growth plate has a distinctly different structure from the mammalian one: it is much wider, it contains more cells in each zone, and the blood vessels penetrate deeper into the hypertrophic zone. Nevertheless, the upregulation of the avian 75-kDa gelatinase B-like enzyme by vitamins A and D, coupled with its perivascular expression pattern in the growth plate, implies a similar role for the mammalian and avian genes in bone formation.

Maternal dietary lipids alter bone chemical composition, mechanical properties, and histological characteristics of progeny of Japanese quail

This study evaluated the effects of maternal dietary lipids on chemical components and mechanical and histological properties of tibia in progeny of Japanese quail fed different dietary lipids. Laying hens were fed a basal diet containing either soybean oil (SBO), hydrogenated soybean oil (HSBO), chicken fat (CF), or menhaden fish oil (FO) at 50 g/kg of the diet. The various maternal dietary lipid treatments did not affect growth of progeny at any developmental stage. There were no differences in tibial length, diameter, or collagen content. Tibial percentage ash was significantly higher in newly hatched progeny from hens fed the FO and HSBO diets. The levels of tibial deoxypyridinoline and total pyridinium crosslinks were higher in the FO and HSBO groups at hatch. At 7 d of age, the tibial deoxypyridinoline links remained higher in the FO group compared to the CF and SBO groups. Likewise, progeny from hens consuming the FO or HSBO diet had higher tibial shear force and stiffness at 7 and 14 d of age. There were no pronounced differences in tibial fracture energy and deflection among treatments. Maternal FO or HSBO enlarged the cartilaginous proliferative and hypertrophic zones of the tibial proximal end in newly hatched quail, which was accompanied by a thicker cortical bone in the diaphysis. However, the width of the hypertrophic zones tended to be smaller in these two groups coupled with improvement in trabecular density and cortical thickness in the proximal end and cortical density in the diaphysis at 3 wk of age. These results suggest that maternal dietary lipids altered bone development by influencing organic matrix quality and mineralization in embryos.

Toxina T-2 e alterações do crescimento endocondral em frangos de corte

Foi testada a habilidade da toxina T-2, produzida por Fusarium sporotrichioides Sherb e veiculada por milho experimentalmente contaminado, em induzir alterações da placa epifisária proximal do tibiotarso de frangos de corte. Pintos de um dia, todos machos e da linhagem Hubbard, foram alimentados com ração básica a base de milho e soja, na qual todo o milho foi substituído por milho contaminado, contendo exclusivamente T-2 na quantidade de 2,64mg/kg. Um outro grupo alimentado com milho não contaminado serviu como testemunha e ambos foram observados por três períodos (7, 14 e 21 dias). Independente do período e da quantidade de T-2 ingerida (0,3 a 1,9 mg/kg), o tibiotarso dos animais tratados mostrou maturação e diferenciação defectivas de condrócitos, lesões vasculares e penetração vascular da cartilagem, todas similares às da discondroplasia tibial. Conclui-se que a toxina T-2 oriunda de Fusarium sporotrichioides Sherb é capaz de induzir lesões básicas e iniciais da discondroplasia tibial em frangos de corte.

Microtubules are potential regulators of growth-plate chondrocyte differentiation and hypertrophy

Terminal differentiation of growth-plate chondrocytes is accompanied by the acquisition of a spherical morphology and a large increase in cell volume. These changes are likely to be associated with rearrangement of the cytoskeleton, but little information on this aspect of chondrocyte hypertrophy is available. We report a role for microtubules in the control of chondrocyte maturation and hypertrophy. Chick growth-plate chondrocytes were fractionated into five maturationally distinct populations by Percoll density gradient centrifugation, and agarose gel differential display analysis was performed. We identified a 1200 bp cDNA fragment derived from a transcript that was most highly expressed in the hypertrophic chondrocytes. After cloning and sequencing, FASTA and BLAST analysis revealed 100% identity to chick beta7-tubulin. Differential expression was confirmed in a reverse transcription-polymerase chain reaction (RT-PCR) assay using specific primers for a 343 bp fragment from the 3' untranslated region of beta7-tubulin. Beta7-tubulin was upregulated three-fold in fully hypertrophic chondrocytes compared with the other four fractions, which all had similar levels of expression. Immunocytochemical localization of beta-tubulin in chick growth-plate sections demonstrated little staining in the chondrocytes of the proliferating zone, but intense cytoplasmic staining was present in the large hypertrophic chondrocytes. In cell culture studies, the addition of colchicine (10(-6) mol/L) resulted in a higher rate of [3H]-thymidine uptake (36.0%; p < 0.001), but lower amounts of alkaline phosphatase activity (69.1%; p < 0.001), collagen (49.1%; p < 0.01), and glycosaminoglycan (43.3%; p < 0.01) accumulation within the cell-matrix layer. Further evidence for the involvement of microtubules in chondrocyte differentiation and hypertrophy was obtained by morphological assessment of colchicine-treated growth-plate explant cultures. A partial failure of chondrocyte hypertrophy was observed, although collagen type X immunoreactivity was noted within the interstitial matrix. Further studies are required to identify the exact role of microtubules in chondrocyte hypertrophy, but the results presented here suggest that upregulation of beta-tubulin may be required for increased microtubule synthesis during changes in cell size during the hypertrophic process. In addition, as cell-matrix interactions are required for chondrocyte maturation, microtubules may promote the differentiated phenotype as a result of their role in Golgi-mediated secretion of matrix proteins.

Expression of growth factors in chicken growth plate with special reference to tibial dyschondroplasia

Immunoreactive growth factors were identified in chick embryonic cartilage and bone, and in the growth plate of normal tibiotarsi and tibiotarsi affected with tibial dyschondroplasia (TD). A specific pattern of temporal and spatial expression was observed for each growth factor. Transforming growth factor beta and alpha (TGF beta and TGF alpha) and epidermal growth factor (EGF) were briefly expressed in chondrocytes of early chick embryos. Immunolabelling for TGF beta then gradually shifted into cartilaginous matrix and was not observed in cytoplasm of hypertrophic chondrocytes until the late embryonic and post-hatch stages. The distribution and intensity of TGF beta labelling was the same in chondrocytes of the TD and normal growth plate. Insulin-like growth factor I (IGF-I) labelling persisted from the early embryonic stage to the end of the mid-stage and then disappeared from chondrocytes. IGF-I appeared again in chondrocytes 1-2 days before hatching. After hatching, the labelling intensified in prehypertrophic and hypertrophic chondrocytes. TD lesions displayed IGF-I in the distal region, mainly in chondrocytes around small blood vessels. EGF reappeared in proliferative and hypertrophic chondrocytes of the mid-embryonic stage. By day 18 after hatching, EGF was present mainly in prehypertrophic and hypertrophic chondrocytes. EGF was demonstrated only in distal proliferative and early prehypertrophic chondrocytes of the dyschondroplastic growth plate. TGF alpha was identified in hypertrophic chondrocytes adjacent to the periosteum and in the distal tip of the mid-embryonic growth plate. With progressing ossification, TGF alpha labeling intensified in the embryonic hypertrophic chondrocytes. In the TD growth plate at day 18 after hatching, TGF alpha expression was limited to 1-3 concentric layers of chondrocytes surrounding blood vessels.

The effect of prepuberal and postpuberal gonadectomy on radial physeal closure in male and female domestic cats

Male (n = 6/group) and female (n = 6/group) kittens were gonadectomized at 7 weeks (prepuberally) or 7 months of age (postpuberally), or left intact. Lateral radiographic projections of the right forelimb were made from 4 months of age until the distal radial physis was closed, or 24 months of age. In males, distal radial physeal closure was delayed in both groups of gonadectomized animals, compared to intact males (p < 0.01). In females, proximal radial physeal closure was significantly delayed in prepuberally gonadectomized animals (p = 0.02), and distal radial physeal closure was significantly delayed in both groups of gonadectomized animals, compared to intact animals (p < 0.01). Final radial length (females p < 0.01, males p = 0.01), and age and radial length at time of the growth plateau (p < 0.01) were significantly increased in all gonadectomized animals. Age at gonadectomy had no effect on age and radial length at time of the growth plateau. No puberal growth spurt was observed in any of the cats.

A study of the chemical composition of the proximal tibial articular cartilage and growth plate of broiler chickens

This study was undertaken to analyze the chemical composition of the proximal tibial articular cartilage and growth plate from 1-mo-old broiler chickens. The composition was different between the two types of cartilage (weight-bearing tissue and the tissue of growth center). The dry matter and collagen contents and the ratio of keratan sulfate to sulfated glycosaminoglycan (GAG) were higher, and the total GAG uronic acid, chondroitin sulfate, hyaluronic acid, and sialic acid contents were lower in the articular cartilage hyaluronic acid, and sialic acid contents were lower in the articular cartilage than in the growth plate. Chondroitin sulfate was the major GAG, accounting for an average 96% of total GAG in both tissues. The size of chondroitin sulfate examined by gel chromatography was similar between the two tissues. The articular cartilage contained a small amount of dermatan sulfate (approximately 1% of total GAG) with low iduronic acid content (38% of total uronic acid). There was no appreciable amount of dermatan sulfate found in the growth plate. Proteoglycans were extracted from these tissues with 4 M-guanidine hydrochloride and separated by ion-exchange chromatography and gel chromatography. The uronic acid to protein ratio in the proteoglycan fraction was similar (average 2.6) between the two tissues. However, gel electrophoresis of chondroitinase-ABC digests of proteoglycan fraction showed differences in their composition.