Increased sclerostin associated with stress fracture of the third metacarpal bone in the Thoroughbred Racehorse

Abstract Objectives: The exact aetiopathogenesis of microdamage induced long bone fractures remains unknown. These fractures are likely the result of inadequate bone remodeling in response to damage. This study aims to identifiesy an association of osteocyte apoptosis, the presence of osteocytic osteolysis and any alterations in sclerostin expression with fracture of the third metacarpal bone of (Mc-III) thoroughbred (TB) racehorses. Methods: 30 Mc-III bones were obtained; 10 from bones fractured during racing, 10 from the contralateral limb and 10 from control horses. Each Mc- III bone was divided into fracture site, condyle, condylar groove and sagittal ridge. Microcracks and diffuse microdamage were quantified. Apoptotic osteocytes were measured using TUNEL staining. Cathepsin K, matrix metalloproteinase -13 (MMP-13), HtrA1 and sclerostin expression was analysed. of apoptotic cells between contralateral limb and unraced control, however, there were significantly less apoptotic cells in fractured samples (p<0.02). Immunohistochemistry showed that in the deep zones of the fractured samples sclerostin expression was significantly higher (p<0.03) of the total number of osteocytes. No increase in cathepsin K, MMP-13 or HtrA1 was present

Healing of Osteochondral Defects via Endochondral Ossification in an Ovine Model.

OBJECTIVE: The objective of this study was to describe the mechanism of healing of osteochondral defects of the distal femur in the sheep, a commonly used translational model. Information on the healing mechanism be useful to inform the design of tissue engineering devices for joint surface defect repair. DESIGN: A retrospective study was conducted examining 7-mm diameter osteochondral defects made in the distal medial femoral condyle of 40 adult female sheep, comprising control animals from 3 separate structures. The healing of the defects was studied at post mortem at up to 26 weeks. RESULTS: Osteochondral defects of the distal femur of the sheep heal through endochondral ossification as evidenced by chondrocyte hypertrophy and type X collagen expression. Neocartilage is first formed adjacent to damaged cartilage and then streams over the damaged underlying bone before filling the defect from the base upward. No intramembranous ossification or isolated mesenchymal stem cell aggregates were detected in the healing tissue. No osseous hypertrophy was detected in the defects. CONCLUSIONS: Osteochondral defects of the medial femoral condyle of the sheep heal via endochondral ossification, with neocartilage first appearing adjacent to damaged cartilage. Unlike the mechanism of healing in fracture repair, neocartilage is eventually formed directly onto damaged bone. There was most variability between animals between 8 and 12 weeks postsurgery. These results should be considered when designing devices to promote defect healing

Ultrasonographic evaluation of the supraspinous ligament in a series of ridden and unridden horses and horses with unrelated back pathology

Abstract Background Injury to the supraspinous ligament (SSL) is reported to cause back pain in the horse. The diagnosis is based on clinical examination and confirmed by ultrasonographic examination. The ultrasonographic appearance of the supraspinous ligament has been well described, but there are few studies that correlate ultrasonographic findings with clinical pain and/or pathology. This preliminary study aims to test the hypothesis that unridden horses (n = 13) have a significantly reduced frequency of occurrence of ultrasonographic changes of the SSL consistent with a diagnosis of desmitis when compared to ridden horses (n = 13) and those with clinical signs of back pain (n = 13). Results The supraspinous ligament of all horses was imaged between T(thoracic)6-T18 and ultrasonographic appearance. There was an average of 2.08 abnormal images per horse from the whole group. The average number of abnormalities in unridden horses was 4.92, in ridden horses 2.92 and in horses with clinical back pain 4.69. No lesions were found between T6 and T10 and 68% of lesions were found between T14 and T17. No significant difference (p &lt; 0.05) was found between the three groups in the number or location of abnormal images. Conclusion The main conclusion was that every horse in this study (n = 39) had at least one site of SSL desmitis (range 2 to 11). It was clear that ultrasonographically diagnosed SSL desmitis cannot be considered as prima facie evidence of clinically significant disease and further evidence is required for a definitive diagnosis.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are

Genome-wide transcriptome analysis reveals equine embryonic stem cell-derived tenocytes resemble fetal, not adult tenocytes.

BACKGROUND: Tendon injuries occur frequently in human and equine athletes. Treatment options are limited, and the prognosis is often poor with functionally deficient scar tissue resulting. Fetal tendon injuries in contrast are capable of healing without forming scar tissue. Embryonic stem cells (ESCs) may provide a potential cellular therapeutic to improve adult tendon regeneration; however, whether they can mimic the properties of fetal tenocytes is unknown. To this end, understanding the unique expression profile of normal adult and fetal tenocytes is crucial to allow validation of ESC-derived tenocytes as a cellular therapeutic. METHODS: Equine adult, fetal and ESC-derived tenocytes were cultured in a three-dimensional environment, with histological, morphological and transcriptomic differences compared. Additionally, the effects on gene expression of culturing adult and fetal tenocytes in either conventional two-dimensional monolayer culture or three-dimensional culture were compared using RNA sequencing. RESULTS: No qualitative differences in three-dimensional tendon constructs generated from adult, fetal and ESCs were found using histological and morphological analysis. However, genome-wide transcriptomic analysis using RNA sequencing revealed that ESC-derived tenocytes' transcriptomic profile more closely resembled fetal tenocytes as opposed to adult tenocytes. Furthermore, this study adds to the growing evidence that monolayer cultured cells' gene expression profiles converge, with adult and fetal tenocytes having only 10 significantly different genes when cultured in this manner. In contrast, when adult and fetal tenocytes were cultured in 3D, large distinctions in gene expression between these two developmental stages were found, with 542 genes being differentially expressed. CONCLUSION: The information provided in this study makes a significant contribution to the investigation into the differences between adult reparative and fetal regenerative cells and supports the concept of using ESC-derived tenocytes as a cellular therapy. Comparing two- and three-dimensional culture also indicates three-dimensional culture as being a more physiologically relevant culture system for determining transcriptomic difference between the same cell types from different developmental stages

Genome-wide transcriptome analysis reveals equine embryonic stem cell-derived tenocytes resemble fetal, not adult tenocytes

Background: Tendon injuries occur frequently in human and equine athletes. Treatment options are limited, and the prognosis is often poor with functionally deficient scar tissue resulting. Fetal tendon injuries in contrast are capable of healing without forming scar tissue. Embryonic stem cells (ESCs) may provide a potential cellular therapeutic to improve adult tendon regeneration; however, whether they can mimic the properties of fetal tenocytes is unknown. To this end, understanding the unique expression profile of normal adult and fetal tenocytes is crucial to allow validation of ESC-derived tenocytes as a cellular therapeutic. Methods: Equine adult, fetal and ESC-derived tenocytes were cultured in a three-dimensional environment, with histological, morphological and transcriptomic differences compared. Additionally, the effects on gene expression of culturing adult and fetal tenocytes in either conventional two-dimensional monolayer culture or three-dimensional culture were compared using RNA sequencing. Results: No qualitative differences in three-dimensional tendon constructs generated from adult, fetal and ESCs were found using histological and morphological analysis. However, genome-wide transcriptomic analysis using RNA sequencing revealed that ESC-derived tenocytes’ transcriptomic profile more closely resembled fetal tenocytes as opposed to adult tenocytes. Furthermore, this study adds to the growing evidence that monolayer cultured cells’ gene expression profiles converge, with adult and fetal tenocytes having only 10 significantly different genes when cultured in this manner. In contrast, when adult and fetal tenocytes were cultured in 3D, large distinctions in gene expression between these two developmental stages were found, with 542 genes being differentially expressed. Conclusion: The information provided in this study makes a significant contribution to the investigation into the differences between adult reparative and fetal regenerative cells and supports the concept of using ESC-derived tenocytes as a cellular therapy. Comparing two- and three-dimensional culture also indicates three-dimensional culture as being a more physiologically relevant culture system for determining transcriptomic difference between the same cell types from different developmental stages.</p

The transcription factor scleraxis differentially regulates gene expression in tenocytes isolated at different developmental stages

The transcription factor scleraxis (SCX) is expressed throughout tendon development and plays a key role in directing tendon wound healing. However, little is known regarding its role in fetal or young postnatal tendons, stages in development that are known for their enhanced regenerative capabilities. Here we used RNA-sequencing to compare the transcriptome of adult and fetal tenocytes following SCX knockdown. SCX knockdown had a larger effect on gene expression in fetal tenocytes, affecting 477 genes in comparison to the 183 genes affected in adult tenocytes, indicating that scleraxis-dependent processes may differ in these two developmental stages. Gene ontology, network and pathway analysis revealed an overrepresentation of extracellular matrix (ECM) remodelling processes within both comparisons. These included several matrix metalloproteinases, proteoglycans and collagens, some of which were also investigated in SCX knockdown tenocytes from young postnatal foals. Using chromatin immunoprecipitation, we also identified novel genes that SCX differentially interacts with in adult and fetal tenocytes. These results indicate a role for SCX in modulating ECM synthesis and breakdown and provide a useful dataset for further study into SCX gene regulation