Osteoarthritis (OA) of the equine distal interphalangeal joint (DIPJ) is a common cause of lameness. MicroRNAs (miRNAs) from biofluids such as plasma and synovial fluid make promising biomarker and therapeutic candidates. The objectives of this study are (1) Identify differentially expressed (DE) miRNAs in mild and severe equine DIPJ OA synovial fluid samples and (2) Determine the effects of DE miRNAs on equine chondrocytes in monolayer culture. Synovial fluid samples from five horses with mild and twelve horses with severe DIPJ OA were submitted for RNA-sequencing; OA diagnosis was made from MRI T2 mapping, macroscopic and histological evaluation. Transfection of equine chondrocytes (n=3) was performed using the Lipofectamine® RNAiMAX system with a negative control and a miR-92a mimic and inhibitor. qPCR was used to quantify target mRNA genes. RNA-seq showed two miRNAs (miR-16 and miR-92a) were significantly DE (p<0.05). Ingenuity Pathway Analysis (IPA) identified important downstream targets of miR-92a involved in the pathogenesis of osteoarthritis and so this miRNA was used to transfect equine chondrocytes from three donor horses diagnosed with OA. Transfection was successfully demonstrated by a 1000-20000 fold increase in miR-92a expression in the equine chondrocytes. There was a significant (p<0.05) increase in COMP, COL3A1 and Sox9 in the miR-92a mimic treatment and there was no difference in ADAMTS-5 expression between the miR-92 mimic and inhibitor treatment. RNA-seq demonstrated miR-92a was downregulated in severe OA synovial fluid samples which has not previously been reported in horses, however miR-92a is known to play a role in the pathogenesis of OA in other species. Over expression of miR-92a in equine chondrocytes led to significantly increased COMP and Sox9 expression, consistent with a chondrogenic phenotype which has been identified in human and murine chondrocytes.
Heterotopic ossification is the formation of extraskeletal mineralized tissue commonly associated with either trauma or surgery. While several mouse models have been developed to better characterize the pathologic progression of HO, no model currently exists to study HO of the hip, the most common location of acquired HO in patients. Owing to the unique biological mechanisms underpinning the formation of HO in different tissues, we sought to develop a model to study the post-surgical HO of the hip. Wild-type mice C57BL/6J mice were used to study the procedure outcomes, while Pdgfra-CreERT2;mT/mG and Scx-GFP reporter animals were used for the lineage tracing experiments (total n=16 animals, male, 12 weeks old). An anterolateral approach to the hip was performed. Briefly, a 2 cm incision was made centered on the great trochanter and directed proximal to the iliac crest and distally over the lateral shaft of the femur. The joint was then reached following the intermuscular plane between the rectus femoris and gluteus medius muscles. After the joint was exposed, the articular cartilage was removed using a micropower drill with a 1.2 mm reamer. The medius gluteus and superficial fascia were then re-approximated with Vicryl 5-0 suture (Ethicon Inc, Somerville, NJ) and skin was then closed with Ethilon 5-0 suture (Ethicon Inc). Live high resolution XR imaging was performed every 2 wks to assess the skeletal tissues (Faxitron Bioptics, Tucson, AZ). The images were then scored using the Brooker classification. Ex-vivo microCT was conducted using a Skyscan 1275 scanner (Bruker-MicroCT, Kontich, Belgium). 3D reconstruction and analysis was performed using Dragonfly (ORS Inc., Montreal, Canada). For the histological analysis of specimens, Hematoxylin and Eosin (H&E), modified Goldner's Trichrome (GMT) stainings were performed. Reporter activity was assessed using fluorescent imaging.Introduction and Objective
Materials and Methods
Low-intensity pulsed ultrasound (LIPUS) enhanced osteogenic differentiation of osteoprogenitor cells derived from mouse induced pluripotent cells (iPSCs) without embryoid body formation. Our findings provide insights on the development of LIPUS as an effective technology for bone regeneration strategies using iPSCs. iPSCs represent a promising cell source for regenerative medicine such as bone regeneration because of their unlimited self-renewal property and ability of differentiation into all somatic cell types. Recently, we developed an efficient protocol for generating a highly homogeneous population of osteoprogenitor cells from embryonic stem cells by using a direct-plating method without EB formation step. It is well-recognised that LIPUS accelerates the fracture healing. There have been several reports showing that LIPUS stimulates the osteogenic differentiation of mesenchymal stem cells (MSCs) Summary Statement
Introduction
Little is known about the increase in length of tendons in postnatal life or of their response to limb lengthening procedures. A study was carried out in ten young and nine adult rabbits in which the tibia was lengthened by 20% at two rates 0.8 mm/day and 1.6 mm/day. The tendon of the flexor digitorum longus (FDL) muscle showed a significant increase in length in response to lengthening of the tibia. The young rabbits exhibited a significantly higher increase in length in the FDL tendon compared with the adults. There was no difference in the amount of lengthening of the FDL tendon at the different rates. Of the increase in length which occurred, 77% was in the proximal half of the tendon. This investigation demonstrated that tendons have the ability to lengthen during limb distraction. This occurred to a greater extent in the young who showed a higher proliferative response, suggesting that there may be less need for formal tendon lengthening in young children.
