Medial malleolus fragmentation following talocalcaneal arthrodesis by a dorsomedial approach in a horse.

A 16-year-old, Quarter Horse mare was presented for a 3/5 right hind lameness associated with osteoarthritis of the talocalcaneal joint (TCLJ). Positron emission tomography (PET) and computed tomography (CT) demonstrated marked increased uptake of 18F-sodium fluoride and bone remodeling at the medial facet of the TCLJ, respectively. Under general anesthesia 2 cortical screws (4.5 and 5.5 mm) were placed in neutral fashion via an arthrotomy from dorsomedial to plantaromedial through the medial facet of the TCLJ followed by copious lavage of the tarsocrural joint. Eight weeks after surgery, observable effusion of the tarsocrural joint was present and lameness had worsened. Radiographic examination revealed a fragmented medial malleolus of the tibia, likely secondary to repetitive trauma of the screw heads during tarsal flexion. Repeated CT showed partial fusion of the TCLJ. Both screws were removed and the tarsocrural joint was thoroughly lavaged arthroscopically. At a 20-month recheck the lameness had not improved, and ultrasound examination revealed severe thickening of the TCLJ capsule. Recheck examination 48 mo after surgery showed complete fusion of the TCLJ and resolution of the lameness. Key clinical message: Diagnosis of osteoarthritis of the TCLJ is challenging. Management by arthrodesis using a dorsomedial approach can result in fragmentation of the medial malleolus, with secondary synovitis and capsulitis of the tarsocrural joint

Scintigraphic tracking of allogeneic mesenchymal stem cells in the distal limb after intra-arterial injection in standing horses

Objective: To assess the feasibility of intra-arterial administration of allogeneic mesenchymal stem cells (MSC) in the median artery of standing horses and evaluate the distribution and retention of radiolabeled cells. Study Design: In vivo experimental study. Animals: Six research horses. Methods: Technetium-HexaMethyl-Propylene-Amine Oxime-labeled MSC were injected under ultrasound guidance in the median artery of 6 front limbs of 3 horses, standing under sedation. Scintigraphic images were obtained at the time of injection, and at 1, 6, and 24 hours postinjection. Six additional limbs from 3 horses were similarly injected with unlabeled MSC. Ultrasound was performed the following day for assessment of vascular changes. Results: Intra-arterial injection was performed successfully in 11 of 12 limbs. In 1 limb, partial periarterial injection compromised the success of the procedure. Homogeneous distribution of radiolabeled MSC was observed through the entire distal limb, including within the hoof. Partial venous thrombosis was found in both groups of horses, but was subjectively less severe in horses injected with unlabeled MSC. No lameness was observed. Transient swelling of the distal limb occurred in only 1 limb. Conclusion: Intra-arterial injection of MSC can be performed in standing horses under sedation and successfully distribute MSC to the distal limb. A risk of periarterial injection was identified but can be reduced with proper sedation, local anesthesia, and increased experience. Partial venous thrombosis was observed as a complication, but did not cause changes of clinical importance, other than rare transient swelling

Effects of postanesthetic sedation with romifidine or xylazine on quality of recovery from isoflurane anesthesia in horses

Objective—To test the hypothesis that postanesthetic sedation with romifidine would dose-dependently improve recovery quality of recovery from isoflurane anesthesia in horses more than postanesthetic sedation with xylazine. Design—Prospective, randomized, blinded clinical trial. Animals—101 healthy adult horses examined at the University of California-Davis Veterinary Medical Teaching Hospital from 2007 to 2009. Procedures—Horses were sedated with xylazine, and anesthesia was induced with guaifenesin, diazepam, and ketamine via a standardized drug protocol. Anesthesia for surgical or diagnostic procedures was maintained with isoflurane in oxygen for 1 to 4 hours. At the end of anesthesia, horses were moved to a padded stall for recovery. Once the breathing circuit was disconnected and the patient was spontaneously breathing, either xylazine (100 or 200 μg/kg [45 or 91 μg/lb]) or romifidine (10 or 20 μg/kg [4.5 or 9.1 μg/lb]) was administered IV. Objective patient, surgical, and anesthesia data were recorded. Subjective visual analog scale (VAS) scores of recovery quality were assigned by a single individual who was unaware of the treatment received. A stepwise linear regression model was used to correlate patient and procedure factors with the VAS score. Results—Painful procedures, longer anesthesia times, and the Arabian horse breed were associated with poorer VAS scores. Adjustment for these factors revealed an improved VAS recovery score associated with the use of a romifidine dose of 20 μg/kg. Conclusions and Clinical Relevance—In healthy adult horses anesthetized with isoflurane for > 1 hour, the results of this study supported the use of 20 μg of romifidine/kg, IV, rather than lower romifidine doses or xylazine, for postanesthetic sedation to improve recovery quality

Injectable mineralized microsphere-loaded composite hydrogels for bone repair in a sheep bone defect model

The efficacy of cell-based therapies as an alternative to autologous bone grafts requires biomaterials to localize cells at the defect and drive osteogenic differentiation. Hydrogels are ideal cell delivery vehicles that can provide instructional cues via their composition or mechanical properties but commonly lack osteoconductive components that nucleate mineral. To address this challenge, we entrapped mesenchymal stromal cells (MSCs) in a composite hydrogel based on two naturally-derived polymers (alginate and hyaluronate) containing biomineralized polymeric microspheres. Mechanical properties of the hydrogels were dependent upon composition. The presentation of the adhesive tripeptide Arginine-Glycine-Aspartic Acid (RGD) from both polymers induced greater osteogenic differentiation of ovine MSCs in vitro compared to gels formed of RGD-alginate or RGD-alginate/hyaluronate alone. We then evaluated the capacity of this construct to stimulate bone healing when transplanting autologous, culture-expanded MSCs into a surgical induced, critical-sized ovine iliac crest bone defect. At 12 weeks post-implantation, defects treated with MSCs transplanted in composite gels exhibited significant increases in blood vessel density, osteoid formation, and bone formation compared to acellular gels or untreated defects. These findings demonstrate the capacity of osteoconductive hydrogels to promote bone formation with autologous MSCs in a large animal bone defect model and provide a promising vehicle for cell-based therapies of bone healing

Safety and tracking of intrathecal allogeneic mesenchymal stem cell transplantation in healthy and diseased horses

Abstract Background It is currently unknown if the intrathecal administration of a high dose of allogeneic mesenchymal stem cells (MSCs) is safe, how MSCs migrate throughout the vertebral canal after intrathecal administration, and whether MSCs are able to home to a site of injury. The aims of the study were: 1) to evaluate the safety of intrathecal injection of 100 million allogeneic adipose-derived MSCs (ASCs); 2) to assess the distribution of ASCs after atlanto-occipital (AO) and lumbosacral (LS) injection in healthy horses; and 3) to determine if ASCs homed to the site of injury in neurologically diseased horses. Methods Six healthy horses received 100 × 106 allogeneic ASCs via AO (n = 3) or LS injection (n = 3). For two of these horses, ASCs were radiolabeled with technetium and injected AO (n = 1) or LS (n = 1). Neurological examinations were performed daily, and blood and cerebrospinal fluid (CSF) were evaluated prior to and at 30 days after injection. Scintigraphic images were obtained immediately postinjection and at 30 mins, 1 h, 5 h, and 24 h after injection. Three horses with cervical vertebral compressive myelopathy (CVCM) received 100 × 106 allogeneic ASCs labeled with green fluorescent protein (GFP) via AO injection and were euthanized 1–2 weeks after injection for a full nervous system necropsy. CSF parameters were compared using a paired student’s t test. Results There were no significant alterations in blood, CSF, or neurological examinations at any point after either AO or LS ASC injections into healthy horses. The radioactive signal could be identified all the way to the lumbar area after AO ASC injection. After LS injection, the signal extended caudally but only a minimal radioactive signal extended further cranially. GFP-labeled ASCs were not present at the site of disease at either 1 or 2 weeks following intrathecal administration. Conclusions The intrathecal injection of allogeneic ASCs was safe and easy to perform in horses. The AO administration of ASCs resulted in better distribution within the entire subarachnoid space in healthy horses. ASCs could not be found after 7 or 15 days of injection at the site of injury in horses with CVCM

Gene Expression in Synovial Membrane Cells After Intraarticular Delivery of Plasmid-Linked Superparamagnetic Iron Oxide Particles—A Preliminary Study in Sheep

This study evaluated in vivo gene deliver y and subsequent gene expression within cells of the synovium in the presence of static and pulsating magnetic field application following intraar ticular injection of super paramagnetic iron oxide nanopar ticles linked to plasmids containing reporter genes encoding for fluorescent proteins. Plasmids encoding genes for either green fluorescent protein or red fluorescent protein were bound to super paramagnetic nanopar ticles coated with polyethyleneimine. Larger (200–250 nm) and smaller (50 nm) nanopar ticles were compared to evaluate the effects of size on transfection efficiency as well as any associated intraar ticular reaction. Comparisons between groups were evaluated at 24, 72, and 120 h time periods. Inflammator y response was mild to moderate for all injected par ticles, but was present in the majority of synovial membrane samples evaluated. Larger par ticles tended to be associated with more inflammation than smaller ones. Never theless, intraar ticular application of both experimental and control nanoparticles were well tolerated clinically. Gene expression as determined by obser vation of either green or red intracellular fluorescence was difficult to assess by both epifluorescent light, and confocal microscopy. An insufficient concentration of nanopar ticles in relation to joint volume likely resulted in a limited number of samples with positive evidence of iron staining and with suspected positive evidence of cells expressing fluorescent proteins. Our results indicate that intraar ticular administration of functionalized super paramagnetic iron oxide nanopar ticles resulted in a mild to moderate synovitis and there was in conclusive evidence of gene expression. Fur ther research is warranted to determine the best and most effective repor ter assay for assessment of the in vivo gene deliver y into the joints. In addition, the best suited concentration and size of nanopar ticles, which will optimize gene delivery and expression, while minimizing intraarticular inflammation, needs to be determined