Mesenchymal stromal cells (MSC) have recently been explored for their potential use as therapeutics in human and veterinary medicine applications, such as the treatment of endometrial inflammation and infertility. Allogeneic MSC-derived extracellular vesicles (EVs) may also provide therapeutic benefits with advantage of being an “off-the-shelf” solution, provided they can be produced in large enough quantities, without contamination from bovine EVs contained in fetal bovine serum that is a common component of cell culture media. Towards this aim, we demonstrated the successful isolation and characterisation of equine MSCs from pre-implantation embryos. We also demonstrate that many of these lines can be propagated long-term in culture while retaining their differentiation potential, and conducted a head-to-head comparison of two bioreactor systems for scalable EV production including in serum-free conditions. Based on our findings, the CELLineTM AD 1000 flasks enabled higher cell density cultures and significantly more EV production than the FiberCellTM system or conventional culture flasks. These findings will enable future isolation of equine MSCs and the scalable culture of their EVs for a wide range of applications in this rapidly growing field.

A 1.5-year-old, female, entire German shepherd dog was presented for evaluation of an abdominal mass. The dog had a 4-month history of polydipsia, polyuria, diarrhoea, and weight loss despite polyphagia. Abdominal ultrasound confirmed a large abdominal mass suspected to be uterine in origin. An exploratory celiotomy revealed a 4.3 kg, 26 × 17 × 17 cm multinodular mass entirely encompassing the uterus, left ovary and left kidney. A combined ovariohysterectomy and left nephrectomy were undertaken. Histopathology confirmed stage ΙΙ renal nephroblastoma with favourable histology. Chemotherapy was declined and 86 days following surgery, significant abdominal metastases were identified on a computed tomography scan. The patient was euthanased 113 days after surgery due to progressive disease. This is the first report to display the rapid presumed metastasis of a canine nephroblastoma, without gross metastasis at initial surgical resection, through advanced imaging. This is also the first reported case of polyphagia despite weight loss as a presenting clinical sign.

Case summary We describe two cats that had episodic tachypnoea and increased respiratory effort during periods of paroxysmal supraventricular tachycardia (SVT). Thoracic radiographs at the time of clinical signs were consistent with cardiogenic pulmonary oedema. Echocardiography following stabilisation revealed a hypertrophic cardiomyopathy phenotype with normal left atrial size in both cats. The first cat was initially treated with diltiazem, but this did not reduce the frequency of the clinical episodes. Diltiazem was switched to atenolol and the cat remained well without further recurrence. At the time of writing, the cat was reported to be well, 3 years after the initial diagnosis of SVT. The second cat was first managed with diltiazem and was then transitioned to atenolol due to recurrent clinical episodes. The episodes were less frequent with atenolol but still present. Therefore, atenolol was changed to sotalol. The cat remained well on sotalol for 2 years with only one recurrent episode during a painful event. The patient then suffered a sudden cardiac death, 5 years after the initial diagnosis of SVT. Relevance and novel information To our knowledge, this is the first report that describes flash pulmonary oedema developing secondary to episodic paroxysmal SVT in cats. Despite the severity and speed of respiratory compromise, prognosis may be good with an adequate arrhythmia control.