Mesenchymal stromal cells (MSCs) have long been used in research for bone regeneration, with evidence of their beneficial properties. In the segmental area of MSC-based therapies, MSC-derived extracellular vesicles (EVs) have also shown great therapeutic effects in several diseases, including bone healing. This study aimed to assess whether the conditioning of MSCs improves the therapeutic effects of their derived extracellular vesicles for bone regeneration. Electronic research was performed until February 2021 to recover the studies in the following databases: PubMed, Scopus, and Web of Science. The studies were screened based on the inclusion criteria. Relevant information was extracted, including in vitro and in vivo experiments, and the animal studies were evaluated for risk of bias by the SYRCLE tool. A total of 463 studies were retrieved, and 18 studies met the inclusion criteria (10 studies for their in vitro analysis, and 8 studies for their in vitro and in vivo analysis). The conditioning methods reported included: osteogenic medium; dimethyloxalylglycine; dexamethasone; strontium-substituted calcium silicate; hypoxia; 3D mechanical microenvironment; and the overexpression of miR-375, bone morphogenetic protein-2, and mutant hypoxia-inducible factor-1α. The conditioning methods of MSCs in the reported studies generate exosomes able to significantly promote bone regeneration. However, heterogeneity regarding cell source, conditioning method, EV isolation and concentration, and defect model was observed among the studies. The different conditioning methods reported in this review do improve the therapeutic effects of MSC-derived EVs for bone regeneration, but they still need to be addressed in larger animal models for further clinical application.

Background: This work reports a case of urethral obstruction by urolith in a female cat. The patient had a history of hematuria beginning approximately 2 months before visiting the clinic, with anorexia, apathy, emesis, tenesmus and absence of urination. Following physical and ultrasonic examinations, urethral obstruction by urolith was diagnosed. Although feline lower urinary tract disease (FLUTD) is common in both males and females, a urethral obstruction in female cats is extremely rare. This report aims to alert veterinarians to such an occurrence, highlighting the importance of early diagnosis and treatment in view of the severity of the consequences of a urethral obstruction.Case: An undefined, female cat of indefinite age, with a history of hematuria, emaciation, anorexia, apathy, emesis, tenesmus and anuria, presented at our clinic. Physical examination revealed dehydration, discrete rectal prolapse and dysuria. During abdominal palpation, a rigid spherical-shaped structure was observed in the hypogastric region, and complementary examinations were subsequently performed. Hematological examination revealed leukocytosis and increased serum urea and creatinine levels. Abdominal ultrasound examination showed that the urinary vesicle was full, with heterogeneous anechoic content with discrete sedimentation, as well as the presence of a hyperechogenic structure that formed an acoustic shadow at the transition between the bladder trigone and the urethra. In addition, both renal pelves presented dilatation byanechoic content, and measured about 0.5 cm. Treatment with amoxicillin and potassium clavulanate (20 mg/kg administered intravenously) was initiated, and the patient was referred to undergo a surgical procedure to remove the calculus. When exploring the abdominal cavity, the urinary vesicle was identified, which appeared to be rigid. Ventral cystotomywas performed, and calculus was identified in the proximal urethra, which was ‘milked’ into the bladder and removed. The patient showed good surgical recovery, presenting normorexia and normuria after anesthetic recovery. The patient remained hospitalized for 12 h. On the following day, hematological tests showed improvement in leukocytosis and azotemia, and amoxicillin was prescribed with potassium clavulanate (20 mg/kg 12/12 h), tramadol (4 mg/kg 8/8 h) and ketoprofen (1mg/kg SID). The patient was requested to return for a follow-up appointment 5 days later, but the patient did not return.Discussion: Although the low frequency of urethral obstruction in female felines does not reflect the common occurrence of FLUTD, the present report warns of the importance of the final diagnosis in patients with manifestations of urinary tract disorders, especially female animals, in order to exclude the possibility of urolithiasis. This attention will allow the correct treatment of each condition and complete recovery of the patient, avoiding possible obstructions and serious consequences related to the presence of an obstruction for a prolonged period of time. The present work reported a case of feline urethral obstruction, a condition considered rare for females of this species. Urethral obstruction is considered an emergency in the small animal clinic, and the treatment, which consists of clearing and correcting systemic effects, should be rapid as the consequences for the patient can be severe and permanent, and can even lead to death. The possibility of urethral obstruction was not ignored despite the rare occurrence in females, which allowed for rapid surgical intervention to clear and reestablish the urinary flow, which contributed to the successful recovery of the patient.Keywords: urolithiasis, feline lower urinary tract disease, urethral calculus.

Background:The urachus is a tubular structure continuous with the urinary bladder and the allantois in foetal mammals. It serves as a communication between these two structures. At birth, it loses its function and undergoes atrophy by fibrous proliferation within the lumen. When this atrophy process fails at some point, congenital anomalies of the urachus occur. These anomalies are rare in animals, and to our knowledge, the urachal cyst has not yet been described in dogs. The present work is unique in that it reports a case of this congenital defect in a dog. Our aim is to increase awareness and to discuss the clinical presentation, the imaging techniques used, and the final diagnosis of this anomaly. Case: A 3-year-old bitch Pit Bull was presented for veterinary assistance to investigate recurrent pseudopregnancy and an irregular estrous cycle. The animal presented in good bodily condition, and the white blood count and clinical biochemistry were normal. At ultrasound, 2 tubular structures, filled by an echogenic fluid mimicking uterine topography, were found extending through the umbilical and hypogastric regions. No alterations in structure, echogenicity or echotexture of the other organs were observed, including the ovaries and uterus. On exploratory laparotomy, a cystic structure was found, with 2 segments: the larger one was on the left side, attached to the apex of the bladder by its caudal portion; the other was on the right side, attached to the spleen by its cranial portion and to the apex of the bladder by its caudal portion in connection with the left segment. The ovaries, uterus and uterine horns showed no macroscopic alterations. The structure was removed, and after analysis (macroscopic morphology, wall histopathology and biochemistry of the contained fluid), it was determined to be a urachal cyst. The animal recovered uneventfully. Discussion: Ultrasound is an important tool for the evaluation of reproductive cycle physiology and its pathologies. At first, the owner's complaint justified a fairly straightforward evaluation and clinical management of pseudopregnancy in a very healthy animal based on the history and clinical and complementary exams. However, ultrasound examination revealed two tubular structures filled with echogenic fluid in the lower abdomen. This made the case more complex, as these were interpreted as uterine horns by three different veterinarians, leading to the possibility of pyometra. The management of this condition must be cautious, since the animal's condition could rapidly deteriorate, necessitating an exploratory laparotomy. Based on the clinical presentation, macroscopic anatomy, fluid biochemistry and histological evaluations, the diagnosis of urachal cyst was proposed. Congenital anomalies occur when the urachus fails to obliterate. Four types can be found: patent urachus, urachal sinus, urachal diverticulum and urachal cyst. The urachal cyst occurs when the urachus encompasses a cyst-like structure that is closed to the umbilicus and the bladder lumen. The urachus be...