Safety Evaluation Of Exosomes Derived From Human Umbilical Cord Mesenchymal Stem Cell

Background aims: Clinical phase I and II studies have shown that mesenchymal stem cells(MSCs) transplantation is beneficial to the repair of acute myocardial infarction(AMI), but is restrained by the low survival rate of transplanted MSCs, aggravation of stenosis, and their tumorigenic problem. Mounting evidence shows that non-cell-based transplantation of exosomes derived from MSCs(MSC-exosomes) has more potential protective and reparative effects than MSCs have. However, whether it is safe to transplant MSC-exosomes into tissues is still not clear yet. In this study, we used many animal models and evaluated the safety of transplantation of exosomes derived from human umbilical cord mesenchymal stem cell(hucMSC-exosomes). Methods: The cardiac blood from a healthy rabbit was taken and the fibrinogen in blood was removed. Then 2% red blood cell(RBC) suspension with normal saline was prepared and incubated with hucMSC-exosomes at 37℃. Hemolysis and erythrocyte sedimentation were observed at 3 h. For analysis of vascular and muscle stimulation, hucMSC-exosomes were infused via the ear marginal vein and quadriceps muscle. Any changes of stimulation, such as congestion, edema, necrosis or inflammatory cells infiltration at the injection sites were visual observed. The vascular, muscle and surrounding tissues were collected and made into sections, which were then stained with hematoxylin and eosin(H&E) and the degree of stimulation was assessed. Healthy guinea pigs were taken and prepared for intraperitoneal injection with hucMSC-exosomes. Sentitization was made every other day and three consecutive times. 14 days after the third sensitization, the final sensitization was made. Allergy symptoms and the time of symptom appearance and disappearance were recorded and the reaction degree of allergy was judged. To detect pyrogen, huc MSC-exosomes were infused via the ear marginal vein and rectal temperature was measured every hour, for a total of three times. The alteration temperature was used to evaluate the existence of pyrogen. Next, huc MSC-exosomes were given to Sprague-Dawley(SD) rats via the tail vein. The blood was collected and routine blood indexes were detected at fixed times. To study safety in vivo, huc MSC-exosomes(400μg and 800μg) were infused intravenously into SD rats with AMI, once a day and lasted for 7 days. The growth of rats was obersved closely. Rats’ weight was measured and tail vein blood was collected to detect liver and renal function. Results: huc MSC-exosomes had no effects on hemolysis and routine blood indexes. It caused no stimulation to vascular, muscle and surrounding tissues. There is also no allergen and pyrogen in huc MSC-exosomes. In addition, huc MSC-exosomes had a protective effect on weight loss in SD rats with AMI and had no adverse effects on liver or renal function. The results showed that huc MSC-exosomes were safe and applicable.Conclusions: huc MSC exosomes are well tolerated in animal models. This study provides evidence for the safety of intravenous infusion in future clinical therapy.