Hemorrhagic Shock and Rescue in Aging Mice

Young (5-6-week-old) and mature (3-4-month-old) male C57BL/6 mice used were obtained from Jackson laboratories and aged (23-26-month-old) C57BL/6 mice were from the National Institute of Aging rodent colony. Animal studies were conducted as per the protocol approved by the Institutional Animal Use and Care committee at the Augusta University. Hemorrhagic shock was induced as described before [25 (link)]. Briefly 60% blood volume was removed in 45 minutes through femoral artery, to induce hypovolemic shock (Mean arterial pressure: 30-35 mm Hg) and this MAP was maintained for another 45 minutes (shock period). Sham animals were not subjected to bleeding or fluid resuscitation, but they were subjected to laparotomy and groin incisions. For survival studies, EVs or vehicle was given immediately after the shock period (Fig. 1A). Each group for this study had 5-6 animals. For organ function studies, the animals were resuscitated following shock period for 1 hour, with Ringers Lactate (twice the shed blood volume), observed for another two hours and sacrificed to remove tissues for mitochondrial function assessment (Fig. 2A). Each group for this study had 6 animals. In this latter group, EVs or vehicle was administered as a single dose (50 µl; 2 mg/Kg body weight) at 10 minutes after the start of fluid resuscitation.