Mice cope with parabiosis — Assessment of their physiological changes of life

The purpose of this study was to establish a parabiotic mice model and assess the physiological changes of the mice under the parabiotic state. Thirteen pairs of isogenic partners were studied. The model was created by preparing a bridge of skin and subcutaneous tissues between the two mice starting distal of the elbow joint along the humerus along the lateral costal region until the end of the waist line. Physiological, social and affective qualities of life were studied in the mice through behavioural observations for 120 days following the parabiotic surgery. During the first 2-3 days following the operation, the animals suffered from severe pain and distress. During the following days and weeks, the physiological system began to recover and the animals displayed behavioral adaptations to the parabiotic condition. All animals survived at day 120. At three days post operation, the body weight began to decrease. Following this, the animals experienced a continual body weight recovery and reached pre-surgical measures at about 30 days post op. Forty-eight h post op., faecal corticosterone-metabolites were extremely elevated, but their levels returned to two to four times of levels in control females within 72 hours post op. The faecal corticosterone-metabolite levels decreased near to control values on day 75. Out of the 13 pairs, the blood exchange rate of three parabiotic partners was tested, with the result being normal post op. After 12 weeks, the total blood exchange between both partners needed 63 or 46 or 107 min, respectively. These results demonstrated that the animals could adapt behaviourally to the parabiotic situation. Therefore, this parabiosis mouse model may provide useful insights in many research areas, such as transplantation immunity, hematological system and metabolism, etc.