Subcutaneous Islet Transplantation with Oxygen Delivery

After implanting the oxygen delivery device into the subcutaneous space of diabetic recipient rats, 6000 islet equivalents (IEQs) of syngeneic rat islets were transplanted into subcutaneous site uniformly distributed just above the 30-mm-diameter diffuser plate of the oxygen delivery device using a plastic cannula-type 18G puncture needle and a gastight syringe (Hamilton Co., Reno, NV, USA)^{34 (link)} to receive oxygen supply directly from the device. Then, the transplanted islets were covered with a seprafilm (KAKEN PHARMACEUTICAL CO., LTD., Tokyo, Japan) to prevent them from moving away and to fix them to the transplant site. An intravenous glucose tolerance test (IVGTT) and serum C-peptide (a byproduct of insulin production) measurement were performed as in vivo functional assessments of transplanted islets. The IVGTT was performed as previously described^{43 (link)}. D-glucose (3.0 g/kg) was intravenously infused, and the blood glucose concentrations were determined before and at 5, 10, 20, 30, 60, 90, and 120 min after the injection of glucose. Rat serum C-peptide was measured before and at 60 and 120 min after glucose injection using a rat C-peptide ELISA kit (Mercodia, Uppsala, Sweden). These assessments were performed 3 days after transplantation in the Pure oxygen and No gas groups (n = 5, respectively).