Biomedical Research

Introduction: Hemoglobin Vesicles (HbVs) have been developed as artificial oxygen carriers in the form of liposomes containing concentrated hemoglobin extracted from outdated human Red Blood Cells (RBC). Because HbVs have a small particle size of 250 nm in diamete, rthey can efficiently perfuse capillaries.

Objectives: To evaluate the reperfusion of capillaries with HbVs in a tracheal transplant model and compare it with that of RBC.

Methods: Isogenic mice were used as both donors and recipients in a parallel trachea transplant model, which realizes simultaneous histological observation of the recipient and the grafted tracheas. Both ends of the donor trachea were anastomosed end-laterally to the recipient trachea to form in parallel. After transplantation, 0.3 ml of HbV solution (Hb concentration, 10 g/dl) was administered via the tail vein. The recipients were sacrificed 1, 4, 6, and 8 h after surgery. The tracheas were harvested, and the reperfusion of tracheal Subepithelial Capillaries (SEC) was histologically evaluated.

Results: A significant number of particles defined as HbV by electron microscopy were observed in the SEC of the grafted tracheas 4 h after the transplant surgery and HbV administration when no RBC were found in the SECs. The number increased 6 h later, and HbVs were observed in the SEC 8 h later.

Discussion: Our experiment with a tracheal transplantation model suggests that HbVs, which are smaller than RBC, can reperfuse the capillaries of grafts earlier than RBC after transplantation and contribute to the oxygenation of transplanted tissues.

Author(s): Hiroto Onozawa, Mitsutomo Kohno, Kana Oiwa, Ryo Hashimoto, Masatoshi Yamaguchi, Tai Hato, Masazumi Watanabe, Hirohisa Horinouchi, Hiromi Sakai, Koichi Kobayashi, Masayuki Iwazaki
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