Abstract: Objective To transplant the microencapsulated recombinanted Chinese hamster ovary (CHO ) cells into the infracted myocardium of rodent animals and investigate whether vascular endothelial growth factor (VEGF) secreted by the implanted CHO cells could augment angiogenesis and improve cardiac function. Methods The cDNA of VEGF was transferred into CHO cells with plasmid stable transfection. After microencapsulation, the cell growth in microcapsules and the VEGF level in the culture supernatant were evaluated. Two weeks after myocardial infarction, the microencapsulated CHO cells (MC-CHO group ) were implanted into the border of infracted myocardium, as well as similar amount of CHO cells (CHO group ) , blank microcapsule (MC group ) and non-serum culture medium (control group ) as controls, 12 rats per group. The cardiac function improvement was evaluated 3 weeks after transplantation, while the survival status of implanted CHO cells, in situ secretion of VEGF and capillary density were assayed by histology. Results CHO cells could grow and proliferate after microencapsulation. The secretion of VEGF was detectable in culture media supernatant, with the highest concentration of 3 852 pg/m l at day 8. As compared to the other three groups, the left ventricular dimension and cardiac function were significantly improved in MC-CHO group 3 weeks after transplantation. The capillary density of MC-CHO group were increased significantly than those of CHO group, MC group and control group (22. 3±3. 1 vs. 15. 6±2. 8, 11. 4±2. 5, 13. 2±2. 7 vessels per 0.13 mm2, P lt; 0.05). The implanted microcapsule maintained its original shape and protected theCHO cells in it. Conclusion M icroencapsulaed recombinanted CHO cells transplantation might be a promising app roach to augment angiogenesis and improve the cardiac function in infarction myocardium.