目的 探讨利用小肠黏膜下层（SIS）复合骨髓间充质干细胞（BMSCs）体外构建心肌组织薄片的可行性。方法 将自大鼠骨髓分离培养的BMSCs经5-氮胞苷（5-Aza）诱导培养3周后种植在经脱细胞处理的SIS浆膜面，在体外动态条件下共培养2周，构建组织工程心肌组织薄片，并进行病理组织学、超微结构和免疫组织化学染色观察。结果 与BMSCs体外共培养2周的SIS经苏木精-伊红（HE）染色显示，细胞在SIS上不只局限于材料表层，呈多层分布，部分细胞逐步向深层迁移和渗透。扫描电子显微镜观察发现，细胞较好地在SIS上黏附、生长和迁移，细胞分泌大量的细胞外基质。免疫组织化学染色结果显示，SIS上的细胞为表达α-actin、cTnⅠ和connexin-43的心肌样细胞。结论 在体外将SIS复合经5-Aza诱导的BMSCs，成功地初步构建出组织工程化心肌组织薄片。SIS是一种良好的心肌组织工程生物支架材料。

Objective To explore the feasibility of in vitro construction of tissue-engineered cardiac sheet by small intestinal submucosa (SIS) with bone mesenchymal stem cells (BMSCs). Methods BMSCs separated from rat bone marrow were induced by 5-azacytidine (5-Aza) for 3 weeks, and were seeded on the serosal side of acellular SIS scaffold. The tissue-engineered cardiac tissue sheet was established in vitro after co-culture in dynamic culture system for 2 weeks, and its properties were evaluated by histological, ultrastructural and immunohistochemical examinations. Results After co-culture for 2 weeks, HE staining revealed that the seeded cells were not restricted in the upper area of SIS, forming multiple uniform layers on SIS, and some cells penetrated and migrated into the porous matrix. Scanning electronic microscopy revealed that BMSCs adhered, proliferated and migrated well on SIS, and secreted a large amount of extracellular matrix. Immunohistochemical staining demonstrated that the cells on SIS were cardiomyocyte-like cells with the expression of α-actin, cTnⅠ and connexin-43. Conclusion The engineered cardiac tissue sheet has been successfully constructed by SIS with 5-Aza-induced BMSCs in vitro, and SIS is an ideal bio-scaffold material for cardiac tissue engineering.