BACKGROUND:Human umbilical cord mesenchymal stem cel s belong to a special class of stem cel s with a limited number, which are difficult to isolate and purify. Importantly, there is a lack of clinical understanding of biological characteristics of human umbilical cord mesenchymal stem cel s. OBJECTIVE:To study the bioactive properties and cardiomyocyte-like differentiation of human umbilical cord mesenchymal stem cel s. METHODS:Under a sterile col ection, umbilical cord blood of newborn from cesarean section was col ected to isolate human mesenchymal stem cel s by digestion using col agenase II. Immunohistochemical staining was used to detect cel surface markers and observe morphological characteristics, and MTT assay used to detect cel proliferation and draw cel growth curve. Cel s grown to 70%-80%confluence were treated with 10μmol/L 5-azacytidine for 24 hours. RESULTS AND CONCLUSION:One week after adherent tissue culture, human umbilical cord mesenchymal stem cel s were seen, and then the cel s cultured in culture medium showed colony growth. Within 24 hours of cel seeding, cel s at passages 3 and 10 were at latency period and then grew logarithmical y with a doubling time of 30 hours. Immunocytochemical staining showed that passage 3 cel s at over 90%confluence expressed CD44 and CD29, rather than CD28 and CD31.Three weeks after induced culture, the cel s with the absence of processes grew irregularly;after 4 weeks, the cel s were round in shape and expressed cardiac-specific immune markers. Taken together, isolated human umbilical cord mesenchymal stem cel s with strong proliferative ability have the basic biological characteristics of mesenchymal stem cel s, which are capable of differentiating into cardiomyocyte-like cel s induced by 5-azacytidine.