Human cord derived MSC cell(Allcare Biomedical)

The main purpose is to evaluate the safety and tolerability of single and multiple doses of human umbilical cord mesenchymal stem cell injection in the treatment of moderate to severe ulcerative colitis, explore its maximum tolerated dose (MTD) and dose-limiting toxicity (DLT), and provide a basis for the design of a phase II clinical trial; the secondary purpose is to preliminarily evaluate the effectiveness of human umbilical cord mesenchymal stem cell injection in the treatment of moderate to severe ulcerative colitis; explore the pharmacokinetic (PK) characteristics and immunogenicity of human umbilical cord mesenchymal stem cell injection; explore the pharmacodynamic characteristics of human umbilical cord mesenchymal stem cell injection in the treatment of moderate to severe ulcerative colitis.