Umbilical Cord Mesenchymal Stem Cells as First-line Treatment for Patients With Acute Graft Versus Host Disease

Allogenic haemopoietic stem cell transplantation (allo-HSCT) is the effective treatment for many hematologic malignancies and some non-malignant diseases. In recent years, with the rapid improvement of economy and medical level, the number of cases of hematopoietic stem cell transplantation (HSCT) develops rapidly in China. In 2019, 12,323 cases of HSCT were completed in China, with allo-HSCT accounting for 9600 cases of which. However, Graft versus host disease (GVHD) is one of the most common and serious complications after Allo-HSCT. The incidence of acute GVHD (aGVHD) is as high as 40%-60% in HLA-matched sibling transplantation, and the incidence is even higher in haplo-hematopoietic stem cell transplantation(haplo-HSCT) and unrelated donor transplantation. By Glucksberg grading standard, the 5-year survival rates of grade III and IV aGVHD are 25% and 5% respectively, indicating severe GVHD directly affects the survival of Allo-HSCT patients. The first-line treatment for aGVHD is still glucocorticoid, while the effective rate is only 30%-50%. Moreover, due to immunosuppression and increasing risk of infection, the efficacy of second-line treatments including polyclonal antibodies, monoclonal antibodies, immunosuppressants, immunotoxins, chemotherapy drugs, and light therapy for steroid resistant aGVHD is also poor, with the overall survival rate of 5%-30%. Mesenchymal stem cells (MSCs) are multipotent cells, which can promote engraftment and hematopoietic reconstruction by secreting a variety of hematopoietic promoting factors, expressing adhesion molecules supporting hematopoietic stem cells, guiding homing of hematopoietic stem cells and providing hematopoietic microenvironment. At the same time, MSCs can modulate immune responses by affecting the proliferation of T cells and the migration of T cells and DC, inducing the expansion of Treg cells, inhibiting the secretion of antibodies by B lymphocytes, and regulating the secretion of soluble factors such as