Hematopoietic stem cell microtransplantation: current situation and challenges

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) stands as a cornerstone in the treatment of hematological malignancies, recognized for its remarkable efficacy. However, the persistent challenge of graft-versus-host disease (GVHD) continues to represent a significant barrier, often being the leading cause of nonrelapse mortality after allo-HSCT. To address this limitation, hematopoietic stem cell microtransplantation (MST) has emerged as a novel therapeutic strategy that synergistically combines chemotherapy, allo-HSCT, and cellular immunotherapy. This innovative approach is designed to retain the patient's immune function, promote the establishment of microchimerism, and achieve a potent graft-versus-tumor (GVT) response, all while significantly minimizing the risk of GVHD. MST has primarily been applied in the treatment of hematological malignancies, where it has demonstrated promising outcomes, including marked improvements in complete remission rates, overall survival rates, and progression-free survival rates. Moreover, MST facilitates hematopoietic recovery, decreases the likelihood of infections, and reduces the incidence of GVHD, thus contributing to an improved quality of life for patients. A deeper and more comprehensive understanding of MST's mechanisms could enhance its clinical utility and integration into standard treatment protocols. This review aims to explore the underlying mechanisms, current clinical applications, and challenges of MST, shedding light on its potential role in advancing the management of hematological malignancies.