This clinical trial is studying the effects of mesenchymal stem cell (MSC) culture supernatant on the prevention and treatment of mucosal injuries in patients undergoing hematopoietic stem cell transplantation (HSCT). HSCT is a common treatment for blood-related cancers and other serious blood disorders. However, many patients experience severe damage to their mucous membranes, including the lining of the mouth, skin, and bladder, due to the high-dose chemotherapy used in the treatment process. These mucosal injuries can cause pain, increase the risk of infection, and lower the patient's quality of life. The purpose of this study is to determine whether MSC culture supernatant can help repair mucosal injuries and improve recovery for these patients. MSC culture supernatant contains substances produced by mesenchymal stem cells that may promote healing and reduce inflammation. These substances could potentially repair tissue without the risks associated with using live cells. Participants in this trial will be randomly assigned to one of two groups: one group will receive standard care, and the other will receive MSC culture supernatant as part of their treatment. The study will look at how well MSC supernatant helps heal mucosal injuries, as well as its safety and any side effects that may occur. The outcomes of this study could lead to new ways to prevent and treat mucosal injuries in patients undergoing HSCT, improving their quality of life during and after treatment. The trial will include 120 patients who have undergone HSCT and experienced mucosal injuries. The study will last approximately five years, from October 2020 to September 2025. Participants will be monitored throughout the trial for safety and effectiveness of the treatment, with follow-up visits scheduled to assess their progress.