1.What are stem cells? Stem cells are a non-specific cell type with self-renewal and differentiation potential, which can differentiate into a variety of tissue cells across lineages and germ layers under certain conditions, and can even differentiate into a variety of tissues and organs, which is called “universal cells” in the medical field. 2.What are the sources of stem cells? Stem cells can be obtained from four common sources: embryo (mainly used for basic research), placenta and its appendages, bone marrow, and adult tissue (including peripheral blood). Currently, there are three main sources of stem cells used in clinical practice: autologous peripheral blood, autologous bone marrow, and placenta and its appendages. 3.What diseases can be treated by stem cell transplantation? Stem cells have strong plasticity and can differentiate into a variety of tissue cells across lineages and germ layers. The main diseases treated by stem cell technology include: (1) Parkinson’s disease; (2) cerebral infarction, cerebral hemorrhage, traumatic brain injury, paraplegia after spinal cord injury; (3) amyotrophic lateral sclerosis, spinal muscular atrophy, multiple sclerosis; (4) Alzheimer’s disease, cerebral hypoplasia, cerebral atrophy, ataxia; (5) (6) cerebral palsy, pediatric ischemic-hypoxic encephalopathy, mental retardation; (7) neurological diseases such as myelitis sequelae; (8) diabetes mellitus and its complications; (9) femoral head necrosis; (10) optic nerve hypoplasia, etc. 4.What are the ways of stem cell transplantation treatment? There are four commonly used routes: interventional route, local implantation, intravenous route and lumbar puncture route. 5.What are the contraindications of stem cell transplantation? Stem cell transplantation technology is an emerging cellular therapy, which is currently a relatively high safety treatment. Contraindications for stem cell transplantation include: ① Highly allergic or with a history of severe allergy; ② Shock or systemic failure with abnormal vital signs and uncooperative examination; ③ Systemic infection or serious local infection; ④ Combined dysfunction of important organs such as heart, lung, liver and kidney; ⑤ Positive serological tests such as AIDS, hepatitis B, syphilis, etc. (6) Very few people with high expectations or unrealistic requirements. 6.What are the advantages of stem cell transplantation therapy? Stem cell transplantation has many advantages, such as: convenient collection, no anesthesia, less pain; fast reconstruction of hematopoietic function after transplantation, early recovery of immune function, low and light complications of infection and bleeding; solving the problem of bone marrow suppression during tumor chemotherapy, maximizing the dose of chemotherapy, and prolonging the life of patients with mid- to late-stage cancer, etc. 7.Does stem cell transplantation require mating? Will there be rejection reaction? What are the side effects? Stem cell transplantation is divided into different stem cell transplantation methods according to the type, such as hematopoietic stem cells, which must be tissue-matched, and MSC transplantation, which can be considered without tissue-matching because of the low immunogenicity of MSC transplantation. Therefore, the patient’s own immune system will not strongly reject it, thus avoiding immune rejection and allergic reactions caused by organ transplantation. At present, stem cell research has completed a full set of preclinical safety tests on stem cells, including acute toxicity test, long-term toxicity test, tumorigenicity test, teratogenicity test, local irritation test, fever test and immunotoxicity test, and the results show that the clinical application of stem cells is safe and non-toxic. In the clinical research, after a large number of clinical case studies, stem cell therapy has no serious adverse reactions except for a very small number of patients with mild fever and headache, which indicates that its clinical application is safe. 8.Is there any after-effects after stem cell transplantation? What is the duration of the effect after treatment? There are no obvious sequelae after stem cell transplantation, and the stem cells will survive in the patient’s body for a long time after transplantation, but their efficacy varies according to the original disease. For patients whose original pathogenic factors are clear, it may be effective for a long time, but for patients whose pathogenic factors persist, it is difficult to maintain the efficacy for a long time due to the continuous destruction of the pathogenic factors, but it can slow down the development of the disease. 9.When will I see the curative effect after stem cell transplantation? The time required for stem cells to develop into mature tissue cells varies depending on the disease and the current stage of the disease. The process of migration and differentiation in vivo is very complex and we cannot fully predict the exact time for each individual. It is a process from quantitative to qualitative change, some patients have some significant improvement in symptoms after one transplant, but usually show increasing efficacy after 2-3 months after transplantation, and then this process takes 3 months or more after discharge from the hospital.