Release date: 2016-04-26 The clinical study of MSC began in 1995 when Professor Caplan extracted and isolated these adherent cells from the bone marrow of patients with hematologic malignancies, and then returned to the patient to observe the clinical effect and prove the safety of clinical application [1]. Although clinical trials have reported that MSC causes cardiotoxicity, it is characterized by transient arrhythmia, with an incidence of 7% (2 of 30 patients) [2-4]. In a non-randomized controlled trial (hematopoietic stem cell transplantation), 3 of 100 patients in the MSC-treated group and 8 of 100 patients in the control group died due to infection after treatment [5]. However, in a number of randomized controlled clinical trials, statistical analysis revealed no difference in infection rates between the MSC-treated and control groups, and it was clearly suggested that MSC treatment did not increase the risk of infection, and that the MSC-treated and control groups were in dyscrasia and There is no difference in tumor formation [6-9]. Long-term observations have not found that patients increase microbial infection and mesenchymal stem cell tumorigenesis [10-12]. Although multiple randomized controlled clinical trials have demonstrated the safety of MSCs in clinical applications (no tumorigenicity), although multiple countries have approved MSC marketing (see Figure 1 below); the US FDA has not approved marketing, which may have led to many people. There is still concern about the safety of MSC. In fact, the US FDA does not approve Osiris' Prochymal (Bone Marrow MSC) market, not for safety reasons, but because its Phase III clinical trial for treating GVHD failed to meet expectations. figure 1 After the fertilized egg has developed through the blastocyst stage, there is no embryonic stem cell; in the natural life of the human body, there is no induced pluripotent stem cell (iPS); however, there are MSC and hematopoietic stem cells (HSC) in the human body. How much information can this phenomenon tell us? First, MSC is a type of cell that must exist in the human body. At present, tumor cells have not been found or proven to be derived from MSC. Even some scholars believe that cancer stem cells are not derived from normal stem cells [13, 14], then it can be considered that MSCs in their own bodies do not become cancer cells or cancer cells. As to whether MSC promotes the growth of tumor cells? Without the presence of the immune system, MSCs secrete abundant nutrient cytokines, which greatly increases the growth of tumor cells. But in the presence of the immune system, can exogenous MSCs have a tumor-promoting effect? The relationship between the immune system, mesenchymal stem cells, and tumor cells/cancer cells requires in-depth study (see Figure 2 below). figure 2 Second, MSC is not equivalent to an immunosuppressive agent. MSC has been widely distributed in humans, and randomized controlled clinical trials have shown that the application of MSC does not increase the infection rate, which indicates that MSC in human body does not play a role in suppressing immune response. Immunosuppressive function is only one of the effects of MSC on the immune system. Features. Our current understanding of MSC immune function needs to be further deepened. Although the International Cell Therapy Association has proposed immunomodulatory function analysis as a cell product release standard (or evaluation standard) for MSC clinical studies [15], this standard cannot be quantified and is not operational. Third, is the safety of MSC after in vitro expansion equivalent to MSC in vivo? Without MSCs expanded in vitro, the cells themselves are safe and harmless unless they have a genetic defect. The greatest risk of in vitro expansion is genetic mutation. One research team found that when bone marrow MSCs were cultured in vitro for 18 generations, gene mutations and chromosomal abnormalities occurred [16]. Another team found that umbilical cord MSCs were cultured in vitro for 30 generations before chromosomal abnormalities occurred [17]. We can't conclude from these two studies that bone marrow MSCs cultured in vitro are more prone to chromosomal abnormalities than umbilical cord MSCs, because the culture system may be different; but it also shows that MSCs in the culture in vitro are too high (more than 10 generations) Will cause chromosomal abnormalities. Fourth, the safety of the MSC formulation product (injection) is different from the safety of the MSC cells themselves. MSC preparation products, in addition to MSC, also contain other excipients (buffers), such as physiological saline; also need to consider the safety hazards caused by the cultivation process. Studies have shown that the use of fetal bovine serum (FBS) to culture MSC may increase the immunogenicity of MSC [18, 19]. Fetal bovine serum is widely used in in vitro expansion culture of MSC. Considering the large amount of heterologous protein in fetal bovine serum, we should also reduce the fetal bovine serum residue in MSC cell preparation as much as possible. Whether serum-free medium can meet the needs of MSC industrialization is worthy of further study. More notably, MSC cell preparations containing dimethyl sulfoxide (DMSO, a reagent that must be used for cryopreservation) can significantly increase toxic side effects and cause hypersensitivity reactions [20-22]. If the endotoxin content in the MSC preparation exceeds the standard, it is easy to cause fever. Some scholars have analyzed the literature of a large number of clinical trials (Meta-Analysis), and found that MSC input therapy only has a certain correlation with fever, but it is not necessary to be associated with adverse reactions reported in other literatures. It is considered that MSC treatment is safe. [23]. The fever caused by MSC treatment is closely related to the residual amount of "fetal calf serum, dimethyl sulfoxide and endotoxin" of MSC preparation products. Fetal bovine serum residues, dimethyl sulfoxide and endotoxin are closely related to the production process. The cell viability of MSC preparation products is too low, and there are too many dead cells. These dead cells and cell debris can cause fever. In addition, attention should be paid to the presence of microbial contamination during MSC collection and the introduction of exogenous microbial contamination during the culture process. Microbial contamination is also a high risk factor for MSC formulation products. Fifth, the metabolism of allogeneic MSCs into the body. At present, the metabolic kinetics of MSC in the body are derived from animal experiments. Since MSC has the characteristics of tissue and organ sites that are chemotactic to damaged, the metabolic dynamics of MSC in the healthy body and the diseased body are not the same. The source of MSC is also an influencing factor. For example, the cell volume of bone marrow MSC is larger than that of cord blood MSC, which results in the retention of bone marrow MSC in the lungs more than that of cord blood MSC [24]. The species of experimental animals also affect the metabolic dynamics of MSCs. For example, dogs without lung injury, MSCs stay in the lungs for about 1 day [25], but MSCs can stay in the lungs of healthy rats for 3 days [26] After giving radioactive injury to the lungs of rats, the MSC stayed in the lungs for an additional 7 days [26]. Studies have shown that MSCs are trapped in the lungs, and the lung environment can activate MSCs to express TSG-6, which is beneficial for MSCs to exert therapeutic effects [27]. After the MSC passes through the lungs, it will circulate blood to other organs at any time, such as liver, kidney, and spleen [25]. The survival time of allogeneic MSCs in mice with intact immune system is about 22 days. The survival time of MSCs in mice is inversely proportional to the degree of defects of immune cells in mice, that is, the survival time of MSCs in NOD/SCID mice is the most. Long, Nude nude mice followed, normal healthy mice were the shortest [28]. Sixth, the choice of indications. Since MSC is widely present in the human body, can all diseases that occur in the human body be treated with MSC? There are dozens of diseases or indications for the MSC clinical trial (stage I-III) registered on the clinicaltrials website (see Figure 3 below), many of which have published the results of clinical studies. So what is the basis for the selection of indications for MSC treatment? The stem cell biological function of MSC determines the efficacy of MSC (therapeutic regimen is also important), so it is very important to study the function of MSC in depth. Early differentiation of MSCs is thought to be suitable for the treatment of certain diseases, but the therapeutic mechanism of MSCs is more likely to secrete cytokines [29-34]. However, there is currently no data or article supporting the combination of bioactive molecules to replace MSCs for the treatment of diseases; and some of the advantages of MSCs are that biologically active molecules do not have, such as low immunogenicity, chemotaxis, localized sites of damage, and tissues. Cell-cell crosstalk of organs, etc. image 3 Seventh, what kind of situation is suitable for autologous MSC treatment. MSC exists in many tissues and organs of the body, including bone marrow, fat, thymus, and peripheral blood. The human body has an age, the organs and organs have an age, and the stem cells also have an age. The growth rate of older MSCs has dropped significantly [35, 36]. When older MSCs are cultured in vitro, the cell bodies of the cells are much larger than those of younger ones [36, 37]. The increase of cell body is closely related to cell senescence [38]. There are three changes in MSCs that demonstrate surface aging: decreased quality, decreased differentiation/regeneration capacity, and reduced migration capacity [39]. For a detailed discussion of this part, refer to the public number "The patient's autologous stem cells have functional defects and are not suitable for autologous transplantation." Patients with certain diseases may have some functional defects (see Figure 4 below). Whether the defects of these functions are serious enough to affect the efficacy, further research is needed. Figure 4 to sum up: Although MSC has been approved for marketing in some countries, security and effectiveness are officially and market-recognized; however, listing does not imply termination of MSC research. The fascination of MSC is that she always gives us some surprises. What we have to do is to study the mystery behind these surprises. Source: Mesenchymal stem cells NINGBO AUTRENDS INTERNATIONAL TRADE CO., LTD , https://www.metests.com