Improvements in perinatal emergency medicine have decreased the neonatal mortality rate, however, the incidence of hypoxic ischemic encephalopathy and premature cerebral palsy have increased over time . Conventional rehabilitation treatment for cerebral palsy cannot improve the motor function of patients with moderate-to-severe chronic cerebral palsy [5, 6]. In this study, we did not find any significant improvement in the motor functions of the patients in the control group. However, in the transplantation group, our data indicated that the GMFM scores post-treatment were significantly higher after 3 months compared with the baselines scores, which suggests that the motor recovery effects were accelerated in the transplantation group. In addition, we found that patients in the transplantation group with GMFCS levels IV and V had a better recovery of motor functions. These results provide strong clinical support for MSC-derived NSC-like cells transplantation for the treatment of cerebral palsy, especially for moderate-to-severe chronic cerebral palsy.
The mechanism by which NSCs contribute to motor function recovery remains controversial. Experiments have demonstrated that transplanted NSCs exhibit strong plasticity, can easily integrate with host cells and can establish a stable synaptic connection and become functional substituting nerve cells [26–28]. Additionally, NSCs may produce neurotrophic factors that facilitate the recovery of impaired tissues in the diseased brain region [29–32]. Consistent with these findings, we found that autologous NSC-like cells derived from MSCs could differentiate into neuronal and glial lineages in vitro. Our study was not designed to address the mechanism of NSC functions in vivo, and future experiments are necessary to define the exact mechanism of therapeutic cerebral repair by NSCs.
The safety of the NSC-based cell therapy is another urgent problem. The risk for chromosomal aberrations, neoplastic transformation, increased telomerase activity, or both has been reported for human MSCs following several passages in culture in experimental settings . We used early cultured MSCs (3–4 passage) that displayed normal karyotypes and telomerase activity to induce NSC-like cells. Before each treatment, we confirmed the safety of induced NSC-like cells by telomerase activity evaluation, karyotype analysis and microbiological detection. To our knowledge, there are no clinical data that support the development of neoplasms that are directly related to an autologous MSC inoculum [34, 35]. In this study, we evaluated the safety of MSCs and NSC-like cells in nude mice, and no tumour formation or other complications were found in a long-term (more than 3 months) study. Moreover, allodynia was reported to be a risk of intraspinal neural stem cell transplantation . In this study, we did not find any cases of allodynia or other adverse events during the 6-month follow-up. Therefore, we confirmed that the cells in our study were safe for the patients, however, more long-term follow-up studies may be necessary to further confirm the safety of NSC-like cells.
In this study, we did not find any evidence of accelerated recovery of language function in the transplantation group. Language disorders in children with cerebral palsy are categorized as asophia, anarthria and language developmental delays , which are caused by a motor disturbance of the speech organs due to brain injury. Language recovery is affected by multiple factors . The time period from 7–24 months after birth is important for establishing brain language signal pathways. In this study, all of the patients missed this key phase of language training. Therefore, stem cells combined with language training at an earlier stage may improve the language ability of these patients.
The main limitations of this study include the small sample size and the lack of a randomised, double-blinded, placebo-controlled design. However, we employed an observer-blinded, controlled design to minimize measurement bias. As shown in Figure 3, the baseline characteristics of the patients from the two groups are well matched, and no significant differences were found between the two groups in the comparison of the patient ages, LDQs and GMFM scores at the study onset. This study is the first reported controlled clinical trial of NSC-like cells therapy for chronic cerebral palsy, and our study provides strong clinical evidence that supports stem cell transplantation for the treatment of motor deficits related to cerebral palsy. Further randomised clinical trials are necessary to establish the efficacy of this procedure.