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Cell–Cell Contact Mediates Gene Expression and Fate Choice of Human Neural Stem/Progenitor Cells

Transplantation of Neural Stem/Progenitor Cells (NPCs) is a promising regenerative strategy to promote neural repair following injury and degeneration because of the ability of these cells to proliferate, migrate, and integrate with the host tissue. Precise in vitro control of NPC proliferation without compromising multipotency and differentiation ability is critical in stem cell maintenance. This idea was highlighted in recent clinical trials, where discrepancies in NPC culturing protocols produced inconsistent therapeutic benefits. Of note, cell density plays an important role in regulating the survival, proliferation, differentiation, and fate choice of stem cells. To determine the extent of variability produced by inconsistent culturing densities, the present study cultured human-induced pluripotent NPCs (hiPSC-NPCs) at either a low or high plating density. hiPSC-NPCs were then isolated for transcriptomic analysis or differentiation in vitro. Following sequencing analysis, genes involved in cell–cell contact-mediated pathways, including Hippo-signaling, NOTCH, and WNT were differentially expressed. Modulation of these pathways was highly associated with the regulation of pro-neuronal transcription factors, which were also upregulated in response to higher-density hiPSC-NPC culture. Moreover, higher plating density translated into a greater neuronal and less astrocytic differentiation in vitro. This study highlights the importance of precisely controlling culture conditions during the development of NPC transplantation therapies.

Regenerative Therapies for Spinal Cord Injury

Spinal cord injury (SCI) is a serious problem that primarily affects younger and middle-aged adults at its onset. To date, no effective regenerative treatment has been developed. Over the last decade, researchers have made significant advances in stem cell technology, biomaterials, nanotechnology, and immune engineering, which may be applied as regenerative therapies for the spinal cord. Although the results of clinical trials using specific cell-based therapies have proven safe, their efficacy has not yet been demonstrated. The pathophysiology of SCI is multifaceted, complex and yet to be fully understood. Thus, combinatorial therapies that simultaneously leverage multiple approaches will likely be required to achieve satisfactory outcomes. Although combinations of biomaterials with pharmacologic agents or cells have been explored, few studies have combined these modalities in a systematic way. For most strategies, clinical translation will be facilitated by the use of minimally invasive therapies, which are the focus of this review. In addition, this review discusses previously explored therapies designed to promote neuroregeneration and neuroprotection after SCI, while highlighting present challenges and future directions. Impact Statement To date there are no effective treatments that can regenerate the spinal cord after injury. Although there have been significant preclinical advances in bioengineering and regenerative medicine over the last decade, these have not translated into effective clinical therapies for spinal cord injury. This review focuses on minimally invasive therapies, providing extensive background as well as updates on recent technological developments and current clinical trials. This review is a comprehensive resource for researchers working towards regenerative therapies for spinal cord injury that will help guide future innovation.

Clinical Outcomes from a Multi-Center Study of Human Neural Stem Cell Transplantation in Chronic Cervical Spinal Cord Injury

Human neural stem cell transplantation (HuCNS-SC^®) is a promising central nervous system (CNS) tissue repair strategy in patients with stable neurological deficits from chronic spinal cord injury (SCI). These immature human neural cells have been demonstrated to survive when transplanted in vivo, extend neural processes, form synaptic contacts, and improve functional outcomes after experimental SCI. A phase II single blind, randomized proof-of-concept study of the safety and efficacy of HuCNS-SC transplantation into the cervical spinal cord was undertaken in patients with chronic C5-7 tetraplegia, 4-24 months post-injury. In Cohort I (n = 6) dose escalation from 15,000,000 to 40,000,000 cells was performed to determine the optimum dose. In Cohort II an additional six participants were transplanted at target dose (40,000,000) and compared with four untreated controls. Within the transplant group, there were nine American Spinal Injury Association Impairment Scale (AIS) B and three AIS A participants with a median age at transplant of 28 years with an average time to transplant post-injury of 1 year. Immunosuppression was continued for 6 months post-transplant, and immunosuppressive blood levels of tacrolimus were achieved and well tolerated. At 1 year post-transplantation, there was no evidence of additional spinal cord damage, new lesions, or syrinx formation on magnetic resonance (MR) imaging. In summary, the incremental dose escalation design established surgical safety, tolerability, and feasibility in Cohort I. Interim analysis of Cohorts I and II demonstrated a trend toward Upper Extremity Motor Score (UEMS) and Graded Redefined Assessment of Strength, Sensibility, and Prehension (GRASSP) motor gains in the treated participants, but at a magnitude below the required clinical efficacy threshold set by the sponsor to support further development resulting in early study termination.

How to construct an optimal interim report: What the data monitoring committee does and doesn’t need to know

Background:

Data monitoring committees for randomized clinical trials have the responsibility of safeguarding interests of trial participants. To do so, the data monitoring committee must receive reports on safety and efficacy to assess risk/benefit and on trial conduct to ensure that the study can achieve its goals. This article outlines the key components of reports to the data monitoring committee and the important role of the unblinded statistician in preparing those reports.

Methods:

Most data monitoring committee meetings include open and closed sessions. For each session, there is a report of interim results. The open session is attended by the sponsor and lead investigators, including the statistician(s) responsible for the trial design. These investigators are blinded to the interim treatment comparisons. The closed session is attended by the data monitoring committee members and by the statistician(s) who prepared the closed report. These individuals are unblinded to interim treatment comparisons and therefore are not involved in study design changes. The optimal content of data monitoring committee reports and qualifications of the unblinded statistician(s) are discussed.

Reports:

Open reports should include responses to data monitoring committee recommendations, a synopsis of the protocol, a review of the protocol history and amendments, and information on enrollment, baseline characteristics, completeness of follow-up, and data quality. The open report is also a vehicle through which the sponsor and investigators should inform the data monitoring committee of relevant external information. Data in the open report are pooled over the treatment groups. The open report should not include data summaries by treatment group. The closed report should include a written summary with references to key tables and figures and methods used to prepare them. Tables and figures should summarize baseline characteristics, follow-up completeness, treatment adherence, and major safety and efficacy outcomes by treatment group. Text summaries should accompany the tables and figures. The data monitoring committee monitoring history (e.g. treatment differences at previous meetings) should be summarized. The unblinded statistician preparing the closed report should be familiar with the protocol and data collection plan and be capable of customizing the report to the current stage of the trial. This includes anticipating questions that may arise during the data monitoring committee review and pro-actively including data summaries to address these questions.

Conclusions:

There is considerable variation in the quality of open and closed data monitoring committee reports. Open and closed data monitoring committee reports should be concise, up to date, and informative. To achieve this, unblinded statisticians responsible for preparing closed data monitoring committee reports should be familiar with the statistical methods, the trial protocol, and the data collection plan. They should be capable of anticipating questions from the data monitoring committee and responding to requests for additional analyses.

Cellular therapy for traumatic neurological injury

Neurological injury is the primary lethal mechanism of injury in children, and the primary etiology of long-term disability after trauma. Laboratories and clinical/translational teams have sought to develop stem/progenitor cell therapies to improve recovery in a clinical setting in which there is no significant reparative option. While none of these treatments are currently standard therapeutics, phase IIb clinical trials are underway in both adults and children in severe traumatic brain injury (TBI) and phase I/IIa trials in spinal cord injury. This review will characterize the cell therapy strategies: cell replacement and tissue integration vs. immunomodulation/enhanced endogenous tissue repair. TBI is somewhat different from other central nervous system injuries (spinal cord injury and stroke), in that TBI is a diffuse injury, whereas spinal cord injury and stroke are anatomically discrete. Importantly, this drives cell therapy approaches, as TBI is less apt to be treatable with a local cell replacement intervention. More localized injuries may be more amenable to local approaches and cell replacement to bridge focal gaps. This review focuses on a few reports in the field that highlight areas of progress, but is not intended to be a comprehensive survey of the state of regenerative medicine for neurological injuries.