Treatment of Severe Adult Traumatic Brain Injury Using Bone Marrow Mononuclear Cells

Abstract

Preclinical studies using bone marrow derived cells to treat traumatic brain injury have demonstrated efficacy in terms of blood-brain barrier preservation, neurogenesis, and functional outcomes. Phase 1 clinical trials using bone marrow mononuclear cells infused intravenously in children with severe traumatic brain injury demonstrated safety and potentially a central nervous system structural preservation treatment effect. This study sought to confirm the safety, logistic feasibility, and potential treatment effect size of structural preservation/inflammatory biomarker mitigation in adults to guide Phase 2 clinical trial design. Adults with severe traumatic brain injury (Glasgow Coma Scale 5-8) and without signs of irreversible brain injury were evaluated for entry into the trial. A dose escalation format was performed in 25 patients: 5 controls, followed 5 patients in each dosing cohort (6, 9, 12 ×10⁶ cells/kg body weight), then 5 more controls. Bone marrow harvest, cell processing to isolate the mononuclear fraction, and re-infusion occurred within 48 hours after injury. Patients were monitored for harvest-related hemodynamic changes, infusional toxicity, and adverse events. Outcome measures included magnetic resonance imaging-based measurements of supratentorial and corpus callosal volumes as well as diffusion tensor imaging-based measurements of fractional anisotropy and mean diffusivity of the corpus callosum and the corticospinal tract at the level of the brainstem at 1 month and 6 months postinjury. Functional and neurocognitive outcomes were measured and correlated with imaging data. Inflammatory cytokine arrays were measured in the plasma pretreatment, posttreatment, and at 1 and 6 month follow-up. There were no serious adverse events. There was a mild pulmonary toxicity of the highest dose that was not clinically significant. Despite the treatment group having greater injury severity, there was structural preservation of critical regions of interest that correlated with functional outcomes. Key inflammatory cytokines were downregulated. Treatment of severe, adult traumatic brain injury using an intravenously delivered autologous bone marrow mononuclear cell infusion is safe and logistically feasible. There appears to be a treatment signal as evidenced by central nervous system structural preservation, consistent with previous pediatric trial data. Inflammatory biomarkers are downregulated after cell infusion. Stem Cells 2016 Video Highlight: https://youtu.be/UiCCPIe-IaQ Stem Cells 2017;35:1065-1079.

Keywords: adult human bone marrow; adult stem cells; bone marrow stromal cells; cellular therapy; clinical trials; diffusion tensor imaging; traumatic brain injury.

Figure 1. CONSORT Diagram for Trial Enrollment/Participation

Patients were screened with a 10-15X ratio of screened to enrolled. This has logistical implications for trial design. Long term follow-up was exceptionally strong for an acute trauma study (normally approximately30-50%). The Flow diagram shows how patients are identified, enrolled and treated within 48 hours, with a measured mean of approximately 36 hours.

Figure 2. Global Change in White Matter Volume

These data graphically represent the changes in WM volume by treatment group (Panel A), the individual patients in the high dose group with their corresponding computed tomography images explaining their outlier status (Panel B) and the pooled comparisons of treated vs. controls (Panel C). Supra-tentorial White Matter Volume is demonstrated with and without the outlier patients 19 and 20. Treated patients show greater supra-tentorial WM volume preservation compared to Controls.

Figure 3. Corpus Callosum Fractional Anisotropy and Mean Diffusivity

These data graphically display the changes in FA and MD in the Control and Treated groups in a dose dependent manner (Panels A), High dose individual patients (Panel B) and pooled comparisons (Panel C). FA is a summary measure of microstructural integrity. Oversimplified, High FA values are a surrogate measure of coherent, tightly packed and myelinated fibers. Mean diffusivity is an inverse measure of cell membrane density and is sensitive to edema and necrosis (higher FA is “good”, and lower MD is “good”). FA is higher in the treated groups except in the outliers as demonstrated in Panel B. MD is lower in the low and medium dose groups, and again the higher dose outliers skew those results.

Figure 4. Corticospinal tract Fractional Anisotropy, Mean Diffusivity and Radial Diffusivity

These data demonstrate the increase in FA over time in the treated group compared to the decrease over time in the control group. Conversely, the diffusivity measurements show progression in the control group and improvement in the treated group.

Figure 5. Inflammatory Cytokine Array

A panel of pro and anti-inflammatory cytokines were measured in plasma. Peak levels within the first 96 hours post-injury were considered the physiological maximal response, and the 6 month follow-up levels were considered “baseline”. True un-injured baseline/pre-treatment cytokine data cannot be obtained. Pre-treatment and peak levels were also analyzed and presented. The data show a significant decrease in IL-1β, and IFN-γ in the high dose group and an apparent dose-dependent downward trend in those cytokines as well as TNF-α. The anti-inflammatory cytokine IL-10 was decreased in the high dose group with a dose dependent downward trend in IL-4.