Analysis of Host-Mediated Repair Mechanisms after Human CNS-Stem Cell Transplantation for Spinal Cord Injury: Correlation of Engraftment with Recovery

Abstract

BackgroundHuman central nervous system-stem cells grown as neurospheres (hCNS-SCns) self-renew, are multipotent, and have potential therapeutic applications following trauma to the spinal cord. We have previously shown locomotor recovery in immunodeficient mice that received a moderate contusion spinal cord injury (SCI) and hCNS-SCns transplantation 9 days post-injury (dpi). Engrafted hCNS-SCns exhibited terminal differentiation to myelinating oligodendrocytes and synapse-forming neurons. Further, selective ablation of human cells using Diphtheria toxin (DT) abolished locomotor recovery in this paradigm, suggesting integration of human cells within the mouse host as a possible mechanism for the locomotor improvement. However, the hypothesis that hCNS-SCns could alter the host microenvironment as an additional or alternative mechanism of recovery remained unexplored; we tested that hypothesis in the present study.Methods and FindingsStereological quantification of human cells using a human-specific cytoplasmic marker demonstrated successful cell engraftment, survival, migration and limited proliferation in all hCNS-SCns transplanted animals. DT administration at 16 weeks post-transplant ablated 80.5% of hCNS-SCns. Stereological quantification for lesion volume, tissue sparing, descending serotonergic host fiber sprouting, chondroitin sulfate proteoglycan deposition, glial scarring, and angiogenesis demonstrated no evidence of host modification within the mouse spinal cord as a result of hCNS-SCns transplantation. Biochemical analyses supplemented stereological data supporting the absence of neural stem-cell mediated host repair. However, linear regression analysis of the number of engrafted hCNS-SCns vs. the number of errors on a horizontal ladder beam task revealed a strong correlation between these variables (r = −0.78, p<0.05), suggesting that survival and engraftment were directly related to a quantitative measure of recovery.ConclusionsAltogether, the data suggest that the locomotor improvements associated with hCNS-SCns transplantation were not due to modifications within the host microenvironment, supporting the hypothesis that human cell integration within the host circuitry mediates functional recovery following a 9 day delayed transplant.

Treatment of a Mouse Model of Spinal Cord Injury by Transplantation of Human Induced Pluripotent Stem Cell-Derived Long-Term Self-Renewing Neuroepithelial-Like Stem Cells

“…3D-3F), even though endogenous or transplanted NSCs in the injured spinal cord have been reported by others to differentiate preferentially into the glial lineage [42,43]. Recent studies have indicated that neurons derived from transplanted human NSCs can integrate into the injured spinal cord and form synaptic connections with host neurons [33,34]. We therefore took advantage of the tendency of our hiPS-lt-NES cells to differentiate into neurons and tried to apply these cells to reconstruction of the injured spinal cord.…”

“…Indeed, the sources and methods of induction of NSCs are critical for differentiation and tumor formation [33,53]. Neurosphere cultures are heterogeneous and sensitive to variations in methodological procedures [12], whereas monolayer cell cultures give rise to more homogeneous population [13,14].…”

“…Recent studies have revealed that local endogenous and transplant-derived neurons can form new neuronal circuits and make synaptic connections after SCI [32][33][34]. To determine whether disrupted CSTs were reconstructed by forming a local neuronal relay, we injected WGA-expressing adenoviruses into the motor cortex of the hind limb area at 12 weeks after SCI.…”

Adult human neural stem cell therapeutics: Current developmental status and prospect

“…Treatment mechanism study indicated that neurons derived from transplanted stem cells integrated into the host neuronal circuitry and mediated functional recovery [19,67] . On the other hand, the functional recovery after NSC transplantation into spinal cord injury models was proportional to the number of transplanted stem cell-derived oligodendrocytes and the amount of regenerated myelin [68] .…”

Cell Therapy of Stroke and Spinal Cord Injury Complications

“…Кли-нические испытания проводились на основе предклинических исследований, показавших, что стволовые клетки, выделенные из фе-тального мозга человека, могут дифференци-роваться в миелин-продуцирующие олиго-дендроциты и нейроны, формирующие новые синапсы, что приводит к функциональному восстановлению на моделях ПСМТ грызунов [54][55][56][57][58]. Клиническое исследование было на-чато в марте 2011 года и в настоящее время завершено.…”