Shekar N. Kurpad

Allodynia limits the usefulness of intraspinal neural stem cell grafts; directed differentiation improves outcome

Several studies have reported functional improvement after transplantation of neural stem cells into injured spinal cord. We now provide evidence that grafting of adult neural stem cells into a rat thoracic spinal cord weight-drop injury improves motor recovery but also causes aberrant axonal sprouting associated with allodynia-like hypersensitivity of forepaws. Transduction of neural stem cells with neurogenin-2 before transplantation suppressed astrocytic differentiation of engrafted cells and prevented graft-induced sprouting and allodynia. Transduction with neurogenin-2 also improved the positive effects of engrafted stem cells, including increased amounts of myelin in the injured area, recovery of hindlimb locomotor function and hindlimb sensory responses, as determined by functional magnetic resonance imaging. These findings show that stem cell transplantation into injured spinal cord can cause severe side effects and call for caution in the consideration of clinical trials.

Pain with no gain: allodynia following neural stem cell transplantation in spinal cord injury.

Transplantation of neural stem cells (NSCs) in the injured spinal cord has been shown to improve functional outcome; however, recent evidence has demonstrated forelimb allodynia following transplantation of embryonic NSCs. The aim of this study was to investigate whether transplantation of murine C17.2 NSCs alone or transfected with glial-derived neurotrophic factor (C17.2/GDNF) would induce allodynia in transplanted spinal cord-injured animals. One week after a T8-level spinal cord injury (SCI), C17.2, C17.2/GDNF or normal saline was injected at the injury site. Locomotor function and sensory recovery to thermal and mechanical stimuli were then measured. Spinal cords were processed immunohistochemically at the injury/transplantation site for characterization of NSC survival and differentiation; and at the cervicothoracic level for calcitonin gene-related peptide (CGRP), a neuropeptide expressed in dorsal horn nocioceptive neurons, and growth-associated protein-43 (GAP43), a marker of neuronal sprouting. Locomotor function was not significantly improved following NSC transplantation at any time (P >0.05). Significant forelimb thermal and mechanical allodynia were observed following transplantation with both NSC populations (P <0.05). The C17.2 and C17.2/GDNF NSCs survived and differentiated into a predominately astrocytic population. Calcitonin gene-related peptide and GAP43 immunoreactivity significantly increased and co-localized in cervicothoracic dorsal horn laminae I-III following C17.2 and C17.2/GDNF transplantation. This study demonstrated that murine C17.2 NSCs differentiated primarily into astrocytes when transplanted into the injured spinal cord, and resulted in thermal and mechanical forelimb allodynia. Sprouting of nocioceptive afferents occurred rostral to the injury/transplantation site only in allodynic animals, suggesting a principal role in this aberrant pain state. Further, a difference in the degree of allodynia was noted between C17.2- and C17.2/GDNF transplant-treated groups; this difference correlated with the level of CGRP/GAP43 immunoreactivity and sprouting observed in the cervicothoracic dorsal horns. Both allodynia- and CGRP/GAP43-positive afferent sprouting were less in the C17.2/GDNF group compared to the C17.2 group, suggesting a possible protective or analgesic effect of GDNF on post-injury neuropathic pain.

Diffusion Tensor MR Imaging in Chronic Spinal Cord Injury

BACKGROUND AND PURPOSE: Diffusion tensor MR imaging is emerging as an important tool for displaying anatomic changes in the brain after injury or disease but has been less widely applied to disorders of the spinal cord. The aim of this study was to characterize the diffusion properties of the entire human spinal cord in vivo during the chronic stages of spinal cord injury (SCI). These data provide insight into the structural changes that occur as a result of long-term recovery from spinal trauma. MATERIALS AND METHODS: Thirteen neurologically intact subjects and 10 subjects with chronic SCI (>4 years postinjury) were enrolled in this study. A single-shot twice-refocused spin-echo diffusion-weighted echo-planar imaging pulse sequence was used to obtain axial images throughout the entire spinal cord (C1-L1) in <60 minutes. RESULTS: Despite heterogeneity in SCI lesion severity and location, diffusion characteristics of the chronic lesion were significantly elevated compared with those of uninjured controls. Fractional anisotropy was significantly lower at the chronic lesion and appeared dependent on the completeness of the injury. Conversely, mean diffusivity measurements in the upper cervical spinal cord in subjects with SCI were significantly lower than those in controls. These trends suggest that the entire neuraxis may be affected by long-term recovery from spinal trauma. CONCLUSION: These results suggest that diffusion tensor imaging may be useful in the assessment of SCI recovery.

Diffusion Tensor MR Imaging of the Neurologically Intact Human Spinal Cord

BACKGROUND AND PURPOSE: The aim of this study was to characterize the diffusion properties of the entire human spinal cord in vivo. These data are essential for comparisons to pathologic conditions as well as for comparisons of different pulse sequence design parameters aimed to reduce scan time and more accurately determine diffusion coefficients. MATERIALS AND METHODS: A total of 13 neurologically intact subjects were enrolled in this study. A single-shot, twice-refocused, spin-echo, diffusion-weighted, echo-planar imaging (EPI) pulse sequence was used to obtain axial images throughout the entire spinal cord (C1–L1) in 45 minutes. RESULTS: Diffusion images indicated slight geometric distortions; however, gray and white matter contrast was observed. All measurements varied across the length of the cord. Whole cord diffusion coefficients averaged 0.5–1.3 × 10−3 mm2/s depending on orientation, mean diffusivity (MD) averaged 0.83 ± 0.06 × 10−3 mm2/s, fractional anisotropy (FA) averaged 0.49 ± 0.05, and volume ratio (VR) averaged 0.73 ± 0.05. CONCLUSION: This study provided normative diffusion values for the entire spinal cord for use in comparisons with pathologic conditions as well as improvements in pulse sequence design.

In vitro and in vivo characterization of neurally modified mesenchymal stem cells induced by epigenetic modifiers and neural stem cell environment.

Mesenchymal stem cell (MSC)-mediated tissue regeneration is a promising strategy to treat several neurodegenerative diseases and traumatic injuries of the central nervous system. Bone marrow MSCs have great potential as therapeutic agents, since they are easy to isolate and expand and are capable of producing various cell types, including neural cells. Recently we developed a highly efficient methodology to produce neural stem-like and neural precursor-like cells from mice bone marrow-derived MSCs that eventually differentiate into neuronal- and glial-like cells in vitro. The aim of this study is to further elucidate neural expression profile of neurally induced mesenchymal stem cells (NI-MSCs) and their ability to retain neural differentiation potential when grafted into the intact spinal cord of rats. To this end, we further characterized in vitro and in vivo properties of NI-MSCs by immunocytochemistry, Western blot, ELISA, and immunohistochemistry. Immunocytochemical data demonstrated that NI-MSCs express several mature neural markers such as B3T, GFAP MAP-2, NF-200, and NeuN, which were confirmed through Western blot. ELISA data showed that NI-MSCs release nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF). In vivo studies demonstrated that grafted NI-MSCs survived after transplantation into intact spinal cord and produced cells that expressed neural markers. All these data suggest that neurally modified MSCs, induced by recently developed methodology, could be a potential source of cells to replace damaged neurons and glia in injured spinal cord, and/or to promote cell survival and axonal growth of host tissue.

Anterior lumbar interbody fusion for treatment of failed back surgery syndrome: an outcome analysis.

OBJECTIVEAnterior lumbar interbody fusion (ALIF) has gained popularity for the treatment of degenerative disease of the lumbar spine. In this report, we present our experience with the ALIF procedure for treatment of failed back surgery syndrome (FBSS) in a noncontrolled prospective cohort. METHODSIn a 2-year period, we treated patients diagnosed with FBSS with ALIF. Clinical and radiological outcomes were recorded in a prospective, nonrandomized, longitudinal manner. Neurological, pain, and functional outcomes were measured preoperatively and 12 months after surgery. Operative data, perioperative complications, and radiological and clinical outcomes were recorded. RESULTSThirty-three patients with a preoperative diagnosis of FBSS, with degenerative disc disease (n = 17), postsurgical spondylolisthesis (n = 13), or pseudarthrosis (n = 3), underwent ALIF. Back pain, leg pain, and functional status improved significantly, by 76% (P < 0.01), 80% (P < 0.01), and 67% (P < 0.01), respectively. CONCLUSIONOn the basis of our results, we found ALIF to be a safe and effective procedure for the treatment of FBSS for selected patients.

Bioresorbable Fixation for Congenital Pediatric Craniofacial Surgery: A 2-Year Follow-Up

We describe our experience with the use of a polymeric biodegradable system for the correction of congenital pediatric craniofacial malformations. These fixation methods present several advantages over conventional metallic fixation systems. Our series consists of 51 patients that underwent craniofacial surgery, 46 for craniosysostosis, and 5 for encephalocele. The mean age of the patients was 3 years (median age 9 months). Patients with coronal or metopic craniosynostosis underwent a bifrontal craniotomy and anterior cranial vault and orbital reconstruction. Three patients with late sagittal synostosis underwent cranial vault reconstruction in two stages. Encephalocele defects were repaired with osteotomies, and/or onlay bone graft. Lactosorb (Lorenz Biomet, Warsaw, Ind.) plates (cut from a prefabricated mesh) and screws were employed using established fixation techniques. Cranial bone was the source of all bone graft when required. Pre- and postoperative clinical, radiographic and photographic examinations were performed on all patients. At 2 years follow-up, no evidence of infection, erythema, extrusion, instability of the bony fragments or relapse has been noted. The plates themselves were universally impalpable by the one year follow-up examination. The results in this series support the use of resorbable fixation systems in the correction of congenital craniofacial deformities.

Ex vivo diffusion tensor imaging and quantitative tractography of the rat spinal cord during long-term recovery from moderate spinal contusion

To characterize DTI metric changes throughout the length of the entire spinal cord from the acute through chronic stages of spinal cord injury (SCI).

Lesion growth and degeneration patterns measured using diffusion tensor 9.4-T magnetic resonance imaging in rat spinal cord injury.

OBJECT Using diffusion tensor MR imaging, the authors conducted a study to explore lesion growth and degeneration patterns, from the acute through chronic stages of spinal cord injury (SCI), in an experimental animal model. METHODS In vivo and ex vivo diffusion tensor imaging was performed using a 9.4-T MR imaging system in rats allowed to recover from traumatic contusion SCI from 2 weeks through 25 weeks postinjury, mimicking progression of human SCI from the acute through chronic stages. RESULTS Results showed significant growth of the traumatic lesion up to 15 weeks postinjury, where both the size and mean diffusivity (MD) reached a maximum that was maintained through the remainder of recovery. Mean diffusivity was sensitive to overall spinal cord integrity, whereas fractional anisotropy showed specificity to sites of cavity formation. The use of an MD contour map for in vivo data and a 3D surface map for ex vivo data, showing MD as a function of rostral-caudal distance and recovery time, allowed documentation of rostral and caudal spreading of the lesion. CONCLUSIONS Results from this study demonstrate changes in both lesion morphology and diffusivity beyond previously reported time points and provide a unique perspective on the process of cavity formation and degeneration following traumatic SCI. Additionally, results suggest that MD more accurately defines regions of histological damage than do regions of T2 signal hyperintensity. This could have significant clinical implications in the detection and potential treatment of posttraumatic syringes in SCI.

Diffusion tensor imaging of the spinal cord: insights from animal and human studies.

Diffusion tensor imaging (DTI) provides a measure of the directional diffusion of water molecules in tissues. The measurement of DTI indexes within the spinal cord provides a quantitative assessment of neural damage in various spinal cord pathologies. DTI studies in animal models of spinal cord injury indicate that DTI is a reliable imaging technique with important histological and functional correlates. These studies demonstrate that DTI is a noninvasive marker of microstructural change within the spinal cord. In human studies, spinal cord DTI shows definite changes in subjects with acute and chronic spinal cord injury, as well as cervical spondylotic myelopathy. Interestingly, changes in DTI indexes are visualized in regions of the cord, which appear normal on conventional magnetic resonance imaging and are remote from the site of cord compression. Spinal cord DTI provides data that can help us understand underlying microstructural changes within the cord and assist in prognostication and planning of therapies. In this article, we review the use of DTI to investigate spinal cord pathology in animals and humans and describe advances in this technique that establish DTI as a promising biomarker for spinal cord disorders.