Suppression of neurocan and enhancement of axonal density in rats after treatment of traumatic brain injury with scaffolds impregnated with bone marrow stromal cells

Abstract

Bone marrow stromal cells (MSCs) are a heterogeneous subpopulation of bone marrow cells that includes mesenchymal stem and progenitor cells. Extensive research conducted during the last decade has shown great promise for MSCs as an effective therapy for traumatic brain injury (TBI) in experimental models 32-35, 37-41,52 and potentially in clinical settings. Also the underlying mechanisms of action of MSCs have been demonstrated to be neuro-restorative rather than neuro-substitutive. 33 Among their neural remodeling effects, MSCs have been shown to promote axonal sprouting in the brain and spinal cord. 42,60 The present study focuses on the ability of MSCs to inhibit neurocan, one of the growth-inhibitory molecules (growth-IMs) that suppress axonal regeneration after neural injury. 18,25 The molecular mechanisms involved in axonal regeneration after neural injury are still unclear; however, over the last few years growth-IMs that have a repulsive effect Suppression of neurocan and enhancement of axonal density in rats after treatment of traumatic brain injury with scaffolds impregnated with bone marrow stromal cells Object. Neurocan is a major form of growth-inhibitory molecule (growth-IM) that suppresses axonal regeneration after neural injury. Bone marrow stromal cells (MSCs) have been shown to inhibit neurocan expression in vitro and in animal models of cerebral ischemia. Therefore, the present study was designed to investigate the effects of treatment of MSCs impregnated with collagen scaffolds on neurocan expression after traumatic brain injury (TBI).Methods. Adult male Wistar rats were injured with controlled cortical impact and treated with saline, human MSCs (hMSCs) (3 × 10 6 ) alone, or hMSCs (3 × 10 6 ) impregnated into collagen scaffolds (scaffold + hMSCs) transplanted into the lesion cavity 7 days after TBI (20 rats per group). Rats were sacrificed 14 days after TBI, and brain tissues were harvested for immunohistochemical studies, Western blot analyses, laser capture microdissections, and quantitative real-time reverse transcriptase polymerase chain reaction (qRT-PCR) to evaluate neurocan protein and gene expressions after various treatments.Results. Animals treated with scaffold + hMSCs after TBI showed increased axonal and synaptic densities compared with the other groups. Scaffold + hMSC treatment was associated with reduced TBI-induced neurocan protein expression and upregulated growth-associated protein 43 (GAP-43) and synaptophysin expression in the lesion boundary zone. In addition, animals in the scaffold + hMSC group had decreased neurocan transcription in reactive astrocytes after TBI. Reduction of neurocan expression was significantly greater in the scaffold + hMSC group than in the group treated with hMSCs alone.Conclusions. The results of this study show that transplanting hMSCs with scaffolds enhances the effect of hMSCs on axonal plasticity in TBI rats. This enhanced axonal plasticity may partially be attributed to the downregulation of neurocan expression by hMSC treatment after in...

Diffusion-Derived Magnetic Resonance Imaging Measures of Longitudinal Microstructural Remodeling Induced by Marrow Stromal Cell Therapy after Traumatic Brain Injury

“…14,20,26,56,57 In agreement with these findings, our dynamic image data showed that FA in particular brain areas spontaneously increased after TBI, which was accompanied with an improvement of functional recovery as measured by mNSS. In addition, similarly to some sites in the brain that are particularly vulnerable to diffuse axonal injury following TBI, 27,58 there seem to be brain regions that are more prone to structural remodeling.…”

“…As described previously, 14,50 our TBI model induced severe brain injury, which affected both the cortical and underlying subcortical regions. Damage to the corpus callosum, the principal and largest bundle of nerve fibers in the brain, and its reorganization afterwards, led to readily detected MRI signal change (Fig.…”

“…For the animal model with severe TBI in the current study, an apparent structural reorganization following the injury is found in the lesion boundary regions, as revealed by both histological and imaging investigations. 14,20,24 In order to compare the capacity of FA and entropy to identify this structural alteration, we therefore focused specifically on the lesion boundary region.…”

“…7,9,37-48 Cell transplantation after TBI promotes WM reorganization, [13][14][15] which can be detected by FA. 20 The advent of advanced model-free estimate MRI, such as diffusion entropy, 30,31 raises the exciting possibility that brain structural reorganization evoked by the therapeutic intervention could be revealed, which may add to our understanding of the role of structural remodeling as underlying functional recovery.…”

“…[5][6][7] However, recent investigations show that cell transplantation, which amplifies endogenous regenerative and restorative processes, has potential as a therapeutic strategy to attenuate devastating secondary pathological processes and meanwhile, to enhance brain plasticity. [8][9][10] As the key mechanism of damage, axonal injury is directly associated with neurobehavioral outcome, 11,12 whereas axonal remodeling, an adaptive brain response to trauma, which compensates for loss of function and could be promoted by cell engraftment, [13][14][15] has received increasing attention. These structural alterations within the injured brain can be revealed by magnetic resonance imaging (MRI), especially diffusion measurements.…”