Liejing Lu

Diffusion Tensor Imaging of Symptomatic Nerve Roots in Patients with Cervical Disc Herniation

RATIONALE AND OBJECTIVES Cervical disc degeneration can result in nerve root compression and severe symptoms that significantly impair the patients quality of life. The purpose of this study is to investigate multiple diffusion metrics changes in the diffusion tensor imaging (DTI) of cervical nerve roots and their relationship with the clinical severity of patients with cervical disc herniation. MATERIALS AND METHODS High directional DTI of the cervical nerve roots was performed in 18 symptomatic patients and 10 healthy volunteers with a 3.0-T magnetic resonance system after a routine cervical disc scanning. The fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) were calculated from the DTI data and compared between the affected and unaffected sides in the same patient and between healthy volunteers and symptomatic patients. The correlation between the side-to-side diffusion metric differences and the clinical International Standards for Neurological Classification of Spinal Cord Injury scores was analyzed. RESULTS C5-C8 nerve roots were clearly delineated with DTI. The FA, MD, AD, and RD of compressed nerve roots were 0.31 ± 0.091, 2.06 ± 0.536, 2.69 ± 0.657, and 1.75 ± 0.510 mm(2)/s, respectively. Compared to the unaffected side or healthy volunteers, the nerve roots of the affected side showed decreased FA (P < .022) and increased MD (P < .035), AD (P < .047), and RD (P < .012). The clinical International Standards for Neurological Classification of Spinal Cord Injury scores of the patients were negatively correlated with MD (r = -0.57, P = .002), AD (r = -0.451, P = .021), and RD (r = -0.564, P = .003) but not with FA (r = 0.004, P = .984). CONCLUSIONS DTI can potentially be used to assess microstructural abnormalities in the cervical nerve roots in patients with disc herniation.

A novel polymeric micelle used for in vivo MR imaging tracking of neural stem cells in acute ischemic stroke

Transplantation of neural stem cells (NSCs) is a promising treatment strategy for acute ischemic stroke. In vivo tracking of the therapeutic stem cells in the host brain after transplantation is essential not only to ensure the safety and efficacy of the treatment, but also to better understand their migrational dynamics and regeneration potential. Many polymeric nanoparticles have been developed to label stem cells for in vivo tracking by magnetic resonance imaging (MRI), optical imaging (OI) or other imaging modalities. However, the non-degradability and presence of cellular toxicity of the nanoparticles restrict their clinical applications. In this study, we developed a novel cationic polymeric micelles based on amphipathic polymer of biodegradable hydrophilic poly(aspartic acid-dimethylethanediamine) (PAsp(DMA)) that were conjugated with two molecules of hydrophobic cholic acid (CA) by lysine. Image labels, superparamagnetic iron oxide nanoparticles (SPIONs) and fluorescent nile red were simultaneously loaded into the micelles to label NSCs. The labeling capacity, efficiency and cytotoxicity of the cationic micelles were determined. The in vivo MRI tracking of the therapeutic NSCs in acute ischemic stroke was also explored. Our results showed that this type of cationic polymeric micelles achieved a high efficient and safe labeling of NSCs and resulted in reliable in vivo MRI tracking of therapeutic stem cells in acute ischemic stroke, but without detrimental effect. The cationic, biodegradable polymeric micelles are highly translatable for clinical application and can be used as a versatile nanoplatform for stem cell labeling and subsequently in vivo tracking in regenerative medicine.

Superparamagnetic Iron Oxide Nanoparticles-Complexed Cationic Amylose for In Vivo Magnetic Resonance Imaging Tracking of Transplanted Stem Cells in Stroke

Cell-based therapy with mesenchymal stem cells (MSCs) is a promising strategy for acute ischemic stroke. In vivo tracking of therapeutic stem cells with magnetic resonance imaging (MRI) is imperative for better understanding cellular survival and migrational dynamics over time. In this study, we develop a novel biocompatible nanocomplex (ASP-SPIONs) based on cationic amylose, by introducing spermine and the image label, ultrasmall superparamagnetic iron oxide nanoparticles (SPIONs), to label MSCs. The capacity, efficiency, and cytotoxicity of the nanocomplex in transferring SPIONs into green fluorescence protein-modified MSCs were tested; and the performance of in vivo MRI tracking of the transplanted cells in acute ischemic stroke was determined. The results demonstrated that the new class of SPIONs-complexed nanoparticles based on biodegradable amylose can serve as a highly effective and safe carrier to transfer magnetic label into stem cells. A reliable tracking of transplanted stem cells in stroke was achieved by MRI up to 6 weeks, with the desirable therapeutic benefit of stem cells on stroke retained. With the advantages of a relatively low SPIONs concentration and a short labeling period, the biocompatible complex of cationic amylose with SPIONs is highly translatable for clinical application. It holds great promise in efficient, rapid, and safe labeling of stem cells for subsequent cellular MRI tracking in regenerative medicine.

Enhanced Repair Effect of Toll-Like Receptor 4 Activation on Neurotmesis: Assessment Using MR Neurography

BACKGROUND AND PURPOSE: Alternative use of molecular approaches is promising for improving nerve regeneration in surgical repair of neurotmesis. The purpose of this study was to determine the role of MR imaging in assessment of the enhanced nerve regeneration with toll-like receptor 4 signaling activation in surgical repair of neurotmesis. MATERIALS AND METHODS: Forty-eight healthy rats in which the sciatic nerve was surgically transected followed by immediate surgical coaptation received intraperitoneal injection of toll-like receptor 4 agonist lipopolysaccharide (n = 24, study group) or phosphate buffered saline (n = 24, control group) until postoperative day 7. Sequential T2 measurements and gadofluorine M-enhanced MR imaging and sciatic functional index were obtained over an 8-week follow-up period, with histologic assessments performed at regular intervals. T2 relaxation times and gadofluorine enhancement of the distal nerve stumps were measured and compared between nerves treated with lipopolysaccharide and those treated with phosphate buffered saline. RESULTS: Nerves treated with lipopolysaccharide injection achieved better functional recovery and showed more prominent gadofluorine enhancement and prolonged T2 values during the degenerative phase compared with nerves treated with phosphate buffered saline. T2 values in nerves treated with lipopolysaccharide showed a more rapid return to baseline level than did gadofluorine enhancement. Histology exhibited more macrophage recruitment, faster myelin debris clearance, and more pronounced nerve regeneration in nerves treated with toll-like receptor 4 activation. CONCLUSIONS: The enhanced nerve repair with toll-like receptor 4 activation in surgical repair of neurotmesis can be monitored by using gadofluorine M-enhanced MR imaging and T2 relaxation time measurements. T2 relaxation time seems more sensitive than gadofluorine M-enhanced MR imaging for detecting such improved nerve regeneration.

Magnetic Cationic Amylose Nanoparticles Used to Deliver Survivin-Small Interfering RNA for Gene Therapy of Hepatocellular Carcinoma In Vitro

Amylose is a promising nanocarrier for gene delivery in terms of its good biocompatibility and high transfection efficiency. Small interfering RNA against survivin (survivin-siRNA) can cause tumor apoptosis by silencing a hepatocellular carcinoma (HCC)-specific gene at the messenger RNA level. In this study, we developed a new class of folate-functionalized, superparamagnetic iron oxide (SPIO)-loaded cationic amylose nanoparticles to deliver survivin-siRNA to HCC cells. The cellular uptake of nanocomplexes, cytotoxicity, cell apoptosis, and gene suppression mediated by siRNA-complexed nanoparticles were tested. The results demonstrated that folate-functionalized, SPIO-loaded cationic amylose nanoparticles can mediate a specific and safe cellular uptake of survivin-siRNA with high transfection efficiency, resulting in a robust survivin gene downregulation in HCC cells. The biocompatible complex of cationic amylose could be used as an efficient, rapid, and safe gene delivery vector. Upon SPIO loading, it holds a great promise as a theranostic carrier for gene therapy of HCC.

In Vivo Targeted MR Imaging of Endogenous Neural Stem Cells in Ischemic Stroke

Acute ischemic stroke remains a leading cause of death and disability. Endogenous neurogenesis enhanced via activation of neural stem cells (NSCs) could be a promising method for stroke treatment. In vivo targeted tracking is highly desirable for monitoring the dynamics of endogenous NSCs in stroke. Previously, we have successfully realized in vivo targeted MR imaging of endogenous NSCs in normal adult mice brains by using anti-CD15 antibody-conjugated superparamagnetic iron oxide nanoparticles (anti-CD15-SPIONs) as the molecular probe. Herein, we explore the performance of this molecular probe in targeted in vivo tracking of activated endogenous NSCs in ischemic stroke. Our study showed that intraventricular injection of anti-CD15-SPIONs could label activated endogenous NSCs in situ seven days after ischemic stroke, which were detected as enlarged areas of hypo-intense signals on MR imaging at 7.0 T. The treatment of cytosine arabinosine could inhibit the activation of endogenous NSCs, which was featured by the disappearance of areas of hypo-intense signals on MR imaging. Using anti-CD15-SPIONs as imaging probes, the dynamic process of activation of endogenous NSCs could be readily monitored by in vivo MR imaging. This targeted imaging strategy would be of great benefit to develop a new therapeutic strategy utilizing endogenous NSCs for ischemic stroke.

In Vivo Long-Term Tracking of Neural Stem Cells Transplanted into an Acute Ischemic Stroke model with Reporter Gene-Based Bimodal MR and Optical Imaging

Transplantation of neural stem cells (NSCs) is emerging as a new therapeutic approach for stroke. Real-time imaging of transplanted NSCs is essential for successful cell delivery, safety monitoring, tracking cell fate and function, and understanding the interactions of transplanted cells with the host environment. Magnetic resonance imaging (MRI) of magnetic nanoparticle-labeled cells has been the most widely used means to track stem cells in vivo. Nevertheless, it does not allow for the reliable discrimination between live and dead cells. Reporter gene-based MRI was considered as an alternative strategy to overcome this shortcoming. In this work, a class of lentiviral vector-encoding ferritin heavy chain (FTH) and enhanced green fluorescent protein (EGFP) was constructed to deliver reporter genes into NSCs. After these transgenic NSCs were transplanted into the contralateral hemisphere of rats with acute ischemic stroke, MRI and fluorescence imaging (FLI) were performed in vivo for tracking the fate of transplanted cells over a long period of 6 wk. The results demonstrated that the FTH and EGFP can be effectively and safely delivered to NSCs via the designed lentiviral vector. The distribution and migration of grafted stem cells could be monitored by bimodal MRI and FLI. FTH can be used as a robust MRI reporter for reliable reporting of the short-term viability of cell grafts, whereas its capacity for tracking the long-term viability of stem cells remains dependent on several confounding factors such as cell death and the concomitant reactive inflammation.

Assessment of the synergic effect of immunomodulation on nerve repair using multiparametric magnetic resonance imaging

The immune system plays a pivotal role in nerve injury. The aim of this study was to determine the role of multiparametric magnetic resonance imaging (MRI) in evaluation of the synergic effect of immunomodulation on nerve regeneration in neurotmesis.

Monitoring of macrophage recruitment enhanced by Toll-like receptor 4 activation with MR imaging in nerve injury: MRI of Enhanced Macrophage Recruitment in Nerve Injury

Introduction: Macrophage recruitment is critical for nerve regeneration after an injury. The aim of this study was to investigate whether ultrasmall superparamagnetic iron oxide (USPIO) nanoparticle‐based MRI could be used to monitor the enhanced macrophage recruitment by Toll‐like receptor 4 (TLR4) activation in nerve injury. Methods: Rats received intraperitoneal injections of either lipopolysaccharide (LPS) or phosphate buffered saline (PBS) or no injection (controls) after a sciatic nerve crush injury. After intravenous injection of the USPIOs (LPS and PBS groups) or PBS (control group), MRI was performed and correlated with histological findings. Results: LPS group showed more remarkable hypointense signals on T2*‐weighted imaging and lower T2 values in the crushed nerves than PBS group. The hypointense signal areas were associated with an enhanced recruitment of iron‐loaded macrophages to the injured nerves. Discussion: USPIO‐enhanced MRI can be used to monitor the enhanced macrophage recruitment by means of TLR4 signal pathway activation in nerve injury. Muscle Nerve 58: 123–132, 2018

In vivo tracking of the tropism of mesenchymal stem cells to malignant gliomas using reporter gene‐based MR imaging

Mesenchymal stem cells (MSCs) have emerged as a promising cellular vehicle for gene therapy of malignant gliomas due to their property of tumor tropism. However, MSCs may show bidirectional and divergent effects on tumor growth. Therefore, a robust surveillance system with a capacity for noninvasive monitoring of the homing, distribution and fate of stem cells in vivo is highly desired for developing stem cell‐based gene therapies for tumors. In this study, we used ferritin gene‐based magnetic resonance imaging (MRI) to track the tumor tropism of MSCs in a rat orthotopic xenograft model of malignant glioma. MSCs were transduced with lentiviral vectors expressing ferritin heavy chain (FTH) and enhanced green fluorescent protein (eGFP). Intra‐arterial, intravenous and intertumoral injections of these FTH transgenic MSCs (FTH‐MSCs) were performed in rats bearing intracranial orthotopic C6 gliomas. The FTH‐MSCs were detected as hypointense signals on T2‐ and T2*‐weighted images on a 3.0 T clinical MRI. After intra‐arterial injection, 17% of FTH‐MSCs migrated toward the tumor and gradually diffused throughout the orthotopic glioma. This dynamic process could be tracked in vivo by MRI up to 10 days of follow‐up, as confirmed by histology. Moreover, the tumor tropism of MSCs showed no appreciable impact on the progression of the tumor. These results suggest that FTH reporter gene‐based MRI can be used to reliably track the tropism and fate of MSCs after their systemic transplantation in orthotopic gliomas. This real‐time in vivo tracking system will facilitate the future development of stem cell‐based therapies for malignant gliomas.