Jianhong Zhu

Stem cells tropism for malignant gliomas

Various studies have demonstrated the tremendous tropism of stem cells for malignant gliomas, making these cells a potential vehicle for delivery of therapeutic genes to disseminated glioma cells. However, little is known about the mechanisms underlying the glioma-induced tropism of stem cells. Soluble factors including chemokines or growth factors released and expressed by glioma cells at least mediate the tropism of stem cells for gliomas. Here we review the possible mechanisms of stem cells tropism for malignant gliomas. 干细胞具有向恶性胶质瘤趋向性迁移的特性, 并可能成为恶性胶质瘤基因治疗的理想载体。 然而, 对干细胞向胶质瘤迁移的机制仍知之甚少。 胶质瘤细胞分泌的可溶性因子包括趋化因子或生长因子可以介导干细胞的胶质瘤趋向性。 本文就干细胞的胶质瘤趋向性机制进行综述。

An acellular cerebellar biological scaffold: Preparation, characterization, biocompatibility and effects on neural stem cells.

Biomaterial and regenerative medical research has diversified and developed rapidly. A biological scaffold consisting of an extracellular matrix (ECM) functions not only as a supportive material but also as a regulator of cellular functions. Although decellularized scaffolds have been widely applied for the repair of non-central nervous system (CNS) tissues, their efficacy in the CNS has not been extensively investigated. In this report, we describe a dynamic decellularization protocol that combined intracardial perfusion and a series of treatments to effectively remove the cellular components from the cerebellum, which is a unique and relatively simple CNS structure. The resulting cerebellar scaffold retained neurosupportive proteins and growth factors and, when tested with neural stem cells (NSCs) in vitro, was found to be cytocompatible and to stimulate the proliferation and migration of these cells. NSCs that were cultured in vitro on the scaffold differentiated into neurons and astrocytes, as indicated by their expression of βIII-tubulin and glial fibrillary acidic protein (GFAP). Through subcutaneous and intracranial implantation experiments, this preliminary study demonstrated the in vivo biocompatibility of the cerebellar scaffold and indicated its potential for future applications. Thus, our study demonstrated that the cerebellar ECM scaffold provided tissue-specific advantages for regenerative medical applications.

Current status of cell-mediated regenerative therapies for human spinal cord injury

During the past decade, significant advances have been made in refinements for regenerative therapies following human spinal cord injury (SCI). Positive results have been achieved with different types of cells in various clinical studies of SCI. In this review, we summarize recently-completed clinical trials using cell-mediated regenerative therapies for human SCI, together with ongoing trials using neural stem cells. Specifically, clinical studies published in Chinese journals are included. These studies show that current transplantation therapies are relatively safe, and have provided varying degrees of neurological recovery. However, many obstacles exist, hindering the introduction of a specific clinical therapy, including complications and their causes, selection of the target population, and optimization of transplantation material. Despite these and other challenges, with the collaboration of research groups and strong support from various organizations, cell-mediated regenerative therapies will open new perspectives for SCI treatment.

Epigenetics and neural stem cell commitment

Neural stem cell is presently the research hotspot in neuroscience. Recent progress indicates that epigenetic modulation is closely related to the self-renewal and differentiation of neural stem cell. Epigenetics refer to the study of mitotical/meiotical heritage changes in gene function that cannot be explained by changes in the DNA sequence. Major epigenetic mechanisms include DNA methylation, histone modification, chromatin remodeling, genomic imprinting, and non-coding RNA. In this review, we focus on the new insights into the epigenetic mechanism for neural stem cells fate. 神经干细胞是当前神经科学领域的研究热点。 最近的研究显示表观调控与神经干细胞的分化关系密切, 而且为神经干细胞的移植治疗提供可能的细胞来源。 表观调控是指在基因的DNA序列未改变的情况下, 基因功能发生可遗传的变化而导致细胞表型发生改变, 主要机制包括 DNA 甲基化、 组蛋白修饰、 基因印迹、 染色体重组以及非编码小 RNA 等。 本综述就表观调控对神经干细胞分化作用的最新进展作一回顾。

Neural stem/progenitor cells on collagen with anchored basic fibroblast growth factor as potential natural nerve conduits for facial nerve regeneration

Introducing neural stem/progenitor cells (NS/PCs) for repairing facial nerve injuries could be an alternative strategy for nerve gap reconstruction. However, the lack of success associated with current methods of applying NS/PCs to neurological disease is due to poor engraftment following transplantation into the host tissue. In this work, we developed rat-tail collagen-based nerve conduits to repair lengthy facial nerve defects, promoting NS/PC proliferation in the natural nerve conduits with anchored bFGF to improve the therapeutic effects of cell transplantation. In vitro studies showed that heparinized collagen prevented leakage of bFGF and NS/PCs expended in the rat-tail collagen gel with the anchored bFGF. The natural nerve conduits were implanted to connect 8-mm facial nerve defects in rats. The repair outcomes including vibrissae movements, electrophysiological tests, immunohistochemistry and remyelination analysis of regenerated nerve were evaluated. At 12weeks after implantation, only natural nerve conduits treated group showed Hoechst labeled NS/PCs. Besides, the natural nerve conduit significantly promoted functional recovery and nerve growth, which was similar to those of the gold standard, an autograft. The animal experiment results suggesting that the natural nerve conduits were valuable for facial nerve reconstruction. STATEMENT OF SIGNIFICANCE Neural stem/progenitor cells (NS/PCs) were beneficial for the treatment of nervous system diseases. However, after transplantation, the beneficial was limited because the number of living NS/PCs decreased rapidly due to insufficient signaling molecules, such as growth factors, in the microenvironments surrounding transplanted cells. In the present study, we constructed collagen-based nerve conduit with anchored bFGF to achieve higher numbers of NS/PCs for repairing facial nerve injury. Compared with other methods involving neutral salt treatment or dialysis, the fabrication method of collagen scaffolds was simple, low-cost and safe, requiring a relatively short time to prepare. At 12weeks after transplantation, the functional and histological results of natural nerve conduits treated group showed significant similarities to the gold standard method of nerve autografting.

Stem Cell Tracking Technologies for Neurological Regenerative Medicine Purposes

The growing field of stem cell therapy is moving toward clinical trials in a variety of applications, particularly for neurological diseases. However, this translation of cell therapies into humans has prompted a need to create innovative and breakthrough methods for stem cell tracing, to explore the migration routes and its reciprocity with microenvironment targets in the body, to monitor and track the outcome after stem cell transplantation therapy, and to track the distribution and cell viability of transplanted cells noninvasively and longitudinally. Recently, a larger number of cell tracking methods in vivo were developed and applied in animals and humans, including magnetic resonance imaging, nuclear medicine imaging, and optical imaging. This review has been intended to summarize the current use of those imaging tools in tracking stem cells, detailing their main features and drawbacks, including image resolution, tissue penetrating depth, and biosafety aspects. Finally, we address that multimodality imaging method will be a more potential tracking tool in the future clinical application.

Sustained delivery of glial cell-derived neurotrophic factors in collagen conduits for facial nerve regeneration

Facial nerve injury caused by traffic accidents or operations may reduce the quality of life in patients, and recovery following the injury presents unique clinical challenges. Glial cell-derived neurotrophic factor (GDNF) is important in nerve regeneration; however, soluble GDNF rapidly diffuses into body fluids, making it difficult to achieve therapeutic efficacy. In this work, we developed a rat tail derived collagen conduit to connect nerve defects in a simple and safe manner. GDNF was immobilized in the collagen conduits via chemical conjugation to enable controlled release of GDNF. The GDNF delivery system prevented rapid diffusion from the site without impacting bioactivity of GDNF; degradation of the collagen conduit was inhibited owing to the chemical conjugation. The artificial nerve conduit was then used to examine facial nerve regeneration across a facial nerve defect. Following transplantation, the artificial nerve conduits degraded gradually without causing dislocations and serious inflammation, with good integration into the host tissue. Functional and histological tests indicated that the artificial nerve conduits were able to guide the axons to grow through the defect, reaching the distal stumps. The degree of nerve regeneration in the group that was treated with the artificial nerve conduit approached that of the autograft group, and exceeded that of the other conduit grafted groups. STATEMENT OF SIGNIFICANCE In this study, we developed artificial nerve conduits consisting of GDNF immobilized on collagen, with the aim of providing an environment for nerve regeneration. Our results show that the artificial nerve conduits guided the regeneration of axons to the distal nerve segment. GDNF was immobilized stably in the artificial nerve conduits, and therefore retained a sufficient concentration at the target site to effectively promote the regeneration process. The artificial nerve conduits exhibited good biocompatibility and facilitated nerve regeneration and functional recovery with an efficacy that was close to that of an autograft, and better than that of the other conduit grafted groups. Our approach provides an effective delivery system that overcomes the rapid diffusion of GDNF in body fluids, promoting peripheral nerve regeneration. The artificial nerve conduit therefore qualifies as a putative candidate material for the fabrication of peripheral nerve reconstruction devices.

Transplanting Mesenchymal Stem Cells for Treatment of Ischemic Stroke

Stroke is a major disease that leads to high mortality and morbidity. Given the ageing population and the potential risk factors, the prevalence of stroke and socioeconomic burden associated with stroke are expected to increase. During the past decade, both prophylactic and therapeutic strategies for stroke have made significant progress. However, current therapies still cannot adequately improve the outcomes of stroke and may not apply to all patients. One of the significant advances in modern medicine is cell-derived neurovascular regeneration and neuronal repair. Progress in stem cell biology has greatly contributed to ameliorating stroke-related brain injuries in preclinical studies and demonstrated clinical potential in stroke treatment. Mesenchymal stem cells (MSCs) have the differentiating potential of chondrocytes, adipocytes, and osteoblasts, and they have the ability to transdifferentiate into endothelial cells, glial cells, and neurons. Due to their great plasticity, MSCs have drawn much attention from the scientific community. This review will focus on MSCs, stem cells widely utilized in current medical research, and evaluate their effect and potential of improving outcomes in ischemic stroke.

Three-Dimensional Organoid System Transplantation Technologies in Future Treatment of Central Nervous System Diseases

In recent years, scientists have made great achievements in understanding the development of human brain and elucidating critical elements of stepwise spatiotemporal control strategies in neural stem cell specification lineage, which facilitates successful induction of neural organoid in vitro including the cerebral cortex, cerebellar, neural tube, hippocampus cortex, pituitary, and optic cup. Besides, emerging researches on neural organogenesis promote the application of 3D organoid system transplantation in treating central nervous system (CNS) diseases. Present review will categorize current researches on organogenesis into three approaches: (a) stepwise, direct organization of region-specific or population-enriched neural organoid; (b) assemble and direct distinct organ-specific progenitor cells or stem cells to form specific morphogenesis organoid; and (c) assemble embryoid bodies for induction of multilayer organoid. However, the majority of these researches focus on elucidating cellular and molecular mechanisms involving in brain organogenesis or disease development and only a few of them conducted for treating diseases. In this work, we will compare three approaches and also analyze their possible indications for diseases in future treatment on the basis of their distinct characteristics.

MEMOIR: A Novel System for Neural Lineage Tracing

Memory by Engineered Mutagenesis with Optical In situ Readout (MEMOIR) is a novel strategy for lineage tracing that combines Cas9/gRNA and sequential multiplexed single-molecule RNA fluorescence hybridization (seqFISH) [1], which was created by Cai Long et al. at the California Institute of Technology [2]. In MEMOIR, dynamic cellular event histories are recorded, then read out in single cells using seqFISH. Here, we introduce the principles and the implementation processes of the MEMOIR system (Fig. 1), and further discuss its merits for neural lineage tracing compared with classical strategies. In principle, two powerful techniques are essential for MEMOIR: first, a set of genomic elements termed ‘barcoded scratchpad’, whose sequences can be specifically targeted and deleted by Cas9-gRNA, are integrated into the genome of cells. Therefore, for a single cell, its progeny inherit the alterations of the barcoded scratchpads, and all the daughter cells can be traced permanently. Second, seqFISH supports in situ readout of the states of barcoded scratchpads in single cells. By analyzing the distribution patterns of these mutations, the lineage relationships of targeted cells are defined. For instance, whether cells are sisters or cousins have been identified accurately. It has been verified that seqFISH can distinguish the readouts of 13 barcoded scratchpads in a single cell after growth for 3–4 divisions [2]. Clearly, the Cas9/gRNA-targeted ‘barcoded scratchpad’ and seqFISH are the keys for the MEMOIR system to record and readout lineage information. A barcoded scratchpad is a bipartite genetic recording element (i.e. a scratchpad element and a barcode element). Ten repeat units constitute the scratchpad element, which can be targeted by gRNA. Accordingly, the components of Cas9 and gRNA stochastically lead scratchpad to double-strand breaks, namely ‘‘collapse’’. In order to modulate Cas9 activity externally, an inducible degron is contained in a variant Cas9. To distinguish different scratchpads, a unique barcode, as a diacritical sign, is adjoined with each scratchpad. The bipartite element is co-transcribed, and its mRNAs are detected by seqFISH. There are two steps in this novel system: (1) Cas9 [3, 4] stochastically breaks these genetic barcoded-scratchpads and accumulates collapses with each cell division, and the states of barcoded scratchpads reflect the relationships between different daughter cells; and (2) seqFISH is used to interrogate the states of barcoded scratchpads in situ. Based on the readout of seqFISH, a lineage tree is reconstructed within the native context. Another crucial technique is seqFISH, developed by the Cai Long group. They presented a scheme of sequential rounds of hybridization to multiplex mRNAs in a single cell. This differs from FISH in that, after hybridizing and imaging probes, these probes are removed by DNase I and the fluorophores are bleached. Then a new round of hybridization is implemented in the same cell with another series of barcode probes. They have verified that the method maintains 77.9% ± 5.6% of co-localization after 3 & Jianhong Zhu jzhu@fudan.edu.cn