Molecular biology and neurosurgery in the third millennium

The Evolving Role of Induced Pluripotent Stem Cells and Cerebral Organoids in Treating and Modeling Neurosurgical Diseases

Over the past decade, the use of induced pluripotent stem cells (IPSCs), as both direct therapeutics and building blocks for 3D in vitro models, has exhibited exciting potential in both helping to elucidate pathogenic mechanisms and treating diseases relevant to neurosurgery. Transplantation of IPSCs is being studied in neurological injuries and diseases, such as spinal cord injury and Parkinson's disease, whose clinical manifestations stem from underlying neuronal and/or axonal degeneration. Both animal models and clinical trials have shown that IPSCs have the ability to regenerate damaged neural tissue. Such evidence makes IPSCs a potentially promising therapeutic modality for patients who suffer from these neurological injuries/diseases. In addition, the cerebral organoid, a 3D assembly of IPSC aggregates that develops heterogeneous brain regions, has become the first in vitro model to closely recapitulate the complexity of the brain extracellular matrix, a 3-dimensional network of molecules that structurally and biochemically support neighboring cells. Cerebral organoids have become an exciting prospect for modeling and testing drug susceptibility of brain tumors, such as glioblastoma and metastatic brain cancer. As patient-derived organoid models are becoming more faithful to the brain, they are becoming an increasingly accurate substitute for patient clinical trials; such patient-less trials would protect the patient from potentially ineffective drugs, and speed up trial results and optimize cost. In this review, we aim to describe the role of IPSCs and cerebral organoids in treating and modeling diseases that are relevant to neurosurgery.

β-transducin repeat-containing E3 ubiquitin protein ligase inhibits migration, invasion and proliferation of glioma cells

β-transducin repeat-containing E3 ubiquitin protein ligase (β-TrCP) serves as the substrate recognition subunit for the Skp1-Cullin1-F-box protein E3 ubiquitin ligase, which recognizes the double phosphorylated DSG (X)_2+nS destruction motif in various substrates that are essential for numerous aspects of tumorigenesis and regulates several important signaling pathways. However, the biological significance of β-TrCP in glioma progression remains largely unknown. A previous study by the authors demonstrated that the levels of β-TrCP protein expression in brain glioma tissues were significantly lower compared with non-tumorous tissues and that higher grades of gliomas exhibited lower levels of β-TrCP expression in comparison with lower glioma grades. In addition, low β-TrCP expression was associated with poor prognosis in patients with glioma. Subsequently, the present study aimed to investigate the effect of β-TrCP on migratory, invasive and proliferative abilities of glioma cells. β-TrCP plasmids were transfected into cultured U251 and U87 glioma cells, and changes in migration, invasion and proliferation were analyzed using wound healing, Transwell and EdU assays. It was identified that the overexpression of β-TrCP inhibited migration, invasion and proliferation in glioma cells. In summary, these results indicate that β-TrCP may serve a protective role against the progression of glioma by suppressing cell migration, invasion and proliferation. The potential mechanism of β-TrCP I glioma cells requires additional investigation.

CMIP Promotes Proliferation and Metastasis in Human Glioma

Glioma is one of the most common primary malignant brain tumors and the outcomes are generally poor. The intrinsic mechanisms involved in glioma development and progression remain unclear. Further studies are urgent and necessary. In this study, we have proven that CMIP (C-Maf-inducing protein) promotes cell proliferation and metastasis in A172 cells through knockdown of CMIP and in U251 cells through overexpression of CMIP by using MTT assay, cell colony formation assay, cell migration assay, and cell invasion assay. Furthermore, we discovered that CMIP upregulates MDM2, which is involved in the promoting role of CMIP in human glioma cells. For clinical study, 99 glioma tissues and 59 normal tissues were analyzed. CMIP expression was higher in glioma tissues than in normal tissues. In glioma tissues, CMIP is found to correlate positively with tumor grade but no significant correlation is found with patients' age, gender, or Karnofsky performance score (KPS). Moreover, CMIP also correlates with low relapse-free survival (RFS) rate and overall survival (OS) rate in glioma patients. Therefore, CMIP is oncogenic and could be a potential target for human glioma diagnosis and therapy.

Expression of β-transducin repeat-containing E3 ubiquitin protein ligase in human glioma and its correlation with prognosis

β-transducin repeat-containing E3 ubiquitin protein ligase (β-TrCP) targets a number of substrates essential for specific aspects of tumorigenesis. In addition, β-TrCP regulates various important signaling pathways. As β-TrCP is involved in regulating the ubiquitination and degradation of multiple oncogenes and tumor suppressors, the function of β-TrCP varies between cancer types. At present, the association between β-TrCP expression and clinicopathological factors in glioma is unknown. Therefore, the current study used western blotting and immunohistochemistry to investigate the expression of β-TrCP protein in glioma tissue specimens. It was identified that β-TrCP protein expression levels were significantly lower in glioma compared with non-tumorous human brain tissues. Furthermore, the higher the grade of glioma, the lower the level of β-TrCP expression. Kaplan-Meier analysis demonstrated that patients with low β-TrCP expression experienced significantly worse overall survival compared with patients with high β-TrCP expression. The results indicate that downregulation of β-TrCP may be associated with poor survival in patients with glioma. Together, the current data indicates that β-TrCP may be applied as a useful indicator of glioma prognosis and may serve as an anticancer therapeutic target for glioma, however further investigation is required.

Bex2 regulates cell proliferation and apoptosis in malignant glioma cells via the c-Jun NH2-terminal kinase pathway

The function of Bex2, a member of the Brain Expressed X-linked gene family, in glioma is controversial and its mechanism is largely unknown. We report here that Bex2 regulates cell proliferation and apoptosis in malignant glioma cells via the c-Jun NH2-terminal kinase (JNK) pathway. The expression level of Bex2 is markedly increased in glioma tissues. We observed that Bex2 over-expression promotes cell proliferation, while down-regulation of Bex2 inhibits cell growth. Furthermore, Bex2 down-regulation promotes cell apoptosis and activates the JNK pathway; these effects were abolished by administration of the JNK specific inhibitor, SP600125. Thus, Bex2 may be an important player during the development of glioma.

Discovering neurosurgery: new frontiers

Over the centuries, discoveries of lands unknown, treasures lost and buried, and formulas to delineate physicochemical processes have led to advancements in our understanding of how the world is structured and governed. In science and medicine, discoveries are frequently made following deliberate periods of observation and experimentation to test hypotheses. However, in some instances, discoveries may arise either following a "eureka moment" that transcends rigorous scientific experimentation or following a serendipitous observation. In many instances, scientific discoveries will lead to new inventions that are aimed at improving the manner in which tasks or operations are performed. In this address, some of the key discoveries in science and medicine that have impacted significantly on the field of neurosurgery are described. Some of these include discoveries in neuroanatomy, anesthesiology, infectious diseases, antisepsis, and radiology. Discoveries in the field of molecular science, from the discovery of DNA to next-generation DNA sequencing, which have helped improve the diagnosis and prognosis of neurosurgical patients with conditions such as brain tumors, are also described. In the end, these discoveries have led us to new frontiers in the subspecialty practice of neurosurgery. Navigating our way through these new frontiers will undoubtedly lead to additional discoveries that are unimaginable at present but bound to improve the future care of neurosurgical patients.

Current concepts in the molecular genetics of pediatric brain tumors: implications for emerging therapies

BACKGROUND

The revolution in molecular biology that has taken place over the past 2 decades has provided researchers with new and powerful tools for detailed study of the molecular mechanisms giving rise to the spectrum of pediatric brain tumors. Application of these tools has greatly advanced our understanding of the molecular pathogenesis of these lesions.

REVIEW

After familiarizing readers with some promising new techniques in the field of oncogenomics, this review will present the current state of knowledge as it pertains to the molecular biology of pediatric brain neoplasms. Along the way, we hope to highlight specific instances where the detailed mechanistic knowledge acquired thus far may be exploited for therapeutic advantage.

Expression of structural proteins and angiogenic factors in normal arterial and unruptured and ruptured aneurysm walls

OBJECTIVE

To identify differences in the expression of certain structural proteins and angiogenic growth factors in vessel tissues that represent different phases of the process of intracranial aneurysm formation and rupture: normal vessel wall, intact (unruptured) aneurysm wall, and ruptured vessel wall.

METHODS

The novel study design involved 10 pairs of specimens (ruptured and unruptured aneurysm wall) obtained perioperatively during clipping operations in 10 patients with multiple aneurysms. All surgeries were performed within 5 days of subarachnoid hemorrhage. As controls, five circle of Willis specimens were obtained from five cadavers. Sections of each of the 25 specimens were separately immunostained for five structural proteins (collagen Types III and IV, alpha-smooth muscle actin, fibronectin, and laminin) and three angiogenic factors (vascular endothelial growth factor, basic fibroblast growth factor, and transforming growth factor-alpha). Levels of expression for each protein and factor were graded, and the average grades for each tissue group were recorded and compared.

RESULTS

Among the structural proteins studied, fibronectin specifically is densely expressed in ruptured aneurysms, which is graded as 2.0. However, its expression is less prominent both in nonaneurysmal vessel wall (Grade 1.0) and unruptured aneurysm vessel wall (Grade 1.1). Contrary to fibronectin, laminin is more intensely and regularly expressed in normal vessel wall (Grade 2.7) than in ruptured (Grade 1.1) and unruptured (Grade 1.0) aneurysmal specimens. Among the angiogenic growth factors studied, transforming growth factor-alpha shows a peculiar grading of staining, different from the other two angiogenic factors examined, so that it is more highly expressed in normal circle of Willis specimens (Grade 2.1) than in unruptured and ruptured aneurysm walls, graded as 0.5 and 0.6, respectively.

CONCLUSION

Normal vessel wall, unruptured aneurysm wall, and ruptured aneurysm wall exhibit different levels and patterns of expression for the structural proteins and regulator growth factors investigated. If one accepts the premise that immunohistochemical study has its inherent methodological problems, these results suggest that the biological mediators of aneurysm formation in a vessel wall differ from those of the biological mediators of aneurysm rupture. There was a novel finding related to fibronectin and laminin: the results indicated that a rise in the fibronectin-to-laminin ratio in an unruptured aneurysm wall may contribute to rupture. A drop in transforming growth factor-alpha expression in a vessel wall may also contribute to aneurysm formation.

The evolution and future of minimalism in neurological surgery

INTRODUCTION

The evolution of the field of neurological surgery has been marked by a progressive minimalism. This has been evident in the development of an entire arsenal of modern neurosurgical enterprises, including microneurosurgery, neuroendoscopy, stereotactic neurosurgery, endovascular techniques, radiosurgical systems, intraoperative and navigational devices, and in the last decade, cellular and molecular adjuvants.

AIMS

In addition to reviewing the major developments and paradigm shifts in the cyclic reinvention of the field as it currently stands, this paper attempts to identify forces and developments that are likely to fuel the irresistible escalation of minimalism into the future. These forces include discoveries in computational science, imaging, molecular science, biomedical engineering, and information processing as they relate to the theme of minimalism.

DISCUSSION

These areas are explained in the light of future possibilities offered by the emerging field of nanotechnology with molecular engineering.

Microdissection genotyping of gliomas: therapeutic and prognostic considerations

Molecular anatomic pathology represents the blend of traditional morphological methods and the multigene approach to determine cancer-related gene alterations for diagnostic and prognostic purposes. Microdissection genotyping was utilized to characterize 197 gliomas with targeted microdissection of 2-7 areas spanning the spectrum of histologic types and grades. The methodology described herein is complementary to the existing realities of pathology practice. The technique utilizes paraffin-embedded fixative-treated tissue of small sample size after the primary morphological examination by the pathologist. Molecular information derived from microdissection genotyping in combination with the traditional histological information, results in an enhanced understanding of glioma formation and biological progression leading to improvements in diagnosis and prediction of prognosis. In all, 100% or 32 of 32 cases with at least partial treatment response was observed in neoplasms possessing the 1p or 1p/19q loss. The 19q loss alone without coexisting 1p showed no improvement in treatment response. Gliomas lacking 1p loss with only allelic loss involving 3p, 5q, 9p, 10q and 17p showed unfavorable outcome of only 35%, or six of 17 cases with treatment response. In addition, the determination of fractional allelic loss (favorable/unfavorable), was a very good independent predictor of biological behavior. These findings emphasize the importance of determining the cumulative pattern of mutational damage on 16 distinct sites or more, especially in the presence of 1p loss which in isolation or in combination with 19q is a favorable prognostic factor for therapeutic response.

Gene microarray analysis of human brain arteriovenous malformations

OBJECTIVE

Human brain arteriovenous malformations (BAVMs) display abnormal expression of various angiogenesis-related genes and their products. We examined gene expression patterns in BAVMs by the gene microarray technique.

METHODS

We analyzed BAVM and control brain samples obtained by temporal lobectomy for medically intractable seizure by Affymetrix Human Gene Set U95Av2 (Affymetrix, Inc., Santa Clara, CA). The gene microarray data were compared with new and previously published data that used conventional molecular biology techniques.

RESULTS

We analyzed six BAVM and five control brain samples. From 12,625 gene probes assayed, 1781 gene probes showed differential expression between BAVMs and controls. BAVM samples had a gene expression pattern that was distinct from those of control brain samples. Increased messenger ribonucleic acid expression of vascular endothelial growth factor A was accompanied by increased expression of its protein product. A majority of the gene data was in agreement with previously published data. The gene microarray data generated a new testable hypothesis regarding integrin, and we found increased expression of integrin alphavbeta3 protein in BAVMs.

CONCLUSION

The gene expression pattern of BAVMs was distinct from those of control brain samples. We verified the gene microarray data by demonstrating that increased gene expression levels for angiogenesis-related molecules were accompanied by increased levels of their protein product expression. The gene microarray technique may be a useful tool to study multiple pathways simultaneously in BAVM specimens.

Viral therapy for glioblastoma

Malignant gliomas remain amongst the most difficult cancer to treat. Viral-based gene therapies have been employed for the last decade in preclinical and clinical modes as a novel treatment modality. In this review, such therapies are summarized. The overwhelming majority of clinical studies point one to conclude that methodologies that will increase tumor infection/transduction will lead to enhanced therapeutic results.

Endovascular restorative neurosurgery: a novel concept for molecular and cellular therapy of the nervous system

The amalgam of molecular biology and neurosurgery offers immense promise for neurorestoration and the management of neurodegenerative deficiencies, developmental disorders, neoplasms, stroke, and trauma. This article summarizes present strategies for and impediments to gene therapy and stem cell therapy of the central nervous system and advances the concept of a potential new approach, namely endovascular restorative neurosurgery. The objectives of gene transfer to the central nervous system are efficient transfection of host cells, selective sustained expression of the transgene, and lack of toxicity or immune excitation. The requisite elements of this process are the identification of candidate diseases, the construction of vehicles for gene transfer, regulated expression, and physical delivery. In the selection of target disorders, the underlying genetic events to be overcome, as well as their spatial and temporal distributions, must be considered. These factors determine the requirements for the physical dispersal of the transgene, the duration of transgene expression, and the quantity of transgene product needed to abrogate the disease phenotype. Vehicles for conveying the transgene to the central nervous system include viral vectors (retroviruses, lentiviruses, adenoviruses, adeno-associated viruses, and herpes simplex virus), liposomes, and genetically engineered cells, including neural stem cells. Delivery of the transgene into the brain presents several challenges, including limited and potentially risky access through the cranium, sensitivity to volumetric changes, restricted diffusion, and the blood-brain barrier. Genetic or cellular therapeutic agents may be injected directly into the brain parenchyma (via stereotaxy or craniotomy), into the cerebrospinal fluid (in the ventricles or cisterns), or into the bloodstream (intravenously or intra-arterially). The advantages of the endovascular route include the potential for widespread distribution, the ability to deliver large volumes, limited perturbation of neural tissue, and the feasibility of repeated administration.

The genesis of neurosurgery and the evolution of the neurosurgical operative environment: part II--concepts for future development, 2003 and beyond

The future development of the neurosurgical operative environment is driven principally by concurrent development in science and technology. In the new millennium, these developments are taking on a Jules Verne quality, with the ability to construct and manipulate the human organism and its surroundings at the level of atoms and molecules seemingly at hand. Thus, an examination of currents in technology advancement from the neurosurgical perspective can provide insight into the evolution of the neurosurgical operative environment. In the future, the optimal design solution for the operative environment requirements of specialized neurosurgery may take the form of composites of venues that are currently mutually distinct. Advances in microfabrication technology and laser optical manipulators are expanding the scope and role of robotics, with novel opportunities for bionic integration. Assimilation of biosensor technology into the operative environment promises to provide neurosurgeons of the future with a vastly expanded set of physiological data, which will require concurrent simplification and optimization of analysis and presentation schemes to facilitate practical usefulness. Nanotechnology derivatives are shattering the maximum limits of resolution and magnification allowed by conventional microscopes. Furthermore, quantum computing and molecular electronics promise to greatly enhance computational power, allowing the emerging reality of simulation and virtual neurosurgery for rehearsal and training purposes. Progressive minimalism is evident throughout, leading ultimately to a paradigm shift as the nanoscale is approached. At the interface between the old and new technological paradigms, issues related to integration may dictate the ultimate emergence of the products of the new paradigm. Once initiated, however, history suggests that the process of change will proceed rapidly and dramatically, with the ultimate neurosurgical operative environment of the future being far more complex in functional capacity but strikingly simple in apparent form.

The genesis of neurosurgery and the evolution of the neurosurgical operative environment: part I-prehistory to 2003

Despite its singular importance, little attention has been given to the neurosurgical operative environment in the scientific and medical literature. This article focuses attention on the development of neurosurgery and the parallel emergence of its operative setting. The operative environment has, to a large extent, defined the "state of the art and science" of neurosurgery, which is now undergoing rapid reinvention. During the course of its initial invention, major milestones in the development of neurosurgery have included the definition of anatomy, consolidation of a scientific basis, and incorporation of the practicalities of anesthesia and antisepsis and later operative technical adjuvants for further refinement of action and minimalism. The progress, previously long and laborious in emergence, is currently undergoing rapid evolution. Throughout its evolution, the discipline has assimilated the most effective tools of modernity into the operative environment, leading eventually to the entity known as the operating room. In the decades leading to the present, progressive minimalization of manipulation and the emergence of more refined operative definition with increasing precision are evident, with concurrent miniaturization of attendant computerized support systems, sensors, robotic interfaces, and imaging devices. These developments over time have led to the invention of neurosurgery and the establishment of the current state-of-the-art neurosurgical operating room as we understand it, and indeed, to a broader definition of the entity itself. To remain current, each neurosurgeon should periodically reconsider his or her personal operative environment and its functional design with reference to modernity of practice as currently defined.

Morphological redifferentiation in a malignant astrocytic tumor after gamma knife radiosurgery

Object. The purpose of this study was to demonstrate positron emission tomography (PET), histological, and immunohistochemical data supporting the notion of morphological redifferentiation in a malignant astrocytic tumor after gamma knife radiosurgery (GKS).

Methods. The 11C- methionine-PET activity, Ki-67 labeling index (LI), and p53 protein expression were examined using immunohistochemical methods to assess tumor proliferative capacity. Tissue samples were obtained before and after radiosurgery in a patient with a malignant (Grade III) cerebellar astrocytoma.

Positron emission tomography scans obtained 5.5 months following radiosurgery were suggestive of decreased tumor proliferative capacity and radionecrosis. Histological examination of tumor tissue removed 42 months before GKS was characteristic of a diffuse Grade III astrocytoma in every part of the resected tumor. Similar material removed 6 months after GKS was consistent with a Grade II astrocytoma in the great majority of the resected tumor.

Conclusions. Histopathological examination showed positive phenotypic modification (redifferentiation) consistent with a Grade II astrocytoma in the majority of tumor specimens after radiosurgery. After GKS both the Ki-67 LI and p53 reaction decreased considerably as did 11C methionine uptake. Because p53 is one of the essential genes involved in the radiation response, mutations induced by the ionizing effect of gamma rays might promote partial repair of this gene's tumor suppressor function.

2001: Things to come

THIS ARTICLE DISCUSSES elements in the definition of modernity and emerging futurism in neurological surgery. In particular, it describes evolution, discovery, and paradigm shifts in the field and forces responsible for their realization. It analyzes the cyclical reinvention of the discipline experienced during the past generation and attempts to identify apertures to the near and more remote future. Subsequently, it focuses on forces and discovery in computational science, imaging, molecular science, biomedical engineering, and information processing as they relate to the theme of minimalism that is evident in the field. These areas are explained in the light of future possibilities offered by the emerging field of nanotechnology with molecular engineering.

Alterations of the p53 and pRB pathways in human astrocytoma

Human astrocytomas are characterized by a number of molecular changes affecting two critical tumor suppressor pathways: the pRB and the p53 pathways. Genetic alterations functionally eliminate pRB and p53 themselves or upstream and/or downstream molecules such as products of the Ink4a/ARF locus, p16Ink4a and p14ARF. As a result, malignant cells are defective in critical cell cycle and apoptosis regulatory elements contributing to unrelenting tumour growth and invasion. Current research aims to discover effective means of reconstituting p53 and pRB pathway components in an effort to attenuate the aggressive phenotype of astrocytoma.

Treating complex nervous system vascular disorders through a "needle stick": origins, evolution, and future of neuroendovascular therapy

In the past few decades, dramatic improvements have occurred in the field of neuroendovascular surgery. Endovascular therapy today is a well-established treatment modality for a variety of cerebrovascular and nonvascular central nervous system diseases. The foundation of this spectacular evolution was laid by the efforts of pioneering visionaries who often worked alone and under difficult, almost impossible, conditions. Ongoing device development and refinement have revolutionized the field at a dizzying, exhilarating pace. With a better understanding of the molecular basis of diseases and further advancements in gene therapy, neuroendovascular techniques have an enormous potential for application to the entire spectrum of central nervous system diseases as a minimally invasive vehicle for the delivery of biological factors.

A phase III clinical evaluation of herpes simplex virus type 1 thymidine kinase and ganciclovir gene therapy as an adjuvant to surgical resection and radiation in adults with previously untreated glioblastoma multiforme

Previous uncontrolled clinical trials have shown the in vivo retrovirus (RV)-mediated transduction of glioblastoma cells with the herpes simplex virus thymidine kinase (HSV-tk) gene and subsequent systemic treatment with ganciclovir to be feasible and well tolerated. However, because of continued tumor progression in most patients, the antitumor effect could not be determined using historical controls. Here, we describe a phase III, multicenter, randomized, open-label, parallel-group, controlled trial of the technique in the treatment of 248 patients with newly diagnosed, previously untreated glioblastoma multiforme (GBM). Patients received, in equal numbers, either standard therapy (surgical resection and radiotherapy) or standard therapy plus adjuvant gene therapy during surgery. Progression-free median survival in the gene therapy group was 180 days compared with 183 days in control subjects. Median survival was 365 versus 354 days, and 12-month survival rates were 50 versus 55% in the gene therapy and control groups, respectively. These differences were not significant. Therefore, the adjuvant treatment improved neither time to tumor progression nor overall survival time, although the feasibility and good biosafety profile of this gene therapy strategy were further supported. The failure of this specific protocol may be due mainly to the presumably poor rate of delivery of the HSV-tk gene to tumor cells. In addition, the current mode of manual injection of vector-producing cells with a nonmigratory fibroblast phenotype limits the distribution of these cells and the released replication-deficient RV vectors to the immediate vicinity of the needle track. Further evaluation of the RV-mediated gene therapy strategy must incorporate refinements such as improved delivery of vectors and transgenes to the tumor cells, noninvasive in vivo assessment of transduction rates, and improved delivery of the prodrug across the blood-brain and blood-tumor barrier to the transduced tumor cells.