Redefining cellular phenotypy based on embryonic, adult, and cancer stem cell biology

The role of extracellular vesicles in the progression of neurodegenerative disease and cancer

Extracellular vesicles (EVs) are released from many cell types, including normal and pathological cells, and range from 30 to 1000 nm in size. Once thought to be a mechanism for discarding unwanted cellular material, EVs are now thought to play a role in intercellular communication. Evidence is accruing that EVs are capable of carrying mRNAs, miRNAs, noncoding RNAs, and proteins, including those associated with neurodegenerative diseases and cancer, which may be exchanged between cells. For this reason, neurodegenerative diseases and cancers may share a common mechanism of disease spread via EVs. Understanding the role EVs play in disease initiation and progression will aid in the discovery of new clinically relevant biomarkers and the development of better targeted molecular and biological therapies.

Patterns of neural differentiation in melanomas

Background

Melanomas, highly malignant tumors arise from the melanocytes which originate as multipotent neural crest cells during neural tube genesis. The purpose of this study is to assess the pattern of neural differentiation in relation to angiogenesis in VGP melanomas using the tumor as a three dimensional system.

Methods

Tumor-vascular complexes [TVC] are formed at the tumor-stroma interphase, by tumor cells ensheathing angiogenic vessels to proliferate into a mantle of 5 to 6 layers [L1 to L5] forming a perivascular mantle zone [PMZ]. The pattern of neural differentiation is assessed by immunopositivity for HMB45, GFAP, NFP and synaptophysin has been compared in: [a] the general tumor [b] tumor-vascular complexes and [c] perimantle zone [PC] on serial frozen and paraffin sections. Statistical Analysis: ANOVA: Kruskal-Wallis One Way Analysis of Variance; All Pairwise Multiple Comparison Procedures [Tukey Test].

Results

The cells abutting on the basement membrane acquire GFAP positivity and extend processes. New layers of tumor cells show a transition between L2 to L3 followed by NFP and Syn positivity in L4&L5. The level of GFAP+vity in L1&L2 directly proportionate to the percentage of NFP/Syn+vity in L4&L5, on comparing pigmented PMZ with poorly pigmented PMZ. Tumor cells in the perimantle zone show high NFP [65%] and Syn [35.4%] positivity with very low GFAP [6.9%] correlating with the positivity in the outer layers.

Discussion

From this study it is seen that melanoma cells revert to the embryonic pattern of differentiation, with radial glial like cells [GFAP+ve] which further differentiate into neuronal positive cells [NFP&Syn+ve] during angiogenic tumor-vascular interaction, as seen during neurogenesis, to populate the tumor substance.

Stem cells in the treatment of stroke

Stroke is an often devastating insult resulting in neurological deficit lasting greater than 24 hours. In the United States, stroke is the third leading cause of death. In those who do not succumb, any outcome from total recovery over a period of weeks to months to persistent profound neurological deficits is possible. Present treatment centers on the decision to administer tissue plasminogen activator, subsequent medical stabilization and early intervention with rehabilitation and risk factor management. The advent of stem cell therapy presents an exciting new frontier for research in stroke treatment, with the potential to cause a paradigm shift from symptomatic control and secondary prevention to reconstitution of neural networks and prevention of neuronal cell death after neurologic injury.

Potential conversion of adult clavicle-derived chondrocytes into neural lineage cells in vitro

Neural stem cells (NSC) can be isolated from a variety of adult tissues and become a valuable cell source for the repair of peripheral and central nervous diseases. However, their origin and identity remain controversial because of possible de-differentiation/trans-differentiation or contaminations by hematopoietic stem cells (HSCs) or mesenchymal stem cells (MSCs). We hypothesize that the commonly used NSC culture medium can induce committed cartilage chondrocytes to de-differentiate and/or trans-differentiate into neural cell lineages. Using a biological isolation and purification method with explants culture, we here show that adult rat clavicle cartilage chondrocytes migrate out from tissue blocks, form sphere-like structures, possess the capability of self-renewal, express nestin and p75NTR, markers for neural crest progenitors, and differentiate into neurons, glia, and smooth muscle cells. Comparing with adult cartilage, the spherical-forming neural crest cell-like cells downregulate the chondrocytic marker genes, including collagen II, collagen X, and sox9, as well as neural-lineage repressors/silencers REST and coREST, but upregulate a set of well-defined genes related to neural crest cells and pro-neural potential. Nerve growth factor (NGF) and glial growth factor (GGF) increase glial and neuronal differentiation, respectively. These results suggest that chondrocytes derived from adult clavicle cartilage can become neural crest stem-like cells and acquire neuronal phenotypes in vitro. The possible de-differentiation/trans-differentiation mechanisms underlying the conversion were discussed.

Tumor cells from ultrasonic aspirations of glioblastomas migrate and form spheres with radial outgrowth

Studies of primary cells from malignant brain tumors such as glioblastomas are limited by the small size of surgically resected specimens. However, glioblastomas are also frequently debulked via ultrasonic aspiration. In this study, we examined the functional competence and growth of their aspirated cells. Cells from minced tissue and aspirations were comparable in migration, formation of pseudopodia, development of cellular spheres with radial outgrowth, and neuroectodermal features. Cultures were maintained for more than six weeks without fibroblastic overgrowth. Our observations show that ultrasonically aspirated specimens contain cells useful for studies of tumor migration and growth of tumorspheres.

Increased dentate neurogenesis after grafting of glial restricted progenitors or neural stem cells in the aging hippocampus

Neurogenesis in the dentate gyrus (DG) declines severely by middle age, potentially because of age-related changes in the DG microenvironment. We hypothesize that providing fresh glial restricted progenitors (GRPs) or neural stem cells (NSCs) to the aging hippocampus via grafting enriches the DG microenvironment and thereby stimulates the production of new granule cells from endogenous NSCs. The GRPs isolated from the spinal cords of embryonic day 13.5 transgenic F344 rats expressing human alkaline phosphatase gene and NSCs isolated from embryonic day 9 caudal neural tubes of Sox-2:EGFP transgenic mice were expanded in vitro and grafted into the hippocampi of middle-aged (12 months old) F344 rats. Both types of grafts survived well, and grafted NSCs in addition migrated to all layers of the hippocampus. Phenotypic characterization revealed that both GRPs and NSCs differentiated predominantly into astrocytes and oligodendrocytic progenitors. Neuronal differentiation of graft-derived cells was mostly absent except in the dentate subgranular zone (SGZ), where some of the migrated NSCs but not GRPs differentiated into neurons. Analyses of the numbers of newly born neurons in the DG using 5'-bromodeoxyuridine and/or doublecortin assays, however, demonstrated considerably increased dentate neurogenesis in animals receiving grafts of GRPs or NSCs in comparison with both naïve controls and animals receiving sham-grafting surgery. Thus, both GRPs and NSCs survive well, differentiate predominantly into glia, and stimulate the endogenous NSCs in the SGZ to produce more new dentate granule cells following grafting into the aging hippocampus. Grafting of GRPs or NSCs therefore provides an attractive approach for improving neurogenesis in the aging hippocampus. Disclosure of potential conflicts of interest is found at the end of this article.

Stem Cells, Regenerative Medicine, and Animal Models of Disease

The field of stem cell biology and regenerative medicine is rapidly moving toward translation to clinical practice, and in doing so has become even more dependent on animal donors and hosts for generating cellular reagents and assaying their potential therapeutic efficacy in models of human disease. Advances in cell culture technologies have revealed a remarkable plasticity of stem cells from embryonic and adult tissues, and transplantation models are now needed to test the ability of these cells to protect at-risk cells and replace cells lost to injury or disease. With such a mandate, issues related to acceptable sources and controversial (e.g., chimeric) models have challenged the field to provide justification of their potential efficacy before the passage of new restrictions that may curb anticipated breakthroughs. Progress from the use of both in vitro and in vivo regenerative medicine models already offers hope both for the facilitation of stem cell phenotyping in recursive gene expression profile models and for the use of stem cells as powerful new therapeutic reagents for cancer, stroke, Parkinson's, and other challenging human diseases that result in movement disorders. This article describes research in support of the following three objectives: (1) To discover the best stem or progenitor cell in vitro protocols for isolating, expanding, and priming these cells to facilitate their massive propagation into just the right type of neuronal precursor cell for protection or replacement protocols for brain injury or disease, including those that affect movement such as Parkinson's disease and stroke; (2) To discover biogenic factors--compounds that affect stem/progenitor cells (e.g., from high-throughput screening and other bioassay approaches)--that will encourage reactive cell genesis, survival, selected differentiation, and restoration of connectivity in central nervous system movement and other disorders; and (3) To establish the best animal models of human disease and injury, using both small and large animals, for testing new regenerative medicine therapeutics.

Neoplastic stem cells: A novel therapeutic target in clinical oncology

Cancer is among the leading causes of morbidity and mortality in the Western world. Despite recent advances, most therapeutic approaches fail to eradicate the entire neoplastic clone. The remaining cells often develop metastasis and/or recurrences and therefore may represent attractive targets of therapy. A new exciting concept in this regard suggests that each neoplasm represents a heterogeneous population of cells that pertain to long-term tumor growth both in vivo in the natural host and in experimental animals. This concept postulates the existence of small fractions of 'tumor stem cells' that exhibit a capacity for self-renewal and unlimited growth and therefore are distinct from their progeny. Based on these hypotheses, the targeting of neoplastic stem cells is considered indispensable for eradication of the entire clone and for the development of curative treatment approaches. However, tumor stem cells often may be quiescent cells and may express a different profile of targets compared with 'more mature' tumor cells. Therefore, current efforts have attempted to characterize target expression profiles in cancer stem cells in various malignancies. In the this review, the authors have provided a brief summary of the current knowledge of neoplastic stem cells and the application of respective concepts in translational oncology with the ultimate objective of improving anticancer therapy.