Brain-derived Progenitor Cells Research Articles

Development of Brain-Derived Bioscaffolds for Neural Progenitor Cell Culture.

Biomaterials derived from brain extracellular matrix (ECM) have the potential to promote neural tissue regeneration by providing instructive cues that can direct cell survival, proliferation, and differentiation. This study focused on the development and characterization of microcarriers derived from decellularized brain tissue (DBT) as a platform for neural progenitor cell culture. First, a novel detergent-free decellularization protocol was established that effectively reduced the cellular content of porcine and rat brains, with a >97% decrease in the dsDNA content, while preserving collagens (COLs) and glycosaminoglycans (GAGs). Next, electrospraying methods were applied to generate ECM-derived microcarriers incorporating the porcine DBT that were stable without chemical cross-linking, along with control microcarriers fabricated from commercially sourced bovine tendon COL. The DBT microcarriers were structurally and biomechanically similar to the COL microcarriers, but compositionally distinct, containing a broader range of COL types and higher sulfated GAG content. Finally, we compared the growth, phenotype, and neurotrophic factor gene expression levels of rat brain-derived progenitor cells (BDPCs) cultured on the DBT or COL microcarriers within spinner flask bioreactors over 2 weeks. Both microcarrier types supported BDPC attachment and expansion, with immunofluorescence staining results suggesting that the culture conditions promoted BDPC differentiation toward the oligodendrocyte lineage, which may be favorable for cell therapies targeting remyelination. Overall, our findings support the further investigation of the ECM-derived microcarriers as a platform for neural cell derivation for applications in regenerative medicine.

Promotion of rat brain-derived progenitor cell neurogenesis by liquiritigenin treatment: Underlying mechanisms

The purpose of the present study was to determine if liquiritigenin, which is a newly discovered estrogen receptor β (ERβ) agonist, can induce differentiation of brain-derived progenitor cells from rats and to investigate the mechanisms involved. Treatment of brain-derived progenitor cell cultures with liquiritigenin increased the number of cells that differentiated into neurons; but the treatment did not alter the growth of astrocytes. Furthermore, treatment with liquiritigenin decreased Notch-2 mRNA and protein expression, which could promote the growth of new neurons. Using RNA interference (RNAi), we determined that inhibition of Notch-2 by liquiritigenin was probably ERβ-dependent. These findings highlight the possible role of liquiritigenin in the repair and regeneration of injured brain tissue of patients with neurodegenerative diseases and support further investigation of the Notch-2 signaling pathway using ERβ agonists.

Proteomic Differentiation Between Murine Retinal and Brain-Derived Progenitor Cells

Previous studies have transplanted a variety of neural stem cells (NSCs) to the eye in hopes of developing a therapy to replace retinal neurons lost to disease. Successful integration, survival, and differentiation of the cell types has been variably successful. At the moment, little is known about the fundamental biological differences between stem cell or progenitor cell types. Characterization of these differences will not only increase our general understanding of this broadly characterized group of cells, but also lead to development of criteria for sorting cells, evaluating their differentiation, and predicting their suitability for transplantation. We have used two-dimensional gel electrophoresis protein expression profiles to characterize the molecular differences between two populations of murine progenitor cells-retinal progenitor cells (RPCs) and brain progenitor cells (BPCs) isolated from mice of the same age and same genetic background. Our protein expression profiling identified 22 proteins that are differentially expressed in RPCs when compared to BPCs. Four of the differentially expressed proteins correspond to proteins known to be involved in a cellular response to stress, and analysis of potential transcription factor binding sites in the promoter regions of their genes suggests these proteins could be co-regulated at the transcriptional level. On the basis of this discovery, we tested the hypothesis that the addition of the antioxidant vitamin E would decrease the expression of the stress-response proteins and influence differentiation of RPCs. Further investigation of differences between multiple populations of RPCs and BPCs during their maintenance and differentiation will further identify fundamental differences that define 'retinal-like' characteristics and provide tools to assay the success of efforts to influence many populations of stem cells to adapt a retinal cell fate.

Astrocyte differentiation selectively upregulates CCL2/monocyte chemoattractant protein‐1 in cultured human brain‐derived progenitor cells

Chemokines (chemoattractant cytokines) and their receptors are present in the brain and may play roles in both neurodevelopment and neuropathology. Increased brain levels of monocyte chemoattractant protein-1 (MCP-1), also known as CCL2, are found in patients with human immunodeficiency virus type 1 (HIV-1)-associated dementia and other acute and chronic neurologic diseases. Although the function of CCL2 in the brain is unclear, it is believed that upregulation of this chemokine during neuropathologic or neuroinflammatory conditions leads to recruitment of activated monocytes into the brain, where they differentiate into macrophages producing neurotoxic and inflammatory molecules. We recently showed that human fetal brain-derived progenitor cells are susceptible to HIV-1 and JC virus infection, and that differentiation toward an astrocyte phenotype increased virus production from these cells. In the current study, we found that in the absence of infection, progenitors produced moderate levels of CCL2 (5.6 ng per million cells). Astrocyte differentiation over 3 weeks increased CCL2 protein levels 30-fold in a biphasic manner, whereas neuronal differentiation decreased production 20-fold. Electromobility shift assays (EMSAs) demonstrated increased nuclear NF-kappaB levels within 2 h of initiating astrocyte differentiation, and inhibitors of NF-kappaB activation partially blocked the CCL2 increase in differentiating astrocytes. Transfection of progenitors with mutated CCL2 promoter/CAT reporter constructs showed that the distal promoter region, containing NF-kappaB and NF-I binding sites, is important for differentiation-induced CCL2 upregulation. Together these results suggest that the transcription factor NF-kappaB, and possibly NF-I, contribute to the upregulation of CCL2 chemokine production during the differentiation of human progenitor cells toward an astrocyte phenotype.

Characterization of the NF2 protein merlin and the ERM protein ezrin in human, rat, and mouse central nervous system

The neurofibromatosis 2 (NF2) protein, merlin, is structurally related to the ERM (ezrin-radixin-moesin) protein family of membrane-cytoskeleton linkers and is mutated in nervous system tumors. Apart from tumor suppressor activity, merlin's functions are poorly understood. We compared the localization and expression of merlin and ezrin in developing and adult brain and in brain-derived progenitor cells. Both proteins were widely but differentially expressed in human, rat, and mouse brain. In brain tissue and neuronal progenitor cell cultures merlin was predominantly found in neurons while ezrin was expressed in astrocytes. Merlin expression was seen from E11 in mouse embryos, whereas ezrin was present earlier. Both proteins were expressed in embryonic mouse neurospheres, where ezrin was specifically localized in filopodia of adherent neuronal progenitor cells. Subcellular analysis demonstrated ezrin in fine filopodial structures in astrocytes, while merlin was detected in neuronal synaptic junctions. The widespread expression of merlin in brain and its association with protein kinase A suggest a role for merlin in brain biology.

Human immunodeficiency virus type 1 infection of human brain-derived progenitor cells.

Although cells of monocytic lineage are the primary source of human immunodeficiency virus type 1 (HIV-1) in the brain, other cell types in the central nervous system, including astrocytes, can harbor a latent or persistent HIV-1 infection. In the present study, we examined whether immature, multipotential human brain-derived progenitor cells (nestin positive) are also permissive for infection. When exposed to IIIB and NL4-3 strains of HIV-1, progenitor cells and progenitor-derived astrocytes became infected, with peak p24 levels of 100 to 500 pg/ml at 3 to 6 days postinfection. After 10 days, virus production was undetectable but could be stimulated by the addition of tumor necrosis factor alpha (TNF-alpha). To bypass limitations to receptor entry, we compared the fate of infection in these cell populations by transfection with the infectious HIV-1 clone, pNL4-3. Again, transfected progenitors and astrocytes produced virus for 7 days but diminished to low levels beyond 8 days posttransfection. During the nonproductive phase, TNF-alpha stimulated virus production from progenitors as late as 5 weeks posttransfection. Astrocytes produced 5- to 20-fold more infectious virus (27 ng of p24/10(6) cells) than progenitors at the peak of 3 days posttransfection. Differentiation of infected progenitors toward an astrocyte phenotype increased virus production to levels consistent with infected astrocytes, suggesting a phenotypic difference in viral replication. Using this cell culture system of multipotential human brain-derived progenitor cells, we provide evidence that progenitor cells may be a reservoir for HIV-1 in the brains of AIDS patients.