Sex-related differences and hormonal effects in the Dry Eye Assessment and Management (DREAM) study

BACKGROUND/AIMS

To compare dry eye disease (DED) signs and symptoms between men and women, as well as between premenopausal and postmenopausal women, in the Dry Eye Assessment and Management (DREAM) study.

METHODS

434 women and 101 men self-reported prior medical history and underwent a standardised DED assessment using the Ocular Surface Disease Index, Brief Pain Inventory, Tear Break-Up Time (TBUT)(s), Schirmer's test 2 (mm/5 min), National Eye Institute-graded lissamine conjunctival staining, corneal staining, meibomian gland dysfunction evaluation and tear osmolarity (mOsms/L) at baseline, 6 months and 12 months. Multivariable linear regression models were used to compare these scores.

RESULTS

Women experienced significantly worse DED signs than men with lower Schirmer's test scores (9.27 vs 12.16; p<0.001), higher corneal staining scores (3.59 vs 2.70; p=0.006) and worse composite DED sign scores (0.52 vs 0.40; p<0.001). Postmenopausal women experienced significantly worse DED signs than premenopausal women with higher corneal staining scores (3.74 vs 2.58, p<0.001), higher conjunctival staining scores (2.80 vs 2.22, p<0.001), higher tear osmolarity (304 vs 299, p=0.004), lower TBUT (3.37 vs 3.93, p=0.047), worse meibomian gland dysfunction (3.05 vs 2.62, p=0.04) and worse composite DED sign scores (0.54 vs 0.42, p<0.001). There were no significant differences in DED symptoms between sex and between premenopausal and postmenopausal women (all p≥0.08).

CONCLUSION

In the DREAM study, women experienced more severe DED signs than men. Further, postmenopausal women presented with more severe DED signs than premenopausal women. Elucidating these differences may improve DED diagnosis and provide future direction in understanding sex-related differences in DED.

TRIAL REGISTRATION NUMBER

NCT02128763.

Association of Tear Cytokine Concentrations with Symptoms and Signs of Dry Eye Disease: Baseline Data from the Dry Eye Assessment and Management (DREAM) Study

PURPOSE

To describe tear concentrations of IL-1β, Il-6, IL-8, IL-10, IL-17A, IFNγ and TNFα in tears, collected by microcapillaries, and their correlation with symptoms and signs in subjects with dry eye disease (DED) in the DREAM Study.

METHODS

Cytokine levels of patients with moderate to severe DED were determined using a magnetic bead assay. Scores for Ocular Surface Disease Index, corneal and conjunctival staining, tear break-up time (TBUT), and Schirmer's test were obtained using standardized procedures. Associations of cytokines with each other and signs/symptoms were assessed with Spearman correlation coefficients (r).

RESULTS

Assay results from 131 patient samples from 10 sites with tear volumes ≥ 4 ul were analyzed. Cytokine concentrations did not correlate with each other in a generally acknowledged pro-inflammatory/anti-inflammatory pattern, such as proinflammatory IL-17A and IFNγ were not inversely correlated to anti-inflammatory cytokine IL-10, and cytokines did not correlate with DED symptoms. Lower corneal staining was correlated with higher concentrations of IL-17A (r= -0.24, p = 0.006), IL-10 (r= -0.25, p = 0.005) and IFNγ (r= -0.33, p = 0.0001). Higher concentrations of IFNγ were associated with lower conjunctival staining (r= -0.18, p = 0.03). Higher concentrations of IL-17A were associated with higher TBUT scores (r = 0.19 p = 0.02).

CONCLUSIONS

Cytokines IL-10, IL-17A and IFNγ were highly correlated with each other but weakly correlated with some DED signs. No key cytokines or definitive expression patterns were identified in this study of moderate to severe DED patients. Further studies addressing various biases, including methodological and sampling biases, and standardization of methodology for inter-laboratory consistency are needed to confirm and establish pathological and clinical relevance of tear cytokines in DED.

Effect of Omega-3 on HLA-DR Expression by Conjunctival Cells and Tear Cytokine Concentrations in the Dry Eye Assessment and Management Study

OBJECTIVES

To determine effect of omega-3 supplementation on conjunctival cell HLA-DR expression and tear concentrations of interleukin (IL)-1β, IL-6, IL-8, IL-10, IL-17A, interferon-γ, and tumor necrosis factor-α in dry eye disease patients in the Dry Eye Assessment and Management study.

METHODS

Patients were randomized to receive a daily dose of eicosapentaenoic and docosahexaenoic acids (ω3) or refined olive oil (placebo) for 12 months. At baseline, 6 and 12 months, HLA-DR expression in conjunctival total, epithelial, and white blood cells and cytokine concentration in tears were determined. Differences in change from baseline between treatment groups were assessed using generalized estimating equations (HLA-DR) or Wilcoxon rank-sum test (cytokines).

RESULTS

No differences were observed in HLA-DR expression in total, epithelial, or white blood cells between ω3 and placebo groups at 6 months (n=435) or 12 months (n=436). The median concentration percent change differed between ω3 and placebo groups at 6 months for IL-6 (-36.6 vs. 24.5%, P =0.02, n=75) and for IL-8 (3.7% vs. 72.6%, P =0.02, n=68); at 12 months, they did not differ ( P ≥0.18). No other differences between the treatment groups were detected.

CONCLUSIONS

ω3 supplementation did not consistently affect ocular inflammatory status as measured by the frequency of HLA-DR expressing conjunctival cells or tear cytokines.

Conjunctival HLA-DR Expression and Its Association With Symptoms and Signs in the DREAM Study

Purpose

Evaluation of dry eye disease (DED) relies on subjective symptoms and signs. We examined HLA-DR expression (HLA-DR%) in conjunctival cells, a minimally invasive biomarker with objective metrics, as an alternative method.

Methods

Dry Eye Assessment and Management (DREAM) study participants completed the Ocular Surface Disease Index questionnaire. Clinicians evaluated tear volume, tear breakup time, and corneal and conjunctival staining. Conjunctival impression cytology samples (n = 1049) were assessed for HLA-DR% in total cells (TCs), epithelial cells (ECs), and white blood cells (WBCs). Associations (categorized into <5%, 5%–15%, >15%–25%, and >25%) with symptoms and signs were evaluated.

Results

The HLA-DR% varied markedly across samples. Over 40% had <5 HLA-DR% positive cells in TCs and ECs and under 23% in WBCs. Higher HLA-DR% was associated with higher conjunctival staining for ECs (mean score 2.77 for <5% and 3.28 for >25%, linear trend P = 0.009) and TCs (mean score 2.82 for <5% and 3.29 for >25%, linear trend P = 0.04) and in TCs was associated with higher corneal staining (mean score 3.59 for <5% and 4.46 for >25%, linear trend P = 0.03). HLA-DR% in WBCs did not correlated with signs (all P ≥ 0.58), and in TCs, ECs or WBCs were not associated with symptoms (P> 0.06).

Conclusions

The distribution of HLA-DR% in conjunctival cells reflects the heterogeneity of disease in DREAM participants. High percentages of samples with <5% positive cells indicate that HLA-DR% may not be a sensitive marker for DED in all patients.

Translational Relevance

High HLA-DR% in ECs in association with high conjunctival staining may identify a subgroup of DED patients prone to epithelial disease and possibly need a different approach from current standards of treatment.

The Growing Need for Validated Biomarkers and Endpoints for Dry Eye Clinical Research

Purpose

Biomarkers with minimally invasive and reproducible objective metrics provide the key to future paradigm shifts in understanding of the underlying causes of dry eye disease (DED) and approaches to treatment of DED. We review biomarkers and their validity in providing objective metrics for DED clinical research and patient care.

Methods

The English-language literature in PubMed primarily over the last decade was surveyed for studies related to identification of biomarkers of DED: (1) inflammation, (2) point-of-care, (3) ocular imaging, and (4) genetics. Relevant studies in each group were individually evaluated for (1) methodological and analytical details, (2) data and concordance with other similar studies, and (3) potential to serve as validated biomarkers with objective metrics.

Results

Significant work has been done to identify biomarkers for DED clinical trials and for patient care. Interstudy variation among studies dealing with the same biomarker type was high. This could be attributed to biologic variations and/or differences in processing, and data analysis. Correlation with other signs and symptoms of DED was not always clear or present.

Conclusions

Many of the biomarkers reviewed show the potential to serve as validated and objective metrics for clinical research and patient care in DED. Interstudy variation for a given biomarker emphasizes the need for detailed reporting of study methodology, including information on subject characteristics, quality control, processing, and analysis methods to optimize development of nonsubjective metrics. Biomarker development offers a rich opportunity to significantly move forward clinical research and patient care in DED.

Overview

DED is an unmet medical need - a chronic pain syndrome associated with variable vision that affects quality of life, is common with advancing age, interferes with the comfortable use of contact lenses, and can diminish results of eye surgeries, such as cataract extraction, LASIK, and glaucoma procedures. It is a worldwide medical challenge with a prevalence rate ranging from 8% to 50%. Many clinicians and researchers across the globe are searching for better answers to understand the mechanisms related to the development and chronicity of DED. Though there have been many clinical trials for DED, few new treatments have emerged over the last decade. Biomarkers may provide the needed breakthrough to propel our understanding of DED to the next level and the potential to realize our goal of truly personalized medicine based on scientific evidence. Clinical trials and research on DED have suffered from the lack of validated biomarkers and less than objective and reproducible endpoints. Current work on biomarkers has provided the groundwork to move forward. This review highlights primarily ocular biomarkers that have been investigated for use in DED, discusses the methodologic outcomes in providing objective metrics for clinical research, and suggests recommendations for further work.

Activated EGFR signaling increases proliferation, survival, and migration and blocks neuronal differentiation in post-natal neural stem cells

Recent evidence supports the notion that transformation of undifferentiated neural stem cell (NSC) precursors may contribute to the development of glioblastoma multiforme (GBM). The over-expression and mutation of the epidermal growth factor receptor (EGFR), along with other cellular pathway mutations, plays a significant role in GBM maintenance progression. Though EGFR signaling is important in determining neural cell fate and conferring astrocyte differentiation, there is a limited understanding of its role in NSC and tumor stem cell (TSC) biology. We hypothesized that EGFR expression and mutation in post-natal NSCs may contribute to cellular aggressiveness including enhanced cellular proliferation, survival and migration. Stable subclones of C17.2 murine NSCs were transfected to over-express either the wild-type EGFR (wtEGFR) or its most common mutated variant EGFRvIII. Activated EGFR signaling in these cells induced behaviors characteristic of GBM TSCs, including enhanced proliferation, survival and migration, even in the absence of EGF ligand. wtEGFR activation was also found to block neuronal differentiation and was associated with a dramatic increase in chemotaxis in the presence of EGF. EGFRvIII expression lead to an increase in NSC proliferation and survival, while it simultaneously blocked neuronal differentiation and promoted glial fate. Our findings suggest that activated EGFR signaling enhances the aggressiveness of NSCs. Understanding the regulatory mechanisms of NSCs may lend insight into deregulated mechanisms of GBM TSC invasion, proliferation, survival and resistance to current treatment modalities.

Neonatal chimerization with human glial progenitor cells can both remyelinate and rescue the otherwise lethally hypomyelinated shiverer mouse

Congenitally hypomyelinated shiverer mice fail to generate compact myelin and die by 18-21 weeks of age. Using multifocal anterior and posterior fossa delivery of sorted fetal human glial progenitor cells into neonatal shiverer x rag2(-/-) mice, we achieved whole neuraxis myelination of the engrafted hosts, which in a significant fraction of cases rescued this otherwise lethal phenotype. The transplanted mice exhibited greatly prolonged survival with progressive resolution of their neurological deficits. Substantial myelination in multiple regions was accompanied by the acquisition of normal nodes of Ranvier and transcallosal conduction velocities, ultrastructurally normal and complete myelination of most axons, and a restoration of a substantially normal neurological phenotype. Notably, the resultant mice were cerebral chimeras, with murine gray matter but a predominantly human white matter glial composition. These data demonstrate that the neonatal transplantation of human glial progenitor cells can effectively treat disorders of congenital and perinatal hypomyelination.

Statin treatment of adult human glial progenitors induces PPAR gamma-mediated oligodendrocytic differentiation

The statins have been proposed as possible therapeutic agents for a variety of autoimmune disorders, including multiple sclerosis. In a genomic screen, we found that glial progenitor cells (GPCs) of the adult human white matter expressed significant levels of the principal statin target, HMG-CoA reductase, as well as additional downstream members of the sterol synthesis pathway. We therefore asked if statin treatment might influence the differentiated fate of adult glial progenitor cells. To assess the functional importance of the sterol synthesis pathway to adult human glial progenitors, we used simvastatin or pravastatin to inhibit HMG-CoA reductase, and then assessed the phenotypic differentiation of the progenitors, as well as the molecular concomitants thereof. We found that both statins induced a dose-dependent induction of oligodendrocyte phenotype, and concomitant reduction in progenitor number. Oligodendrocyte commitment was associated with induction of the sterol-regulated nuclear co-receptor PPARgamma, and could be blocked by the specific PPARgamma antagonist GW9662. Thus, statins may promote oligodendrocyte lineage commitment by parenchymal glial progenitor cells; this might reduce the available progenitor pool, and hence degrade the long-term regenerative competence of the adult white matter.

Long-term expansion of adult human brain subventricular zone precursors

OBJECTIVE

Many common neurosurgical procedures, including anterior temporal lobectomy and endoscopic ventricular puncture, allow neurosurgeons to retrieve portions of the germinal subventricular zone (SVZ). Isolation and maintenance of precursor cells from this zone can be used for hypothesis-driven experiments with a goal of improving our understanding of the basic mechanisms of central nervous system injury or disease and the potential of cell-based therapies to treat them. This article details our ability to reliably harvest, isolate, characterize, and maintain normal adult human brain SVZ precursor cells.

METHODS

Normal SVZ specimens were retrieved as part of anterior temporal lobe resections during planned epilepsy surgery. Dissociated SVZ specimens were plated and incubated in epidermal growth factor and basic fibroblast growth factor for more than 1 year to select for and expand normal neural precursor cells.

RESULTS

Self-renewal and immunocytochemical experiments proved the feasibility of long-term expansion of a slowly dividing nestin+, vimentin+, and glial fibrillary acidic protein-positive astrocyte capable of generating new neurons and glia. These mitotically active bipotent human precursors generated a large number of progeny and possessed significant self-renewal capacity, demonstrated by their ability to generate neurospheres. Cryopreservation was reliable with no loss of the precursor phenotype.

CONCLUSION

We have adapted techniques to allow for the isolation and long-term propagation of human adult neural precursors that are capable of generating both neurons and astrocytes in vitro. We have exploited the cell's self-renewal capacity to significantly and consistently expand human neural precursor cells for as long as 20 months. These findings suggest that cells derived from the SVZ during routine surgery may provide a renewable source of human neural precursor cells to study the biological mechanism of central nervous system disease or for application in cell-based human transplantation paradigms.

Retrovirally mediated telomerase immortalization of neural progenitor cells

Traditional methods of generating immortalized lines of both somatic cells and their progenitors have relied on the use of oncogenes. However, the resulting lines are typically anaplastic in vitro and tumorigenic in vivo, and hence of limited utility. The overexpression of telomerase, as mediated by the induced overexpression of human telomerase reverse transcriptase (hTERT), has permitted the generation of stable, non-oncogenic lines of a variety of cell types. This strategy for immortalization has found special utility in the central nervous system, as few stable lines are available for the study of either human neural progenitor cells, or of neurons or glia of restricted phenotype. We describe the use of retroviral hTERT overexpression for generating lines of immortalized human neural progenitor cells, whose neuronal progeny are phenotypically restricted, post-mitotic and functionally competent. Although we focus here on telomerase immortalization of spinal neural progenitors, this is a broadly applicable protocol for using hTERT to immortalize human fetal neural progenitors of any pre-selected phenotype and for characterizing the cell lines thereby generated.

Neurocytoma is a tumor of adult neuronal progenitor cells

Central neurocytoma (CN) is a rare periventricular tumor, whose derivation, lineage potential, and molecular regulation have been mostly unexplored. We noted that CN cells exhibited an antigenic profile typical of neuronal progenitor cells in vivo, yet in vitro generated neurospheres, divided in response to bFGF (basic fibroblast growth factor), activated the neuroepithelial enhancer of the nestin gene, and gave rise to both neuron-like cells and astrocytes. When CN gene expression was compared with that of both normal adult VZ (ventricular zone) and E/nestin:GFP (green fluorescent protein)-sorted native neuronal progenitors, significant overlap was noted. Marker analysis suggested that the gene expression pattern of CN was that of a proneuronal population; glial markers were conspicuously absent, suggesting that the emergence of astroglia from CN occurred only with passage. The expression pattern of CN was distinguished from that of native progenitor cells by a cohort of differentially expressed genes potentially involved in both the oncogenesis and phenotypic restriction of neurocytoma. These included both IGF2 and several components of its signaling pathway, whose sharp overexpression implicated dysregulated autocrine IGF2 signaling in CN oncogenesis. Both receptors and effectors of canonical wnt signaling, as well as GDF8 (growth differentiation factor 8), PDGF-D, and neuregulin, were differentially overexpressed by CN, suggesting that CN is characterized by the concurrent overactivation of these pathways, which may serve to drive neurocytoma expansion while restricting tumor progenitor phenotype. This strategy of comparing the gene expression of tumor cells to that of the purified native progenitors from which they derive may provide a focused approach to identifying transcripts important to stem and progenitor cell oncogenesis.

Functional engraftment of human ES cell-derived dopaminergic neurons enriched by coculture with telomerase-immortalized midbrain astrocytes

To direct human embryonic stem (HES) cells to a dopaminergic neuronal fate, we cocultured HES cells that were exposed to both sonic hedgehog and fibroblast growth factor 8 with telomerase-immortalized human fetal midbrain astrocytes. These astrocytes substantially potentiated dopaminergic neurogenesis by both WA09 and WA01 HES cells, biasing them to the A9 nigrostriatal phenotype. When transplanted into the neostriata of 6-hydroxydopamine-lesioned parkinsonian rats, the dopaminergic implants yielded a significant, substantial and long-lasting restitution of motor function. However, although rich in donor-derived tyrosine hydroxylase-expressing neurons, the grafts exhibited expanding cores of undifferentiated mitotic neuroepithelial cells, which can be tumorigenic. These results show the utility of recreating the cellular environment of the developing human midbrain while driving dopaminergic neurogenesis from HES cells, and they demonstrate the potential of the resultant cells to mediate substantial functional recovery in a model of Parkinson disease. Yet these data also mandate caution in the clinical application of HES cell-derived grafts, given their potential for phenotypic instability and undifferentiated expansion.

Complementary patterns of gene expression by human oligodendrocyte progenitors and their environment predict determinants of progenitor maintenance and differentiation

OBJECTIVE

Glial progenitor cells are abundant in adult human white matter. This study was designed to identify signaling pathways regulating their self-renewal and fate.

METHODS

We compared the transcriptional profiles of freshly sorted adult human white matter progenitor cells (WMPCs), purified by A2B5-based immunomagnetic sorting, with those of the white matter from which they derived.

RESULTS

We identified 132 genes differentially expressed by WMPCs; these included principal components of five receptor-defined signaling pathways, represented by platelet derived growth factor receptor alpha (PDGFRA) and type 3 fibroblast growth factor receptor (FGFR3), receptor tyrosine phosphatase-beta/zeta (RTPZ), notch, and syndecan3. WMPCs also differentially expressed the bone morphogenetic protein 4 (BMP4) inhibitors neuralin and BAMBI (BMP and activin membrane-bound inhibitor), suggesting tonic defense against BMP signaling. Differential overexpression of RTPZ was accompanied by that of its modulators pleiotrophin, NrCAM, tenascin, and the chondroitin sulfate proteoglycans, suggesting the importance of RTPZ signaling to WMPCs. When exposed to the RTPZ inhibitor bpV(phen), or lentiviral-shRNAi against RTPZ, WMPCs differentiated as oligodendrocytes. Conversely, when neuralin and BAMBI were antagonized by BMP4, astrocytic differentiation was induced, which was reversible by noggin.

INTERPRETATION

The RTPZ and BMP pathways regulate the self-maintenance of adult human WMPCs, and can be modulated to induce their oligodendrocytic or astrocytic differentiation. As such, they provide targets by which to productively mobilize resident progenitor cells of the adult human brain.

Telomerase immortalization of neuronally restricted progenitor cells derived from the human fetal spinal cord

Lineage-restricted progenitors of the central nervous system (CNS) are not readily expandable because their mitotic competence is limited. Here we used retroviral overexpression of human telomerase reverse transcriptase (hTERT) to immortalize progenitors from human fetal spinal cord. The hTERT-immortalized cells divided in basic fibroblast growth factor (bFGF) expressed high telomerase activity, and gave rise to phenotypically restricted subpopulations of either glia or neurons. The latter included a prototypic line, hSC11V-TERT, that gave rise only to neurons. These included both chx10(+) interneurons and Islet1(+)/Hb9(+)/ChAT(+) motor neurons; the latter were recognized by green fluorescent protein (GFP) driven by the Hb9 enhancer. The neurons were postmitotic and achieved electrophysiologic competence. Upon xenograft to both fetal rat brain and injured adult spinal cord, they matured as neurons and survived for 6 months, with no evident tumorigenesis. The cells have survived >168 doublings in vitro, with karyotypic normalcy and without replicative senescence. hTERT overexpression thus permits the generation of progenitor lines able to give rise to phenotypically restricted neurons.

Fetal and adult human oligodendrocyte progenitor cell isolates myelinate the congenitally dysmyelinated brain

Both late-gestation and adult human forebrain contain large numbers of oligodendrocyte progenitor cells (OPCs). These cells may be identified by their A2B5(+)PSA-NCAM(-) phenotype (positive for the early oligodendrocyte marker A2B5 and negative for the polysialylated neural cell adhesion molecule). We used dual-color fluorescence-activated cell sorting (FACS) to extract OPCs from 21- to 23-week-old fetal human forebrain, and A2B5 selection to extract these cells from adult white matter. When xenografted to the forebrains of newborn shiverer mice, fetal OPCs dispersed throughout the white matter and developed into oligodendrocytes and astrocytes. By 12 weeks, the host brains showed extensive myelin production, compaction and axonal myelination. Isolates of OPCs derived from adult human white matter also myelinated shiverer mouse brain, but much more rapidly than their fetal counterparts, achieving widespread and dense myelin basic protein (MBP) expression by 4 weeks after grafting. Adult OPCs generated oligodendrocytes more efficiently than fetal OPCs, and ensheathed more host axons per donor cell than fetal cells. Both fetal and adult OPC phenotypes mediated the extensive and robust myelination of congenitally dysmyelinated host brain, although their differences suggested their use for different disease targets.

Progenitor cells derived from the adult human subcortical white matter disperse and differentiate as oligodendrocytes within demyelinated lesions of the rat brain

A distinct population of white matter progenitor cells (WMPCs), competent but not committed to generate oligodendrocytes, remains ubiquitous in the adult human subcortical white matter. These cells are present in both sexes and into senescence and may constitute as much as 4% of the cells of adult human capsular white matter. Transduction of adult human white matter dissociates with plasmids bearing early oligodendrocytic promoters driving fluorescent reporters permits the separation of these cells at high yield and purity, as does separation based on their expression of A2B5 immunoreactivity. Isolates of these cells survive xenograft to lysolecithin-demyelinated brain and migrate rapidly to infiltrate these lesions, without extending into normal white matter. Within several weeks, implanted progenitors mature as oligodendrocytes, and develop myelin-associated antigens. Lentiviral tagging with green fluorescent protein confirmed that A2B5-sorted progenitors develop myelin basic protein expression within regions of demyelination and that they fail to migrate when implanted into normal brain. Adult human white matter progenitor cells can thus disperse widely through regions of experimental demyelination and are able to differentiate as myelinating oligodendrocytes. This being the case, they may constitute appropriate vectors for cell-based remyelination strategies.

Identification and characterization of neuronal precursors and their progeny from human fetal tissue

We have examined primary human neuronal precursors (HNPs) from 18-22-week-old fetuses. We showed that E-NCAM/MAP2/beta-III tubulin-immunoreactive neuronal precursors divide in vitro and could be induced to differentiate into mature neurons in 2 weeks. HNPs did not express nestin and differentiated slowly compared to rodent neuronal restricted precursors (NRPs, 5 days). Immunocytochemical and physiological analyses showed that HNPs could generate a heterogeneous population of neurons that expressed neurofilament-associated protein and various neurotransmitters, neurotransmitter synthesizing enzymes, voltage-gated ion channels, and ligand-gated neurotransmitter receptors and could fire action potentials. Undifferentiated and differentiated HNPs did not coexpress glial markers. Only a subset of cells that expressed GFP under the control of the Talpha1 tubulin promoter was E-NCAM/beta-III tubulin-immunoreactive, indicating nonexclusive overlap between these two HNP cell populations. Overall, HNPs resemble NRPs isolated from rodent tissue and appear to be a neuronal precursor population.

High-yield selection and extraction of two promoter-defined phenotypes of neural stem cells from the fetal human brain

Neural stem and precursor cells reside in the ventricular lining of the fetal forebrain, and may provide a cellular substrate for brain repair. To selectively identify and extract these cells, we infected dissociated fetal human brain cells with adenoviruses bearing the gene for green fluorescence protein (GFP), placed under the control of enhancer/promoters for two genes (nestin and musashi1) that are expressed in uncommitted neuroepithelial cells. The cells were then sorted by fluorescence-activated cell sorting (FACS) on the basis of E/nestin- or P/musashi1-driven GFP expression. Both P/musashi1:hGFP- and E/nestin:EGFP-sorted cells were multipotent: limiting dilution with clonal expansion as neurospheres, in tandem with retroviral lineage analysis and xenograft to E17 and P0-2 rat forebrain, revealed that each phenotype was able to both self-renew and co-generate neurons and glia. Thus, fluorescent genes placed under the control of early neural promoters allow neural stem cells to be specifically targeted, isolated, and substantially enriched from the fetal human brain.

Promoter-based isolation and fluorescence-activated sorting of mitotic neuronal progenitor cells from the adult mammalian ependymal/subependymal zone

Neuronal precursor cells are widespread in the subependyma of the forebrain ventricular lining, and may provide a cellular substrate for brain repair. We have previously identified and isolated them from fetal brain, by sorting forebrain cells transfected with plasmid DNA encoding the gene for green fluorescent protein (hGFP), driven by the early neuronal promoter for Talpha1 tubulin (P/Talpha1). Fetal neuronal precursors were thereby identified and harvested with both a high degree of enrichment, and a virtual abolition of glial contaminants. We have now extended this approach to include the isolation and purification of neuronal progenitors from the adult brain. Dissociates of the lateral ventricular wall, that included the combined ependymal/subependymal zone, were obtained from 3-month-old adult rats. These cells were cultured and transfected with P/Talpha1:hGFP plasmid DNA. Two days later, the cells were redissociated, sorted on the basis of Talpha1-driven GFP expression, and replated. The majority of these cells expressed the early neuronal proteins Hu and TuJ1/betaIII-tubulin upon FACS; within the week thereafter, most matured as morphologically-evident neurons, that coexpressed betaIII-tubulin and MAP-2. Fewer than 5% expressed astrocytic markers, compared to over half of the cells in matched samples that were either not sorted, or sorted after transfection with a plasmid bearing the nonfluorescent lacZ gene under the control of P/Talpha1 tubulin. Thus, the use of a fluorescent transgene under the control of an early neuron-selective promoter permits the enrichment of neuronal progenitor cells from the adult rat brain, in a form that may allow their heterologous implantation.

In vitro neurogenesis by progenitor cells isolated from the adult human hippocampus

Neurogenesis persists in the adult mammalian hippocampus. To identify and isolate neuronal progenitor cells of the adult human hippocampus, we transfected ventricular zone-free dissociates of surgically-excised dentate gyrus with DNA encoding humanized green fluorescent protein (hGFP), placed under the control of either the nestin enhancer (E/nestin) or the Talpha1 tubulin promoter (P/Talpha1), two regulatory regions that direct transcription in neural progenitor cells. The resultant P/Talpha1:hGFP+ and E/nestin:enhanced (E)GFP+ cells expressed betaIII-tubulin or microtubule-associated protein-2; many incorporated bromodeoxyuridine, indicating their genesis in vitro. Using fluorescence-activated cell sorting, the E/nestin:EGFP+ and P/Talpha1:hGFP+ cells were isolated to near purity, and matured antigenically and physiologically as neurons. Thus, the adult human hippocampus contains mitotically competent neuronal progenitors that can be selectively extracted. The isolation of these cells may provide a cellular substrate for re-populating the damaged or degenerated adult hippocampus.

Promoter-targeted selection and isolation of neural progenitor cells from the adult human ventricular zone

Adult humans, like their nonhuman mammalian counterparts, harbor persistent neural progenitor cells in the forebrain ventricular lining. In the absence of adequate surface markers, however, these cells have proven difficult to isolate for study. We have previously identified and selected neural progenitor cells from both the fetal and adult rodent ventricular zone (VZ), by sorting forebrain cells transfected with plasmid DNA encoding the gene for green fluorescent protein driven by the early neuronal promoter for Talpha1 tubulin (P/Talpha1:hGFP). We have now extended this approach by purifying both P/Talpha1:hGFP tubulin-defined neuronal progenitors, as well as potentially less committed E/nestin:hGFP-defined neural progenitor cells, from the adult human VZ. The ventricular wall of the temporal horn of the lateral ventricle was dissected from temporal lobes obtained from four adult patients undergoing therapeutic lobectomy. These samples were dissociated, and the cultured cells transduced with either P/Talpha1:hGFP or E/nestin:EGFP plasmid DNA. A week later, the cells were redissociated, selected via fluorescence-activated cell sorting (FACS) on the basis of neural promoter-driven GFP expression, and replated. The majority of these cells expressed the early neuronal protein betaIII-tubulin upon FACS; within the week thereafter, most matured as morphologically evident neurons that coexpressed betaIII-tubulin and microtubule-associated protein (MAP)-2. Many of these neurons had incorporated bromodeoxyuridine in vitro in the days before FACS, indicating their mitogenesis in vitro. Thus, the use of fluorescent transgenes under the control of early neural promoters permits the enrichment of neuronal progenitor cells from the adult human ventricular zone. The specific acquisition, in both purity and number, of residual neural progenitor cells from the adult human brain may now permit hitherto unfeasible studies of both their biology and practical application.

Identification, isolation, and promoter-defined separation of mitotic oligodendrocyte progenitor cells from the adult human subcortical white matter

Previous studies have suggested the persistence of oligodendrocyte progenitor cells in the adult mammalian subcortical white matter. To identify oligodendrocyte progenitors in the adult human subcortical white matter, we transfected dissociates of capsular white matter with plasmid DNA bearing the gene for green fluorescence protein (hGFP), placed under the control of the human early promoter (P2) for the oligodendrocytic protein cyclic nucleotide phosphodiesterase (P/hCNP2). Within 4 d after transfection with P/hCNP2:hGFP, a discrete population of small, bipolar cells were noted to express GFP. These cells were A2B5-positive (A2B5(+)), incorporated bromodeoxyuridine in vitro, and constituted <0.5% of all cells. Using fluorescence-activated cell sorting (FACS), the P/hCNP2-driven GFP(+) cells were then isolated and enriched to near-purity. In the weeks after FACS, most P/hCNP2:hGFP-sorted cells matured as morphologically and antigenically characteristic oligodendrocytes. Thus, the human subcortical white matter harbors mitotically competent progenitor cells, which give rise primarily to oligodendrocytes in vitro. By using fluorescent transgenes of GFP expressed under the control of an early oligodendrocytic promoter, these oligodendrocyte progenitor cells may be extracted and purified from adult human white matter in sufficient numbers for implantation and cell-based therapy.

Increase in housing temperature can alleviate decrease in white blood cell counts after energy restriction in C57BL/6 female mice

White blood cell (WBC) counts decrease after energy restriction (ER) in both rodents and humans. ER reduces cellular proliferation rates in various organs of rodents. Increases in housing temperatures can cancel this inhibitory effect of ER. We investigated whether a high housing temperature can alleviate decreases in WBC counts after ER, since peripheral WBC counts at basal levels are considered to represent cellular proliferation rates in the bone marrow. C57BL/6 female mice were allocated to three groups: the control (397 kJ/week), the ER (176 kJ/week) and the ER housed-in-incubator group (ERI: 134 kJ/week). The former two groups were housed at 21-23 degrees C and the third group was housed at 30 degrees C. At 4 and 13 months of age, WBC counts were significantly lower in ER or ERI mice than in control mice. WBC counts, however, were significantly higher in ERI mice (194%) than in ER mice at 13 months of age. A high housing temperature was proved to antagonize the effect of ER on WBC counts, as it antagonizes suppressive effects of ER on cellular proliferation rates in various organs.