Although astrocytes are involved in the production of an inhibitory glial scar following injury, they are also capable of providing neuroprotection and supporting axonal growth. There is growing appreciation for a diverse and dynamic population of astrocytes, specified by a variety of glial precursors, whose function is regulated regionally and temporally. Consequently, the therapeutic application of glial precursors and astrocytes by effective transplantation protocols requires a better understanding of their phenotypic and functional properties and effective protocols for their preparation. We present a systematic analysis of astrocyte differentiation using multiple preparations of glial-restricted precursors (GRP), evaluating their morphological and phenotypic properties following treatment with fetal bovine serum (FBS), bone morphogenetic protein 4 (BMP-4), or ciliary neurotrophic factor (CNTF) in comparison to controls treated with basic fibroblast growth factor (bFGF), which maintains undifferentiated GRP. We found that treatments with FBS or BMP-4 generated similar profiles of highly differentiated astrocytes that were A2B5−/GFAP+. Treatment with FBS generated the most mature astrocytes, with a distinct and nearhomogeneous morphology of fibroblast-like flat cells, whereas BMP-4 derived astrocytes had a stellate, but heterogeneous morphology. Treatment with CNTF induced differentiation of GRP to an intermediate state of GFAP+ cells that maintained immature markers and had relatively long processes. Furthermore, astrocytes generated by BMP-4 or CNTF showed considerable experimental plasticity, and their morphology and phenotypes could be reversed with complementary treatments along a wide range of mature-immature states. Importantly, when GRP or GRP treated with BMP-4 or CNTF were transplanted acutely into a dorsal column lesion of the spinal cord, cells from all 3 groups survived and generated permissive astrocytes that supported axon growth and regeneration of host sensory axons into, but not out of the lesion. Our study underscores the dynamic nature of astrocytes prepared from GRP and their permissive properties, and suggest that future therapeutic applications in restoring connectivity following CNS injury are likely to require a combination of treatments.

Cellular transplantation using neural stem cells and progenitors is a promising therapeutic strategy that has the potential to replace lost cells, modulate the injury environment, and create a permissive environment for the regeneration of injured host axons. Our research has focused on the use of human glial restricted progenitors (hGRP) and derived astrocytes. In the current study, we examined the morphological and phenotypic properties of hGRP prepared from the fetal central nervous system by clinically-approved protocols, compared with astrocytes derived from hGRP prepared by treatment with ciliary neurotrophic factor or bone morphogenetic protein 4. These differentiation protocols generated astrocytes that showed morphological differences and could be classified along an immature to mature spectrum, respectively. Despite these differences, the cells retained morphological and phenotypic plasticity upon a challenge with an alternate differentiation protocol. Importantly, when hGRP and derived astrocytes were transplanted acutely into a cervical dorsal column lesion, they survived and promoted regeneration of long ascending host sensory axons into the graft/lesion site, with no differences among the groups. Further, hGRP taken directly from frozen stocks behaved similarly and also supported regeneration of host axons into the lesion. Our results underscore the dynamic and permissive properties of human fetal astrocytes to promote axonal regeneration. They also suggest that a time-consuming process of pre-differentiation may not be necessary for therapeutic efficacy, and that the banking of large quantities of readily available hGRP can be an appropriate source of permissive cells for transplantation.

The ability of Candida albicans to transit between different cellular morphologies is believed to be important for virulence. Morphological transitions occur in response to a variety of environmental signals. One such signal is encountered when cells are grown in a semisolid matrix. An important regulator of cellular morphology is the putative transcription factor CZF1. Here we demonstrate that transcription of CZF1 is responsive to growth parameters such as the temperature, carbon source, growth phase of cells, and the physical environment. In wild-type cells, a CZF1 transcript of about 4 kb was expressed when cells were grown embedded in semisolid agar medium, as well as in late exponential phase when cells were grown in liquid medium. Deletion of EFG1, a key regulator of morphogenesis, abolished CZF1 expression. Overexpression of CZF1 revealed that this gene also autoregulates its expression. Efg1p and Czf1p were shown by chromatin immunoprecipitation to act by binding to the promoter of CZF1. The coupling of environmental cues to the expression of a morphogenetic transcription factor may allow C. albicans to coordinate morphogenesis in response to specific conditions encountered in the human host.Candida albicans is an important pathogenic fungus of humans. Although it inhabits its mammalian host primarily as a commensal organism, it is capable of causing a variety of diseases and is the fourth-leading cause of nosocomial infections in the United States (54). C. albicans changes its morphology from the yeast form to filamentous forms in response to various environmental cues, and this ability is thought to be important for the success of the fungus both as a commensal organism and as an opportunistic pathogen (32).Many growth conditions induce filamentous growth, including growth at 37°C, at neutral pH, in nutrient-poor media, or in media containing serum or being embedded within a semisolid matrix (for a review, see reference 15).Deletion of the EFG1 and CPH1 genes, which encode transcriptional regulators, results in a mutant that fails to produce filaments under most laboratory conditions but retains the ability to form filaments when grown embedded within agar (17). In contrast, deletion of the CZF1 gene, encoding a putative transcriptional regulator, results in the converse phenotype, i.e., the strain is defective in filamentation under embedded conditions but not under other filament-inducing conditions (7). These findings indicate that there is a genetic program that functions during filamentous growth under embedded conditions and is distinct from the program that regulates filamentation under other conditions. This genetic program may contribute to disease pathogenesis by promoting filamentation during C. albicans growth within host tissue.CZF1 regulates the morphogenetic response to growth within a semisolid matrix (7). CZF1 is predicted to encode a 388-amino-acid protein with a glutamine-rich central region and a C-terminal cysteine-rich region similar to zinc cluster elements of DNA-binding protei...

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Therapeutic options for Alzheimer's disease are currently limited to symptomatic treatment that only provides modest and temporary maintenance of cognitive and memory functions, without altering disease progression. Although a variety of therapeutics targeting amyloid production or plaque degradation as well as tau hyperphosphorylation and aggregation have been proposed, examined in pre-clinical models and introduced into clinical trials, many have failed to provide significant therapeutic benefit. Concerns over the adequacy of currently used pre-clinical models, in addition to questions pertaining to the timing of therapeutic administration, vis-à-vis synaptic and neuronal loss have been raised, and are further complicated by the genetic diversity of individual patients. This review will provide a brief overview of Alzheimer's disease pathophysiology and the currently approved therapeutics, while the main section will focus on therapeutics currently evaluated in pre-clinical models and clinical trials.