Showing papers by "Clive N. Svendsen published in 2013"

Targeting RNA Foci in iPSC-Derived Motor Neurons from ALS Patients with a C9ORF72 Repeat Expansion

Abstract: Amyotrophic lateral sclerosis (ALS) is a severe neurodegenerative condition characterized by loss of motor neurons in the brain andspinalcord.Expansionsofahexanucleotide repeat(GGGGCC) in thenoncodingregionoftheC9ORF72geneare the most common cause of the familial form of ALS (C9-ALS), as well as frontotemporal lobar degeneration and other neurological diseases. How the repeat expansion causes disease remains unclear, with both loss of function (haploinsufficiency) and gain of function (either toxic RNA or protein products) proposed. We report a cellular model of C9-ALS with motor neurons differentiated from induced pluripotent stem cells (iPSCs) derived from ALS patients carrying the C9ORF72 repeat expansion. No significant loss of C9ORF72 expression was observed, and knockdown of the transcript was not toxic to cultured human motor neurons. Transcription of the repeat was increased, leading to accumulation of GGGGCC repeat–containing RNA foci selectively in C9-ALS iPSC-derived motor neurons. Repeat-containing RNA foci colocalized with hnRNPA1 andPur-a, suggestingthat they maybe ableto alter RNAmetabolism. C9-ALSmotor neurons showed altered expression of genes involved in membrane excitability including DPP6, and demonstrated a diminished capacity to fire continuous spikes upon depolarization compared to control motor neurons. Antisense oligonucleotides targeting the C9ORF72 transcript suppressed RNA foci formation and reversed gene expression alterations in C9-ALS motorneurons.Thesedatashowthatpatient-derivedmotorneuronscanbeusedtodelineatepathogeniceventsinALS.

Intermittent hypoxia and stem cell implants preserve breathing capacity in a rodent model of amyotrophic lateral sclerosis.

Abstract: Rationale: Amyotrophic lateral sclerosis (ALS) is a devastating motor neuron disease causing paralysis and death from respiratory failure. Strategies to preserve and/or restore respiratory function are critical for successful treatment. Although breathing capacity is maintained until late in disease progression in rodent models of familial ALS (SOD1G93A rats and mice), reduced numbers of phrenic motor neurons and decreased phrenic nerve activity are observed. Decreased phrenic motor output suggests imminent respiratory failure.Objectives: To preserve or restore phrenic nerve activity in SOD1G93A rats at disease end stage.Methods: SOD1G93A rats were injected with human neural progenitor cells (hNPCs) bracketing the phrenic motor nucleus before disease onset, or exposed to acute intermittent hypoxia (AIH) at disease end stage.Measurements and Main Results: The capacity to generate phrenic motor output in anesthetized rats at disease end stage was: (1) transiently restored by a single presentation of AIH; an...

A Simple Alkaline Method for Decellularizing Human Amniotic Membrane for Cell Culture

Abstract: Human amniotic membrane is a standard substratum used to culture limbal epithelial stem cells for transplantation to patients with limbal stem cell deficiency. Various methods were developed to decellularize amniotic membrane, because denuded membrane is poorly immunogenic and better supports repopulation by dissociated limbal epithelial cells. Amniotic membrane denuding usually involves treatment with EDTA and/or proteolytic enzymes; in many cases additional mechanical scraping is required. Although ensuring limbal cell proliferation, these methods are not standardized, require relatively long treatment times and can result in membrane damage. We propose to use 0.5 M NaOH to reliably remove amniotic cells from the membrane. This method was used before to lyse cells for DNA isolation and radioactivity counting. Gently rubbing a cotton swab soaked in NaOH over the epithelial side of amniotic membrane leads to nearly complete and easy removal of adherent cells in less than a minute. The denuded membrane is subsequently washed in a neutral buffer. Cell removal was more thorough and uniform than with EDTA, or EDTA plus mechanical scraping with an electric toothbrush, or n-heptanol plus EDTA treatment. NaOH-denuded amniotic membrane did not show any perforations compared with mechanical or thermolysin denuding, and showed excellent preservation of immunoreactivity for major basement membrane components including laminin α2, γ1-γ3 chains, α1/α2 and α6 type IV collagen chains, fibronectin, nidogen-2, and perlecan. Sodium hydroxide treatment was efficient with fresh or cryopreserved (10% dimethyl sulfoxide or 50% glycerol) amniotic membrane. The latter method is a common way of membrane storage for subsequent grafting in the European Union. NaOH-denuded amniotic membrane supported growth of human limbal epithelial cells, immortalized corneal epithelial cells, and induced pluripotent stem cells. This simple, fast and reliable method can be used to standardize decellularized amniotic membrane preparations for expansion of limbal stem cells in vitro before transplantation to patients.

Back to the future: how human induced pluripotent stem cells will transform regenerative medicine

Abstract: Based on cloning studies in mammals, all adult human cells theoretically contain DNA that is capable of creating a whole new person. Cells are maintained in their differentiated state by selectively activating some genes and silencing. The dogma until recently was that cell differentiation was largely fixed unless exposed to the environment of an activated oocyte. However, it is now possible to activate primitive pluripotent genes within adult human cells that take them back in time to a pluripotent state (termed induced pluripotent stem cells). This technology has grown at an exponential rate over the past few years, culminating in the Nobel Prize in medicine. Discussed here are recent developments in the field as they relate to regenerative medicine, with an emphasis on creating functional cells, editing their genome, autologous transplantation and how this ground-breaking field may eventually impact human aging.

Neural Stem Cells Derived by Small Molecules Preserve Vision

Abstract: Purpose: The advances in stem cell biology hold a great potential to treat retinal degeneration. Importantly, specific cell types can be generated efficiently with small molecules and maintained stably over numerous passages. Here, we investigated whether neural stem cell (NSC) derived from human embryonic stem cells (hESC) by small molecules can preserve vision following grafting into the Royal College Surgeon (RCS) rats; a model for retinal degeneration.

Stimulation of GABA-Induced Ca2+ Influx Enhances Maturation of Human Induced Pluripotent Stem Cell-Derived Neurons

Abstract: Optimal use of patient-derived, induced pluripotent stem cells for modeling neuronal diseases is crucially dependent upon the proper physiological maturation of derived neurons. As a strategy to develop defined differentiation protocols that optimize electrophysiological function, we investigated the role of Ca2+ channel regulation by astrocyte conditioned medium in neuronal maturation, using whole-cell patch clamp and Ca2+ imaging. Standard control medium supported basic differentiation of induced pluripotent stem cell-derived neurons, as assayed by the ability to fire simple, single, induced action potentials. In contrast, treatment with astrocyte conditioned medium elicited complex and spontaneous neuronal activity, often with rhythmic and biphasic characteristics. Such augmented spontaneous activity correlated with astrocyte conditioned medium-evoked hyperpolarization and was dependent upon regulated function of L-, N- and R-type Ca2+ channels. The requirement for astrocyte conditioned medium could be substituted by simply supplementing control differentiation medium with high Ca2+ or γ-amino butyric acid (GABA). Importantly, even in the absence of GABA signalling, opening Ca2+ channels directly using Bay K8644 was able to hyperpolarise neurons and enhance excitability, producing fully functional neurons. These data provide mechanistic insight into how secreted astrocyte factors control differentiation and, importantly, suggest that pharmacological modulation of Ca2+ channel function leads to the development of a defined protocol for improved maturation of induced pluripotent stem cell-derived neurons.