Dunja Lukovic

Retinitis pigmentosa (RP), a genetically heterogeneous group of diseases together with age-related macular degeneration (AMD), are the leading causes of permanent blindness and are characterized by the progressive dysfunction and death of the light sensing photoreceptors of the retina. Due to the limited regeneration capacity of the mammalian retina, the scientific community has invested significantly in trying to obtain retinal progenitor cells from embryonic stem cells (ESC). These represent an unlimited source of retinal cells, but it has not yet been possible to achieve specific populations, such as photoreceptors, efficiently enough to allow them to be used safely in the future as cell therapy of RP or AMD. In this study, we generated a high yield of photoreceptors from directed differentiation of mouse ESC (mESC) by recapitulating crucial phases of retinal development. We present a new protocol of differentiation, involving hypoxia and taking into account extrinsic and intrinsic cues. These include niche-specific conditions as well as the manipulation of the signaling pathways involved in retinal development. Our results show that hypoxia promotes and improves the differentiation of mESC toward photoreceptors. Different populations of retinal cells are increased in number under the hypoxic conditions applied, such as Crx-positive cells, S-Opsin-positive cells, and double positive cells for Rhodopsin and Recoverin, as shown by immunofluorescence analysis. For the first time, this manuscript reports the high efficiency of differentiation in vivo and the expression of mature rod photoreceptor markers in a large number of differentiated cells, transplanted in the subretinal space of wild-type mice.

Spinal cord injury (SCI) results in neural loss and consequently motor and sensory impairment below the injury. There are currently no effective therapies for the treatment of traumatic SCI in humans. Different kinds of cells including embryonic, fetal, and adult stem cells have been transplanted into animal models of SCI resulting in sensorimotor benefits. Transplantation of human embryonic stem cell (hESC)- or induced pluripotent stem cell (hiPSC)-derived neural cells is nowadays a promising therapy for SCI. This review updates the recent progress in preclinical studies and discusses the advantages and flaws of various neural cell types derived from hESCs and hiPSCs. Before introducing the stem cell replacement strategies in clinical practice, this complex field needs to advance significantly in understanding the lesion itself, the animal model adequacy, and improve cell replacement source. This knowledge will contribute to the successful translation from animals to humans and lead to established guidelines for rigorous safety screening in order to be implemented in clinical practice.

The behavior at air–liquid interfaces of two recombinant versions of human surfactant protein SP-C has been characterized in comparison with that of native palmitoylated SP-C purified from porcine lungs. Both native and recombinant proteins promoted interfacial adsorption of dipalmitoylphosphatidylcholine bilayers to a limited extent, but catalyzed very rapid formation of films from different lipid mixtures containing both zwitterionic and anionic phospholipids. Once at the interface, the recombinant variants exhibited compression-driven structural transitions, consistent with changes in the orientation of the deacylated N-terminal segment, which were not observed in the native protein. Compression isotherms of lipid/protein films suggest that the recombinant SP-C forms promote expulsion at high pressures of a higher number of lipid molecules per mole of protein than does native SP-C. A more dynamic conformation of the N-terminal segment in recombinant SP-C forms is likely also responsible for facilitating compression-driven condensation of domains in anionic phospholipid films as observed by epifluorescence microscopy. Finally, both native palmitoylated SP-C and the phenylalanine-containing recombinant versions facilitate similarly the repetitive compression–expansion dynamics of lipid/protein films, which were able to reach maximal surface pressures with practically no hysteresis along multiple quasi-static or dynamic cycles.

Here we provide a protocol for differentiation of human embryonic stem cells (hESC) into cerebellar neurons using a novel defined culture method. This protocol is based on the application of inductive signaling factors involved in the early patterning of the cerebellar region of the neural tube, followed by the application of factors responsible for cerebellar neuron specification. Human pluripotent stem cells are induced to form spherical embryonic‐like structures called embryoid bodies (EBs) and neuroepithelial tube‐like rosettes using defined chemical conditions. In the presence of FGF, Wnt, and RA signaling factors the rosettes were specified to OTX2‐expressing cells. Further specification of derived cells involves application of BMP factors involved in early development of granule cell progenitors, followed by mitogens and neurotrophins. It typically takes 5 weeks to generate the functional cerebellar granule neurons. This protocol is feeder‐free, applies human recombinant factors, and produces high yield of desired neurons. Curr. Protoc. Stem Cell Biol. 20:1H.5.1‐1H.5.10. © 2012 by John Wiley & Sons, Inc.

Pulmonary surfactant is a lipid-protein complex that coats the interior of the alveoli and enables the lungs to function properly. Upon its synthesis, lung surfactant adsorbs at the interface between the air and the hypophase, a capillary aqueous layer covering the alveoli. By lowering and modulating surface tension during breathing, lung surfactant reduces respiratory work of expansion, and stabilises alveoli against collapse during expiration. Pulmonary surfactant deficiency, or dysfunction, contributes to several respiratory pathologies, such as infant respiratory distress syndrome (IRDS) in premature neonates, and acute respiratory distress syndrome (ARDS) in children and adults. The main clinical exogenous surfactants currently in use to treat some of these pathologies are essentially organic extracts obtained from animal lungs. Although very efficient, natural surfactants bear serious defects: i) they could vary in composition from batch to batch; ii) their production involves relatively high costs, and sources are limited; and iii) they carry a potential risk of transmission of animal infectious agents and the possibility of immunological reaction. All these caveats justify the necessity for a highly controlled synthetic material. In the present review the efforts aimed at new surfactant development, including the modification of existing exogenous surfactants by adding molecules that can enhance their activity, and the progress achieved in the production of completely new preparations, are discussed.

The principles that govern the folding and packing of membrane proteins are still not completely understood. In the present work, we have revisited the glycophorin A (GpA) dimerisation motif that mediates transmembrane (TM) helix association, one of the best‐suited models of membrane protein oligomerisation. By using artificial polyleucine TM segments we have demonstrated in this study that a pattern of only five amino acids (GVxxGVxxT) promotes specific dimerisation. Further, we have used this minimised GpA motif to assess the influence of hydrophobic matching on the TM helix packing process in detergent micelles and found that this factor modulates helix–helix association and/or dissociation between TM fragments.

Background An understanding of the molecular processes that comprise the program of physiological cell death demands analytical techniques for the assessment of death events on the level of the individual cell, especially among transfectants and within heterogeneous populations. The utility of available transfection markers is limited by the variability of marker retention and discrimination as cells die. For example, soluble green fluorescent protein (GFP) leaks from dying cells and is not useful when fixation is required; conversely, transfected β‐galactosidase can be visualized only after fixation and staining. Methods We have tested a GFP variant as a marker for the direct identification and visualization of transfected cells. We have explored the utility of this membrane‐targeted GFP, the genetic fusion of the enhanced GFP and the farnesylation sequence of p21^Ras (EGFP‐F), in a variety of cell death assays. Results EGFP‐F is retained reliably in unfixed dying cells, permitting numerous events of the cell death process to be analyzed in real time in marked cells. Moreover, the cell rounding and shrinkage associated with the loss of adhesion during cell death result in a characteristic condensed EGFP‐F signal. Conclusions EGFP‐F serves to identify transfectants consistently, independent of their ultimate fate. Cellular condensation of EGFP‐F provides a specific and quantitative measure of physiological cell death. Cytometry 43:273‐278, 2001.