Publications
2026-2022
-
Light-Responsive Bilayer Cell Culture Platform for Reversible Cell Guidance
In vivo, cells are surrounded by a constantly changing microenvironment, which regulates many cell functions such as differentiation, migration, and cell death. Stimuli-responsive biomaterials aim to mimic this interaction between cells and extracellular matrix in vitro. However, reproducing dynamic signaling noninvasively without affecting the cell viability remains a challenge. Herein, a dynamic cell culturing platform consisting of a light-responsive azobenzene molecular glass film and a... -
Pneumatic equiaxial compression device for mechanical manipulation of epithelial cell packing and physiology
It is well established that mechanical cues, e.g., tensile- compressive- or shear forces, are important co-regulators of cell and tissue physiology. To understand the mechanistic effects these cues have on cells, technologies allowing precise mechanical manipulation of the studied cells are required. As the significance of cell density i.e., packing on cellular behavior is beginning to unravel, we sought to design an equiaxial cell compression device based on our previously published cell... -
Heterogeneity of Potassium Channels in Human Embryonic Stem Cell-Derived Retinal Pigment Epithelium
Human pluripotent stem cell (hPSC)-derived retinal pigment epithelium (RPE) is extensively used in RPE research, disease modeling, and transplantation therapies. For successful outcomes, a thorough evaluation of their physiological authenticity is a necessity. Essential determinants of this are the different ion channels of the RPE, yet studies evaluating this machinery in hPSC-RPE are scarce. We examined the functionality and localization of potassium (K+) channels in the human embryonic stem... -
Gap junctions and connexin hemichannels both contribute to the electrical properties of retinal pigment epithelium
Gap junctions are intercellular channels that permit the transfer of ions and small molecules between adjacent cells. These cellular junctions are particularly dense in the retinal pigment epithelium (RPE), and their contribution to many retinal diseases has been recognized. While gap junctions have been implicated in several aspects of RPE physiology, their role in shaping the electrical properties of these cells has not been characterized in mammals. The role of gap junctions in the electrical... -
Cell maturation influences the ability of hESC-RPE to tolerate cellular stress
CONCLUSIONS: Our results suggest that due to better tolerance to cellular stress, the late maturation status of hESC-RPE population is superior compared to monolayers with early maturation status in the transplantation therapy settings.
2021
-
Light-Responsive Bilayer Cell Culture Platform for Reversible Cell Guidance
In vivo, cells are surrounded by a constantly changing microenvironment, which regulates many cell functions such as differentiation, migration, and cell death. Stimuli-responsive biomaterials aim to mimic this interaction between cells and extracellular matrix in vitro. However, reproducing dynamic signaling noninvasively without affecting the cell viability remains a challenge. Herein, a dynamic cell culturing platform consisting of a light-responsive azobenzene molecular glass film and a... -
Culture surface protein coatings affect the barrier properties and calcium signalling of hESC-RPE
Human pluripotent stem cell-derived retinal pigment epithelium (RPE) transplantation is currently under evaluation as treatment for macular degeneration. For therapeutic applications, cryostorage during cell production is typically needed with potential consequences to cell functionality. We have previously shown that the culture substrate affects human embryonic stem cell-derived RPE (hESC-RPE) properties in fresh cultures. Here, we aimed to further identify the role of RPE basement membrane...
2020
-
Azobenzene-based sinusoidal surface topography drives focal adhesion confinement and guides collective migration of epithelial cells
Surface topography is a key parameter in regulating the morphology and behavior of single cells. At multicellular level, coordinated cell displacements drive many biological events such as embryonic morphogenesis. However, the effect of surface topography on collective migration of epithelium has not been studied in detail. Mastering the connection between surface features and collective cellular behaviour is highly important for novel approaches in tissue engineering and repair. Herein, we used...
2019
-
Analysis of ATP-Induced Ca<sup>2+</sup> Responses at Single Cell Level in Retinal Pigment Epithelium Monolayers
Calcium is one of the most important second messengers in cells and thus involved in a variety of physiological processes. In retinal pigment epithelium (RPE), Ca^(2+) and its ATP-dependent signaling pathways play important roles in the retina maintenance functions. Changes in intracellular Ca^(2+) concentration can be measured from living cells by Ca^(2+) imaging. Combining these measurements with quantitative analysis of Ca^(2+) response properties enables studies of signaling pathways... -
Sodium channels enable fast electrical signaling and regulate phagocytosis in the retinal pigment epithelium
CONCLUSIONS: Taken together, our study shows that Na(v) channels are present in RPE, giving this tissue the capacity of fast electrical signaling. The channels are critical for the physiology of RPE with an important role in photoreceptor outer segment phagocytosis. -
Viability of Mouse Retinal Explant Cultures Assessed by Preservation of Functionality and Morphology
CONCLUSIONS: Retinal explants provide a valuable tool for studies of retinal functions and development of ocular therapies. However, critical for long-term use, retinal functionality was lost before structural loss, emphasizing a need for both functional and morphologic readouts to determine the overall state of the cultured retina. -
Structural dynamics of tight junctions modulate the properties of the epithelial barrier
Tight junctions are dynamic structures that are crucial in establishing the diffusion and electrical barrier of epithelial monolayers. Dysfunctions in the tight junctions can impede this barrier function and lead to many pathological conditions. Unfortunately, detailed understanding of the non-specific permeation pathway through the tight junctions, the so-called leak pathway, is lacking. We created computational models of the leak pathway to describe the two main barrier measures, molecular... -
Functional Voltage-Gated Calcium Channels Are Present in Human Embryonic Stem Cell-Derived Retinal Pigment Epithelium
Retinal pigment epithelium (RPE) performs important functions for the maintenance of photoreceptors and vision. Malfunctions within the RPE are implicated in several retinal diseases for which transplantations of stem cell-derived RPE are promising treatment options. Their success, however, is largely dependent on the functionality of the transplanted cells. This requires correct cellular physiology, which is highly influenced by the various ion channels of RPE, including voltage-gated Ca^(2+)...
2018-2017
-
Functional Voltage-Gated Calcium Channels Are Present in Human Embryonic Stem Cell-Derived Retinal Pigment Epithelium
Retinal pigment epithelium (RPE) performs important functions for the maintenance of photoreceptors and vision. Malfunctions within the RPE are implicated in several retinal diseases for which transplantations of stem cell-derived RPE are promising treatment options. Their success, however, is largely dependent on the functionality of the transplanted cells. This requires correct cellular physiology, which is highly influenced by the various ion channels of RPE, including voltage-gated Ca^(2+)...
2016
-
Effect of Rhodopsin Phosphorylation on Dark Adaptation in Mouse Rods
Rhodopsin is a prototypical G-protein-coupled receptor (GPCR) that is activated when its 11-cis-retinal moiety is photoisomerized to all-trans retinal. This step initiates a cascade of reactions by which rods signal changes in light intensity. Like other GPCRs, rhodopsin is deactivated through receptor phosphorylation and arrestin binding. Full recovery of receptor sensitivity is then achieved when rhodopsin is regenerated through a series of steps that return the receptor to its ground state.... -
Rhodopsin kinase and arrestin binding control the decay of photoactivated rhodopsin and dark adaptation of mouse rods
Photoactivation of vertebrate rhodopsin converts it to the physiologically active Meta II (R*) state, which triggers the rod light response. Meta II is rapidly inactivated by the phosphorylation of C-terminal serine and threonine residues by G-protein receptor kinase (Grk1) and subsequent binding of arrestin 1 (Arr1). Meta II exists in equilibrium with the more stable inactive form of rhodopsin, Meta III. Dark adaptation of rods requires the complete thermal decay of Meta II/Meta III into opsin...
2015-2014
-
Early retinal function deficit without prominent morphological changes in the R6/2 mouse model of Huntington's disease
Huntington's disease (HD) is an inherited neurodegenerative disorder that primarily affects the medium-size GABAergic neurons of striatum. The R6/2 mouse line is one of the most widely used animal models of HD. Previously the hallmarks of HD-related pathology have been detected in photoreceptors and interneurons of R6/2 mouse retina. Here we aimed to explore the survival of retinal ganglion cells (RGCs) and functional integrity of distinct retinal cell populations in R6/2 mice. The pattern... -
Chromophore supply rate-limits mammalian photoreceptor dark adaptation
Efficient regeneration of visual pigment following its destruction by light is critical for the function of mammalian photoreceptors. Here, we show that misexpression of a subset of cone genes in the rd7 mouse hybrid rods enables them to access the normally cone-specific retina visual cycle. The rapid supply of chromophore by the retina visual cycle dramatically accelerated the mouse rod dark adaptation. At the same time, the competition between rods and cones for retina-derived chromophore... -
Prediction of passive drug permeability across the blood-retinal barrier
CONCLUSIONS: Our model is the first BRB model of its level and combines the present knowledge of the BRB barrier function. Furthermore, the model forms a platform for the future model development to be used for the design of new drugs and drug administration systems.
2013-2012
-
Generation of hESC-derived retinal pigment epithelium on biopolymer coated polyimide membranes
The in vitro generation of a functional retinal pigment epithelium (RPE) for therapeutic applications requires a limitless source of RPE cells and a supporting scaffold, which improves cell survival and promotes the acquisition of the RPE phenotype. We successfully differentiated human embryonic stem cells (hESCs) toward RPE on a transplantable, biopolymer coated polyimide (PI) membrane. We studied various membrane coatings of which several lead to the generation of a tight and highly polarized...
2011-2009
-
Rod phototransduction determines the trade-off of temporal integration and speed of vision in dark-adapted toads
Human vision is approximately 10 times less sensitive than toad vision on a cool night. Here, we investigate (1) how far differences in the capacity for temporal integration underlie such differences in sensitivity and (2) whether the response kinetics of the rod photoreceptors can explain temporal integration at the behavioral level. The toad was studied as a model that allows experimentation at different body temperatures. Sensitivity, integration time, and temporal accuracy of vision were...
2010-2005
-
A new method for measuring free drug concentration: retinal tissue as a biosensor
CONCLUSIONS: This method enables accurate concentration determinations of the model drug IBMX in retinal tissue in drug-release experiments. The concentration dependence of the photoresponse kinetics has to be calibrated for each retina and temperature. The same preparation can be used for rapid testing of possible bioincompatibility of various molecules.