The role of laminin in attachment, growth, and differentiation of cultured cells: a brief review

Cytocompatibility of electrospun poly-L-lactic acid membranes for Bruch's membrane regeneration using human embryonic stem cell-derived retinal pigment epithelial cells

Cell replacement therapy is under development for dry age-related macular degeneration (AMD). A thin membrane resembling the Bruch's membrane is required to form a cell-on-membrane construct with retinal pigment epithelial (RPE) cells. These cells have been differentiated from human embryonic stem cells (hESCs) in vitro. A carrier membrane is required for cell implantation, which is biocompatible for cell growth and has dimensions and physical properties resembling the Bruch's membrane. Here a nanofiber electrospun poly-L-lactic acid (PLLA) membrane is tested for capacity to support cell growth and maturation. The requirements for laminin coating of the membrane are identified here. A porous electrospun nanofibrous PLLA membrane of ∼50 nm fiber diameter was developed as a prototype support for functional RPE cells grown as a monolayer. The need for laminin coating applied to the membrane following treatment with poly-L-ornithine (PLO), was identified in terms of cell growth and survival. Test membranes were compared in terms of hydrophilicity after laminin coating, mechanical properties of surface roughness and Young's modulus, porosity and ability to promote the attachment and proliferation of hESC-RPE cells in culture for up to 8 weeks. Over this time, RPE cell proliferation, morphology, and marker and gene expression, were monitored. The functional capacity of cell monolayers was identified in terms of transepithelial electrical resistance (TEER), phagocytosis of cells, as well as expression of the cytokines, vascular endothelial growth factor (VEGF) and pigment epithelium-derived factor (PEDF). PLLA polymer fibers are naturally hydrophobic, so their hydrophilicity was improved by pretreatment with PLO for subsequent coating with the bioactive protein laminin. They were then assessed for amount of laminin adsorbed, contact angle and uniformity of coating using scanning electron microscopy (SEM). Pretreatment with 100% PLO gave the best result over 10% PLO treatment or no treatment prior to laminin adsorption with significantly greater surface stiffness and modulus. By 6 weeks after cell plating, the coated membranes could support a mature RPE monolayer showing a dense apical microvillus structure and pigmented 3D polygonal cell morphology. After 8 weeks, PLO (100%)-Lam coated membranes exhibited the highest cell number, cell proliferation, and RPE barrier function measured as TEER. RPE cells showed the higher levels of specific surface marker and gene expression. Microphthalmia-associated transcription factor expression was highly upregulated indicating maturation of cells. Functionality of cells was indicated by expression of VEGF and PEDF genes as well as phagocytic capacity. In conclusion, electrospun PLLA membranes coated with PLO-Lam have the physical and biological properties to support the distribution and migration of hESC-RPE cells throughout the whole structure. They represent a good membrane candidate for preparation of hESC-RPE cells as a monolayer for implantation into the subretinal space of AMD patients.

The mechanics of the retina: Müller glia role on retinal extracellular matrix and modelling

The retina is a highly heterogeneous tissue, both cell-wise but also regarding its extracellular matrix (ECM). The stiffness of the ECM is pivotal in retinal development and maturation and has also been associated with the onset and/or progression of numerous retinal pathologies, such as glaucoma, proliferative vitreoretinopathy (PVR), age-related macular degeneration (AMD), epiretinal membrane (ERM) formation or uveitis. Nonetheless, much remains unknown about the biomechanical milieu of the retina, and specifically the role that Müller glia play as principal mechanosensors and major producers of ECM constituents. So far, new approaches need to be developed to further the knowledge in the field of retinal mechanobiology for ECM-target applications to arise. In this review, we focus on the involvement of Müller glia in shaping and altering the retinal ECM under both physiological and pathological conditions and look into various biomaterial options to more accurately replicate the impact of matrix stiffness in vitro.

DNA hydroxymethylation differences underlie phenotypic divergence of somatic growth in Nile tilapia reared in common garden

Phenotypic plasticity of metabolism and growth are essential for adaptation to new environmental conditions, such as those experienced during domestication. Epigenetic regulation plays a key role in this process but the underlying mechanisms are poorly understood, especially in the case of hydroxymethylation. Using reduced representation 5-hydroxymethylcytosine profiling, we compared the liver hydroxymethylomes in full-sib Nile tilapia with distinct growth rates (3.8-fold difference) and demonstrated that DNA hydroxymethylation is strongly associated with phenotypic divergence of somatic growth during the early stages of domestication. The 2677 differentially hydroxymethylated cytosines between fast- and slow-growing fish were enriched within gene bodies (79%), indicating a pertinent role in transcriptional regulation. Moreover, they were found in genes involved in biological processes related to skeletal system and muscle structure development, and there was a positive association between somatic growth and 5hmC levels in genes coding for growth factors, kinases and receptors linked to myogenesis. Single nucleotide polymorphism analysis revealed no genetic differentiation between fast- and slow-growing fish. In addition to unveiling a new link between DNA hydroxymethylation and epigenetic regulation of growth in fish during the initial stages of domestication, this study suggests that epimarkers may be applied in selective breeding programmes for superior phenotypes.

Novel adult cortical neuron processing and screening method illustrates sex- and age-dependent effects of pharmaceutical compounds

Neurodegenerative diseases and neurotraumatic injuries are typically age-associated disorders that can reduce neuron survival, neurite outgrowth, and synaptic plasticity leading to loss of cognitive capacity, executive function, and motor control. In pursuit of reducing the loss of said neurological functions, novel compounds are sought that promote neuron viability, neuritogenesis, and/or synaptic plasticity. Current high content in vitro screenings typically use cells that are iPSC-derived, embryonic, or originate from post-natal tissues; however, most patients suffering from neurodegenerative diseases and neurotrauma are of middle-age and older. The chasm in maturity between the neurons used in drug screens and those in a target population is a barrier for translational success of in vitro results. It has been historically challenging to culture adult neurons let alone conduct screenings; therefore, age-appropriate drug screenings have previously not been plausible. We have modified Miltenyi's protocol to increase neuronal yield, neuron purity, and neural viability at a reduced cost to expand our capacity to screen compounds directly in primary adult neurons. To our knowledge, we developed the first morphology-based screening system using adult cortical neurons and the first to incorporate age and sex as biological variables in a screen using adult cortical neurons. By using primary adult cortical neurons from mice that were 4 to 48 weeks old for screening pharmaceutical agents, we have demonstrated age- and sex-dependent effects on neuritogenesis and neuron survival in vitro. Utilizing age- and sex-appropriate in vitro models to find novel compounds increasing neuron survival and neurite outgrowth, made possible by our modified adult neuron processing method, will greatly increase the relevance of in vitro screening for finding neuroprotective compounds.

Spinal Cord Neuronal Network Formation in a 3D Printed Reinforced Matrix-A Model System to Study Disease Mechanisms

3D cell cultures allow a better mimicry of the biological and mechanical environment of cells in vivo compared to 2D cultures. However, 3D cell cultures have been challenging for ultrasoft tissues such as the brain. The present study uses a microfiber reinforcement approach combining mouse primary spinal cord neurons in Matrigel with melt electrowritten (MEW) frames. Within these 3D constructs, neuronal network development is followed for 21 days in vitro. To evaluate neuronal development in 3D constructs, the maturation of inhibitory glycinergic synapses is analyzed using protein expression, the complex mechanical properties by assessing nonlinearity, conditioning, and stress relaxation, and calcium imaging as readouts. Following adaptation to the 3D matrix-frame, mature inhibitory synapse formation is faster than in 2D demonstrated by a steep increase in glycine receptor expression between days 3 and 10. The 3D expression pattern of marker proteins at the inhibitory synapse and the mechanical properties resemble the situation in native spinal cord tissue. Moreover, 3D spinal cord neuronal networks exhibit intensive neuronal activity after 14 days in culture. The spinal cord cell culture model using ultrasoft matrix reinforced by MEW fibers provides a promising tool to study and understand biomechanical mechanisms in health and disease.

Bio-instructive hydrogel expands the paracrine potency of mesenchymal stem cells

The therapeutic efficacy of clinically applied mesenchymal stromal cells (MSCs) is limited due to their injection into harshin vivoenvironments, resulting in the significant loss of their secretory function upon transplantation. A potential strategy for preserving their full therapeutic potential is encapsulation of MSCs in a specialized protective microenvironment, for example hydrogels. However, commonly used injectable hydrogels for cell delivery fail to provide the bio-instructive cues needed to sustain and stimulate cellular therapeutic functions. Here we introduce a customizable collagen I-hyaluronic acid (COL-HA)-based hydrogel platform for the encapsulation of MSCs. Cells encapsulated within COL-HA showed a significant expansion of their secretory profile compared to MSCs cultured in standard (2D) cell culture dishes or encapsulated in other hydrogels. Functionalization of the COL-HA backbone with thiol-modified glycoproteins such as laminin led to further changes in the paracrine profile of MSCs. In depth profiling of more than 250 proteins revealed an expanded secretion profile of proangiogenic, neuroprotective and immunomodulatory paracrine factors in COL-HA-encapsulated MSCs with a predicted augmented pro-angiogenic potential. This was confirmed by increased capillary network formation of endothelial cells stimulated by conditioned media from COL-HA-encapsulated MSCs. Our findings suggest that encapsulation of therapeutic cells in a protective COL-HA hydrogel layer provides the necessary bio-instructive cues to maintain and direct their therapeutic potential. Our customizable hydrogel combines bioactivity and clinically applicable properties such as injectability, on-demand polymerization and tissue-specific elasticity, all features that will support and improve the ability to successfully deliver functional MSCs into patients.

Neuronal Differentiation from Induced Pluripotent Stem Cell-Derived Neurospheres by the Application of Oxidized Alginate-Gelatin-Laminin Hydrogels

Biodegradable hydrogels that promote stem cell differentiation into neurons in three dimensions (3D) are highly desired in biomedical research to study drug neurotoxicity or to yield cell-containing biomaterials for neuronal tissue repair. Here, we demonstrate that oxidized alginate-gelatin-laminin (ADA-GEL-LAM) hydrogels facilitate neuronal differentiation and growth of embedded human induced pluripotent stem cell (hiPSC) derived neurospheres. ADA-GEL and ADA-GEL-LAM hydrogels exhibiting a stiffness close to ~5 kPa at initial cell culture conditions of 37 °C were prepared. Laminin supplemented ADA-GEL promoted an increase in neuronal differentiation in comparison to pristine ADA-GEL, with enhanced neuron migration from the neurospheres to the bulk 3D hydrogel matrix. The presence of laminin in ADA-GEL led to a more than two-fold increase in the number of neurospheres with migrated neurons. Our findings suggest that laminin addition to oxidized alginate-gelatin hydrogel matrices plays a crucial role to tailor oxidized alginate-gelatin hydrogels suitable for 3D neuronal cell culture applications.

Optimization of a Method to Isolate and Culture Adult Porcine, Rats and Mice Müller Glia in Order to Study Retinal Diseases

Müller cells are the predominant glial elements in the retina, extending vertically across this structure, and they fulfill a wealth support roles that are critical for neurons. Alterations to the behavior and phenotype of Müller glia are often seen in animal models of retinal degeneration and in retinal tissue from patients with a variety of retinal disorders. Thus, elucidating the mechanisms underlying the development of retinal diseases would help better understand the cellular processes involved in such pathological changes. Studies into Müller cell activity in vitro have been hindered by the difficulty in obtaining pure cell populations and the tendency of these cells to rapidly differentiate in culture. Most protocols currently used to isolate Müller glia use neonatal or embryonic tissue but here, we report an optimized protocol that facilitates the reliable and straightforward isolation and culture of Müller cells from adult pigs, rats and mice. The protocol described here provides an efficient method for the rapid isolation of adult mammalian Müller cells, which represents a reliable platform to study therapeutic targets and to test the effects of drugs that might combat retinal diseases.

Laminin-Coated Poly(Methyl Methacrylate) (PMMA) Nanofiber Scaffold Facilitates the Enrichment of Skeletal Muscle Myoblast Population

Myoblasts, the contractile cells of skeletal muscle, have been invaluable for fundamental studies of muscle development and clinical applications for muscle loss. A major limitation to the myoblast-based therapeutic approach is contamination with non-contractile fibroblasts, which overgrow during cell expansion. To overcome these limitations, this study was carried out to establish a 3D culture environment using nanofiber scaffolds to enrich the myoblast population during construct formation. Poly(methyl methacrylate) (PMMA) nanofiber (PM) scaffolds were fabricated using electrospinning techniques and coated with extracellular matrix (ECM) proteins, such as collagen or laminin, in the presence or absence of genipin. A mixed population of myoblasts and fibroblasts was isolated from human skeletal muscle tissues and cultured on plain surfaces, as well as coated and non-coated PM scaffolds. PMMA can produce smooth fibers with an average diameter of 360 ± 50 nm. Adsorption of collagen and laminin on PM scaffolds is significantly enhanced in the presence of genipin, which introduces roughness to the nanofiber surface without affecting fiber diameter and mechanical properties. It was also demonstrated that laminin-coated PM scaffolds significantly enhance myoblast proliferation (0.0081 ± 0.0007 h-1) and migration (0.26 ± 0.04 μm/min), while collagen-coated PM scaffolds favors fibroblasts proliferation (0.0097 ± 0.0009 h-1) and migration (0.23 ± 0.03 μm/min). Consequently, the myoblast population was enriched on laminin-coated PM scaffolds throughout the culture process. Therefore, laminin coating of nanofiber scaffolds could be a potential scaffold for the development of a tissue-engineered muscle substitute.

Automating the expansion process of human skeletal muscle myoblasts with suppression of myotube formation

An intelligent culture system accompanied by automated operations (liquid transfer and cell passage) was newly developed to perform serial cultures of human skeletal muscle myoblasts. To realize a desired performance, a laminin-coated surface was applied to myoblast expansion in a culture flask. It was found that the laminin coating enhanced the overall growth ability attributable not to shortening of the doubling time but to prevention of differentiation toward myotube formation, compared with that on a conventional plain surface. In addition, the effects of seeding density and confluence degree on the growth were investigated quantitatively in terms of cell attachment and division as well as proliferative cell population in the culture on the laminin-coated surface. With increasing in seeding density, the number of proliferative cells decreased at the end of culture accompanied by an increase in the confluence degree, which caused poor attachment of the passaged cells on the surface in the subsequent culture. The quantitative analyses of these cell behaviors helped us determine the appropriate seeding density and attainable confluence degree during one passage, which were 1.0 x 10(3) cells/cm(2) and 0.5 as the initial and boundary conditions, respectively. An automated culture system that could manage two serial cultures by monitoring the confluence degree was constructed. The automated operation with the intelligent determination of the time for passage was successfully performed without serious loss of growth activity, compared with manual operation using conventional flasks. These results indicated that the monitoring of confluence degree is effective to perform the culture passage of myoblasts, being contributable to automating the cell expansion process.

Localization of Lutheran, a novel laminin receptor, in normal, knockout, and transgenic mice suggests an interaction with laminin alpha5 in vivo

Laminins are major components of all basement membranes. One laminin that has garnered particular interest, due to its widespread expression pattern and importance during development, is the laminin alpha5 chain. In vitro studies have suggested that the Lutheran blood group glycoprotein/basal cell adhesion molecule (Lu), an Ig superfamily transmembrane protein, is a receptor for laminins containing the alpha5 chain. However, there are no in vivo studies showing that these proteins are capable of interacting in tissues. We have isolated the mouse ortholog of Lu and characterized its expression and localization in mouse tissues. Lu was primarily found on the basal surface of epithelial cells and on muscle cells adjacent to basement membranes containing laminin alpha5. In addition, there was both a dramatic reduction in the basal concentration of Lu in mice lacking laminin alpha5, and a significant increase in Lu protein in transgenic mice overexpressing laminin alpha5. Together, these data provide the first in vivo evidence for an interaction between Lu and laminin alpha5 and support the hypothesis that Lu is a laminin alpha5 receptor. We propose that laminin alpha5 is involved in concentrating Lu on the basal surface of epithelial cells. This may be one mechanism by which basement membrane signals are transmitted to the cell.

The expression of membrane-associated 67-kDa laminin receptor (67LR) is modulated in vitro by cell-contact inhibition

The interaction of cells with their substratum is an important determinant of cell behaviour, influencing attachment, proliferation, and motility. Such interactions are mediated by cell surface receptors which bind to attachment factors, like the glycoprotein laminin in basement membranes. We have previously shown that expression of the 67-kDa laminin receptor (67LR) is elevated in proliferating retinal microvasculature compared with mature, quiescent vessels. Here, we examined 67LR mRNA and protein expression in primary cultures of retinal microvascular endothelial cells (RMEC) and in the breast cancer cell-line T47D during stages of contact inhibition. In both cell types, the expression levels of 67LR mRNA and membrane-associated 67LR protein were significantly increased during the proliferative phases of monolayer formation. As the cells achieved contact inhibition, 67LR expression was reduced to comparatively low levels. Thus, the differential expression of 67LR between dividing and contact-inhibited cells may indicate a role for this receptor during proliferative processes.