Arrangement of Type IV Collagen and Laminin on Substrates with Controlled Density of –OH Groups

Notch regulates vascular collagen IV basement membrane through modulation of lysyl hydroxylase 3 trafficking

Collagen type IV (Col IV) is a basement membrane protein associated with early blood vessel morphogenesis and is essential for blood vessel stability. Defects in vascular Col IV deposition are the basis of heritable disorders, such as small vessel disease, marked by cerebral hemorrhage and drastically shorten lifespan. To date, little is known about how endothelial cells regulate the intracellular transport and selective secretion of Col IV in response to angiogenic cues, leaving a void in our understanding of this critical process. Our aim was to identify trafficking pathways that regulate Col IV deposition during angiogenic blood vessel development. We have identified the GTPase Rab10 as a major regulator of Col IV vesicular trafficking during vascular development using both in vitro imaging and biochemistry as well as in vivo models. Knockdown of Rab10 reduced de novo Col IV secretion in vivo and in vitro. Mechanistically, we determined that Rab10 is an indirect mediator of Col IV secretion, partnering with atypical Rab25 to deliver the enzyme lysyl hydroxylase 3 (LH3) to Col IV-containing vesicles staged for secretion. Loss of Rab10 or Rab25 results in depletion of LH3 from Col IV-containing vesicles and rapid lysosomal degradation of Col IV. Furthermore, we demonstrate that Rab10 is Notch responsive, indicating a novel connection between permissive Notch-based vessel maturation programs and vesicle trafficking. Our results illustrate both a new trafficking-based component in the regulated secretion of Col IV and how this vesicle trafficking program interfaces with Notch signaling to fine-tune basement membrane secretion during blood vessel development.

Type IV collagen conforms to the organization of polylaminin adsorbed on planar substrata

Tissue engineering demands the development of scaffolds that mimic natural extracellular matrices (ECM). Despite the success in obtaining synthetic interstitial ECM, the production of an artificial basement membrane (BM), the specialized thin sheet of ECM that is pivotal for the functional organization of most tissues and internal organs, is still not achieved. With the long-term aim of developing a flat BM-like structure here we investigated the behavior of acid-soluble Col IV during simultaneous assembly with laminin (LM) in acidic conditions. The underlying rationale was the previously observed phenomenon of acid-triggered LM polymerization, giving rise to biomimetic polylaminin (polyLM) that can be adsorbed on the substrate. Unexpectedly, we found that Col IV (that does not polymerize in acidic conditions) readily incorporated into the polyLM layer, forming a network that mimics to a great extent the characteristic polygonal morphology of single polyLM observable at micrometric scale. Scanning calorimetry and light scattering measurements supported the notion that polyLM and Col IV could directly interact. The biological properties of the proposed artificial BM-like structure were characterized using human keratinocytes (HACAT) and umbilical vein endothelial cells (HUVEC). HACAT formed stratified cell layers on the hybrid polyLM/Col IV layer, but not on Matrigel, nor on LM or Col IV alone, while HUVEC improved cortical F-actin and tight juctions organization on polyLM/Col IV. Thus, the proposed artificial BM reproduces not only morphological but also some functional properties of the natural BM. STATEMENT OF SIGNIFICANCE: Basement membranes (BMs) are flat biological matrices separating tissue compartments in the body. Their peculiar sheet-like structure is thought to result from the association of two independent protein networks of laminin and collagen IV. While pursuing the development of an artificial BM, we found that, when mixed with acid-induced polymerized laminin, collagen IV immediately conformed to the laminin shape. This implies that the protein networks may not be independently assembled as believed so far, but instead that laminin may command the assembly of collagen IV. Our hybrid matrix was structurally more stable than the commercial BM extract Matrigel and, unlike the latter, supported in vitro formation of a stratified layer of keratinocytes that approximated the organization of the natural epidermis.

Collagen type-IV Langmuir and Langmuir-Schäfer layers as model biointerfaces to direct stem cell adhesion

In biomaterial development, the design of material surfaces that mimic the extra-cellular matrix (ECM) in order to achieve favorable cellular instruction is rather challenging. Collagen-type IV (Col-IV), the major scaffolding component of Basement Membranes (BM), a specialized ECM with multiple biological functions, has the propensity to form networks by self-assembly and supports adhesion of cells such as endothelial cells or stem cells. The preparation of biomimetic Col-IV network-like layers to direct cell responses is difficult. We hypothesize that the morphology of the layer, and especially the density of the available adhesion sites, regulates the cellular adhesion to the layer. The Langmuir monolayer technique allows for preparation of thin layers with precisely controlled packing density at the air-water (A-W) interface. Transferring these layers onto cell culture substrates using the Langmuir-Schäfer (LS) technique should therefore provide a pathway for preparation of BM mimicking layers with controlled cell adherence properties. In situ characterization using ellipsometry and polarization modulation-infrared reflection absorption spectroscopy of Col-IV layer during compression at the A-W interface reveal that there is linear increase of surface molecule concentration with negligible orientational changes up to a surface pressure of 25 mN m^-1. Smooth and homogeneous Col-IV network-like layers are successfully transferred by LS method at 15 mN m^-1 onto poly(ethylene terephthalate) (PET), which is a common substrate for cell culture. In contrast, the organization of Col-IV on PET prepared by the traditionally employed solution deposition method results in rather inhomogeneous layers with the appearance of aggregates and multilayers. Progressive increase in the number of early adherent mesenchymal stem cells (MSCs) after 24 h by controlling the areal Col-IV density by LS transfer at 10, 15 and 20 mN m^-1 on PET is shown. The LS method offers the possibility to control protein characteristics on biomaterial surfaces such as molecular density and thereby, modulate cell responses.

Osteogenic differentiation of mesenchymal stem cells using hybrid nanofibers with different configurations and dimensionality

Novel, hybrid fibrinogen/polylactic acid (FBG/PLA) nanofibers with different configuration (random vs aligned) and dimensionality (2-D vs 3-D environment) were used to control the overall behavior and the osteogenic differentiation of human adipose-derived mesenchymal stem cells (ADMSCs). Aligned nanofibers in both the 2-D and 3-D configurations are proved to be favored for osteodifferentiation. Morphologically, we found that on randomly configured nanofibers, the cells developed a stellate-like morphology with multiple projections; however, time-lapse analysis showed significantly diminished cell movements. Conversely, an elongated cell shape with advanced cell spreading and extended actin cytoskeleton accompanied with significantly increased cell mobility were observed when cells attached on aligned nanofibers. Moreover, a clear tendency for higher alkaline phosphatase activity was also found on aligned fibers when ADMSCs were switched to osteogenic induction medium. The strongest accumulation of Alizarin red (AR) and von Kossa stain at 21 days of culture in osteogenic medium were found on 3-D aligned constructs while the rest showed lower and rather undistinguishable activity. Quantitative reverse transcription-polymerase chain reaction analysis for Osteopontin (OSP) and RUNX 2 generally confirmed this trend showing favorable expression of osteogenic genes activity in 3-D environment particularly in aligned configuration. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2065-2074, 2017.

Dynamic Reorganization and Enzymatic Remodeling of Type IV Collagen at Cell-Biomaterial Interface

Vascular basement membrane remodeling involves assembly and degradation of its main constituents, type IV collagen (Col IV) and laminin, which is critical during development, angiogenesis, and tissue repair. Remodeling can also occur at cell-biomaterials interface altering significantly the biocompatibility of implants. Here we describe the fate of adsorbed Col IV in contact with endothelial cells adhering on positively charged NH2 or hydrophobic CH3 substrata, both based on self-assembly monolayers (SAMs) and studied alone or mixed in different proportions. AFM studies revealed distinct pattern of adsorbed Col IV, varying from single molecular deposition on pure NH2 to network-like assembly on mixed SAMs, turning to big globular aggregates on bare CH3. Human umbilical endothelial cells (HUVECs) interact better with Col IV adsorbed as single molecules on NH2 surface and readily rearrange it in fibril-like pattern that coincide with secreted fibronectin fibrils. The cells show flattened morphology and well-developed focal adhesion complexes that are rich on phosphorylated FAK while expressing markedly low pericellular proteolytic activity. Conversely, on hydrophobic CH3 substrata HUVECs showed abrogated spreading and FAK phosphorylation, combined with less reorganization of the aggregated Col IV and significantly increased proteolytic activity. The later involves both MMP-2 and MMP-9, as measured by zymography and FITC-Col IV release. The mixed SAMs support intermediate remodeling activity. Taken together these results show that chemical functionalization combined with Col IV preadsorption provides a tool for guiding the endothelial cells behavior and pericellular proteolytic activity, events that strongly affect the fate of cardiovascular implants.

Different Organization of Type I Collagen Immobilized on Silanized and Nonsilanized Titanium Surfaces Affects Fibroblast Adhesion and Fibronectin Secretion

Silanization has emerged in recent years as a way to obtain a stronger and more stable attachment of biomolecules to metallic substrates. However, its impact on protein conformation, a key aspect that influences cell response, has hardly been studied. In this work, we analyzed by atomic force microscopy (AFM) the distribution and conformation of type I collagen on plasma-treated surfaces before and after silanization. Subsequently, we investigated the effect of the different collagen conformations on fibroblasts adhesion and fibronectin secretion by immunofluorescence analyses. Two different organosilanes were used on plasma-treated titanium surfaces, either 3-chloropropyl-triethoxy-silane (CPTES) or 3-glycidyloxypropyl-triethoxy-silane (GPTES). The properties and amount of the adsorbed collagen were assessed by contact angle, X-ray photoelectron spectroscopy, optical waveguide lightmode spectroscopy, and AFM. AFM studies revealed different conformations of type I collagen depending on the silane employed. Collagen was organized in fibrillar networks over very hydrophilic (plasma treated titanium) or hydrophobic (silanized with CPTES) surfaces, the latter forming little globules with a beads-on-a-string appearance, whereas over surfaces presenting an intermediate hydrophobic character (silanized with GPTES), collagen was organized into clusters with a size increasing at higher protein concentration in solution. Cell response was strongly affected by collagen conformation, especially at low collagen density. The samples exhibiting collagen organized in globular clusters (GPTES-functionalized samples) favored a faster and better fibroblast adhesion as well as better cell spreading, focal adhesions formation, and more pronounced fibronectin fibrillogenesis. In contrast, when a certain protein concentration was reached at the material surface, the effect of collagen conformation was masked, and similar fibroblast response was observed in all samples.