Enhancement of hMSC In Vitro Proliferation by Surface Immobilization of a Heparin-Binding Peptide

The use of human Mesenchymal Stem Cells (hMSC) as therapeutic agents for advanced clinical therapies relies on their in vitro expansion. Over the last years, several efforts have been made to optimize hMSC culture protocols, namely by mimicking the cell physiological microenvironment, which strongly relies on signals provided by the extracellular matrix (ECM). ECM glycosaminoglycans, such as heparan-sulfate, sequester adhesive proteins and soluble growth factors at the cell membrane, orchestrating signaling pathways that control cell proliferation. Surfaces exposing the synthetic polypeptide poly(L-lysine, L-leucine) (pKL) have previously been shown to bind heparin from human plasma in a selective and concentration-dependent manner. To evaluate its effect on hMSC expansion, pKL was immobilized onto self-assembled monolayers (SAMs). The pKL-SAMs were able to bind heparin, fibronectin and other serum proteins, as demonstrated by quartz crystal microbalance with dissipation (QCM-D) studies. hMSC adhesion and proliferation were significantly increased in pKL-SAMs compared to controls, most probably related to increased heparin and fibronectin binding to pKL surfaces. This proof-of-concept study highlights the potential of pKL surfaces to improve hMSC in vitro expansion possible through selective heparin/serum protein binding at the cell-material interface.

Directional migration of vascular smooth muscle cells guided by synergetic surface gradient and chemical pattern of poly(ethylene glycol) brushes

Directional migration of cells in vitro can mimic corresponding biological events in vivo, which provides a way to determine the cascade responses in the tissue regeneration process and develop novel criteria for the design of tissue-inductive biomaterials. In this work, a density gradient of methoxy poly(ethylene glycol) brushes (from 0.37 to 0.95 chains/nm2) on plain and striped pattern surfaces was fabricated, using a dynamically controlled reaction process, and characterized by X-ray photoelectron spectroscopy and quartz crystal microbalance with dissipation. Adhesion and migration behavior of vascular smooth muscle cells were studied on the gradient and gradient-patterned surfaces. The vascular smooth muscle cells exhibited preferential orientation and enhanced directional migration on the gradient surface toward the lower end of the methoxy poly(ethylene glycol) density. By introducing methoxy poly(ethylene glycol) chemical striped patterns in parallel with the gradient direction on the surface, the extent of cell orientation and directional migration were significantly improved. Due to the synergetic effects of surface methoxy poly(ethylene glycol) striped patterns and gradient cues, almost all cells were oriented, and 67% of the cells were observed to move unidirectionally.

High surface water interaction in superhydrophobic nanostructured silicon surfaces: convergence between nanoscopic and macroscopic scale phenomena

In the present work, we investigate wetting phenomena on freshly prepared nanostructured porous silicon (nPS) with tunable properties. Surface roughness and porosity of nPS can be tailored by controlling fabrication current density in the range 40-120 mA/cm(2). The length scale of the characteristic surface structures that compose nPS allows the application of thermodynamic wettability approaches. The high interaction energy between water and surface is determined by measuring water contact angle (WCA) hysteresis, which reveals Wenzel wetting regime. Moreover, the morphological analysis of the surfaces by atomic force microscopy allows predicting WCA from a semiempiric model adapted to this material.

Nanofibrous electrospun barrier membrane promotes osteogenic differentiation of human mesenchymal stem cells

An electrospun polysulfone (PSU) was prepared as a barrier membrane for guided bone regeneration. The membrane was in nanoscale to prevent fibrous tissue infiltration and highly porous to allow permeation of oxygen and nutrients. The morphology and attachment, viability and proliferation, and differentiation and mineralization of human bone marrow mesenchymal stem cells (HBMSCs) were determined. Cells adhered and spread well on the PSU membrane with characteristic polygonal, fusiform shapes and radial extensions. The live/dead staining revealed that the membrane had no negative influence on cell viability. The proliferation rates of HBMSCs on PSU membranes were lower in comparison with tissue-culture polystyrene plate after 3 days of culture. However, differentiation activity was particularly expressed at high levels when cells were cultured on PSU membranes. The results based on the data suggest that the PSU electrospun membrane promoted the osteogenic differentiation of HBMSCs, displayed desirable in vitro biocompatibility, and has good potential as a barrier membrane.

Gradient patterning and differentiation of mesenchymal stem cells on micropatterned polymer surface

A micropatterned surface with different area ratios of cell-adhesive to nonadhesive surfaces was prepared by micropatterning poly(vinyl alcohol) on a polystyrene plate using photolithography. A gradient pattern of mesenchymal stem cells of different cell densities was generated by culturing the cells on a micropatterned surface. The effects of the cell density gradient on cell functions such as proliferation and differentiation were investigated. Cells seeded at a low density proliferated faster than cells seeded at a high density. Although mesenchymal stem cells seeded at both low and high densities showed osteogenic differentiation, the higher cell seeding density could initiate osteogenic differentiation at a faster rate than the low cell density. And high cell density was required to induce chondrogenic differentiation.

Modulation of collagen and keratin synthesis in co-cultures of fibroblasts and keratinocytes on hyaluronan-coated polysulfone membranes

Human epidermal keratinocytes and dermal fibroblasts were co-cultured on polysulfone (PSU) membranes, previously coated or not with hyaluronan (HA), and compared to monocultured keratinocytes and fibroblasts. The purpose was to define the interplay between both cell types and how it is influenced. The co-cultures reduced types I and III collagen levels, indicating that keratinocytes exerted an inhibition on matrix synthesis by fibroblasts. On the other hand, the amounts of keratins 17 and 10 were increased, suggesting that fibroblasts stimulate the production of keratins by keratinocytes. In contrast with naked PSU membranes, HA coatings increased types I and III collagens mRNA (messenger ribonucleic acid) levels, suggesting that HA counteracts the inhibition produced by keratinocytes. Changes were also observed in the expression of metalloproteinases (MMPs) on HA-coated PSU membranes. The presence of keratinocytes increased MMP1 and MMP3 synthesis by fibroblasts whereas HA exerted an inhibitory effect on MMP2 expression that depended on the culture conditions. The TGF-β3 mRNA levels were very high in co-cultures on PSU, whereas TGF-β1 mRNA was rather low; this was amplified on HA-coated membranes. These data provide a deeper insight into the intercellular interactions between dermal fibroblasts and keratinocytes, and their modulation by the culture support of these cells.