Surface modification to improve in vitro attachment and proliferation of human urinary tract cells

Tissue engineering for human urethral reconstruction: systematic review of recent literature

Background

Techniques to treat urethral stricture and hypospadias are restricted, as substitution of the unhealthy urethra with tissue from other origins (skin, bladder or buccal mucosa) has some limitations. Therefore, alternative sources of tissue for use in urethral reconstructions are considered, such as ex vivo engineered constructs.

Purpose

To review recent literature on tissue engineering for human urethral reconstruction.

Methods

A search was made in the PubMed and Embase databases restricted to the last 25 years and the English language.

Results

A total of 45 articles were selected describing the use of tissue engineering in urethral reconstruction. The results are discussed in four groups: autologous cell cultures, matrices/scaffolds, cell-seeded scaffolds, and clinical results of urethral reconstructions using these materials. Different progenitor cells were used, isolated from either urine or adipose tissue, but slightly better results were obtained with in vitro expansion of urothelial cells from bladder washings, tissue biopsies from the bladder (urothelium) or the oral cavity (buccal mucosa). Compared with a synthetic scaffold, a biological scaffold has the advantage of bioactive extracellular matrix proteins on its surface. When applied clinically, a non-seeded matrix only seems suited for use as an onlay graft. When a tubularized substitution is the aim, a cell-seeded construct seems more beneficial.

Conclusions

Considerable experience is available with tissue engineering of urethral tissue in vitro, produced with cells of different origin. Clinical and in vivo experiments show promising results.

Smooth muscle cell functionality on collagen immobilized polycaprolactone nanowire surfaces

Inhibition of smooth muscle cell (SMC) proliferation and preservation of a differentiated state are important aspects in the management, avoidance and progression of vascular diseases. An understanding of the interaction between SMCs and the biomaterial involved is essential for a successful implant. In this study, we have developed collagen immobilized nanostructured surfaces with controlled arrays of high aspect ratio nanowires for the growth and maintenance of human aortic SMCs. The nanowire surfaces were fabricated from polycaprolactone and were immobilized with collagen. The objective of this study is to reveal how SMCs interact with collagen immobilized nanostructures. The results indicate significantly higher cellular adhesion on nanostructured and collagen immobilized surfaces; however, SMCs on nanostructured surfaces exhibit a more elongated phenotype. The reduction of MTT was significantly lower on nanowire (NW) and collagen immobilized NW (colNW) surfaces, suggesting that SMCs on nanostructured surfaces may be differentiated and slowly dividing. Scanning electron microscopy results reveal that SMCs on nanostructured surfaces are more elongated and that cells are interacting with the nano-features on the surface. After providing differentiation cues, heavy chain myosin and calponin, specific to a contractile SMC phenotype, are upregulated on collagen immobilized surfaces. These results suggest that nanotopography affects cell adhesion, proliferation, as well as cell elongation, while collagen immobilized surfaces greatly affect cell differentiation.

Controlling the phenotype and function of mesenchymal stem cells in vitro by adhesion to silane-modified clean glass surfaces

The behaviour of human mesenchymal stem cells (hMSC) when cultured in contact with a range of silane-modified surfaces was examined to determine if changing the surface chemistry affected the early differentiation potential of mesenchymal stem cells in vitro over a 7-day period. Cells were cultured for 1 and 7 days in direct contact with glass which had been functionalized by surface treatment to provide a range of different surfaces: -CH(3), -NH(2), -SH, -OH, and -COOH modified surfaces and a clean glass reference (TAAB). Viable cell adhesion was quantified by Lactate Dehydrogenase assay, and morphology and viability was qualitatively evaluated using calcein AM, ethidium homodimer, cytoskeletal (F Actin), extra-cellular matrix (fibronectin and vitronectin) and Hoechst staining (nucleus). The expression of selected differentiation markers, Collagen II (chondrocytes), CBFA1 (bone transcription factor), Collagen I (MSC marker) and TGF-beta3 (extra-cellular matrix production) was determined using real time polymerase chain reaction. The expression of ornithine decarboxylase was evaluated as a marker of proliferation. Surfaces of the -NH(2) group demonstrated the greatest level of cell adhesion by the 7-day period, and mRNA expression profiles indicated osteogenic differentiation, increased CBFA1 and decreased Collagen II expression. Cells cultured in contact with the -COOH surfaces displayed different cell morphologies, fibronectin and vitronectin spatial distributions compared with the cells in contact with the -NH(2) surfaces, in addition to an increase in Collagen II expression, indicative of chondrogenic differentiation. The modifications to the surface chemistry of glass did affect cell behaviour, both in terms of viable cell adhesion, morphology and profiles of mRNA expression, providing the means to alter the differentiation potential of the MSCs.

Fibrillar collagen assembled in the presence of glycosaminoglycans to constitute bioartificial stem cell niches in vitro

Fibrillar collagen was reconstituted from mixtures of monomeric tropocollagen and heparin or hyaluronic acid, respectively. Turbidity measurements were utilized to follow the fibrillar assembly and demonstrated the influence of the concentration of the glycosaminoglycan on the maximum optical densities. Thin film coatings of maleic anhydride copolymers were utilized for the covalent immobilization of the fibrillar assemblies to solid supports. Quantification of surface-bound collagen was accomplished by ellipsometry and HPLC-based amino acid analysis indicating that less collagen was immobilized in the presence of the glycosaminoglycans. SEM and AFM revealed various sizes and shapes of the immobilized fibrillar assemblies if collagen fibrils were prepared in the presence of heparin or hyaluronic acid. Human hematopoietic stem cells (HSCs) were cultivated on the surface-bound collagen fibrils and the migration of adherent cells was studied by time-lapse microscopy. Migration rates on fibrillar structures were significantly lower then on tropocollagen indicating a more intimate contact of HSCs to the fibrillar substrates.

In Vitro Reconstitution of Fibrillar Collagen Type I Assemblies at Reactive Polymer Surfaces

The reconstitution of fibrillar collagen and its assemblies with heparin and hyaluronic acid was studied in vitro. Fibril formation kinetics were analyzed by turbidity and depletion measurements in solutions containing varied concentrations of collagen and glycosaminoglycans. Fibril-forming collagen solutions were further applied for the coating of planar substrates which had been modified with alternating maleic anhydride copolymer films before. The immobilized collagen assemblies were characterized with respect to the deposited amount of protein using ellipsometry and acidic hydrolysis/HPLC-based amino acid analysis, respectively. AFM, SEM, and cLSM were utilized to gain information on structural features and patterns formed by surface-attached fibrils depending on the initial solution concentrations of collagen. The results revealed that the addition of heparin and hyaluronic acid affected both the fibril dimensions and the meshwork characteristics of the surface-bound fibrils.