Abstract

The manner in which a mutually acceptable co-existence of biomaterials and tissues is developed and sustained has been the focus of attention in biomaterials science for many years, and forms the foundation of the subject of biocompatibility. There are many ways in which materials and tissues can be brought into contact such that this co-existence may be compromised, and the search for biomaterials that are able to provide for the best performance in devices has been based upon the understanding of all the interactions within biocompatibility phenomena. Our understanding of the mechanisms of biocompatibility has been restricted whilst the focus of attention has been long-term implantable devices. In this paper, over 50 years of experience with such devices is analysed and it is shown that, in the vast majority of circumstances, the sole requirement for biocompatibility in a medical device intended for long-term contact with the tissues of the human body is that the material shall do no harm to those tissues, achieved through chemical and biological inertness. Rarely has an attempt to introduce biological activity into a biomaterial been clinically successful in these applications. This essay then turns its attention to the use of biomaterials in tissue engineering, sophisticated cell, drug and gene delivery systems and applications in biotechnology, and shows that here the need for specific and direct interactions between biomaterials and tissue components has become necessary, and with this a new paradigm for biocompatibility has emerged. It is believed that once the need for this change is recognised, so our understanding of the mechanisms of biocompatibility will markedly improve.

Abstract

This study investigated cytotoxic effects of Ni(II) to mouse fibroblast cells (L-929) on the level of gene expression profiles with cDNA microarray. The gene expression profiles of L-929 were detected after the cells were cultured in the medium with 200 μm Ni(II) for 24, 48 and 72 h, respectively, and the cytotoxicity of Ni(II) was evaluated with methylthiazoltetrazolium (MTT) assay. 20 up-regulated genes and 19 down-regulated genes were differentially expressed in all three-culture periods. Gene ontology analysis showed that the L-929 cells which responded to Ni(II) covered a broad range of functional gene groups including cellular biological process, molecular function, and cellular component. Ni(II) has extensive effects on cells by inhibiting cell proliferation and differentiation through inducing cell apoptosis, affecting cell development and influencing cholesterol metabolism.

Abstract

Bone repairs represent a major focus in orthopedic medicine with biomaterials as a critical aspect of the regenerative process. However, only a limited set of biomaterials are utilized today and few studies relate biomaterial scaffold design to degradation rate and new bone formation. Matching biomaterial remodeling rate towards new bone formation is important in terms of the overall rate and quality of bone regeneration outcomes. We report on the osteogenesis and metabolism of human bone marrow derived mesenchymal stem cells (hMSCs) in 3D silk scaffolds. The scaffolds were prepared with two different degradation rates in order to study relationships between matrix degradation, cell metabolism and bone tissue formation in vitro. SEM, histology, chemical assays, real-time PCR and metabolic analyses were assessed to investigate these relationships. More extensively mineralized ECM formed in the scaffolds designed to degrade more rapidly, based on SEM, von Kossa and type I collagen staining and calcium content. Measures of osteogenic ECM were significantly higher in the more rapidly degrading scaffolds than in the more slowly degrading scaffolds over 56 days of study in vitro. Metabolic analysis, including glucose and lactate levels, confirmed the degradation rate differences with the two types of scaffolds, with the more rapidly degrading scaffolds supporting higher levels of glucose consumption and lactate synthesis by the hMSCs upon osteogenesis, in comparison to the more slowly degrading scaffolds. The results demonstrate that scaffold degradation rates directly impact the metabolism of hMSCs, and in turn the rate of osteogenesis. An understanding of the interplay between cellular metabolism and scaffold degradability should aid in the more rational design of scaffolds for bone regeneration needs both in vitro and in vivo.

Abstract

This study was conducted to determine the interaction of individual corrosion products from biodegradable iron stents with cells from the adjacent tissue. The response of human umbilical venous smooth muscle cells (SMCs) to an excess of ferrous ions was investigated in a cell culture model at the phenotypic and at the molecular level. When soluble ferrous ions were added to the cell culture medium the cell growth rate was reduced. Gene expression profiling indicated a reduction in the amounts of mRNA from genes that are required for cell proliferation. In addition, mRNA was regulated from multiple genes involved in iron homeostasis, DNA replication and lipid metabolism. In conclusion, ions released from iron stents could reduce the vascular SMC proliferation rate by influencing growth-related gene expression and may therefore play a beneficial role in antagonizing restenosis in vivo.

Abstract

To reveal molecular mechanisms of the interaction between Ni²⁺ and cells, cDNA microarray technology and GenMAPP analysis were utilized to investigate changes of gene expression profile and identify significant biological pathways in mouse fibroblast cells (L-929) treated by 100 μm Ni²⁺ for 12, 24, 48 and 72 h, respectively. The microarray data was validated by real-time PCR. Methylthiazoltetrazolium (MTT) analysis and flow cytometry experiment were used to assess the cellular response of L-929 cells to Ni²⁺. It was found that six main biological pathways were affected by Ni²⁺ with 118 differentially expressed genes involved. Further analysis illuminated that the exposure of cells to Ni²⁺ may evoke series of cellular responses to hypoxia by regulating hypoxia-inducible gene expression and cause irreversible DNA damage. Cell cycle pathway analysis results showed DNA replication in S phase could be inhibited by Ni²⁺ which was consistent with the data gained from flow cytometry experiment. Compared to previous researches based on conventional molecular biology experiments, the present work has not only indirectly validated the findings of other groups but also obtained several discoveries related to cell-Ni²⁺ interaction, such as inhibition of electron transport chain and accumulation of extracellular matrix (ECM) collagens. The routine of the present study not only can analyze gene expression profile but also may provide a more convenient and efficient approach to explain molecular mechanisms of cell–biomaterial interaction.

Abstract

The use of synthetic hydroxyapatite as bone substitute calls for the knowledge of the influence on adjacent cells. The aim of this study was to investigate the proteins with differential protein expression levels in the proteome of human osteoblast cell line incubated separately with various nano sized hydroxyapatite powders with different shapes and chemical compositions using iTRAQ-coupled 2D LC-MS/MS approach. In the present study, we investigated several intracellular signaling molecules involved in calcium regulation to analyze how osteoblast cells respond to dissimilar HA nanoparticles. It was found there was a significant decrease in cell population after adding the HA nanoparticles to the osteoblasts. Our results combining proteomics analysis and RT-PCR validation on targeted genes involved in calcium regulation confirmed the differences in the cellular response to dissimilar HA nanoparticles.

Summary

Bio-Oss^® (Geistlich, Wolhusen, Switzerland) is composed by anorganic bovine bone and is widely used in several bone regeneration procedures in oral surgery.

How this biomaterial alters osteoblast gene expression to promote bone formation is poorly understood. We therefore attempted to address this question by using microarray techniques to identify genes that are differentially regulated in osteoblasts exposed to Bio-Oss^®.

By using DNA microarrays containing 20,000 genes, we identified in osteoblast-like cells line (MG-63) cultured with Bio-Oss^® several genes which expression was significantly up- and down-regulated. The differentially expressed genes cover a broad range of functional activities: (a) signaling transduction, (b) transcription, (c) cell cycle regulation, (d) vesicular transport, (e) apoptosis, and (f) immunity. These results could explain the reported bioaffinity of Bio-Oss^® to host animals, its biological affinity to osteogenic cells and its capability to stimulate osteoblastic differentiation. The data reported are, to our knowledge, the first genetic portrait of Bio-Oss^® effects. They can be relevant to our improved understanding of the molecular mechanism underlying bone regenerative procedures and as a model for comparing other materials with similar clinical effects.

Abstract

Peripheral nerve regeneration can be enhanced by the stimulation of formation of bands of Büngner prior to implantation. Aligned electrospun poly(ε-caprolactone) (PCL) fibers were fabricated to test their potential to provide contact guidance to human Schwann cells. After 7 days of culture, cell cytoskeleton and nuclei were observed to align and elongate along the fiber axes, emulating the structure of bands of Büngner. Microarray analysis revealed a general down-regulation in expression of neurotrophin and neurotrophic receptors in aligned cells as compared to cells seeded on two-dimensional PCL film. Real-time-PCR analyses confirmed the up-regulation of early myelination marker, myelin-associated glycoprotein (MAG), and the down-regulation of NCAM-1, a marker of immature Schwann cells. Similar gene expression changes were also observed on cells cultured on randomly oriented PCL electrospun fibers. However, up-regulation of the myelin-specific gene, P0, was observed only on aligned electrospun fibers, suggesting the propensity of aligned fibers in promoting Schwann cell maturation.

Abstract

Previously we demonstrated that high throughput gene expression experiments can yield novel information about how cells respond to a collagen–glycosaminoglycan (GAG) three-dimensional culture environment. The goal of the current study was to determine which of these differences result from culture in a three-dimensional construct versus those caused simply by the presence of the collagen–GAG biomaterial. To make this distinction, cells were cultured both in collagen–GAG scaffolds fabricated using a phase separation method and on thin two-dimensional coatings of the same material. Control cells were grown on standard tissue culture polystyrene (TCPS). Cell response was measured using histology and microarray analysis and select results were verified with real time polymerase chain reaction (RT-PCR) assays. Genes involved in matrix remodeling (matrix components, matrix metalloproteinases and growth factors) and angiogenesis (VEGF, HGF and HMOX) were shown to be differentially expressed between the treatment conditions. Several matrix metalloproteinases (MMPs) were up regulated in mesh grown cell while some of their inhibitors (TIMPs) were down regulated. These results suggest that the three-dimensional presentation of the collagen–GAG material to the cells is required to stimulate the observed increase in fibroblast remodeling behavior.

Abstract

A goal of tissue engineering is to produce a scaffold material that will guide cells to differentiate and regenerate functional replacement tissue at the site of injury. Little is known about how cells respond on a molecular level to tissue engineering scaffold materials. In this work we used oligonucleotide microarrays to interrogate gene expression profiles associated with cell–biomaterial interactions. We seeded collagen–glycosaminoglycan meshes, a widely used tissue engineering scaffold material, with human IMR-90 fibroblasts and compared transcript levels with control cells grown on tissue culture polystyrene. Genes involved in cell signaling, extracellular matrix remodeling, inflammation, angiogenesis and hypoxia were all activated in cells on the collagen–GAG mesh. Understanding the impact of a scaffold on attached cells will facilitate the design of improved tissue engineering materials.