The matrix delivers

TMIGD1 is a novel adhesion molecule that protects epithelial cells from oxidative cell injury

Oxidative damage to renal tubular epithelial cells is a fundamental pathogenic mechanism implicated in both acute kidney injury and chronic kidney diseases. Because epithelial cell survival influences the outcome of acute kidney injury and chronic kidney diseases, identifying its molecular regulators could provide new insight into pathobiology and possible new therapeutic strategies for these diseases. We have identified transmembrane and immunoglobulin domain-containing 1 (TMIGD1) as a novel adhesion molecule, which is highly conserved in humans and other species. TMIGD1 is expressed in renal tubular epithelial cells and promotes cell survival. The extracellular domain of TMIGD1 contains two putative immunoglobulin domains and mediates self-dimerization. Our data suggest that TMIGD1 regulates transepithelial electric resistance and permeability of renal epithelial cells. TMIGD1 controls cell migration, cell morphology, and protects renal epithelial cells from oxidative- and nutrient-deprivation-induced cell injury. Hydrogen peroxide-induced oxidative cell injury downregulates TMIGD1 expression and targets it for ubiquitination. Moreover, TMIGD1 expression is significantly affected in both acute kidney injury and in deoxy-corticosterone acetate and sodium chloride (deoxy-corticosterone acetate salt)-induced chronic hypertensive kidney disease mouse models. Taken together, we have identified TMIGD1 as a novel cell adhesion molecule expressed in kidney epithelial cells that protects kidney epithelial cells from oxidative cell injury to promote cell survival.

Progenitor and stem cells for bone and cartilage regeneration

Research in regenerative medicine is developing at a significantly quick pace. Cell-based bone and cartilage replacement is an evolving therapy aiming at the treatment of patients who suffer from limb amputation, damaged tissues and various bone and cartilage-related disorders. Stem cells are undifferentiated cells with the capability to regenerate into one or more committed cell lineages. Stem cells isolated from multiple sources have been finding widespread use to advance the field of tissue repair. The present review gives a comprehensive overview of the developments in stem cells originating from different tissues and suggests future prospects for functional bone and cartilage tissue regeneration.

Localized and sustained SDF-1 gene release mediated by fibronectin films: A potential method for recruiting stem cells

Gene-activated matrix has wide potential utilization in tissue engineering. It may genetically modify cells with plasmid DNA encoding therapeutic genes and allow sustained expression and release of the proteins to surrounding tissues. In this study, we assessed the feasibility of the local gene release from human fibronectin (HFN) substrate and the efficacy of local release of stromal cell-derived factor-1 (SDF-1) gene on c-kit+ cell homing. Cationic polymer polyethylenimine (25kDa PEI) was used as non-viral DNA vector. Gene-activated HFN (GAH) was prepared by mixing PEI/DNA complexes with HFN substrate. The DNA retardation, the complex size, and the DNA release speed from the GAH were studied. The in vitro transfection was optimized by luciferase expression and cell viability assay in the COS7 cell line. Localized gene expression in COS7 cells cultured on the GAH was assessed by LacZ and GFP-N3-SDF-1 marker genes. Ckit+ cell homing was investigated in response to the local in vitro SDF-1 expression from rat mesenchymal stem cells (RMSCs) cultured on GAH. Results showed GAH allows long time-sustained DNA release, localized gene delivery, and high transfection efficiency. Local SDF-1 expression with GAH is a promising method to induce targetable stem cell homing.

Investigation of in vitro biocompatibility of novel pentablock copolymers for gene delivery

Novel pentablock copolymers of poly(diethylaminoethylmethacrylate) (PDEAEM), poly(ethylene oxide) (PEO), and poly(propylene oxide) (PPO), (PDEAEM-b-PEO-b-PPO-b-PEO-b-PDEAEM), were synthesized as vectors for gene delivery, and were tested for their biocompatibility on SKOV3 (human ovarian carcinoma) and A431 (human epidermoid cancer) cell lines under different in vitro conditions using various assays to elucidate the mechanism of cell death. These copolymers form micelles in aqueous solutions and can be tuned for their cytotoxicity by tailoring the weight percentage of their cationic component, PDEAEM. Copolymers with higher PDEAEM content were found to be more cytotoxic, though their polyplexes were less toxic than the polycations alone. Pentablock copolymers displayed higher cell viability than commercially available ExGen 500 at similar N:P ratios. While cell death with ExGen was found to be accompanied by an early loss of cell membrane integrity, pentablock copolymers caused very little membrane leakage. Caspase-3/7 assay confirmed that none of these polymers induced apoptosis in the cells. These pentablock copolymers form thermo-reversible gels at physiological temperatures, thereby enabling controlled gene delivery. Toxicity of the polymer gels was tested using an agarose-matrix, simulating an in vivo tumor model where injected polyplex gels would dissolve to release polyplexes, diffusing through tumor mass to reach the target cells. Twenty five weight percent of copolymer gels were found to be nontoxic or mildly cytotoxic after 24 h incubation. Transfection efficiency of the copolymers was found to be critically correlated to cytotoxicity and depended on DNA dose, polymer concentration, and N:P ratios. Transgene expression obtained was comparable to that of ExGen, but ExGen exhibited greater cell death.

Regulation of angiogenesis and matrix remodeling by localized, matrix-mediated antisense gene delivery

Implantation of biomaterials, such as glucose sensors, leads to the formation of a poorly vascularized collagenous capsule that can lead to implant failure. This process, known as the foreign body reaction (FBR), develops in response to almost all biomaterials and consists of overlapping phases similar to those in wound healing. Implantation of porous biomaterials, such as polyvinyl alcohol sponges, also leads to granuloma formation within the interstices of the sponge prior to encapsulation by the FBR. We asked whether delivery of an antisense cDNA for the potent angiogenesis inhibitor thrombospondin (TSP) 2 would enhance blood vessel formation and alter collagen fibrillogenesis in the sponge granuloma and capsule. Collagen solutions were mixed with plasmid to generate gene-activated matrices (GAMs) and applied to biomaterials that were then implanted subcutaneously. Sustained expression of plasmid-encoded proteins was observed at 2 weeks and a month following implantation. In vivo delivery of plasmids, encoding either sense or antisense TSP2 cDNA, altered blood vessel formation and collagen deposition in TSP2-null and wild-type mice, respectively. Untreated implants, implanted next to GAM-treated implants, did not show exogenous gene expression and did not elicit altered responses, suggesting that gene delivery was limited to implant sites. This method of antisense DNA delivery has the potential to improve the performance and life span of implantable delivery devices and biosensors.

Ionic products of bioactive glass dissolution increase proliferation of human osteoblasts and induce insulin-like growth factor II mRNA expression and protein synthesis

Bioglass 45S5 is an osteoproductive material, which resorbs by releasing its constitutive ions into solution. Treatment with the ionic products of Bioglass 45S5 dissolution in DMEM for 4 days increased human osteoblast proliferation to 155% of control. Two days after treatment, differential gene expression was analyzed by cDNA microarrays. Expression of a potent osteoblast mitogenic growth factor, insulin-like growth factor II (IGF-II), was increased to 290%. Additionally, there was a 168% increase in the concentration of unbound IGF-II protein in the conditioned media of treated osteoblasts. Expression levels of IGFBP-3, an IGF-II carrier protein, metalloproteinase-2 and cathepsin-D were also increased to 200, 340, and 310% of control levels, respectively. Metalloproteinase-2 and cathepsin-D are proteases that cleave IGF-II from its carrier proteins, resulting in the release of the unbound biologically active IGF-II. We suggest that the stimulatory effect of the ionic products of Bioglass 45S5 dissolution on osteoblast proliferation may be mediated by IGF-II.

The impact of tissue engineering on dentistry

BACKGROUND

Tissue engineering is a novel and highly exciting field of research that aims to repair damaged tissues as well as create replacement (bioartificial) organs.

OVERVIEW

The authors provide a general review of the principles underlying key tissue engineering strategies, as well as the typical components used. Several examples of preclinical and clinical progress are presented. These include passive approaches, such as dental implants, and inductive approaches that activate cells with specific molecular signals.

PRACTICE IMPLICATIONS

Tissue engineering will have a considerable effect on dental practice during the next 25 years. The greatest effects will likely be related to the repair and replacement of mineralized tissues, the promotion of oral wound healing and the use of gene transfer adjunctively.