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Biomedical subjects

Michelle D Kofron

Publications and source records attributed to Michelle D Kofron.

6 recordsLinked to original sources
PubMed2004

Development of a calcium phosphate co-precipitate/poly(lactide-co-glycolide) DNA delivery system: release kinetics and cellular transfection studies.

One of the most common non-viral methods for the introduction of foreign deoxyribonucleic acid (DNA) into cultured cells is calcium phosphate co-precipitate transfection. This technique involves the encapsulation of DNA within a calcium phosphate co-precipitate, particulate addition to in vitro cell culture, endocytosis of the co-precipitate, and exogenous DNA expression by the transfected cell. In this study, we fabricated a novel non-viral gene transfer system by adsorbing DNA, encapsulated in calcium phosphate (DNA/Ca-P) co-precipitates, to biodegradable two- and three-dimensional poly(lactide-co-glycolide) matrices (2D-DNA/Ca-P/PLAGA, 3D-DNA/Ca-P/PLAGA). Co-precipitate release studies demonstrated an initial burst release over the first 48 h. By day 7, approximately 96% of the initially adsorbed DNA/Ca-P co-precipitate had been released. This was followed by low levels of co-precipitate release for 42 days. Polymerase chain reaction was used to demonstrate the ability of the released DNA containing co-precipitates to transfect SaOS-2 cells cultured in vitro on the 3D-DNA/Ca-P/PLAGA matrix and maintenance of the structural integrity of the exogenous DNA. In summary, a promising system for the incorporation and controlled delivery of exogenous genes encapsulated within a calcium phosphate co-precipitate from biodegradable polymeric matrices has been developed and may have applicability to the delivery of therapeutic genes and the transfection of other cell types.

Adsorption↗
PubMed2004

Protein- and gene-based tissue engineering in bone repair.

A tissue engineering approach to bone regeneration includes the use of a scaffold, cells and bioactive factors alone or in various combinations. Several investigators have demonstrated enhanced bone formation when the tissue-engineered construct possesses traits inherent to autogenic bone grafts, namely osteoconductivity, osteoinductivity and osteogenicity. Use of the biodegradable polymer poly(lactide-co-glycolide) in combination with bone morphogenetic protein or primary cells genetically modified to release osteogenic protein have demonstrated the ability to induce osteogenic differentiation of, and subsequent mineralization by, muscle-derived cells and mesenchymal stem cells in both in vitro and in vivo applications.

Animals↗
PubMed2004

Molecular regulation of osteoblasts for tissue engineered bone repair.

The use of biodegradable polymers in medicine and biomedical research is increasing. A key growth area has been the use of these materials in tissue engineering, especially for guided regeneration of bone and cartilage. Our interest has been in determining the mechanisms by which cellular attachment and growth occurs on these materials. In the current study, we examined human osteoblast cell adhesion, growth, and morphologic changes on polymeric scaffolds composed of polylactic-co-glycolic acid and polylactic acid materials. We examined these characteristics in association with measurements of levels of key adhesion integrin receptors in the presence and absence of antibodies against alpha2, alpha3, alpha4, alpha5, alpha6, and beta1 subunits, and the adhesion ligand peptides RGD (Arg-Gly-Asp) and RGE (Arg-Gly-Ser). At 2 hours, results showed initial cell adhesion was considerably decreased on polylactic-co-glycolic acid and polylactic acid in the presence of the alpha2 and beta1, antibodies with a 70% adhesion rate difference observed among the groups evaluated. Higher levels of inhibition were observed on polylactic-co-glycolic acid relative to polylactic acid, which may be correlated to a higher number of cells being able to interact with the surface initially. The presence of known competitive peptide (RGD) at 2 hours, revealed its ability to block cellular adhesion to these matrices relative to the control and noncompetitive peptide RGE on polylactic-co-glycolic acid matrices. Overall adhesion rate was affected by the presence of the integrin antibodies to the alpha2, alpha3, alpha4, alpha5, alpha6, and beta1 subunits with highest differences among polylactic-co-glycolic acid relative to its control, therefore suggesting that initial osteoblastic cell adhesion to commonly used biomaterials is regulated through integrin binding.

Biocompatible Materials↗
PubMed2003

In vitro bone formation using muscle-derived cells: a new paradigm for bone tissue engineering using polymer-bone morphogenetic protein matrices.

Over 800,000 bone grafting procedures are performed in the United States annually, creating a demand for viable alternatives to autogenous bone, the grafting standard in osseous repair. The objective of this study was to examine the efficacy of a BMP-polymer matrix in inducing the expression of the osteoblastic phenotype and in vitro bone formation by muscle-derived cells. Specifically, we evaluated the ability of bone morphogenetic protein-7 (BMP-7), delivered from a poly(lactide-co-glycolide) (PLAGA) matrix, to induce the differentiation of cells derived from rabbit skeletal muscle into osteoblast-like cells and subsequently form mineralized tissue. Results confirmed that muscle-derived cells attached and proliferated on the PLAGA substrates. BMP-7 released from PLAGA induced the muscle-derived cells to increase bone marker expression and form mineralized cultures. These results demonstrate the efficacy of a BMP-polymer matrix in inducing the expression of the osteoblastic phenotype by muscle-derived cells and present a new paradigm for bone tissue engineering.

Absorbable Implants↗
PubMed2003

Cryopreservation of tissue engineered constructs for bone.

The large-scale clinical use of tissue engineered constructs will require provisions for its mass availability and accessibility. Therefore, it is imperative to understand the effects of low temperature (-196 degrees C) on the tissue engineered biological system. Initial studies used samples of the osteoblast-like cell line (SaOS-2) adhered to a two-dimensional poly(lactide-co-glycolide) thin film (2D-PLAGA) or a three-dimensional poly(lactide-co-glycolide) sintered microsphere matrix (3D-PLAGA) designed for bone tissue engineering. Experimental samples were tested for their ability to maintain cell viability, following low temperature banking for one week, in solutions of the penetrating cryoprotective agents, dimethylsulfoxide (DMSO), ethylene glycol, and glycerol. Results indicated the DMSO solution yielded the greatest percent cell survival for SaOS-2 cells adhered to both the 2D- and 3D-PLAGA scaffolds; therefore, DMSO was used to cryopreserve mineralizing primary rabbit osteoblasts cells adhered to 2D-PLAGA matrices for 35 days. Results indicated retention of the extracellular matrix architecture as no statistically significant difference in the pre- and post-thaw mineralized structures was measured. Percent cell viability of the mineralized constructs following low temperature storage was approximately 50%. These are the first studies to address the issue of preservation techniques for tissue engineered constructs. The ability to successfully cryopreserve mineralized tissue engineered matrices for bone may offer an unlimited and readily available source of bone-like materials for orthopaedic applications.

Bone Substitutes↗