Gene transfer strategies in tissue engineering

Abstract

Aiming for regeneration of severed or lost parts of the body, the combined application of gene therapy and tissue engineering has received much attention by regenerative medicine. Techniques of molecular biology can enhance the regenerative potential of a biomaterial by co-delivery of therapeutic genes, and several different strategies have been used to achieve that goal. Possibilities for application are many-fold and have been investigated to regenerate tissues such as skin, cartilage, bone, nerve, liver, pancreas and blood vessels. This review discusses advantages and problems encountered with the different gene delivery strategies as far as they relate to tissue engineering, analyses the positive aspects of polymeric gene delivery from matrices and discusses advances and future challenges of gene transfer strategies in selected tissues.

1

Genedelivery strategies in tissue engineering.ADNAsequence constituting the gene of interest which codes for the therapeutic protein is inserted into a suitable vector. Gene transfer into the host can now occur in four different ways: (A) Direct In vivo gene delivery or ex vivo gene transfer to either (B) cells or (C) Three-dimensional matrices, followed by transplantation of the genetically manipulated material into the host. Alternatively (B) and (C) can be combined whereby genetically modified cells are seeded onto threedimensional matrices followed by transplantation into the host.

2

Combination of bone tissue engineering, gene therapy based on human mesenchymal stem cells (MSCs) and silk fibroin biomaterials to study the impact of viral transfection on MSC osteogenic performance. MSCs were transduced with adenovirus containing a human BMP-2 (Ad-BMP-2) gene at clinically reasonable viral concentrations and cultured for 4 weeks. Controls with non-transfected MSCs, but exposed to exogenous BMP-2 concentrations on an analogous time profile as that secreted by the Ad-BMP-2 group, were compared. Both the Ad-BMP-2 MSC group and the exogenous protein BMP-2 group strongly expressed osteopontin and bone sialoprotein. Cells secreted a matrix that underwent mineralization on the silk fibroin scaffolds, forming clusters of osseous material, as determined by micro-computed tomography. The expression of osteogenic marker proteins and alkaline phosphatase was significantly higher in the Ad-BMP-2 MSC group than in the exogenous protein BMP-2 group, and no significant differences in mineralization were observed in two of the three MSC sources tested.The results demonstrate that transfection resulted in higher levels of expression of osteogenic marker genes, no change in proliferation rate and did not impact the capacity of the cells to calcify tissues on these protein scaffolds.These findings suggest additional options to control differentiation where exogenous additions of growth factors or morphogens can be replaced with transfected MSCs. Light microscopy of construct cross sections after 2 weeks (A–F) or 4 weeks (G–L) of cultivation in osteogenic medium (B, C, E, F, H, I, K, L) or control medium (A, D, G, J). MSC were either transduced with Ad-BMP-2 (center column) or exposed to BMP-2 concentrations as secreted and measured for the Ad-BMP-2 transduced cells (right column) or cultivated in control medium (left column). Sections were stained with H&E (A–C; G–I) or with von Kossa (D–F; J–L). Bar length is 100 μm. Reprinted from [63], with permission from Elsevier.