Efficient adenoviral-mediated gene delivery into porcine mesenchymal stem cells.

Mesenchymal stem cell (MSC) mediated gene therapy research has been conducted predominantly on rodents. Appropriate large animal models may provide additional safety and efficacy information prior to human clinical trials. The objectives of this study were: (a) to optimize adenoviral transduction efficiency of porcine bone marrow MSCs using a commercial polyamine-based transfection reagent (GeneJammer, Stratagene, La Jolla, CA), and (b) to determine whether transduced MSCs retain the ability to differentiate into mesodermal lineages. Porcine MSCs (pMSCs) were infected under varying conditions, with replication-defective adenoviral vectors carrying the GFP gene and GFP expression analyzed. Transduced cells were induced to differentiate in vitro into adipogenic, chondrogenic, and osteogenic lineages. We observed a 5.5-fold increase in the percentage of GFP-expressing pMSCs when adenovirus type 5 carrying the adenovirus type 35 fiber (Ad5F35eGFP) was used in conjunction with GeneJammer. Transduction of pMSCs at 10.3-13.8 MOI (1,500-2,000 vp/cell) in the presence of Gene Jammer yielded the highest percentage of GFP-expressing cells ( approximately 90%) without affecting cell viability. A similar positive effect was detected when pMSCs were infected with an Ad5eGFP vector. Presence of fetal bovine serum (FBS) during adenoviral transduction enhanced vector-encoded transgene expression in both GeneJammer-treated and control groups. pMSCs transduced with adenovirus vector in the presence of GeneJammer underwent lipogenic, chondrogenic, and osteogenic differentiation. Addition of GeneJammer during adenoviral infection of pMSCs can revert the poor transduction efficiency of pMSCs while retaining their pluripotent differentiation capacity. GeneJammer-enhanced transduction will facilitate the use of adenoviral vectors in MSC-mediated gene therapy models and therapies.

Osteoinduction by ex vivo adenovirus-mediated BMP2 delivery is independent of cell type.

The objective of the study was to analyze and compare the abilities of various human cell types with inherently dissimilar osteogenic potentials to induce heterotopic bone formation following ex vivo transduction with two distinct adenoviral vectors encoding bone morphogenetic protein type 2 (BMP2). The cells comprised primary human bone marrow mesenchymal stem cells (BM-MSCs), primary human skin fibroblasts (SFs), and a human diploid fetal lung cell line (MRC-5). The vectors included adenovirus type 5 or a chimeric adenovirus type 5 with the fiber gene of adenovirus type 35 (Ad5F35-BMP2), both demonstrating significantly different expression of BMP2 in vitro. The experimental groups consisted of the three human cell types transduced with each of the two adenoviral vectors. Using nonobese diabetic severe combined immunodeficiency (NOD/SCID) mice, the transduced cells were injected intramuscularly following ex vivo adenoviral transduction. The nature and extent of heterotopic bone formation were analyzed radiographically and histologically. At 14 days postinjection, abundant, highly mineralized bone was formed in mice injected with Ad5F35-BMP2-transduced cells irrespective of the cell type. There was no statistically significant difference in the amount of bone formed between BM-MSCs, SFs, and MRC-5 cells transduced with Ad5F35-BMP2, as assessed from bone surface area on biplanar plain radiography. Substantially lesser amounts or no bone could be detected in mice injected with cells transduced with Ad5-BMP2. Immunohistochemical analysis confirmed the presence of human cells in muscle as early as 2 days postdelivery; however, at 6-7 days after injection, the transduced cells could not be detected in surrounding muscle, or in the heterotopic bone, indicating the host origin of the newly formed bone. The results of the study demonstrate no significant difference in osteoinductive properties between BM-MSCs, SFs, and MRC-5 cells transduced ex vivo with the same type of adenovirus encoding BMP2. The level of BMP2 expression appears to be a crucial factor determining the extent of heterotopic bone formation and was significantly affected by the type of adenovirus used. In the cell types studied, Ad5F35-BMP2 was more efficacious than Ad5-BMP2 in providing adequate levels of BMP2 for efficient osteoinduction.

Knock-in of nuclear localised beta-galactosidase reveals that the tyrosine phosphatase Ptprv is specifically expressed in cells of the bone collar.

Ptprv is a member of the transmembrane tyrosine phosphatase gene family reported to be expressed in osteoblasts and gonads. To better define the developmental and tissue specificity of Ptprv expression, we generated knock-in mice expressing a nuclear localised beta-galactosidase reporter under the control of resident Ptprv regulatory elements. Histochemical staining of Ptprv-nLacZ mice revealed that Ptprv expression is readily detectable in the foetal gonadal ridge of both sexes and in adult gonads where it is localised to Sertoli cells of the testis and celomic epithelial cells of the ovaries. During early limb development, Ptprv expression is prominent in the apical ectodermal ridge of the limb bud. At latter stages of development, Ptprv is predominantly expressed in the perichondrial and periosteal region of long bones, known as the bone collar. In contrast to previous indications from in vitro studies, there is little if any expression in mature osteoblasts in vivo. Analysis of Ptprv mRNA localisation by in situ hybridization in parallel with molecular markers of chondrocytes and osteoblasts confirmed the specific expression of Ptprv in immature bone collar cells. The specificity of Ptprv expression in these cells may be a useful tool to elucidate their role in the transition of skeletal elements from cartilage template to bone.