Transfection of adipocytes by gene gun-mediated transfer

Implantation of VEGF transfected preadipocytes improves vascularization of fibrin implants on the cylinder chorioallantoic membrane (CAM) model

The successful substitution or augmentation of soft tissues by implantation of three dimensional cell constructs, consisting of human preadipocytes and fibrin glue as a carrier matrix, requires a rapid and homogeneous vascularization of the whole implant in order to provide a sufficient blood supply of centrally situated cells. Previous investigations have shown that under in vivo conditions primary human preadipocytes induce vascularization of fibrin matrices by secretion of several growth factors, such as VEGF and bFGF. The current study investigates whether vascularization of implants can be improved by transplantation of preadipocytes following transfection with a VEGF-vector. Transfection was performed by electroporation with an pCMX-GFP and pCMX-VEGF165 vector. Transfection efficiency (GFP expression) and VEGF expression were determined in vitro by FACS analysis and VEGF immunoassay, respectively. In vivo investigations to determine the vascularization of the implants were performed on the cylinder chorioallantoic membrane (CAM). Four million VEGF transfected cells were transferred within a fibrin matrix onto the CAM on the 7(th) day of incubation and after 8 days the vascularization of the implant was histologically examined and evaluated by means of a computer-assisted image analysis program. Transfection of preadipocytes with the GFP vector by electroporation yielded transfection efficiencies between 12% and 41% of surviving cells. Results of the VEGF immunoassay demonstrated that VEGF expression was significantly higher following transfection. Investigations on the CAM outlined a significantly higher rate of vascularization in the transfected vs. control population. Our investigations demonstrate that primary human preadipocytes can be successfully transfected by electroporation with a VEGF vector. The enhanced VEGF expression on transfected cells results in an increase of vascularization of the cell constructs on the CAM.

The permeability transition pore triggers Bax translocation to mitochondria during neuronal apoptosis

Cerebellar granule neurons (CGNs) require depolarization for their survival in culture. When deprived of this stimulus, CGNs die via an intrinsic apoptotic cascade involving Bim induction, Bax translocation, cytochrome c release, and caspase-9 and -3 activation. Opening of the mitochondrial permeability transition pore (mPTP) is an early event during intrinsic apoptosis; however, the precise role of mPTP opening in neuronal apoptosis is presently unclear. Here, we show that mPTP opening acts as an initiating event to stimulate Bax translocation to mitochondria. A C-terminal (alpha9 helix) GFP-Bax point mutant (T182A) that constitutively localizes to mitochondria circumvents the requirement for mPTP opening and is entirely sufficient to induce CGN apoptosis. Collectively, these data indicate that the major role of mPTP opening in CGN apoptosis is to trigger Bax translocation to mitochondria, ultimately leading to cytochrome c release and caspase activation.

Somatic gene transfer into the lactating ovine mammary gland

BACKGROUND

Somatic gene therapy requires safe and efficient techniques for the gene transfer procedure. The ovine mammary gland is described as a model system for the evaluation of somatic gene transfer methods.

METHODS

Different gene delivery formulations were retrogradely injected into the mammary gland of lactating sheep. The efficiency of the gene transfer was subsequently measured by the detection of the secreted transgene products in the milk. To counteract the milk flow in the lactating gland caused by the permanent milk production, a newly developed pretreatment of the mammary gland with hyperosmotic solutions was applied. In addition, in vivo electroporation of DNA into the mammary gland is described.

RESULTS

Gene transfer using naked DNA or simple complexes of DNA with polycations did not result in traceable amounts of reporter gene products. However, utilizing the complex cationic lipid DOSPER, a peak expression of about 400 ng/ml was observed 6 days after transfection. Maximum expression rates of more than 1 microg/ml were obtained by combining hyperosmotic pretreatment and receptor-mediated gene transfer. For the in vivo electroporation, the proof of principle for this technique in the mammary gland is reported.

CONCLUSIONS

The ovine mammary gland turned out to be a very well suited as a model system for evaluation and optimization of various gene transfer protocols.

Chromosomal localization, expression pattern, and promoter analysis of the mouse gene encoding adipocyte-specific secretory protein Acrp30

Acrp30 is an abundantly expressed secretory protein exclusively synthesized in adipose tissue. Due to the dysregulation in various forms of obesity in humans and mice and its strong structural similarity to TNFalpha, it is currently under study as an important molecule involved in whole body energy homeostasis. Here we describe the sequence of mouse Acrp30 locus, define the intron/exon boundaries and map the gene to the telomere of mouse chromosome 16, syntenic to the human chromosomal locus 3q27. We demonstrate that alternative polyadenylation gives rise to two distinct mRNA species. We also show that Acrp30 expression is induced only at the late stages of mouse embryonic development. Finally, we have characterized the mouse Acrp30 promoter in tissue culture cells. We propose that Acrp30 promoter has the potential to drive strong adipocyte specific heterologous gene expression in transgenic mice.