Constructing retroviral vector carrying green fluorescent protein(GFP)and investigating the expression of GFP in primary rat myoblast

Objective： To construct green fluorescent protein（GFP） retroviral vector（pLgXSN）, and to investigate the expression of GFP in primary rat myoblast. Methods： GFP cDNA was subcloned into the plasmid pLgXSN, and the recombinant vector was transfected into packaging cell PT67. G418 was used to select positive colony. Myoblasts were infected by a high-titer viral supernatant. The recombinant retroviral plasmid vector was identified by restriction endonuclease analysis and DNA sequence analysis. Confocal microscopy and flow cytometry were used to detect the expression of GFP. Results： The GFP cDNA sequence was identical to that of GenBank. Recombinant retroviral plasmid vector pLgGFPSN was constructed successfully. The titer of the packaged recombinant retrovirus was 1×10^6 cfu/ml. Bright green fluorescence of the transfected cells was observed under confocal microscope 48 h after transfection. The transfection rate was 33%. The effective expression of GFP in myoblast infected by recombinant retrovirus lasted for 6 weeks. Conclusion： GFP gene could be effectively and stably expressed in myoblast, which suggests that GFP could act as a marker for studies on myoblast.

Effects of recombinant retroviral vector mediated human insulin like growth factor-1 gene transfection on skeletal muscle growth in rat

Background This study transferred a recombinant gene encoding human insulin like growth factor-1 （hIGF-1） into modified primary skeletal myoblasts with a retroviral vector （pLgXSN） and determined whether the hIGF-1 promoted growth of skeletal muscle in rat.Methods hlGF-lcDNA was amplified in vitro from normal human liver cells by using RT-PCR and cloned into plasmid vector pLgXSN. The recombinant vector pLghIGF-1SN and control vector pLgGFPSN were transfected into packaging cell PT67 and G418 was used to select positive colony. Myoblasts were infected with a high titre viral supernatant and transduction efficiency was evaluated as GFP expression. The expression of hIGF-1 mRNA in myoblasts was investigated by immunocytochernistry and RT-PCR. MTT assays detected the growth of myoblasts in vitro. Myoblasts transduced with pLghlGF-1SN were injected into hind limb muscles of 10-12 week male SD rats. Formed tissues were harvested 4 weeks later. Myocyte diameter, mean weight of hind limb and body were measured to evaluate the skeletal muscle growth. Results Recombinant retroviral plasmid vector pLghlGF-1SN was constructed successfully. The titre of the packaged recombinant retrovirus was 1 × 106 cfu/ml. The transfection rate of PT67 cells reached 100% after G418 screening, hIGF-1 expression was positive in myoblast-IGF-1. The proliferation rate of myoblast-IGF-1 in vitro was higher than GFP-myoblast or myoblast （P〈 0.05）. The mean weights of hind limb and body of rats injected myoblast-IGF-1 were higher than those of the rats injected with myoblast-GFP or myoblast （P〈 0.05）. Myocyte diameter had a significant increase in IGF-1 group compared to GFP group and myobiast group （P〈 0.05）. Conclusions The transfection of the human IGF- 1 gene mediated by a retroviral vector can promote the growth of skeletal muscle in rats. Genetically modified primary skeletal myoblasts provide a possibly effective approach to treat some skeletal muscle diseases.

Hepatocyte growth factor improves right ventricular remodeling in pulmonary arterial hypertensive rats via decreasing neurohormonal activation and inhibiting apoptosis

Background Hepatocyte growth factor （HGF） inhibits the development of pulmonary artery hypertension （PAH） by reducing pulmonary artery pressure and right ventricle （RV） hypertrophy.However,whether HGF can prevent RV remodeling via inhibiting apoptosis in RV cardiomyocytes and decreasing neurohormonal activation remains unknown.Methods The PAH and subsequent RV remodeling in rats were induced by subcutaneous injection of monocrotaline （MCT）.The PAH rats were transfected with adenovirus carrying HGF （Ad-HGF） via intratracheal instillation.Three weeks after transfection,the hemodynamics indexes were measured,serum levels for angiotonin Ⅱ （ANG Ⅱ） and brain natriuretic peptide （BNP） were determined by ELISA.Histological analysis was used to assess the RV hypertrophy and fibrosis.The cardiomyocyte apoptosis in RV was assayed by TUNEL staining.The mRNA expression of BNP,angiotensin-converting enzyme （ACE）,Bax and Bcl-2 in RV was determined by reverse transcriptase polymerase chain reaction （RT-PCR）,the protein expression of transforming growth factor （TGF）-β1 and tumor necrosis factor （TNF）-α in RV was determined by Western blotting.Results HGF treatment significantly decreased the mean PAH,RV systolic pressure,serum ANG Ⅱ and BNP levels.HGF treatment also significantly decreased the RV hypertrophy,collagen deposition,and the number of apoptotic cardiomyocytes.Moreover,HGF treatmemt significantly decreased the expression of BNP,ACE,Bax,TGF-β1,and TNF-α,while it significantly increased the expression of Bcl-2.Conclusions Gene transfer of HGF decreases MCT-induced PAH and improves RV remodeling.This effect is mediated not only by improving the hemodynamics but also by decreasing neurohormonal activation and inhibiting cardiomyocytes apoptosis.HGF gene treatment may be an effective strategy for improving RV remodeling in MCT-induced PAH.

Recombinant human growth hormone secreted from tissue-engineered bioartificial muscle improves left ventricular function in rat with acute myocardial infarction

Background Experimental studies and preliminary clinical studies have suggested that growth hormone （GH） treatment may improve cardiovascular parameters in chronic heart failure （CHF）. Recombinant human GH （rhGH） has been delivered by a recombinant protein, by plasmid DNA, and by genetically engineered cells with different pharmacokinetic and physiological properties. The present study aimed to examine a new method for delivery of rhGH using genetically modified bioartificial muscles （BAMs）, and investigate whether the rhGH delivered by this technique improves left ventricular （LV） function in rats with CHE Methods Primary skeletal myoblasts were isolated from several Sprague-Dawley （SD） rats, cultured, purified, and retrovirally transduced to synthesize and secrete human rhGH, and tissue-engineered into implantable BAMs. Ligation of the left coronary artery or sham operation was performed. The rats that underwent ligation were randomly assigned to 2 groups： CHF control group （n=6） and CHF treatment group （n=6）. The CHF control group received non-rhGH-secreting BAM （GFP-BAMs） transplantation, and the CHF treatment group received rhGH-secreting BAM （GH-BAMs） transplantation. Another group of rats served as the sham operation group, which was also randomly assigned to 2 subgroups： sham control group （n=6） and sham treatment group （n=6）. The sham control group underwent GFP-BAM transplantation, and the sham treatment group underwent GH-BAM transplantation. GH-BAMs and GFP-BAMs were implanted subcutaneously into syngeneic rats with ligation of the left coronary artery or sham operation was performed. Eight weeks after the treatment, echocardiography was performed, hGH, insulin-like growth factor-1 （IGF-1） and TNF-a levels in rat serum were measured by radioimmunoassay and ELISA, and then the rats were killed and ventricular samples were subjected to immunohistochemistry. Results Primary rat myoblasts were retrovirally transduced to secrete rhGH and tissue-engineered into implantable BAMs containing parallel arrays of postmitotic myofibers. In vitro, they secreted 1 to 2 lug of bioactive rhGH per day. When implanted into syngeneic rat, GH-BAMs secreted and delivered rhGH. Eight weeks after therapy, LV ejection fraction （EF） and fractional shortening （FS） were significantly higher in CHF rats treated with GH-BAMs than in those treated with GFP-BAMs （（65.0i-6.5）% vs （48.1±6.8）%, P 〈0.05）, （（41.3±7.4）% VS （26.5±7.1）%, P 〈0.05）. LV end-diastolic dimension （LVEDD） was significantly lower in CHF rats treated with GH-BAM than in CHF rats treated with GFP-BAM （P 〈0.05）. The levels of serum GH and IGF-1 were increased significantly in both CHF and sham rats treated with GH-BAM. The level of serum TNF-α decreased more significantly in the CHF treatment group than in the CHF control group.Conclusions rhGH significantly improves LV function and prevents cardiac remodeling in rats with CHF. Genetically modified tissue-engineered bioartificial muscle provides a method delivering recombinant protein for the treatment of heart failure.

Recombinant proteins secreted from tissue-engineered bioartificial muscle improve cardiac dysfunction and suppress cardiomyocyte apoptosis in rats with heart failure

Background Tissue-engineered bioartificial muscle-based gene therapy represents a promising approach for the treatment of heart diseases. Experimental and clinical studies suggest that systemic administration of insulin-like growth factor-1 （IGF-1） protein or overexpression of IGF-1 in the heart exerts a favorable effect on cardiovascular function. This study aimed to investigate a chronic stage after myocardial infarction （MI） and the potential therapeutic effects of delivering a human IGF-1 gene by tissue-engineered bioartificial muscles （BAMs） following coronary artery ligation in Sprague-Dawley rats.Methods Ligation of the left coronary artery or sham operation was performed. Primary skeletal myoblasts were retrovirally transduced to synthesize and secrete recombinant human insulin-like growth factor-1 （rhIGF-1）, and green fluorescent protein （GFP）, and tissue-engineered into implantable BAMs. The rats that underwent ligation were randomly assigned to 2 groups： MI-IGF group （n=6） and MI-GFP group （n=6）. The MI-IGF group received rhIGF-secreting BAM （IGF-BAMs） transplantation, and the MI-GFP group received GFP-secreting BAM （GFP-BAMs） transplantation. Another group of rats served as the sham operation group, which was also randomly assigned to 2 subgroups： S-IGF group （n=6）and S-GFP group （n=6）. The S-IGF group underwent IGF-1-BAM transplantation, and S-GFP group underwent GFP-BAM transplantation. IGF-1-BAMs and GFP-BAMs were implanted subcutaneously into syngeneic rats after two weeks of operation was performed. Four weeks after the treatment, hemodynamics was performed. IGF-1 was measured by radioimmunoassay, and then the rats were sacrificed and ventricular samples were subjected to immunohistochemistry. Reverse transcriptase-polymerase chain reaction （RT-PCR） was used to examine the mRNA expression of bax and Bcl-2. TNF-α and caspase 3 expression in myocardium was examined by Western blotting.Results Primary rat myoblasts were retrovirally transduced to secrete rhlGF-1 and tissue-engineered into implantable BAMs containing parallel arrays of postmitotic myofibers. In vitro, they secreted consistent levels of hIGF （0.4-1.2 μg·BAM-1·d-1）. When implanted into syngeneic rat, IGF-BAMs secreted and delivered rhIGF. Four weeks after therapy,the hemodynamics was improved significantly in MI rats treated with IGF-BAMs compared with those treated with GFP-BAMs. The levels of serum IGF-1 were increased significantly in both MI and sham rats treated with IGF-BAM. The mRNA expression of bax was lower and Bcl-2 expression was higher in MI-IGF group than MI-GFP group （P ＜0.05）.Western blotting assay showed TNF-α and caspase 3 expression was lower in MI-IGF group than MI-GFP group after therapy.Conclusions rhIGF-1 significantly improves left ventricular function and suppresses cardiomyocyte apoptosis in rats with chronic heart failure. Genetically modified tissue- engineered BAMs provide a method delivering recombinant protein for the treatment of heart failure.