Novel autologous cell therapy in ischemic limb disease through growth factor secretion by cultured adipose tissue-derived stromal cells.

OBJECTIVE: The delivery of autologous progenitor cells into ischemic tissue of patients is emerging as a novel therapeutic option. Here, we report the potential impact of cultured adipose tissue-derived cells (ADSC) on angiogenic cell therapy. METHOD AND RESULTS: ADSC were isolated from C57Bl/6 mouse inguinal adipose tissue and showed high expression of ScaI and CD44, but not c-kit, Lin, CD34, CD45, CD11b, and CD31, compatible with that of mesenchymal stem cells from bone marrow. In coculture conditions with ADSC and human aortic endothelial cells (ECs) under treatment with growth factors, ADSC significantly increased EC viability, migration and tube formation mainly through secretion of vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF). At 4 weeks after transplantation of ADSC into the ischemic mouse hindlimb, the angiogenic scores were improved in the ADSC-treated group, which were evaluated with blood flow by laser Doppler imaging (LDI) and capillary density by immunostaining with anti-CD31 antibody. However, injected ADSC did not correspond to CD31, von Willebrand factor, and alpha-smooth muscle actin-positive cells in ischemic tissue. CONCLUSIONS: These adipose tissue-derived cells demonstrated potential as angiogenic cell therapy for ischemic disease, which appears to be mainly achieved by their ability to secrete angiogenic growth factors.

Lack of association between the hepatocyte growth factor receptor, c-met, and the anti-apoptotic action of bag-1 in endothelial cells.

Bag-1 is a novel multifunctional protein. It was identified based on its ability to bind the anti-apoptotic protein, bcl-2, and also reported to interact with the heat shock protein 70 kDa (Hsp70). Thus, bag-1 may modulate apoptosis and the chaperone activity. More interestingly, bag-1 can bind to several growth factor receptors or steroid hormone receptors and regulate their function and signaling. The receptor of hepatocyte growth factor (HGF), c-met, associated with bag-1 in a study measuring immunoprecipitation in endothelial cells, we decided to investigate the contribution of bag-1 to the anti-apoptotic action of HGF. Endogenous expression of bag-1 in endothelial cells was confirmed mainly in the cytosol fraction. The treatment of human recombinant HGF (rHGF) increased tyrosine kinase and ERK phosphorylation, whereas over-expression of bag-1 had no effect on this phosphorylation. In DNA synthesis as assessed by thymidine incorporation, over-expression of bag-1 also did not induce any additional increase. In contrast, in an assay of cell death as assessed by caspase activity and lactate dehydrogenase release, over-expression of bag-1 alone attenuated serum-free and tumor necrosis factor-alpha-induced cell death in endothelial cells. No synergistic effect was observed between bag-1 and rHGF. To further study the association of HGF and bag-1, we examined the effect of a deletion mutant of the bag-1 C-terminal region (CTR), because bag-1 CTR is necessary to bind to c-met. Unexpectedly, over-expression of bag-1 CTR also attenuated the endothelial cell death, similar to rHGF. Taken together, these results indicate that over-expression of bag-1 has an anti-apoptotic effect on endothelial cells independent of HGF signaling.

Mitogenic activity of oxidized lipoprotein (a) on human vascular smooth muscle cells.

Although oxidized lipoproteins may play an important role in the progression of atherosclerosis, no report has mentioned the significance of oxidized lipoprotein (a) (Lp[a]) in the pathogenesis of cardiovascular disease. Initially, we compared the mitogenic actions of Lp(a) and oxidized Lp(a) on human vascular smooth muscle cells (VSMC). Lp(a) significantly stimulated the growth of human VSMC in a dose-dependent manner, whereas oxidized Lp(a) showed a stronger stimulatory action on VSMC growth than native Lp(a). Interestingly, antioxidants probucol and fluvastatin inhibited the oxidation of Lp(a). Moreover, the stimulatory effect of oxidized Lp(a) on human VSMC growth was significantly inhibited by probucol. Finally, we elucidated the molecular mechanisms of how Lp(a) stimulated the growth of VSMC. Extracellular signal-regulated kinase (ERK), as those controlled by kinases, modulate critical cellular functions such as cell growth, differentiation, and apoptosis, was transiently phosphorylated by oxidized Lp(a) as well as native Lp(a) from 5 minutes, and the phosphorylation disappeared within 30 minutes. The degree of ERK phosphorylation by oxidized Lp(a) was much higher than that by native Lp(a). Administration of a specific inhibitor of MEK, PD 98059, significantly attenuated VSMC growth induced by native Lp(a) or oxidized Lp(a) in a dose-dependent manner (P<0.01). The current study demonstrated that oxidized Lp(a) is more potent than native Lp(a) in stimulating VSMC growth. Oxidized Lp(a) may play an important role in the pathogenesis of vascular disease.

Impairment of collateral formation in lipoprotein(a) transgenic mice: therapeutic angiogenesis induced by human hepatocyte growth factor gene.

BACKGROUND: Although lipoprotein(a) (Lp[a]) is a risk factor for atherosclerosis, no study has documented the effects of Lp(a) on angiogenesis. In this study, we examined collateral formation in peripheral arterial disease (PAD) model in Lp(a) transgenic mice. In addition, we examined the feasibility of gene therapy by using an angiogenic growth factor, hepatocyte growth factor (HGF), to treat PAD in the presence of high Lp(a). METHODS AND RESULTS: In Lp(a) transgenic mice, the degree of natural recovery of blood flow after operation was significantly lower than that in nontransgenic mice. Of importance, there was a significant negative correlation between serum Lp(a) concentration and the degree of natural recovery of blood flow (P<0.05). In addition, Lp(a) significantly stimulated the growth of vascular smooth muscle, accompanied by the phosphorylation of ERK. These data demonstrated the association of impairment of collateral formation with serum Lp(a) concentration. Thus, we examined the feasibility of therapeutic angiogenesis by using HGF, with the goal of progression to human gene therapy. Intramuscular injection of HGF plasmid resulted in a significant increase in blood flow even in Lp(a) transgenic mice, accompanied by the detection of human HGF protein. A significant increase in capillary density also was detected in Lp(a) transgenic mice transfected with human HGF compared with control (P<0.01). CONCLUSIONS: Overall, a high serum Lp(a) concentration impaired collateral formation. Although the delay of angiogenesis in high serum Lp(a) might diminish angiogenesis, intramuscular injection of HGF plasmid induced therapeutic angiogenesis in the Lp(a) transgenic ischemic hindlimb mouse model as potential therapy for PAD.

Deletion and insertion of a 192-residue peptide in the active-site domain of glycosyl hydrolase family-2 beta-galactosidases.

The monomeric multimetal-binding beta-galactosidase of Saccharopolyspora rectivirgula (srbg), a glycosyl hydrolase family-2 enzyme, has a unique sequence consisting of 192 amino acid residues with no similarity to known proteins. This 192-residue sequence (termed the "iota [iota] sequence") appears to be inserted into a sequence homologous to the active-site domain of the Escherichia coli lacZ enzyme (lacZbg). To assess the effects of the t sequence at specific sites of beta-galactosidase on the catalytic functioning and molecular properties of beta-galactosidase, deletion or insertion mutants of beta-galactosidases were constructed, expressed in LacZ- E. coli strains, and characterized: srbgdelta in which the iota sequence was deleted from srbg, and lacZbgI, in which the 192-residue iota sequence was inserted into the corresponding position (between Asp591 and Phe592) in the active-site domain of lacZbg. srbgdelta was a catalytically inactive, dimeric protein which retained multimetal-binding characteristics, suggesting that the iota sequence is very important for maintaining the structure necessary for the catalytic functioning and the monomeric structure of srbg but is not responsible for the unique metal ion requirements of srbg. On the other hand, lacZbgI existed as a mixture of a monomer, a tetramer, and higher multimers. The monomeric species was inactive, whereas the tetramer and other multimers were catalytically active (V(max )K(m) value, 25% of that of lacZbg) and highly specific for beta-D-galactoside. The tetrameric lacZbgI was activated by Mg2+ and Mn2+ with lowered metal affinities, and the stoichiometry of metal binding was unchanged from that of lacZbg. These results, along with the published stereo structure of lacZbg, suggest that, in lacZbgI, the inserted 192-residue iota peptide could fold independently of the lacZbg domains into a "sub-domain," lying distant from the active site and subunit interfaces.