Fibronectin stimulates transcription of the platelet-derived growth factor beta-receptor in cultured rat aortic smooth muscle cells

Differential effect of nitric oxide on thrombospondin-1-, PDGF- and fibronectin-induced migration of vascular smooth muscle cells

BACKGROUND

Neointimal hyperplasia involves the migration of medial vascular smooth muscle cells (VSMCs) in response to arterial injury. Thrombospondin-1 (TSP1), platelet-derived growth factor (PDGF), and fibronectin (Fn) induce VSMC migration. Nitric oxide (NO) limits VSMC migration. The hypothesis of this study is that NO would dose dependently inhibit TSP1-induced, PDGF-induced, and Fn-induced VSMC chemotaxis.

METHODS

VSMCs were pretreated with serum free media or the NO donors diethylenetriamine NONOate or S-nitroso-N-acetyl-D,L-penicillamine. Chemotaxis to TSP1, PDGF, or Fn was determined. Analysis of variance with post hoc testing was done. P values < .05 were considered significant.

RESULTS

PDGF, TSP1, and Fn induced VSMC chemotaxis. NO donors inhibited chemotaxis of VSMCs to PDGF in a concentration-dependent manner. NO donors had a variable effect on TSP1-induced chemotaxis. NO donors did not inhibit Fn-induced chemotaxis.

CONCLUSION

The complex interactions of these proteins in vivo will need to be considered when developing NO-dependent therapies for neointimal hyperplasia.

Growth factors in the treatment of diabetic foot ulcers

BACKGROUND

Chronic foot ulceration is a major source of morbidity in diabetic patients. Despite traditional comprehensive wound management, including vascular reconstruction, there remains a cohort of patients with non-responding wounds, often resulting in amputation. These wounds may benefit from molecular manipulation of growth factors to enhance the microcirculation.

METHODS

A review of the current literature was performed using Pubmed, with secondary references obtained from key articles.

RESULTS AND CONCLUSION

There has been a generally disappointing clinical outcome from growth factor trials, although topical platelet-derived growth factor has shown significant benefit and should be considered in non-healing, well perfused ulcers after failure of conventional wound care. The modulatory role of the extracellular matrix in the cellular response to growth factors and data from regenerative-type fetal wound healing are further areas of interest. The chemical induction of microvessel formation may become a future therapeutic option.

Localization of extracellular matrix and mitogen-activated protein kinase (MAPK) in aorta of streptozotocin treated Mongolian gerbils

To evaluate the relationship among the extracellular matrix (ECM) and mitogen-activated protein kinase (MAPK) family for the vascular damages in hyperglycemia, we injected Mongolian gerbils intravenously with 150 mg/kg streptozotocin (STZ) and observed over the next one year the resulting aortic changes by immunohistochemical techniques. After STZ treatment, hyperglycemia was confirmed. At 4 weeks after STZ administration morphological observation revealed increased stromal components among the vascular smooth muscle cells (SMCs). Immunohistochemically, extracellular matrices such as fibronectin and laminin were localized in the aorta at 4 weeks and one year after STZ administration. The reaction products of MAPK in vascular SMCs were more increased at one year than at 4 weeks after STZ administration. After STZ administration, the increase of ECM and MAPK was observed in the aorta, which suggests these factors play important roles in the pathogenesis of macrovasculopathy in diabetes mellitus.

Mechanical stretch augments PDGF receptor beta expression and protein tyrosine phosphorylation in pulmonary artery tissue and smooth muscle cells

With regard to the mechanotransduction mechanisms of vasculature involved in hypertensive diseases, we aimed to identify tyrosine-phosphorylated proteins in pulmonary artery that responded to mechanical stress. Mechanical stretch simultaneously augmented protein-tyrosine phosphorylation in p55, p95, p105, p115, p130, p165, p180 in pulmonary artery tissue and pulmonary artery-derived smooth muscle cells (PASMC), whereas p115 and p55 were preferentially phosphorylated by the stretch in endothelial cells (PAEC). A series of experiments designed to characterize these proteins indicated that p115 and p180 were focal adhesion kinase (FAK) and platelet-derived growth factor receptor beta (PDGF-Rbeta), respectively, and that stretch augmented the surface-expression of PDGF-Rbeta in PASMC but not in PAEC. Moreover, a significant increase in the steady-state mRNA level for PDGF-Rbeta was observed in the pulmonary artery of rats with monocrotaline-induced pulmonary hypertension, where the artery should be overstretched due to increasing pulmonary arterial blood pressure. These results suggest that stretch-induced overexpression of cell-surface PDGF-Rbeta as well as augmentation of yrosine phosphorylation of proteins including FAK in PASMC might be involved in the mechanotransduction of pulmonary artery.

Isolation and partial characterization of myogenic cells from mussel larvae in vitro

The main finding of the present study is the discovery of the possibility of a morphofunctional myogenic differentiation of larval mussel cells in vitro. The shape and extensive cytoskeletal network of the cultured contracting cells mimic largely those of smooth muscle cells in vivo. However, the behavior and protein composition of these cells are not completely identical with those of smooth muscle cells. Contracting mussel cells in vitro, as well as differentiated smooth muscles, demonstrate both phasic and tonic contractions. The paramyosin to myosin ratio in the cultured mussel cells is far less than that in the muscles of veliger larvae and adult mussels. We have found the protein carpets with various adhesive characteristics determine different development pathways. Myogenic differentiation is only observed in spreading cells. Non-spreading adherent cells plated on collagen carpet show high synthetic activity but the commitment of contractile phenotype is inhibited. Our results confirm that the myogenic program established in early embryogenesis of molluscs can be realized during the cultivation of cells from premyogenic larval stages.

Enhanced expression of osteopontin by high glucose. Involvement of osteopontin in diabetic macroangiopathy

Atherosclerotic vascular disease is a major complication of diabetic patients. Osteopontin has recently been implicated in the development of atherosclerosis. In the present study, we have investigated the effects of high glucose on expression of osteopontin in cultured rat aortic smooth muscle cells. High concentrations of glucose increased osteopontin secretion from the cells, and the increased secretion was completely inhibited by an inhibitor of protein kinase C, GF109203X. Northern blot analysis confirmed the enhanced effect of glucose on expression of osteopontin mRNA. Promoter activity of osteopontin, measured using the osteopontin promoter/luciferase expression vector system, was increased by high glucose, and the enhanced effect was completely inhibited by GF109203X. Glucosamine also increased the promoter activity of osteopontin. Azaserine, an inhibitor of glutamine:fructose-6-phosphate amidotransferase, the key enzyme of the hexosamine pathway, profoundly inhibited high glucose-mediated increase in the promoter activity. Taken together, these data indicate that high glucose enhances the expression of osteopontin at the transcriptional level possibly through the activation of protein kinase C as well as the hexosamine pathway. Our results suggest that osteopontin could play a role in the development of diabetic vascular complications.

Enhanced expression of osteopontin in human diabetic artery and analysis of its functional role in accelerated atherogenesis

We have previously reported that high glucose stimulates osteopontin (OPN) expression through protein kinase C-dependent pathways as well as hexosamine pathways in cultured rat aortic smooth muscle cells. The finding prompted us to study in vivo expression of OPN in diabetes mellitus. In the present study, we found by immunohistochemistry that medial layers of the carotid arteries of streptozotocin-induced diabetic rats and the forearm arteries of diabetic patients stained positively for OPN antibodies, whereas the staining from arteries of control rats and nondiabetic patients was negative. We also found that OPN stimulated the migration and enhanced platelet-derived growth factor (PDGF)-mediated DNA synthesis of cultured rat aortic smooth muscle cells. OPN and PDGF synergistically activated focal adhesion kinase as well as extracellular signal-regulated kinase; this finding seems to explain the OPN-induced enhancement of PDGF-mediated DNA synthesis. Taken together, our present results raise a possibility that OPN plays a role in the development of diabetic vascular complications.

Enhanced expression of osteopontin by high glucose in cultured rat aortic smooth muscle cells

Atherosclerotic vascular disease is a major complication of diabetic patients, and osteopontin has recently been implicated in the development of atherosclerosis. In the present study, we have investigated the effects of high glucose on expression of osteopontin in cultured rat aortic smooth muscle cells. High concentrations of glucose increased osteopontin secretion from the cells, and the increased secretion was completely inhibited by an inhibitor of protein kinase C, GF109203X. Northern blot analysis confirmed the enhanced effect of glucose on expression of osteopontin mRNA. Promoter activity of osteopontin, measured using the osteopontin promoter/luciferase expression vector system, was increased by high glucose, and the enhanced effect was completely inhibited by GF109203X. Glucosamine also increased the promoter activity of osteopontin, and azaserine, an inhibitor of glutamine:fructose-6-phosphate amidotransferase (the key enzyme of the hexosamine pathway), profoundly inhibited high glucose-mediated increase in the promoter activity. Taken together, these data indicate that high glucose enhances the expression of osteopontin at the transcriptional level possibly through the activation of protein kinase C as well as the hexosamine pathway. Our results suggest that osteopontin could play a role in the development of diabetic vascular complications.