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PubMed2005

Plasma levels of platelet-derived growth factor BB and transforming growth factor in patients with failed hip prostheses.

BACKGROUND: The role of growth factors in prosthesis loosening is unclear. We evaluated the levels of platelet-derived growth factor BB (PDGF-BB), transforming growth factors beta1 (TGF-beta1) and beta2 (TGF-beta2), both before and after activation, in patients with aseptic loosening of their hip prosthesis. PATIENTS AND METHODS: 26 patients with loosened hip implants were compared with 21 patients who had stable hip prostheses, and 28 patients undergoing primary hip replacement. The plasma levels of the growth factors were analyzed by enzyme immunoassay. TGF-beta1 and TGF-beta2 were determined both before and after activation. RESULTS: Patients with aseptic loosening had significantly lower PDGF-BB levels than patients undergoing primary hip replacement, and significantly lower TGF-beta2 levels than patients with a stable implant. Patients with stable prostheses had significantly higher TGF-beta1 and TGF-beta2 levels than patients undergoing primary hip replacement. INTERPRETATION: It is possible that the prosthetic implant itself causes a local increase in PDGF-BB, TGF-beta1 and TGF-beta2, released by osteoblasts and other cells in the microenvironment. The plasma PDGF-BB measured does not correspond to local release, which is probably due to local consumption or degradation. The consumption of PDGF-BB is low in stable implants, and TGF-beta1 and TGF-beta2 levels increase during bone formation. In loosening, PDGF-BB consumption is higher and causes a significant reduction in plasma levels as compared to presurgery. The formation of poor-quality bone may be related to the scarce increase in TGF-beta1 and TGF-beta2. In conclusion, compared with patients with a stable implant, a reduction in bone-forming growth factors appears to occur in individuals with aseptic loosening.

Adult↗
PubMed2000

Short-term stimulation of vascular smooth muscle cells with platelet-derived growth factor (PDGF)-BB and angiotensin II induces.

Growth factors such as the platelet-derived growth factor (PDGF)-BB and angiotensin II (Ang II) have been shown to induce vascular smooth muscle cell (VSMC) proliferation after long stimulation periods. Little is known though, about the effects of PDGF-BB and Ang II on VSMC proliferation after short stimulation periods. The purpose of our study was to examine whether a short term (3-60 min) stimulation of VSMC with PDGF-BB or Ang II is sufficient to induce cell proliferation. Incubation of VSMC with Ang II (100 nM) or PDGF-BB (50 ng/ml) caused a significant increase in [3H]thymidine incorporation starting after a 3-min stimulation, while the cell counts required 32 and 8 h of stimulation, respectively. Mitogen-activated protein kinase activation reached a maximum at 5-10 min of PDGF-BB or Ang II stimulation. This study demonstrates that the growth-promoting effects of PDGF-BB and Ang II are strongly dependent on the length of the stimulation period and that while prolonged stimulation periods (>8-32 h) result in VSMC proliferation, short ones (3-60 min) result only in [3H]thymidine incorporation without an increase in cell count, a fact of considerable pathophysiological significance, considering that the time kinetics of growth factors in the VSMC microenvironment have not as yet been clarified.

Angiotensin II↗
PubMed2003

Studies of cytokine levels in bronchoalveolar fluid lavage from patients with interstitial lung diseases.

Cytokine levels in bronchoalveolar lavage fluid from patients with eosinophilic pneumonia (n = 7), allergic alveolitis (n = 11), (cryptogenic) fibrosing alveolitis (n = 8), sarcoidosis (n = 10) were determined, as well as levels in control samples from healthy non-smoking volunteers (n = 11). Fibronectin levels were increased in all the patient categories, the highest absolute levels of fibronectin (100-fold increase) being found in eosinophilic pneumonia and allergic alveolitis. TGF-beta (transforming growth factor-beta) was significantly elevated in allergic alveolitis only. There was a significant difference between allergic alveolitis on the one hand and both sarcoidosis and fibrosing alveolitis on the other. Tumour necrosis factor-alpha (TNF-alpha) was significantly increased in eosinophilic pneumonia and allergic alveolitis; allergic alveolitis and fibrosing alveolitis differed significantly in this respect. Platelet-derived growth factor-BB (PDGF-BB) levels were significantly elevated in allergic alveolitis and fibrosing alveolitis. It was found that the level of PDGF-BB was significantly decreased in the case of sarcoidosis, with no overlapping with allergic alveolitis or fibrosing alveolitis. Interferon-gamma (IFN-gamma) was decreased in all patient categories. A significant difference in extent of the decrease was found between allergic alveolitis and sarcoidosis. The interstitial lung diseases thus differed in the pattern of cytokines expressed, indicating that these cytokines could well be a part of the pathogenic process, and also that the measurement of cytokine levels could be diagnostically useful.

Adult↗
PubMed1999

Carvastatin suppresses intimal thickening of rabbit carotid artery after balloon catheter injury probably through the inhibition of vascular smooth muscle cell proliferation and migration.

In order to test whether a 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor has an anti-atherogenic activity, the effects of carvastatin, a newly developed potent inhibitor, and pravastatin were examined on the intimal thickening of the artery after the endothelial denudation induced by balloon catheter injury. Rabbits were divided into four groups; control, pravastatin-treated (20 mg kg(-1) day(-1)) and two of carvastatin-treated groups (10 or 20 mg kg(-1) day(-1)). Two weeks after balloon catheter injury, the areas of intima and media of the injured carotid arteries were determined, and the ratios of intima to media (I/M) were calculated as an index of intimal thickening. Average I/M ratios of the injured artery were 0.42+/-0.05 for control, 0.49+/-0.07 for pravastatin, 0.19+/-0.03 (10 mg kg(-1) day(-1)) and 0.20+/-0.04 (20 mg kg(-1) day(-1)) for carvastatin-treated rabbits, respectively. Thus, carvastatin reduced I/M ratio of the injured artery to approximately half versus control, but pravastatin failed to suppress the intimal thickening. For in vitro study, vascular smooth muscle cells (SMC) from rabbit aorta were explanted, then cultured, and the effects of carvastatin on SMC migration and SMC proliferation were also examined. Carvastatin inhibited dose-dependently SMC migration and SMC proliferation with IC50 values of 0.5 microM and 1 microM, respectively. These inhibitory effects of carvastatin were cancelled by the coexistence of mevalonate, a metabolite of cholesterol synthesis. Our results suggest that carvastatin may be useful in rabbits as an anti-atherogenic drug by means of the inhibition of SMC migaration or SMC proliferation.

Animals↗
PubMed2001

PDGF-BB regulates IGF-mediated IGFBP-4 proteolysis in fetal lung fibroblasts.

Insulin-like growth factor (IGF)-stimulated lung fibroblast proliferation may be regulated by locally produced IGF-binding proteins (IGFBPs) during lung development. Recent evidence has shown that many growth factors participate in the regulation of cell proliferation by regulating IGFBPs. Because platelet-derived growth factor-BB (PDGF-BB) is highly expressed during lung development and is known to regulate IGFBP-4 production by lung cells, we examined the mechanisms by which PDGF-BB regulates ICFBP-4 production using primary cultures of 19-day gestation rat lung fibroblasts. Exposure of fetal rat lung fibroblasts to PDGF-BB increased IGFBP-4 mRNA transcript abundance by 3.6- and 2.4-fold at 18 and 40 hours, respectively. Addition of Rp-adenosine-3'-5'-cyclic monophosphothioate triethylamine (rp-cAMPS), a competitive inhibitor of protein kinase A, blunted the PDGF-BB-stimulated increase in conditioned medium (CM) IGFBP-4 and the increase in IGFBP-4 mRNA. Proteolysis of IGFBP-4 was detected in aliquots of cell-free CM from cells exposed to SFM for 48 hours. IGFBP-4 proteolysis was inhibited by EDTA and 1,10-phenanthroline and was accentuated by the addition of IGF-I and IGF-II and, to a lesser extent, by des(1-3)IGF-I. Exposure of cells to PDGF-BB for 48 hours resulted in an inhibition of IGFBP-4 proteolysis that was associated with a decrease in the concentration of IGF-I in CM. These studies demonstrate that PDGF-BB increases the accumulation of ICFBP-4 in fetal rat lung fibroblasts CM through increased production and by inhibiting IGF-mediated IGFBP-4 proteolysis.

Animals↗
PubMed2004

Regulation of insulin-like growth factor (IGF)-binding protein expression by growth factors and cytokines alters IGF-mediated proliferation of postnatal lung fibroblasts.

Postnatal day 5 is the beginning of septation and the peak of postnatal fibroblast proliferation. The author and colleagues studied fibroblasts from this developmental time period to determine factors that regulate cell proliferation. Exposure of cells to insulin-like growth factor (IGF)-I for 48 hours increased cell number whereas exposure to epithelial growth factor (EGF), platelet-derived growth factor (PDGF)-BB, fibroblast growth factor (FGF)-7, FGF-2, tumor necrosis factor-alpha (TNF-alpha), or interleukin (L)-1beta did not alter cell number. Long[R3]IGF-I (a synthetic IGF analog with reduced affinity for IGF-binding proteins [IGFBPs]) was more potent than IGF-I, with half-maximal stimulation at a dose of 0.6 nM for long[R3]IGF-I compared to 1.5 nM for IGF-I, suggesting that IGFBPs in the conditioned medium (CM) inhibit IGF activity. Addition of exogenous IGFBP-3 inhibited the IGF-stimulated increase in cell number. Addition of IGFBP-4 did not alter IGF activity because IGF-I stimulated proteolysis of IGFBP-4. The expression of mRNA for PAPP-A (a known IGFBP-4 protease) suggests that the clearance of IGFBP-4 is mediated by pregnancy-associated plasma protein (PAPP)-A. Exposure of cells to TNF-alpha or IL-1beta increased IGFBP-3 mRNA abundance and IGFBP-3 protein in CM. PDGF-BB and IL-1beta increased IGFBP-4 protein abundance and PDGF-BB and dibutyryl cAMP increased IGFBP-4 mRNA. The increase in CM IGFBP-3 following TNF-alpha exposure blocked IGF-mediated cell proliferation, suggesting that the growth factor- and cytokine-mediated changes in IGFBP abundance regulate postnatal fibroblast cell proliferation.

Animals↗
PubMedDate not supplied

PDGF and microvessel wall remodeling in adult lung: imaging PDGF-Rbeta and PDGF-BB molecules in progenitor smooth muscle cells developing in pulmonary hypertension.

Smooth muscle cells are relatively rare cells in the microvessels of the normal adult lung but develop in high numbers in the clinical pulmonary hypertensions (PHs). Understanding this cellular response has profound implications for determining the pathogenesis of PH, and for the development of therapeutic strategies, yet little is known of the angiogenic molecules responsible. The authors have previously shown that interstitial fibroblasts, and intermediate cells, are the progenitors of smooth muscle cells developing in adult lung microvessels in an in vivo model of experimental PH. The present study evaluates PDGF-Rbeta/PDGF-BB, an important angiogenic signaling pathway, using antibodies linked to protein A-gold (pA-AU) and quantitative high-resolution imaging techniques to detect expression by these cells. Each progenitor cell type in the control lung expressed PDGF-Rbeta and PDGF-BB. In the hypertensive lung, PDGF-Rbeta was highly expressed by fibroblasts developing as perivascular cells, the mean number of pA-AU labeled antigenic sites per cell profile, and their density (microm(-2)), increasing with time: in intermediate cells the mean number of sites per cell profile, although not their density (microm(-2)), also increased with time but less so than in the fibroblasts. In clear contrast to the RTK, constitutive expression levels of PDGF-BB were low in each progenitor cell type and remained restricted in the hypertensive lung.

Animals↗
PubMed2000

Transfer of platelet-derived growth factor-BB gene by gene gun increases contraction of collagen lattice by fibroblasts in diabetic and non-diabetic human skin.

We have used an in vitro model of wound contraction, the fibroblast-populated collagen lattice, to examine the effect of platelet-derived growth factor BB (PDGF-BB) and PDGF-BB gene transfer by gene gun on the contraction of lattices composed of either diabetic or non-diabetic human fibroblasts. The area of collagen lattice and DNA synthesis were measured in 12 specimens. There were significant increases in lattice contraction with increasing doses of PDGF-BB and fibroblasts transfected with the PDGF-BB gene compared with control (p < 0.01). DNA synthesis of the non-diabetic and diabetic fibroblast lattices showed significantly increased incorporation of tritiated thymidine with increasing doses of PDGF-BB and fibroblasts transfected with the PDGF-BB compared with controls (p < 0.05). The effect of PDGF-BB gene transfer on diabetic and non-diabetic fibroblasts was similar to that of 20 ng/ml or less of PDGF-BB.

Becaplermin↗
PubMed2003

Phosphorylation of extracellular signal-regulated protein kinase in cultured keloid fibroblasts when stimulated by platelet-derived growth factor BB.

Abnormal scars result in distressing symptoms and disfiguring blemishes; an understanding of the molecular events that cause such scars, particularly keloids, would make possible the optimisation of both wound healing and treatment. Extracellular signal-regulated protein kinase (ERK) has a crucial role in distinct signalling pathways in different cells, but to date we know of no study on its signalling events in keloid fibroblasts. The purpose of this study was to characterise the expression of tyrosine phosphorylation kinases, particularly that of ERK, in keloids at the protein level by immunoblotting analysis. Studies on phosphorylation were made on cell lysates of three cultures of five different keloid fibroblasts (n = 5), their relatively 'normal' fibroblasts in adjacent skin (rNHDF, n = 5), and normal human dermal fibroblasts (n = 1, standard control). The result showed that ERK signalling molecular protein was more highly phosphorylated in keloid fibroblast culture than in the other two cultures.

Adolescent↗
PubMed2002

Quantification of thrombocyte growth factors in platelet concentrates produced by discontinuous cell separation.

Platelet concentrates (PC) are increasingly used to increase bone regeneration in pre-prosthetic surgery. Although it is generally appreciated that certain growth factors (PDGF, TGF, EGF, and ECGF) are present in thrombocyte preparations, relatively little is known about these components in quantitative terms. The study reported here analysed the amounts of growth factors in PC produced under standard conditions from healthy volunteers. All the blood samples (237 in total) were analysed using Quantikine ELISA kits (R and D). The mean +/- SD platelet count in whole blood from these donors was 262,000+/-58,000/microl, while in PC produced by discontinuous cell separation it was 1.419,000+/-333,000/microl. The mean growth factor concentrations in PC preparations in ng/ml were as follows: PDGF-AB 125+/-55 ng/ml; TGF-beta1 221+/-92 ng/ml; IGF-I 85+/-25 ng/ml; PDGF-BB 14+/-9 ng/ml; TGF-beta2 0.4+/-0.3 ng/ml. These growth factor concentrations typically covered a 3-10 fold range: PDGF-AB 29-277ng/ml; PDGF-BB 2-33ng/ml; TGF-beta1 32-397ng/ml; TGF-beta2 0.1-1.2 ng/ml; IGF-I 40-138 ng/ml. Platelet counts in PC were slightly higher for women (Mann-Whitney Test all p < 0.001) than for men, while the concentrations of growth factors in PC exhibited no gender-related difference of any statistical significance.

Adult↗
PubMedDate not supplied

PDGF-BB induces expression of LTBP-1 but not TGF-beta1 in a rat cirrhotic fat storing cell line.

TGF-beta, a profibrogenic cytokine is predominantly secreted as a latent molecule complexed with one of the latent TGF-beta binding proteins (LTBP). Due to the proposed functions of LTBP-1 and -3 in regulating TGF-beta-bioavailability and -activity, we investigated the effects of PDGF-BB and TGF-beta1 on their expression levels in Cirrhotic fat storing cells (CFSC). CFSC basally express LTBP-1 and -3 and TGF-beta1. LTBP-1 colocalizes with LAP and the cells secrete some active TGF-beta1. Promoter studies showed no strong induction of the LTBP-1 promoters after stimulation, although mRNA and protein levels were increased by PDGF-BB treatment without affecting TGF-beta1 expression. Vice versa, TGF-beta1 treatment did not alter LTBP-1 expression while an autocrine induction was found. Our data indicate that LTBP-1 but not TGF-beta1 is induced by PDGF-BB and that TGF-beta1 autoinduction does not affect the expression of LTBP-beta1. This divergent regulation may represent an important mechanism for modulation of TGF-beta bioavailability.

Adipocytes↗
PubMed2005

Characterization of intracellular pathways leading to coinduction of thrombospondin-1 and TGF-beta1 expression in rat hepatic stellate cells.

Accumulating evidence has identified Thrombospondin (TSP)-1 as important activator of latent TGF-beta. Since little is known about signal transduction pathways regulating TSP expression in liver, we investigated cytokine-mediated upregulation of TSP-1 and TGF-beta1 in primary rat hepatic stellate cells (HSC). PDGF-BB and TNF-a rapidly coinduce mRNA levels of TSP-1 and TGF-beta1. Interestingly, blockade of basal Erk activity by synthetic Erk-binding peptides also leads to strong induction of both mRNA transcripts in non-stimulated cells. We show that PDGF-BB induces TSP-1 and TGF-beta1 via the src kinase pathway whereas TNF-a utilizes the MAPK/Erk pathway. However, especially TSP-1 induction by both cytokines involves a pathway, which depends to a certain extent on PI3 kinase activity. In summary the data illustrate specific pathways activated by PDGF-BB and TNF-a in HSC giving new insights into the tightly controlled mechanisms regulating TSP-1 and TGF-beta1 expression in these cells.

Animals↗
PubMed2000

Effect of heparin and related glycosaminoglycan on PDGF-induced lung fibroblast proliferation, chemotactic response and matrix metalloproteinases activity.

Fibroblast migration, proliferation, extracellular matrix protein synthesis and degradation are the key events in various biological and pathological processes in pulmonary fibrosis. In addition, biopsy specimens from the lungs of patients with pulmonary fibrosis show increased numbers of mast cells which have metachromatic granules containing heparin, histamine and proteases. Little is known about how these products influence pulmonary fibrosis. In the present study, we investigated the effect of heparin and related glycosaminoglycans on PDGF-induced lung fibroblast proliferation and chemotactic response in vitro. In addition, we examined the effect of heparin on both the induction of matrix metalloproteinases (MMPs) and MMPs activity in lung fibroblasts in vitro. Heparin, de-N-sulphated heparin but not heparan sulphate inhibited PDGF-induced lung fibroblast proliferation. In contrast, only heparin inhibited PDGF-stimulated human lung fibroblast chemotaxis. Negatively charged poly-L-glutamic acid had no effect on either fibroblast proliferation or chemotaxis. Thus the negative charge alone cannot account for the ant-proliferative and anti-chemotactic effects of heparin. Furthermore, heparin and heparan sulphate also had no inhibitory effect on induction of MMPS, including MMP-1 (interstitial collagenase), MMP-2 (gelatinase A) and MMP-9 (gelatinase B). Only heparin inhibited both MMP-1 and MMP-2/MMP-9 activity. Additionally, tissue inhibitor of metalloproteinase type 1 (TIMP-1) and type 2 (TIMP-2) inhibited PDGF-stimulated human lung fibroblast chemotaxis. The ability of heparin to inhibit fibroblast chemotaxis may account for the inhibitory effect of heparin on MMP activity. The above results suggested that heparin and related glycosaminoglycans differentially regulate PDGF-induced lung fibroblast proliferation, chemotaxis and MMPs activity and further that these effects may have a key role in extracellular matrix remodeling in inflammatory lung disease.

Becaplermin↗
PubMed2002

Topical platelet-derived growth factor in patients enhances wound closure in the absence of wound contraction.

Recombinant human platelet-derived growth factor (PDGF) is reported to promote wound closure in problem wounds. The mechanism of PDGF enhancement of wound closure is not clear. Does PDGF enhance wound contraction, or re-epithelialization, or both? In four patients undergoing elective surgery, a full excision 5 cm(2) punch wound was made behind each ear. The left post-articular wound received daily PDGF in a gel and each right post-articular wound received placebo-gel daily. The placebo-treated wounds closed in 19.8 days, while the PDGF-treated wounds closed significantly faster, in 15.6 days, p=0.002. At Day 20, all healed wounds were processed for histology. PDGF-treated wounds showed granulation tissue beneath an uninterrupted epidermis. A fine birefringence pattern, consistent with granulation tissue, was found by polarized light microscopy. The control closed-wounds had a smaller area of granulation tissue under an intact epidermis and polarized light microscopy showed mostly normal dermis. The presence of intact dermis within the closed-wound site is the hallmark of wound contraction. Topical PDGF limits the role of wound contraction in wound closure. Control wounds healed by wound contraction, while PDGF-treated wounds close by re-epithelialization and filling in with scar.

Administration, Topical↗
PubMed2005

Molecular signaling aptamers for real-time fluorescence analysis of protein.

Aptamers are a new class of nucleic acids that are selected in vitro for binding target molecules with high affinity and selectivity. They are promising protein-binding molecular probes that rival conventional antibodies for protein analysis. There have been recent advances in the development of molecular signaling aptamers that can transduce target protein binding to sensitive fluorescence signal changes. This facilitates the real time protein monitoring in homogenous solution as well as potentially in vivo. Different signaling strategies of using dual labeled aptamers based on fluorescence resonance energy transfer (FRET), one fluorophore labeled aptamers based on fluorescence anisotropy assay, or other label-free aptamers are reviewed.

Anisotropy↗
PubMed2006

Transforming growth factor-beta as a key molecule triggering the expression of versican isoforms v0 and v1, hyaluronan synthase-2 and synthesis of hyaluronan in malignant osteosarcoma cells.

Versican, a large sized chondroitin-sulphate proteoglycan (PG), and its binding partner, hyaluronan (HA), are extracellular matrix (ECM) components that play an essential role in transformed cell behavior. Expression of certain versican isoforms has been implicated in cell migration and proliferation of cancer cells and, on the other hand, disruption of HA synthesis by inhibiting hyaluronan synthase-2 (HAS2) expression in osteosarcoma cells by suppressing cell proliferation, invasiveness and motility. Considering that growth factors, such as TGF-beta, bFGF and PDGF-BB, are important regulators for the expression of the ECM macromolecules, in this study we examined the effect of these growth factors on the expression of the various versican isoforms, HA synthases as well as HA synthesis by MG-63 osteosarcoma cells and normal human osteoblastic periodontal ligament cells (hPDL). Real-time PCR and metabolic labelling followed by fine HPLC analysis coupled to radiochemical detection were the methods utilized. It was found that, contrary to normal hPDL cells, osteosarcoma MG-63 cells do not constitutively express the versican isoforms V0 and V1. Exogenous addition of TGF-beta2 stimulated the versican transcript levels mainly by forcing osteosarcoma cells to express V1 and V0 isoforms. PDGF-BB and bFGF had only minor effects in these cells. In hPDL cells a strong stimulation of the V3 transcript by all growth factors was observed. TGF-beta2 was also the major stimulator of HAS2 isoform expression as well as hyaluronan synthesis in osteosarcoma cells, while PDGF-BB exerted dominant influence on HAS2 isoform expression and hyaluronan biosynthesis by osteoblasts. The obtained results show for the first time that TGF-beta2 triggers the malignant phenotype pattern of versican and hyaluronan expression in human osteosarcoma cells and indicate that this growth factor may account for the metastatic potential of these cells.

Becaplermin↗
PubMedDate not supplied

Potentiation of mitogenic activity of platelet-derived growth factor by physiological concentrations of insulin via the MAP kinase cascade in rat A10 vascular smooth muscle cells.

Hyperinsulinemia has been shown to be associated with diabetic angiopathy. Migration and proliferation of vascular smooth muscle cells (VSMC) are the processes required for the development of atherosclerosis. In this study, we attempted to determine whether insulin affects mitogenic signaling induced by platelet-derived growth factor (PDGF) in a rat VSMC cell line (A10 cells). PDGF stimulated DNA synthesis which was totally dependent on Ras, because transfection of dominant negative Ras resulted in complete loss of PDGF-stimulated DNA synthesis. Initiation of DNA synthesis was preceded by activation of Raf-1, MEK and MAP kinases (Erk 1 and Erk2). Treatment of the cells with PD98059, an inhibitor of MAPK kinase (MEK) attenuated but did not abolish PDGF-stimulated DNA synthesis, suggesting that MAPK is required but not essential for DNA synthesis. PDGF also stimulated phosphorylation of protein kinase B (Akt/PKB) and p70 S6Kinase (p70S6K) in a wortmannin-sensitive manner. Rapamycin, an inhibitor of p70S6K, markedly suppressed DNA synthesis. Low concentrations of insulin (1-10 nmol/l) alone showed little mitogenic activity and no significant effect on MAPK activity. However, the presence of insulin enhanced both DNA synthesis and MAPK activation by PDGF. The enhancing effect of insulin was not seen in cells treated with PD98059. Insulin was without effect on PDGF-stimulated activations of protein kinase B (Akt/PKB) and p70S6K. We conclude that insulin, at pathophysiologically relevant concentrations, potentiates the PDGF-stimulated DNA synthesis, at least in part, by potentiating activation of the MAPK cascade. These results are consistent with the notion that hyperinsulinemia is a risk factor for the development of atherosclerosis.

Animals↗
PubMed1993

Mechanical strain induces growth of vascular smooth muscle cells via autocrine action of PDGF.

The effect of cyclic mechanical strain on growth of neonatal rat vascular smooth muscle (VSM) cells were examined. Cells were grown on silicone elastomer plates subjected to cyclic strain (60 cycle/min) by application of a vacuum under the plates. A 48 h exposure to mechanical strain increased the basal rate of thymidine incorporation by threefold and increased cell number by 40% compared with cells grown on stationary rubber plates. Strain also increased the rate of thymidine incorporation in response to alpha-thrombin (from 15- to 33-fold), but not to PDGF. As determined by thymidine autoradiography, strain alone induced a fourfold increase in labeled nuclei at the periphery of dishes, where strain is maximal, and a 2-3-fold increase at the center of dishes. Strain appeared to induce the production of an autocrine growth factor(s), since conditioned medium from cells subjected to strain induced a fourfold increase in DNA synthesis in control cells. Western blots of medium conditioned on the cells subjected to strain indicate that the cells secrete both AA and BB forms of PDGF in response to strain. Northern blots of total cell RNA from cells exposed to strain for 24 h show increased steady-state level of mRNA for PDGF-A. Lastly, polyclonal antibodies to the AA form of PDGF reduced by 75% the mitogenic effect of strain and polyclonal antibodies to AB-PDGF reduced mitogenicity by 50%. Antibodies to bFGF did not significantly reduce the strain-induced thymidine incorporation. Thus, the mechanism of strain-induced growth appears to involve the intermediary action of secreted PDGF.

Animals↗