Biomedical subjects

F J Villarreal

Publications and source records attributed to F J Villarreal.

At least 19 recordsLinked to original sources

PubMed2006

Localized CO2 laser damage repair of fused silica optics.

A technique has been developed for the localized treatment of laser damage sites in fused silica optics by CO2 laser melt-flow smoothing, by using a 50 to 125 microm diameter beam in a regime that avoids mass removal by ablation. A detailed calibration of the laser irradiance for the threshold ablation of craters was carried out for a range of beam diameters and pulses in the 20 micros to 200 ms range. The results agree with a thermal model that also provides estimates of the melt depth for the different irradiation conditions. Smoothing trials for glass melting at irradiance values just below the ablation threshold irradiance were conducted to determine the optimum conditions and limits for the smoothing process. The technique has been found to remove damage pits up to a depth of 0.5 microm, while the small melt depth associated with localized treatment limits the smoothing to a <or=5 microm lateral size.

Journal Article↗

PubMed2000

Time-dependent increases in type-III collagen gene expression in medical collateral ligament fibroblasts under cyclic strains.

Numerous studies have demonstrated the capacity of mechanical strains to modulate cell behavior through several different signaling pathways. Understanding the response of ligament fibroblasts to mechanically induced strains may provide useful knowledge for treating ligament injury and improving rehabilitation regimens. Biomechanical studies that quantify strains in the anterior cruciate and medial collateral ligaments have shown that these ligaments are subjected to 4-5% strains during normal activities and can be strained to 7.7% during external application of loads to the knee joint. The objective of this study was to characterize the expression of types I and III collagen in fibroblast monolayers of anterior cruciate and medial collateral ligaments subjected to equibiaxial strains on flexible growth surfaces (0.05 and 0.075 strains) by quantifying levels of mRNA encoding these two proteins. Both cyclic strain magnitudes were studied under a frequency of 1 Hz. The results indicated marked differences in responses to strain regimens not only between types I and III collagen mRNA expression within each cell type but also in patterns of expression between anterior cruciate and medial collateral ligament cells. Whereas anterior cruciate ligament fibroblasts responded to cyclic strains by expression of higher levels of type-I collagen message with almost no significant increases in type-III collagen, medial collateral ligament fibroblasts exhibited statistically significant increases in type-III collagen mRNA at all time points after initiation of strain with almost no significant increases in type-I collagen. Furthermore, differences in responses by fibroblasts from the two ligaments were detected between the two strain magnitudes. In particular, 0.075 strains induced a time-dependent increase in type-III collagen mRNA levels in medial collateral ligament fibroblasts whereas 0.05 strains did not. The strain-induced changes in gene expression of these two collagens may have implications for the healing processes in ligament tissue. The differences may explain, in part, the healing differential between the anterior cruciate and medial collateral ligaments in vivo.

Adult↗

PubMed2000

Leukemia Inhibitory Factor and Interleukin-6 downregulate sarcoplasmic reticulum Ca2+ ATPase (SERCA2) in cardiac myocytes.

Alterations in gene expression are a hallmark of cardiac hypertrophy and heart failure. Among these, the decreased expression of the sarcoplasmic reticulum calcium ATPase (SERCA2) has been described. Elevated levels of cytokines in particular, Leukemia Inhibitory Factor (LIF) and Interleukin-6 (IL-6) have been shown to have the capacity to elicit hypertrophic responses in cultured cardiac myocytes. In this study, we investigated the effects of these cytokines (LIF & IL-6) on the regulation of SERCA2 levels in cardiac myocytes. Cultured neonatal rat ventricular myocytes were transfected with a 3.2 kb promoter plasmid construct containing the SERCA2 promoter linked to a chloramphenicol acetyltransferase (CAT) reporter gene, and subsequently treated with 10 ng/ml LIF or 10 ng/ml IL-6. LIF and IL-6 independently caused a significant (p < or = 0.05) 23-36% inhibition in SERCA2 promoter activity. LIF and IL-6 induced inhibition was also evident in SERCA2 mRNA levels as assessed by Northern analysis. Time course of inhibition of SERCA2 mRNA levels showed the most prominent decrease occurring after 48 hours of treatment, with both cytokines having a dose dependent effect on the inhibitory response. Western analysis using a polyclonal antibody to SERCA2 protein indicate a significant, 60% decrease in the amount of total SERCA2 protein in cultured myocytes treated with 10 ng/ml LIF or IL-6. In conclusion, the cytokines LIF and IL-6 downregulate SERCA2 gene expression and protein levels. The molecular mechanism responsible for cytokine induced downregulation of SERCA2 is at least partly transcriptional.

Animals↗

PubMed2000

Role of mechanical factors in modulating cardiac fibroblast function and extracellular matrix synthesis.

The cardiac fibroblast is the most abundant cell type present in the myocardium and is mainly responsible for the deposition of extracellular matrix (ECM). Important components of cardiac ECM include structural and adhesive proteins such as collagen and fibronectin. Excess deposition of cardiac ECM (fibrosis) has been associated with the pathophysiological mechanical overload of the heart. Therefore, the role of cardiac fibroblasts in "sensing", "integrating" and "responding" to mechanical stimuli is of great interest. The development of in vitro strain apparatuses has allowed scientists to investigate the effects of mechanical stimuli on cardiac fibroblast function. Cardiac fibroblasts express ECM receptors (integrins) which couple mechanical stimuli to functional responses. Mechanical stimulation of cardiac fibroblasts has been shown to result in activation of various signal transduction pathways. The application of defined mechanical stimuli to cultured cardiac fibroblasts has been associated with ECM gene expression, growth factor production, release and/or bioactivity as well as collagenase activity. Ultimately, for fibrosis to develop the overproduction of ECM must overcome any associated increases in collagenase activity. Mechanically induced upregulation of ECM production may follow direct or indirect pathways through the autocrine or paracrine action of growth factors. Given the complex nature of the interstitial milieu of the working heart, additional research is needed to further our understanding of the roles that mechanical stimuli play in excess deposition of myocardial ECM.

Angiotensin II↗

PubMed2000

Thyroid hormone-induced stimulation of the sarcoplasmic reticulum Ca(2+) ATPase gene is inhibited by LIF and IL-6.

We investigated the effects of the leukemia inhibitory factor (LIF) and interleukin-6 (IL-6) on 3,3', 5-triiodo-L-thyronine, or thyroid hormone (T(3))-stimulated sarcoplasmic reticulum Ca(2+) ATPase (SERCA2) gene expression on cultured neonatal rat cardiac myocytes. A reduction of T(3) induced increases in SERCA2 mRNA levels after co-treatment with LIF or IL-6. To investigate for the molecular mechanism(s) responsible for the blunted gene expression, a 3.2-kb SERCA2 promoter construct containing a reporter gene was transfected into cardiac myocytes. T(3) treatment stimulated transcriptional activity twofold, whereas co-treatment with T(3) and either of the cytokines caused an inhibition of T(3)-induced SERCA2 transcriptional activity. A T(3)-responsive 0.6-kb SERCA2 construct also showed a similar inhibition by cytokines. Cytokine inhibition of SERCA2 transcriptional activity was also evident when a 0.6-kb SERCA2 mutant, T(3)-unresponsive promoter construct was used. Treatment with T(3) and cytokines showed a significant decrease in transcription when a reporter construct was used that was comprised of direct repeats of SERCA2 thyroid response element I. These data provide evidence for cytokine-mediated inhibitory effects on the SERCA2 promoter that may be mediated by interfering with T(3) action.

Animals↗

PubMed1999

Tumor necrosis factor-alpha upregulates angiotensin II type 1 receptors on cardiac fibroblasts.

Angiotensin II (Ang II) plays an important role in post-myocardial infarction (MI) remodeling. Most Ang II effects related to remodeling involve activation of the type 1 receptor (AT(1)). Although the AT(1) receptor is upregulated on cardiac fibroblasts post-MI, little is known about the mechanisms involved in the process. Consequently, we tested whether growth factors known to be present in the remodeling heart increased AT(1) mRNA levels. Using quantitative competitive reverse transcription-polymerase chain reaction, we found that norepinephrine, endothelin, atrial natriuretic peptide, and bradykinin had no significant effect on AT(1) mRNA levels. Ang II, transforming growth factor-beta(1), and basic fibroblast growth factor reduced AT(1) mRNA levels (P<0.02). Tumor necrosis factor-alpha (TNF-alpha), however, produced a marked increase in AT(1) mRNA. After 24 hours of TNF-alpha incubation, AT(1) mRNA increased by 5-fold above control levels (P<0.01). The EC(50) for the TNF-alpha effect was 4.6 ng/mL (0.2 nmol/L). Interleukin (IL)-1beta caused a 2.4-fold increase, whereas IL-2 and IL-6 had no significant effect. Studies of TNF-alpha enhancement of AT(1) mRNA levels demonstrate that the increase was not due to a change in transcript stability. TNF-alpha treatment for 48 hours also resulted in a 3-fold increase in AT(1) surface receptor and a 2-fold increase in Ang II-induced production of inositol phosphates. The present findings provide evidence for TNF-alpha regulation of AT(1) receptor density on cardiac fibroblasts. Because TNF-alpha concentration and AT(1) receptor density increase in the myocardium after MI, these results raise the possibility that TNF-alpha modulates post-MI remodeling by enhancing Ang II effects on cardiac fibroblasts.

Angiotensin II↗

PubMed1999

Regulation of cardiac fibroblast extracellular matrix production by bradykinin and nitric oxide.

The beneficial effects of angiotensin-converting enzyme inhibitors on ameliorating cardiac fibrosis have been partially attributed to their ability to prevent the degradation of kinins. The potential role of bradykinin and the related signaling molecule nitric oxide (NO) in modulating extracellular matrix (ECM) production was examined in primary cultures of adult rat cardiac fibroblasts. Treatment of fibroblasts with 5 nM bradykinin for 24 h led to a reduction in steady-state mRNA levels for fibronectin (34 +/- 7%) and collagens type I (19 +/- 8%) and type III (48 +/- 4%), as determined by Northern blot analysis. The NO synthase inhibitor L-NAME attenuated the reduction observed in fibronectin and collagen mRNA levels in response to bradykinin. The NO donor DETA NONOate (100 microM) mimicked the effects of bradykinin on ECM mRNA levels. Protein levels of soluble fibronectin, assessed in conditioned medium by ELISA, were decreased by 14 +/- 4% and 21 +/- 4% after 48 h treatment with 1 microM bradykinin and 100 microM DETA NONOate, respectively. Bradykinin stimulated intracellular cGMP accumulation 73.7 +/- 10.3% after 10 min of treatment. Cell proliferation rates at 48 h were unaffected by bradykinin, but were reduced by 26 +/- 12% by 100 microM DETA NONOate. These data indicate that bradykinin downregulates ECM protein production in cardiac fibroblasts and suggest that NO and the related signaling molecule cGMP may play an important role in mediating this response.

Animals↗

PubMed1999

Differential responses of adult cardiac fibroblasts to in vitro biaxial strain patterns.

Different patterns of extracellular matrix (ECM) remodeling in the heart are thought to be dependent on altered mechanical and chemical conditions and can contribute to cardiac dysfunction. Cardiac fibroblasts are the primary regulators of the ECM and may respond to mechanical factors in vitro. We hypothesized that different types of in vitro strains, e.g. tensile or compressive, can stimulate different functional responses in cultured adult rat cardiac fibroblasts. In this study, we first showed that a single step in strain applied by a uniaxial stretch system stimulated collagen III and fibronectin mRNA levels and transforming growth factor-beta(1) (TGF-beta(1)) activity in the adult phenotype of rat cardiac fibroblasts. Two-dimensional deformations were measured by tracking fluorescent microspheres attached to the substrate and cultured cells. For 10% uniaxial strain, mean principal strains were 0. 104 +/- 0.018 in the direction of stretch and -0.042 +/- 0.013 in the perpendicular direction, verifying that the fibroblasts were simultaneously subjected to tensile (positive) and compressive (negative) strains. Furthermore, these cells were also subjected to area change and to shear. In order to examine the distinct effects of different types of deformation on cardiac fibroblasts, an equibiaxial stretch system was used to apply either pure tensile or compressive area strains, in the absence of shear. Magnitudes of equibiaxial strain were selected to apply local cell area changes identical to those applied in the uniaxial system. Results showed that pure tensile and compressive area strains induced divergent responses in ECM mRNA levels. TGF-beta(1) activity was dependent on the magnitude of applied area strain regardless of the mode of deformation. These findings demonstrate that adult cardiac fibroblasts may respond differently to varied types of mechanical loading, suggesting that ECM remodeling may be locally regulated by specific mechanical stimuli in the heart.

Animals↗

PubMed1999

Nicotine-modified postinfarction left ventricular remodeling.

Cigarette smoking has been noted to impair wound healing in tissues such as skin, bone, and gut. This study was designed to examine whether nicotine adversely affects postinfarction cardiac wound healing and remodeling in an experimental model of myocardial infarction. For this purpose, two groups of rats were studied. The control group received a simple bandage, and the nicotine group had a section (1.75 mg/day) of a nicotine patch attached on their backs. After a 7-day treatment period, an anterior wall infarction was induced. A bandage-free 7-day healing period followed, after which hearts were isolated for mechanical tests. Nicotine-treated rats developed significantly enlarged left ventricles with thin, infarcted walls and a rightward shift in the passive pressure-volume relationship. Pressure-strain analysis also indicated possible changes in the material properties of the wound for nicotine-treated rats. In conclusion, nicotine has significant adverse effects on postinfarction healing and left ventricular remodeling. These observations have important clinical implications because of the enhanced risk for development of heart failure.

Animals↗

PubMed1998

Human cardiac fibroblasts and receptors for angiotensin II and bradykinin: a potential role for bradykinin in the modulation of cardiac extracellular matrix.

Evidence derived from in vivo experimental studies performed with angiotensin converting enzyme inhibitors (ACEi) indicates that these agents are capable of modulating the process of cardiac hypertrophy and fibrosis. The antifibrotic actions of ACEi are thought to be derived from their capacity to block the production of angiotensin II and, thus, its action on the cardiac fibroblast. However, in contrast to rat hearts, human myocardium has low levels of angiotensin II receptors. Evidence indicates that enhanced bradykinin (BK) levels result from the action of ACEi. In vivo data derived from the use of the BK blocker HOE140 suggests a role for BK in repressing the process of cardiac hypertrophy and fibrosis. Little is known as to the abundance of angiotensin II and BK receptors in human cardiac fibroblasts. Data presented in this study indicates that in cultured human cardiac fibroblasts there is apparently few angiotensin II receptors whereas as in other species there is evidence for the presence of BK receptors. Further studies need to be performed to establish the potential role that BK plays in modulating human cardiac fibroblast function.

Bradykinin↗

PubMed1996

Adenovirus-mediated overexpression of human transforming growth factor-beta 1 in rat cardiac fibroblasts, myocytes and smooth muscle cells.

Transforming growth factor-beta 1 (TGF-beta 1) is known to regulate cardiac cell function and its overexpression in the heart is thought to contribute to the development of cardiac hypertrophy and fibrosis. We wished to develop a high efficiency gene transfer method that could be used both in vitro and in vivo and result in the overexpression of TGF-beta 1. For this purpose, we constructed a replication-deficient human adenovirus 5 vector encoding for human TGF-beta 1 and used for control purposes an adenovirus lacZ vector. The adenovirus 5 construct was capable of infecting neonatal rat cardiac myocytes, fibroblasts and VSMCs. Of the three cell types, cardiac myocytes appear more susceptible to infection by the adenovirus 5 construct as assessed through beta-galactosidase staining. Infection of cardiac fibroblasts, myocytes and VSMCs with the hTGF-beta 1 adenovirus leads to the expression of hTGF-beta 1 mRNA and enhanced levels of bioactive and total TGF-beta 1 protein. Infection with hTGF-beta 1 adenovirus also results in enhanced levels of collagen type III gene expression in VSMCs and fibroblasts whereas in cardiac myocytes it leads to increased levels for sarcomeric and beta-actin. Thus, this adenoviral vector might be used for the exploration of in vivo effects of altered levels of cardiac TGF-beta 1.

Adenoviridae↗

PubMed1996

Phorbol myristate acetate-induced hypertrophy of neonatal rat cardiac myocytes is associated with decreased sarcoplasmic reticulum Ca2+ ATPase (SERCA2) gene expression and calcium reuptake.

The decreased expression of the sarcoplasmic reticulum Ca(2+)-ATPase associated with cardiac hypertrophy was investigated in cultured neonatal rat cardiac myocytes. Northern blot analysis indicated a significant 55-60% decrease in Ca(2+)-ATPase mRNA levels and after 12 and 24 h of treatment with the phorbol ester phorbol myristate acetate (PMA). Myocytes treated with the phorbol ester for 80 h showed a significant 34% decrease (relative to vehicle-treated control cells) in the levels of Ca(2+)-ATPase protein, and a significant 38% increase in the levels of alpha-sarcomeric actin, as assessed by Western blot analysis using specific antibodies. Immunocytochemistry of myocytes treated for 72 h with the phorbol ester revealed a hypertrophied cell morphology, and showed a marked decrease in Ca(2+)-ATPase staining intensity. Contractile calcium transients were evaluated through the use of indo-1. It was found that the t1/2 for the decline of calcium transient was significantly prolonged by PMA treatment (0.51 +/- 0.15) when compared to controls (0.38 +/- 0.17, P < 0.001). Treatment of myocytes with endothelin-1 also led to a 35% decrease in sarcoplasmic reticulum Ca(2+)-ATPase mRNA levels. It is concluded that phorbol ester treatment of neonatal rat cardiac myocytes induces similar changes in Ca(2+)-ATPase mRNA levels. It is concluded that phorbol ester treatment of neonatal rat cardiac myocytes induces similar changes in Ca(2+)-ATPase gene expression as observed in vivo in the hypertrophied and failing heart. The observed prolongation in t1/2 for [Ca2+]i decline might be due to the observed depressed levels for sarcoplasmic reticulum Ca(2+)-ATPase in PMA treated cells.

Animals↗

PubMed1996

An equibiaxial strain system for cultured cells.

We developed a device that applies homogeneous equibiaxial strains of 0-10% to a cell culture substrate and quantitatively verified transmission of substrate deformation to cultured cardiac cells. Clamped elastic membranes in both single-well and multiwell versions of the device are uniformly stretched by indentation with a plastic ring, resulting in strain that is directly proportional to the pitch-to-radius ratio. Two-dimensional deformations were measured by tracking fluorescent microspheres attached to the substrate and to cultured adult rat cardiac fibroblasts. For nominal stretches up to 18%, strains along circumferential and radial axes were equal in magnitude and homogeneously distributed with negligible shear. For 5% stretch, circumferential and radial strains in the substrate were 0.046 +/- 0.005 and 0.048 +/- 0.004 [not significant (NS)], respectively, and shear strain was 0.001 +/- 0.003 (NS). Calibration of both single-well and multiwell versions permits strain selection by device rotation. The reproducible application and quantification of homogeneous equibiaxial strain in cultured cells provides a quantitative approach for correlating mechanical stimuli to cellular transduction mechanisms.

Animals↗

PubMed1995

Angiotensin II stimulates the autocrine production of transforming growth factor-beta 1 in adult rat cardiac fibroblasts.

Angiotensin II (Ang II) has been implicated in the development of cardiac hypertrophy and myocardial fibrosis. While recent in vivo and in vitro studies performed in cultured cardiac myocytes and fibroblasts support this role for Ang II, the mechanisms of Ang II action at the cellular level remain unclear. In the present study, we postulated that Ang II action in adult cardiac fibroblasts may stimulate the autocrine production and release of transforming growth factor-beta 1 (TGF-beta 1), a known regulator of cardiac fibroblast and myocyte function. We examined the ability of Ang II to regulate the gene expression, biological activity, and protein production of TGF-beta 1 in cultured adult rat cardiac fibroblasts. Treatment of fibroblast cultures with Ang II (10(-9) M) induced a two-fold increase in TGF-beta 1 mRNA levels within 4 h that was sustained through 24 h (P < 0.01). TGF-beta 1-like activity in Ang II-treated cultures was significantly increased compared with control as measured by bioassay (P < 0.001). Specificity for TGF-beta 1-like activity was confirmed through its neutralization with a TGF-beta 1 specific antibody (100 micrograms/ml). Total concentration of TGF-beta 1 (latent plus active forms) in conditioned media from Ang II-treated cardiac fibroblasts was also found to be greater than control (P < 0.01). These findings suggest that the effects of Ang II in the adult myocardium may be mediated in part by autocrine/paracrine mechanisms, including the production and release of TGF-beta 1 by cardiac fibroblasts.

Angiotensin II↗

PubMed1995

Trophic effects of angiotensin II on neonatal rat cardiac myocytes are mediated by cardiac fibroblasts.

Cultured neonatal rat cardiac fibroblasts (NF) and myocytes (NM) were used to examine the distribution of angiotensin II (ANG II) receptors and the potential role of NF in mediating the trophic response to ANG II in the heart. In NM preparations cultured for 2-5 days, specific binding to 125I-ANG II was < 10% of the specific binding in cultured NF. Binding assays, immunocytochemistry, and autoradiography in NM cultured for > 5 days identified two populations of cells, one with fibroblast-like morphology and high density of ANG II receptors and another with low binding, comparable to NM cultures at day 5 or earlier. Conditioned medium (CM) from untreated NF increased cell surface area and net [3H]leucine (Leu) incorporation 1.4-fold in NM. CM from ANG II-treated NF enhanced [3H]Leu incorporation 2.2-fold in NM. This potentiating effect of ANG II was inhibited by losartan and was absent when ANG II was added directly to NM. In addition, studies using antibodies and bioassay for transforming growth factor-beta 1 (TGF-beta 1) suggested that TGF-beta 1 does not mediate the trophic effects of ANG II on NM. We conclude that ANG II receptors are localized predominantly on NF and that ANG II can indirectly stimulate hypertrophy of NM by stimulating NF to produce a transferrable factor(s). These data suggest that cardiac fibroblasts may play a critical role in mediating the hypertrophic response to ANG II in the rat heart.

Angiotensin II↗

PubMed1995

Myocardial remodeling in hypertensive Ren-2 transgenic rats.

Rats harboring the mouse Ren-2 transgene develop hypertension despite low levels of plasma renin. We determined the extent of left ventricular remodeling present in Ren-2 rats at 16 weeks of age by measuring blood pressure, ratio of heart weight to body weight, left ventricular wall thickness, passive (diastolic) left ventricular compliance, and left ventricular collagen content using hydroxyproline and collagen area fraction. Changes in perivascular fibronectin and collagen type I and III were examined with immunohistochemistry. Blood pressure values at time of death were 244 +/- 15 mm Hg for Ren-2 rats (mean +/- SD, n = 5). Ratios of heart weight to body weight (grams per kilogram) for Ren-2 animals were 4.1 +/- 0.2 versus 3.1 +/- 0.1 for controls (n = 6, P < .001). Wall thickness values for control animals were 2.6 +/- 0.1 versus 4.1 +/- 0.4 mm for Ren-2 animals (P < .001). Left ventricular Ren-2 hydroxyproline measurements were significantly decreased (3.4 +/- 0.2 versus 4.7 +/- 0.9 mg/g dry wt for controls). Significant decreases of approximately 30% were also observed in collagen area fraction in Ren-2 rats. Immunohistochemical and picrosirius red staining indicated increased amounts of perivascular fibrosis in all Ren-2 animals (when compared with controls) with enhanced levels of perivascular fibronectin and type I and type III collagen proteins. Left ventricular compliance measurements indicated a decrease in left ventricular volume for all left ventricular pressures (P = .07).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Identification of functional angiotensin II receptors on rat cardiac fibroblasts.

BACKGROUND: Cardiac hypertrophy results in an increased deposition of the extracellular matrix (ECM) proteins fibronectin and collagen. Recent evidence indicates that angiotensin II (Ang II) might have an important role in the development of myocardial fibrosis accompanying cardiac hypertrophy. We sought to determine whether fibroblasts of cardiac origin (isolated from neonatal and adult animals) express receptors for Ang II and to examine the ability of this peptide to regulate fibronectin and collagen gene expression in a cultured adult cardiac fibroblast cell preparation. METHODS AND RESULTS: Binding of 125I-Ang II to both neonatal and adult cardiac fibroblasts in culture was specific, reversible, and saturable, with the receptor evenly distributed over the cell population. Competition binding experiments with receptor-specific antagonists indicate that Ang II receptors found on both fibroblast types were of the AT1 subtype. Analysis of mRNA levels for the AT1 receptor indicates that adult cardiac fibroblasts express higher levels of the message than neonatal fibroblasts or cardiac myocytes. Addition of 10(-9) mol/L Ang II to adult cardiac fibroblasts resulted in an induction of ECM proteins above control levels, as determined through Northern blots and total collagen assays. CONCLUSIONS: Results from this study indicate that neonatal and adult rat cardiac fibroblasts in culture express AT1 receptors for Ang II. Ang II stimulation of AT1 receptors results in an increased gene expression for ECM proteins. These data suggest that Ang II might have important regulatory roles over cardiac fibroblast function under normal and pathological conditions.

Angiotensin II↗

PubMed1992

Cardiac hypertrophy-induced changes in mRNA levels for TGF-beta 1, fibronectin, and collagen.

Cardiac hypertrophy induced by pressure overload is accompanied by increases in the deposition of extracellular matrix (ECM) proteins. We wanted to determine in this study whether changes in mRNA coding for transforming growth factor (TGF)-beta 1, TGF-beta 3, and the ECM proteins, fibronectin and collagen, occur during the early phases of cardiac hypertrophy. Steady-state mRNA levels were determined in sham-operated and thoracic-banded hypertrophied rat myocardium from 6 h to 30 days after surgery. TGF-beta 1 mRNA increased significantly (1.7-fold vs. control) 12 h after aortic banding, decreasing to control levels by 14 days. No significant changes were observed for TGF-beta 3 message. Fibronectin mRNA levels increased twofold at day 1 and peaked to approximately threefold at day 3. Type I and III collagen mRNA expression was similar to control levels at day 1 but increased significantly 3 days after banding. Cardiac hypertrophy also resulted in an induction of mRNA for an embryonic isoform of fibronectin (EIIIA+) that is generated through alternative splicing of the gene. These findings indicate that, with myocardial hypertrophy, mRNAs for fibronectin are increased as early as 1 day after banding, which may allow for an initial increase in the production of fibronectin followed by the deposition of collagen. These increased mRNA levels for the ECM proteins are preceded by marked increases in TGF-beta 1 mRNAs.

Animals↗