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Biomedical subjects

Richard D Weisel

Publications and source records attributed to Richard D Weisel.

At least 73 records · Page 4Linked to original sources
PubMed2003

Transplantation of cryopreserved muscle cells in dilated cardiomyopathy: effects on left ventricular geometry and function.

OBJECTIVE: Cell transplantation to prevent congestive heart failure in patients with inherited dilated cardiomyopathy might require the use of noncardiac donor cells unaffected by the genetic defect and cryopreservation to permit cell storage until the time of transplantation. However, the effects of cryopreservation on peripheral muscle cells harvested from a cardiomyopathic recipient and their subsequent ability to restore cardiac structure and function after transplantation are unknown. METHODS: Skeletal myoblasts and vascular smooth muscle cells from cardiomyopathic hamsters (delta-sarcoglycan-deficient BIO 53.58 hamster) and age-matched normal donor hamsters were isolated, expanded in culture, and cryopreserved. After reanimation in culture, cell morphology and growth rate were assessed and compared with values seen in noncryopreserved cells. A total of 4 x 10(6) previously cryopreserved skeletal myoblasts (n = 10) and vascular smooth muscle cells (n = 10) harvested from cardiomyopathic donors were then transplanted into the left ventricles of 17-week-old BIO 53.58 hamsters. Hearts injected with culture medium alone (n = 11) served as controls. Heart function was assessed 5 weeks after transplantation on a Langendorff apparatus, and left ventricular geometry was quantified by means of computerized planimetry. Staining with 5-bromo-2'-deoxyuridine identified the injected cells. RESULTS: Vascular smooth muscle cells from cardiomyopathic donors had an abnormal morphology and diminished growth rates in culture compared with vascular smooth muscle cells from normal donors. These markers of injury were exacerbated by cryopreservation. In contrast, vascular smooth muscle cells from normal donors and skeletal myoblasts from either cardiomyopathic or normal donors appeared normal in culture and were unaffected by cryopreservation. Both cryopreserved vascular smooth muscle cells and skeletal myoblasts from cardiomyopathic donors formed a viable muscle-resembling tissue that prevented wall thinning, limited left ventricular dilatation, and preserved global systolic function in hamsters with a genetic dilated cardiomyopathy. However, attenuation of cardiac remodeling and preservation of global heart function was greater after skeletal myoblast transplantation compared with vascular smooth muscle cell transplantation in parallel to the in vitro morphologic and growth characteristics of these cells. CONCLUSIONS: Cryostorage of healthy donor cells does not prevent the benefits of cell transplantation on limiting remodeling and preserving cardiac function in the failing heart. The health of donor cells in vitro predicts their subsequent benefits on cardiac structure and function after transplantation. Cryopreservation of donor cells might facilitate a clinically applicable and effective approach for ventricular restoration with cell-transplantation therapy for patients with inherited dilated cardiomyopathy.

Analysis of Variance↗
PubMed2003

Cell transplantation to improve ventricular function in the failing heart.

Current therapies for congestive heart failure are limited in efficacy or in applicability. Cardiac cell transplantation offers a novel therapeutic approach to improve heart function. Although significant progress has been made over the past decade in the development of cell transplantation, only recently have investigators studied the changes in ventricular function following cell transplantation. This review article describes the latest research developments, evaluates recent studies of ventricular function after cell transplantation, and discusses the future directions of cell transplantation as a new therapy to 'repair broken hearts'.

Animals↗
PubMed2003

Restoration and regeneration of failing myocardium with cell transplantation and tissue engineering.

Cell transplantation and the creation of bioengineered cardiovascular tissues are novel biologic approaches to restore and regenerate failing myocardium. These rapidly evolving therapies may complement and enhance other mechanical and surgical interventions for patients with congestive heart failure, providing cardiac surgeons with a wider range of treatments for patients at risk of congestive heart failure. Proof-of-concept studies have been performed in several experimental animal models of human cardiovascular disease, such as myocardial infarction and dilated cardiomyopathy. Although the exact mechanisms are unclear, cell transplantation restores cardiac function and limits ventricular dilatation. Clinical cell transplantation has been performed in a limited number of patients with encouraging preliminary results. In contrast, bioengineered muscle grafting is largely experimental but offers the promise of myocardial regeneration by replacing irreversibly damaged myocardium with healthy autologous tissue to facilitate more extensive ventricular remodeling surgery.

Animals↗
PubMed2003

Caveolin: a key target for modulating nitric oxide availability in health and disease.

The endothelial layer is a key component of the cardiovascular system. Recent evidence indicates that strategies aimed at preserving the endothelium may have important implications in the battle against cardiovascular disease. Nitric oxide remains the critical factor determinant of endothelial function. Understanding the regulatory components involved in nitric oxide production may elucidate novel targets for improving compromised vascular function. The caveolae/caveolin system has recently become of interest due to its ability to regulate endothelial nitric oxide synthase activity. The caveolae/caveolin system is a multifaceted structure in the plasma membrane, which plays an integral role in cellular signaling. Recognizing the potential of this specialized domain may provide the fundamental knowledge to target the endothelium in disease.

Animals↗
PubMed2003

Does ischemic preconditioning afford clinically relevant cardioprotection?

This paper reviews significant work which has been done on ischemic preconditioning since its introduction by Murry et al. in 1986. This is a phenomenon where myocardial cells gain protection against long periods of ischemia by initially being exposed to brief episodes of ischemia followed by reperfusion. The molecular basis of ischemic preconditioning where adenosine, bradykinin and opioids are released, and eventually lead to the opening of mitochondrial ATP-sensitive potassium channels, is discussed in detail. There have been over 33 clinical studies to assess the clinical relevance of ischemic preconditioning. Many of these studies have looked at its benefit in patients undergoing percutaneous transluminal coronary angioplasty; others have looked at its use in open-heart surgery. There is no doubt that many of these studies support the clinical relevance of ischemic preconditioning, however, most of these studies have looked at surrogate markers, such as cardiac enzyme release, and left ventricular ejection fraction, but very few looked at the original endpoint, described by Murry et al., which is cell death. Larger trials, with morbidity and mortality being with the primary endpoints, are needed to confirm the clinical relevance of ischemic preconditioning.

Angina, Unstable↗
PubMed2003

Optimal conditions for heart cell cryopreservation for transplantation.

Cultured myocyte transplantation into an infarcted myocardium has been shown to improve contractile function. Cryopreservation of cultured muscle cells or heart tissue will be important for the technology to be practical. This study, using fetal cardiomyocytes, evaluated the optimal conditions for muscle cell cryopreservation. Study 1: Fetal rat cardiomyocytes were isolated and cultured. The freshly isolated and passage 1, 2, 3 and 4 cells were cryopreserved in a solution containing 70% IMDM, 20% FBS and 10% DMSO and stored in -196 degrees C for 1, 2, 4, 8, 12 and 24 weeks. The cells were thawed and cultured. Cell number and contractility were evaluated at 0, 2, 4, 6, 8 and 10 days of culture. Study 2: Rat myocardium was cryopreserved in sizes of 0.2, 2 and 6 mm3 for 1 week. The tissue was thawed and cells were isolated. Cell growth and contractility were evaluated. (1) Cardiomyocytes grew and contracted after cryopreservation. Storage time did not affect cell survival rate, beating cell numbers and beating rates. Increasing cell passage prior to cryopreservation decreased the percentage of beating cells. (2) Cells isolated from cryopreserved tissue grew in vitro and contracted normally. Cell yield decreased with increased cryopreserved tissue size. Fetal rat cardiomyocytes survived and functioned after in vitro cryopreservation. Viable cells can be isolated from cryopreserved myocardium and cultured. Cryopreservation of small pieces of myocardium is preferred for maximal cell yields.

Animals↗
PubMed2002

Matrix remodeling in experimental and human heart failure: a possible regulatory role for TIMP-3.

In the failing heart, an imbalance in matrix metalloproteinases (MMPs) and their biological regulators, the tissue inhibitors of MMPs (TIMPs), may result in cardiac dilatation from matrix degradation. We hypothesized that a reduction of myocardial TIMP-3 is associated with adverse matrix remodeling in both human and experimental heart failure. Cardiomyopathic hamsters at age 15 wk (normal), 25 wk (compensated stage), and 35 wk (overt failure) were compared with age-matched normal controls. MMP activity (gelatinase bioassay) was increased in cardiomyopathic hearts (P = 0.03) and peaked during the transition to overt heart failure. TIMP-3 content (immunoblot) was decreased compared with normal controls (74 +/- 5% at 25 wk, 69 +/- 10% at 35 wk; P = 0.001) and its reduction was associated with increased MMP activity (r = -0.6; P = 0.004). TIMP-1 increased progressively (P = 0.001), whereas TIMP-2, TIMP-4, and MMP protein levels were unchanged. Myocardial collagen (hydroxyproline content) increased with time during the progression to end-stage cardiac failure (P < 0.0001). Collagen synthesis ([(14)C]proline uptake) was elevated in cardiomyopathy at 15 and 25 wk (P < 0.05). The collagen cross-linking ratio (insoluble:soluble collagen) was reduced (P = 0.003) as the left ventricle dilated. By confocal microscopy restricted to viable myocardium, collagen content was reduced (P = 0.04) with fragmentation (P < 0.0001) and thinning (P = 0.003) of perimysial collagen fibers. Similarly, patients with end-stage congestive heart failure (n = 7) compared with nonfailing controls (n = 2) had elevated gelatinase MMP activity (P = 0.02) associated with isolated reductions in TIMP-3 (55 +/- 5% of normal; P = 0.003). Reductions of TIMP-3 parallel adverse matrix remodeling in the cardiomyopathic hamster and the failing human heart. TIMP-3 may contribute to the regulation of myocardial remodeling and its reduction may promote a transition from compensated to end-stage congestive heart failure.

Animals↗
PubMed2002

Mechanical stretch regimen enhances the formation of bioengineered autologous cardiac muscle grafts.

BACKGROUND: Surgical repair of congenital and acquired cardiac defects may be enhanced by the use of autologous bioengineered muscle grafts. These tissue-engineered constructs are not optimal in their formation and function. We hypothesized that a mechanical stretch regimen applied to human heart cells that were seeded on a three-dimensional gelatin scaffold (Gelfoam) would improve tissue formation and enhance graft strength. METHODS AND RESULTS: Heart cells from children undergoing repair of Tetralogy of Fallot were isolated and cultured. Heart cells were seeded on gelatin-matrix scaffolds (Gelfoam) and subjected to cyclical mechanical stress (n=7) using the Bio-Stretch Apparatus (80 cycles/minute for 14 days). Control scaffolds (n=7) were maintained under identical conditions but without cyclical stretch. Cell counting, histology, and computerized image analysis determined cell proliferation and their spatial distribution within the tissue-engineered grafts. Collagen matrix formation and organization was determined with polarized light and laser confocal microscopy. Uniaxial tensile testing assessed tissue-engineered graft function. Human heart cells proliferated within the gelatin scaffold. Remarkably, grafts that were subjected to cyclical stretch demonstrated increased cell proliferation and a marked improvement of cell distribution. Collagen matrix formation and organization was enhanced by mechanical stretch. Both maximal tensile strength and resistance to stretch were improved by cyclical mechanical stretch. CONCLUSION: The cyclical mechanical stretch regimen enhanced the formation of a three-dimensional tissue-engineered cardiac graft by improving the proliferation and distribution of seeded human heart cells and by stimulating organized matrix formation resulting in an order of magnitude increase in the mechanical strength of the graft.

Absorbable Implants↗
PubMed2002

Optimal biomaterial for creation of autologous cardiac grafts.

BACKGROUND: The optimal cardiac graft for the repair of congenital heart defects will be composed of autologous cells and will grow with the child. The biodegradable material should permit rapid cellular growth and delayed degradation with minimal inflammation. We compared a new material, epsilon-caprolactone-co-L-lactide sponge reinforced with knitted poly-L-lactide fabric (PCLA), to gelatin (GEL) and polyglycolic acid (PGA), which are previously evaluated materials. METHODS: Syngenic rat aortic smooth muscle cells (SMCs, 2x10(6)) were seeded onto GEL, PGA, and PCLA patches and cultured (n=11 per group). The DNA content in each patch was measured at 1, 2, and 3 weeks after seeding. Histological examination was performed 2 weeks after seeding. Cell-seeded patches were employed to replace a surgically created defect in the right ventricular outflow tract (RVOT) of rats (n=5 per group). Histology was studied at 8 weeks following implantation. RESULTS: In vitro studies showed that the DNA content increased significantly (P<0.05) in all patches between 1 and 3 weeks after seeding. Histology and staining SMCs for anti-alpha-smooth muscle actin (alphaSMA) revealed better growth of cells in the interstices of the grafts with GEL and PCLA than the PGA graft. In vivo studies demonstrated that seeded SMCs survived at least 8 weeks after the patch implantation in all groups. PCLA scaffolds were replaced by more cells with larger alphaSMA-positive areas and by more extracellular matrix with larger elastin-positive areas than with GEL and PGA. The patch did not thin and expanded significantly. The GEL and PGA patches thinned and expanded. All grafts had complete endothelialization on the endocardial surface. CONCLUSIONS: SMC-seeded biodegradable materials can be employed to repair the RVOT. The novel PCLA patches permitted better cellular penetration in vitro and did not thin or dilate in vivo and did not produce an inflammatory response. The cell-seeded PCLA patch may permit the construction of an autologous patch to repair congenital heart defects.

Absorbable Implants↗
PubMed2002

Combined procedure of surgical repair and cell transplantation for left ventricular aneurysm: an experimental study.

BACKGROUND: This study was designed to investigate the efficacy of the combined procedure of left ventricular (LV) repair and fetal cardiomyocyte transplantation (CM-TX) in a rat myocardial infarction model. METHODS AND RESULTS: A moderate-sized LV aneurysm was created by proximal ligation of the left coronary artery in 47 Lewis rats. Four weeks later, they were underwent another operation and received culture medium injection (n=10; group I), fetal CM-TX (n=10; group II), purse-string LV repair with culture medium injection (n=14; group III), or LV repair with fetal CM-TX (n=13; group IV). They were echocardiographically followed-up during the subsequent 4 weeks, and cardiac catheterization was performed in the final week. In the late period, LV dimension in group IV was smaller than that in group III (end-diastolic dimension, 0.92+/-0.02 versus 1.01+/-0.03 cm, P=0.0090; end-systolic dimension, 0.62+/-0.02 versus 0.74+/-0.04 cm, P=0.0093; at the fourth week), although they initially showed similar decreases in both groups. At the final week, end-systolic elastance was higher in group IV than in groups I, II, or III (0.61+/-0.10 versus 0.19+/-0.03, 0.30+/-0.09, 0.33+/-0.07 mm Hg/ micro L, P=0.0002, 0.0037, and 0.0042, respectively). CONCLUSIONS: Fetal CM-TX exerted preventive effects against late LV dilation and dysfunction after LV repair in the rat model. The results suggest that repair surgery combined with fetal CM-TX may enhance the surgical benefits for patients with LV aneurysm in the long term.

Animals↗
PubMed2002

A self-fulfilling prophecy: C-reactive protein attenuates nitric oxide production and inhibits angiogenesis.

BACKGROUND: Given the central importance of nitric oxide (NO) in the development and clinical course of cardiovascular diseases, we sought to determine whether the powerful predictive value of C-reactive protein (CRP) might be explained through an effect on NO production. METHODS AND RESULTS: Endothelial cells (ECs) were incubated with recombinant CRP (0 to 100 microg/mL, 24 hours), and NO and cyclic guanosine monophosphate (cGMP) production was assessed. The effects of CRP on endothelial NO synthase (eNOS) protein, mRNA expression, and mRNA stability were also examined. In a separate study, the effects of CRP (25 microg/mL) on EC cell survival, apoptosis, and in vitro angiogenesis were evaluated. Incubation of ECs with CRP resulted in a significant inhibition of basal and stimulated NO release, with concomitant reductions in cGMP production. CRP caused a marked downregulation of eNOS mRNA and protein expression. Actinomycin D studies suggested that eNOS downregulation was related to decreased mRNA stability. In conjunction with a decrease in NO production, CRP inhibited both basal and vascular endothelial growth factor-stimulated angiogenesis as assessed by EC migration and capillary-like tube formation. CRP did not induce EC survival but did, however, promote apoptosis in a NO-dependent fashion. CONCLUSIONS: CRP, at concentrations known to predict adverse vascular events, directly quenches the production of the NO, in part, through posttranscriptional effect on eNOS mRNA stability. Diminished NO bioactivity, in turn, inhibits angiogenesis, an important compensatory mechanism in chronic ischemia. Through decreasing NO synthesis, CRP may facilitate the development of diverse cardiovascular diseases. Risk reduction strategies designed to lower plasma CRP may be effective by improving NO bioavailability.

Apoptosis↗
PubMed2002

Endothelin antagonism and interleukin-6 inhibition attenuate the proatherogenic effects of C-reactive protein.

BACKGROUND: C-reactive protein (CRP) has been suggested to actively participate in the development of atherosclerosis. In the present study, we examined the role of the potent endothelium-derived vasoactive factor endothelin-1 (ET-1) and the inflammatory cytokine interleukin-6 (IL-6) as mediators of CRP-induced proatherogenic processes. METHODS AND RESULTS: Saphenous vein endothelial cells (HSVECs) were incubated with human recombinant CRP (25 microg/mL, 24 hours) and the expression of vascular cell adhesion molecule (VCAM-1), intracellular adhesion molecule (ICAM-1), and monocyte chemoattractant chemokine-1 was determined. The effects of CRP on LDL uptake were assessed in macrophages using immunofluorescent labeling of CD32 and CD14. In each study, the effect of endothelin antagonism (bosentan) and IL-6 inhibition (monoclonal anti-IL-6 antibodies) was examined. The effects of CRP on the secretion of ET-1 and IL-6 from HSVECs were also evaluated. Incubation of HSVECs with recombinant human CRP resulted in a marked increase in ICAM-1 and VCAM-1 expression (P<0.001). Likewise, CRP caused a significant increase in monocyte chemoattractant chemokine-1 production, a key mediator of leukocyte transmigration (P<0.001). CRP caused a marked and sustained increase in native LDL uptake by macrophages (P<0.05). These proatherosclerotic effects of CRP were mediated, in part, via increased secretion of ET-1 and IL-6 (P<0.01) and were attenuated by both bosentan and IL-6 antagonism (P<0.01). CONCLUSIONS: CRP actively promotes a proatherosclerotic and proinflammatory phenotype. These effects are mediated, in part, via the production of ET-1 and IL-6 and are attenuated by mixed ET(A/B) receptor antagonism and IL-6 inhibition. Bosentan may be useful in decreasing CRP-mediated vascular disease.

Antibodies↗
PubMed2002

Cell transplantation in non-ischemic dilated cardiomyopathy. A novel biological approach for ventricular restoration.

OBJECTIVE: With a rising incidence, dilated cardiomyopathy (DCM) is regarded as a major health care concern. Although both medical therapy and novel surgical treatments have been applied to treat DCM, the effects of preventing left ventricular (LV) dilatation are limited, and the mortality rate associated with the disease remains high. Thus novel management strategies for improved treatment of DCM are awaited. METHODS: Researchers have found that, in models of regional ventricular dysfunction, transplanted cells induced a profound biological phenomenon that restored contractile function and prevented ventricular dilatation. We have investigated muscle cell transplantation in hamsters with DCM, and have found that heart cells and smooth muscle cells survived in the host myocardium after transplantation, which suppressed LV dilatation and wall thinning, and preserved heart function. Our current studies are focusing on the clinical applicability of these encouraging early findings by evaluating the optimal cell types, the timing of transplantation, and cryopreservation as cell storage. Concurrently, we are investigating the influence of cell transplantation on myocardial remodeling in order to outline the mechanism of benefit afforded by donor cell engraftment. We believe that the timing of cell transplantation with respect to the progression of the underlying disease is critical in preventing ventricular thinning, dilation and preserving cardiac function. CONCLUSIONS: This novel approach can be a clinically applicable biological therapy for patients with progressive DCM. More studies to uncover the specific molecular and cellular effects of cell transplantation on the host myocardium are necessary for future clinical application.

Animals↗
PubMed2002

The characterization and purification of a human transcription factor modulating the glutathione peroxidase gene in response to oxygen tension.

An oxygen responsive transcription factor regulating human glutathione peroxidase gene (GPx) through two oxygen responsive elements (ORE I and ORE2) has been purified and characterized by sequence-specific DNA affinity chromatography. The DNA binding activity, termed Oxygen Responsive Element Binding Protein (OREBP), was partially represented by a 77 kD polypeptide (p70) possessing a blocked N-terminus. The p70 subunit co-eluted with an 86 kD subunit (p80) from affinity columns. N-terminal sequencing analysis of the 86 kD component revealed that this protein represented the larger member of the Ku antigen complex. The identity of the purified 77 kD subunit was determined by Western blot analysis using an antibody directed against the p70 protein. In addition to binding the GPx-ORE, the OREBP was itself regulated by oxygen tension. It was found that the abundance of the ORE binding activity was decreased in cells maintained at low oxygen tension (40 mm Hg). Anti-Ku-antibodies specifically supershifted the OREBP-ORE DNA complex. These observations further add to the numerous nuclear roles of the Ku-transcription factor.

Antibodies↗
PubMed2002

Regional overexpression of insulin-like growth factor-I and transforming growth factor-beta1 in the myocardium of patients with hypertrophic obstructive cardiomyopathy.

OBJECTIVE: Hypertrophic obstructive cardiomyopathy has been proposed to be the result of gene mutations of contractile proteins. However, we have previously shown significant elevation of insulin-like growth factor-I (IGF-I) and transforming growth factor-beta1 (TGF-beta1) at the messenger RNA, protein, and receptor levels in patients with hypertrophic obstructive cardiomyopathy when compared with myocardium from patients without this disorder. We hypothesized that this growth factor overexpression is a regional phenomenon. To test this hypothesis, we compared levels of IGF-I and TGF-beta1 in hypertrophic and nonhypertrophic myocardium within the same group of patients with hypertrophic obstructive cardiomyopathy. METHODS: Two biopsy specimens were obtained from each patient undergoing septal myectomy for severely symptomatic hypertrophic obstructive cardiomyopathy, from hypertrophied septum and from nonhypertrophied myocardium (8 patients in total). Clinical data were prospectively recorded. Messenger RNA levels for growth factor were quantified by means of multiplex reverse transcriptase-polymerase chain reaction, expressed as a densitometric ratio of growth factor/glyceraldehyde-3-phosphate dehydrogenase. Protein levels were quantified by means of chemiluminescent slot blot analysis. Growth factor proteins were used to generate a standard curve. RESULTS: IGF-I messenger RNA and protein levels in hypertrophic myocardium were 2.6 and 2.9 times greater, respectively, than in nonhypertrophic myocardium of the same patients (both P <.01). TGF-beta 1 messenger RNA and protein levels in the hypertrophic myocardium were 2.5 and 2.8 times greater, respectively, than the levels in the nonhypertrophied myocardium (both P <.01). There was a significant correlation between the IGF-I protein ratio (hypertrophic/nonhypertrophic myocardium) and the inducible left ventricular outflow tract gradients measured at cardiac catheterization (r = 0.77, P =.025). CONCLUSIONS: Myocardial overexpression of IGF-I and TGF-beta1 is a regional phenomenon in patients with hypertrophic obstructive cardiomyopathy and is likely involved in the pathogenesis of the disorder.

Cardiomyopathy, Hypertrophic↗