Jeffrey Lin

Estrogen Receptor-β Activation Results in S-Nitrosylation of Proteins Involved in Cardioprotection

Background— It has been shown that the activation of estrogen receptor-&bgr; (ER-&bgr;) plays an important cardioprotective role against ischemia/reperfusion injury. However, the mechanism for this protection is not clear. We hypothesize that estrogen protects by ER-&bgr; activation, which leads to S-nitrosylation (SNO) of key cardioprotective proteins. Methods and Results— We treated ovariectomized C57BL/6J mice with the ER-&bgr; selective agonist 2,2-bis(4-hydroxyphenyl)-proprionitrile (DPN), 17&bgr;-estradiol (E2), or vehicle using Alzet minipumps for 2 weeks. Isolated hearts were Langendorff perfused and subjected to ischemia and reperfusion. Compared with vehicle-treated hearts, DPN- and E2-treated hearts had significantly better postischemic functional recovery and decreased infarct size. To test the specificity of DPN, we treated ER-&bgr;–knockout mice with DPN. However, no cardioprotective effect of DPN was found in ER-&bgr;–knockout mice, indicating that the DPN-induced cardioprotection occurs through the activation of ER-&bgr;. Using DyLight-maleimide fluors and a modified biotin switch method, we used a 2-dimensional DyLight fluorescence difference gel electrophoresis proteomic method to quantify differences in SNO of proteins. DPN- and E2-treated hearts showed an increase in SNO of a number of proteins. Interestingly, many of these proteins also had been shown to have increased SNO in preconditioned hearts. In addition, the DPN-induced cardioprotection and increased SNO were abolished by treatment with a nitric oxide synthase inhibitor. Conclusion— The activation of ER-&bgr; by DPN treatment leads to increased protein SNO and cardioprotection against ischemia/reperfusion injury, suggesting that long-term estrogen exposure protects hearts largely via activation of ER-&bgr; and nitric oxide/SNO signaling.

Controlled delivery of platelet-rich plasma-derived growth factors for bone formation

Platelet-rich plasma (PRP) represents an autologous source of growth factors essential for bone regeneration. The clinical efficacy of PRP is, however, unpredictable, and this is likely due to the inefficient and inconsistent delivery of PRP-derived growth factors. Previous investigations have shown that current methods of PRP preparation result in a premature release of the relevant bone stimulatory factors. As successful bone regeneration requires multiple factors presented in a physiologic temporal and spatial cascade, the objective of this study is to control the bioavailability of PRP-derived growth factors using a hydrogel carrier system. Specifically, the release of platelet-derived growth factor, transforming growth factor beta-1, and insulin-like growth factor from two types of alginate carriers was compared over time. The effects of the released factors on the growth and alkaline phosphatase (ALP) activity of human osteoblast-like cells were also evaluated. It was found that factor release profiles varied as function of carrier type, and binding of growth factors to the alginate matrix also modulated their release. The bioactivity of released factors was maintained in vitro and they promoted cell proliferation and ALP activity. These results demonstrate the potential of this autologous multifactor delivery system for controlling the bioavailability of PRP-derived factors. Future studies will focus on optimizing this system to increase the clinical efficacy of PRP by matching the distribution and temporal sequencing of PRP-derived factors to the bone healing cascade.

Inflammatory activation: cardiac, renal, and cardio-renal interactions in patients with the cardiorenal syndrome

Although inflammation is a physiologic response designed to protect us from infection, when unchecked and ongoing it may cause substantial harm. Both chronic heart failure (CHF) and chronic kidney disease (CKD) are known to cause elaboration of several pro-inflammatory mediators that can be detected at high concentrations in the tissues and blood stream. The biologic sources driving this chronic inflammatory state in CHF and CKD are not fully established. Traditional sources of inflammation include the heart and the kidneys which produce a wide range of pro-inflammatory cytokines in response to neurohormones and sympathetic activation. However, growing evidence suggests that non-traditional biomechanical mechanisms such as venous and tissue congestion due to volume overload are also important as they stimulate endotoxin absorption from the bowel and peripheral synthesis and release of pro-inflammatory mediators. Both during the chronic phase and, more rapidly, during acute exacerbations of CHF and CKD, inflammation and congestion appear to amplify each other resulting in a downward spiral of worsening cardiac, vascular, and renal functions that may negatively impact patients’ outcome. Anti-inflammatory treatment strategies aimed at attenuating end organ damage and improving clinical prognosis in the cardiorenal syndrome have been disappointing to date. A new therapeutic paradigm may be needed, which involves different anti-inflammatory strategies for individual etiologies and stages of CHF and CKD. It may also include specific (short-term) anti-inflammatory treatments that counteract inflammation during the unsettled phases of clinical decompensation. Finally, it will require greater focus on volume overload as an increasingly significant source of systemic inflammation in the cardiorenal syndrome.

Controlled release of PRP-derived growth factors promotes osteogenic differentiation of human mesenchymal stem cells.

Platelet-rich plasma (PRP) has been gaining increasing popularity in orthopedics and oral and maxillofacial surgery because of its potential efficacy in enhancing bone regeneration. To maximally augment bone healing using PRP and to control the bioavailability of the relevant growth factors, we have designed an alginate hydrogel-based PRP-delivery system. The bioactivity of the growth factors released from PRP carriers was evaluated by determining the ability of these factors to induce osteogenic differentiation of human mesenchymal stem cells (hMSCs). Specifically, monolayers of hMSCs were incubated with the PRP-containing hydrogel carriers over a two-week culture period. Osteoblast-like cells treated with the hydrogel carriers served as controls. The growth and osteogenic differentiation (alkaline phosphatase activity and mineralization) of hMSCs was determined. The results showed that PRP-derived growth factors released from hydrogel carriers stimulated the osteogenic differentiation of hMSCs and most significantly, the cellular response was carrier type-dependent. Future studies will focus on in vitro and in vivo testing of the efficacy of hydrogel-based PRP release systems

Exercise-Induced Left Ventricular Remodeling Among Competitive Athletes A Phasic Phenomenon

Background—Contemporary understanding of exercise-induced cardiac remodeling is based on cross-sectional data and relatively short duration longitudinal studies. Temporal progression of exercise-induced cardiac remodeling remains incompletely understood. Methods and Results—A longitudinal repeated-measures study design using 2-dimensional and speckle-tracking echocardiography was used to examine acute augmentation phase (AAP; 90 days) and more extended chronic maintenance phase (39 months) left ventricular (LV) structural and functional adaptations to endurance exercise training among competitive male rowers (n=12; age 18.6±0.5 years). LV mass was within normal limits at baseline (93±9 g/m2), increased after AAP (105±7 g/m2; P=0.001), and further increased after chronic maintenance phase (113±10 g/m2; P<0.001 for comparison to post-AAP). AAP LV hypertrophy was driven by LV dilation (&Dgr;LV end-diastolic volume, 9±3 mL/m2; P=0.004) with stable LV wall thickness (&Dgr;LV wall thickness, 0.3±0.1 mm; P=0.63). In contrast, chronic maintenance phase LV hypertrophy was attributable to LV wall thickening (&Dgr; LV wall thickness, 1.1±0.4 mm; P=0.004) with stable LV chamber volumes (&Dgr;LV end-diastolic volume, 1±1 mL/m2; P=0.48). Early diastolic peak tissue velocity increased during AAP (−11.7±1.9 versus −13.6±1.3 cm/s; P<0.001) and remained similarly increased after chronic maintenance phase. Conclusions—In a small sample of competitive endurance athletes, exercise-induced cardiac remodeling follows a phasic response with increases in LV chamber size, early diastolic function, and systolic twist in an acute augmentation phase of exercise training. This is followed by a chronic phase of adaptation characterized by increasing wall thickness and regression in LV twist. Training duration is a determinant of exercise-induced cardiac remodeling and has implications for the assessment of myocardial structure and function in athletes.

Peripheral venous congestion causes time‐ and dose‐dependent release of endothelin‐1 in humans

Endothelin‐1 (ET‐1) is a pivotal mediator of vasoconstriction and inflammation in congestive states such as heart failure (HF) and chronic kidney disease (CKD). Whether peripheral venous congestion (VC) increases plasma ET‐1 at pressures commonly seen in HF and CKD patients is unknown. We seek to characterize whether peripheral VC promotes time‐ and dose‐dependent increases in plasma ET‐1 and whether these changes are sustained after decongestion. We used a randomized, cross‐over design in 20 healthy subjects (age 30 ± 7 years). To experimentally model VC, venous pressure was increased to either 15 or 30 mmHg (randomized at first visit) above baseline by inflating a cuff around the subjects dominant arm; the nondominant arm served as a noncongested control. We measured plasma ET‐1 at baseline, after 20, 60 and 120 min of VC, and finally at 180 min (60 min after cuff release and decongestion). Plasma ET‐1 progressively and significantly increased over 120 min in the congested arm relative to the control arm and to baseline values. This effect was dose‐dependent: ET‐1 increased by 45% and 100% at VC doses of 15 and 30 mmHg, respectively (P < 0.05), and declined after 60 min of decongestion though remaining significantly elevated compared to baseline. In summary, peripheral VC causes time‐ and dose‐dependent increases in plasma ET‐1. Of note, the lower dose of 15 mmHg (more clinically relevant to HF and CKD patients) was sufficient to raise ET‐1. These findings support the potentially contributory, not merely consequential, role of VC in the pathophysiology of HF and CKD.

Exercise-Induced Left Ventricular Remodeling Among Competitive AthletesCLINICAL PERSPECTIVE

Background—Contemporary understanding of exercise-induced cardiac remodeling is based on cross-sectional data and relatively short duration longitudinal studies. Temporal progression of exercise-induced cardiac remodeling remains incompletely understood. Methods and Results—A longitudinal repeated-measures study design using 2-dimensional and speckle-tracking echocardiography was used to examine acute augmentation phase (AAP; 90 days) and more extended chronic maintenance phase (39 months) left ventricular (LV) structural and functional adaptations to endurance exercise training among competitive male rowers (n=12; age 18.6±0.5 years). LV mass was within normal limits at baseline (93±9 g/m2), increased after AAP (105±7 g/m2; P=0.001), and further increased after chronic maintenance phase (113±10 g/m2; P<0.001 for comparison to post-AAP). AAP LV hypertrophy was driven by LV dilation (&Dgr;LV end-diastolic volume, 9±3 mL/m2; P=0.004) with stable LV wall thickness (&Dgr;LV wall thickness, 0.3±0.1 mm; P=0.63). In contrast, chronic maintenance phase LV hypertrophy was attributable to LV wall thickening (&Dgr; LV wall thickness, 1.1±0.4 mm; P=0.004) with stable LV chamber volumes (&Dgr;LV end-diastolic volume, 1±1 mL/m2; P=0.48). Early diastolic peak tissue velocity increased during AAP (−11.7±1.9 versus −13.6±1.3 cm/s; P<0.001) and remained similarly increased after chronic maintenance phase. Conclusions—In a small sample of competitive endurance athletes, exercise-induced cardiac remodeling follows a phasic response with increases in LV chamber size, early diastolic function, and systolic twist in an acute augmentation phase of exercise training. This is followed by a chronic phase of adaptation characterized by increasing wall thickness and regression in LV twist. Training duration is a determinant of exercise-induced cardiac remodeling and has implications for the assessment of myocardial structure and function in athletes.

Exercise-Induced Left Ventricular Remodeling Among Competitive AthletesCLINICAL PERSPECTIVE: A Phasic Phenomenon

Background—Contemporary understanding of exercise-induced cardiac remodeling is based on cross-sectional data and relatively short duration longitudinal studies. Temporal progression of exercise-induced cardiac remodeling remains incompletely understood. Methods and Results—A longitudinal repeated-measures study design using 2-dimensional and speckle-tracking echocardiography was used to examine acute augmentation phase (AAP; 90 days) and more extended chronic maintenance phase (39 months) left ventricular (LV) structural and functional adaptations to endurance exercise training among competitive male rowers (n=12; age 18.6±0.5 years). LV mass was within normal limits at baseline (93±9 g/m2), increased after AAP (105±7 g/m2; P=0.001), and further increased after chronic maintenance phase (113±10 g/m2; P<0.001 for comparison to post-AAP). AAP LV hypertrophy was driven by LV dilation (&Dgr;LV end-diastolic volume, 9±3 mL/m2; P=0.004) with stable LV wall thickness (&Dgr;LV wall thickness, 0.3±0.1 mm; P=0.63). In contrast, chronic maintenance phase LV hypertrophy was attributable to LV wall thickening (&Dgr; LV wall thickness, 1.1±0.4 mm; P=0.004) with stable LV chamber volumes (&Dgr;LV end-diastolic volume, 1±1 mL/m2; P=0.48). Early diastolic peak tissue velocity increased during AAP (−11.7±1.9 versus −13.6±1.3 cm/s; P<0.001) and remained similarly increased after chronic maintenance phase. Conclusions—In a small sample of competitive endurance athletes, exercise-induced cardiac remodeling follows a phasic response with increases in LV chamber size, early diastolic function, and systolic twist in an acute augmentation phase of exercise training. This is followed by a chronic phase of adaptation characterized by increasing wall thickness and regression in LV twist. Training duration is a determinant of exercise-induced cardiac remodeling and has implications for the assessment of myocardial structure and function in athletes.