The impact of right ventricular pressure and function on survival in patients with pulmonary vein stenosis.

Pulmonary vein stenosis (PVS) is associated with pulmonary hypertension (PH), but there is little information regarding the impact of PH on right ventricular (RV) systolic function and survival. We conducted a retrospective cohort study of our patients to explore this and other aspects of pulmonary hemodynamics with PVS. RV function was assessed using qualitative two-dimensional echocardiography. The ratio of systolic pulmonary artery (PA) and aortic pressures (PA:Ao) at cardiac catheterization reflected pulmonary hemodynamics. Reactivity testing employed inhaled nitric oxide + 100% fiO2, or 100% fiO2 only; "reactivity" was a ≥ 20% decrease in PA:Ao. There were 105 PVS patients, although not all had data at every time point. (1) The mean PA:Ao at first cardiac catheterization (n = 77) was 0.79 ± 0.36; at last catheterization (n = 54), PA:Ao = 0.69 ± 0.30; 90% had systolic PAP > one-half systemic. Survival was shorter with PA:Ao > 0.5. (2) Differences in survival relative to RV dysfunction on the first echocardiogram were not significant, although they were using the last echocardiogram. (3) The magnitude of RV dysfunction was positively correlated with PA:Ao. (4) Balloon dilation of PV acutely decreased PA:Ao (-0.13 ± 0.37, P = 0.03 [n = 40 patients]). 5. Of 20 patients tested, 13 were acutely reactive to vasodilators. PH is a major feature of PVS. Reduced RV function and PA:Ao appear to be predictors of survival. Given the importance of PH in this disease, clinical studies of PVS treatments should include measures of PAP and RV function as important variables of interest.

Pseudoaneurysm complicating right ventricle-to-pulmonary artery conduit surgery: Incidence and risk factors.

OBJECTIVES: Although pseudoaneurysm is an uncommon complication after right ventricle-to-pulmonary artery conduit placement, it has the potential to cause significant morbidity and mortality. METHODS: We performed a review of patients with pseudoaneurysms diagnosed at our institution in a 20-year period (from 1995 through 2015) and compared their clinical characteristics with a group of age- and sex-matched control patients. RESULTS: We found that younger age, smaller size, the diagnosis of tetralogy of Fallot, the use of a pulmonary homograft conduit, the presence of an unrestrictive ventricular septal defect after conduit placement, and having at least systemic right ventricular pressure were all more common in patients who had pseudoaneurysms develop. CONCLUSIONS: This study is unique in identifying both patient and surgical factors that may predispose to pseudoaneurysm development and can help inform optimal strategies to monitor and evaluate this patient population.

Low magnitude and high frequency mechanical loading prevents decreased bone formation responses of 2T3 preosteoblasts.

Bone loss due to osteoporosis or disuse such as in paraplegia or microgravity is a significant health problem. As a treatment for osteoporosis, brief exposure of intact animals or humans to low magnitude and high frequency (LMHF) mechanical loading has been shown to normalize and prevent bone loss. However, the underlying molecular changes and the target cells by which LMHF mechanical loading alleviate bone loss are not known. Here, we hypothesized that direct application of LMHF mechanical loading to osteoblasts alters their cell responses, preventing decreased bone formation induced by disuse or microgravity conditions. To test our hypothesis, preosteoblast 2T3 cells were exposed to a disuse condition using the random positioning machine (RPM) and intervened with an LMHF mechanical load (0.1-0.4 g at 30 Hz for 10-60 min/day). Exposure of 2T3 cells to the RPM decreased bone formation responses as determined by alkaline phosphatase (ALP) activity and mineralization even in the presence of a submaximal dose of BMP4 (20 ng/ml). However, LMHF mechanical loading prevented the RPM-induced decrease in ALP activity and mineralization. Mineralization induced by LMHF mechanical loading was enhanced by treatment with bone morphogenic protein 4 (BMP4) and blocked by the BMP antagonist noggin, suggesting a role for BMPs in this response. In addition, LMHF mechanical loading rescued the RPM-induced decrease in gene expression of ALP, runx2, osteomodulin, parathyroid hormone receptor 1, and osteoglycin. These findings suggest that preosteoblasts may directly respond to LMHF mechanical loading to induce differentiation responses. The mechanosensitive genes identified here provide potential targets for pharmaceutical treatments that may be used in combination with low level mechanical loading to better treat osteoporosis or disuse-induced bone loss.

Identification of mechanosensitive genes in osteoblasts by comparative microarray studies using the rotating wall vessel and the random positioning machine.

Weightlessness or microgravity of spaceflight induces bone loss due in part to decreased bone formation by unknown mechanisms. Due to difficulty in performing experiments in space, several ground-based simulators such as the Rotating Wall Vessel (RWV) and Random Positioning Machine (RPM) have become critical venues to continue studying space biology. However, these simulators have not been systematically compared to each other or to mechanical stimulating models. Here, we hypothesized that exposure to RWV inhibits differentiation and alters gene expression profiles of 2T3 cells, and a subset of these mechanosensitive genes behaves in a manner consistent to the RPM and opposite to the trends incurred by mechanical stimulation of mouse tibiae. Exposure of 2T3 preosteoblast cells to the RWV for 3 days inhibited alkaline phosphatase activity, a marker of differentiation, and downregulated 61 and upregulated 45 genes by more than twofold compared to static 1 g controls, as shown by microarray analysis. The microarray results were confirmed by real-time PCR and/or Western blots for seven separate genes and proteins including osteomodulin, runx2, and osteoglycin. Comparison of the RWV data to the RPM microarray study that we previously published showed 14 mechanosensitive genes that changed in the same direction. Further comparison of the RWV and RPM results to microarray data from mechanically loaded mouse tibiae reported by an independent group revealed that three genes including osteoglycin were upregulated by the loading and downregulated by our simulators. These mechanosensitive genes may provide novel insights into understanding the mechanisms regulating bone formation and potential targets for countermeasures against decreased bone formation during space flight and in pathologies associated with lack of bone formation.

Simulated microgravity using the Random Positioning Machine inhibits differentiation and alters gene expression profiles of 2T3 preosteoblasts.

Exposure to microgravity causes bone loss in humans, and the underlying mechanism is thought to be at least partially due to a decrease in bone formation by osteoblasts. In the present study, we examined the hypothesis that microgravity changes osteoblast gene expression profiles, resulting in bone loss. For this study, we developed an in vitro system that simulates microgravity using the Random Positioning Machine (RPM) to study the effects of microgravity on 2T3 preosteoblast cells grown in gas-permeable culture disks. Exposure of 2T3 cells to simulated microgravity using the RPM for up to 9 days significantly inhibited alkaline phosphatase activity, recapitulating a bone loss response that occurs in real microgravity conditions without altering cell proliferation and shape. Next, we performed DNA microarray analysis to determine the gene expression profile of 2T3 cells exposed to 3 days of simulated microgravity. Among 10,000 genes examined using the microarray, 88 were downregulated and 52 were upregulated significantly more than twofold using simulated microgravity compared with the static 1-g condition. We then verified the microarray data for some of the genes relevant in bone biology using real-time PCR assays and immunoblotting. We confirmed that microgravity downregulated levels of alkaline phosphatase, runt-related transcription factor 2, osteomodulin, and parathyroid hormone receptor 1 mRNA; upregulated cathepsin K mRNA; and did not significantly affect bone morphogenic protein 4 and cystatin C protein levels. The identification of gravisensitive genes provides useful insight that may lead to further hypotheses regarding their roles in not only microgravity-induced bone loss but also the general patient population with similar pathological conditions, such as osteoporosis.