Twist1 Inactivation in Dmp1-Expressing Cells Increases Bone Mass but Does Not Affect the Anabolic Response to Sclerostin Neutralization.

Wnt signaling plays a major role in bone metabolism. Advances in our understanding of secreted regulators of Wnt have yielded several therapeutic targets to stimulate osteoanabolism-the most promising of which is the Wnt inhibitor sclerostin. Sclerostin antibody recently gained approval for clinical use to treat osteoporosis, but the biology surrounding sclerostin antagonism is still incompletely understood. Numerous factors regulate the efficacy of sclerostin inhibition on bone formation, a process known as self-regulation. In previous communications we reported that the basic helix-loop-helix transcription factor Twist1-a gene know to regulate skeletal development-is highly upregulated among the osteocyte cell population in mice treated with sclerostin antibody. In this communication, we tested the hypothesis that preventing Twist1 upregulation by deletion of Twist1 from late-stage osteoblasts and osteocytes would increase the efficacy of sclerostin antibody treatment, since Twist1 is known to restrain osteoblast activity in many models. Twist1-floxed loss-of-function mice were crossed to the Dmp1-Cre driver to delete Twist1 in Dmp1-expressing cells. Conditional Twist1 deletion was associated with a mild but significant increase in bone mass, as assessed by dual energy x-ray absorptiometry (DXA) and microCT (µCT) for many endpoints in both male and female mice. Biomechanical properties of the femur were not affected by conditional mutation of Twist1. Sclerostin antibody improved all bone properties significantly, regardless of Twist1 status, sex, or endpoint examined. No interactions were detected when Twist1 status and antibody treatment were examined together, suggesting that Twist1 upregulation in the osteocyte population is not an endogenous mechanism that restrains the osteoanabolic effect of sclerostin antibody treatment. In summary, Twist1 inhibition in the late-stage osteoblast/osteocyte increases bone mass but does not affect the anabolic response to sclerostin neutralization.

Low-dose nitric oxide therapy for persistent pulmonary hypertension of the newborn. Clinical Inhaled Nitric Oxide Research Group.

BACKGROUND: Inhaled nitric oxide improves gas exchange in neonates, but the efficacy of low-dose inhaled nitric oxide in reducing the need for extracorporeal membrane oxygenation has not been established. METHODS: We conducted a clinical trial to determine whether low-dose inhaled nitric oxide would reduce the use of extracorporeal membrane oxygenation in neonates with pulmonary hypertension who were born after 34 weeks' gestation, were 4 days old or younger, required assisted ventilation, and had hypoxemic respiratory failure as defined by an oxygenation index of 25 or higher. The neonates who received nitric oxide were treated with 20 ppm for a maximum of 24 hours, followed by 5 ppm for no more than 96 hours. The primary end point of the study was the use of extracorporeal membrane oxygenation. RESULTS: Of 248 neonates enrolled, 126 were randomly assigned to the nitric oxide group and 122 to the control group. Extracorporeal membrane oxygenation was used in 78 neonates in the control group (64 percent) and in 48 neonates in the nitric oxide group (38 percent) (P=0.001). The 30-day mortality rate in the two groups was similar (8 percent in the control group and 7 percent in the nitric oxide group). Chronic lung disease developed less often in neonates treated with nitric oxide than in those in the control group (7 percent vs. 20 percent, P=0.02). The efficacy of nitric oxide was independent of the base-line oxygenation index and the primary pulmonary diagnosis. CONCLUSIONS: Inhaled nitric oxide reduces the extent to which extracorporeal membrane oxygenation is needed in neonates with hypoxemic respiratory failure and pulmonary hypertension.

The changing demographics of neonatal extracorporeal membrane oxygenation patients reported to the Extracorporeal Life Support Organization (ELSO) Registry.

BACKGROUND: Extracorporeal membrane oxygenation (ECMO) is an important treatment tool in the management of near-term and term neonates with severe hypoxemic respiratory failure. To better understand how health care for patients treated with ECMO has changed, we studied the demographic and treatment data reported to the Extracorporeal Life Support Organization (ELSO) registry from January 1, 1988, through January 1, 1998. METHODS: We used data stored in the ELSO registry and evaluated the changes in demographics, use of alternate therapies before ECMO, severity of illness, duration of ECMO therapy, and mortality over a 10-year period. All data on neonates reported between January 1, 1988, and January 1, 1998 were used. Verification checks were performed on all fields to eliminate nonsense outliers. We separated the neonates into 2 groups-those with and those without a congenital diaphragmatic hernia (CDH). All analyses were performed on the total group and each subgroup separately. Changes in continuous data were analyzed by year using analysis of variance. Year differences in categorical data were evaluated with chi(2) analysis. We also used the linear trend test and the Cochran-Armitage trend test to evaluate time-related changes. RESULTS: We reviewed 12 175 neonates. Over the decade, there were no changes in mean gestational age, gender, age at which ECMO was started, pH, or PaCO(2) just before ECMO. The proportion of neonates with CDH increased from 18% to 26%, while the proportion with respiratory distress syndrome decreased from 15% to 4%. Other diagnostic categories remained constant. The use of surfactant, high-frequency ventilation, and inhaled nitric oxide increased from 0% in 1988 to 36%, 46%, and 24%, respectively, in 1997. The mean peak pressure being used just before ECMO decreased (47 +/- 10 in 1988 to 39 +/- 12 in 1997), and the mean PaO(2)/FIO(2) ratio increased (38 +/- 23 in 1988 to 48 +/- 36 in 1997). The primary mode of ECMO remains venoarterial; however, the use of venovenous ECMO increased from 1% to 32% over the decade. Duration of ECMO treatment increased overall, and this trend was seen for patients with and without CDH (124 +/- 67 to 141 +/- 104 hours for the non-CDH group, 161 +/- 99 to 238 +/- 141 hours for the CDH group). The number of centers reporting neonatal data to the ELSO registry increased from 52 in 1988 to a peak of 100 in 1993. In 1997, 96 centers reported data to ELSO. The average number of neonatal patients reported from each site decreased from a peak of 18 in 1991 to 9 in 1997. Mortality increased from 18% to 22%; however, when corrected for the relative increase in neonates with CDH, this trend disappeared. Diagnoses-specific mortality rates remained constant. The occurrence of intracranial hemorrhage and/or infarct also stayed constant at 16%. CONCLUSIONS: The population of neonates treated with ECMO in 1997 was very different from patients treated in the 1980s and early 1990s. They were exposed to an ever-expanding group of new therapies, appeared to be healthier based on indices of gas exchange, and were cared for at centers that reported fewer cases per year.

Improving prosthetic results through periodontal procedures.

The purpose of this article is to discuss how the periodontist can aid the restorative dentist in achieving the best prosthetic result. The procedures discussed include: surgical crown lengthening to provide access to subgingival preparation margins, esthetic gingival contouring to blend gingival architecture with tooth shape, esthetic root coverage by gingival grafts, grafting to prevent loss of alveolar plates in extraction sockets and preservation or correction of the alveolar ridge.

Ablation of lung endothelial injury after pacing-induced heart failure is related to alterations in Ca2+ signaling.

We have previously shown that ANG II increases microvascular permeability in normal dog lungs but not after pacing-induced heart failure. This study investigated how ANG II induces permeability in isolated blood-perfused canine lung lobes and what alterations occur during heart failure. In normal lobes, the protein kinase C (PKC) inhibitors staurosporine (500 nM) or chelerythrine (10 microM) did not modify ANG II-induced increases in the capillary filtration coefficient (Kf,c, ml . min-1 . cmH2O-1 . 100 g-1; an index of microvascular permeability), suggesting that PKC is not involved. Thapsigargin (150 nM) was used to stimulate capacitative Ca2+ entry in lobes from control dogs and dogs paced at 245 beats/min for 4 wk to induce heart failure. In control lobes, Kf,c rose after thapsigargin, from 0.06 +/- 0.01 to 0.17 +/- 0.03 ml . min-1 . cmH2O-1 . 100 g-1 (mean +/- SE, P < 0.05) but did not change in the paced group. A Ca2+ ionophore, A-23187, increased Kf,c in both control (10 microM; 0.05 +/- 0.01 to 0.17 +/- 0.05 ml . min-1 . cmH2O-1 . 100 g-1, P < 0.05) and pace (5 microM; 0.06 +/- 0.01 to 0. 21 +/- 0.07 ml . min-1 . cmH2O-1 . 100 g-1, P < 0.05) lobes, indicating that increasing intracellular Ca2+ is sufficient to induce pulmonary microvascular permeability after pacing. We conclude that during heart failure, Ca2+ signaling within the pulmonary microvascular endothelium is altered.

Pulmonary vascular response to angiotensin II in canine pacing-induced heart failure.

The effects of angiotensin II(ANG II) on pulmonary vascular resistance and microvascular permeability were studied in isolated, blood-perfused, ventilated canine lung lobes from control animals (n = 40) and animals with pacing-induced heart failure (n = 15). Conditioned dogs were paced (245 beats/min) for 30.6 +/- 0.9 (SE) days until left ventricular shortening fraction decreased by 56% (P < 0.05). Baseline pulmonary arterial resistance (Ra) (19.1 +/- 1.6 vs. 8.0 +/- 1.1 cmH2O.1(-1).min.100g) and venous resistance (Rv) (17.1 +/- 2.3 vs. 7.8 +/- 1.0 cmH2O.1(-1).min.100 g) were greater (P < 0.05) in the paced group compared with controls, respectively. Increments in Ra (delta Ra) and Rv(delta Rv) were measured after intra-arterial boluses of ANG II (1-10 micrograms). ANG II produced a dose-dependent response in delta Ra that was enhanced after pacing (P < 0.05). There was no effect on delta Rv in either group. At increased venous pressure (Pv = 20 cmH2O), the increments in delta Ra were significantly attenuated in both groups. In control lobes at low Pv, delta Ra and delta Rv both tended to decrease with increased lobar blood flow, suggesting that blood flow affects the pulmonary vascular response of ANG II. The baseline capillary filtration coefficient (Kf,c) was not different in the paced group compared with control, nor was there any effect of ANG II on Kf,c in the paced group. However, Kf,c did increase after ANG II in the control groups evaluated at either low or high Pv (P < 0.05). This difference in Kf,c was not seen if the experiment was done at increased Pv but without ANG II administration. We conclude that the pulmonary vasoconstrictor activity of ANG II is modestly enhanced in canine pacing-induced heart failure. Nonetheless, ANG II does not likely contribute to increased pulmonary vascular resistance in vivo in heart failure, since this effect was abolished at increased Pv. Finally, the absence of any effect of ANG II on pulmonary microvascular permeability in the paced group is suggestive of some adaptive remodeling of the capillary endothelial barrier.

Venovenous extracorporeal membrane oxygenation affects renal function.

OBJECTIVE: We evaluated the effect of venovenous extracorporeal membrane oxygenation (ECMO) on renal function and fluid balance in neonates with severe respiratory failure. DESIGN: We retrospectively reviewed the charts of 30 consecutive patients who met criteria for treatment with ECMO. Twelve were managed without ECMO (comparison group) and 18 were treated with venovenous ECMO (treatment group). SETTING: The study was conducted in a single level III neonatal intensive care unit in a regional children's hospital accepting medical and surgical neonatal transfers. Our hospital does not have an inborn service. PATIENTS: Neonates were included if their gestational age was more than 34 weeks, they weighed more than 2 kg, and their respiratory failure was severe enough to warrant consideration of ECMO as a mode of support. All the neonates in this study were treated with high-frequency ventilation before being considered for ECMO; none were treated with nitric oxide. Criteria used to determine whether a neonate was a candidate for ECMO included: (1) alveolar-arterial oxygen difference greater than 60 kPa (610 torr) for 8 hours; (2) alveolar-arterial oxygen difference greater than 59 kPa (605 torr) and a peak airway pressure greater than 3.7 kPa (38 cm H2O) for 4 hours; (3) oxygenation index greater than 40 on three of five postductal blood gases obtained at least 30 minutes apart and unstable patient condition; or (4) refractory, severe respiratory failure with sudden decompensation (partial pressure of arterial oxygen 3.4 kPa or lower, 35 torr) despite maximal medical management for 2 hours. We did not include patients with congenital diaphragmatic hernia. MAIN RESULTS: There were no differences between the groups in gestational age, birth weight, age at admission, gender, or diagnoses. Over the course of the 108 hours reviewed for each case, neonates treated with ECMO had higher positive fluid balance (P < .001), lower urine flow rates (P < .01), and higher blood urea nitrogen (P < .01) and creatinine (P < .01) levels than neonates managed without ECMO. There were no differences in mean blood pressure, protein intake, serum albumin, or use of diuretic therapy that might explain the differences between the groups. CONCLUSION: We conclude that venovenous ECMO is associated with transient impairment in renal function and marked fluid retention.