Comparison of transseptal puncture using a dedicated RF wire versus a mechanical needle with and without electrification in an animal model.

INTRODUCTION: Mechanical force to achieve transseptal puncture (TSP) using a standard needle may lead to overshooting and injury, and can potentially be avoided using a radiofrequency (RF)-powered needle or wire. Applying electrocautery to needles and guidewires as an alternative to purpose-built RF systems has been associated with safety risks, such as tissue coring and thermal damage. The commercially available AcQCross needle-dilator system (Medtronic) features a sharp open-ended needle for mechanical puncture, as well as a built-in connector to enable energy delivery for RF puncture. This investigation compares the safety and efficacy of the AcQCross needle to the dedicated VersaCross RF wire system and generator (Baylis Medical/Boston Scientific). METHODS: In an ex vivo porcine model, VersaCross wire punctures were performed using 1 s, constant mode (approx. 10 W) with maximum two attempts. AcQCross punctures were performed by applying energy for 2 s using a standard electrosurgical generator at 10 W (max. five attempts), 20 W (max. two attempts), and 30 W (max. two attempts). Efficacy was assessed in terms of puncture success and a number of energy applications required for TSP. Safety was assessed quantitatively as force required for TSP, energy required to puncture, and incidence of tissue coring, as well as by qualitative assessment of puncture sites. Additional qualitative observation of tissue cores and debris were obtained from TSP performed in live swine. RESULTS: RF TSP was 100% successful using the VersaCross wire with 1.0 ± 0.0 attempts. When power was used with the AcQCross needle, it failed to puncture at low (10 and 20 W) power settings; TSP was achieved with 30 W of energy with 91% success using 1.53 ± 0.51 attempts (p < .05 vs. VC) with greater variability (F1,33 = 9223.5, p < .0001). Compared to RF puncture using the VersaCross system, mechanical puncture, alone, using the AcQcross needle required six times more force (8 mm additional forward device displacement) to perforate the septum. Qualitative assessment of puncture sites revealed larger defects and more tissue charring with the AcQCross needle at 30 W compared to punctures with VersaCross wire. Tissue coring with the open-ended AcQCross needle was observed in vivo and measured to occur in 57% of punctures using the ex vivo model; no coring was observed with the closed-tip VersaCross wire. CONCLUSIONS: The AcQCross needle frequently required higher energy of 30 W to achieve RF TSP and was associated with tissue coring and charring, which have been, previously, reported when electrifying a standard open-ended mechanical needle or guidewire. These findings may limit safety and effectiveness compared to the VersaCross system.

A new transseptal solution for enabling left atrial access of large delivery sheaths.

BACKGROUND: Transseptal access for large sheaths may be encumbered by tissue resistance against the sheath-dilator stepped interface. The ExpanSure Large Access Transseptal Dilator (Baylis Medical) is designed as a single introducer and dilation device with a smooth sheath-dilator transition to support transseptal puncture. It may facilitate ease and efficiency of interatrial crossing. METHODS: This study experimentally evaluated the crossing force of ExpanSure relative to a conventional 8.5 F Swartz SL1 transseptal sheath and dilator in a benchtop septum model. Its ability to reduce the subsequent crossing force of a 14 F WATCHMAN delivery sheath was also tested. The clinical use of ExpanSure, including procedure time, was then validated in a series of left atrial appendage closure (LAAC) procedures. RESULTS: In a benchtop septum model (N = 12), less peak force (1.90 ± 0.08 N vs. 2.36 ± 0.09 N; p < .001) and overall work (17.3 ± 1.2 mJ vs. 28.0 ± 1.9 mJ; p < .001) were required to advance ExpanSure relative to a conventional SL1 transseptal sheath and dilator system. Peak force (2.34 ± 0.24 N vs. 2.65 ± 0.21 N; p < .003) and overall work (28.5 ± 3.9 mJ vs. 35.4 ± 2.1 mJ; p < .001) to advance a WATCHMAN sheath were also significantly lower after using ExpanSure than after using a conventional transseptal system. In 19 LAAC procedures, ExpanSure crossed the septum smoothly and integrated readily, which enabled efficient procedure completion (mean total procedure time 37.6 ± 13.5 min), with 100% success and no procedure-related complications. CONCLUSION: Experimental force measurements, combined with early clinical experience using ExpanSure, suggest that the tapered design with smooth transition without dilator-sheath step-up and the larger diameter, both facilitated ease and efficiency of interatrial crossing.

Calcium Sensing Receptor Function Supports Osteoblast Survival and Acts as a Co-Factor in PTH Anabolic Actions in Bone.

Anabolic actions of PTH in bone involve increased deposition of mineralizing matrix. Regulatory feedback of the process may be important to maintain calcium homeostasis and, in turn, calcium may inform the process. This investigation clarified the role of calcium availability and the calcium sensing receptor (CaSR) in the anabolic actions of PTH. CaSR function promoted osteoblastic cell numbers, with lower cell numbers in post-confluent cultures of primary calvarial cells from Col1-CaSR knock-out (KO) mice, and for calvarial cells from wild-type (WT) mice treated with a calcilytic. Increased apoptosis of calvarial cells with calcilytic treatment suggested CaSR is critical for protection against stage-dependent cell death. Whole and cortical, but not trabecular, bone parameters were significantly lower in Col1-CaSR KO mice versus WT littermates. Intact Col1-CaSR KO mice had lower serum P1NP levels relative to WT. PTH treatment displayed anabolic actions in WT and, to a lesser degree, KO mice, and rescued the lower P1NP levels in KO mice. Furthermore, PTH effects on whole tibiae were inhibited by osteoblast-specific CaSR ablation. Vertebral body implants (vossicles) from untreated Col1-CaSR KO and WT mice had similar bone volumes after 4 weeks of implantation in athymic mice. These findings suggest that trabecular bone formation can occur independently of the CaSR, and that the CaSR plays a collaborative role in the PTH anabolic effects on bone. J. Cell. Biochem. 117: 1556-1567, 2016. © 2015 Wiley Periodicals, Inc.

The soluble interleukin-6 receptor is a mediator of hematopoietic and skeletal actions of parathyroid hormone.

Both PTH and IL-6 signaling play pivotal roles in hematopoiesis and skeletal biology, but their interdependence is unclear. The purpose of this study was to evaluate the effect of IL-6 and soluble IL-6 receptor (sIL-6R) on hematopoietic and skeletal actions of PTH. In the bone microenvironment, PTH stimulated sIL-6R protein levels in primary osteoblast cultures in vitro and bone marrow in vivo in both IL-6(+/+) and IL-6(-/-) mice. PTH-mediated hematopoietic cell expansion was attenuated in IL-6(-/-) compared with IL-6(+/+) bone marrow, whereas sIL-6R treatment amplified PTH actions in IL-6(-/-) earlier than IL-6(+/+) marrow cultures. Blocking sIL-6R signaling with sgp130 (soluble glycoprotein 130 receptor) inhibited PTH-dependent hematopoietic cell expansion in IL-6(-/-) marrow. In the skeletal system, although intermittent PTH administration to IL-6(+/+) and IL-6(-/-) mice resulted in similar anabolic actions, blocking sIL-6R significantly attenuated PTH anabolic actions. sIL-6R showed no direct effects on osteoblast proliferation or differentiation in vitro; however, it up-regulated myeloid cell expansion and production of the mesenchymal stem cell recruiting agent, TGF-ß1 in the bone marrow microenvironment. Collectively, sIL-6R demonstrated orphan function and mediated PTH anabolic actions in bone in association with support of myeloid lineage cells in the hematopoietic system.

Apoptotic osteocytes regulate osteoclast precursor recruitment and differentiation in vitro.

Fatigue loading causes a spatial distribution of osteocyte apoptosis co-localized with bone resorption spaces peaking around microdamage sites. Since osteocytes have been shown to regulate osteoclast formation and activity, we hypothesize that osteocyte apoptosis regulates osteoclastogenesis. In this study, we used serum-starvation to mimic reduced nutrient transport in microdamaged bone and induce apoptosis in MLO-Y4 osteocyte-like cells; conditioned medium was used to apply soluble factors released by apoptotic osteocytes (aOCY) to healthy non-apoptotic MLO-Y4 cells. Osteoclast precursor (RAW264.7 monocyte) migration and differentiation were assessed in the presence of conditioned media (CM) from: (A) aOCY, (B) osteocytes treated with apoptosis conditioned medium (i.e., healthy osteocytes in the presence of apoptosis cues; apoptosis CM-treated osteocytes (atOCY)), and (C) osteocytes treated with non-apoptosis conditioned medium (i.e., healthy osteocytes in the absence of apoptosis cues; non-apoptosis CM-treated osteocytes (natOCY)). Receptor activator for nuclear factor-κB ligand (RANKL), macrophage colony stimulating factor (M-CSF), vascular endothelial growth factor (VEGF) and osteoprotegerin (OPG) mRNA, and protein expression were measured. Our findings indicate that soluble factors released by aOCY and atOCY promoted osteoclast precursor migration (up to 64% and 24% increase, respectively) and osteoclast formation (up to 450% and 265% increase, respectively). Osteoclast size increased up to 233% in the presence of aOCY and atOCY CM. Recruitment, formation and size were unaltered by natOCY. RANKL mRNA and protein expression were upregulated only in aOCY, while M-CSF and VEGF increased in atOCY. Addition of RANKL-blocking antibody abolished aOCY-induced osteoclast precursor migration and osteoclast formation. VEGF and M-CSF blocking antibodies abolished atOCY-induced osteoclastogenesis. These findings suggest that aOCY directly and indirectly (through atOCY) initiate targeted bone resorption by regulating osteoclast precursor recruitment and differentiation.

Effect of low-magnitude, high-frequency vibration on osteocytes in the regulation of osteoclasts.

Osteocytes are well evidenced to be the major mechanosensor in bone, responsible for sending signals to the effector cells (osteoblasts and osteoclasts) that carry out bone formation and resorption. Consistent with this hypothesis, it has been shown that osteocytes release various soluble factors (e.g. transforming growth factor-beta, nitric oxide, and prostaglandins) that influence osteoblastic and osteoclastic activities when subjected to a variety of mechanical stimuli, including fluid flow, hydrostatic pressure, and mechanical stretching. Recently, low-magnitude, high-frequency (LMHF) vibration (e.g., acceleration less than <1 x g, where g=9.81m/s(2), at 20-90 Hz) has gained much interest as studies have shown that such mechanical stimulation can positively influence skeletal homeostasis in animals and humans. Although the anabolic and anti-resorptive potential of LMHF vibration is becoming apparent, the signaling pathways that mediate bone adaptation to LMHF vibration are unknown. We hypothesize that osteocytes are the mechanosensor responsible for detecting the vibration stimulation and producing soluble factors that modulate the activity of effector cells. Hence, we applied low-magnitude (0.3 x g) vibrations to osteocyte-like MLO-Y4 cells at various frequencies (30, 60, 90 Hz) for 1h. We found that osteocytes were sensitive to this vibration stimulus at the transcriptional level: COX-2 maximally increased by 344% at 90Hz, while RANKL decreased most significantly (-55%, p<0.01) at 60Hz. Conditioned medium collected from the vibrated MLO-Y4 cells attenuated the formation of large osteoclasts (> or =10 nuclei) by 36% (p<0.05) and the amount of osteoclastic resorption by 20% (p=0.07). The amount of soluble RANKL (sRANKL) in the conditioned medium was found to be 53% lower in the vibrated group (p<0.01), while PGE(2) release was also significantly decreased (-61%, p<0.01). We conclude that osteocytes are able to sense LMHF vibration and respond by producing soluble factors that inhibit osteoclast formation.