Extent Of Ablation Research Articles

Ablation of Myocardial Tissue With Nanosecond Pulsed Electric Fields

BackgroundAblation of cardiac tissue is an essential tool for the treatment of arrhythmias, particularly of atrial fibrillation, atrial flutter, and ventricular tachycardia. Current ablation technologies suffer from substantial recurrence rates, thermal side effects, and long procedure times. We demonstrate that ablation with nanosecond pulsed electric fields (nsPEFs) can potentially overcome these limitations.MethodsWe used optical mapping to monitor electrical activity in Langendorff-perfused New Zealand rabbit hearts (n = 12). We repeatedly inserted two shock electrodes, spaced 2–4 mm apart, into the ventricles (through the entire wall) and applied nanosecond pulsed electric fields (nsPEF) (5–20 kV/cm, 350 ns duration, at varying pulse numbers and frequencies) to create linear lesions of 12–18 mm length. Hearts were stained either with tetrazolium chloride (TTC) or propidium iodide (PI) to determine the extent of ablation. Some stained lesions were sectioned to obtain the three-dimensional geometry of the ablated volume.ResultsIn all animals (12/12), we were able to create nonconducting lesions with less than 2 seconds of nsPEF application per site and minimal heating (< 0.2°C) of the tissue. The geometry of the ablated volume was smoother and more uniform throughout the wall than typical for RF ablation. The width of the lesions could be controlled up to 6 mm via the electrode spacing and the shock parameters.ConclusionsAblation with nsPEFs is a promising alternative to radiofrequency (RF) ablation of AF. It may dramatically reduce procedure times and produce more consistent lesion thickness than RF ablation.

Discordance in lymphoid tissue recovery following stem cell transplantation in rhesus macaques: an in vivo imaging study

AbstractIonizing irradiation is used routinely to induce myeloablation and immunosuppression. However, it has not been possible to evaluate the extent of ablation without invasive biopsy. For lymphoid recovery, peripheral blood (PB) lymphocytes (PBLs) have been used for analysis, but they represent <2% of cells in lymphoid tissues (LTs). Using a combination of single-photon emission computed tomography imaging and a radiotracer (99mTc-labeled rhesus immunoglobulin G1 anti-CD4R1 (Fab′)2), we sequentially imaged CD4+ cell recovery in rhesus macaques following total body irradiation (TBI) and reinfusion of vector-transduced, autologous CD34+ cells. Our results present for the first time a sequential, real-time, noninvasive method to evaluate CD4+ cell recovery. Importantly, despite myeloablation of circulating leukocytes following TBI, total depletion of CD4+ lymphocytes in LTs such as the spleen is not achieved. The impact of TBI on LTs and PBLs is discordant, in which as few as 32.4% of CD4+ cells were depleted from the spleen. In addition, despite full lymphocyte recovery in the spleen and PB, lymph nodes have suboptimal recovery. This highlights concerns about residual disease, endogenous contributions to recovery, and residual LT damage following ionizing irradiation. Such methodologies also have direct application to immunosuppressive therapy and other immunosuppressive disorders, such as those associated with viral monitoring.

SURG-20A MULTICENTER SURVIVAL ANALYSIS OF UPFRONT LASER-ABLATION FOR TREATMENT OF PATIENTS WITH NEWLY DIAGNOSED GLIOBLASTOMA

SURG-20. A MULTICENTER SURVIVAL ANALYSIS OF UPFRONT LASER-ABLATION FOR TREATMENT OF PATIENTS WITH NEWLY DIAGNOSED GLIOBLASTOMA Alireza Mohammadi1, Veronica Chiang2, Thomas Beaumont3, Paul Elson1, Gene Barnett1, and Eric Leuthardt3; Cleveland Clinic, Cleveland, OH, USA; Yale University, New Haven, CT, USA; Washington University, St. Louis, MO, USA INTRODUCTION: Laser-ablation is a new treatment modality for difficult-to-access brain tumors. Limited data is available regarding the outcome of laser-ablation for patients with newly diagnosed glioblastoma (nGBM). We evaluated the outcomes of nGBM patients utilizing laserablation via the NeuroBlate system (NBS). METHODS: 32 nGBM patients had upfront treatment with NBS in Cleveland Clinic, Washington University inSt. Louis, andYaleUniversity (6/2011-12/2014).8patientswithmultifocal nGBMs or no radiation/chemotherapy after surgery were excluded. Study endpoints: progression-free survival (PFS time to progression or death from any cause), time to progression (TTP; like PFS but with censored 4 patients who died with causes other than progression), overall survival (OS time to death from any cause), disease-specific PFS (DS-PFS), and disease-specific OS (DS-OS). Deaths from reasons other than progression were considered a competing risk for DSPFS and DSOS. Extent of ablation was defined by NBS software as blue (438C for 10 minutes) and yellow (438C for 2 minutes) thermal-damage-threshold (TDT)-lines. Using recursive partitioning algorithm three prognostic groups were identified in respect to coverage of tumor by TDT-lines as favorable (n 1⁄4 8 patients); intermediate (n 1⁄4 9 patients); and unfavorable (n 1⁄4 7 patients). RESULTS: 58% were male and median age was 54 years. The median tumor volume was 9.33 cm. 18 (75%) patients progressed and 15 (62%) patients have died during extended follow up. Median OS is estimated to be 14.4 months, median TTP 5.3 months, and median PFS 4.3 months. In multivariate analysis, NBS coverage groups were significant prognostic factor for PFS (p 1⁄4 0.008), TTP (p 1⁄4 0.0005), DS-PFS (p 1⁄4 0.0002), and DS-OS (0.0001). Only age. 70 years (p 1⁄4 0.04) and tumor volume .11 cm (p 1⁄4 0.03) were significant poor prognostic factors for OS. CONCLUSIONS: The NBS coverage groups are independent predictor of all outcomes other than OS that can be translated as surgical extent of resection in nGBM outcome. Neuro-Oncology 17:v214–v220, 2015. doi:10.1093/neuonc/nov235.20 Published by Oxford University Press on behalf of the Society for Neuro-Oncology 2015.

Persistent atrial fibrillation ablation: conventional versus driver-guided strategy.

While pulmonary vein isolation for paroxysmal atrial fibrillation (AF) is highly effective, catheter ablation for persistent AF remains a challenge with varying clinical success reported. Several ablation techniques have been proposed to target persistent AF, with the additional ablation of complex fractionated electrograms and linear lesions shown to provide incremental success to pulmonary vein isolation alone. Recently, several studies have suggested the presence of localized drivers (re-entrant or focal) in AF. By targeting these drivers, clinical outcomes may be maintained while minimizing the extent of ablation. This article will focus on the conventional stepwise ablation approach for persistent AF versus driver-guided ablation with the use of newer mapping technologies.

Correlation of Reductions in Perfused Fibroid Volume With Subsequent Reductions in Total Fibroid Volume After Transcervical Radiofrequency Ablation.

Study Objective To determine if the extent of fibroid ablation, as reflected in a decrease in perfused fibroid volume three months after treatment, correlates with a reduction in total fibroid volume at 12 months. Design Prospective, longitudinal, multicenter, single-arm trial. Setting Academic and community hospitals in the United Kingdom, The Netherlands and Mexico. Patients 27 women with heavy menstrual bleeding secondary to fibroids. Intervention Radiofrequency ablation guided by built-in intrauterine sonography (the Sonata™ System). Measurements and Main Results The 27 patients had a total of 42 fibroids that were ablated. Contrast-enhanced MRI was used to determine the perfused and total fibroid volumes at baseline, at 3 months post-treatment and again at 12 months post-treatment. All MRI measurements were performed at a single core laboratory (MedQIA, Los Angeles, USA). Using a least squares method for linear regression, the change in total fibroid volume at 12 months as a function of the change in perfused fibroid volume at 3 months was found to have a correlation coefficient (R2) of 0.7518. The linear equation describing this relationship was y = 0.9919x + 0.0052. Conclusion There is a positive correlation between the reduction in perfused fibroid volume noted on contrast-enhanced MRI at 3 months after transcervical radiofrequency ablation and the reduction in total fibroid volume at 12 months. Thus, as larger portions of a fibroid are ablated, there will tend to be a greater reduction in total fibroid volume at 1 year.

Magnetic Resonance Thermometry-Guided Stereotactic Laser Ablation of Cavernous Malformations in Drug-Resistant Epilepsy: Imaging and Clinical Results.

Surgery is indicated for cerebral cavernous malformations (CCM) that cause medically refractory epilepsy. Real-time magnetic resonance thermography (MRT)-guided stereotactic laser ablation (SLA) is a minimally invasive approach to treating focal brain lesions. SLA of CCM has not previously been described. To describe MRT-guided SLA, a novel approach to treating CCM-related epilepsy, with respect to feasibility, safety, imaging, and seizure control in 5 consecutive patients. Five patients with medically refractory epilepsy undergoing standard presurgical evaluation were found to have corresponding lesions fulfilling imaging characteristics of CCM and were prospectively enrolled. Each underwent stereotactic placement of a saline-cooled cannula containing an optical fiber to deliver 980-nm diode laser energy via twist drill craniostomy. MR anatomic imaging was used to evaluate targeting prior to ablation. MR imaging provided evaluation of targeting and near real-time feedback regarding extent of tissue thermocoagulation. Patients maintained seizure diaries, and remote imaging (6-21 months post-ablation) was obtained in all patients. Imaging revealed no evidence of acute hemorrhage following fiber placement within presumed CCM. MRT during treatment and immediate post-procedure imaging confirmed desired extent of ablation. We identified no adverse events or neurological deficits. Four of 5 (80%) patients achieved freedom from disabling seizures after SLA alone (Engel class 1 outcome), with follow-up ranging 12-28 months. Reimaging of all subjects (6-21 months) indicated lesion diminution with surrounding liquefactive necrosis, consistent with the surgical goal of extended lesionotomy. Minimally invasive MRT-guided SLA of epileptogenic CCM is a potentially safe and effective alternative to open resection. Additional experience and longer follow-up are needed.

Polarimetric assessment of healthy and radiofrequency ablated porcine myocardial tissue

Radiofrequency (RF) ablation offers a potential treatment for cardiac arrhythmia, where properly titrated energy delivered at critical sites can destroy arrhythmogenic foci. The resulting ablation lesion typically consists of a core (coagulative necrosis) surrounded by a rim of mixed viable and non-viable cells. The extent of the RF lesion is difficult to delineate with current imaging techniques. Here, we explore polarization signatures of ten ex-vivo samples from untreated (n=5) and RF ablated porcine hearts (n=5), in backscattered geometry through Mueller matrix polarimetry. Significant differences (p<0.01) in depolarization, ΔT , were observed between the healthy, RF ablated and rim regions. Linear retardance, δ, was significantly lower in the core and rim regions compared to healthy regions (p<0.05). The results demonstrate a novel application of polarimetry, namely the characterization of RF ablation extent in myocardium, including the visualization of the important lesion rim region. White light photo (top) of porcine myocardium tissue with radiofrequency ablation lesion and corresponding depolarization map (bottom). Depolarization is useful for visualizing the lesion core and rim.

Effect of catheter ablation on quality of life in patients with atrial fibrillation and its correlation with arrhythmia outcome

ObjectiveTo assess the effect of catheter ablation on atrial fibrillation (AF) symptoms and quality of life (QoL).MethodsPatients with AF scheduled for ablation were recruited. Pulmonary vein isolation (PVI) was performed...

Impact of analyte ablation and surface acidity of Pd nanoparticles on efficiency of surface-assisted laser desorption/ionization-mass spectrometry

In this study, the impact of analyte ablation and substrate surface acidity on ion yield in surface-assisted laser desorption/ionization-mass spectrometry (SALDI-MS) from Pd nanoparticles was examined. The extent of analyte removal from the Pd material was investigated by X-ray analysis and compared to conventional desorption/ionization on silicon (DIOS) and matrix-assisted laser desorption/ionization (MALDI). Despite the different surface morphologies of the investigated materials and the widely varying ionization yields observed during the experiments, virtually the same amount of analyte was removed by laser irradiation from each of the investigated substrates at a given laser fluence. Our experiments therefore suggested that the extent of analyte ablation from the substrate was less important for SALDI efficiency than the chemical properties of the surface.

Efficient Lattice Boltzmann Solver for Patient-Specific Radiofrequency Ablation of Hepatic Tumors.

Radiofrequency ablation (RFA) is an established treatment for liver cancer when resection is not possible. Yet, its optimal delivery is challenged by the presence of large blood vessels and the time-varying thermal conductivity of biological tissue. Incomplete treatment and an increased risk of recurrence are therefore common. A tool that would enable the accurate planning of RFA is hence necessary. This manuscript describes a new method to compute the extent of ablation required based on the Lattice Boltzmann Method (LBM) and patient-specific, pre-operative images. A detailed anatomical model of the liver is obtained from volumetric images. Then a computational model of heat diffusion, cellular necrosis, and blood flow through the vessels and liver is employed to compute the extent of ablated tissue given the probe location, ablation duration and biological parameters. The model was verified against an analytical solution, showing good fidelity. We also evaluated the predictive power of the proposed framework on ten patients who underwent RFA, for whom pre- and post-operative images were available. Comparisons between the computed ablation extent and ground truth, as observed in postoperative images, were promising (DICE index: 42%, sensitivity: 67%, positive predictive value: 38%). The importance of considering liver perfusion while simulating electrical-heating ablation was also highlighted. Implemented on graphics processing units (GPU), our method simulates 1 minute of ablation in 1.14 minutes, allowing near real-time computation.

The effects of anatomic variations on stereotactic laser amygdalohippocampectomy and a proposed protocol for trajectory planning.

Stereotactic laser amygdalohippocampectomy (SLAH) is a promising minimally invasive alternative for mesial temporal lobe epilepsy. As seizure outcome has been associated with the extent of amygdalar and hippocampal ablation, it is important to select a safe trajectory optimizing involvement of both structures; however, variations in temporal anatomy significantly affect the overall complexity of planning. To quantify anatomic variables of SLAH and facilitate stereotactic planning by developing a protocol for optimally targeting the amygdalohippocampal complex (AHC). We performed a retrospective analysis of 19 SLAHs. Anatomic measurements from preoperative magnetic resonance imaging and laser trajectory measurements from coregistered postoperative magnetic resonance imaging were taken in 11 patients. Simple linear regression analysis was performed to identify significant predictor variables determining ablation extent. Based on these data, a protocol for optimal trajectory planning was developed and subsequently implemented in 8 patients. The medial angle of the laser trajectory correlated with the medial angle of the AHC. The length of amygdalar cannulation was predictive of its ablation volume. All trajectories passed through a posteroinferior corridor formed by the lateral ventricle superiorly and collateral sulcus inferiorly. Our protocol facilitated planning and increased the volume of AHC ablation. The medial AHC angle dictates the medial trajectory angle and a path from the posteroinferior corridor through the hippocampus and the center of the amygdala dictates the caudal angle. These observations led to a protocol for long-axis AHC cannulation that maintains an extraventricular trajectory to minimize hemorrhage risk and targets the center of the amygdala to optimize ablation volumes.

Randomized Controlled Trial Comparing the Efficacy of Impedance Control and Temperature Control of Radiofrequency Interstitial Thermal Ablation for Treating Small Hepatocellular Carcinoma

Objectives: A randomized controlled trial was conducted to evaluate the efficacy of impedance control of a radiofrequency interstitial thermal ablation system (RITA) used to treat hepatocellular carcinoma (HCC). Methods: Fifteen patients with hypervascular HCCs <20 mm in diameter were randomly treated with radiofrequency ablation (RFA) using conventional temperature control (group A) or impedance control methods (group B). RITA needle electrodes were used in all cases. We compared ablation time, extent of lesion ablation, and energy use between the two groups. Results: The median long and short diameters of the axial cross sections of radiofrequency-induced necrotic areas visualized by CT were 32 mm (range, 26-36) and 25 mm (20-31) in group A and 32 mm (28-40) and 31 mm (24-37) in group B, respectively. The short diameter of group B patients was significantly greater than that of group A patients (p = 0.029). The median ablation time was 18.8 min in group A and 13.4 min in group B, thus significantly shorter in group B (p = 0.001). The energy requirement did not differ significantly between the groups. Conclusions: Impedance control of the RITA system resulted in an increased size of the ablation zone and a decreased ablation time.

Atrial fibrillation cycle length as a predictor for the extent of substrate ablation.

Atrial fibrillation (AF) cycle length (CL) has been demonstrated to be one of the predictors for termination during ablation for AF. We evaluated the AF CL gradient between right atrium (RA) and left atrium (LA) and their mean AF CL in predicting the extent of substrate ablation. One-hundred and thirty-six patients undergoing first ablation for persistent AF were studied. Stepwise ablation, sequentially in the following order: pulmonary veins (PV), LA, and RA, was performed to achieve AF termination. Stepwise ablation terminated AF in 110 patients (81%). In the AF termination group, AF was terminated by PV isolation (PVI) (Group P), PVI plus LA ablation (Group L), and PVI plus LA plus RA ablation (Group R) in 14 patients (13%), 49 patients (44%), and 47 patients (43%), respectively. Group R had much shorter mean AF CL than Group L (156 ± 18 vs. 174 ± 24 ms, P < 0.001) and mean AF CL in Group L was much shorter than Group P (174 ± 24 vs. 209 ± 36 ms, P = 0.004). The RA to LA AF CL gradient was not significantly different between left-side ablation (Group P + Group L) and additional RA ablation (Group R) (P = 0.177). Mean AF CL >180.50 ms predicted AF termination by PVI (Group P) with 79% sensitivity and 84% specificity while mean AF CL >165.25 ms predicted AF termination by left-side ablation (Group P + Group L) with 67% sensitivity and 75% specificity. After a mean follow-up of 15 ± 7 months, freedom from arrhythmia recurrence was significantly higher in left-side ablation (Group P + Group L) than additional RA ablation (Group R) (P = 0.024). Baseline mean AF CL may identify the subset of patients in whom persistent AF can be terminated by different extent of substrate ablation, which may in turn predict the chance of recurrence. However, baseline RA to LA AF CL gradient cannot predict the need for additional RA ablation.

Modulating electrolytic tissue ablation with reversible electroporation pulses

Electrolytic ablation is a minimally invasive tissue ablation technique that operates by delivering low magnitude direct current to the target region over long periods of time, generating electrolytic products that destroy cells. Our study seeks to examine the hypothesis that permeabilizing the cell membrane with reversible electroporation will reduce the electrolytic dose required for tissue ablation, by exposing the interior of the cell to the electrolytic products. The hypothesis is examined by evaluating the extent of tissue damage when electrolytic and reversible electroporation sequences are delivered separately and in combination, it in vivo, to rat liver tissue. The study shows that combining reversible electroporation with electrolysis produces a substantial increase in the extent of tissue ablation compared to that achieved by electrolysis alone.

Scar dechanneling: new method for scar-related left ventricular tachycardia substrate ablation.

Ventricular tachycardia (VT) substrate ablation usually requires extensive ablation. Scar dechanneling technique may limit the extent of ablation needed. The study included 101 consecutive patients with left ventricular scar-related VT (75 ischemic patients; left ventricular ejection fraction, 36 ± 13%). Procedural end point was the elimination of all identified conducting channels (CCs) by ablation at the CC entrance followed by abolition of residual inducible VTs. By itself, scar dechanneling rendered noninducibility in 54.5% of patients; ablation of residual inducible VT increased noninducibility to 78.2%. Patients needing only scar dechanneling had a shorter procedure (213 ± 64 versus 244 ± 71 minutes; P = 0.027), fewer radiofrequency applications (19 ± 11% versus 27 ± 18%; P = 0.01), and external cardioversion/defibrillation shocks (20% versus 65.2%; P < 0.001). At 2 years, patients needing scar dechanneling alone had better event-free survival (80% versus 62%) and lower mortality (5% versus 11%). Incomplete CC-electrogram elimination was the only independent predictor (hazard ratio, 2.54 [1.06-6.10]) for the primary end point. Higher end point-free survival rates were observed in patients noninducible after scar dechanneling (log-rank P = 0.013) and those with complete CC-electrogram elimination (log-rank P = 0.013). The complications rate was 6.9%, with no deaths. Scar dechanneling alone results in low recurrence and mortality rates in more than half of patients despite the limited ablation extent required. Residual inducible VT ablation improves acute results, but patients who require it have worse outcomes. Recurrences are mainly related to incomplete CC-electrogram elimination.

Combined Radiofrequency Ablation and Double Anti-Angiogenic Protein Therapy to Increase Coagulation Efficacy: An Experimental Study in a Murine Renal Carcinoma Model.

ObjectiveTo evaluate whether suppression of tumor microvasculature by double anti-angiogenic protein (DAAP) treatment could increase the extent of radiofrequency ablation (RFA)-induced coagulation in a murine renal cell carcinoma model.Materials and MethodsRenal cell carcinoma cell lines were implanted subcutaneously into 10 nude mice. Four mice received adenoviral DAAP treatment and 6 mice received sterile 0.9% saline solution as DAAP-untreated group. The effect of DAAP was evaluated according to the vascularity by contrast-enhanced ultrasound (CEUS) using microbubbles. Four DAAP-treated mice and 4 DAAP-untreated mice were then treated with RFA, resulting in 3 groups: no-therapy (n = 2), RFA only (n = 4), and RFA combined with DAAP treatment (n = 4). Immediately after RFA, the size of coagulation necrosis and mitochondrial enzyme activity were compared between the groups using analysis of variance (ANOVA) and post hoc test.ResultsThe contrast enhancement ratio for tumor vascularization on CEUS was significantly lower in the DAAP treated group than in DAAP-untreated group (30.2 ± 9.9% vs. 77.4 ± 17.3%; p = 0.021). After RFA, the mean coagulation diameter was 0 mm for no-therapy group, 6.7 ± 0.7 mm for the RFA only group and 8.5 ± 0.4 mm for the RFA with DAAP group (ANOVA, p < 0.001). The area of viable mitochondria within the tumor was 27.9 ± 3.9% in no-therapy group, 10.3 ± 4.5% in the RFA only group, and 2.1 ± 0.7% in the RFA with DAAP group (ANOVA, p < 0.001).ConclusionOur results suggest the potential value of combining RFA with anti-angiogenic therapy.

Image-Guided Robot-Assisted Prostate Ablation Using Water Jet-Hydrodissection: Initial Study of a Novel Technology for Benign Prostatic Hyperplasia

To evaluate the safety and efficacy of a novel robotic tissue ablation system (PROCEPT Aquablation(™) System), in performing prostate ablation in a survival canine model. This novel technology uses a high-velocity saline stream that aims to selectively ablate prostatic glandular tissue while sparing collagenous structures such as blood vessels and capsule. Once the ablation is complete, a laser beam is captured by a low-pressure water jet to produce surface hemostasis. The extent and depth of ablation is predetermined by endoscopic and transrectal ultrasonography guidance. The procedure was performed in eight noncastrated male beagles aged 6 years or older (Acute 2, Chronic 6) through a previously created perineal urethrostomy. Aquablation time ranged from 40 to 84 seconds (mean 60.5 sec). There was no active bleeding in any of the dogs during or after Aquablation. Water jet-guided laser coagulation was used for purposes of monitoring its safety and efficacy. Five of the six dogs reached the predetermined 6-week mark. Complications included two dogs with infection successfully treated with antibiotics, a false passage created during catheter placement, and two bladder neck perforations (from mechanical insertion), one leading to euthanasia. Histologic evaluation at 6 weeks revealed a normal cellular architecture and full reepithelialization of the treatment cavity. We report the initial survival data in the animal model of a novel robotic device developed for managing symptomatic benign prostatic hyperplasia (BPH). Aquablation produces ablation of adenomatous elements while preserving collagenous structures and is a promising technology for surgical management of symptomatic BPH.

Atrial tachycardias following atrial fibrillation ablation.

One of the most important proarrhythmic complications after left atrial (LA) ablation is regular atrial tachycardia (AT) or flutter. Those tachycardias that occur after atrial fibrillation (AF) ablation can cause even more severe symptoms than those from the original arrhythmia prior to the index ablation procedure since they are often incessant and associated with rapid ventricular response. Depending on the method and extent of LA ablation and on the electrophysiological properties of underlying LA substrate, the reported incidence of late ATs is variable. To establish the exact mechanism of these tachycardias can be difficult and controversial but correlates with the ablation technique and in the vast majority of cases the mechanism is reentry related to gaps in prior ablation lines. When tachycardias occur, conservative therapy usually is not effective, radiofrequency ablation procedure is mostly successful, but can be challenging, and requires a complex approach.

Effect of Biological Characteristics of Different Types of Uterine Fibroids, as Assessed with T2-Weighted Magnetic Resonance Imaging, on Ultrasound-Guided High-Intensity Focused Ultrasound Ablation

The aims of this study were to assess the effects of the biological characteristics of different types of uterine fibroids, as assessed with T2-weighted magnetic resonance imaging (MRI), on ultrasound-guided high-intensity focused ultrasound (USgHIFU) ablation. Thirty-five patients with 39 symptomatic uterine fibroids who underwent myomectomy or hysterectomy were enrolled. Before surgery, the uterine fibroids were subdivided into hypo-intense, iso-intense, heterogeneous hyper-intense and homogeneous hyper-intense categories based on signal intensity on T2-weighted MRI. Tissue density and moisture content were determined in post-operative samples and normal uterine tissue, the isolated uterine fibroids were subjected to USgHIFU, and the extent of ablation was measured using triphenyltetrazolium chloride. Hematoxylin and eosin staining and sirius red staining were undertaken to investigate the organizational structure of the uterine fibroids. Estrogen and progesterone receptor expression was assayed via immunohistochemical staining. The mean diameter of uterine fibroids was 6.9 ± 2.8 cm. For all uterine fibroids, the average density and moisture content were 10.7 ± 0.7 mg/mL and 75.7 ± 2.4%, respectively; and for the homogeneous hyper-intense fibroids, 10.3 ± 0.5 mg/mL and 76.6 ± 2.3%. The latter subgroup had lower density and higher moisture content compared with the other subgroups. After USgHIFU treatment, the extent of ablation of the hyper-intense fibroids was 102.7 ± 42.1 mm2, which was significantly less than those of the hypo-intense and heterogeneous hyper-intense fibroids. Hematoxylin and eosin staining and sirius red staining revealed that the homogeneous hyper-intense fibroids had sparse collagen fibers and abundant cells. Immunohistochemistry results revealed that estrogen and progesterone receptors were highly expressed in the homogeneous hyper-intense fibroids. This study revealed that lower density, higher moisture content, sparse collagen fibers, abundant cells and overexpression of estrogen and progesterone receptors are important biological characteristics that resulted in poor efficacy in the treatment of homogeneous hyper-intense fibroids.

Expansion of the Endosteal Hematopoietic Stem Cell Niche Following Myeloablative and Reduced Intensity Conditioning Is Triggered By Hematopoietic Cell Loss

The efficiency and durability of donor hematopoietic stem cell (HSC) engraftment at specialized niches within recipient bone marrow (BM) are critical determinants of successful clinical stem cell transplant (SCT). Osteolineage elements of BM niches play active, critical roles in regulating HSC engraftment, differentiation, and self-renewal both during homeostasis and post-SCT. We have previously shown that SCT preparative regimens consisting of myeloablative total body irradiation (MB-TBI) result in expansion of osteolineage niche cells at the endosteal surface of metaphyseal bone. This expansion is facilitated by IGF-1 and megakaryocyte-derived PDGF-BB signaling, and is required for optimal HSC engraftment. However, the pathway that integrates these signals to induce expansion remains undefined, and whether expansion is unique to conditioning with MB-TBI due to direct effects on osteolineage cells is also not known. We now present data using chemotherapy-based and reduced intensity conditioning (RIC) models, demonstrating that niche expansion is triggered by hematopoietic cell loss, and not by direct effects of conditioning agents on the niche.In vitro, MB-TBI (1125 cGy) inhibited primary murine osteoblast (OB) growth and increased apoptosis (Annexin V+ OB at 72 hours: TBI 17% versus control 4%, p < 0.001). In contrast, busulfan treatment caused significantly less OB growth inhibition versus MB-TBI, with no increased apoptosis compared to sham-treated controls. We therefore conditioned wildtype (WT) C57BL/6 mice with myeloablative busulfan (Day -7 to -4) and cyclophosphamide (Day -3 to -2) (BuCy) in a schedule similar to clinical SCT regimens. Endosteal niche expansion increased over this time course, correlating with the extent of hematopoietic ablation, with most expansion occurring prior to cyclophosphamide administration. Maximal expansion occurred by the end of the treatment course, and based on a quantitative scoring index, was not significantly different than maximal MB-TBI-induced niche expansion, demonstrating that niche expansion is not specific to radiation-based conditioning. As with MB-TBI treatment, BuCy-treated recipients of GFP+donor BM consistently exhibited >95% donor chimerism.We next investigated whether RIC regimens can mediate niche expansion, using an anti-cKit antibody (clone ACK2) known to enable donor engraftment when administered alone in immunodeficient mice or in combination with low dose irradiation (LD-TBI, 300 cGy) in WT mice. ACK2 treatment alone resulted in modest endosteal cell expansion (33% of MB-TBI induced expansion), correlating with transient reductions in host BM cellularity, but absence of definitive donor engraftment in ACK2-treated WT mice. In contrast, LD-TBI alone or in combination with ACK2 produced 58% and 74%, respectively, of the endosteal expansion seen following MB-TBI. Interestingly, while these regimens reduced total BM cellularity by 85% (LD-TBI) and 93% (LD-TBI + ACK2), and led to clearance of BM Lin-Sca1+cKit+(LSK) progenitors, this lack of full niche expansion correlated with incomplete and inconsistent donor chimerism in SCT recipients.Finally, to prove that endosteal niche expansion results from signals triggered specifically by hematopoietic cell loss, we crossed mice expressing Cre-recombinase under control of the CD45 promoter (CD45Cre) with mice expressing inducible diphtheria toxin receptor (iDTRlox). When treated with diphtheria toxin (DT), BM cellularity in these mice was reduced by 90%, and this targeted ablation of hematopoietic cells was sufficient to induce similar expansion of endosteal mesenchymal cells as seen with radiation or chemotherapy-based conditioning regimens.Taken together, our results demonstrate that endosteal niche expansion occurs in response to both radiation- and chemotherapy-based SCT conditioning, and that the degree of expansion correlates with both conditioning intensity and with the subsequent degree of donor cell engraftment/chimerism in SCT recipients. Importantly, expansion is triggered not by direct effects of the preparative regimen on mesenchymal niche cells, but rather by loss of hematopoietic cells. These findings provide important insights into how SCT conditioning modulates niche function, and suggests that therapeutic strategies to enhance niche function may be effective in improving engraftment outcomes following RIC SCT. DisclosuresNo relevant conflicts of interest to declare.