Tenascin-C-enriched regeneration-specific extracellular matrix guarantees superior muscle regeneration in Ambystoma mexicanum

Severe muscle injury causes distress and difficulty in humans. Studying the high regenerative ability of the axolotls may provide hints for the development of an effective treatment for severe injuries to muscle tissue. Here, we examined the regenerative process in response to a muscle injury in axolotls. We found that axolotls are capable of complete regeneration in response to a partial muscle resection called volumetric muscle loss (VML), which mammals cannot perfectly regenerate. We investigated the mechanisms underlying this high regenerative capacity in response to VML, focusing on the migration of muscle satellite cells and the extracellular matrix (ECM) formed during VML injury. Axolotls form tenascin-C (TN-C)-enriched ECM after VML injury. This TN-C-enriched ECM promotes the satellite cell migration. We confirmed the importance of TN-C in successful axolotl muscle regeneration by creating TN-C mutant animals. Our results suggest that the maintenance of a TN-C-enriched ECM environment after muscle injury promotes the release of muscle satellite cells and supports eventually high muscle regenerative capacity. In the future, better muscle regeneration may be achieved in mammals through the maintenance of TN-C expression.

FGF signaling induces the regeneration of collagen fiber structure during skin wound healing in axolotls

Axolotls have been considered to be able to regenerate their skin completely. Our recent study updated this theory with the finding that the lattice structure of dermal collagen fibers was not fully regenerated after skin injury. We also discovered that nerves induce the regeneration of collagen fibers. The mechanism of collagen fiber regeneration remains unknown, however. In this study, we focused on the structure of collagen fibers with collagen braiding cells, and cell origin in axolotl skin regeneration. In the wounded dermis, cells involved in skin repair/regeneration were derived from both the surrounding dermis and the subcutaneous tissue. Regardless of cell origin, cells acquired the proper cell morphology to braid collagen fiber with nerve presence. We also found that FGF signaling could substitute for the nerve roles in the conversion of subcutaneous fibroblasts to lattice-shaped dermal fibroblasts. Our findings contribute to the elucidation of the fundamental mechanisms of true skin regeneration and provide useful insights for pioneering new skin treatments.

Bead Implantation and Delivery of Exogenous Growth Factors

Genetic methods in axolotls (Ambystoma mexicanum) remain in their infancy which has hampered the study of limb regeneration. There is much room for advancement, especially with respect to spatiotemporal regulation of gene expression. Secreted growth factors play a major role in each stage of regeneration. The use of slow-release beads is one of the most effective methods to control the spatiotemporal expression of secretory gene products. The topical administration of secreted factors by slow-release beads may also prove effective for future applications in non-regenerative animals and for medical applications in humans, in which genetic methods are not available. In this chapter, we describe a methodology for using and implanting slow-release beads to deliver exogenous growth factors to salamanders.

Spinocerebellar ataxia type 17-digenic TBP/STUB1 disease: neuropathologic features of an autopsied patient

Spinocerebellar ataxia (SCA) type 17-digenic TBP/STUB1 disease (SCA17-DI) has been recently segregated from SCA17, caused by digenic inheritance of two gene mutations - intermediate polyglutamine-encoding CAG/CAA repeat expansions (polyQ) in TBP (TBP_41 - 49) and STUB1 heterozygosity - the former being associated with SCA17, and the latter with SCA48 and SCAR16 (autosomal recessive). In SCA17, most patients carry intermediate TBP_41 - 49 alleles but show incomplete penetrance, and the missing heritability can be explained by a new entity whereby TBP_41 - 49 requires the STUB1 variant to be symptomatic. The STUB1 gene encodes the chaperone-associated E3 ubiquitin ligase (CHIP) involved in ubiquitin-mediated proteasomal control of protein homeostasis. However, reports of the neuropathology are limited and role of STUB1 mutations in SCA17-DI remain unknown. Here we report the clinicopathologic features of identical twin siblings, one of whom was autopsied and was found to carry an intermediate allele (41 and 38 CAG/CAA repeats) in TBP and a heterozygous missense mutation in STUB1 (p.P243L). These patients developed autosomal recessive Huntington's disease-like symptoms. Brain MRI showed diffuse atrophy of the cerebellum and T2WI revealed hyperintense lesions in the basal ganglia and periventricular deep white matter. The brain histopathology of the patient shared features characteristic of SCA17, such as degeneration of the cerebellar cortex and caudate nucleus, and presence of 1C2-positive neurons. Here we show that mutant CHIP fails to generate the polyubiquitin chain due to disrupted folding of the entire U box domain, thereby affecting the E3 activity of CHIP. When encountering patients with cerebellar ataxia, especially those with Huntington's disease-like symptoms, genetic testing for STUB1 as well as TBP should be conducted for diagnosis of SCA17-DI, even in cases of sporadic or autosomal recessive inheritance.

Temporal Profiles of Symptom Scores After Palliative Radiotherapy for Bleeding Gastric Cancer With Adjustment for the Palliative Prognostic Index: An Exploratory Analysis of a Multicentre Prospective Observational Study (JROSG 17-3)

AIMS

Although palliative radiotherapy for gastric cancer may improve some symptoms, it may also have a negative impact due to its toxicity. We investigated whether symptoms improved after radiotherapy with adjustment for the Palliative Prognostic Index (PPI) considering that patients with limited survival tend to experience deterioration of symptoms.

MATERIALS AND METHODS

This study was an exploratory analysis of the Japanese Radiation Oncology Study Group study (JROSG 17-3). We assessed six symptom scores (nausea, anorexia, fatigue, shortness of breath, pain at the irradiated area and distress) at registration and 2, 4 and 8 weeks thereafter. We tested whether symptoms linearly improved after adjusting for the baseline PPI. Shared parameter models were used to adjust for potential bias in missing data.

RESULTS

The present study analysed all 55 patients enrolled in JROSG 17-3. With time from registration as the only explanatory variable in the model, a significant linear decrease was observed in shortness of breath, pain and distress (slopes, -0.26, -0.22 and -0.19, respectively). Given that the interaction terms (i.e. PPI × time) were not significantly associated with symptom scores in any of the six symptoms, only PPI was included as the main effect in the final multivariable models. After adjusting for the PPI, shortness of breath, pain and distress significantly improved (slope, -0.25, -0.19 and -0.17; P < 0.001, 0.002 and 0.047, respectively). An improvement in fatigue and distress was observed only in patients treated with a biologically effective dose ≤14.4 Gy.

CONCLUSION

Shortness of breath, pain and distress improved after radiotherapy. Moreover, a higher PPI was significantly associated with higher symptom scores at all time points, including baseline. In contrast, PPI did not seem to influence the improvement of these symptoms. Regardless of the expected survival, patients receiving radiotherapy for gastric cancer can expect an improvement in shortness of breath, pain and distress over 8 weeks. Multiple-fraction radiotherapy might hamper the improvement in fatigue and distress by its toxicity or treatment burden.

Refinements in the reconstruction of bisphosphonate-related osteonecrosis of the jaw

The recommended treatment strategy for stage 3 bisphosphonate-related osteonecrosis of the jaw (BRONJ) is currently rigid plate fixation without bone reconstruction. However, a recent systematic review indicated the utility of microsurgical reconstruction after resection of BRONJ. Several types of flaps have been described but their applications are controversial. Here we present a detailed reconstruction plan for obtaining better outcomes in patients with maxillary and mandibular BRONJ. Given that progressive maxillary BRONJ is often invasive to the skin, including the eyelid, leading to functional loss such as leakage of discharge and ectropion, several revision surgeries are needed to increase the volume in the defect after the free flap transfer. For progressive mandibular BRONJ, hemi-mandibulectomy to subtotal mandibulectomy with an adequate margin from the necrotic bone is necessary, followed by a well-designed fibular free flap.

Lattice-patterned collagen fibers and their dynamics in axolotl skin regeneration

The morphology of collagen-producing cells and the structure of produced collagen in the dermis have not been well-described. This lack of insights has been a serious obstacle in the evaluation of skin regeneration. We succeeded in visualizing collagen-producing cells and produced collagen using the axolotl skin, which is highly transparent. The visualized dermal collagen had a lattice-like structure. The collagen-producing fibroblasts consistently possessed the lattice-patterned filopodia along with the lattice-patterned collagen network. The dynamics of this lattice-like structure were also verified in the skin regeneration process of axolotls, and it was found that the correct lattice-like structure was not reorganized after simple skin wounding but was reorganized in the presence of nerves. These findings are not only fundamental insights in dermatology but also valuable insights into the mechanism of skin regeneration.

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Dermal collagen synthesized by a single cell was visualized in the axolotl skin

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Collagen-synthetic cells were visualized and revealed lattice-patterned filopodia

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Collagen pattern was deformed after simple skin wounding

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The lattice-patterned collagen was only restorable in the presence of nerves

An approach for elucidating dermal fibroblast dedifferentiation in amphibian limb regeneration

Urodele amphibians, Pleurodeles waltl and Ambystoma mexicanum, have organ-level regeneration capability, such as limb regeneration. Multipotent cells are induced by an endogenous mechanism in amphibian limb regeneration. It is well known that dermal fibroblasts receive regenerative signals and turn into multipotent cells, called blastema cells. However, the induction mechanism of the blastema cells from matured dermal cells was unknown. We previously found that BMP2, FGF2, and FGF8 (B2FF) could play sufficient roles in blastema induction in urodele amphibians. Here, we show that B2FF treatment can induce dermis-derived cells that can participate in multiple cell lineage in limb regeneration. We first established a newt dermis-derived cell line and confirmed that B2FF treatment on the newt cells provided plasticity in cellular differentiation in limb regeneration. To clarify the factors that can provide the plasticity in differentiation, we performed the interspecies comparative analysis between newt cells and mouse cells and found the Pde4b gene was upregulated by B2FF treatment only in the newt cells. Blocking PDE4B signaling by a chemical PDE4 inhibitor suppressed dermis-to-cartilage transformation and the mosaic knockout animals showed consistent results. Our results are a valuable insight into how dermal fibroblasts acquire multipotency during the early phase of limb regeneration via an endogenous program in amphibian limb regeneration.

Lmx1b activation in axolotl limb regeneration

BACKGROUND

Axolotls can regenerate their limbs. In their limb regeneration process, developmental genes are re-expressed and reorganize the developmental axes, in which the position-specific genes are properly re-expressed. However, how such position specificity is reorganized in the regeneration processes has not been clarified. To address this issue, we focused on the reactivation process of Lmx1b, which determines the limb dorsal identity in many animals.

RESULTS

Here, we show that Lmx1b expression is maintained in the dorsal skin before amputation and is activated after amputation. Furthermore, we demonstrate that only cells located in the dorsal side prior to limb amputation could reactivate Lmx1b after limb amputation. We also found that Lmx1b activation was achieved by nerve presence. The nerve factors, BMP2 + FGF2 + FGF8 (B2FF), consistently reactivate Lmx1b when applied to the dorsal skin.

CONCLUSIONS

These results imply that the retained Lmx1b expression in the intact skin plays a role in positional memory, which instruct cells about the spatial positioning before amputation. This memory is reactivated by nerves or nerve factors that can trigger the entire limb regeneration process. Our findings highlight the role of nerves in amphibian limb regeneration, including both the initiation of limb regeneration and the reactivation of position-specific gene expression. This article is protected by copyright. All rights reserved.

Fibrillation cycle length predicts cardiovascular events in patients with long-standing persistent atrial fibrillation

BACKGROUND

Atrial fibrillation (AF) is associated with an increased risk of heart failure (HF), stroke, and death. Although fibrillation cycle length (FCL) is used as a surrogate for atrial refractoriness, its impact on outcomes remains unclear. This study aimed to identify predictors of cardiovascular events, including FCL, in patients with long-standing persistent AF.

METHODS

The study included 190 consecutive patients with long-standing persistent AF (mean age 74 years, 74% male). Patients with valvular AF or hemodialysis-dependent end-stage renal disease and those on anti-arrhythmic drugs were excluded. The primary composite outcome was occurrence of cardiovascular events (myocardial infarction, HF), cerebrovascular events (stroke, transient ischemic attack), and all-cause death. FCL was calculated by fast Fourier transformation analysis of fibrillation waves in the surface electrocardiogram.

RESULTS

Over a median follow-up of 2.6 years, the primary outcome occurred in 31 patients (cardiovascular events, n = 18; cerebrovascular events, n = 8; all-cause death, n = 5). In multivariate analysis, longer FCL and history of HF were independent predictors of these outcomes. In a Cox proportional hazards model adjusted for age, sex, and history of HF, patients with an FCL > 160 ms (cut-off determined by receiver-operating characteristic curve analysis) were at increased risk of the outcome (hazard ratio 12.9; 95% confidence interval 4.99-44.10; p < 0.001).

CONCLUSIONS

FCL was independently associated with cardiovascular outcomes in patients with long-standing persistent AF.

Nerve-mediated FGF-signaling in the early phase of various organ regeneration

Amphibians have a very high capacity for regeneration among tetrapods. This superior regeneration capability in amphibians can be observed in limbs, the tail, teeth, external gills, the heart, and some internal organs. The mechanisms underlying the superior organ regeneration capability have been studied for a long time. Limb regeneration has been investigated as the representative phenomenon for organ-level regeneration. In limb regeneration, a prominent difference between regenerative and nonregenerative animals after limb amputation is blastema formation. A regeneration blastema requires the presence of nerves in the stump region. Thus, nerve regulation is responsible for blastema induction, and it has received much attention. Nerve regulation in regeneration has been investigated using the limb regeneration model and newly established alternative experimental model called the accessory limb model. Previous studies have identified some candidate genes that act as neural factors in limb regeneration, and these studies also clarified related events in early limb regeneration. Consistent with the nervous regulation and related events in limb regeneration, similar regeneration mechanisms in other organs have been discovered. This review especially focuses on the role of nerve-mediated fibroblast growth factor in the initiation phase of organ regeneration. Comparison of the initiation mechanisms for regeneration in various amphibian organs allows speculation about a fundamental regenerative process.

Clinical study of treatment methods and associated factors in mandibular osteoradionecrosis

This study aimed to determine the appropriate treatment methods and evaluate associated factors by comparing nonoperative treatment alone with a combination of both nonoperative and surgical treatment in 34 patients with mandibular osteoradionecrosis (mORN). The associated cure factors were analyzed by Cox regression. Propensity scores were calculated from factors that were not significant in the univariate analysis and used as covariates in the multivariate analysis. The cure rate among patients who received nonoperative and surgical treatment was higher than that observed with nonoperative treatment alone. Only the treatment method was associated with cure in both univariate and multivariate analyses.

Intentional Supernumerary Motor Phantom Limb after Right Cerebral Stroke: A Case Report

A 47-year-old right-handed man was admitted to our hospital for rehabilitation after right basal ganglion hematoma. On day 57, he noticed a supernumerary motor phantom limb (SPL) involving his right arm, originating at the level of the elbow. The most notable finding of his SPL was the motor characteristic. When the subject had the intention to move the upper paralyzed limb simultaneously with the trainer's facilitating action, he said "there is another arm." The intention to move the paralyzed arm alone or passive movement of the paralyzed arm did not induce the SPL. He showed a severe left sensorimotor impairment and mild hemineglect, but no neglect syndromes of the body (e.g., asomatognosia, somatoparaphrenia, personification and misoplegia, or anosognosia) were observed. Brain MRI demonstrated a hematoma in the right temporal lobe subcortex, subfrontal cortex, putamen, internal capsule, and thalamus. Single-photon emission computed tomography images showed more widespread hypoperfusion in the right hemisphere in comparison to the lesions on MRI. However, the premotor cortex was preserved. Our case is different from Staub's case in that SPL was not induced by the intention to move the paralyzed limb alone; rather, it was induced when the patient intended to move the paralyzed limb with a trainer's simultaneous facilitating action. The SPL may reflect that an abnormal closed-loop function of the thalamocortical system underlies the phantom phenomenon. However, despite the severe motor and sensory impairment, the afferent pathway from the periphery to the premotor cortex may have been partially preserved, and this may have been related to the induction of SPL.

Canagliflozin Suppresses Atrial Remodeling in a Canine Atrial Fibrillation Model

Background

Recent clinical trials have demonstrated the possible pleiotropic effects of SGLT2 (sodium–glucose cotransporter 2) inhibitors in clinical cardiovascular diseases. Atrial electrical and structural remodeling is important as an atrial fibrillation (AF) substrate.

Methods and Results

The present study assessed the effect of canagliflozin (CAN), an SGLT2 inhibitor, on atrial remodeling in a canine AF model. The study included 12 beagle dogs, with 10 receiving continuous rapid atrial pacing and 2 acting as the nonpacing group. The 10 dogs that received continuous rapid atrial pacing for 3 weeks were subdivided as follows: pacing control group (n=5) and pacing+CAN (3 mg/kg per day) group (n=5). The atrial effective refractory period, conduction velocity, and AF inducibility were evaluated weekly through atrial epicardial wires. After the protocol, atrial tissues were sampled for histological examination. The degree of reactive oxygen species expression was evaluated by dihydroethidium staining. The atrial effective refractory period reduction was smaller (P=0.06) and the degree of conduction velocity decrease was smaller in the pacing+CAN group compared with the pacing control group (P=0.009). The AF inducibility gradually increased in the pacing control group, but such an increase was suppressed in the pacing+CAN group (P=0.011). The pacing control group exhibited interstitial fibrosis and enhanced oxidative stress, which were suppressed in the pacing+CAN group.

Conclusions

CAN and possibly other SGLT2 inhibitors might be useful for preventing AF and suppressing the promotion of atrial remodeling as an AF substrate.

Acute heart failure due to large intimal flap associated with chronic aortic dissection

Acute heart failure from aortic stenosis secondary to chronic aortic dissection is very rare. We describe a case of acute heart failure secondary to aortic arch stenosis resulting from subacute type A aortic dissection. Resection of large thickened immobile intimal flap with total aortic arch replacement was successful, and cardiac function improved.

Neural regulation in tooth regeneration of Ambystoma mexicanum

The presence of nerves is an important factor in successful organ regeneration in amphibians. The Mexican salamander, Ambystoma mexicanum, is able to regenerate limbs, tail, and gills when nerves are present. However, the nerve-dependency of tooth regeneration has not been evaluated. Here, we reevaluated tooth regeneration processes in axolotls using a three-dimensional reconstitution method called CoMBI and found that tooth regeneration is nerve-dependent although the dentary bone is independent of nerve presence. The induction and invagination of the dental lamina were delayed by denervation. Exogenous Fgf2, Fgf8, and Bmp7 expression could induce tooth placodes even in the denervated mandible. Our results suggest that the role of nerves is conserved and that Fgf+Bmp signals play key roles in axolotl organ-level regeneration. The presence of nerves is an important factor in successful organ regeneration in amphibians. The Mexican salamander, Ambystoma mexicanum, is able to regenerate limbs, tail, and gills when nerves are present. However, the nervedependency of tooth regeneration has not been evaluated. Here, we reevaluated tooth regeneration processes in axolotls using a three-dimensional reconstitution method called CoMBI and found that tooth regeneration is nerve-dependent although the dentary bone is independent of nerve presence. The induction and invagination of the dental lamina were delayed by denervation. Exogenous Fgf2, Fgf8, and Bmp7 expression could induce tooth placodes even in the denervated mandible. Our results suggest that the role of nerves is conserved and that Fgf+Bmp signals play key roles in axolotl organ-level regeneration.

Unveiling the Dynamical Assembly of Magnetic Nanocrystal Zig-Zag Chains via In Situ TEM Imaging in Liquid

The controlled assembly of colloidal magnetic nanocrystals is key to many applications such as nanoelectronics, storage memory devices, and nanomedicine. Here, the motion and ordering of ferrimagnetic nanocubes in water via liquid-cell transmission electron microscopy is directly imaged in situ. Through the experimental analysis, combined with molecular dynamics simulations and theoretical considerations, it is shown that the presence of highly competitive interactions leads to the formation of stable monomers and dimers, acting as nuclei, followed by a dynamic growth of zig-zag chain-like assemblies. It is demonstrated that such arrays can be explained by first, a maximization of short-range electrostatic interactions, which at a later stage become surpassed by magnetic forces acting through the easy magnetic axes of the nanocubes, causing their tilted orientation within the arrays. Moreover, in the confined volume of liquid in the experiments, interactions of the nanocube surfaces with the cell membranes, when irradiated at relatively low electron dose, slow down the kinetics of their self-assembly, facilitating the identification of different stages in the process. The study provides crucial insights for the formation of unconventional linear arrays made of ferrimagnetic nanocubes that are essential for their further exploitation in, for example, magnetic hyperthermia, magneto-transport devices, and nanotheranostic tools.

The low carriage prevalence of pneumococcus among community-dwelling older people: A cross-sectional study in Japan

BACKGROUND

The carriage prevalence of pneumococcus among community-dwelling older adults is not fully understood, especially in superaged societies. Our purpose was to elucidate the carriage prevalence of pneumococcus in the upper respiratory tract among Japanese community-dwelling adults aged ≥65 years.

METHODS

We conducted a cross-sectional study of generally healthy community-dwelling adults aged ≥65 years in Nagasaki city, Japan. Demographic and clinical data and nasopharyngeal, oropharyngeal and saliva samples were collected from February 21st, 2018, to December 17th, 2018. The specimens were tested by culture and molecular methods.

RESULTS

Among a total of 504 enrolled participants, none were positive for pneumococcus by culture, and 22 were positive by PCR. The overall carriage prevalence was 4.4% (95% CI: 2.8-6.5%). The prevalence was highest in saliva samples, followed by oropharyngeal and nasopharyngeal samples. No demographic characteristics were associated with carriage prevalence, including age (4.7% among participants aged 65-74 years and 4.1% among those 75 years and older). Among the pneumococcal-positive participants, 18.2% were PCV13-covered serotypes.

CONCLUSIONS

Our data suggest a low carriage prevalence of S. pneumoniae among community-dwelling older people in Japan.

Wearable Cardioverter Defibrillator - Initial Experience in the Outpatient Setting in Japan

Background: The wearable cardioverter defibrillator (WCD) has been available since 2014 in Japan, and its benefit in the in-hospital acute phase at high risk of ventricular tachyarrhythmia (VTA) has been established, but its clinical use in the outpatient setting remains unclear, especially in Japan.

Methods and Results: The subjects consisted of 43 consecutive patients with WCD use in the outpatient setting from April 2014 to October 2019 at the present institute. Event alerts and wearing compliance were checked via the remote monitoring system, and a dedicated WCD training team contacted the patients if necessary. The median observation period was 51 days (IQR, 37–68 days) and the median daily wearing time was 23.1 h/day (IQR, 22.0–23.6 h/day). WCD was prescribed for primary prevention of VTA in 7 patients (16%), and for secondary prevention in 36 (84%). The common reason for WCD use was preventive therapy and/or clinical observation. Two appropriate and one inappropriate shock were observed. Eleven patients were not indicated for ICD because of successful catheter ablation optimal medical therapy, VTA in early onset of heart disease and refusal. The remaining 32 patients, however, underwent ICD implantation.

Conclusions: In the present real-world study, the WCD wearing compliance was well-maintained in the outpatient setting. WCD is useful for patients at high risk of VTA.

Real-World Antithrombotic Therapy in Atrial Fibrillation Patients with a History of Percutaneous Coronary Intervention

Optimal antithrombotic strategy for atrial fibrillation (AF) patients with a history of percutaneous coronary intervention (PCI) has been under debate. The actual prescription trend of antithrombotic therapy for these patients remains unclear, especially in chronic phase.Patients with AF having at least a 1-year history of PCI were retrospectively evaluated in 2010, 2012, 2014, and 2016. A total of 266 patients were finally enrolled in this study. The proportion of patients prescribed with oral anticoagulants (OACs) gradually increased over the study period (56%, 67%, 73%, and 74% in 2010, 2012, 2014, and 2016, respectively). According to the type of OACs, the proportion of direct oral anticoagulant (DOAC), launched in 2011, increased compared with warfarin (DOAC versus warfarin = 3% versus 64% in 2012, 24% versus 49% in 2014, and 32% versus 42% in 2016). Single antiplatelet therapy (SAPT) with OAC was the most popular prescription every year, and its proportion increased over the study period (41%, 44%, 55%, and 59%, respectively). The proportion of OAC monotherapy gradually increased (2%, 3%, 8%, and 9%, respectively), whereas that of triple therapy, i.e., dual antiplatelet therapy with OAC, gradually decreased (14%, 22%, 8%, and 5% in 2010, 2012, 2014, and 2016, respectively).Antithrombotic therapy trends for AF patients with a history of PCI were changing every year. The prescription rate of triple therapy gradually decreased, in contrast, that of OAC monotherapy gradually increased from 2010 to 2016. However, the evidence for OAC monotherapy in these patients remains insufficient.

Stability and plasticity of positional memory during limb regeneration in Ambystoma mexicanum

BACKGROUND

Urodele amphibians are capable of regenerating their organs after severe damage. During such regeneration, participating cells are given differentiation instructions by the surrounding cells. Limb regeneration has been investigated as a representative phenomenon of organ regeneration. Cells known as blastema cells are induced after limb amputation. In this process, dermal fibroblasts are dedifferentiated and become undifferentiated similar to limb bud cells. Just like limb bud cells, the induced blastema cells are positioned along the three limb developmental axes: the dorsoventral, the anteroposterior, and the proximodistal. The accurate developmental axes are essential for reforming the structures correctly. Despite the importance of the developmental axes, the relationship between the newly establishing developmental axes and existing limb axes was not well described with molecular markers.

RESULTS

In this study, we grafted skin from GFP-transgenic axolotls and traced the cell lineage with position-specific gene expressions in order to investigate the correlation of the newly established axes and cellular origin. Shh- and Lmx1b-expressing cells emerged from the posterior skin and dorsal skin, respectively, even though the skin was transplanted to an inconsistent position. Shox2, a posterior marker gene, could be activated in cells derived from distal skin.

CONCLUSIONS

Our results suggest that the location memories on anteroposterior and dorsoventral axes are relatively stable in a regenerating blastema though cellular differentiation is reprogrammed.

Use of idarucizumab for dabigatran reversal in cardiac tamponade during atrial fibrillation ablation: A case report

It is known that the efficacy of catheter ablation for atrial fibrillation (AF) is high, but cardiac tamponade may occur in 1–2% cases. Even in such cases, fatal condition can be avoided by appropriate drainage, but reversal of anticoagulation therapy might also be necessary. Here, we report a case of use of idarucizumab for cardiac tamponade during AF ablation. Although the drainage with pericardial centesis should be selected, we could not perform because echo free space was too thin at least at the precordial or apical side of the ventricle. Fortunately, dabigatran reversal by idarucizumab suppressed cardiac tamponade progress and the patient recovered without undergoing any invasive procedures. The pericardial drainage must be the principal therapy for cardiac tamponade, but reversal of anticoagulant might be helpful for patients’ recovery. It might be thought that dabigatran, the only direct oral anticoagulant with a specific reversal agent, should be the safest choice in case of risk for bleeding complications such as AF ablation.

<Learning objective: Cardiac tamponade is one of the complications of catheter ablation for atrial fibrillation (AF). In such cases, fatal condition can be avoided by appropriate drainage, but reversal of anticoagulation therapy might be necessary. Drainage with pericardial centesis was not selected because echo free space was too thin. Dabigatran reversal by idarucizumab suppressed cardiac tamponade progress. It was thought that dabigatran would be the safest choice in case of bleeding complications during AF ablation.>

Nerve roles in blastema induction and pattern formation in limb regeneration

Compared to amniotes, amphibians are widely known to be great healers. Urodele amphibians in particular have tremendous regeneration abilities, and can even regenerate organs, such as the brain, the heart and the limbs. Limb regeneration, in particular, has been investigated since it is representative of their superior regeneration abilities, and the presence of nerves has been examined in detail because they play essential roles in limb regeneration. Without nerves, there is no regeneration. Recent research has succeeded in outlining nerve regulation in the early phases, namely, the blastema induction phase. Based on the results of a few classic studies, it was believed that nerves played minimal roles in the later phases. In the present review, we first summarize the recent insights into the roles of nerves in blastema formation, and in the later stages, pattern formation becomes the focus. Pattern formation in limb regeneration has been interpreted in an intercalary manner. Recent findings point to the participation of nerves in the intercalary regulation of limb regeneration. This may change the current thinking on the effects of nerves on pattern formation in limb regeneration. Although the importance of nerves in amphibian limb regeneration has been recognized, the extent of their importance has remained unclear since the nerve entities were undetermined. This ambiguity was a large obstacle to investigating and comparing regeneration abilities in other species. Recent insights into nerves in limb regeneration may help overcome this obstacle and lead to future advancements.

Linagliptin Suppresses Electrical and Structural Remodeling in the Isoproterenol Induced Myocardial Injury Model

The effect of DPP-4 inhibitor on the electrical and structural remodeling in myocardial injury has not been evaluated. We hypothesized that linagliptin, DPP-4 inhibitor, suppresses myocardial remodeling in the isoproterenol (ISP)-induced myocardial injury model.Sprague-Dawley rats were assigned to 3 groups: 1) sham group, 2) ISP group (subcutaneous ISP injection of 70 mg/kg), and 3) ISP + linagliptin (ISP + Lin) (5 mg/kg/day, p.o.) group. Serum was sampled on day 1 (acute phase) and day 7 (sub-acute phase) to evaluate derivatives of reactive oxidative metabolites (d-ROMs). The electrophysiological study was performed in sub-acute phase for the evaluation of the ventricular effective refractory period (VERP) and monophasic action potential duration (MAPD). The VERP and MAPD were markedly prolonged in the ISP group in comparison with the sham (MAPD20: 14 ± 6 versus 11 ± 3 ms, MAPD90: 57 ± 8 versus 44 ± 7 ms, VERP: 74 ± 22 versus 38 ± 10 ms, P < 0.05). In contrast in the ISP + Lin group, such prolongations were suppressed, and the parameters were shorter than the ISP group (MAPD20: 9 ± 2 ms, MAPD90: 35 ± 6 ms, VERP: 52 ± 13 ms, P < 0.05). ISP treatment induced myocardial injury. The injured area was reduced in the ISP + Lin group in comparison with the ISP group (P < 0.05). Serum d-ROMs level in acute phase was higher in ISP group than the other 2 groups (sham: 214 ± 55 versus ISP: 404 ± 45 versus ISP + Lin: 337 ± 20 U.CARR, P < 0.05).Linagliptin suppressed structural and electrical changes, possibly through the antioxidative effect, in this myocardial injury model.

Antiremodeling Effect of Xanthine Oxidase Inhibition in a Canine Model of Atrial Fibrillation

In a canine rapid atrial stimulation model of atrial fibrillation (AF), we have demonstrated an increased production of reactive oxygen species (ROS) along with electrical and structural remodeling. In the present study, we hypothesized that antioxidants can suppress atrial remodeling canines with AF. We therefore evaluated the effect of febuxostat, a xanthine oxidase (XO) inhibitor and a pure antioxidant, on atrial remodeling.AF was produced by performing a 3-week rapid atrial pacing (400 bpm) in 13 dogs divided into three groups: pacing + febuxostat group (n = 5; atrial pacing with 50 mg/day of febuxostat (administration); pacing control group (n = 5; atrial pacing without any drug administration); and non-pacing group (n = 3). Electrophysiological studies were conducted in the first 2 groups every week. Atrial tissue fibrosis was evaluated by Azan and immunofluorescent staining of fibronectin. Oxidative stress was evaluated by DHE and FCF-DA staining.Shortening of the refractory period and increase in AF inducibility appeared gradually in the pacing control group, but such changes were suppressed in the pacing + febuxostat group (P = 0.05). The pacing control group showed increase in fibrosis, which was suppressed in the febuxostat group. In DHE and DCF-DA staining, the pacing control group showed an increase in oxidative stress, which was suppressed in the pacing + febuxostat group. The pacing control group exhibited fibronectin expression, which was suppressed in the pacing + febuxostat group.The antioxidant effect of febuxostat may achieve an inhibition of new-onset AF in canines.