Immunity in salamander regeneration: Where are we standing and where are we headed?

Salamanders exhibit the most extensive regenerative repertoire among vertebrates, being able to accomplish scar-free healing and faithful regeneration of significant parts of the eye, heart, brain, spinal cord, jaws and gills, as well as entire appendages throughout life. The cellular and molecular mechanisms underlying salamander regeneration are currently under extensive examination, with the hope of identifying the key drivers in each context, understanding interspecies differences in regenerative capacity, and harnessing this knowledge in therapeutic settings. The immune system has recently emerged as a potentially critical player in regenerative responses. Components of both innate and adaptive immunity have been found at critical stages of regeneration in a range of salamander tissues. Moreover, functional studies have identified a requirement for macrophages during heart and limb regeneration. However, our knowledge of salamander immunity remains scarce, and a thorough definition of the precise roles played by its members is lacking. Here, we examine the evidence supporting roles for immunity in various salamander regeneration models. We pinpoint observations that need revisiting through modern genetic approaches, uncover knowledge gaps, and highlight insights from various model organisms that could guide future explorations toward an understanding of the functions of immunity in regeneration.

Generation of a novel model of primary human cell senescence through Tenovin-6 mediated inhibition of sirtuins.

Cell senescence, a state of cell cycle arrest and altered metabolism with enhanced pro-inflammatory secretion, underlies at least some aspects of organismal ageing. The sirtuin family of deacetylases has been implicated in preventing premature ageing; sirtuin overexpression or resveratrol-mediated activation of sirtuins increase longevity. Here we show that sirtuin inhibition by short-term, low-dose treatment with the experimental anti-cancer agent Tenovin-6 (TnV6) induces cellular senescence in primary human fibroblasts. Treated cells cease proliferation and arrest in G1 of the cell cycle, with elevated p21 levels, DNA damage foci, high mitochondrial and lysosomal load and increased senescence-associated ß galactosidase activity, together with actin stress fibres and secretion of IL-6 (indicative of SASP upregulation). Consistent with a histone deacetylation role of SIRT1, we find nuclear enlargement, possibly resulting from chromatin decompaction on sirtuin inhibition. These findings highlight TnV6 as a drug that may be useful in clinical settings where acute induction of cell senescence would be beneficial, but also provide the caveat that even supposedly non-genotoxic anticancer drugs can have unexpected and efficacy-limiting impacts on non-transformed cells.

Focused Ultrasound and Other Lesioning Therapies in Movement Disorders.

PURPOSE OF REVIEW: Lesioning therapies have been some of the earliest, most effective surgical treatments in movement disorders. This review summarizes recent studies, emerging modalities, and trends in lesioning procedures for movement disorders. RECENT FINDINGS: Magnetic resonance-guided high-intensity focused ultrasound (MRgFUS) is the newest incisionless technology for lesioning procedures in movement disorders. It has recent FDA approval for thalamotomy in essential tremor and tremor-dominant Parkinson disease. There are current studies exploring subthalamotomy and pallidotomy in PD. Gamma knife is another incisionless modality that has been studied for decades and remains an effective treatment, albeit with less recent studies and more risks for adverse events, in movement disorders. Radiofrequency lesioning remains an efficacious treatment, particularly for unilateral pallidotomy in PD, but has fallen out of favor compared with other modalities, particularly MRgFUS. Lesioning therapies in movement disorders have shown efficacy in treating a variety of movement disorders. Enthusiasm for their use has waned with the advent of deep brain stimulation. The recent development of MRgFUS has recentered attention on lesioning therapy and its potential. Patient preference and access to care will remain determinants in the use of lesioning therapy as more data are being collected on the long-term benefit and safety.

Association of twins' sex discordance and age at menarche.

INTRODUCTION: Age at menarche (AAM) is the point in development when the female starts her first menstrual period and is one of the first milestones in female reproductive life. A combination of genetic and environmental factors plays a role in the timing of female's age at menarche. MATERIAL AND METHODS: This study's purpose was to investigate the association between the biological sex of the co-twin and the age at menarche experienced by the female twin. Females from pairs of female-female twins (n = 12,176) and female-male twins (n = 2286) were collected through the Washington State Twin Registry. RESULTS: Environmental and genetic analyses were conducted. There was no significant difference between females with female twins and females with male twins regarding early, late or normal age at menarche (P = 0.87). However, the adjusted odds of early menarche among females with female twins were 35% lower than females with male co-twins (0.65, 95% CI 0.50-0.83). When using Falconer's formula, an estimated heritability of 0.81 was found with shared (21.8%) and non-shared (40.8%) environmental factors contributing to the age at menarche. CONCLUSION: Having a male twin during fetal life as a co-twin does not change the age of menarche in future life, although female-female twins have lower age of menarche compared to females from female-male pair. Both genetic and environmental factors determine the age of menarche.

mTORC Inhibitors as Broad-Spectrum Therapeutics for Age-Related Diseases.

Chronological age represents the greatest risk factor for many life-threatening diseases, including neurodegeneration, cancer, and cardiovascular disease; ageing also increases susceptibility to infectious disease. Current efforts to tackle individual diseases may have little impact on the overall healthspan of older individuals, who would still be vulnerable to other age-related pathologies. However, recent progress in ageing research has highlighted the accumulation of senescent cells with chronological age as a probable underlying cause of pathological ageing. Cellular senescence is an essentially irreversible proliferation arrest mechanism that has important roles in development, wound healing, and preventing cancer, but it may limit tissue function and cause widespread inflammation with age. The serine/threonine kinase mTOR (mechanistic target of rapamycin) is a regulatory nexus that is heavily implicated in both ageing and senescence. Excitingly, a growing body of research has highlighted rapamycin and other mTOR inhibitors as promising treatments for a broad spectrum of age-related pathologies, including neurodegeneration, cancer, immunosenescence, osteoporosis, rheumatoid arthritis, age-related blindness, diabetic nephropathy, muscular dystrophy, and cardiovascular disease. In this review, we assess the use of mTOR inhibitors to treat age-related pathologies, discuss possible molecular mechanisms of action where evidence is available, and consider strategies to minimize undesirable side effects. We also emphasize the urgent need for reliable, non-invasive biomarkers of senescence and biological ageing to better monitor the efficacy of any healthy ageing therapy.

Induction and Characterization of Cellular Senescence in Salamanders.

Cellular senescence is a permanent proliferation arrest mechanism induced following the detection of genotoxic stress. Mounting evidence has causally linked the accumulation of senescent cells to a growing number of age-related pathologies in mammals. However, recent data have also highlighted senescent cells as important mediators of tissue remodeling during organismal development, tissue repair, and regeneration. As powerful model organisms for studying such processes, salamanders constitute a system in which to probe the characteristics, physiological functions, and evolutionary facets of cellular senescence. In this chapter, we outline methods for the generation, identification, and characterization of salamander senescent cells in vitro and in vivo.

Senescent cells enhance newt limb regeneration by promoting muscle dedifferentiation.

Salamanders are able to regenerate their entire limbs throughout lifespan, through a process that involves significant modulation of cellular plasticity. Limb regeneration is accompanied by the endogenous induction of cellular senescence, a state of irreversible cell cycle arrest associated with profound non-cell-autonomous consequences. While traditionally associated with detrimental physiological effects, here, we show that senescent cells can enhance newt limb regeneration. Through a lineage tracing approach, we demonstrate that exogenously derived senescent cells promote dedifferentiation of mature muscle tissue to generate regenerative progenitors. In a paradigm of newt myotube dedifferentiation, we uncover that senescent cells promote myotube cell cycle re-entry and reversal of muscle identity via secreted factors. Transcriptomic profiling and loss of function approaches identify the FGF-ERK signalling axis as a critical mediator of senescence-induced muscle dedifferentiation. While chronic senescence constrains muscle regeneration in physiological mammalian contexts, we thus highlight a beneficial role for cellular senescence as an important modulator of dedifferentiation, a key mechanism for regeneration of complex structures.

Obatoclax Rescues FUS-ALS Phenotypes in iPSC-Derived Neurons by Inducing Autophagy.

Aging is associated with the disruption of protein homeostasis and causally contributes to multiple diseases, including amyotrophic lateral sclerosis (ALS). One strategy for restoring protein homeostasis and protecting neurons against age-dependent diseases such as ALS is to de-repress autophagy. BECN1 is a master regulator of autophagy; however, is repressed by BCL2 via a BH3 domain-mediated interaction. We used an induced pluripotent stem cell model of ALS caused by mutant FUS to identify a small molecule BH3 mimetic that disrupts the BECN1-BCL2 interaction. We identified obatoclax as a brain-penetrant drug candidate that rescued neurons at nanomolar concentrations by reducing cytoplasmic FUS levels, restoring protein homeostasis, and reducing degeneration. Proteomics data suggest that obatoclax protects neurons via multiple mechanisms. Thus, obatoclax is a candidate for repurposing as a possible ALS therapeutic and, potentially, for other age-associated disorders linked to defects in protein homeostasis.

Cellular senescence promotes progenitor cell expansion during axolotl limb regeneration.

Axolotl limb regeneration is accompanied by the transient induction of cellular senescence within the blastema, the structure that nucleates regeneration. The precise role of this blastemal senescent cell (bSC) population, however, remains unknown. Here, through a combination of gain- and loss-of-function assays, we elucidate the functions and molecular features of cellular senescence in vivo. We demonstrate that cellular senescence plays a positive role during axolotl regeneration by creating a pro-proliferative niche that supports progenitor cell expansion and blastema outgrowth. Senescent cells impact their microenvironment via Wnt pathway modulation. Further, we identify a link between Wnt signaling and senescence induction and propose that bSC-derived Wnt signals facilitate the proliferation of neighboring cells in part by preventing their induction into senescence. This work defines the roles of cellular senescence in the regeneration of complex structures.

The Power of Access in Parkinson's Disease Care: A Retrospective Review of Telehealth Uptake During the COVID-19 Pandemic.

Objective: The onset of the COVID-19 pandemic in March of 2020 forced a rapid pivot to telehealth and compelled a use-case experiment in specialty telehealth neurology movement disorders care. The aims of this study were to quantify the potential benefit of telehealth as an option to the Parkinson's disease community as shown by the first 9 months of the COVID-19 pandemic, and to quantify the potential impact of the absence of a deep brain stimulation (DBS) telehealth option on DBS patient follow-up. Methods: New patient visits to the Inova Parkinson's and Movement Disorder's Center from April to December 2020 (9 months) were retrospectively reviewed for telehealth vs. in-person, demographics (age, gender, race, primary insurance), chief complaint, prior movement disorders specialist (MDS) consultation, imaging tests ordered, and distance/travel time from primary zip code to clinic. Additionally, DBS programming visit volume from April to December 2020 was compared to DBS programming visit volume from April to December 2019. Results: Of the 1,097 new patients seen, 85% were via telehealth (N = 932) and 15% in person (N = 165). In the telehealth cohort, 97.75% had not consulted with an MDS before (N = 911), vs. 87.9% of in-person (N = 145). Age range was 61.8 +/- 17.9 years (telehealth), 68.8 +/- 16.0 years (in-person). Racial breakdown for telehealth was 60.7% White (N = 566), 10.4% Black (N = 97), 7.4% Asian (N = 69) and 4.5% Hispanic (N = 42); in-person was 70.9% White (N = 117), 5.5% Black (N = 9), 7.9% Asian (N = 13) and 5.5% Hispanic (N = 9). Top 5 consultation reasons, top 10 primary insurance providers and imaging studies ordered between the two cohorts were similar. Distance/travel time between primary zip code and clinic were 33.8 +/- 104.8 miles and 42.2 +/- 93.4 min (telehealth) vs. 38.1 +/- 114.7 miles and 44.1 +/- 97.6 min (in-person). DBS programming visits dropped 24.8% compared to the same period the year before (254 visits to 191 visits). Conclusion: Telehealth-based new patient visits to a Movement Disorders Center appeared successful at increasing access to specialty care. The minimal difference in supporting data highlights the potential parity to in-person visits. With no telehealth option for DBS visits, a significant drop-off was seen in routine DBS management.

Tig1 regulates proximo-distal identity during salamander limb regeneration.

Salamander limb regeneration is an accurate process which gives rise exclusively to the missing structures, irrespective of the amputation level. This suggests that cells in the stump have an awareness of their spatial location, a property termed positional identity. Little is known about how positional identity is encoded, in salamanders or other biological systems. Through single-cell RNAseq analysis, we identified Tig1/Rarres1 as a potential determinant of proximal identity. Tig1 encodes a conserved cell surface molecule, is regulated by retinoic acid and exhibits a graded expression along the proximo-distal axis of the limb. Its overexpression leads to regeneration defects in the distal elements and elicits proximal displacement of blastema cells, while its neutralisation blocks proximo-distal cell surface interactions. Critically, Tig1 reprogrammes distal cells to a proximal identity, upregulating Prod1 and inhibiting Hoxa13 and distal transcriptional networks. Thus, Tig1 is a central cell surface determinant of proximal identity in the salamander limb.

Prevalence of Pseudobulbar Affect (PBA) in Parkinson's Disease: An Underrecognized Patient Burden.

Objective Pseudobulbar affect (PBA) is a neurological condition characterized by emotional lability and a discrepancy between the patient's emotional expression and emotional experience. These uncontrollable episodes cause distress in social situations resulting in embarrassment and social withdrawal. The most comprehensive study to date estimated that 26% of Parkinson's disease (PD) patients screened positive for PBA symptoms via the validated Center for Neurologic Study-Lability Scale (CNS-LS) screening tool. We hypothesize that the prevalence of this disabling syndrome is higher than reported, often being labeled as depression. Methods One hundred patients were enrolled in the study and screened with a CNS-LS tool, all of whom were diagnosed with PD by a fellowship-trained movement disorder specialist. Patients were also asked about previous diagnosis of depression, current antidepressant medication use, and history of PBA diagnosis and treatment. Results The percentage of PD patients (n = 100) with PBA symptoms as defined by a CNS-LS score ≥13 was 41% (n = 41) and by a CNS-LS score ≥17 was 21.0% (n = 21). In our sample, 38.0% of patients (n = 38) had a previous clinical diagnosis of depression and 25.0% (n = 25) were currently undergoing treatment for their depression. There was a significant association between previous depression diagnosis, current antidepressant use, and higher CNS-LS scores (p < 0.001). Conclusion Using either of the CNS-LS score cutoffs, a significant proportion of the PD population in our sample displayed symptoms of PBA. We also found an association between previous diagnosis of depression and higher CNS-LS scores as well as between antidepressant use and higher CNS-LS scores. This suggests both a higher prevalence than prior studies showed as well as frequent misdiagnosis or co-diagnosis with depression.

Suicides at Shooting Ranges.

Background: Some shooting ranges have adopted policies to prevent suicides at their facilities. Little data have been available to guide them. Aim: We aimed to describe the incidence and characteristics of suicides at public shooting ranges. Method: We conducted text searches of 63,710 firearm suicides in the 16 states participating in the National Violent Death Reporting System from 2004 to 2015 to identify those occurring at public shooting ranges. Results: A total of 118 (or 0.18%) occurred at a shooting range, or 0.12 per million population. If that rate held for the nation as a whole, there would have been roughly 35 shooting range suicides per year during the study period. In total, 88% of decedents arrived alone. When gun ownership was noted, 86% of guns were rented from the range. In some cases, people drove to the range and took their lives in the parking lot with their own gun. Limitations: Our search strategy may have missed cases, and the data may not be nationally representative. Conclusion: Suicides at shooting ranges are rare. Policies that some ranges have adopted - such as allowing rentals only if the person is not alone - are responsive to the actual characteristics of these deaths and could potentially prevent most.

Intercellular Transfer of Mitochondria between Senescent Cells through Cytoskeleton-Supported Intercellular Bridges Requires mTOR and CDC42 Signalling.

Cellular senescence is a state of irreversible cell proliferation arrest induced by various stressors including telomere attrition, DNA damage, and oncogene induction. While beneficial as an acute response to stress, the accumulation of senescent cells with increasing age is thought to contribute adversely to the development of cancer and a number of other age-related diseases, including neurodegenerative diseases for which there are currently no effective disease-modifying therapies. Non-cell-autonomous effects of senescent cells have been suggested to arise through the SASP, a wide variety of proinflammatory cytokines, chemokines, and exosomes secreted by senescent cells. Here, we report an additional means of cell communication utilised by senescent cells via large numbers of membrane-bound intercellular bridges-or tunnelling nanotubes (TNTs)-containing the cytoskeletal components actin and tubulin, which form direct physical connections between cells. We observe the presence of mitochondria in these TNTs and show organelle transfer through the TNTs to adjacent cells. While transport of individual mitochondria along single TNTs appears by time-lapse studies to be unidirectional, we show by differentially labelled co-culture experiments that organelle transfer through TNTs can occur between different cells of equivalent cell age, but that senescent cells, rather than proliferating cells, appear to be predominant mitochondrial donors. Using small molecule inhibitors, we demonstrate that senescent cell TNTs are dependent on signalling through the mTOR pathway, which we further show is mediated at least in part through the downstream actin-cytoskeleton regulatory factor CDC42. These findings have significant implications for the development of senomodifying therapies, as they highlight the need to account for local direct cell-cell contacts as well as the SASP in order to treat cancer and diseases of ageing in which senescence is a key factor.

Rising from the ashes: cellular senescence in regeneration.

Cellular senescence has recently become causally implicated in pathological ageing. Hence, a great deal of research is currently dedicated towards developing senolytic agents to selectively kill senescent cells. However, senescence also plays important roles in a range of physiological processes including during organismal development, providing a barrier to tumorigenesis and in limiting fibrosis. Recent evidence also suggests a role for senescence in coordinating tissue remodelling and in the regeneration of complex structures. Through its non-cell-autonomous effects, a transient induction of senescence may create a permissive environment for remodelling or regeneration through promoting local proliferation, cell plasticity, tissue patterning, balancing growth, or indirectly through finely tuned interactions with infiltrating immune mediators. A careful analysis of the beneficial roles of cellular senescence may provide insights into important physiological processes as well as informing strategies to counteract its detrimental consequences in ageing and disease.