Search Results (65)

Since their initial discovery in 2003, carbon quantum dots (CDs) have attracted significant attention due to their unique optical properties and potential biomedical applications. This review critically examines the past 20 years of research on CDs, with a particular focus on cytotoxicity studies from the last decade. CDs, typically less than 10 nm in size, have been synthesized from various organic and inorganic precursors using multiple methods, including hydrothermal, microwave, and chemical reduction techniques. Their properties can be finely tuned by modifying synthesis parameters and incorporating dopants. The preliminary studies on the biological effects of CDs were published in 2013, highlighting their antibacterial properties and low toxicity in certain contexts. Subsequent research has explored their bioactivity, including their application in drug delivery, bioimaging, and photothermal therapy. However, the cytotoxicity of CDs remains a critical area of investigation. Further studies have demonstrated that surface functional groups, charge, concentration, and size significantly influence their interaction with biological systems. For instance, CDs with positive surface charges exhibit higher cellular uptake and greater cytotoxicity compared to their negatively charged counterparts. In vivo studies utilizing animal models such as zebrafish, mice, and planarians have provided valuable insights into the potential toxicological impacts of CDs. The results indicate that while CDs generally exhibit low toxicity at certain concentrations, high doses can lead to adverse effects, including oxidative stress, organ damage, and disrupted cellular functions. Notably, the route of administration (oral, intravenous, or intraperitoneal) also affects the observed toxicity profiles. The goal of this review is to integrate the results of various studies to provide a balanced perspective on the potential risks and benefits of CDs, guiding future research and applications in nanomedicine. This review underscores the necessity for standardized and comprehensive toxicological evaluations of CDs to fully understand their safety and efficacy for biomedical applications. Full article

ADCY9, a crucial member of the adenylate cyclase family, exerts neuroprotective and analgesic effects in the nervous system by modulating the activity of the cAMP/AMPK signaling pathway. However, the role of the ADCY9 gene in neural regeneration remains unreported. In this study, we utilized Dugesia japonica, a highly regenerative planarian species, as a model to systematically examine the spatiotemporal expression pattern of the ADCY9 gene during planarian brain regeneration and investigate its regulatory function in this process. The results demonstrated that the downregulation of ADCY9 resulted in abnormal brain regeneration in planarians, characterized by partial loss of the nerve cord, reduced numbers of collateral branches, and significant inhibition of the regeneration and differentiation of multiple neuron types. RNA sequencing revealed that the downregulation of ADCY9 led to 499 differentially expressed genes, with KEGG enrichment pathway analysis indicating significant associations with neurodegenerative diseases such as Alzheimer’s disease and Parkinson’s disease. Double RNAi experiments demonstrated that simultaneous knockdown of ADCY9 and Mitofusin-1 significantly restored neural regeneration. Collectively, ADCY9 might promote the comprehensive reconstruction of neural structure by hierarchically regulating the regeneration intensity through negative regulation of the downstream inhibitory factor Mitofusin-1. This study discloses the function of ADCY9 in planarian neural regeneration, providing a theoretical foundation for its application in investigating neural regeneration mechanisms and neurodegenerative disease pathogenesis in higher vertebrates. Full article

Ibrutinib (IB), a Bruton’s tyrosine kinase (BTK) inhibitor, is widely used against B-cell malignancies. However, its adverse effects on stem cell-dependent processes and tissue homeostasis remain incompletely understood. Freshwater planarians possess pluripotent stem cells (neoblasts), which enable remarkable regeneration of various tissues, including the central nervous system. This makes them ideal in vivo models for studying chemical toxicity within a whole-organism context. Here, we utilized planarian Dugesia constrictiva to assess IB toxicity and elucidate its mechanisms, focusing on its impact on stem cell dynamics and regeneration. Our results demonstrated that exposure to IB at concentrations as low as 0.9 mg/L, far below clinical plasma levels, led to severe morphological and regenerative impairments, including disrupted neural regeneration. Mechanistically, IB disrupted stem cell dynamics by suppressing proliferation and differentiation and by inducing oxidative stress via ROS overproduction. Notably, IB exposure significantly downregulated BTK expression. Crucially, BTK RNAi caused the key toxic effects of IB exposure, including morphological and regenerative defects, suppression of stem cell proliferation and differentiation, and increased apoptosis. Therefore, we conclude that IB may exert its toxicity in planarians primarily through BTK inhibition. This finding provides direct functional evidence linking BTK inhibition to stem cell dysfunction and regenerative defects in a novel in vivo context, offering critical insights for refining the clinical safety profile of IB. Full article

Freshwater planarians are an emerging model for toxicology and neuroscience because of their amenability to rapid behavioral screening and remarkable ability to regenerate a cephalized nervous system. As invertebrates, planarians can help reduce the use of vertebrates in research; however, laboratories typically maintain planarians on diets of homogenized organic beef or chicken liver, raising ethical concerns with feeding a vertebrate diet. Organic liver is difficult to obtain, and preparation methods vary, introducing intra- and interlaboratory variability. Here, we show that Dugesia japonica planarians can be maintained for over a year on commercially available red midge larvae (RML), a natural prey of freshwater planarians. We found only minor effects on reproduction and gene expression. To explore dietary effects on behavior and chemical sensitivity, we compared the results of a chemical screen using dimethyl sulfoxide, diazinon, and fluoxetine on adult and regenerating D. japonica. We found that differences in potency and bioactivity for planarians on liver and RML diets were on par with inter-experiment variability of planarians fed the same diet. We also show that RNA interference is feasible with RML. Because RML requires no preparation and sustains planarian populations long-term, this invertebrate diet can substitute liver and help reduce the use of vertebrates in research. Full article

The problem of steroid hormones in the aquatic environment remains a current global research topic. These substances have a strong impact on biological processes, contributing to reductions in the populations of numerous fish and amphibian species. The impact of steroid hormones, especially the third-generation progestogens, on aquatic invertebrates is poorly understood. We aimed to determine whether desogestrel, progestogen of low androgenic activity, affects the reproduction and growth of the following freshwater invertebrates: snails of the species Melanoides tuberculata and the planarian Dugesia sp. We also tried to estimate the threshold concentrations of this substance at which significant changes in both the behavior and reproductive activity of the studied organisms are observed. In the mesocosm experiment, we performed three treatments with the following different concentrations of desogestrel: control 0 ng/L, medium 10 ng/L, and high 100 ng/L. The high hormone concentration significantly reduced the reproduction of both snails and planarians, despite their different life history strategies, compared to the control. Both planarians and snails showed a significantly lower abundance in the high concentration compared to the 10 ng/L treatment, indicating a threshold concentration > 10 ng/L. The impacts of steroid hormone pollution on aquatic organisms and the need for further research are discussed. Full article

Rapid environmental change is reshaping freshwater ecosystems, influencing food availability and predator–prey dynamics. This study examined interactions among four freshwater invertebrates—the cnidarian Hydra viridissima (HV), the turbellarians Polycelis felina (PF) and Dugesia gonocephala (DG), and the cladoceran Daphnia magna (DM)—under controlled microcosm conditions. We investigated the effects of temperature, light regime, and predator satiation on predation intensity, prey survival, and interspecific behavior during the 24 h period. DM served as a universal prey, with survival strongly affected by both temperature and predator feeding state. Predation was generally higher at 25 °C and among hungry individuals. HV proved to be the most efficient predator and competitor, whereas DG dominated among planarians by preying on PF and adopting its dark pigmentation—a potential camouflage strategy enabling mimicry of both prey and habitat. PF responded by forming defensive groups, highlighting species-specific behavioral adaptations. PF simultaneously exhibited traits of both predators and prey. These findings demonstrate that microcosm experiments can reproducibly capture natural freshwater interaction patterns. Moreover, this study provides the first evidence of a planarian predator exhibiting both prey mimicry and environmental camouflage, revealing a novel behavioral strategy in flatworm ecology. Full article

Xylazine, an adulterant found frequently in illicit fentanyl, has been implicated in causing several adverse effects in human recreational users, including skin lesions and complications in the treatment of opiate overdose. Despite these public health concerns, the literature on the basic behavioral effects of xylazine is limited. Recent research has demonstrated that planarians show potential as an emerging and practical animal model for studying the behavioral effects of acute xylazine exposure. The goal of the current investigation was to evaluate the behavioral effects of chronic xylazine administration on negative phototaxis in two planarian species: Girardia tigrina and Schmidtea mediterranea. Three experiments were conducted. Overall, 10 µM of chronic xylazine exposure, arranged according to a multiple-baseline design, impaired negative phototaxis in S. mediterranea but not G. tigrina. An ABA reversal design indicated that behavioral effects in S. mediterranea abated when chronic xylazine was terminated. Finally, a between-group design replicated potential interspecies differences when G. tigrina and S. mediterranea were compared directly, with the latter showing significantly greater susceptibility to drug effects. This work provides evidence of the utility of a planarian model for studying the behavioral effects of xylazine and lays the foundation for further investigation into the chronic effects of the drug. Full article

Neurodegenerative diseases are characterized by progressive loss of neurons and remain largely incurable. Numerous mammalian models have been developed to study the mechanisms underlying their physiopathology; however, their high cost, complexity and time requirements highlight the need for alternative systems. Glial cells are increasingly recognized as key contributors to neurodegenerative disease progression through non-cell autonomous mechanisms. Planarians possess a nervous system with diverse neuronal subtypes and glial cells, offering an attractive combination of evolutionary conservation and remarkable regenerative capacity. Unlike mammalian glia, planarian glia originate from phagocytic progenitors and exhibit distinctive molecular markers, including if-1, cali and cathepsin. Emerging evidence suggests that planarian glia may contribute to neurotransmitter homeostasis, neuron–glia interactions and phagocytic activity. Additionally, planarians display robust and quantifiable behavioral responses, making them well suited for modeling neurodegenerative disease. In this review, we summarize the current findings regarding neuronal subtypes and glial cells in planaria, emphasizing their relevance as a model system. Further research into planarian glia will be crucial for understanding their roles in pathological contexts and for exploring their potential applications in neurodegenerative diseases research. Planarian simplicity, regenerative capacity, and compatibility with high-throughput approaches position planarians as a powerful model for investigating the cellular and molecular mechanisms underlying neurodegenerative diseases and for identifying potential therapeutic targets. Full article

Metformin is one of the most commonly used medications to treat type 2 diabetes. In addition to lowering blood sugar, it can also promote the regeneration of certain organs or tissues. Planarian Dugesia japonica, with its remarkable regenerative capacity, has become an important model organism for studying pharmacology and regenerative medicine. Planarian eyespot regeneration involves precise tissue regeneration via mechanisms like cell proliferation, differentiation, and gene regulation following body damage. Experiments on planarian eyespot regeneration have confirmed that 1 mM metformin significantly promotes regeneration. Through analysis of the regenerating planarian miRNA database and the metformin-treated transcriptome database, combined with target gene prediction by TargetScan, the DjmiR-27b/DjPax6 axis was finally determined as the research focus. qPCR showed that metformin significantly affects the expression levels of DjmiR-27b and DjPax6. DjPax6 was identified as the target gene of DjmiR-27b through dual luciferase reporter gene analysis. Functional experiments revealed that metformin regulates the expression of DjPax6 via DjmiR-27b, thereby influencing the regeneration of planarian eyespots. In situ hybridization showed that both DjmiR-27b and DjPax6 are expressed throughout the entire body. This study reveals the molecular mechanism of metformin regulating planarian regeneration through miRNA, providing further insights into its role in the field of regeneration. Full article

Background: The genus Dugesia (Platyhelminthes: Tricladida) includes a large diversity of free-living freshwater flatworms and is important for studies on regeneration and evolution. This study aims to describe a newly discovered asexual planarian species from southern China and explore its genetic characteristics and regenerative abilities. Methods: An integrative taxonomic analysis was conducted using morphology, karyology, histology, molecular phylogeny (18S, 28S, COI, mitogenome), and genome size estimation via flow cytometry. Regeneration was assessed by standardized amputations, and long-term asexual propagation was observed under laboratory conditions for three years. Results: Phylogenetic analyses using nuclear (18S, 28S rDNA) and mitochondrial (COI, mitogenome) markers confirmed that Dugesia cantonensis Guang Yang & Zhinan Yin, sp. nov. forms a distinct clade within Dugesia. Its 18,125 bp mitogenome contains 36 genes but lacks atp8. D. cantonensis displays a distinctive morphology, notably a pharynx located near the head. All body fragments regenerated into complete individuals within nine days. Remarkably, one individual produced ~10⁵ clonal descendants over three years via repeated amputation, maintaining stable regenerative ability and growth across generations. Karyological analysis revealed a diploid karyotype (2n = 16) consisting of eight chromosome pairs. The nuclear genome size was estimated at approximately 2.5 Gb using Danio rerio as an internal standard. Histological examination showed no detectable reproductive organs, confirming the species as an exclusively asexual lineage. Conclusions: D. cantonensis represents a new planarian strain with stable propagation and regeneration. These features make it a valuable resource for regenerative biology and comparative genomic studies. Full article

Background: Metformin is a widely used oral hypoglycemic agent for treating type 2 diabetes. Planarians, with their remarkable regenerative abilities, are frequently employed as model organisms in stem cell and regeneration studies. This study aimed to investigate the effects of metformin on planarian regeneration, focusing on the regeneration of eyespots after amputation. Methods: Regenerating planarians with amputated eyespots were exposed to various concentrations of metformin. The regeneration time of the eyespots was measured to assess the effects of metformin. Subsequently, a 1 mmol/L metformin treatment for 24 h was applied to the planarians, followed by transcriptome analysis to identify differentially expressed genes (DEGs). The gene expression was validated through qPCR. The full-length gene of casein kinase 1α (DjCK1α) was cloned using RACE technology. DjCK1α interference was performed to examine its role in regeneration. Results: Low concentrations of metformin significantly reduced the regeneration time of planarians. Transcriptome analysis identified 113 DEGs, including 61 upregulated and 52 downregulated genes. GO and KEGG enrichment analyses were conducted. Notably, DjCK1α, a key gene involved in regeneration, was selected for further validation. qPCR confirmed that DjCK1α was significantly upregulated. The interference of DjCK1α prolonged the regeneration time of the eyespots of planarians cultured in water, while treatment with metformin did not promote the eyespot regeneration of the DjCK1α-interfered planarians. Conclusions: The results suggest that metformin accelerates planarian eyespot regeneration, potentially through the regulation of DjCK1α. This study provides the first transcriptome-based analysis of drug effects on regeneration in planarians, highlighting the role of metformin in the regeneration process. Full article

Autophagy is a cellular recycling system that, through the sequestration and degradation of intracellular components regulates multiple cellular functions to maintain cellular homeostasis and survival. Dysregulation of autophagy is closely associated with the development of physiological alterations and human diseases, including the loss of regenerative capacity. Tissue regeneration is a highly complex process that relies on the coordinated interplay of several cellular processes, such as injury sensing, defense responses, cell proliferation, differentiation, migration, and cellular senescence. These processes act synergistically to repair or replace damaged tissues and restore their morphology and function. In this review, we examine the evidence supporting the involvement of the autophagy pathway in the different cellular mechanisms comprising the processes of regeneration and repair across different regenerative contexts. Additionally, we explore how modulating autophagy can enhance or accelerate regeneration and repair, highlighting autophagy as a promising therapeutic target in regenerative medicine for the development of autophagy-based treatments for human diseases. Full article

Despite significant improvements in the comprehension of neuro-regeneration, restoring nerve injury in humans continues to pose a substantial therapeutic difficulty. In the peripheral nervous system (PNS), the nerve regeneration process after injury relies on Schwann cells. These cells play a crucial role in regulating and releasing different extracellular matrix proteins, including laminin and fibronectin, which are essential for facilitating nerve regeneration. However, during regeneration, the nerve is required to regenerate for a long distance and, subsequently, loses its capacity to facilitate regeneration during this progression. Meanwhile, it has been noted that nerve regeneration has limited capabilities in the central nervous system (CNS) compared to in the PNS. The CNS contains factors that impede the regeneration of axons following injury to the axons. The presence of glial scar formation results from this unfavourable condition, where glial cells accumulate at the injury site, generating a physical and chemical barrier that hinders the regeneration of neurons. In contrast to humans, several species, such as axolotls, polychaetes, and planarians, possess the ability to regenerate their neural systems following amputation. This ability is based on the vast amount of pluripotent stem cells that have the remarkable capacity to differentiate and develop into any cell within their body. Although humans also possess these cells, their numbers are extremely limited. Examining the molecular pathways exhibited by these organisms has the potential to offer a foundational understanding of the human regeneration process. This review provides a concise overview of the molecular pathways involved in axolotl, polychaete, and planarian neuro-regeneration. It has the potential to offer a new perspective on therapeutic approaches for neuro-regeneration in humans. Full article

Background: Levels of chronic inflammation, oxidative stress, and neurotransmitter availability are altered in depressed patients and can be used as biological markers. This study aimed to analyze these markers in female Wistar rats under chronic inflammation induced by E. coli lipopolysaccharide (LPS), treated with aqueous extract of A. gratissima and rutin, the major flavonoid of its extract. Methods: Thirty female Wistar rats under a chronic inflammatory regimen induced by 1 mg/kg i.p. of LPS were divided into six experimental groups: control (1), treated with fluoxetine 5 mg/kg (2), rutin at 50 mg/kg (3) or 100 mg/kg (4), aqueous extract of A. gratissima 100 mg/kg (5), and co-treatment with 50 mg/kg of extract and 10 mg/kg of rutin (6). Treatments were administered by gavage for 15 days. Results: Oxidative damage to proteins and lipids was lower in group 6 compared to group 2. Pro- and anti-inflammatory cytokines increased in group 1 but not in group 2, indicating a relationship with depression. Similar effects were observed in the treated groups, showing no significant differences from group 2. Neurotransmitter levels of dopamine and serotonin were low in group 1, and all treatments effectively increased them. Additionally, A. gratissima extract at 100 ppm increased locomotor activity in planarians. Conclusions: This study demonstrates the effectiveness of the LPS induction model in subacute experimental designs and the potential antidepressant effect of the treatments due to their antioxidant and anti-inflammatory properties, and ability to increase neurotransmitter levels. Full article

The freshwater planarian is an emerging animal model in neuroscience due to its centralized nervous system that closely parallels closely parallels the nervous system of vertebrates. Cocaine, an abused drug, is the ‘founding member’ of the local anesthetic family. Parthenolide, a sesquiterpene lactone, acts as a behavioral and physiological antagonist of cocaine in planarians and rats, respectively. Previous work from our laboratory showed that both parthenolide and cocaine reduced planarian motility and that parthenolide reversed the cocaine-induced motility decrease at concentrations where parthenolide does not affect the movement of the worms. However, the exact mechanism of the cocaine/parthenolide antagonism is unknown. Here, we report the results of a Schild analysis to explore the parthenolide/cocaine relationship in the planarian Girardia tigrina. The Schild slopes of a family of concentration–response curves of parthenolide ± a single concentration of cocaine and vice versa were −0.55 and −0.36, respectively. These slopes were not statistically different from each other. Interestingly, the slope corresponding to the parthenolide ± cocaine (but not the cocaine ± parthenolide) data set was statistically different from −1. Our data suggest an allosteric relationship between cocaine and parthenolide for their effect on planarian motility. To the best of our knowledge, this is the first study about the mechanism of action of the antagonism between cocaine and parthenolide. Further studies are needed to determine the specific nature of the parthenolide/cocaine target(s) in this organism. Full article