Expression of hsp90 mediates cytoprotective effects in the gastrodermis of planarians

Cell death in regeneration and cell turnover: Lessons from planarians and Drosophila

Programmed cell death plays a crucial role during tissue turnover in all animal species, and it is also essential during regeneration, serving as a key signalling mechanism to promote tissue repair and regrowth. In freshwater planarians, remarkable regenerative abilities are supported by neoblasts, a population of adult stem cells, which enable high somatic cell turnover. Cell death in planarians occurs continuously during regeneration and adult homeostasis, underscoring its critical role in tissue remodeling and repair. However, the exact mechanisms regulating cell death in these organisms remain elusive. In contrast, Drosophila melanogaster serves as a powerful model for studying programmed cell death in development, metamorphosis, and adult tissue maintenance, leveraging advanced genetic tools and visualization techniques. In Drosophila, cell death sculpts tissues, eliminates larval structures during metamorphosis, and supports homeostasis in adulthood. Despite limited regenerative capacity compared to planarians, Drosophila provides unique insights into cell death's regulatory mechanisms. Comparative analysis of these two systems highlights both conserved and divergent roles of programmed cell death in tissue renewal and regeneration. This review synthesizes the latest knowledge of programmed cell death in planarians and Drosophila, aiming to illuminate shared principles and system-specific adaptations, with relevance to tissue repair across biological systems.

Characterization of HSP90 expression and function following CNS injury

Spinal cord injury induces significant cellular stress responses. The Heat Shock Protein 90 (HSP90) plays a pivotal role as a molecular chaperone and is crucial for protein folding, stabilization, and cellular signaling pathways. Despite its important function in stress adaptation, the specific expression patterns and functional roles of HSP90 after nerve injury remain unclear. This study aimed to elucidate the expression dynamics and functional implications of HSP90 following central nervous system (CNS) injury. Using western blotting and immunohistochemical analyses, we observed upregulation of HSP90 expression in spinal cord tissues and within injured neurons in a spinal cord contusion injury model. Additionally, HSP90 was found to enhance neurite outgrowth in primary cortical neurons cultured in vitro. Furthermore, in a glutamate-induced neuronal injury model, the expression of HSP90 was up-regulated, and overexpression of HSP90 promoted neurite re-growth in damaged neurons. Overall, our findings highlight the critical involvement of HSP90 in the neural response to injury and offer valuable insights into potential therapeutic strategies for CNS repair.

It is not all about regeneration: Planarians striking power to stand starvation

All living forms, prokaryotes as eukaryotes, have some means of adaptation to food scarcity, which extends the survival chances under extreme environmental conditions. Nowadays we know that dietary interventions, including fasting, extends lifespan of many organisms and can also protect against age-related diseases including in humans. Therefore, the capacity of adapting to periods of food scarcity may have evolved billions of years ago not only to allow immediate organismal survival but also to be able to extend organismal lifespan or at least to lead to a healthier remaining lifespan. Planarians have been the center of attention since more than two centuries because of their astonishing power of full body regeneration that relies on a large amount of adult stem cells or neoblasts. However, they also present an often-overlooked characteristic. They are able to stand long time starvation. Planarians have adapted to periods of fasting by shrinking or degrowing. Here we will review the published data about starvation in planarians and conclude with the possibility of starvation being one of the processes that rejuvenate the planarian, thus explaining the historical notion of non-ageing planarians.

Djhsp90s are crucial regulators during planarian regeneration and tissue homeostasis

Heat shock protein 90 family members (HSP90s), as molecular chaperones, have conserved roles in the physiological processes of eukaryotes regulating cytoprotection, increasing host resistance and so on. However, whether HSP90s affect regeneration in animals is unclear. Planarians are emerging models for studying regeneration in vivo. Here, the roles of three hsp90 genes from planarian Dugesia japonica are investigated by WISH and RNAi. The results show that: (1) Djhsp90s expressions are induced by heat and cold shock, tissue damage and ionic liquid; (2) Djhsp90s mRNA are mainly distributed each side of the body in intact worms as well as blastemas in regenerative worms; (3) the worms show head regression, lysis, the body curling and the regeneration arrest or even failure after Djhsp90s RNAi; (4) Djhsp90s are involved in autophagy and locomotion of the body. The research results suggest that Djhsp90s are not only conserved in cytoprotection, but also involved in homeostasis maintenance and regeneration process by regulating different pathways in planarians.

Toxic effects of cadmium on flatworm stem cell dynamics: A transcriptomic and ultrastructural elucidation of underlying mechanisms

Stem cells or undifferentiated cells can cope more easily with external stresses. To evaluate the impact of toxic compounds on stem cell dynamics in vivo, in relation to other biological responses, we use the carcinogenic element cadmium and the regenerating model organism Macrostomum lignano. Through both BrdU and anti-histone H3 immunostainings, cadmium-induced effects were investigated at different stages of the stem cell cycle. A 24-h exposure to 100 and 250 μM CdCl2 significantly decreased the number of stem cells (neoblasts) in mitosis, whereas the number of cells in the S phase remained unchanged. After this short-term exposure, the ultrastructure of the neoblasts was minimally affected in contrast to the epidermal tissues. These results were supported by gene expression data: transcripts of cdc2 and pig3 were significantly upregulated during all treatments. Both genes are involved in the cell cycle progression and are transcribed in the gonadal region, where stem cells are highly represented. Based on a substantial increase in gene expression of heat shock proteins (HSP) and their high activity in the gonadal region, we hypothesize that these proteins are key players in the protection of stem cells against external stresses. Apart from the strong HSP induction, other protective processes including cell division, apoptosis and anti-oxidative defence, were also activated. We, therefore, conclude that the protection of stem cells against external stressors may be based on the interplay between stem cell maintenance, i.e. repair and recovery through division, on one hand and apoptosis on the other hand. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1217-1228, 2016.

UV-B radiation-induced oxidative stress and p38 signaling pathway involvement in the benthic copepod Tigriopus japonicus

Ultraviolet B (UV-B) radiation presents an environmental hazard to aquatic organisms. To understand the molecular responses of the intertidal copepod Tigriopus japonicus to UV-B radiation, we measured the acute toxicity response to 96 h of UV-B radiation, and we also assessed the intracellular reactive oxygen species (ROS) levels, glutathione (GSH) content, and antioxidant enzyme (GST, GR, GPx, and SOD) activities after 24 h of exposure to UV-B with LD50 and half LD50 values. Also, expression patterns of p53 and hsp gene families with phosphorylation of p38 MAPK were investigated in UV-B-exposed copepods. We found that the ROS level, GSH content, and antioxidant enzyme activity levels were increased with the transcriptional upregulation of antioxidant-related genes, indicating that UV-B induces oxidative stress by generating ROS and stimulating antioxidant enzymatic activity as a defense mechanism. Additionally, we found that p53 expression was significantly increased after UV-B irradiation due to increases in the phosphorylation of the stress-responsive p38 MAPK, indicating that UV-B may be responsible for inducing DNA damage in T. japonicus. Of the hsp family genes, transcriptional levels of hsp20, hsp20.7, hsp70, and hsp90 were elevated in response to a low dose of UV-B radiation (9 kJ m(-2)), suggesting that these hsp genes may be involved in cellular protection against UV-B radiation. In this paper, we performed a pathway-oriented mechanistic analysis in response to UV-B radiation, and this analysis provides a better understanding of the effects of UV-B in the intertidal benthic copepod T. japonicus.

Induction of hsp70, hsp90, and catalase activity in planarian Dugesia japonica exposed to cadmium

The hsp70 and hsp90 expression patterns and catalase (CAT) activity in the freshwater planaria Dugesia japonica exposed to cadmium (Cd) under laboratory conditions were investigated. Planaria were exposed to a range of Cd concentrations (0–150 μg Cd/L) for 24 h. The expression levels of hsp70 and hsp90 were determined by relative quantitative real-time polymerase chain reaction. Within the overall dose range in the experiment, the expression level of hsp70 and the activity of CAT in D. japonica were altered significantly. Hsp70 was induced in D. japonica upon Cd exposure concentrations as low as 9.375 μg Cd/L. No significant effect on the expression level of hsp90 was observed. Our findings demonstrated that stress gene hsp70, but not hsp90, was responsive to Cd contamination in D. japonica. CAT activity was significantly induced at concentrations of 18.75, 37.5, and 75 μg Cd/L after 24-h exposure. We recommend that the use of hsp70 as a biomarker should be complemented by evidence of changes in other parameters, such as CAT activity, in D. japonica.

Heat shock protein 90 is a potential therapeutic target for ameliorating skeletal muscle abnormalities in Parkinson's disease

Previous studies have confirmed that heat shock protein 90 overexpression can lead to dopaminergic neuronal death. This study was designed to further investigate what effects are produced by heat shock protein 90 after endurance exercise training. Immunohistochemistry results showed that exercise training significantly inhibited heat shock protein 90 overexpression in the soleus and gastrocnemius in Parkinson's disease rats, which is a potential therapeutic target for ameliorating skeletal muscle abnormalities in Parkinson's disease.

The history and enduring contributions of planarians to the study of animal regeneration

Having an almost unlimited capacity to regenerate tissues lost to age and injury, planarians have long fascinated naturalists. In the Western hemisphere alone, their documented history spans more than 200 years. Planarians were described in the early 19th century as being 'immortal under the edge of the knife', and initial investigation of these remarkable animals was significantly influenced by studies of regeneration in other organisms and from the flourishing field of experimental embryology in the late 19th and early 20th centuries. This review strives to place the study of planarian regeneration into a broader historical context by focusing on the significance and evolution of knowledge in this field. It also synthesizes our current molecular understanding of the mechanisms of planarian regeneration uncovered since this animal's relatively recent entrance into the molecular-genetic age.

A proteomics approach to decipher the molecular nature of planarian stem cells

Background

In recent years, planaria have emerged as an important model system for research into stem cells and regeneration. Attention is focused on their unique stem cells, the neoblasts, which can differentiate into any cell type present in the adult organism. Sequencing of the Schmidtea mediterranea genome and some expressed sequence tag projects have generated extensive data on the genetic profile of these cells. However, little information is available on their protein dynamics.

Results

We developed a proteomic strategy to identify neoblast-specific proteins. Here we describe the method and discuss the results in comparison to the genomic high-throughput analyses carried out in planaria and to proteomic studies using other stem cell systems. We also show functional data for some of the candidate genes selected in our proteomic approach.

Conclusions

We have developed an accurate and reliable mass-spectra-based proteomics approach to complement previous genomic studies and to further achieve a more accurate understanding and description of the molecular and cellular processes related to the neoblasts.