Infertility in the hyperplasic ovary of freshwater planarians: the role of programmed cell death

Using autophagy, apoptosis, cytoskeleton, and epigenetics markers to investigate the origin of infertility in ex-fissiparous freshwater planarian individuals (nomen nudum species) with hyperplasic ovaries

The origin of the sterility observed in ex-fissiparous freshwater planarians with hyperplasic ovaries has yet to be explained. To improve our understanding of this enigmatic phenomenon, immunofluorescence staining and confocal microscopy examination were used the assess autophagy, apoptosis, cytoskeleton, and epigenetics markers in the hyperplasic ovaries of ex-fissiparous individuals and the normal ovaries of sexual individuals. Immunofluorescence positivity for the autophagic marker microtubule-associated protein1 light chain 3 (LC3) was significantly lower in the hyperplasic ovary than in the normal ovary. Compared with the normal ovary, the hyperplasic ovary exhibited significantly higher immunofluorescence positivity for the apoptotic marker caspase 3, suggesting that autophagy and apoptosis are closely associated in this pathogenicity. Furthermore, the level of global DNA (cytosine-5)-methyltransferase 3A (DNMT3) protein expression was significantly higher in the normal ovary than in the hyperplasic ovary, suggesting that DNA methylation is involved in the infertility phenomenon. The cytoskeleton marker actin also exhibited relatively higher immunofluorescence intensity in the normal ovary than in the hyperplasic ovary, consistent with previous findings on the role of cytoskeleton architecture in oocyte maturation. These results help improve our understanding of the causes of infertility in ex-fissiparous planarians with hyperplasic ovaries and provide new insights that will facilitate future studies on this mysterious pathogenicity.

Fetal programming: in utero exposure to acrylamide leads to intergenerational disrupted ovarian function and accelerated ovarian aging

In this study we investigated the effects of multigenerational exposures to acrylamide (ACR) on ovarian function. Fifty-day-old Wistar albino female rats were divided into the control and ACR-treated groups (2.5, 10, and 20 mg/kg/day) from day 6 of pregnancy until delivery. The obtained females of the first (AF1) and second generation (AF2) were euthanized at 4 weeks of age, and plasma and ovary samples were collected. We found that in utero multigenerational exposure to ACR reduced fertility and ovarian function in AF1 through inducing histopathological changes as evidenced by the appearance of cysts and degenerating follicles, oocyte vacuolization, and pyknosis in granulosa cells. TMR red positive cells confirmed by TUNEL assay were mostly detected in the stroma of the treated groups. Estradiol and IGF-1 concentrations significantly decreased as a result of decreased CYP19 gene and its protein expression. However, ACR exposure in AF2 led to early ovarian aging as evidenced by high estradiol and progesterone levels among all treated groups compared to control group, corresponding to the upregulation of the CYP19 gene and protein expression. The apoptotic cells of the stroma were greatly detected compared to that in the control group, whereas no significant difference was reported in ESR1 and ESR2 gene expression. This study confirms the developmental adverse effects of ACR on ovarian function and fertility in at least two consecutive generations. It emphasizes the need for more effective strategies during pregnancy, such as eating healthy foods and avoiding consumption of ACR-rich products, including fried foods and coffee.

The negative effect of the PI3K inhibitor 3-methyladenine on planarian regeneration via the autophagy signalling pathway

As an important PI3K (VPS34) inhibitor, 3-methyladenine (3-MA) can block the formation of autophagic vesicles in animals. Most toxicological studies using 3-MA have shown that 3-MA leads to serious disorders via autophagy suppression in mammals. However, no toxicological research on 3-MA has been performed on individuals undergoing regeneration. The freshwater planarian has powerful regenerative capability, and it can regenerate a new brain in 5 days and undergo complete adult individual remodelling in approximately 14 days. Moreover, it is also an excellent model organism for studies on environmental toxicology due to its high chemical sensitivity and extensive distribution. Here, Dugesia japonica planarians were treated with 3-MA, and the results showed that autophagy was inhibited and Djvps34 expression levels were down-regulated. After exposure to 10 mM 3-MA for 18 h, all the controls showed normal phenotypes, while one-half of the planarians treated with 3-MA showed morphological defects. In most cases, an ulcer appeared in the middle of the body, and a normal phenotype was restored 7 days following 3-MA exposure. During regeneration, disproportionate blastemas with tissue regression were observed. Furthermore, 3-MA treatment suppressed stem cell proliferation in intact and regenerating worms. These findings demonstrate that autophagy is indispensable for tissue homeostasis and regeneration in planarians and that 3-MA treatment is detrimental to planarian regeneration via its effect on the autophagy pathway.

When treatment increases the contaminant's ecotoxicity: A study of the Fenton process in the degradation of methylene blue

The degradation of dyes can generate harmful by-products, thereby requiring the need to evaluate the toxicity to aquatic organisms. This study aims to evaluate the chronic ecotoxicity of methylene blue dye degraded by the Fenton process using the non-target planarian Girardia tigrina as a sensitive bioindicator of environmental contamination. The bioassays evaluated the lethality of several concentrations of the untreated and degraded dye methylene blue (MB), as well as, their sub-lethal effects on locomotion, feeding, regeneration, and reproduction. In both acute and chronic tests, the degraded dye had a stronger toxic effect when compared to the untreated dye. This negative effect after treatment was mainly associated with the presence of residual hydrogen peroxide and iron (and consequently the hydroxyl radical formed). We conclude that the utilization of the Fenton process using less oxidizing agents should be considered as important alternatives for the protection of aquatic ecosystems, without compromising the efficient removal of MB.

Two new species of Dugesia (Platyhelminthes, Tricladida, Dugesiidae) from the tropical monsoon forest in southern China

Two new species of the genus Dugesia (Platyhelminthes, Tricladida, Dugesiidae) from the tropical monsoon forest in southern China are described on the basis of an integrative taxonomic study involving morphology, karyology, histology, and molecular analyses. The new species Dugesiacircumcisa Chen & Dong, sp. nov. is characterised by asymmetrical openings of the oviducts; right vas deferens opening at anterior portion of the seminal vesicle and the left one opening at mid-lateral portion of the seminal vesicle; two diaphragms in ejaculatory duct, the latter being ventrally displaced and opening at the tip of the penis papilla, which is provided with a nozzle; wide duct connecting male atrium and common atrium; chromosome complement triploid with 24 metacentric chromosomes. The other new species, Dugesiaverrucula Chen & Dong, sp. nov., is characterised by the large size of the living worm, usually exceeding 3.5 cm in length; asymmetrical openings of the oviducts; subterminal opening of ventrally displaced ejaculatory duct; vasa deferentia symmetrically opening into the postero-lateral portion of the seminal vesicle; well-developed duct between the seminal vesicle and diaphragm; single dorsal bump near the root of the penis papilla; bursal canal with pleated wall and spacious posterior section; unstalked cocoons; chromosome complement diploid with 16 metacentric chromosomes. Inter-specific molecular distances and their positions in the phylogenetic tree reveal that D.circumcisa and D.verrucula are clearly separated from their congeners.

Integrative descriptions of two new species of Dugesia from Hainan Island, China (Platyhelminthes, Tricladida, Dugesiidae)

Two new species of the genus Dugesia (Platyhelminthes, Tricladida, Dugesiidae) from Hainan Island of China are described on the basis of morphological, karyological and molecular data. Dugesiasemiglobosa Chen & Dong, sp. nov. is mainly characterized by a hemispherical, asymmetrical penis papilla with ventrally displaced ejaculatory duct opening terminally at tip of penis papilla; vasa deferentia separately opening into mid-dorsal portion of intrabulbar seminal vesicle; two diaphragms in the ejaculatory duct; copulatory bursa formed by expansion of bursal canal, lined with complex stratified epithelium, which projects through opening in bursa towards intestine, without having open communication with the gut; mixoploid chromosome complement diploid (2n = 16) and triploid (3n = 24), with metacentric chromosomes. Dugesiamajuscula Chen & Dong, sp. nov. is mainly characterized by oviducts opening asymmetrically into female reproductive system; hyperplasic ovaries; expanded posterior section of bursal canal; vasa deferentia separately opening into mid-dorsal portion of seminal vesicle; asymmetrical penis papilla due to ventral course of ejaculatory duct, which has subterminal and dorsal opening at tip papilla; mixoploid chromosome complement diploid (2n = 16) and triploid (3n = 24); chromosomes metacentric. Apart from their anatomy, separate species status of the two new species is supported also by their genetic distances and by their positions in the phylogenetic tree. The sexualization process may have been induced by the lower temperatures, in comparison with their natural habitat, under which the worms were cultured in the laboratory.

Autophagy-related Djatg8 is required for remodeling in planarian Dugesia japonica

Planarians are the earliest free-living platyhelminthe with triploblastic and bilateral-symmetry. As an integral component of tissue homeostasis and regeneration, remodeling occurs constantly in the general planarian life history. In the present study, we isolate three planarian Dugesia japonica Atg8 genes (Djatg8-1, Djatg8-2, Djatg8-3) that show high sequence similarity with Atg8 from yeast and human. Results from whole-mount in situ hybridization indicate that Djatg8-2 and Djatg8-3 are strongly expressed in blastemas during Dugesia japonica regeneration. Using RNA interference, inhibition of Djatg8-1 gene expression has no obvious effect on planarian morphological changes. Interestingly, downregulation of Djatg8-2 gene expression in planarians results in defects in blastema regeneration and tissue regression. Furthermore, loss of Djatg8-3 expression leads to tissue degradation. Taken together, our results suggest that Djatg8-2 and Djatg8-3 play important roles in planarian remodeling during regeneration.

Summary: The autophagy-related Djatg8 homologues Djatg8-2 and Djatg8-3 are required for planarian remodeling; we provide an emergent in vivo model organism to study autophagy and the molecular mechanism for planarian remodeling.

Dynamics of Cytokine-like Activity in the Hyperplasic Ovary of Ex-fissiparous Planarians

The origin of infertility in the hyperplasic ovary of ex-fissiparous planarians remains poorly understood. In a previous study we demonstrated that a complex process of early autophagy, followed by apoptotic processes, occurs in the hyperplasic ovary of the freshwater planarian Dugesia arabica. The present study aimed to investigate whether the mRNA expression levels of selected mRNA-like genes are altered in the hyperplasic ovary of the ex-fissiparous freshwater planarian D. arabica compared to the normal ovary. Using human cytokine-specific primers including interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α), we have successfully amplified by real-time polymerase chain reaction some transcripts that could be similar to those amplified in human. The transcript levels of the human-like transcript (IL-1-like and TNF-α-like) were significantly higher, 4.89- and 3.41-fold, respectively, in the hyperplasic ovary compared to the normal ovary (P < 0.05). However, although IL-6-like levels were higher in the hyperplasic ovary than the normal ovary (2.57-fold), this difference was not significant (P > 0.05). Immunohistochemical labeling supported the quantitative real-time PCR, showing that, like their respective mRNA expression levels, IL-1, IL-6, and TNF-α-like proteins are more highly expressed in the hyperplasic ovary than in the normal ovary.

Relationship between bcl-2, bax, beclin-1, and cathepsin-D proteins during postovulatory follicular regression in fish ovary

In fish ovaries, postovulatory follicles (POFs) are key biomarkers of breeding and provide an interesting model for studying the relationship between autophagy and apoptosis. In this study, we investigated the immunohistochemical expression of autophagic and apoptotic proteins to improve the knowledge on the mechanisms regulating ovarian remodeling after spawning. Females from three neotropical fish species kept in captivity were submitted to hormonal induction. After ova stripping, ovarian sections were sampled daily until 5 days postspawning (dps). Similar events of POF regression were detected by histology, terminal transferase-mediated dUTP nick-end labeling (TUNEL), and electron microscopy in the three species: follicular cells hypertrophy, progressive disintegration of the basement membrane, gradual closing of the follicular lumen, theca thickening, and formation of large autophagic vacuoles preceding apoptosis of the follicular cells. Autophagic and apoptotic proteins were assessed by immunohistochemistry. Morphometric analysis of the immunolabeling revealed a more intense reaction for bcl-2 and beclin-1 (BECN1) in POFs at 0 to 1 dps and for bax at 2 to 3 dps (P < 0.001), the later period being the peak of apoptosis of the follicular cells. The immunostaining for cathepsin-D was more elevated until 2 to 3 dps and decreased significantly at 4 to 5 dps, when the POFs were in late stage of regression. Double labeling for BECN1 and caspase-3 indicated a shift in the relationship between autophagy and apoptosis at 2 to 3 dps, a critical period in determining the fate of follicular cells in POFs. Together, these results indicate that the bcl-2 family, BECN1, and cathepsin-D can be involved in the regulation of ovarian remodeling in teleost fish.