Apoptosis as a possible mechanism of infertility inEchinococcus granulosus hydatid cysts

Potential use of silver nanoparticles green synthesized using Astragalus spinosus extract for treating cystic echinococcosis

The present investigation aims to develop and evaluate silver nanoparticles (AgNP) synthesized through environmentally friendly methods and to assess their effectiveness against hydatid cysts through in vitro, ex vivo, and in vivo experiments. The green synthesis of ANP was accomplished using the precipitation technique with Astragalus spinosus extract. The in vitro protoscolicidal effects of ANP were evaluated on hydatid cyst protoscoleces (PTS) through eosin exclusion test. The study also investigated the effect of ANP on the gene expression levels of caspase-3 and 9, as well as the external morphology of PTS. The in vivo efficacy was assessed by analyzing the quantity, dimensions, and weight of hydatid cysts in infected mice. Real-time PCR was used to analyze the gene expression levels of antioxidant and inflammatory cytokines. ANP exhibited significant (p < 0.001) in vitro protoscolicidal activity in a dose- and time-dependent manner. Treatment with ANP resulted in creases and protrusions on the plasma membrane, indicating bleb formation and an increase in the expression of caspase-3 and caspase-9 genes. Notably, there was a significant (p < 0.001) reduction in the number, size, and weight of hydatid cysts following ANP treatment. Administration of ANP resulted in a significant increase in the expression of antioxidant genes (glutathione peroxidase and superoxide dismutase) and a notable decrease in oxidative stress markers, as well as in the expression levels of Interleukin-4 (IL-4) and IL-10. Due to its antioxidant and anti-inflammatory properties, ANP shows potential as a scolicidal agent and holds promise in managing hydatid cysts in a mouse model. Nevertheless, further clinical trials are imperative to validate the efficacy of ANP in treating hydatidosis.

Comparative analysis of host immune responses to Hydatid cyst in human and ovine hepatic cystic Echinococcosis

BACKGROUND

Hydatid disease is caused by the larval stages of the canine tapeworm Echinococcus granulosus. It is one of the most critical helminthic diseases, representing worldwide public health and socio-economic concern.

AIM

This study aimed to investigate the expression of apoptosis and immune response within hepatic tissues of humans and sheep infected with the Hydatid cyst.

METHODS

Paraffin-embedded tissue was prepared from each tissue sample and used for histopathological examination by Haematoxylin- Eosin. Also, toluidine blue staining was used for mast cell detection, while an immunohistochemical study was performed to assess CD3 T lymphocytes, CD4 helper T lymphocytes, CD8 cytotoxic T lymphocytes, CD20 memory B lymphocytes, CD68 macrophage, and caspase-3 antibodies.

RESULTS

The histological examination revealed significant changes, including the infiltration of inflammatory cells, predominantly lymphocytes with scattered giant cells, necrotic hepatic tissue, and fibrosis. Toluidine blue stain revealed a higher number of mast cells (5 cells/field) in humans compared to sheep (3.6 cells/field). The immunohistochemical analysis confirmed that the CD3 were the most predominant inflammatory cell in the hepatic tissue of humans (intensive 70%), and sheep (moderate 38.47%). Caspase-3 was observed in all samples in different grades and mostly in human liver tissue.

CONCLUSION

This data could aid in recognizing immunological markers for differentiating disease progression, as well as enhance the understanding of local immune responses to cystic Echinococcosis (CE). The findings could provide preliminary data for future studies on immune responses associated with Hydatid cysts.

Scolicidal and apoptotic effects of phyto- and chemically synthesized silver/boehmite nanocomposites on Echinococcus granulosus protoscoleces

Cystic hydatid disease (CHD) is a zoonotic disease caused by the larval stage of Echinococcus granulosus (E. granulosus). This study aimed to synthesize silver nanoparticles (Ag NPs), silver boehmite nanocomposite (Ag/Bhm NC), and silver boehmite nanocomposite modified with chitosan (Ag/Bhm/Chit NC) using Rosmarinus officinalis (R. officinalis) extract and chemical method, and to evaluate their scolicidal and apoptotic effects on protoscoleces (PSCs) in vitro. The nanomaterials (NMs) were characterized by XRD, FTIR, FESEM, EDS, DLS, PDI, and zeta potential (ZP). The NMs were tested against PSCs at different concentrations (0.2-1.6 mg/mL) and exposure times (10-60 min). The size of Ag NPs, phytosynthesized Ag/Bhm NC, Ag/Bhm/Chit NC, and chemically synthesized Ag/Bhm NC were 25.55, 43, 72.3, and 60.8 nm, respectively. Ag NPs and phytosynthesized Ag/Bhm NC showed the highest scolicidal effect, with 65.34 % and 51.60 % mortality rate at 1.6 mg/mL and 60 min, respectively. Caspase-3 mRNA expression was higher in PSCs treated with Ag NPs and Ag/Bhm NC than in control groups (P < 0.05). Phytosynthesized Ag/Bhm NC had stronger scolicidal and apoptotic effect than chemically synthesized Ag/Bhm NC. Ag/Bhm/Chit NC had a weaker scolicidal effect but higher gene expression than Ag/Bhm NC. In conclusion, this study demonstrates the potential of phytosynthesized Ag NPs and Ag/Bhm NC as effective scolicidal and apoptotic agents against PSCs of hydatid cysts, which may be useful for the treatment of this disease.

Tumor suppressor p73 induces apoptosis of murine peritoneal cell after exposure to hydatid cyst antigens; a possibly survival mechanism of cystic echinococcosis in vivo mice model

Cystic echinococcosis (CE) is a life-threatening helminthic disease caused by the Echinococcus granulosus sensulato complex. Previous evidence indicates that the host's innate immune responses against CE can combat and regulate the growth rate and mortality of hydatid cyst in the host's internal organs. However, the survival mechanisms of CE are not yet fully elucidated in the human body. In the present study, the apoptotic effects of fertile and infertile hydatid fluid (HF) were tested on murine peritoneal cells in vivo mice model. Mice were divided into five groups including; control group, fertile HF-treated peritoneal cells, infertile HF-treated peritoneal cells, protoscolices (PSCs)-treated peritoneal cells and HF+PSCs-treated peritoneal cells group. Mice groups were intraperitoneally inoculated with PBS, HF, and/or PSCs. Afterwards, peritoneal cells were isolated and mRNA expression of STAT3, caspase-3, p73 and Smac genes were evaluated by quantitative Real-time PCR. After 48 hours of exposure, the protein levels of Smac and STAT3 was determined by western blotting technique. After 6 hours of exposure, Caspase-3 activity was also measured by fluorometric assay. The intracellular reactive oxygen species (ROS) production was examined in all groups. The mRNA expression levels of p73, caspase-3 and also Caspase-3 activity in HF+PSCs-treated peritoneal cells were higher than in the test and control groups (Pv<0.05), while the mRNA expression level of anti-apoptotic STAT3 and Smac genes in HF+PSC-treated peritoneal cells were lower than in the other groups (Pv<0.05). As well, the level of intracellular ROS in the fertile HCF-treated peritoneal cells, infertile HCF-treated peritoneal cells, PSC-treated peritoneal cells and HF+PSC-treated peritoneal cells groups were significantly higher than in the control group (Pv<0.05).Current findings indicates that oxidative stress and p73 can trigger the apoptosis of murine peritoneal cells through modulator of HF-treated PSCs that is likely one of the hydatid cyst survival mechanisms in vivo mice model.

Apoptosis as a Potential Target to Arrest and Survival of Hydatid Cyst

Background

Hydatidosis is a serious and life-threatening disease that may lead to the death of the host if diagnosed and treated improperly. Apoptosis has been investigated as a mechanism of host innate immunity in suppressing parasites and also the survival of cysts in the human body. The present study investigates the process and role of apoptosis caused by a host cell or parasite in hydatid cysts.

Materials and Methods

Survey cytotoxic effect and apoptotic mortality of hydatid-treated lymphocytes were investigated. Also, to determine the mechanism of apoptosis in host and parasite, the mean gene expressions of Bcl-2, Bax, Caspase 3 in hydatid-treated lymphocytes, and Fas-L gene in the laminated-germinal layer of fertile and infertile hydatid cysts were evaluated.

Results

The viability of fertile and infertile hydatid fluid-treated lymphocytes was significantly different compared with the control group. Flow cytometry also showed apoptotic cells. Bax mean gene expression was significantly different between fertile and infertile treated lymphocytes. However, there was no significant difference in the mean expression of Caspase 3, and Bcl-2 genes in these two groups. Although the expression of the Fas-L gene in infertile cysts was higher than in fertile cysts, the result was not significant.

Conclusion

It seems that hydatid cyst fluid may induce apoptosis in lymphocytes so that, hydatid cysts can escape from the immune system and stay alive. On the other hand, the results represent the possible immune path of host apoptosis against the parasite as one of the important routes in infertility of hydatid cysts.

Natural history of Echinococcus granulosus microcyst development in long term in vitro culture and molecular and morphological changes induced by insulin and BMP-4

Introduction

Cystic echinococcosis (CE) caused by the cestode Echinococcus granulosus is a disease of worldwide public health and economic importance. The determinants and underlying cellular mechanisms of CE development and fate in intermediate hosts are largely unknown. Hormones and cytokines such as insulin and BMP-4 are the key players in the development, differentiation, and apoptosis. In this study, we evaluated the long term natural history of E. granulosus microcysts in an vitro setting and the molecular and morphological changes induced by the growth factors, insulin and BMP4 during the development of metacestode stage of E. granulosus.

Methods

E. granulosus protoscoleces were cultivated and the parasite development was followed in the long term mono-phasic culture for 105 days and the morphometric, molecular and immunohistochemical changes were evaluated, including the microcysts number and size, microcysts development and deformation rates as well as the markers of calcification (Alizarin Red staining) and apoptosis (BAX, BCL2, Caspase-3, Caspase-8 and TNF-α expression) in the microcysts. Also the biological, histological and molecular consequences of insulin and BMP-4 treatment on the parasite development were evaluated.

Results

Insulin and BMP-4 treatment of microcysts resulted in significant increase in microcyst formation, increased size, reduced apoptosis and deformation of the microcysts. Alizarin red staining of the microcysts treated with the insulin and BMP-4 confirmed that calcium deposition is significantly lower than the untreated microcysts. Also Alizarin Red staining and Immunohistochemistry of the microcysts indicates that calcium accumulation in deformed microcysts is higher than the normal ones on day 105. The microcysts began to wrinkle and the germinal layer was partially detached from the laminated layer on day 84.

Conclusion

Results of the present study suggest that the degenerative changes in hydatid cysts can be slowed down by insulin and BMP-4, indicating that cellular factors and host hormones could contribute to the longevity of hydatid cysts. Significant evidences are provided suggesting that the microcysts cultivated in vitro can undergo calcification and apoptotic processes similar to what have been observed in the natural hydatid infection in the intermediate hosts.

Deciphering the role of miR-71 and let-7 in the fertility of cystic echinococcosis cysts: a preliminary assessment

Cystic echinococcosis (CE) is a neglected helminthic zoonosis in many parts of the world. Some CE cysts in the intermediate host are non-fertile. Considering the function of microRNAs in many biological processes such as embryonic development, cell proliferation, and apoptosis, this study investigated the function and comparison of miR-71 and let-7 in fertile and non-fertile CE cysts. Here, we determined the expression level of the miRNAs for 33 animal cysts and 16 human cysts (Echinococcus granulosus sensu stricto (G1). The quantitative real-time PCR method was conducted for the expression evaluation of miR-71 and let-7. The expression of both miRNAs in all samples was determined using the following formula: [ΔCT = CT (target) - CT (internal control)]. A comparison of Δct of miR-71 and let-7 in fertile and non-fertile cysts did not show a significant difference (P = 0.911 and 0.354). In cattle, sheep, and humans, Δct of miR-71, and let-7 were higher, respectively. Therefore, the mean expression of miR-71 and let-7 indicates an increase in humans compared to other intermediate hosts. Also, statistical results show a significant difference in the expression of these miRNAs in sheep, cattle, and human cysts (P = 0.025 and 0.01). The lower expression of these miRNAs in cattle cysts and their common infertility might be associated with the hypothesis and function of miRNAs in the fertility of CE cysts. So we should not ignore the function and role of miRNAs in this subject due to the importance of infertility in E. granulosus epidemiology.

MicroRNA profile of the strobilated worms of Echinococcus granulosus derived from in vivo and in vitro systems by using high-throughput approach

MicroRNAs are critical gene regulators at the post-transcriptional level and play essential roles in numerous developmental processes in metazoan parasites including the causative agent of cystic echinococcosis, Echinococcus granulosus. The molecular basis of different patterns of E. granulosus development in the canine definitive host and in in vitro culture systems is poorly understood. In the present study, miRNA transcriptomes of the strobilated worms derived from experimental infection in the definitive host were compared with those from diphasic culture system after 60-day protoscoleces cultivation. Total RNA was extracted from in vivo- and in vitro-derived strobilated worms. Small RNA libraries were constructed, and deep sequencing was performed. Subsequently, differential miRNA expressions and target predictions were obtained, and pathway analysis was performed by gene ontology and KEGG. Seven miRNAs were differentially expressed between the in vivo- and in vitro-derived worms. In addition, we reported 13 novel miRNA candidates and 42 conserved miRNAs. Four out of five top miRNAs with the highest read counts were shared between the in vivo and in vitro-derived worms, i.e., egr-miR-10a-5p, egr-let-7-5p, egr-bantam-3p, and egr-miR-71-5p. Target prediction of the differential miRNAs between the two systems showed significant differences in the membrane-enclosed lumen, membrane part, and an intrinsic component of the membrane. Findings of KEGG analysis indicated that differentially expressed miRNAs were involved in hippo, MAPK, and WNT signaling pathways. The study demonstrated a significant difference in miRNA transcriptomes and related signaling pathways between the two systems, suggesting the importance of host-parasite interplay in the fate of protoscoleces development in in vivo and in vitro systems.

Expression analysis of circulating miR-146a and miR-155 as novel biomarkers related to effective immune responses in human cystic echinococcosis

Cystic echinococcosis, an important zoonotic disease, is caused by Echinococcus granulosus. MicroRNAs are a small group of single-stranded noncoding RNAs, which play an effective role in biological processes. This study aimed at comparing the expression levels of miR-146a and miR-155 in the plasma of patients with hydatidosis and healthy individuals. A group of 20 patients with hydatid cyst formed a study group and 20 healthy individuals with no known chronic diseases formed a control group. Plasma samples were collected from hydatidosis patients as well as sex- and age-matched healthy volunteers. After that, RNA extraction and cDNA synthesis were done and the expression levels of miR-146a and miR-155 were determined by quantitative real-time polymerase chain reaction (PCR) for both groups. The results indicated that the level of miR-146a increased in all patients with hydatidosis compared to the control group. Also, the level of miR-155 increased in all hydatidosis patients, but no correlation was observed in the level of miR-155 between the two groups. The results also revealed that miR-146a and miR-155 upregulation in the plasma leads to the development of novel biomarkers for echinococcosis. One of the reasons for the increase of miRNAs in hydatidosis may be their role in modulating the immune system. These miRNAs are likely to be considered as one of the most important biomarkers in determining the severity of hydatidosis.

Fasciola hepatica co-infection enhances Th1 immune response in the adventitial layer of non-fertile Echinococcus granulosus cysts

Cystic echinococcosis is a widespread zoonosis caused by the larval stage of the tapeworm Echinococcus granulosus. In intermediary hosts, two types of echinococcal cysts can be found: fertile, which produce protoscoleces, the infective form of the parasite to dogs; and infertile, that do not present protoscoleces and therefore are not able to continue with the parasite life cycle. The adventitial layer, the local immune response against the cyst, plays an important role in cyst fertility. Grazing cattle can often feature Fasciola hepatica co-infection, a parasite known to modulate the host systemic immune response. In this work the cellular Th1/Th2 immune profiles were evaluated in the adventitial layer of fertile and non-fertile cysts with and without co-infection with Fasciola hepatica. Measuring with immunohistochemistry and qPCR in adventitial layer, we report that non-fertile cysts present higher levels of Th1 cytokines (IFN-γ (P < 0.0001) and TNF-α (P < 0.05)), and fertile cysts have higher levels of Th2 cytokines (IL-4 (P < 0.001)). Co-infection with Fasciola hepatica is associated with a decrease in the expression of IL-4 (P < 0.05) and an increase in the expression of IFN-γ (P < 0.0001) in the adventitial layer of fertile cysts. Non-fertile cysts were associated with higher levels of Th1 cytokines in the adventitial layer, with IFN-γ expression enhanced by F. hepatica co-infection (P < 0.0001), confirming that polyparasitism should be considered in the treatment and control of naturally infected cattle.

In Vitro and In Vivo Efficacies of the EGFR/MEK/ERK Signaling Inhibitors in the Treatment of Alveolar Echinococcosis

Alveolar echinococcosis (AE), caused by the larval stage of the cestode Echinococcus multilocularis, is a lethal disease in humans. Novel therapeutic options are urgently needed since the current chemotherapy displays limited efficiency in AE treatment. In this study, we assessed the in vitro and in vivo effects of the epidermal growth factor receptor (EGFR)/MEK/extracellular signal-regulated kinase (ERK) signaling inhibitors, including BIBW2992, CI-1033, and U0126, on E. multilocularis.

Alveolar echinococcosis (AE), caused by the larval stage of the cestode Echinococcus multilocularis, is a lethal disease in humans. Novel therapeutic options are urgently needed since the current chemotherapy displays limited efficiency in AE treatment. In this study, we assessed the in vitro and in vivo effects of the epidermal growth factor receptor (EGFR)/MEK/extracellular signal-regulated kinase (ERK) signaling inhibitors, including BIBW2992, CI-1033, and U0126, on E. multilocularis. Our data showed that BIBW2992, CI-1033, and U0126 all displayed in vitro effects on the viability of the E. multilocularis metacestode. These inhibitors also showed protoscolicidal activities and caused severe ultrastructural alterations in the parasite. Moreover, BIBW2992 and CI-1033 exhibited potent proapoptotic effects on E. multilocularis metacestodes. Strikingly, a large portion of the apoptotic cells were found to be the germinative cells. In vivo studies showed that BIBW2992 and U0126 significantly reduced parasite burden, and the parasite obtained from BIBW2992-treated mice displayed impaired structural integrity of the germinal layer. In conclusion, these findings demonstrate the potential of EGFR-mediated signaling as a target for the development of novel anti-AE agents. The EGFR inhibitor BIBW2992 represents a promising drug candidate and/or a lead compound for anti-AE chemotherapy.

Fasciola hepatica coinfection modifies the morphological and immunological features of Echinococcus granulosus cysts in cattle

Polyparasitism occurs when animals harbour multiple parasites concomitantly. It is a common occurrence but is generally understudied in wild and domestic animals. Fasciola hepatica and Echinococcus granulosus, which are helminths of ungulates, frequently coinfect cattle. The effects of this particular type of polyparasitism are not well documented. The metacestode of Echinococcus granulosus is surrounded by the adventitial layer, which constitutes the host immune response to the parasite. This layer in cattle is produced by a granulomatous reaction and is involved in echinococcal cyst (EC) fertility. Due to the systemic immune-modulating abilities of Fasciola hepatica, coinfection possibly generates a favourable environment for EC growth. A total of 203 Echinococcus granulosus sensu stricto cysts were found in 82 cattle, of which 42 ECs were found in 31 animals coinfected with Fasciola hepatica. The overall infection intensity was 3 cysts per animal. Coinfection with Fasciola hepatica decreased the mean infection intensity to 1.4 cysts per animal. Regarding EC size, coinfection resulted in smaller ECs (15.91 vs 22.09 mm), especially for infertile lung cysts. The adventitial layer of ECs in coinfected animals lacked lymphoid follicles and palisading macrophages, which are generally hallmarks of the granulomatous immune response. The ECs in coinfected animals had organized laminated layers, whereas those in animals without coinfection did not. Although coinfection was not statistically associated with EC fertility, we did not find fertile cysts in the livers of coinfected animals. We concluded that coinfection with Fasciola hepatica and Echinococcus granulosus has a detrimental effect on ECs, particularly infertile cysts.

Recent advances on innate immune pathways related to host-parasite cross-talk in cystic and alveolar echinococcosis

Cystic echinococcosis (CE) and alveolar echinococcosis (AE) are life-threatening parasitic infections worldwide caused by Echinococcus granulosus (sensu lato) and E. multilocularis, respectively. Very little is known about the factors affecting innate susceptibility and resistance to infection with Echinococcus spp. Although benzimidazolic drugs against CE and AE have definitively improved the treatment of these cestodes; however, the lack of successful control campaigns, including the EG95 vaccine, at a continental level indicates the importance of generating novel therapies. This review represents an update on the latest developments in the regulatory functions of innate immune pathways such as apoptosis, toll-like receptors (TLRs), and inflammasomes against CE and AE. We suggest that apoptosis can reciprocally play a bi-functional role among the host-Echinococcus metabolite relationships in suppressive and survival mechanisms of CE. Based on the available information, further studies are needed to determine whether the orchestrated in silico strategy for designing inhibitors and interfering RNA against anti-apoptotic proteins and TLRs would be effective to improve new treatments as well as therapeutic vaccines against the E. granulosus and E. multilocularis.

Molecular and Functional Characterization of Inhibitor of Apoptosis Proteins (IAP, BIRP) in Echinococcus granulosus

The larval stage of Echinococcus granulosus sensu lato, resulting in cystic echinococcosis, a parasitic zoonosis, causes huge economic losses to the livestock industry and poses a threat to public health. Inhibitor of apoptosis proteins (IAPs) is a class of endogenous anti-apoptotic family, which plays a significant functional role in the regulation of organism’s development. Herein, to explore potential functions of IAPs in E. granulosus, two members of IAPs from E. granulosus (Eg-IAP and Eg-BIRP) were cloned, expressed, and molecularly characterized. Eg-IAP and Eg-BIRP encoded putative 331 and 168 residue proteins, respectively. Bioinformatic analysis showed that both proteins contained a type II BIR domain-the essential functional domain of IAPs. Fluorescence immunohistochemistry revealed that both proteins were ubiquitously localized in all life-cycle stages of E. granulosus. Our fluorescent quantitative PCR (RT-qPCR) results revealed relatively higher transcription levels of two Eg-IAPs in protoscoleces (PSCs) compared to the 18-day strobilated worms. We further used different concentrations of LCL161, a Smac-mimetic pan-IAPs inhibitor, to induce the apoptosis in PSCs in vitro, and revealed that the survival rate of PSCs and transcription levels of both genes were negatively correlated with the concentration of LCL161. While the results of light microscopy, transmission electron microscopy (TEM), and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay also showed a higher apoptotic rate in PSCs with the increasing concentrations of LCL161. Taken together, our findings provide the reasonable evidence that both Eg-IAP and Eg-BIRP have potential implication in critical anti-apoptotic roles during the development of E. granulosus.

Interactions between hydatid cyst and regulated cell death may provide new therapeutic opportunities

Cystic echinococcosis and alveolar echinococcosis are chronic zoonotic infections, transmitted throughout the world. Development of the cestode larval stages in the liver and lungs causes damage to intermediate hosts, including humans. Several pathways leading to the suppression of host immune response and the survival of the cysts in various hosts are known. Immune response modulation and regulated cell death (RCD) play a fundamental role in cyst formation, development and pathogenesis. RCD, referring to apoptosis, necrosis and autophagy, can be triggered either via intrinsic or extrinsic cell stimuli. In this review, we provide a general overview of current knowledge on the process of RCD during echinococcosis. The study of interactions between RCD and Echinococcus spp. metacestodes may provide in-depth understanding of echinococcosis pathogenesis and open new horizons for human intervention and treatment of the disease.

Nanostructured lipid carriers of ivermectin as a novel drug delivery system in hydatidosis

Background

The larval stage of the tapeworm Echinococcus granulosus is the causative agent of hydatid disease in humans. This zoonotic parasitic infection remains a major health problem in certain areas of the world where is still endemic. In view of the ineffectiveness of some drug treatments, the surgical removal of cysts remains the preferred treatment option together with the administration of albendazole and mebendazole. However, severe side effects of these drugs have been reported which demands developing new scolicidal agents that confer suitable efficacy and fewer side effects during surgery.

Methods

To that purpose, in the present work we assessed the effectiveness of ivermectin (IVM), a macrocyclic lactone endectocide that has shown to be an effective nematocidal drug against other important parasitic infections. To overcome the limitations observed in some drug formulations and resistance, we used nano lipid carriers (NLCs) as a targeted and sustained drug delivery system for IVM. We evaluated the in vitro cestocidal and apoptotic effects of NLCs-loaded IVM versus IVM by quantifying the expression of caspase-3 mRNA.

Results

We found that after 60 and 120 min of administration, 800 μg/ml and 400 μg/ml NLCs-loaded IVM induced 100% mortality, respectively. On the other hand, the 800 μg/ml of IVM induced 100% mortality rate 150 min after administration. Additionally, we found that NLCs-loaded IVM induced higher mRNA caspase-3 expression suggesting a more potent apoptotic effect on the parasite.

Conclusions

These data suggest that NLCs-loaded IVM may be a promising alternative to current treatments although in vivo studies are needed.

Effect of Hydatid Cyst Fluid Antigens on Induction of Apoptosis on Breast Cancer Cells

Background

Hydatid cyst is a zoonotic and parasitic disease with worldwide distribution. Anticancer effects of hydatid cyst have been shown in cell culture experiments and animal model investigations. The mechanism of anti-cancer effects of hydatid cyst fluid has not been clearly elucidated, and the induction of apoptosis may have a role in this regard. Hence, in this study, the effect of hydatid cyst fluid (HCF) on the induction of apoptosis on mouse breast cancer (4T1) cell line in cell culture medium has been investigated.

Materials and Methods

Echinococcus granulosus HCF antigens including Antigen B (AgB), glycolipid, glycoprotein, and 78 KDa fractions were prepared. Breast cancer cell line (4T1) was cultured in RPMI-1640 medium supplemented with 10% fetal bovine serum and appropriate antibiotics. Apoptosis was determined by flow cytometry using the annexin V-fluorescein isothiocyanate apoptosis kit.

Results

The 78 KDa and glycoprotein fractions induced more than 40% apoptosis. HCF and glycolipid antigens induced 39% and 34% apoptosis, respectively. However, less apoptosis observed after treatment with AgB fraction.

Conclusion

Hydatid cyst antigens especially the 78 KDa and glycoprotein fractions induced apoptosis on mouse breast cancer cells.

Sodium arsenite augments sensitivity of Echinococcus granulosus protoscoleces to albendazole

This study aimed to observe the effects of sodium arsenite (NaAsO₂) on apoptosis of Echinococcus granulosus protoscoleces induced by albendazole (ABZ), and to explore the potential mechanism of NaAsO₂. According to the following final concentrations, the experimental groups were divided into 10 μM NaAsO₂, 20 μM NaAsO₂, 80 μM ABZ, 10 μM NaAsO₂+80 μM ABZ, and 20 μM NaAsO₂+80 μM ABZ. Viability was detected with 0.1% eosin staining. The ultrastructural alterations were visualized by scanning electron microscopy. Caspase-3 activity was assessed with colorimetric assay. Meanwhile, ELISA or WST were applied to detect the activities of antioxidases in NaAsO₂ treatment groups. The maximum protoscolicidal effect was seen with the combination 20 μM NaAsO₂+80 μM ABZ. The ultrastructural damage detected after NaAsO₂+ABZ incubation were greater than those caused by ABZ alone and its primary damage site was the tegument of the parasite. The caspase-3 activity was clearly higher in protoscoleces treated with the combination of NaAsO₂+ABZ than when drugs were used separately. The activities of NQO-1, HO-1, GST, and SOD were significantly lower in protoscoleces incubated with NaAsO₂ than the untreated controls (P < 0.05). According to our results, ABZ could induce protoscoleces apoptosis, and NaAsO₂ could significantly augment sensitivity of protoscoleces to ABZ.

Inhibitory Effect of Ionizing Radiation on Echinococcus granulosus Hydatid Cyst

BACKGROUND

Heavy ion radiation has more advantages than traditional radiation therapy in the treatment of cancer, mainly because of its superior biological effects. However, there is currently no reliable evidence that heavy ion radiation can induce cell death in hydatid cysts at the cellular and molecular level. In addition, we believe heavy ion therapy could be a potential alternative approach for the treatment of hydatid cysts.

METHODOLOGY/PRINCIPAL FINDING

The hydatid cysts and protoscolices were obtained from an experimentally infected KunMing mice. LD50 was used to evaluate the death of the protoscolex. The cellular and ultrastructure of the parasites were observed under light and electron microscopes, the damage and copy numbers of mitochondrial DNA (mtDNA) were decided by QPCR. The apoptosis was evaluated by the expression and activity of caspase3. Dose-dependent ionizing radiation induced damage to the initial mtDNA. Echinococcosis cyst after ionizing radiation showed sparse cytoplasm, disorganized and clumped organelles, huge vacuoles, and villus deletions. The kinetic of DNA repair activity after X-ray irradiation was faster than those after carbon-ion irradiation. High doses of carbon ion radiation caused irreversible attenuation of mitochondrial DNA. Cysts showed obvious reduction in size after radiation. Carbon ion radiation was more effective than X-ray radiation in inhibiting hydatid cysts.

CONCLUSIONS

These studies provide evidence that heavy-ion radiation can cause the extinction of hydatid cysts in vitro. The carbon-ion radiation is more advantageous than X-ray radiation in suppress hydatid cyst.

New insights of the local immune response against both fertile and infertile hydatid cysts

BACKGROUND

Cystic echinococcosis is caused by the metacestode of the zoonotic flatworm Echinococcus granulosus. Within the viscera of the intermediate host, the metacestode grows as a unilocular cyst known as hydatid cyst. This cyst is comprised of two layers of parasite origin: germinal and laminated layers, and one of host origin: the adventitial layer, that encapsulates the parasite. This adventitial layer is composed of collagen fibers, epithelioid cells, eosinophils and lymphocytes. To establish itself inside the host, the germinal layer produces the laminated layer, and to continue its life cycle, generates protoscoleces. Some cysts are unable to produce protoscoleces, and are defined as infertile cysts. The molecular mechanisms involved in cyst fertility are not clear, however, the host immune response could play a crucial role.

METHODOLOGY/PRINCIPAL FINDINGS

We collected hydatid cysts from both liver and lungs of slaughtered cattle, and histological sections of fertile, infertile and small hydatid cysts were stained with haematoxylin-eosin. A common feature observed in infertile cysts was the disorganization of the laminated layer by the infiltration of host immune cells. These infiltrating cells eventually destroy parts of laminated layer. Immunohistochemical analysis of both parasite and host antigens, identify these cells as cattle macrophages and are present inside the cysts associated to germinal layer.

CONCLUSIONS/SIGNIFICANCE

This is the first report that indicates to cell from immune system present in adventitial layer of infertile bovine hydatid cysts could disrupt the laminated layer, infiltrating and probably causing the infertility of cyst.

Echinococcus granulosus hydatid cyst location is modified by Fasciola hepatica infection in cattle

BACKGROUND

Natural parasite infection occurs in wild and domestics animals with more than one parasite species at the same time, generating an infection called polyparasitism. Cystic echinococcosis reports are usually based only on infection with Echinoccocus granulosus leaving aside other internal parasitoses that could modulate both the immune response and pathogenesis of the natural infection. Fasciola hepatica is another cosmopolitan parasite in ruminants with a similar distribution to E. granulosus in different parts of the world, but no information of the effect of co-infection with E. granulosus has been described. The aims of this report were to establish E. granulosus prevalence and explore the association of F. hepatica co-infection and natural E. granulosus infections in cattle.

RESULTS

From 1725 animals, the prevalence of E. granulosus and F. hepatica was 21.16 and 51.3%, respectively. Considering both infections, older cattle (> 4 years) presented higher prevalence compared to younger animals. In E. granulosus-infected cattle, 5.21% had fertile cysts, 71.78% infertile cysts, and in 23.01% cysts were smaller than 1 cm in diameter. Considering cyst location, 39.72% had lungs cysts, 24.72% had liver cysts and 36.94% had cysts in both organs. Cyst location significantly differed between age groups: 44.68% of younger animals had cysts only in the lungs, while older animals presented hydatid cyst in the lungs and liver simultaneously (44.15%). With E. granulosus infection alone, 30.26% of cysts were found in the lungs, 31.79% in the liver and 37.95% in both organs. Regarding the co-infection of E. granulosus with F. hepatica, the proportion was significantly different (P < 0.05) with most animals having cysts only in the lungs (49.41%) and a lower level of liver infection (15.88%). Analyzing organ cyst distribution and F. hepatica absence/presence ratio within each cyst type, small cysts showed the highest difference in ratio.

CONCLUSIONS

To the best of our knowledge, this is the first report indicating that F. hepatica co-infection in cattle could be affecting the instate of hydatid cysts in the liver, displacing toward lung localization, suggesting an antagonistic relationship.

Molecular Characterisation and Functions of Fis1 and PDCD6 Genes from Echinococcus granulosus

Cystic echinococcosis, a parasitic zoonosis that causes significant economic losses and poses a threat to public health, is caused by larvae of the tapeworm Echinococcus granulosus. Infection causes infertile cysts in intermediate hosts that cannot produce protoscoleces (PSCs) or complete the life cycle. Herein, we cloned, expressed, and characterised mitochondrial fission protein 1 (Eg-Fis1) and programmed cell death protein 6 (Eg-PDCD6) from E. granulosus, and explored their functions related to infertile cysts. Eg-Fis1 and Eg-PDCD6 encode putative 157 and 174 residue proteins, respectively, and Western blotting indicated good reactogenicity for both. Eg-Fis1 and Eg-PDCD6 were ubiquitously distributed in all stages of E. granulosus. Furthermore, mRNAs of Eg-Fis1 and Eg-PDCD6 were upregulated following H₂O₂ treatment which induced apoptosis in PSCs. To investigate the regulation of apoptosis in response to oxidative stress, RNA interference (RNAi) and terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL) assays were performed. The apoptotic rate of the Eg-Fis1 RNAi group was significantly lower than non-interference group, but there was no such difference for Eg-PDCD6. In conclusion, Eg-Fis1 promotes apoptosis induced by oxidative stress, whereas Eg-PDCD6 does not appear to be a key regulator of apoptosis.

Evaluating the effect of Myrtus communis on programmed cell death in hydatid cyst protoscolices

OBJECTIVE

To evaluate the possible involvement of programmed cell death strategy in hydatid cyst protoscolices following treatment with Myrtus communis (M. communis) as an herbal medicine.

METHODS

Protoscolices were aseptically collected from sheep liver hydatid cysts. Evaluating the effect of M. communis extract on programmed cell death and increased activity of caspases 3, 8, and 9 in hydatid cyst protoscolices was conducted by treating the protoscolices with different concentration (5, 50, and 100 mg/mL) of M. communis extract at 37 °C and 5% CO₂ for 4 h by using the Bradford test and ELISA commercial kits.

RESULTS

The extract of M. communis at all concentrations led to initiation of programmed cell death in protoscolices and this effect, was only significant at 50 and 100 mg/mL concentrations, compared to the negative control (P < 0.05). Also, the activity of caspases 3, 8, and 9 in hydatid cyst protoscolices, was shown that the extract at all 3 concentrations could only increase the activity of caspases 3 and 9. Moreover, a significant increase in the activity of caspase 3 was only observed at concentrations 50 and 100 mg/mL by 37.00% and 66.19% while a significant increase in the activity of caspase 9 at the same concentrations was observed by 20.89% and 63.67%, respectively (P < 0.05).

CONCLUSIONS

The extract of M. communis at different concentrations could increase the activity of caspases 3 and 9 and caused programmed cell death in hydatid cyst protoscolices however, this effect was significant at high concentrations of the extract.

Parasite molecules and host responses in cystic echinococcosis

Cystic echinococcosis is the infection by the larvae of cestode parasites belonging to the Echinococcus granulosus sensu lato species complex. Local host responses are strikingly subdued in relation to the size and persistence of these larvae, which develop within mammalian organs as 'hydatid cysts' measuring up to tens of cm in diameter. In a context in which helminth-derived immune-suppressive, as well as Th2-inducing, molecules garner much interest, knowledge on the interactions between E. granulosus molecules and the immune system lags behind. Here, we discuss what is known and what are the open questions on E. granulosus molecules and structures interacting with the innate and adaptive immune systems, potentially or in demonstrated form. We attempt a global biological approach on molecules that have been given consideration primarily as protective (Eg95) or diagnostic antigens (antigen B, antigen 5). We integrate glycobiological information, which traverses the discussions on antigen 5, the mucin-based protective laminated layer and immunologically active preparations from protoscoleces. We also highlight some less well-known molecules that appear as promising candidates to possess immune-regulatory activities. Finally, we point out gaps in the molecular-level knowledge of this infectious agent that hinder our understanding of its immunology.

Post-immunization immunohistochemical expression of Caspase 3 and p53 apoptotic markers in experimental hydatidosis

Abstract The aim of this study was to investigate post-immunization apoptotic changes in experimental hydatidosis, using Caspase 3 and p53 immunohistochemical markers. Two groups of rabbits were immunized with a crude antigen (group 1) or a partially purified antigen (group 2) and were compared to an infected non-immunized control group. More effective immune responses were obtained in group 2 than group 1, signified by fewer and smaller cystic lesions and more severe destructive changes. Normal growth of cysts was attained in the control group, with no expression of apoptotic markers. Significantly higher expression of Caspase 3 and p53 were observed in group 1 compared to group 2, as indicated by OD and area percentage, respectively (Group 1 Caspase 3: 0.89±0.21, 93.5%±6.2; Group 1 p53: 0.46±0.18, 53.26%±11.6; Group 2 Caspase 3: 0.52±0.15, 49.23%±11.7; Group 2 p53: 0.19±0.4, 18.17%±7.3). Vaccine-induced immune responses and cellular damage may underlie the expression of apoptotic markers that appeared to result in a degenerative and atrophic course of action upon immunization. The results of the current study emphasize the importance of immunization for the stimulation of protective immune responses and in preventing mechanisms of evasion to ensure normal cell growth. A cost/benefit control program that implements proper vaccine preparations should be further assessed for complete elimination of severe infections in endemic areas.

Protoscolicidal effects of chenodeoxycholic acid on protoscoleces of Echinococcus granulosus

Dissemination of protoscoleces-rich fluid during surgical operation for cystic echinococcosis is a major cause of its recurrence. Instillation of a scolicidal agent into hydatid cysts to reduce the risk of spillage of viable protoscoleces is an integral part of the surgical technique employed by many surgeons. In this study, the protoscolicidal effect of chenodeoxycholic acid (CDCA) was investigated. Freshly isolated protoscoleces were subjected to CDCA treatment (500, 1000, 2000, and 3000 μmol/L), and the effects on protoscoleces were investigated with the help of 0.1% eosin staining, electron microscopy, and colorimetric assay of caspase-3 like activity. Dose-dependent mortality of Echinococcus granulosus protoscoleces was observed within a few days of CDCA treatment. The treated protoscoleces showed loss of viability, and morphological changes such as contraction of the soma region, formation of blebs, rostellar disorganization, loss of hooks, destruction of microtriches, and formation of vesicles, lipid droplets, and lamellar bodies. Apoptosis was evident in the treated protoscoleces, as compared to the control group, which were cultivated for nearly 3 months. Our study indicates a therapeutic potential for CDCA as a protoscolicidal agent against E. granulosus. However, further studies are needed to test the long-term effects of CDCA in animal models.

Surgical treatment of multiple hydatid cysts in the liver of a pediatric patient

Multiple hydatid cysts in the liver rarely occur in the pediatric population. Here, we present the case of a 16-year-old girl who presented with six hydatid cysts in the liver. The cysts were surgically removed and all found to be infertile. Interestingly, the patient had post-operative eosinophilia. From this experience, we conclude that individualized treatment is necessary for patients with multiple hydatid cysts.

Efficacy of Essential Oils of Thymus vulgaris and Origanum vulgare on Echinococcus granulosus

The aim of the present work was to determine the in vitro effect of T. vulgaris and O. vulgare essential oils against E. granulosus protoscoleces and cysts. Essential oils were added to the medium resulting in thymol final concentrations of 10 μg/mL. The essential oils had a time-dependent effect provoking the complete loss of protoscolex viability after 72 days of postincubation. The results were confirmed at the ultrastructure level. Loss of infectivity in protoscoleces incubated with O. vulgare after 60 days was observed. On the other hand, the weight of cysts recorded in mice inoculated with T. vulgaris treated protoscoleces was significantly lower than that obtained in control group. Gamma-glutamyl-transpeptidase activity was readily detected in the culture supernatant of protoscoleces treated either with the essential oils or thymol. T. vulgaris and O. vulgare essential oils and thymol can induce cell apoptosis of protoscoleces after short incubation times. The efficacy of T. vulgaris and O. vulgare essential oils was also demonstrated in vitro on E. granulosus murine cysts. Our data suggest that essential oils of T. vulgaris and O. vulgare have anthelmintic effect against protoscoleces and cysts of E. granulosus.

Suppression of E. multilocularis hydatid cysts after ionizing radiation exposure

Background

Heavy-ion therapy has an advantage over conventional radiotherapy due to its superb biological effectiveness and dose conformity in cancer therapy. It could be a potential alternate approach for hydatid cyst treatment. However, there is no information currently available on the cellular and molecular basis for heavy-ion irradiation induced cell death in cystic echinococcosis.

Methododology/Principal Findings

LD50 was scored by protoscolex death. Cellular and ultrastructural changes within the parasite were studied by light and electron microscopy, mitochondrial DNA (mtDNA) damage and copy number were measured by QPCR, and apoptosis was determined by caspase 3 expression and caspase 3 activity. Ionizing radiation induced sparse cytoplasm, disorganized and clumped organelles, large vacuoles and devoid of villi. The initial mtDNA damage caused by ionizing radiation increased in a dose-dependent manner. The kinetic of DNA repair was slower after carbon-ion radiation than that after X-rays radiation. High dose carbon-ion radiation caused irreversible mtDNA degradation. Cysts apoptosis was pronounced after radiation. Carbon-ion radiation was more effective to suppress hydatid cysts than X-rays.

Conclusions

These studies provide a framework to the evaluation of attenuation effect of heavy-ion radiation on cystic echinococcosis in vitro. Carbon-ion radiation is more effective to suppress E. multilocularis than X-rays.

Surgical removal of cysts may be impractical in cases that cysts are in multiple organs or tissues, or in risky locations. In that case, alternative treatment should be employed. Heavy-ion radiation could be an effective way for treatment of hydatid cysts, taking its full advantage of well-defined range, small lateral beam spread and an enhanced biological effectiveness. In this study, we found that carbon-ion radiation could result in extensive mitochondrial DNA damage and apoptosis in hydatid cysts. Cellular and ultrastructural changes were observed after ionizing radiation, which were indicative of cysts growth inhibition. To our knowledge, this is the first study reporting the biological effect of carbon-ion radiation on E. multilocularis hydatid cysts.

Strategies of Echinococcus species responses to immune attacks: implications for therapeutic tool development

Echinococcus species have been studied as a model to investigate parasite-host interactions. Echinococcus spp. can actively communicate dynamically with a host to facilitate infection, growth and proliferation partially via secretion of molecules, especially in terms of harmonization of host immune attacks. This review systematically outlines our current knowledge of how the Echinococcus species have evolved to adapt to their host's microenvironment. This understanding of parasite-host interplay has implications in profound appreciation of parasite plasticity and is informative in designing novel and effective tools including vaccines and drugs for the treatment of echinococcosis and other diseases.

Fructose-bisphosphate aldolase and enolase from Echinococcus granulosus: genes, expression patterns and protein interactions of two potential moonlighting proteins

Glycolytic enzymes, such as fructose-bisphosphate aldolase (FBA) and enolase, have been described as complex multifunctional proteins that may perform non-glycolytic moonlighting functions, but little is known about such functions, especially in parasites. We have carried out in silico genomic searches in order to identify FBA and enolase coding sequences in Echinococcus granulosus, the causative agent of cystic hydatid disease. Four FBA genes and 3 enolase genes were found, and their sequences and exon-intron structures were characterized and compared to those of their orthologs in Echinococcus multilocularis, the causative agent of alveolar hydatid disease. To gather evidence of possible non-glycolytic functions, the expression profile of FBA and enolase isoforms detected in the E. granulosus pathogenic larval form (hydatid cyst) (EgFBA1 and EgEno1) was assessed. Using specific antibodies, EgFBA1 and EgEno1 were detected in protoscolex and germinal layer cells, as expected, but they were also found in the hydatid fluid, which contains parasite's excretory-secretory (ES) products. Besides, both proteins were found in protoscolex tegument and in vitro ES products, further suggesting possible non-glycolytic functions in the host-parasite interface. EgFBA1 modeled 3D structure predicted a F-actin binding site, and the ability of EgFBA1 to bind actin was confirmed experimentally, which was taken as an additional evidence of FBA multifunctionality in E. granulosus. Overall, our results represent the first experimental evidences of alternative functions performed by glycolytic enzymes in E. granulosus and provide relevant information for the understanding of their roles in host-parasite interplay.

Bovine (Bos taurus) humoral immune response against Echinococcus granulosus and hydatid cyst infertility

Echinococcus granulosus, the agent of hydatid disease, presents an indirect life cycle, with canines (mainly dogs) as definitive hosts, and herbivores and human as intermediary ones. In intermediary hosts fertile and infertile cysts develop, but only the first ones develop protoscoleces, the parasite form infective to definitive hosts. We report the presence of bovine IgGs in the germinal layer from infertile cysts (GLIC), in an order of magnitude greater than in the germinal layer from fertile cysts (GLFC). When extracted with salt solutions, bovine IgGs from GLIC are associated with low or with high affinity (most likely corresponding to non specific and antigen specific antibodies, respectively). Specific IgGs penetrate both the cells of the germinal layer and HeLa cultured cells and recognize parasitic proteins. These results, taken together with previous ones from our laboratory, showing induction of apoptosis in the germinal layer of infertile hydatid cysts, provide the first coherent explanation of the infertility process. They also offer the possibility of identifying the parasite antigens recognized, as possible targets for immune modulation.

Proteomic characterisation of Echinococcus granulosus hydatid cyst fluid from sheep, cattle and humans

The hydatid cyst fluid (HCF) of Echinococcus granulosus is a complex biological mixture containing a wide range of proteins of both parasite and host origin. Using a combination of in- and off-gel protein fractionation techniques and tandem mass spectrometry 130 HCF proteins were identified from fertile cysts of sheep and human origin and infertile cysts from cattle. Forty-eight proteins were of parasite origin including Antigen 5 and Antigen B--the most abundant parasite proteins, thioredoxin, low-density lipoprotein receptors, cyclophilin and ferritin. Across the three host species the identified HCF proteins were broadly similar although, based on spectral counts, three proteins, including an antigen B isoform, were more abundant in sheep HCF compared with the fluids of cattle and human origin. Eighty-two host proteins were identified in HCF from the three species. Host plasma proteins were the most abundant, although approximately thirty of the host proteins that were identified are not considered constituents of plasma. The identification of parasite heat shock proteins and annexin A13 exclusively in infertile cysts, along with an increased spectral count for cathepsin B, supports the hypothesis of increased cellular stress and apoptosis as the cause of their infertility.

DNA damage, RAD9 and fertility/infertility of Echinococcus granulosus hydatid cysts

Hydatidosis, caused by the larval stage of the platyhelminth parasite Echinococcus granulosus, affects human and animal health. Hydatid fertile cysts are formed in intermediate hosts (human and herbivores) producing protoscoleces, the infective form to canines, at their germinal layers. Infertile cysts are also formed, but they are unable to produce protoscoleces. The molecular mechanisms involved in hydatid cysts fertility/infertility are unknown. Nevertheless, previous work from our laboratory has suggested that apoptosis is involved in hydatid cyst infertility and death. On the other hand, fertile hydatid cysts can resist oxidative damage due to reactive oxygen and nitrogen species. On these foundations, we have postulated that when oxidative damage of DNA in the germinal layers exceeds the capability of DNA repair mechanisms, apoptosis is triggered and hydatid cysts infertility occurs. We describe a much higher percentage of nuclei with oxidative DNA damage in dead protoscoleces and in the germinal layer of infertile cysts than in fertile cysts, suggesting that DNA repair mechanisms are active in fertile cysts. rad9, a conserved gene, plays a key role in cell cycle checkpoint modulation and DNA repair. We found that RAD9 of E. granulosus (EgRAD9) is expressed at the mRNA and protein levels. As it was found in other eukaryotes, EgRAD9 is hyperphosphorylated in response to DNA damage. Our results suggest that molecules involved in DNA repair in the germinal layer of fertile hydatid cysts and in protoscoleces, such as EgRAD9, may allow preserving the fertility of hydatid cysts in the presence of ROS and RNS.

Morphological study of anomalous "laminated" brood capsules in cystic echinococcosis in humans and sheep

"Anomalous", as yet unreported forms of brood capsules (BC) in cystic echinococcosis larvae from humans and sheep are described, thought to be the likely effect of degenerative involution of the parasite. Morphological examination showed an inner laminated layer (LL) in the brood capsules in intimate contact with the internal wall surface, suggesting the term "laminated brood capsules" (LBC). Analysis conducted on LBC from cysts of different typology invariably revealed them to contain just dead and highly degenerated protoscoleces (PSC). Structural and ultrastructural aspects of these peculiar forms are described and possible processes of formation discussed. Comparison of germinal layer (GL), BC wall and PSC organization recognize a "tegumental" and a "non-tegumental" pole, coinciding in GL and PSC and inverted in BC. A quite reversible PSC-or-LL switch governed by complex mechanisms is proposed, of which PSC viability/death is assumed to be an essential part, that under certain conditions makes in vivo LL production inwards possible in BC.