Cellular organization and appearance of differentiated structures in developing stages of the parasitic platyhelminthEchinococcus granulosus

Abstract

Echinococcus granulosus is the causative agent of hydatidosis, a major zoonoses that affects humans and herbivorous domestic animals. The disease is caused by the pressure exerted on viscera by hydatid cysts that are formed upon ingestion of E. granulosus eggs excreted by canine. Protoscoleces, larval forms infective to canine, develop asynchronously and clonally from the germinal layer (GL) of hydatid cysts. In this report, we describe the cellular organization and the appearance of differentiated structures both in nascent buds and developed protoscoleces attached to the GL. Early protoscolex morphogenesis is a highly complex and dynamic process starting from the constitution of a foramen in the early bud, around which nuclei are distributed mainly at the lateral and apical regions. Similarly, distribution of nuclei in mature protoscoleces is not homogenous but underlies three cellular territories: the suckers, the rostellar pad, and the body, that surrounds the foramen. Several nuclei are associated to calcareous corpuscles (Cc), differentiated structures that are absent in the earlier bud stages. The number of nuclei is similar from the grown, elongated bud stage to the mature protoscolex attached to the GL, strongly suggesting that there is no significant cellular proliferation during final protoscolex development. The amount of DNA per nucleus is in the same range to the one described for most other platyhelminthes. Our results point to a sequential series of events involving cell proliferation, spatial cell organization, and differentiation, starting in early buds at the GL of fertile hydatid cysts leading to mature protoscoleces infective to canine.

Biology and Systematics of Echinococcus

“…Cell proliferation derives from the continuous replicative activity of these dividing stem cells located in the germinal layer of the metacestode or neck region of the adult worm (Galindo et al, 2003;Gustafsson, 1976). They have considerable proliferative potential Galindo et al, 2003;Martínez et al, 2005;Mehlhorn et al, 1983) and are the only proliferating cells in Echinococcus . This is particularly well illustrated by the capacity of the parasite for indefinite perpetuation in the larval stage by the passage of protoscoleces or germinal layer material in rodents (secondary hydatidosis; Howell and Smyth, 1995).…”

Morphological and biological characterization of cell line developed from bovine Echinococcus granulosus

“…There is also information on how in nascent pe. nuclei are concentrated in suckers and in rostelar pads and hooks, while in mature pe., nuclei are found adjacent to the tegument, and no cell proliferation is observed after grown buds elongate (Martínez et al 2005). Moreover, greater proliferative activity was described in pe.…”

The study of apoptotic bifunctional effects in relationship between host and parasite in cystic echinococcosis: a new approach to suppression and survival of hydatid cyst

“…Additionally, potential source of infection is carrot juice that nearly in every place is sold in combination with ice cream (Rokni 2008). The hydatid cyst layers from inner to outer are composed an inner cellular germinal layer that is supported by a chitin-like non-cellular laminated layer that is surrounded by a host-produced fibrous layer (Bortoletti and Ferretti 1978;Martinez et al 2005). Oncospheres hatching from eggs migrate to the liver and several organs of the intermediate hosts such as man and developed into hydatid cysts in a few weeks.…”