The sponge as a model of cellular recognition

Abstract

Sponges, the simplest extant Metazoans, have been traditionally used as models to study cell adhesion, since their abundant extracellular matrix allows a mild cell dissociation and the recovery of functionally active macromolecular structures. Dissociated sponge cells quickly reaggregate in a species-specific manner, differentiate, and reconstruct tissue, providing a simple model to investigate the molecular basis of animal intercellular recognition systems. Here, we review the application of sponges as biotools for the study of three cell recognition processes that are relevant for biomedical research. First, the species-specific association of sponge cells is discussed in the context of the role ascribed to carbohydrates in adhesion-related phenomena implicated, among other processes, in tumor metastasis. Second, we will summarize the current knowledge about a sponge proteoglycan that has been proposed as a model for the investigation of the mechanical properties of extracellular matrix proteoglycans in calcium-dependent cell adhesion events, whose impairment can lead to severe disorders such as Alzheimer's disease and Marfan syndrome. Finally, the self-nonself recognition reactions in sponges are presented as a window to the early period in the evolution of histocompatibility systems, and the corresponding molecular and cellular events will be compared with the processes and cells known to be involved in innate immunity and in placental implantation. Potential important applications of sponges in the search for new pharmaceuticals and in key biomedical areas such as stem cell research are just around the corner awaiting the development of sponge cell cultures. © 2008 Humana Press Inc.