Movers and shakers: evolution and development of the mesoderm

Reptile Embryology and Regeneration

Reptiles (lizards, snakes, turtles, and crocodilians) are becoming increasingly popular as models for developmental investigations. In this review the leopard gecko, Eublepharis macularius, is presented as a reptilian model for embryonic and tissue regeneration studies. We provide details of husbandry and breeding and discuss aspects of embryonic nutrition, egg anatomy, and sex determination. We provide comprehensive protocols for transcardial perfusion, short-term anesthesia using the injectable anesthetic Alfaxan, and full-thickness cutaneous biopsy punches, used in geckos for the study of scar-free wound healing. We also provide modifications to three popular histological techniques (whole-mount histochemistry, immunohistochemistry, and double-label immunofluorescence) and provide details on bromodeoxyuridine (BrdU) labeling and immuno-detection.

[Dental pulp stem cells: characteristics, cryopreservation and therapeutic potentialities]

Stem cells discovery and their potential have led to the emergence of new forms of therapy with the development of bio-engineering cell and tissue methods underlying future medicine. The availability of stem cells and their preservation thus become an issue for everyone's health. Among the different sources of stem cells, those in the dental pulp have the advantage of being pluripotent, they can be cryopreserved and stored for long periods without losing their multiplication and differentiation capacities and finally they are easily accessible. The wisdom or natal teeth extracted for medical reasons are an opportunity for everyone to preserve stem cells for an autologous use. Biobanks authorized and specialized in the preparation and storage of pulp stem cells provide access to autologous regenerative medicine of tomorrow.

Osteoblastic/cementoblastic and neural differentiation of dental stem cells and their applications to tissue engineering and regenerative medicine

Recently, dental stem and progenitor cells have been harvested from periodontal tissues such as dental pulp, periodontal ligament, follicle, and papilla. These cells have received extensive attention in the field of tissue engineering and regenerative medicine due to their accessibility and multilineage differentiation capacity. These dental stem and progenitor cells are known to be derived from ectomesenchymal origin formed during tooth development. A great deal of research has been accomplished for directing osteoblastic/cementoblastic differentiation and neural differentiation from dental stem cells. To differentiate dental stem cells for use in tissue engineering and regenerative medicine, there needs to be efficient in vitro differentiation toward the osteoblastic/cementoblastic and neural lineage with well-defined and proficient protocols. This would reduce the likelihood of spontaneous differentiation into divergent lineages and increase the available cell source. This review focuses on the multilineage differentiation capacity, especially into osteoblastic/cementoblastic lineage and neural lineages, of dental stem cells such as dental pulp stem cells (DPSC), dental follicle stem cells (DFSC), periodontal ligament stem cells (PDLSC), and dental papilla stem cells (DPPSC). It also covers various experimental strategies that could be used to direct lineage-specific differentiation, and their potential applications in tissue engineering and regenerative medicine.

Reptile embryology

Reptiles (lizards, snakes, turtles and crocodylians) are becoming increasing popular as models for developmental investigations. In this review the leopard gecko, Eublepharis macularius, is presented as a reptilian model for embryonic studies. We provide details of husbandry, breeding and modifications to two popular histological techniques (whole-mount histochemistry and immunohistochemistry). In addition, we provide a summary of basic reptilian husbandry requirements and discuss important details of embryonic nutrition, egg anatomy and sex determination.

The role of β-sheets in the structure and assembly of keratins

X-ray diffraction, infrared and electron microscope studies of avian and reptilian keratins, and of stretched wool and hair, have played a central role in the development of models for the β-conformation in proteins. Both α- and β-keratins contain sequences that are predicted to adopt a β-conformation and these are believed to play an important part in the assembly of the filaments and in determining their mechanical properties. Interactions between the small β-sheets in keratins provide a simple mechanism through which shape and chemical complementarity can mediate the assembly of molecules into highly specific structures. Interacting β-sheets in crystalline proteins are often related to one another by diad symmetry and the data available on feather keratin suggest that the filament is assembled from dimers in which the β-sheets are related by a perpendicular diad. The most detailed model currently available is for feather and reptilian keratin but the presence of related β-structural forms in mammalian keratins is also noted.

Hatching time for monotreme immunology

The sequencing of the platypus genome has spurred investigations into the characterisation of the monotreme immune response. As the most divergent of extant mammals, the characterisation of the monotreme immune repertoire allows us to trace the evolutionary history of immunity in mammals and provide insights into the immune gene complement of ancestral mammals. The immune system of monotremes has remained largely uncharacterised due to the lack of specific immunological reagents and limited access to animals for experimentation. Early immunological studies focussed on the anatomy and physiology of the lymphoid system in the platypus. More recent molecular studies have focussed on characterisation of individual immunoglobulin, T-cell receptor and MHC genes in both the platypus and short-beaked echidna. Here, we review the published literature on the monotreme immune gene repertoire and provide new data generated from genome analysis on cytokines, Fc receptors and immunoglobulins. We present an overview of key gene families responsible for innate and adaptive immunity including the cathelicidins, defensins, T-cell receptors and the major histocompatibility complex (MHC) Class I and Class II antigens. We comment on the usefulness of these sequences for future studies into immunity, health and disease in monotremes.