Zebrafish Lab – Research Topic 1

The adult zebrafish is covered with dermal bone structures named “elasmoid scales” which mechanically protect the body. The scale is a bone plate structured with a plywood architecture much more similar to mammalian lamellar bone. The scale matrix is composed by fibrillary collagen and hydroxyapatite crystals in different proportion synthesized by the osteoblasts and remodeled by an osteoclast-mediated resorbing activity. Indeed, multinucleated osteoclasts resorbing the scale matrix have also been identified by means of electron microscopy in fish in physiological and pathological conditions.

Scales can be removed with a forceps without causing suffering in fish and a new scale is regenerated in approximately 14 days. Explanted scale can be used as read out system for bone metabolism evaluating biochemical and cellular markers, bone matrix architecture and deposition. To do that, several assays can be performed such as biochemical assays for enzymatic activity, histochemical staining with calcein (topic1_image1) and/or alizarin red, immunohistochemical staining with antibodies, gene expression evaluation by real-time PCR. A live double staining with alizarin red and calcein (topic1_image2) has been recently developed to measure the mineralization rate of the scale after treatment with chemical compounds or drugs. The transparency and the size of the scale facilitates manipulation, treatment and observation of the results under a stereo-microscope.