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Raw nacre implants persist even after 9 months of implantation into bone tissue in sheep. However the nacre surface undergoes a limited biodegradation process. Smooth-surfaced nacre implants were seen to become microporous after implantation. The results of these long-term, in vivo studies show that the overall process involves bone-resorbing cells, relies on a two-phase mechanism and may correspond to a regulation process. The rate of surface change depends on the bone implantation site and the nacre/bone interaction. The in vivo biodegradability of nacre is a highly variable parameter. The size and shape of the implanted nacre and the cellular environment of the implant are key factors in determining the biodegradation kinetics of the nacre in a living system.

Organic matrix from molluscan shells has the potential to regulate calcium carbonate deposition and crystallization. Control of crystal growth thus seems to depend on control of matrix protein secretion or activation processes in the mantle cells, about which little is known. Biomineralization is a highly orchestrated biological process. The aim of this work was to provide information about the source of shell matrix macromolecule production, within the external epithelium of the mantle. An in vivo approach was chosen to describe the histologic changes in the outer epithelium and in blood sinus distribution, associated with mantle cells implicated in shell matrix production. Our results characterized a topographic and time-dependent zonation of matrix proteins involved in shell biomineralization in the mantle of Haliotis.