Nacre, a natural, multi-use, and timely biomaterial for bone graft substitution.

During the past two decades, with a huge and rapidly increasing clinical need for bone regeneration and repair, bone substitutes are more and more seen as a potential solution. Major innovation efforts are being made to develop such substitutes, some having advanced even to clinical practice. It is now time to turn to natural biomaterials. Nacre, or mother-of-pearl, is an organic matrix-calcium carbonate coupled shell structure produced by molluscs. In vivo and in vitro studies have revealed that nacre is osteoinductive, osteoconductive, biocompatible, and biodegradable. With many other outstanding qualities, nacre represents a natural and multi-use biomaterial as a bone graft substitute. This review aims at summarising the current needs in orthopaedic clinics and the challenges for the development of bone substitutes; most of all, we systematically review the physiological characteristics and biological evidence of nacre's effects centred on osteogenesis, and finally we put forward the potential use of nacre as a bone graft substitute. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 662-671, 2017.

Subchondral nacre implant in the articular zone of the sheep's knee: a pilot study.

The present study was designed to analyze the intra-articular behaviour of nacre, when implanted in the subchondral bone area in the sheep knee. We implanted nacre blocks in sheep's trochlea by replacing the half of the femoral trochlea (nacre group). For comparison we used complete cartilage resection (resection group) down to the subchondral bone. In the "nacre group", implants were well tolerated without any synovial inflammation. In addition, we observed centripetal regrowth of new cartilage after 3 months. In the "resection group", no chondral regrowth was observed, but, in contrast, a thin layer of fibrous tissue was formed. After 6 months, a new tissue covered the nacre implant formed by an osteochondral regrowth. Nacre, as a subchondral implant, exerts benefic potential for osteochondral repair.