title: Brief review of models of ectopic bone formation.
abstract: Ectopic bone formation is a unique biologic entity--distinct from other areas of skeletal biology. Animal research models of ectopic bone formation most often employ rodent models and have unique advantages over orthotopic (bone) environments, including a relative lack of bone cytokine stimulation and cell-to-cell interaction with endogenous (host) bone-forming cells. This allows for relatively controlled in vivo experimental bone formation. A wide variety of ectopic locations have been used for experimentation, including subcutaneous, intramuscular, and kidney capsule transplantation. The method, benefits and detractions of each method are summarized in the following review. Briefly, subcutaneous implantation is the simplest method. However, the most pertinent concern is the relative paucity of bone formation in comparison to other models. Intramuscular implantation is also widely used and relatively simple, however intramuscular implants are exposed to skeletal muscle satellite progenitor cells. Thus, distinguishing host from donor osteogenesis becomes challenging without cell-tracking studies. The kidney capsule (perirenal or renal capsule) method is less widely used and more technically challenging. It allows for supraphysiologic blood and nutrient resource, promoting robust bone growth. In summary, ectopic bone models are extremely useful in the evaluation of bone-forming stem cells, new osteoinductive biomaterials, and growth factors; an appropriate choice of model, however, will greatly increase experimental success.
authors.affiliation: Orthodontics and Dentofacial Orthopedics, Roseman University of Health Sciences, Henderson, Nevada, USA.
authors.forename: Michelle A
authors.initials: MA
authors.lastname: Scott
authors.forename: Benjamin
authors.initials: B
authors.lastname: Levi
authors.forename: Asal
authors.initials: A
authors.lastname: Askarinam
authors.forename: Alan
authors.initials: A
authors.lastname: Nguyen
authors.forename: Todd
authors.initials: T
authors.lastname: Rackohn
authors.forename: Kang
authors.initials: K
authors.lastname: Ting
authors.forename: Chia
authors.initials: C
authors.lastname: Soo
authors.forename: Aaron W
authors.initials: AW
authors.lastname: James
mesh_terms: D000818:Animals; D001842:Bone and Bones; D002828:Choristoma / Q000473:pathology*; D004195:Disease Models, Animal; D006801:Humans; D007674:Kidney Diseases / Q000473:pathology*; D009135:Muscular Diseases / Q000473:pathology*; D019736:Prostheses and Implants; D012871:Skin Diseases / Q000473:pathology*
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