Survival of Transplanted Rat Bone Marrow-Derived Osteogenic Stem Cells In Vivo

This study was designed to trace bone marrow-derived stromal cells (MSC) after implantation in an ectopic rat model of bone tissue engineering. MSC were isolated from adult donor rats, expanded, seeded on a hydroxyapatite/β-tricalcium phosphate bone graft substitute (Straumann ® BoneCeramic), and cultivated until confluent. Before subcutaneous implantation of seeded constructs and controls (unseeded bone graft substitute) in isogenic rats ( n = 32), cells were labeled with the fluorescent dye carboxyfluoresceine-diacetate-succinimidyl-ester. Specimens were harvested at sacrifice on day 1, 3, 7, or 14 after implantation ( n = 8 per group) and processed for histology (hematoxylin and eosin, CD68, 4′,6-diamidino-2-phenylindol). Carboxyfluoresceine-diacetate-succinimidyl-ester-labeled transplanted cells were quantified in decalcified sections (50 fields of view per specimen) at 488 nm. Over time, transplanted cells decreased in number from 31.3 ± 2.3 (day 1) to 9.2 ± 1.1 (day 3) and 0.3 ± 0.1 (day 7) ( p