Viable cells survive in fresh frozen human bone allografts

Abstract

Background Fresh frozen bone allograft is available for human recipients after at least 6 months of quarantine at –80°C. It is assumed that cryopreservation without cryoprotectant removes all viable donor cells. Methods We studied the in vitro cell growth from samples of fresh frozen human femoral head allografts after they had been released for patient use, and compared it with cell growth from a control group of fresh cancellous bone specimens from excised femoral heads (8 samples in each group). Results Cell outgrowths were seen in all of the fresh cancellous bone specimens (100% of replicates, 48 replicates per specimen) but only in a small minority of replicates from 4 of the allograft samples (mean 3.1%). Reverse transcription quantitative polymerase chain reaction (RT-qPCR) investigations revealed that cell outgrowths from both groups contained mRNA for transcription factors Runx2 and Osterix, and also for matrix proteins collagen type I, osteocalcin and bone sialoprotein. This is consistent with the cells being osteoblast-related. Interpretation This study confirms that fresh frozen human bone allograft cells have the potential to grow in vitro, but the significance of this in recipients is currently unknown.