Relating cell proliferation to in vivo bone formation in porous Ca/P scaffolds

Most current methods for cell monitoring on 3D porous scaffolds involve end-stage investigation of scaffolds. Repeated measurements on scaffolds, without disturbing cell vitality and proliferation, are needed to relate in vitro to in vivo data. Alamar Blue™ was used for this purpose. Two different Ca/P scaffolds were studied, using rat BMSCs with three different seeding densities [2.5 × 104 (SD1), 2.5 × 105 (SD2), 2.5 × 106 (SD3) cells]. Alamar Blue™ readings were done on days 1, 3, 5 and 7. After 7 days all 96 scaffolds (n = 16) were implanted in 16 mice for 4 weeks. Bone histomorphometry was performed. For both scaffolds, seeding efficiencies were highest with SD1 and SD2, cell proliferation was optimal in SD1, whereas SD3 resulted in an initial drop in vital cell number in the first 3 days. In vivo, upscaling from SD1 to SD2 lead to significantly more bone contact% in both scaffolds. Alamar Blue™ was shown to be a valuable tool in relating in vitro to in vivo data. Cell proliferation may differ depending on seeding density and scaffold type used. Seeding more cells may not necessarily result in more in vivo bone contact.