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. 2014 Sep 22;3(11):1363–1374. doi: 10.5966/sctm.2014-0017

Figure 3.

Figure 3.

Mineralization in the chick fetal femur at the sites of microinjection. (A–D): Bone collars and secondary mineralization sites (green) within the cartilaginous chick fetal femur (white) showing the location and extent of mineralization following sham injection (A), exposure to magnetic bioreactor alone (B), injection of hMSCs (C), and injection of hMSCs followed by exposure to the magnetic bioreactor (D). (E, F): The addition of magnetic nanoparticles coated with RGD tripeptide (E) or TREK-Ab (F) resulted in mineralization at the epiphyseal injection sites. (G, H): Femurs injected with hMSCs prelabeled with either RGD-coated (G) or TREK-Ab-coated (H) magnetic nanoparticles showed the greatest extent of mineralization. Most femurs (including sham-injected femurs) displayed a secondary mineralization site in the epiphysis at the site of injection, whereas the diaphyseal injection site was not visible in any femur after 2 weeks of organotypic ex vivo culture. (I, J): After 14 days of in vitro culture, femurs injected with either phosphate-buffered saline (sham) or exposed to the oscillating magnetic bioreactor alone showed similar alkaline phosphatase activity (I) and mineralization (J) to injections of hMSCs and injections of RGD-coated magnetic nanoparticles alone. Injecting TREK-Ab-coated magnetic nanoparticles or hMSCs pretagged with either RGD or TREK nanoparticles caused significant increases in the extent of mineralization in the femur (J), and tagged cells exhibited more alkaline phosphatase activity (I). Arrows show the locations of the epiphyseal injections. Bars show standard error of the mean (n = 3 for alkaline phosphatase; n = 9 for x-ray microtomography). ∗, p < .05. Scale bars = 1 mm. Abbreviations: hMSC, human mesenchymal stem cells; PNP, p-nitrophenyl phosphate; RGD, Arg-Gly-Asp tripeptide.