ABSTRACT
Objective:To construct a novel biomimetic calcium phosphate (BioCaP) scaffold loaded with bone morphogenetic protein-2 (BMP-2),and to investigate its role in the osteogenesis of human adipose-derived stem cells (hASCs) in vitro and in vivo.Methods:The BioCaP scaffold coprecipitated with BMP-2 (BMP-2-BioCaP) was constructed in this study.Field emission scanning electron microscopy (SEM) was used to analyze the morphology of the surfaces.The release kinetics was measured to evaluate the slow-release characteristics in vitro.BMP-2-BioCaP was immersed in proliferation medium (PM) or osteogenic medium (OM),respectively.The supernatants were collected and used to culture hASCs in vitro.Cell numbers were determined using the cell-counting kit-8 (CCK-8) to assess the cell proliferation.After 7 and 14 days,alkaline phosphatase (ALP) staining and quantification were performed to test the activity of ALP.After 14 and 21 days,the calcification deposition was determined by alizarin red S (ARS) staining and quantification.The expressions of the osteoblast-related genes were tested on day 4 and day 14.In the in vivo study,6 nude mice were used and implanted subcutaneously into the back of the nude mice for 4 groups:(1) BioCaP scaffold only,(2) BioCaP scaffold + hASCs,(3) BMP-2-BioCaP scaffold,(4) BMP-2-BioCaP scaffold + hASCs (test group).After 4 weeks of implantation,hematoxylin-eosin (HE) staining was performed to evaluate the in vivo osteogenesis of hASCs.Results:SEM observations showed that BioCaP and BMP-2-BioCaP scaffold were entirely composed of straight,plate-like and sharp-edged crystal units,and the length of the crystal units varied between 5 and 10 μm.Release kinetics analysis demonstrated that BMP-2 incorporated with BioCaP could be released at certain concentration and last for more than 21 days,and the accumulative protein release could reach 20％.CCK-8 assays showed that cell proliferation was not significantly affected by BMP-2BioCaP.ALP activity was higher by the induction of OM + BMP-2-BioCaP than of the other groups (P ＜0.01).More mineralization deposition and more expressions of osteoblast-related genes such as Runt-related transcription factor 2 (RUNX2),ALP,osteopontin (OPN) and osteocalcin (OC) were determined in the OM + BMP-2-BioCaP group at different time points (P ＜0.01).HE staining showed that,in the test group and BMP-2-BioCaP scaffold group,the extracellular matrix (ECM) with eosinophilic staining were observed around hASCs,and newly-formed bone-like tissues could be found in ECM around the scaffold materials.Moreover,compared with the BMP-2-BioCaP scaffold group,more bone-like tissues could be observed in ECM with typical structure of bone tissue in the test groups.No obvious positive results were found in the other groups.Conclusion:BMP-2-BioCaP scaffold could achieve slow-release of BMP-2 and promote the osteogenic differentiation of hASCs in vitro and in vivo.The novel tissue-engineered bone composed of hASCs and BMP-2-BioCaPis promising for the repair of bone defect.
ABSTRACT
Objective:To construct and evaluate a novel tissue-engineered bone composed of murine stromal cell-derived factor 1(mSDF-1), simvastatin (SIM) and collagen scaffold (Bio-Oss?), serving as a cell-homing approach for bone formation .Methods: In the study , 32 ICR mice were randomly divided into 4 groups,each group including 8 mice.The drug-loaded collagen scaffolds were implanted subcutaneously onto the cranium of each mouse according to the groups: ( 1 ) 1 ∶50 ( volume ratio ) dimethyl sulfoxide ( DMSO ) /phosphate-buffered saline ( PBS ) solution +collagen scaffold ( blank control group ); ( 2 ) 10 -3 mol/L SIM solution +collagen scaffold ( SIM group ); ( 3 ) 200 mg/L mSDF-1solution +collagen scaffold (mSDF-1 group); and (4) 10 -3mol/L SIM +200 mg/L mSDF-1 solution +collagen scaffold ( SIM +mSDF-1 group) .One week after implantation , the mice were trea-ted by injecting the same drug solution mentioned above around the scaffold once a day for two days .The specimens were harvested 6 weeks after implantation and the bone formation was evaluated by soft X-ray analysis , HE staining and immunohistochemical staining .Angiogenesis of each group was checked by calculation of vessels in each tissue section .Results:Six weeks after implantation , the collagen scaffolds were retrieved.The value of gray scale for the SIM +mSDF-1 group[(421 836.5 ±65 425.7) pixels] was significantly higher than that of the blank control group [(153 345.6 ±45 222.2)pixels, P<0.01], the SIM group [(158 119.2 ±100 284.2) pixels, P<0.01], and the mSDF-1 group[(255 529.5 ± 152 142.4) pixels, P <0.05 ]; HE staining analysis revealed that significant bone formation was achieved in the SIM +mSDF-1 group; The immunohistochemical staining showed the existence of os-teopontin and osteocalcin in the SIM +mSDF-1 group; There were more vessels in the SIM +mSDF-1 group[(46 ±8)vessels/mm2] than in the blank control group [(23 ±7) vessels/mm2, P<0.01], and the SIM group[(24 ±6) vessels/mm2 , P<0.01].Conclusion:The novel tissue-engineered bone com-posed of mSDF-1, SIM and collagen scaffolds has the potential to form bone subcutaneously in vivo.It re-presents a novel method of in vivo bone re-generation without seed cell delivery .