Recent studies suggest that human adipose tissue contains pluripotent stem cells, which are similar to bone marrow-derived stem cells. The objective of the present study was to assess the effect in bone regenerating capability of human adipose-derived stem cells (ADSCs) cultured in osteogenic media layered over poly lactide-co-glycolic acid (PLGA) and implanted in a critical nude rat calvarial defect. Twenty-seven nude rats were randomized into 3 groups (n = 9): 1) PLGA alone (control), 2) PLGA with undifferentiated ADSCs, and 3) PLGA with differentiated ADSCs. These 3 groups were divided into 9 subgroups (n = 3) according to in vitro pre-cultured periods (day 1 pre-culture (Group1), day 7 pre-culture (Group2), and day 14 pre-culture (Group3)) before implantation. An 8 mm critical-size circular calvarial defect was made in each nude rat. Specimens were harvested at 12 weeks post-implantation and evaluated radiographically and histologically. Radiodensitometric analysis revealed significantly higher bone growth in implants pre-cultured in osteogenic media for 14 days for Group 3. Histomorphometric analysis demonstrated that Groups 2 and 3 had bone formation filling 35% to 72% of the area of the defect after transplantation with cells that had been pre-cultured for 14 days. Constructs with differentiated ADSCs (Group 3) had noticeably more maximal and robust bone tissue regeneration than constructs with undifferentiated ADSCs (Group 2). These data provide evidence that constructs or implants made of PLGA and osteogenically differentiated ADSCs pre-cultured for 14 days before transplantation have better, more-robust bone regeneration capability in critical-sized skeletal defects than constructs with undifferentiated ADSCs. Human adipose derived stem cells can therefore be used as seed cells to construct tissue-engineered bone.

Although many studies have suggested that human adipose tissue contains pluripotent stem cells, a few reports are available on stromal vascular fraction (SVF). In the present study, we evaluated the bone formation capacities of SVF. We implanted uncultured freshly isolated adipose-derived stem cells combined with demineralized bone matrix (DBM) to induce bone regeneration in a critically sized rat calvarial defect model. We used DBM (DBX(®)) and/or poly(70L-lactide-co-30DL-lactide) copolymer PLA as a scaffold. Fifty white rats were randomized to 5 different groups (n=10): (1) control, (2) DBM, (3) DBM + SVF, (4) DBM + PLA, and (5) DBM + PLA + SVF groups. After acquiring SVF, an 8-mm critically sized calvarial defect was made in each rat. Specimens were harvested at 8 weeks postimplantation and evaluated radiographically and histologically. New bone formation was qualified by hematoxylin and eosin staining and anti-osteocalcin antibody (OC4-30) immunostaining of calvarial sections. Amounts of mineralization were determined by radiodensitometric analysis. In gross appearance, the DBM + SVF and DBM + PLA + SVF groups showed more abundant bone formation than the other groups. Radiodensitometric evaluations revealed that significant intergroup differences were observed according to the Kruskal-Wallis (rank) test (P=0.030<0.05). The 5 groups show different amounts of filling of bone defects (control: 13.48%; DBM: 39.94%; DBM + SVF: 57.69%; DBM + PLA: 24.86%; DBM + PLA + SVF: 42.75%). Histological evaluation revealed that there was abundant new bone formation in the DBM + SVF and DBM + PLA + SVF groups. It was found that undifferentiated adipose-derived stem cells in the form of SVF induced new bone formation in rat calvarial defects. Accordingly, SVF offers a practical, promising candidate for regenerative tissue engineering or cell-based therapy.

These results suggest that PCL does not support the full expression of an osteoblastic phenotype by MC3T3-E1 cells. PCL, therefore, is less desirable as a scaffold polymer in bone tissue engineering in so far as supporting bone formation is concerned. However, because PCL has favorable handling characteristics and strength, modifications of PCL may prompt further investigation.

BMP-2, proven to alter polymer osteogenicity, remained bound to poly(lactic-co-glycolic acid), which may render poly(lactic-co-glycolic acid) an ideal choice as a polymer for scaffold-based bone tissue engineering using growth factor delivery.