Effect of Adipose Tissue-Derived Osteogenic and Endothelial Cells on Bone Allograft Osteogenesis and Vascularization in Critical-Sized Calvarial Defects

Abstract

The use of processed bone allograft to repair large osseous defects of the skull has been limited, given that it lacks the osteogenic cellularity and intrinsic vascular supply which are essential elements for successful graft healing and, at the same time, the areas to be targeted through tissue-engineering applications. In this study, we investigated the effect of predifferentiated rat adipose tissue-derived osteoblastic cells (OBs) and endothelial cells (ECs) on calvarial bone allograft healing and vascularization using an orthotopic critical-sized calvarial defect model. For this purpose, thirty-seven 8 mm critical calvarial defects in Lewis rats were treated with bone allografts seeded with no cells, undifferentiated adipose tissue-derived stem cells (ASC), OBs, ECs, and OBs and ECs simultaneously. After 8 weeks, the bone volume and mineral density were calculated using microcomputed tomography and the microvessel formation using immunohistochemical staining and imaging software. The amount of bone within the 8 mm defect was significantly higher for the allografts treated with ECs compared with the allografts treated with OBs (p=0.05) and simultaneously with the two cell lineages (p=0.02). There were no significant differences in bone formation between the latter two groups and the control groups (allografts treated with no cells and undifferentiated ASC). There were no significant differences in bone mineral density among the groups. The amount of microvessels was significantly higher in the group treated with ECs relative to all groups (p=< 0.05). Our results show that the implantation of ASC-derived ECs improves the vascularization of calvarial bone allografts at 8 weeks after treatment. This cell-based vascularization strategy can be used to improve the paucity of perfusion in allogenic bone implants. However, in this study, the treatment of allografts with OBs alone or in combination with ECs did not support bone formation or vascularization.

Oral Mucosa Harbors a High Frequency of Endothelial Cells: A Novel Postnatal Cell Source for Angiogenic Regeneration

“…Our preliminary study shows that there is a synergistic effect between ECs (HUVECs) and MSCs in promoting bone regeneration when implanted at the fracture gap of the large bone defects created by osteotomy at the tibial epiphysis of host recipients (orthotopic implantation) (preliminary data). These results are consistent with previous studies [60,62]. However, since HUVECs are not postnatal cells, their clinical relevance is unclear.…”

“…Investigators, including our group, have recently started to examine the potential of ECs (or EPCs) to treat criticalsized bone defects, either on their own [10,58,59] or in combination with MSCs [60][61][62][63]. Our preliminary study shows that there is a synergistic effect between ECs (HUVECs) and MSCs in promoting bone regeneration when implanted at the fracture gap of the large bone defects created by osteotomy at the tibial epiphysis of host recipients (orthotopic implantation) (preliminary data).…”

Comparison of Endothelial Differentiation Capacities of Human and Rat Adipose-Derived Stem Cells

“…10,[13][14][15][16][17][18][19][20] However, it is still not clear whether human adipose-derived stem cells have the endothelial differentiation capacity that might be of clinical significance, under the same differentiation conditions.…”

Toll-Like Receptor 4 Mediates the Regenerative Effects of Bone Grafts for Calvarial Bone Repair

“…Thus, grafts were considered to be allogeneic in source. [31][32][33][34] Allogeneic bone is frequently employed as a decellularized graft material, but is generally inferior to autologous bone graft and exhibits inferior remodeling upon implantation. Coating of structural allografts with RANKL and VEGF resulted in marked remodeling, improved vascularization, and enhanced bone repair, however, suggesting an essential role for remodeling in forming bony unions between grafts and host bone tissue.…”