Published online Jan 26, 2021. doi: 10.4252/wjsc.v13.i1.91
Peer-review started: July 12, 2020
First decision: September 24, 2020
Revised: November 1, 2020
Accepted: November 17, 2020
Article in press: November 17, 2020
Published online: January 26, 2021
A major problem in the healing of bone defects is insufficient or absent blood supply within the defect. To overcome this challenging problem, a plethora of approaches within bone tissue engineering have been developed recently. Bearing in mind that the interplay of various diffusible factors released by endothelial cells (ECs) and osteoblasts (OBs) have a pivotal role in bone growth and regeneration and that adjacent ECs and OBs also communicate directly through gap junctions, we set the focus on the simultaneous application of these cell types together with platelet-rich plasma (PRP) as a growth factor reservoir within ectopic bone tissue engineering constructs.
To vascularize and examine osteogenesis in bone tissue engineering constructs enriched with PRP and adipose-derived stem cells (ASCs) induced into ECs and OBs.
ASCs isolated from adipose tissue, induced in vitro into ECs, OBs or just expanded were used for implant construction as followed: BPEO, endothelial and osteogenic differentiated ASCs with PRP and bone mineral matrix; BPUI, uninduced ASCs with PRP and bone mineral matrix; BC (control), only bone mineral matrix. At 1, 2, 4 and 8 wk after subcutaneous implantation in mice, implants were extracted and endothelial-related and bone-related gene expression were analyzed, while histological analyses were performed after 2 and 8 wk.
The percentage of vascularization was significantly higher in BC compared to BPUI and BPEO constructs 2 and 8 wk after implantation. BC had the lowest endothelial-related gene expression, weaker osteocalcin immunoexpression and Spp1 expression compared to BPUI and BPEO. Endothelial-related gene expression and osteocalcin immunoexpression were higher in BPUI compared to BC and BPEO. BPEO had a higher percentage of vascularization compared to BPUI and the highest CD31 immunoexpression among examined constructs. Except Vwf, endothelial-related gene expression in BPEO had a later onset and was upregulated and well-balanced during in vivo incubation that induced late onset of Spp1 expression and pronounced osteocalcin immunoexpression at 2 and 8 wk. Tissue regression was noticed in BPEO constructs after 8 wk.
Ectopically implanted BPEO constructs had a favorable impact on vascularization and osteogenesis, but tissue regression imposed the need for discovering a more optimal EC/OB ratio prior to considerations for clinical applications.
Core Tip: For successful bone regeneration, osteogenesis and vasculogenesis should be supported by the appropriate combination of cells, growth factors and biomaterials (biological triad). Because the optimal triad composition is unknown, our aim was to combine endothelial and osteogenic differentiated adipose-derived stem cells in the same construct with platelet-rich plasma on bone mineral matrix as a carrier. This construct was examined in a mouse subcutaneous implantation model that enabled interplay between endothelial cells and osteoblasts in induction of ectopic osteogenesis. The results indicated the potential of this approach, but further preclinical evaluations in orthotopic model regarding optimization of ECs/OBs ratio are necessary.