3D Printing of Cell-Container-Like Scaffolds for Multicell Tissue Engineering

The development of an engineered non-contact multicellular coculture model that can mimic the in v iv o cell microenvironment of human tissues remains challenging.In this study,we successfully fabricated a cell-container-like scaffold composed of p-tricalcium phosphate/hydroxyapatite(p-TCP/HA)bioceramic that contains four different pore structures,including triangles,squares,parallelograms,and rectangles,by means of three-dimensional(3D)printing technology.These scaffolds can be used to simultaneously culture four types of cells in a non-contact way.An engineered 3D coculture model composed of human bone-marrow-derived mesenchymal stem cells(HBMSCs),human umbilical vein endothelial cells(HUVECs),human umbilical vein smooth muscle cells(HUVSMCs),and human dermal fibroblasts(HDFs)with a spatially controlled distribution was constructed to investigate the individual or synergistic effects of these cells in osteogenesis and angiogenesis.The results showed that three or four kinds of cells cocultured in 3D cell containers exhibited a higher cell proliferation rate in comparison with that of a single cell type.Detailed studies into the cell-cell interactions between HBMSCs and HUVECs revealed that the 3D cell containers with four separate spatial structures enhanced the angiogenesis and osteogenesis of cells by amplifying the paracrine effect of the cocultured cells.Furthermore,the establishment of multicellular non-contact systems including three types of cells and four types of cells,respectively,cocultured in 3D cell containers demonstrated obvious advantages in enhancing osteogenic and angiogenic differentiation in comparison with monoculture modes and two-cell coculture modes.This study offers a new direction for developing a scaffold-based multicellular non-contact coculture system for tissue regeneration.

Co-delivery of rhBMP-2 and zoledronic acid using calcium sulfate/hydroxyapatite carrier as a bioactive bone substitute to enhance and accelerate spinal fusion

Recombinant human bone morphogenetic protein-2(rhBMP-2)has been FDA-approved for lumbar fusion,but supraphysiologic initial burst release due to suboptimal carrier and late excess bone resorption caused by osteoclast activation have limited its clinical usage.One strategy to mitigate the pro-osteoclast side effect of rhBMP-2 is to give systemic bisphosphonates,but it presents challenges with systemic side effects and low local bioavailability.The aim of this in vivo study was to analyze if posterolateral spinal fusion(PLF)could be improved by utilizing a calcium sulfate/hydroxyapatite(CaS/HA)carrier co-delivering rhBMP-2 and zoledronic acid(ZA).Six groups were allocated(CaS/HA,CaS/HA+BMP-2,CaS/HA+systemic ZA,CaS/HA+local ZA,CaS/HA+BMP-2+systemic ZA,and CaS/HA+BMP-2+local ZA).10-week-old male Wistar rats,were randomly assigned to undergo L4-L5 PLF with implantation of group-dependent scaffolds.At 3 and 6 weeks,the animals were euthanized for radiography,μCT,histological staining,or biomechanical testing to evaluate spinal fusion.The results demonstrated that the CaS/HA biomaterial alone or in combination with local or systemic ZA didn’t support PLF.However,the delivery of rhBMP-2 significantly promoted PLF.Combining systemic ZA with rhBMP-2 didn’t enhance spinal fusion.Notably,the co-delivery of rhBMP-2 and ZA using the CaS/HA carrier significantly enhanced and accelerated PLF,without inhibiting systemic bone turnover,and potentially reduced the dose of rhBMP-2.Together,the treatment regimen of CaS/HA biomaterial co-delivering rhBMP-2 and ZA could potentially be a safe and cost-effective off-the-shelf bioactive bone substitute to enhance spinal fusion.