Vascularized Bone-Mimetic Hydrogel Constructs by 3D Bioprinting to Promote Osteogenesis and Angiogenesis

Takahisa Anada,Yunzhi Yang,Chi-Chun Pan,Junji Fukuda,Alexander Stahl,Osamu Suzuki,Satomi Mori

doi:10.3390/ijms20051096

Abstract

Bone is a highly vascularized tissue with a unique and complex structure. Long bone consists of a peripheral cortical shell containing a network of channels for vascular penetration and an inner highly vascularized bone marrow space. Bioprinting is a powerful tool to enable rapid and precise spatial patterning of cells and biomaterials. Here we developed a two-step digital light processing technique to fabricate a bone-mimetic 3D hydrogel construct based on octacalcium phosphate (OCP), spheroids of human umbilical vein endothelial cells (HUVEC), and gelatin methacrylate (GelMA) hydrogels. The bone-mimetic 3D hydrogel construct was designed to consist of a peripheral OCP-containing GelMA ring to mimic the cortical shell, and a central GelMA ring containing HUVEC spheroids to mimic the bone marrow space. We further demonstrate that OCP, which is evenly embedded in the GelMA, stimulates the osteoblastic differentiation of mesenchymal stem cells. We refined the design of a spheroid culture device to facilitate the rapid formation of a large number of HUVEC spheroids, which were embedded into different concentrations of GelMA hydrogels. It is shown that the concentration of GelMA modulates the extent of formation of the capillary-like structures originating from the HUVEC spheroids. This cell-loaded hydrogel-based bone construct with a biomimetic dual ring structure can be potentially used for bone tissue engineering.

Highlights

Large bone defects caused by trauma, tumor resection and osteomyelitis have difficulty healing spontaneously
We demonstrated that 3D culture using the spheroid culture device is useful for the maintenance of the function of hepatocytes [23] and the osteoblastic differentiation of mesenchymal stem cells [24]
We found that sprout formations from human umbilical vein endothelial cells (HUVEC) spheroids were affected by the concentration of gelatin methacrylate (GelMA)

Summary

Introduction

Large bone defects caused by trauma, tumor resection and osteomyelitis have difficulty healing spontaneously. Biomaterials can be used for the treatment of bone defects instead of an autogenous bone graft. When bone substitute materials are implanted in large bone defects, insufficient vascularization often causes poor bone regeneration, because bone is a highly vascularized tissue [1]. Achieving early blood vessel formation in large bone grafts to supply nutrition and oxygen still presents a challenge. As the growth of blood vessels in bone and osteogenesis are coupled [2,3], many groups reported prevascularization strategies for bone substitutes using growth factors [4,5], and endothelial cells [6,7]. Bioprinting, which can build three-dimensional (3D) constructs using cells, proteins and biomaterials, is expected to be a powerful tool for the field of bone tissue engineering [8]. We have already shown that the DLP-based SLA is a very useful technique for the fabrication of the 3D bifurcating tubular structures consisting of cell-laden hydrogels [10]

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Conclusion