3D printed micro-chambers carrying stem cell spheroids and pro-proliferative growth factors for bone tissue regeneration

Abstract

Three-dimensional (3D)-printed scaffolds have proved to be effective tools for delivering growth factors and cells in bone-tissue engineering. However, delivering spheroids that enhance cellular function remains challenging because the spheroids tend to suffer from low viability, which limits bone regeneration in vivo. Here, we describe a 3D-printed polycaprolactone micro-chamber that can deliver human adipose-derived stem cell spheroids. An in vitro culture of cells from spheroids in the micro-chamber exhibited greater viability and proliferation compared with cells cultured without the chamber. We coated the surface of the chamber with 500 ng of platelet-derived growth factors (PDGFs), and immobilized 50 ng of bone morphogenetic protein 2 (BMP-2) on fragmented fibers, which were incorporated within the spheroids as a new platform for a dual-growth-factor delivery system. The PDGF detached from the chamber within 8 h and the remains were retained on the surface of chamber while the BMP-2 was entrapped by the spheroid. In vitro osteogenic differentiation of the cells from the spheroids in the micro-chamber with dual growth factors enhanced alkaline phosphatase and collagen type 1A expression by factors of 126.7 +/- 19.6 and 89.7 +/- 0.3, respectively, compared with expression in a micro-chamber with no growth factors. In vivo transplantation of the chambers with dual growth factors into mouse calvarial defects resulted in a 77.0 +/- 15.9% of regenerated bone area, while the chamber without growth factors and a defect-only group achieved 7.6 +/- 3.9% and 5.0 +/- 1.9% of regenerated bone areas, respectively. These findings indicate that a spheroid-loaded micro-chamber supplied with dual growth factors can serve as an effective protein-delivery platform that increases stem-cell functioning and bone regeneration.