In Vivo Imaging of Angiogenesis in 3D-Printed Bioactive Scaffolds
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Date
2017-05-08
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Johns Hopkins University
Abstract
Due to the complexities associated with bone regeneration and wound site
geometry, successful surgical reconstruction of craniomaxiofacial (CMF) injuries
remains challenging. To circumvent this issue, investigators have developed
paradigm-shifting tissue engineering and regenerative medicine (TERM) based
approaches to induce osteogenesis. One such approach involves the use of ‘bioactive’
scaffolds that are 3D-printed polyacrolaptone (PCL) grafts embedded with cells from
the human stromal vascular fraction (SVF) suspended in fibrin gel. However, since
bioactive grafts are usually tested under in vitro conditions, it is not known how
factors in the in vivo wound microenvironment such as oxygenation, angiogenesis and
perfusion affect the survival of SVF. Therefore, for this thesis we developed an in
vivo optical imaging pipeline to answer these questions in a preclinical calvarial bone
defect model. We used intrinsic optical signal (IOS) imaging to assess in vivo
angiogenesis and oxygenation, and used laser speckle contrast imaging (LSCI) to
assess in vivo perfusion within the implanted 3D scaffold. We also employed a
carbogen (95% oxygen, 5% carbon dioxide) gas challenge protocol to map ‘mature’
vasculature, and red fluorescent protein (RFP) imaging to track SVF distribution in
vivo. Finally, from this multimodality imaging data, we extracted quantitative metrics
that characterize the degree of angiogenesis, oxygenation, vascular maturity and
perfusion in vivo. We believe that the combination of in vivo optical imaging along
with TERM approaches can be exploited to produce patient-specific bone grafts. Such
an advance would revolutionize CMF reconstruction surgery and benefit a wide
variety of patients
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Keywords
Angiogenesis, Scaffold, Regenerative Medicine, Optical Imaging