Optical Molecular Tomography for Regenerative Medicine

Sponsor: NIH: NHLBI: R01 HL098912
Performance Period: 3/1/10-11/30/13
PI: Ge Wang, co-PIs: Chris Rylander, M. Nichole Rylander, and Yong Xu

The overall goal of this project is to develop a first-of-its-kind multi-probe, multi-modal optical molecular tomography (OMT) system for regenerative medicine and to demonstrate its utility in visualizing the real-time development of bioengineered blood vessels, both in bioreactors and after implantation into living animals. We will achieve the following aims:

Aim 1 – System Prototyping: Develop prototypes for hybrid optical molecular tomography to monitor bioengineered blood vessel constructs in bioreactors (in vitro prototype) and after implantation into sheep (in vivo prototype). We will employ fluorescent probes to label a cylindrical electrospun matrix scaffold and two cell types (vascular endothelial and smooth muscle cells). Optical fibers embedded in the scaffold will facilitate optical coherence tomography (OCT) and optical molecular tomography (OMT). The primary novelty of this multi-modal system lies in the enabling capabilities for multi-probe high-resolution analyses.

Aim 2 – Algorithm Development: Develop processing and reconstruction methods for the proposed optical molecular tomography system. Processing will be needed to minimize any excitation, measurement and reconstruction artifacts/noise. We will perform multi-spectral fluorescence tomography reconstructions based on our new phase-approximation model for photon transport. We will conduct systematic comparison in numerical simulation and tissue phantom experiments to optimize the imaging performance towards the design goals of 100μm 3D resolution in vitro and 500μm 3D resolution in vivo.

Aim 3 – In vitro Studies: Apply the imaging system to assess development of the bioengineered vessels in a pulsatile bioreactor for up to 30 days. We will investigate the endothelial coverage of the scaffold’s luminal surface, migration of smooth muscle cells in the scaffold’s porous outer compartment, and population dynamics of the two cell types. Fluorescent reporters will be utilized to monitor cell-type-specific gene expression in real-time, and to verify physiological responses of cells in the engineered vessel. We will validate optical molecular tomography results by comparison with conventional assays, including histology and measurements of specific mRNA and proteins.

Aim 4 – In vivo Studies: Apply the imaging system to assess the further development of bioengineered blood vessel constructs after anastomosis into the carotid arteries of sheep (up to 4 months). Features of interest to be analyzed are similar to those in vitro, and include scaffold remodeling, and the survival, continued growth and migration, and tissue-appropriate gene expression of cells initially seeded in the vessels. We will validate the OMT results by comparison with traditional histological, molecular, and physiological analyses.