Many commonly used implant materials elicit a strong foreign body response, leading to the encapsulation and failure of the implant. A preferred healing response involves a minimal inflammatory response and ingrowth of blood vessels. Currently, normal practice for evaluating novel implants involves surgically implanting devices in experimental animals, harvesting implants at various time points, and performing histological evaluation. The overall goal of this project is to identify the role that blood vessels serve in the healing response of an implant, through non-destructive optical imaging. Optical coherence tomography (OCT) and confocal microscopy will provide a greatly increased amount of data for the same number of implantations performed, and will allow a single implant to be followed for multiple weeks, mitigating concerns about animal-to-animal and surgery-to-surgery variations. As a long-term clinical goal, noninvasive imaging may allow identification of the earliest vascular response to the implant and prediction of its success. There are three specific aims associated with this application:
Specific Aim 1. Evaluate the vascular response in glaucoma implant healing. Glaucoma implants offer an optically accessible model for implant healing. Both commercially available (Ahmed) and experimental expanded polytetrafluroethylene (ePTFE) implants will be placed in rabbit eyes with or without patches of ePTFE, pericardium or a scaffold-based three-dimensional human fibroblast culture. Time sequences of images will be acquired to determine the timing and degree of vascularization of the implants.
Specific Aim 2. Evaluate the healing of vascular implants. Intra- and extra-vascular OCT imaging will be performed of stents and grafts placed in the peripheral arteries of large animals. The proper functioning of the implant and adverse reactions such as neointimal hyperplasia will be measured. Blood flow shear rate measurements will be made at the boundaries of the implant and native artery. Evaluation of the vascularization of grafts by small capillaries will be performed.
Specific Aim 3. Expand OCT imaging capabilities through hardware and software developments.
This aim i ncludes developing miniature probes for intravascular and external use, increasing acquisition speed, and performing signal and image processing to measure perfusion, shear rate, and tissue image texture.
