Design of a noninvasive system for the evaluation of collagen scaffolds using MRI

by Howes, Stuart C.

Collagen implants are widely used in clinical practice and are an active area of research. The continued development of collagen-based implants often relies on histological techniques to fully evaluate the host response post implantation. These destructive, end-point analyses limit the rate that data can be obtained from samples. Magnetic resonance imaging has the potential to non-invasively monitor the remodeling of collagen scaffolds. In this study, scaffolds prepared from insoluble bovine collagen, with varied and predictable tissue responses were implanted in rats and evaluated using both histological and MRI techniques. Treatment of scaffolds with a carbodiimide crosslinker was found to slow the degradation and cellular infiltration into the scaffolds compared to uncrosslinked scaffolds. Angiogenesis was observed in core regions of crosslinked scaffolds, but not uncrosslinked scaffolds. Conjugation of chondroitin sulfate to the collagen scaffolds in combination with crosslinking improved both the cellular infiltration and angiogenesis compared to uncrosslinked and crosslinked scaffolds. Correlations between histology and MRI analyses showed that statistically significant relationships existed between cellular density, void area, T2 and apparent diffusion coefficient (ADC) measurements demonstrating that MRI is sensitive to specific remodeling parameters. Understanding the relationship between histology and MRI parameters may be used to help guide the interpretation of MRI data as well as to reliably detect changes within the implants using the MRI data alone, reducing the need for scaffold harvesting and destructive testing. ii