Date of Award

1-1-2018

Embargo Period

1-1-2024

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Oral Health Sciences

College

College of Graduate Studies

First Advisor

James J. Cray

Second Advisor

Carl Atkinson

Third Advisor

Jeffrey A. Jones

Fourth Advisor

Amanda C. LaRue

Fifth Advisor

Robin C. Muise-Helmericks

Abstract

Background: Currently, the gold standard intervention for substantially large bone wounds is autologous bone grafting. While effective, this therapy is complicated by creation of an invasive second surgical site and limited material available for harvest. INFUSE® Bone Graft (rhBMP-2 delivered via an absorbable collagen sponge or ACS) has been widely used as a graft substitute, resulting in robust bone formation, but at the cost of increased inflammation and often poor healing outcomes. A better understanding of the mechanisms by which rhBMP-2 influences inflammatory processes and how these processes can be modulated through other therapies will inform future novel pharmacological avenues to improve patient outcomes. Hypothesis: Delivery of rhBMP-2 will result in increased inflammation (prolonged M1 response, delayed M2 response) and increased angiogenesis. Administration of pGlcNAc nanofibers will result in a reduced inflammation. Methods: Calvarial defects (5mm) were created in wild-type mice. Defects were treated with ACS alone (control), ACS loaded with rhBMP-2, or a pGlcNAc nanofiber scaffold. Mice were sacrificed at 3 and 7 days post-operation and calvariae were isolated for downstream analyses. Isolated protein was subjected to western blotting. Mounted tissue sections were stained with hematoxylin and eosin for morphological characterization within the defect. Further, immunohistochemistry for markers of inflammation and macrophage polarization were performed and analyzed for effects on inflammation and tissue repair. Results: Baseline characterization of ACS alone indicated little change in markers associated with inflammation from three to seven days. Additionally, delivery of rhBMP-2 led to a delay in macrophage response, but had little effect on macrophage polarization. Angiogenesis was down early in response to rhBMP-2, but resolved to normal levels by day seven. The addition of pGlcNAc to the calvarial defect did not dampen inflammation compared to the baseline control. Further, this treatment had little effect on angiogenesis compared to the ACS alone. Conclusions: This subclinical dose of rhBMP-2 did not lead to further or sustained inflammation compared to the baseline control. Further, the addition of pGlcNAc did not result in a localized down regulation of inflammation. Identifying other methods for delivery of rhBMP-2 and alternative dosing schemas may prove beneficial in improving patient outcome.

Rights

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