Publication Date

2018

Document Type

Thesis

Committee Members

Nasim Nosoudi (Committee Member), Jaime Ramirez-Vick (Advisor), Amir Zadeh (Committee Member)

Degree Name

Master of Science in Biomedical Engineering (MSBME)

Abstract

Modulation of macrophage polarization is required for effective tissue repair and regenerative therapies. Conversion of macrophages from inflammatory M1 to fibrotic M2 phenotype could help in diseases such as chronic wound which are stuck in inflammatory state. During the inflammatory phase, macrophages are of the inflammatory phenotype (M1) and distribute pro-inflammatory cytokines including TNF-a and IL1[beta] which are microbicidal and recruit/activate cells. In normal wound healing macrophages then switch to a fibrotic phenotype (M2) promoting wound closure by angiogenesis, and matrix deposition. Chronic wounds are a major biological and financial burden to both patients and the health care system, costing over $25 billion to Medicare annually. Natural wound healing proceeds through several largely overlapping phases that involve an inflammatory response and associated cellular migration, proliferation, matrix deposition, and tissue remodeling. The initial stages of the inflammatory response are dominated by neutrophils followed soon after by macrophages, which become prominent at the wound site. A sustained inflammation is an important aspect in the disruption of the normal healing process that can lead to a chronic condition. The chronic conditions start when the highly phagocytic M1 macrophages are done removing any infected or non-functional cells, and any damaged matrix or foreign debris and do not differentiate into an M2 phenotype. Thus, inducing these sustained M1 macrophages to differentiate into an M2 phenotype should correct this condition, and has been shown to improve wound healing. We suggest simultaneously using retinoic acid (RA) and mesenchymal stem cells (MSCs) to promote M1 to M2 transition. RA and MSCs have both shown to promote M1 to M2 transition, and in addition, MSCs can promote wound regeneration. We hypothesize that treating M1 macrophages with retinoic acid and mesenchymal stem cells loaded on a pullulan/gelatin scaffold will promote M1 to M2 conversion. To facilitate this, we developed an electrospun hydrogel consisting of 75% pullulan and 25% gelatin and crosslinked with 1:70 ethylene glycol diglycidyl ether (EGDE) in ethanol (EtOH). Pullulan was chosen due to its ability to quench reactive oxygen species and reduce inflammation, as well as for its excellent mechanical properties. While gelatin was added to provide functional motifs for cellular attachment. The scaffold composition was determined via FTIR. The scaffold degraded to approximately 80% after 14 days, and approximately 38% of the drug was released after 7 days. Scaffold nanofibers were determined to 328nm (±47.9) in diameter. RA and MSCs were directly loaded and used to treat M1 THP1 cell derived macrophages to induce polarization. qPCR shows a reduction of M1 markers TNFa and IL1ß, and an increase of M2 marker CCL22 after 2 days of scaffold treatment, suggesting successful M1 to M2 transition.

Page Count

95

Department or Program

Department of Biomedical, Industrial & Human Factors Engineering

Year Degree Awarded

2018

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