Author ORCID Identifier

0000-0001-5215-0914

Defense Date

2017

Document Type

Thesis

Degree Name

Master of Science

Department

Physiology and Biophysics

First Advisor

Zhao Lin

Second Advisor

Sinem E Sahingur

Third Advisor

Liya Qiao

Abstract

Periodontal disease affects 47% of Americans over 30. Characterized by microbial dysbiosis and unregulated inflammation, severe periodontitis causes degradation of bone and soft tissue around teeth. Current treatments have limited regenerative outcomes and frequent reinfection by harmful bacteria. Human mesenchymal stem cells (hMSCs) have been shown to promote wound healing and tissue regeneration. Many therapeutic benefits of hMSCs are due to their secretome products, like exosomes. Our long-term goal is to develop periodontal therapies with hMSC exosomes. The objectives of this study were to determine the effect of hMSC-derived exosomes on cellular activity of hMSCs and investigate whether hMSC exosome treatment reduces pro-inflammatory cytokine production in LPS-activated RAW264.7 cells. The specific aims of this study were: 1) Determine the characteristics of hMSC-derived exosomes, 2) Determine the biological effect of exosomes on cellular activity of hMSCs, 3) Determine whether exosomes treatment can inhibit cytokine production in activated RAW264.7 cells, and 4) Determine the role of exosomal miRNA in pro-inflammatory cytokine production of RAW264.7 cells. To investigate, exosomes were first harvested from hMSCs culture media through ultracentrifugation. Exosomes were then observed under a transmission electron microscope (TEM) and assessed for surface markers using Western Blot. A transwell migration assay was used to evaluate the chemotactic effect of exosomes. To study the effect of exosomes on stem cell proliferation, exosomes were administered to hMSCs. The immunogenicity of MSC exosome was also evaluated. After 72 hours, cells were lysed and DNA was measured. To study anti-inflammatory effects of exosomes, LPS stimulated RAW264.7 cells were treated with exosomes. Interleukin-6 (IL-6) and tumor necrosis factor alpha (TNFα) levels of supernatant were measured by ELISA. To study exosomal miRNA, exosomal miRNAs were overexpressed in RAW264.7 cells and these cells were stimulated with LPS. IL-6 and TNFα were measured by ELISA. TEM images showed that exosomes are nano-sized vesicles (~100 nm). Western blot images showed that CD63 and CD81 are enriched in exosomes compared to total cell lysates. Exosome treatment increased cell proliferation and migration in hMSCs. At the doses that are chemotactic and mitogenic, MSC exosomes had minimal effect on the inflammatory cytokine IL-6 production. Treatment with exosomes significantly decreased IL-6 and TNFα production in RAW264.7 cells activated by LPS. Transfecting RAW264.7 cells with exosomal miR-760 significantly decreased IL-6 production, but had minimal effect on TNFα. Our results indicate that exosomes have a pleiotropic activity, which includes stimulating stem cell migration and proliferation, and mitigating the inflammatory response. Therefore, hMSC exosome delivery is promising for the treatment of periodontal diseases.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

7-10-2017

Available for download on Saturday, July 09, 2022

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