Date of Award

12-2021

Document Type

Honors Thesis

Degree Name

Bachelor of Science

Department

Biology

Advisor/Committee Chair

Amber Altrieth

Major

Biology

Committee Member

Melinda Larsen

Abstract

Extracellular matrix deposition is required for repair after injury, but if left unresolved can result in fibrosis. Fibrosis is an excess deposition of extracellular matrix proteins following injury or aging that leads to eventual organ dysfunction. One surgical model that we have used to study mechanisms of fibrosis is the salivary gland ductal ligation model. During the process of ligation, a clip is placed on the main ducts of the submandibular (SMG) and sublingual gland (SLG) which leads from the salivary glands to the mouth. This causes the gland to atrophy, or waste away, resulting in decreased acinar cell differentiation and death. In the salivary gland, the acinar cells are cells that line an acinus, which is a small sac-like cavity in the gland into which saliva is secreted. We can detect loss of acinar cells by immunostaining to detect epithelial cell proteins like aquaporin 5 (AQP5) which is a water channel protein or conavalin A (ConA). EpCam-FITC can be used to stain for epithelial cells and Ki67 is a cell proliferation marker that allows us to observe what cells are proliferating. The longer the clip is held in place during ligation, the more fibrotic the stroma becomes and the smaller and less productive the salivary gland will become. The ductal ligation can also serve as a model for recovery from injury following the removal of the clip, or deligation. Based on previous research in which saliva production was measured following deligation, acinar cells can fully recover. AQP5 has also been observed in deligated samples, suggesting that the acinar cells do regenerate during deligation. It is unknown how quickly after injury the gland begins to recover, and if the dissipation of the fibrotic response precedes restoration of function. We hypothesize that following deligation, ECM levels will decrease, prior to the restoration of acinar marker protein expression. To address this, we will be performing immunofluorescent and histological staining, IHC, on ligated and deligated tissue cryosections. In this study we will be using C57 mice with a deligation point or mock surgery point of 3 days. First, we will determine if and when acinar cell markers, such as AQP5 and ConA return following deligation. Second, we will be examining the endothelia cells following deligation via IHC staining with CD31 and EpCam-FITC. Lastly, we will be observing what cell types are proliferating with the marker Ki67. This study will provide information on the timing of salivary gland recovery from traumatic injury, which may provide insights into possible regenerative therapies. Depending on the results of this study, we can modify our ligation/deligation timeline to be potentially shorter than 3 days, or longer than 7 days.

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