Simone A. Douglas

PhD Proposal Presentation

Date: November 9, 2017

Time: 12-2pm

Location: EBB 4029 (Georgia Institute of Technology)

Committee:

Advisor: Manu O. Platt, PhD

Edward A. Botchwey, PhD

Johnna S. Temenoff, PhD

Rodney Averett, PhD

Clinton Joiner, MD, PhD

Roger D. Kamm, PhD

Title: Cathepsin-Mediated Fibrin(ogen)olysis Matrix and Vasculature Remodeling

Abstract:

Cysteine cathepsins are powerful proteases involved in tissue destructive disease progression, including vasculogenesis and pathogenic vascular remodeling. These enzymes have been identified as the most potent mammalian collagenases and elastases. However, their potential roles in polymerizing and degrading fibrin, an essential blood clotting protein and commonly used biomaterial scaffold for tissue repair, have not been well characterized. Preliminary work shows that cathepsins K, L, and S are fibrin(ogen)olytic, which can help uncover unknown mechanisms for matrix destabilization, having implications in biomaterial design and aberrant blood clotting in vascular diseases.  To identify the putative role of cathepsin-mediated fibrin(ogen)olysis, we will use a fibrin-based construct as a biological mimicking test bed and sickle cell disease for a pathological condition. The central hypothesis of my proposal is that cysteine cathepsins have fibrin(ogen)olytic properties that contribute to fibrin-based construct destabilization and aberrant blood clotting in sickle cell disease. Perfusable microvascular networks (MVNs) are fibrin-based constructs which destabilize within days and collapse due to unknown mechanisms. We hypothesize that cysteine cathepsins, known to be secreted by MVN constituents, endothelial cells and fibroblasts, can hydrolyze fibrin(ogen) and destabilize MVNs. Further, we have shown that cathepsins are upregulated and involved in vascular remodeling in SCD. People with sickle cell disease experience hypercoagulation, or excessive blood clotting, characterized by increased fibrinogen and fibrinopeptide A levels, which can lead to vaso-occlusion and sickle pain crisis (severe pain due to occluded blood vessels). We hypothesize that upregulated cathepsins can cleave fibrinogen, releasing and increasing fibrinopeptide A levels in SCD. We will test our hypotheses with the following aims: 1) control proteolytic activity in microvasculature networks and 2) assess how cathepsins cleave fibrinogen to understand abnormal blood clotting mechanisms in sickle cell disease.