Single-Cell Analysis of Aneurysmal Aortic Tissue in Patients with Marfan Syndrome Reveals Dysfunctional TGF-β Signaling

The molecular and cellular processes leading to aortic aneurysm development in Marfan syndrome (MFS) remain poorly understood. In this study, we examined the changes of aortic cell populations and gene expression in MFS by performing single-cell RNA sequencing (scRNA seq) on ascending aortic aneurysm tissues from patients with MFS (n = 3) and age-matched non-aneurysmal control tissues from cardiac donors and recipients (n = 4). The expression of key molecules was confirmed by immunostaining. We detected diverse populations of smooth muscle cells (SMCs), fibroblasts, and endothelial cells (ECs) in the aortic wall. Aortic tissues from MFS showed alterations of cell populations with increased de-differentiated proliferative SMCs compared to controls. Furthermore, there was a downregulation of MYOCD and MYH11 in SMCs, and an upregulation of COL1A1/2 in fibroblasts in MFS samples compared to controls. We also examined TGF-β signaling, an important pathway in aortic homeostasis. We found that TGFB1 was significantly upregulated in two fibroblast clusters in MFS tissues. However, TGF-β receptor genes (predominantly TGFBR2) and SMAD genes were downregulated in SMCs, fibroblasts, and ECs in MFS, indicating impairment in TGF-β signaling. In conclusion, despite upregulation of TGFB1, the rest of the canonical TGF-β pathway and mature SMCs were consistently downregulated in MFS, indicating a potential compromise of TGF-β signaling and lack of stimulus for SMC differentiation

Synthesis and Characterization of C8 and N2 2\u27-Deoxyguanosine Adducts of 6-Nitrochrysene, A Cancer-Causing Agent

Nitropolycyclic aromatic hydrocarbons are ubiquitous in the environment, and many compounds of this family are carcinogenic. 6-Nitrochrysene, a representative member of this group, is a suspected human carcinogen that has been shown to cause lung, breast, and other forms of cancer in rodents. It is believed that this derivative of chrysene causes cancer by forming DNA adducts, which, in turn, induce mutations in critical gene sequences. The goal of my research is to synthesize one or more of the major DNA adducts formed by 6-nitrochrysene, which will be introduced in DNA in order to study their biological effects. The initiation step of the multi-step process that leads to cancer involves mutations in DNA via erroneous replication, which occurs when the body is unable to repair certain DNA damages. Accumulation of these mutations in critical genes triggers a series of biological events, ultimately making the cell an outlaw. Usually, there are specific processes the cell employs to repair DNA damages. Cancer-causing agents, such as 6-nitrochrysene, are metabolically activated in a cell to electrophilic species, which induce specific DNA damages resulting in a high frequency of mutations. Understanding exactly how 6-nitrochrysene causes mutations will provide insight into how cancer by this chemical is initiated. In order to accomplish this, one must synthesize the damaged nucleoside and incorporate it into a DNA fragment. In this thesis, two new schemes are presented to prepare the 6-nitrochrysene-damaged DNA fragments