Investigating Liver Fibrosis in a Humanized Mice Model of Sickle Cell Disease

Sickle cell disease (SCD) is an inherited disorder that affects approximately 100,000 people in the United States and millions worldwide. Although severely understudied, frequency of acute and chronic liver pathologies has increased over the past decades due to the growing life expectancy of SCD patients. Typically, sterile inflammation in the liver promote activation of normally quiescent hepatic stellate cells (HSCs), which leads to excess production of cytokines and growth factors, such as transforming growth factor beta (TGF-β). The activation of HSCs leads to increased expression of profibrotic genes such as collagen, and alpha-smooth muscle actin (α-SMA). Increased production of these profibrotic genes lead to tissue fibrosis and unreversed fibrosis can progress to liver failure. Therefore, targeting TGF-β signaling is crucial to mitigate hepatic fibrosis. Previous studies have shown that cysteine cathepsins – potent collagenases and elastases – can modulate TGF-β protein levels. Based on these studies, we hypothesize that increased TGF-β, through activation of HSCs, promotes liver fibrosis in SCD. To test this hypothesis, we utilized 3-month-old Townes mice liver and performed immunoblotting, zymography and immunostaining. Results showed increased bridging fibrosis, collagen content and α-SMA in sickle mice. There’s increased phosphorylated Smad2/3 protein levels and increased active cathepsins in SS mice. Future work will delineate the signaling interplay of TGF-β signaling, HSCs activation/differentiation and the increased deposition of ECM proteins leading to liver fibrosis and lastly, we will determine whether potent collagenases such as cysteine cathepsins can modulate TGF-β, thus reducing fibrosis in sickle cell disease.