Graduate Student Seminar Series – Usha Kabilan

Graduate Student Seminar Series
Please ensure you invite your Principal Investigator by adding their email via the ‘Add Guest’ button and they will also be notified of your presentation.
Location: 2nd Floor Auditorium (TRI/KITE) – 550 University Ave
Presentation Title: Macrophage-Fibroblast crosstalk in lung fibrosis
Abstract:
Background: Lung fibrosis is a devastating disease that can affect all organs post-injury due to inadequate repair by activated fibroblasts. These so-called myofibroblasts (MFs) accumulate collagen during fibrosis, resulting in progressive lung stiffening and respiratory failure. Another hallmark of fibrosis is extracellular activation of transforming growth factor-β1 from latent complexes (L-TGF-β1) by fibroblast αv integrins. TGF-β1 drives fibroblast-to-MF activation and renders them resistant to apoptotic clearance. We published that contact with macrophages (Mϕ) mediates chronic TGF-β1 signalling in lung fibroblasts. How L-TGF-β1 is presented by Mϕ in the lung remains unclear.
Hypothesis: Presentation of L-TGF-β1 on the surface of Mϕ for activation by fibroblasts in direct contact results in chronic MF activation and survival.
Objective: To elucidate how L-TGF-β1-presenting Mϕ and TGF-β1-activating MFs create a pro-fibrotic niche of active TGF-β1.
Methods: Monocytes from mouse bone marrow and human peripheral blood were polarized using cytokine cocktails that mimic normal, inflammatory, and fibrotic lung conditions. Mϕ polarization and expression of L-TGF-β1 presenting membrane proteins (“tethers”) such as GARP and NRROS were assessed using flow cytometry and qRT-PCR. Mϕ expressing L-TGF-β1 tethers were co-cultured with fibroblasts, and TGF-β1 activation was quantified using αSMA (alpha-smooth muscle actin) expression, an MF marker, using Immunofluorescence microscopy. Gene silencing of L-TGF-β1 tethers and inhibition of αv integrins were used to modulate TGF-β1 activation in co-cultures.
Results: Polarization with GM-CSF and IL-13, cytokines that are characteristic of the lung alveolar microenvironment, produced CD163+CD200R+ alveolar-like Mϕ (ALMs). ALMs expressed high levels of TGF-β1, and the L-TGF-β1 tethers GARP, while no difference in NRROS gene expression. GARP loss and integrin inhibition from ALMs in co-cultures with fibroblasts disrupted TGF-β1 and MF activation that drives lung fibrosis.
Conclusion and Significance: Presentation of L-TGF-β1 by GARP on the surface of ALMs to αv integrin-expressing fibroblasts is crucial for MF activation. Specifically inhibiting GARP-TGF-β1 may represent a novel targeted approach to block MF activation in lung fibrosis.
Supervisor Name: Boris Hinz
Year of Study: 2
Program of Study: PhD
Powered by Calendly.com