What role do alveolar p16INK4a-expressing fibroblasts play in promoting repair of alveolar type 2 (AT2) cells?
Previous studies have shown that p16INK4a-expressing fibroblasts enhance airway epithelial regeneration both in vitro using a 3D co-culture assay and in vivo by clearing senescent cells during the regenerative phase following naphthalene injury (Reyes et al., Science, 2022). These findings strongly suggest that fibroblasts expressing p16INK4a induce a senescence-associated secretory phenotype (SASP) conducive to epithelial growth. However, it remains unclear whether this supportive quality is limited to fibroblasts surrounding major airways. Therefore, we are investigating the hypothesis that p16INK4a-expressing fibroblasts activate a region-specific regenerative program tailored to support local stem cells. To induce acute injury in the alveolar region of the lungs, we routinely use the bleomycin injury model, which follows a classical tissue repair phase—homeostasis, inflammation, proliferation, and remodeling—making it an ideal model to study pro-regenerative programs activated in senescent fibroblasts throughout each stage of the alveolar response to injury.
What is the role of p16INK4a in reprogramming the fibroblast secretome?
We have demonstrated that p16INK4a expression is essential for inducing protein secretion in fibroblasts. By manipulating p16INK4a expression using our established tools and combining transcriptomic and proteomic approaches, we aim to establish a baseline of the secretome in p16INK4a -expressing fibroblasts. Our goal is to determine whether protein secretion depends on p16INK4a expression under homeostatic conditions and during injury. By utilizing both established laboratory tools and novel genetic animal models to tag secreted ligands, we aim to identify specific SASP in vivo by lung fibroblasts dependent on p16INK4a expression. Ultimately, our research aims to define p16INK4a's ability to reprogram the SASP in fibroblasts to promote regeneration in neighboring stem cells.
