Digital quantification of p16-positive foci in fibrotic interstitial lung disease is associated with a phenotype of idiopathic pulmonary fibrosis with reduced survival

• Published in: Respiratory research 2022-06, Vol.23 (1), p.147-147, Article 147
• Main Authors: Keow, Jonathan, Cecchini, Matthew J, Jayawardena, Nathashi, Zompatori, Maurizio, Joseph, Mariamma G, Mura, Marco
• Format: Article
• Language: English
• Subjects: Biological markers; Biopsy; Cell cycle; Collagen; Cyclin-dependent kinase; Cyclin-dependent kinase inhibitors; Cyclin-dependent kinases; Diagnosis; Epithelium; Fibroblasts; Fibrosis; Gene expression; Genetic aspects; Health aspects; Idiopathic pulmonary fibrosis; Immunohistochemistry; Inhibitors; Interstitial lung disease; Kinases; Lung diseases; Lung diseases, Interstitial; Lung transplantation; Medical prognosis; Monoclonal antibodies; Morphology; Patient outcomes; Phenotypes; Pneumonia; Pulmonary fibrosis; Risk factors; Senescence; Spatial analysis; Survival; Tumor suppressor genes; Usual interstitial pneumonia
• ISSN: 1465-993X; 1465-9921; 1465-993X; 1465-9921
• DOI: 10.1186/s12931-022-02067-w

Idiopathic pulmonary fibrosis (IPF) is associated with increased expression of cyclin-dependent kinase inhibitors such as p16 and p21, and subsequent induction of cell cycle arrest, cellular senescence, and pro-fibrotic gene expression. We sought to link p16-expression with a diagnosis of IPF or other fibrotic interstitial lung diseases (ILDs), radiographic pattern, senescent foci-specific gene expression, antifibrotic therapy response, and lung transplant (LTx)-free survival. Eighty-six cases of fibrosing ILD were identified with surgical lung biopsy. Immunohistochemistry for p16 was performed on sections with the most active fibrosis. p16-positive foci (loose collection of p16-positive fibroblasts with overlying p16-positive epithelium) were identified on digital slides and quantified. Cases were scored as p16-low (≤ 2.1 foci per 100 mm ) or p16-high (> 2.1 foci per 100 mm ). Twenty-four areas including senescent foci, fibrotic and normal areas were characterized using in situ RNA expression analysis with digital spatial profiling (DSP) in selected cases. The presence of p16-positive foci was specific for the diagnosis of IPF, where 50% of cases expressed any level of p16 and 26% were p16-high. There was no relationship between radiographic pattern and p16 expression. However, there was increased expression of cyclin-dependent kinase inhibitors, collagens and matrix remodeling genes within p16-positive foci, and cases with high p16 expression had shorter LTx-free survival. On the other hand, antifibrotic therapy was significantly protective. DSP demonstrated that fibroblastic foci exhibit transcriptional features clearly distinct from that of normal-looking and even fibrotic areas. We demonstrated the potential clinical applicability of a standardized quantification of p16-positive fibroblastic foci. This method identifies an IPF phenotype associated with foci-specific upregulation of senescence-associated and matrix remodeling gene expression. While these patients have reduced LTx-free survival, good response to antifibrotic therapies was observed in those who were treated.