Assessment of SPP1 and FN1 in serum, BALF and lung tissue samples from dogs affected with CIPF

Background:
Canine idiopathic pulmonary fibrosis (CIPF) is a chronic disease affecting West Highland white terriers (WHWTs)1,2. Osteopontin (SPP1) and fibronectin (FN1) are associated with pulmonary fibrosis in men3-6 and are overexpressed in bronchoalveolar lavage fluid (BALF) macrophage clusters in CIPF7.
Study premise:
The aim is to investigate whether these molecules are potential disease markers. SPP1 and FN1 serum and BALF concentrations were measured using canine ELISA kits in CIPF WHWTs (n=24), healthy aged-matched WHWTs (n=13) and healthy terriers (n=15). Proteins were also localized in lung tissue by immunohistochemistry.
Results:
SPP1 serum concentrations were higher in CIPF compared with healthy WHWTs and terriers, and in healthy WHWTs compared with terriers. There were negatively correlated with PaO2 in WHWTs. Higher SPP1 BALF concentrations were found in CIPF and healthy WHWTs compared with terriers. Intense labelling was reported in all groups in ciliated epithelial cells, smooth muscular cells surrounding large vessels and some macrophages. Moreover, in all CIPF WHWTs, the pneumocytes II and the extra cellular matrix were labelled, while it was the case in only 57% of healthy WHWTs and not present in terriers.
FN1 serum concentrations were lower in CIPF and healthy WHWTs compared with terriers. No difference was found between groups in BALF. There was no evidence of differences in FN1 labelling.
Conclusions:
The results suggest that SPP1 is involved in CIPF pathogenesis and could predispose that breed to the disease. However, further studies are required to determine its interest as biomarker or potential therapeutic target.