Objective To investigate the relationship of pulmonary surfactant protein D( SP-D) with chronic obstructive pulmonary disease ( COPD) by measuring SP-D level in serum and lung tissue of rats with COPD.Methods The rat COPD model was established by passive smoking as well as intratracheal instillation of lipopolysaccharide ( LPS) . Thirty male SD rats were randomly divided into a control group, a LPS group, and a COPD group( n =10 in each group) . The pathologic changes of lung tissue and airway were observed under light microscope by HE staining. Emphysema changes were evaluated by mean linear intercept ( MLI) of lung and mean alveolar number ( MAN) . The level of SP-D in serum was measured by enzymelinked immunosorbent assay ( ELISA) . The expression of SP-D in lung tissue was detected by Western-blot and immunohistochemistry.Results The MLI obviously increased, and MAN obviously decreased in the COPD group compared with the control group ( Plt;0.05) . There was no significant difference in the MLI and MAN between the LPS group and the control group ( Pgt;0.05) . The serum SP-D level was ( 49.59 ±2.81) ng/mL and ( 53.21±4.17) ng/mL in the LPS group and the COPD group, which was significantly higher than that in the control group [ ( 42.14±2.52) ng/mL] ( Plt;0.05) . The expression of SP-D in lung tissue was 0.56±0.01 and 0.63±0.01 in the LPS group and the COPD group, which was also obviously ber than that in the control group ( 0.39 ±0.01) ( Plt;0.05) .Meanwhile the SP-D levels in serumand lung tissue were higher in the COPD group than those in the LPS group ( Plt;0.05) . The levels of SP-D between serum and lung tissue were positively correlated in all three groups ( r=0.93, 0.94 and 0.93, respectively, Plt;0.01) .Conclusion Both the SP-D level in serum and in lung tissue increase significantly in COPD rats and correlate well each other, which suggests that SP-D may serve as a biomarker of COPD.
Objective To investigate the impact and mechanisms of periostin (POSTN), Krebs von den Lungen-6 (KL-6), pulmonary surfactant protein A (SP-A), and pulmonary surfactant protein D (SP-D) on the diagnosis and disease assessment of idiopathic pulmonary fibrosis (IPF), and conduct a comparative analysis. Methods From October 2022 to October 2023, a total of 55 patients diagnosed with IPF and treated at the Third Affiliated Hospital of Anhui Medical University were enrolled as an IPF group. Additionally, 30 patients with bacterial pneumonia and 30 healthy individuals undergoing concurrent health examinations during the same period were selected as a pneumonia control group and a healthy control group, respectively. All participants underwent enzyme-linked immunosorbent assay to measure serum levels of POSTN, KL-6, SP-A, and SP-D, along with pulmonary function tests. The IPF patients also underwent high-resolution computed tomography (HRCT) and echocardiography to quantify HRCT scores and pulmonary artery systolic pressure (PASP). Receiver operating characteristic (ROC) curves were plotted to analyze the significance of serum POSTN, KL-6, SP-A, and SP-D levels in IPF diagnosis. Pearson and Spearman correlation tests were used to analyze the relationships between these biomarkers and pulmonary function, PASP, and HRCT scores. Results Serum concentrations of POSTN, KL-6, SP-A, and SP-D were significantly elevated in the IPF group compared with the pneumonia group and the healthy controls (P<0.05), while serum levels of SP-A and SP-D were notably higher in the pneumonia group compared with the healthy control group (P<0.05). Within the IPF group, serum POSTN levels were negatively correlated with forced expiratory volume in the first second as a percentage of predicted value (FEV1%pred) and diffusion capacity of the lung for carbon monoxide as a percentage of predicted value (DLCO%pred) (P<0.05); KL-6 and SP-D levels were also negatively correlated with FEV1%pred, forced vital capacity as a percentage of predicted value (FVC%pred), and DLCO%pred (P<0.05); and the concentration of SP-A was negatively correlated with DLCO%pred and positively correlated with PASP (P<0.05). Additionally, serum levels of POSTN, KL-6, and SP-A in the IPF group showed significant positive associations with HRCT scores (P<0.01). Conclusions POSTN is a valuable serum biomarker for IPF, exhibiting the highest sensitivity and specificity among the four serum markers, with diagnostic performance superior to KL-6, SP-A, and SP-D. POSTN, KL-6, SP-A, and SP-D can all be used for the diagnosis and assessment of IPF.