Correlation between serum TNAP and myocardial fibrosis in patients after myocardial infarction

Objective To investigate the relationship of tissue non-specific alkaline phosphatase (TNAP) with myocardial fibrosis in patients after myocardial infarction (MI). Methods Forty-six acute MI patients admitted to our hospital from March to November 2019 were enrolled in this study and assigned as the MI group, and another 41 patients with negative findings in coronary angiograms during the same period were collected as the control group. The serum TNAP activity was detected by alkaline phosphatase kit. The serum contents of procollagen type ⅠC-peptide (PⅠCP) and procollagen Ⅲ N-terminal peptide (PⅢNP) were detected by enzyme-linked immunosorbent assay (ELISA). Myocardial tissues from 5 patients who died of MI were collected. Collagen fiber area of heart was detected by Sirius red staining and the expression of TNAP was detected by immunohistochemistry. Ten 8-week-old male C57BL/6J mice were randomly divided into sham group and MI group (n=5). In 2 weeks after MI, all mice were sacrificed, and collagen fiber area of heart was detected by Masson staining and the expression of TNAP was detected by immunohistochemistry. Results Compared with the control group, the MI group had significantly increased serum TNAP activity (8.49±3.30 King U/100 mL, P<0.01), higher serum contents of P Ⅰ CP and PⅢNP (both P<0.01), and the serum TNAP activity was statistically correlated with the serum contents of P Ⅰ CP and PⅢNP (r=0.38, P<0.01; r=0.40, P<0.01). There were more collagen deposition and higher TNAP expression level in the infarct border area of remote MI lesion than in the distal infarct (both P<0.01). Compared with the mice of the sham group, the expression of TNAP and collagen fiber area in MI group were increased significantly (both P<0.01), and the expression was consistent with the distribution of fibers in the MI group. Conclusions TNAP is involved in the pathophysiological process of myocardial fibrosis after MI.