〔Abstract〕 Objective To investigate the effect of phosphatase and tensin homolog(PTEN) overexpression on autophagy in mouse primary cardiac fibroblasts. Methods Neonatal mice(1-3 days old) were purchased and subjected to cardiac tissue harvesting. Cardiac fibroblasts were isolated through enzymatic digestion and cultured. After cellular adhesion, rapamycin(Rapa)-treated cardiac fibroblasts were used to establish an autophagy model. Following successful model construction, cells were transfected with eitherPTEN-overexpressing plasmid(PTENoverexpression group) or empty vector(control group), followed by 24-48 h incubation. The molecular expressions of PTEN, autophagy-related proteins [microtubule-associated protein light chain 3(LC3Ⅱ/Ⅰ), Beclin1], and fibrotic marker collagen Ⅰ were detected by Western blot and RT-qPCR. Autophagic flux was assessed using mCherry-GFP-LC3 fluorescence staining to evaluate changes in autophagic activity. Transmission electron microscopy(TEM) was employed to observe autophagosome formation in cardiac fibroblasts. Results In the Rapa-induced cardiac fibroblast autophagy model, compared with the control group, the protein and mRNA levels of PTEN significantly decreased(P<0.05), while the expression of autophagy-related proteins(LC3Ⅱ/Ⅰ, Beclin1) and fibrotic marker Collagen Ⅰ was upregulated at both protein and mRNA levels(P<0.05). Additionally, in PTEN-overexpressing cardiac fibroblasts, the expression levels of LC3Ⅱ/Ⅰ, Beclin1, and Collagen Ⅰ were markedly reduced compared to the empty vector group(P<0.05). mCherry-GFP-LC3 fluorescence staining demonstrated that autophagic activity was significantly attenuated in thePTENoverexpression group versus the empty vector group(P<0.05). TEM further revealed a decreased number of autophagosomes in PTEN-overexpressing cardiac fibroblasts(P<0.05). Conclusion The overexpression ofPTENsignificantly inhibits autophagy in cardiac fibroblasts, suggesting thatPTENmay be a key gene involved in regulating autophagy in cardiac fibroblasts.