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Objective To explore whether miR-9 can inhibit the growth of hypertrophic scar fibroblasts by targeting PI3K. Methods From September 2020 to September 2021, 12 healthy adult New Zealand long-eared rabbits were randomly divided into control group (6 rabbits) and scar group (6 rabbits). The histological morphology of both groups was detected by HE staining. The mRNA expression of miR-9 and PI3K in tissues was detected by real-time fluorescent quantitative PCR, and the expression of miR-9 and PI3K was analyzed by Pearson's correlation coefficient. The human hypertrophic scar fibroblasts (HSFb) were divided into psiCHECK-WT-PI3K+miR-9 control group, psiCHECK-WT-PI3K+miR-9 mimic group, psiCHECK-MUT-PI3K+miR-9 control group and psiCHECK-MUT-PI3K+ miR-9 mimic group. The corresponding sequences were transfected respectively. The expression of luciferase and renilla luciferase were detected by luciferase reporter gene assay at 48 h after transfection. The HSFb was divided into miR-9 control group and miR-9 mimic group. At 0, 12, 24, 36 and 48 h after transfection, the cell proliferation was detected by MTT. At 24 h after treatment, the cell apoptosis was detected by Annexin V-FITC/PI kit, and the expression of PI3K, caspase 3 and Bcl-2 protein was detected by protein immunoblotting. The number of samples in cell experiment was 3. The data were analyzed by t-test and Pearson's correlation coefficient. Results In HE staining, the excessive proliferation of fibroblasts and inflammatory cell infiltration were found in scar tissue. The model was successfully constructed. Compared with the control group, the miR-9 expression was significantly down-regulated (t=11.020, P<0.05) and PI3K expression was significantly up-regulated in the scar group (t=10.840, P<0.05). Pearson's correlation analysis showed that the expression of miR-9 and PI3K was negatively correlated in all tissues. At 48 h after transfection, the PI3K activity in the psiCHECK-WT-PI3K + miR-9 mimic group was significantly lower than that in the psiCHECK-WT-PI3K+miR-9 control group (t=8.648, P=0.001). The PI3K activity in the psiCHECK-MUT-PI3K+miR-9 control group was similar to that in the psiCHECKMUT-PI3K+miR-9 mimic group (t=2.053, P=0.109). At 12, 24, 36 and 48 h after transfection, the proliferation ability of miR-9 mimic group was significantly lower than that of the miR-9 control group (P<0.05). At 24 h after transfection, the early apoptotic rate of HSFb in the miR-9 mimic group was higher than that in the miR-9 control group (t=11.210, P=0.001). MiR-9 can down regulate the expression of PI3K, inhibit the expression of Bcl-2 and up regulate the content of caspase 3. Conclusion MiR-9 is down-regulated in the hypertrophic scar tissue, which can inhibit the growth of HSFb by targeting PI3K. [ABSTRACT FROM AUTHOR]

BACKGROUND: Due to the close relationship between the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway and the physiological metabolism of bone tissue, human chitinase protein 40 (YKL-40) can regulate the PI3K/Akt signaling pathway related to breast cancer pathogenesis. Therefore, it is speculated that YKL-40 may regulate apoptosis in knee osteoarthritis (KOA) chondrocytes through the PI3K/Akt signaling pathway. OBJECTIVE: To study the mechanism by which YKL-40 regulates apoptosis in rabbit KOA chondrocyte s through the PI3K/Akt signaling pathway. METHODS: (1) New Zealand white rabbits were randomized into two groups. An animal model of KOA was made using anterior cruciate ligament dissection in the model group, whereas the right posterior knee joint capsule was cut but not dissected in the control group. Chondrocytes were extracted from the rabbits at 6 weeks after modeling. Hematoxylin-eosin staining and Mankin histological scoring of the cartilage tissue were performed, whereas immunohistochemical staining was used to detect type II collagen expression in chondrocytes. (2) The second-generation chondrocytes in the control group were used as normal control group, and those in the model group were further divided into four groups, followed by culture with high glucose DMEM medium containing 10% fetal bovine serum in KOA model group, 100 μg/L YKL-40 in KOA + YKL group, 50 μmol/L LY294002 in KOA + LY group, and 50 μmol/L LY294002 + 100 μg/L YKL-40 in KOA + YKL + LY group. The expression levels of collagen type II, matrix metalloproteinase 13, Akt, p-Akt, P53, Bcl-2 proteins in chondrocytes were detected by western blot. RESULTS AND CONCLUSION: Hematoxylin-eosin staining, Mankin histological score, and collagen type II immunohistochemical staining confirmed the successful construction of KOA animal model and successful chondrocyte culture. Compared with the normal control group, the collagen type II, Bcl-2, p-Akt protein expression levels in chondrocytes were significantly reduced in the KOA model group (P < 0.05), and matrix metalloproteinase 13 and P53 protein expression levels were significantly increased in the KOA model group (P < 0.05). Compared with the KOA model group, these indicators were significantly improved in the KOA + YKL group (P < 0.05), significantly worsened in the KOA + LY group (P < 0.05), and had no significant changes in the KOA + YKL + LY group (P > 0.05). However, there were significant differences between the KOA + YKL group and the KOA + LY group (P < 0.05). In addition, the expression level of p-Akt protein in chondrocytes had no difference among groups (P > 0.05). To conclude, YKL-40 can inhibit the apoptosis of KOA chondrocytes, accelerate the repair of KOA cartilage damage and delay the degeneration of cartilage by activating the PI3K/Akt signaling pathway. Therefore, YKL-40 can be used as a new target for clinical treatment of KOA. [ABSTRACT FROM AUTHOR]