Effects of Macrophage Polarization Induced by Mesoporous Silicon-Based Curcumin-siRNA Nanoparticles on the Proliferation of Tendon Stem Cells

Studies have shown that curcumin (CUR)-siRNA can improve excessive fibrosis in the repair of patellar tendon (PT) injury. First, mesoporous silicon nanoparticles (NPs) (MES-SiN) were prepared by a sol–gel method. The small molecule CUR was adsorbed in the internal pore canal of MES-Sin, and the cationic high molecular polyethyleneimine (PP) was adsorbed on the outer layer, which combined with negatively charged siRNA to form CUR@MES-SiN-PP/siRNA NPs. The preparation of NPs was observed by transmission electron microscopy (TEM). RAW264.7 macrophages were treated with different concentrations of NPs, and cell viability was determined by methyl tetrazolium (MTT) assay. The NPs were prepared by siRNA labeled with the fluorescent dye 6-carboxyfluorescein (FAM) and transfected into cells. The cellular uptake of the NPs was observed by confocal laser scanning microscopy (CLSM) and TEM. A total of 80 SPF SD rats (10 weeks of age) were randomly assigned into two groups to establish a PT injury model. The rats in experimental (Exp) group were injected with CUR@MES-SiN-PP/siRNA NP solution (2 μ g/g) in the abdomen for 14 d, and those in control (Ctrl) group were injected with an equal dose of 1% dimethyl sulfoxide (DMSO). The rectus femoris of 24 rats were taken from each group 12 h and 1 d, 3 d, 5 d, 7 d, and 14 d after injury. Masson and hematoxylineosin were used to observe the degree of fibrosis of the PT tissue. The differentiation of macrophages was observed by flow cytometry, and the proliferation of tendon stem cells was observed by immunofluorescence approaches such as Pax7. The results suggested that CUR@MES-SiN-PP/siRNA NPs were successfully fabricated. The NPs showed dose-dependent cytotoxicity, the cell viability remained above 90% at concentrations below 10 μ g/mL, and the NPs were ingested by higher cells. After injury, the fibrotic area of Exp group was drastically decreased ( P <0.05), and the regenerated muscle fiber area was increased ( P <0.05). The number of M2-type macrophages increased markedly 3 d, 5 d, 7 d, and 14 d after injury ( P <0.05). Immunofluorescence showed that the proliferation of fluorescent cells 3 d after surgery was superior to that of Ctrl group ( P <0.05).