Objective:To investigate the effects of exosomes secreted by bone marrow mesenchymal stem cells (BMSCs) during osteogenic differentiation on the polarization of Raw264.7 macrophages and to elucidate the underlying mechanisms.Methods:PBS, uninduced BMSCs conditioned medium (CM), and osteogenic induction BMSCs CM for 7 d, 14 d, and 21 d were respectively added to Raw264.7 macrophages. After 48 h of treatment, Western blotting was used to detect and compare the expression of M1 markers of macrophages [inducible nitric oxide synthase (iNOS) and CD86] and M2 markers of macrophages [arginase-1 (ARG-1) and CD163] in each group. In addition, Raw264.7 macrophages were divided into three groups: the PBS group (only PBS added), the BMSCs-exo group (exosomes derived from uninduced BMSCs were added), and 7D-BMSCs-exo (exosomes derived from BMSCs were added after 7 days of osteogenic induction). The absorbance values of Raw264.7 cells in each group at 24 h, 48 h and 72 h were detected by an enzyme-linked immunosorbent assay (ELISA) reader. Western blotting was performed to assess changes of M1 or M2 marker proteins in Raw264.7 macrophages treated by exosome. The supernatants of the three groups of Raw264.7 macrophages were then co-cultured with BMSCs. Alizarin Red staining was used to quantify the formation of mineralized nodules, and alkaline phosphatase (ALP) staining was used to evaluate the osteogenic activity, and the expression levels of osteogenesis-related proteins Runx2, ALP, osteopontin (OPN), and osteocalcin (OCN) were detected. The migration ability of endothelial progenitor cells (EPCs) was detected by scratch assay for migration distance, and the angiogenesis ability was detected by in vitro tube formation assay for the number of vascular rings formed. The expressions of vascular endothelial growth factor (VEGF)-A and platelet-derived growth factor (PDGF) were detected by Western blot. The activation of the MAPK signaling pathway was evaluated by measuring phosphorylated and total P38 and ERK1/2 levels.Results:Western blot analysis showed that CM from BMSCs after 7 days of osteogenic induction (7D-BMSCs-CM) induced the strongest M2 polarization in macrophages. Compared with the PBS group, 7D-BMSCs-CM induced the most significant polarization of Raw264.7 macrophages to the M2 type, and increased ARG-1 and CD163 expression to 1.36±0.09 and 1.69±0.09, respectively ( P<0.05), while decreasing iNOS and CD86 to 0.21±0.03 and 0.29±0.03 ( P<0.05). The absorbance values of macrophages in the 7D-BMSCs-exo group were significantly higher than those in the PBS group at 24 h, 48 h, and 72 h ( P<0.05). Compared with BMSCs-exo group, 7D-BMSCs-exo upregulated the expressions of CD163 and ARG-1 while inhibited the expressions of iNOS and CD86 ( P<0.05). Alizarin red staining showed enhanced mineral deposition and a higher degree of mineralization in the 7D-BMSCs-exo group, the staining intensity of ALP also increased simultaneously, the Western-blot results showed that the protein expressions of Runx2, ALP, OPN and OCN were respectively higher than those in the PBS group ( P<0.05). The results of the scratch assay showed that the relative migration distance of EPCs cells in the 7D-BMSCS-exo group at 24 h reached 2.30±0.05 μm, which was higher than that in the PBS group 1.10±0.02 μm ( P<0.05). The Tube formation experiment showed that the number of vascular rings in the EPCs group was higher than that in the PBS group (30.3±2.5 and 15.0±1.0, P<0.05), and the protein expressions of VEGF-A and PDGF were upregulated. Furthermore, the levels of phosphorylated P38 and ERK1/2 were significantly reduced in the 7D-BMSCs-exo group 0.40±0.06 and 0.25±0.06 compared with the PBS group ( P<0.05). Conclusions:Exosomes secreted by BMSCs during osteogenic differentiation promote the M2 polarization of Raw264.7 macrophages, with the most pronounced effect observed at the 7th day. M2-polarized macrophages, in turn, enhance the osteogenic differentiation of BMSCs and the angiogenic capacity of EPCs. These processes are closely associated with the suppression of the MAPK signaling pathway.

Objective:To investigate the effects of exosomes secreted by bone marrow mesenchymal stem cells (BMSCs) during osteogenic differentiation on the polarization of Raw264.7 macrophages and to elucidate the underlying mechanisms.Methods:PBS, uninduced BMSCs conditioned medium (CM), and osteogenic induction BMSCs CM for 7 d, 14 d, and 21 d were respectively added to Raw264.7 macrophages. After 48 h of treatment, Western blotting was used to detect and compare the expression of M1 markers of macrophages [inducible nitric oxide synthase (iNOS) and CD86] and M2 markers of macrophages [arginase-1 (ARG-1) and CD163] in each group. In addition, Raw264.7 macrophages were divided into three groups: the PBS group (only PBS added), the BMSCs-exo group (exosomes derived from uninduced BMSCs were added), and 7D-BMSCs-exo (exosomes derived from BMSCs were added after 7 days of osteogenic induction). The absorbance values of Raw264.7 cells in each group at 24 h, 48 h and 72 h were detected by an enzyme-linked immunosorbent assay (ELISA) reader. Western blotting was performed to assess changes of M1 or M2 marker proteins in Raw264.7 macrophages treated by exosome. The supernatants of the three groups of Raw264.7 macrophages were then co-cultured with BMSCs. Alizarin Red staining was used to quantify the formation of mineralized nodules, and alkaline phosphatase (ALP) staining was used to evaluate the osteogenic activity, and the expression levels of osteogenesis-related proteins Runx2, ALP, osteopontin (OPN), and osteocalcin (OCN) were detected. The migration ability of endothelial progenitor cells (EPCs) was detected by scratch assay for migration distance, and the angiogenesis ability was detected by in vitro tube formation assay for the number of vascular rings formed. The expressions of vascular endothelial growth factor (VEGF)-A and platelet-derived growth factor (PDGF) were detected by Western blot. The activation of the MAPK signaling pathway was evaluated by measuring phosphorylated and total P38 and ERK1/2 levels.Results:Western blot analysis showed that CM from BMSCs after 7 days of osteogenic induction (7D-BMSCs-CM) induced the strongest M2 polarization in macrophages. Compared with the PBS group, 7D-BMSCs-CM induced the most significant polarization of Raw264.7 macrophages to the M2 type, and increased ARG-1 and CD163 expression to 1.36±0.09 and 1.69±0.09, respectively ( P<0.05), while decreasing iNOS and CD86 to 0.21±0.03 and 0.29±0.03 ( P<0.05). The absorbance values of macrophages in the 7D-BMSCs-exo group were significantly higher than those in the PBS group at 24 h, 48 h, and 72 h ( P<0.05). Compared with BMSCs-exo group, 7D-BMSCs-exo upregulated the expressions of CD163 and ARG-1 while inhibited the expressions of iNOS and CD86 ( P<0.05). Alizarin red staining showed enhanced mineral deposition and a higher degree of mineralization in the 7D-BMSCs-exo group, the staining intensity of ALP also increased simultaneously, the Western-blot results showed that the protein expressions of Runx2, ALP, OPN and OCN were respectively higher than those in the PBS group ( P<0.05). The results of the scratch assay showed that the relative migration distance of EPCs cells in the 7D-BMSCS-exo group at 24 h reached 2.30±0.05 μm, which was higher than that in the PBS group 1.10±0.02 μm ( P<0.05). The Tube formation experiment showed that the number of vascular rings in the EPCs group was higher than that in the PBS group (30.3±2.5 and 15.0±1.0, P<0.05), and the protein expressions of VEGF-A and PDGF were upregulated. Furthermore, the levels of phosphorylated P38 and ERK1/2 were significantly reduced in the 7D-BMSCs-exo group 0.40±0.06 and 0.25±0.06 compared with the PBS group ( P<0.05). Conclusions:Exosomes secreted by BMSCs during osteogenic differentiation promote the M2 polarization of Raw264.7 macrophages, with the most pronounced effect observed at the 7th day. M2-polarized macrophages, in turn, enhance the osteogenic differentiation of BMSCs and the angiogenic capacity of EPCs. These processes are closely associated with the suppression of the MAPK signaling pathway.

Objective To evaluate the effect of recombinant human erythropoietin (rHuEPO) on brain injury in the patients undergoing cardiac valve replacement with cardiopulmonary bypass (CPB).Methods Forty-five patients with chronic valvular heart disease,aged 36-62 yr,weighing 42-92 kg,of American Society of Anesthesiologists physical status Ⅱ or Ⅲ,with New York Heart Association of Ⅱ or Ⅲ,undergoing cardiac valve replacement with CPB,were randomly divided into 3 groups (n =15 each) using a random number table:control group (group C),and different doses of rHuEPO groups (EPO1 group,EPO2 group).In EPO1 and EPO2 groups,rHuEPO 40 and 80 IU/kg were injected intravenously before anesthesia induction,respectively.Before anesthesia induction (T0,baseline value),immediately after endotracheal intubation (T1),immediately after aortic cannulation (T2),immediately after cannulation of superior and inferior vena cava (T3),immediately after the beginning of CPB (T4),when each index was decreased to the minimal value during CPB (T5),after rewarming to 36.5 ℃ (T6),immediately after termination of CPB (T7),and at 1 h after termination of CPB (T8),regional cerebral oxygen saturation (rSO2),tissue hemoglobin index (THI),and changes in concentrations of oxyhemoglobin (△ O2Hb),deoxyhemoglobin (△ HHb) and total hemoglobin (△ cHb) in bilateral frontal lobes were recorded.The patients whose minimal rSO2 ≤ 50％ and decrease in minimal rSO2 ≥ 20％ of the baseline value (△rSO2) were recorded.At T0,T8 and 2 h after termination of CPB (T9),venous blood samples were taken for determination of serum concentrations of S100 protein and neuron-specific enolase (NSE) by ELISA.At 1 day before surgery and 8 days after surgery,the patient's cognitive function was assessed using Mini-Mental State Examination,the Digit Span subtest of the Wechsler Adult Intelligence Scale-Revised (WAIS-R),the Digit Symbol subtest of the WAIS-R,the Trailing Making Test (Part A)and the Stroop Color Word Interference Test,while depression and anxiety were assessed by Zung Self-Rating Depression Scale and Zung Self-Rating Anxiety Scale,respectively.The occurrence of postoperative cognitive dysfunction was recorded.Results There was no significant difference among the three groups in bilateral rSO2 and △ cHb,incidence of bilateral rSO2 ≤ 50％ and postoperative cognitive dysfunction,Zung Self-Rating Depression Scale score,and Zung Self-Rating anxiety Scale score at each time point (P＞0.05).Compared with group C,the incidence of left △ rSO2 ≥ 20％ was significantly decreased,the right △ O2 Hb was increased at T6,8,the serum NSE concentrations were decreased at T9,the serum S100 protein concentrations were decreased at T8,and the number of the Digit Symbol subtest of the WAIS-R completed was increased in group EPO1,and right THI was significantly decreased at T2,T3,T5,T7 and T8,right △ HHb was increased at T2 and T3,and the completion time of Stroop color word interference test B was shortened at 8 days after surgery in group EPO2 (P＜0.05 or 0.01).Compared with group EPO1,the incidence of left △rSO2 ≥ 20％ was significantly increased,the right THI was decreased at T2-4 and T6-8,and the left △ O2 Hb at T6-7 and right △ O2 Hb at T8 were decreased in group EPO2 (P＜0.05).Conclusion rHuEPO 40 IU/kg injected intravenously before induction of anesthesia can mitigate brain injury in the patients undergoing cardiac valve replacement with CPB.