BACKGROUND:3D-printed bone tissue engineering scaffolds have obvious advantages in the research and clinical treatment of bone defect repair.As one of the important raw materials for 3D printed bone scaffolds,poly-L-lactic acid has a great potential for application in performing bone defect repair,but clinical patients with different bone defect causative factors have different requirements for the comprehensive performance of poly-L-lactic acid bone scaffolds.OBJECTIVE:To summarize and review the development of 3D printing technology and poly-L-lactic acid scaffolds and the design strategies chosen for scaffolds for bone repair in the setting of bone diseases such as osteomyelitis,bone tumor,osteonecrosis,and osteoporosis.METHODS:Literature from CNKI,WanFang,PubMed,Science Direct,and Web of Science databases were searched and screened from 1994 to 2024.Search terms were"3D printing,polylactic acid,bone tissue engineering scaffold,osteomyelitis,bone tumor,osteonecrosis,osteoporosis,bone defect"in Chinese and English.The screened 62 articles were systematically summarized and analyzed.RESULTS AND CONCLUSION:(1)Poly-L-lactic acid is considered to be an ideal raw material for artificial bone scaffold design due to its non-toxicity,processability,biocompatibility,and ability to self-degrade in the human environment.The application of 3D printing technology has enabled poly-L-lactic acid bone scaffolds to meet the multilayered and porous structural design requirements of biomimetic artificial bone repair materials,and to optimize the mechanical properties for better bone repair.(2)According to different bone disease microenvironments,timely adjustment of the functional design of poly-L-lactic acid scaffolds is important for the comprehensive osteogenic efficacy of the scaffolds.The article discusses the application of poly-L-lactic acid scaffolds in bone disease environments such as osteomyelitis,bone tumor,osteonecrosis,and osteoporosis,and highlights the importance of rationally grasping the timing of bone disease treatment and bone tissue regeneration for bone defects caused by different bone diseases.(3)Although poly-L-lactic acid scaffolds show potential in bone repair,there are still some problems,such as the need to further optimize the structural design of the scaffolds to fit new bone regeneration,enhance the bioactivity of the scaffolds,and take into account other functions(e.g.,antimicrobial,anti-tumor,and anti-osteoporosis)in order to adapt to the needs of bone tissue repair in different pathological environments.

BACKGROUND:3D-printed bone tissue engineering scaffolds have obvious advantages in the research and clinical treatment of bone defect repair.As one of the important raw materials for 3D printed bone scaffolds,poly-L-lactic acid has a great potential for application in performing bone defect repair,but clinical patients with different bone defect causative factors have different requirements for the comprehensive performance of poly-L-lactic acid bone scaffolds.OBJECTIVE:To summarize and review the development of 3D printing technology and poly-L-lactic acid scaffolds and the design strategies chosen for scaffolds for bone repair in the setting of bone diseases such as osteomyelitis,bone tumor,osteonecrosis,and osteoporosis.METHODS:Literature from CNKI,WanFang,PubMed,Science Direct,and Web of Science databases were searched and screened from 1994 to 2024.Search terms were"3D printing,polylactic acid,bone tissue engineering scaffold,osteomyelitis,bone tumor,osteonecrosis,osteoporosis,bone defect"in Chinese and English.The screened 62 articles were systematically summarized and analyzed.RESULTS AND CONCLUSION:(1)Poly-L-lactic acid is considered to be an ideal raw material for artificial bone scaffold design due to its non-toxicity,processability,biocompatibility,and ability to self-degrade in the human environment.The application of 3D printing technology has enabled poly-L-lactic acid bone scaffolds to meet the multilayered and porous structural design requirements of biomimetic artificial bone repair materials,and to optimize the mechanical properties for better bone repair.(2)According to different bone disease microenvironments,timely adjustment of the functional design of poly-L-lactic acid scaffolds is important for the comprehensive osteogenic efficacy of the scaffolds.The article discusses the application of poly-L-lactic acid scaffolds in bone disease environments such as osteomyelitis,bone tumor,osteonecrosis,and osteoporosis,and highlights the importance of rationally grasping the timing of bone disease treatment and bone tissue regeneration for bone defects caused by different bone diseases.(3)Although poly-L-lactic acid scaffolds show potential in bone repair,there are still some problems,such as the need to further optimize the structural design of the scaffolds to fit new bone regeneration,enhance the bioactivity of the scaffolds,and take into account other functions(e.g.,antimicrobial,anti-tumor,and anti-osteoporosis)in order to adapt to the needs of bone tissue repair in different pathological environments.

BACKGROUND:Careful regulation of bone immune response during repair of bone scaffold is important for bone regeneration. OBJECTIVE:To review the influence of bone immune response on bone repair and the design of bone tissue engineering scaffold with regulating bone immune function and its application in bone repair. METHODS:Relevant articles published from 1973 to 2023 were retrieved from Science Direct,PubMed,Web of Science,and CNKI databases.English search terms were"osteoimmunology,macrophages,bone repair materials,bone scaffold,bone defects,bone regeneration".Chinese search terms were"bone immunity,macrophages,bone repair material,bone stent,bone defect,bone regeneration".Totally 80 articles of the latest research progress in this field were summarized and analyzed. RESULTS AND CONCLUSION:(1)A detailed review was conducted on the important time points in the origin and development process of bone immunity,and it was explained that macrophages,as important members of the bone immune regulatory system,can be divided into two phenotypes:M1(pro-inflammatory)and M2(anti-inflammatory),and play a key role in different stages of bone regeneration.During the inflammatory phase,M1 type macrophages can activate osteoclasts,initiate tissue repair processes,and participate in the reconstruction of bone microvascular networks.On the other hand,during the bone tissue regeneration process in the later stages of inflammation,sustained high expression of M1 type macrophages can hinder the formation of new bones.During the repair phase,M2 macrophages can secrete osteogenic cytokines,stimulate osteogenic differentiation and mineralization of bone marrow mesenchymal stem cells,and promote bone formation.On the other hand,long-term activation of M2 macrophages can increase the secretion of fibrogenic molecules,leading to excessive formation of scar tissue and delaying the healing process.Therefore,regulating macrophages to undergo phenotype transformation at appropriate stages and constructing an immune microenvironment beneficial for osteogenesis has great significance for bone regeneration.(2)In the process of designing bone scaffolds with bone immune regulation characteristics,the physical and chemical properties such as scaffold roughness,pore structure,stiffness,hydrophilicity,surface charge,and surface functional groups can be changed to affect non-specific protein and cell adhesion,thereby affecting the interaction between bone scaffolds and the immune system.By designing surface functional coatings of bioactive substances such as hydroxyapatite,bioactive glass,metal ions,extracellular matrix,drugs,cytokines,and exosomes,the immune microenvironment can be actively regulated by releasing bioactive substances after implantation into the body,affecting macrophage polarization and crosstalk between macrophages and bone cells,and promoting more M2 polarization of macrophages,so as to build a bone immune microenvironment that is conducive to bone regeneration.(3)Based on the research and development of bone tissue engineering scaffolds,in addition to focusing on the direct regulatory factors of stem cell osteogenic differentiation,this article also proposes that attention should be paid to the management of the immune microenvironment of stem cell differentiation.By regulating the appropriate bone immune microenvironment,more stem cell osteogenic differentiation can be induced;the osteogenic efficiency of the scaffold can be enhanced,and the concept of"bone immune regulatory characteristics"can be condensed;deeply elucidated the multi-directional regulatory role of the bone immune microenvironment and introduced the existing strategies for changing the physicochemical properties and surface functional coating of scaffolds to endow them with bone immune regulatory potential,providing new ideas for guiding the development of a new generation of bone tissue engineering scaffolds with bone immune regulatory characteristics.However,the bone immune microenvironment is a dynamic equilibrium state,and most of the existing regulatory strategies do not consider the dynamic matching of regulation.Therefore,the research and development of intelligent bone immune regulatory scaffolds with efficient and targeted regulation of the immune microenvironment will be a key focus of attention for scholars in future.

Objective    To study the relationship between preoperative heart rate variability (HRV) and postoperative atrial fibrillation (POAF) after off-pump coronary artery bypass grafting (OPCAB). Methods    A retrospective analysis was performed on the clinical data of 290 patients who were admitted to the Department of Cardiovascular Surgery, General Hospital of Northern Theater Command from May to September 2020 and received OPCAB. There were 217 males and 73 females aged 36-80 years. According to the incidence of POAF, the patients were divided into two groups: a non-atrial fibrillation group (208 patients) and an atrial fibrillation group (82 patients). The time domain and frequency domain factors of mean HRV 7 days before operation were calculated: standard deviation of all normal-to-normal intervals (SDNN), root mean square of successive differences, percentage difference between adjacent normal-to-normal intervals that were greater than 50 ms, low frequency power (LF), high frequency power (HF), LF/HF. Results    The HRV value of patients without POAF was significantly lower than that of patients with POAF (P<0.05). The median SDNN of the two groups were 78.90 ms and 91.55 ms, respectively. Age (OR=3.630, 95%CI 2.015-6.542, P<0.001), left atrial diameter (OR=1.074, 95%CI 1.000-1.155, P=0.046), and SDNN (OR=1.017, 95%CI 1.002-1.032, P=0.024) were independently associated with the risk of POPAF after OPCAB. Conclusion     SDNN may be an independent predictor of POAF after OPCAB.

Objective We probed how to predict left ventricular ejection fraction (LVEF) of the ischaemic cardiomyopathy (ICM) patients would be improved apparently after revascularization. Methods Between July 2010 and December 2015, 245 ICM patients (30%≤LVEF≤40%) with coronary bypass grafting (CABG) were retrospectively observed. Among them, 146 patients were accompanied by ischemic mitral regurgitation (IMR) (146/245, 59.6%), and 41 patients underwent mitral valvuloplasty or replacement because of more than moderate IMR. There were 13 patients early death, and other 232 patients who were followed up over 6 months were divided into two groups based on whether or not post-operative LVEF increased by 10%: a LVEF recovered group (group A, 124 patients) and a non-recovered group (group B, 108 patients). Results Preoperative NT-proBNP in the group A was significantly higher than that in the group B (P=0.036). There were less patients with myocardial infarction in the group A than that in the group B (P=0.047), and more with angina pectoris in the group A than that in the group B (P=0.024). There was no significant difference in the extent of mitral regurgitation or mitral surgery between the groups A and B (P>0.05). There were lower left ventricular end-diastolic diameter (LVEDD), left ventricular end-systolic diameter (LVESD) and left ventricular end-diastolic volume (LVEDV) in the group A than those in the group B (P<0.05). Multivariate analysis revealed that preoperative LVEDD dilated apparently and no angina pectoris existed before surgery were independent risk factors for LVEF with no recovery in the ICM patients (30%≤LVEF≤40%) after revascularization. The LVEDD of 245 patients (including 13 early deaths) was 41-71 mm. We found that the ICM patients with LVEDD ≥60 mm were more likely to signify the unfavourable prognosis (χ2=8.63, P=0.003, OR=2.21, 95% confidence interval 1.25 to 3.91). Conclusion Preoperative LVEDD dilated and no angina pectoris before surgery are independent risk factors for LVEF with no recovery in the ICM patients (30%≤LVEF≤40%) after revascularization. LVEDD≥60 mm can be regarded as the preoperative forecasting factors for the unfavourable prognosis in the ICM patients (30%≤LVEF≤40%) after revascularization.

Objective To evaluate the short-term-outcome of MVP in the treatment of moderate IMR patients with CABG.Methods Data from 129 patients with moderate IMR who underwent surgical treatment in our department from June 2007 to September 2011,57 patients(44.2％) underwent CABG combined with MVP,and 72 patients(55.8％) underwent CABG.Postoperative follow-up of patients with heart function NYHA grade to evaluate the clinical status of patients,with LVESD,LVEF,LVEDD to evaluate the reverse of left ventricular remodeling;The postoperative residual mitral regurgitation and major cardiac cerebral vascular events were recorded.Results There was no significant difference between two groups in the preoperative data(P ＞ 0.05).The mortality rate was 3.9％ (5 cases),2 cases (2.8 ％) died in CABG group,3 cases (5.3 ％) died in the combined surgery group.The average follow-up was 24 months,9 cases of late death (5 in CABG group,4 in CABG + MVP group),the cumulative survival rate(P =0.645) and the major cardiovascular events(P =0.761) of the two groups were not statistically different.The degree of mitral regurgitation(P ＜ 0.01) was significantly decreased in the combined surgery group.Compared with the preoperative state,the two groups of left ventricular remodeling indicators such as LVESD,LVEF,LVEDD were significantly improved(P ＜0.05),but the difference between two groups was not significant(P ＞0.05).NYHA heart function classification was significantly improved (P ＜ 0.001).Conclusion MVP can effectively improve the reverse flow of patients with moderate IMR,but CABG combined with MVP can not bring more benefits in the reversal of left ventricular remodeling,short-term survival and cardiac function.

Objective To evaluate the different cardioprotective function of transplantation of marrow mesenchymal stem cells(BMSCs) from coronary heart disease(CHD) patients with diabetes mellitus (DM) or not to myocardial infarction rats.Methods 45 adult male rats with acute myocardial infarction experimentally were randomized into three groups,15 rats in each group.BMSCs from CHD patients with DM or not were injected into the infarcted myocardium.In control group,culture medium was used.Echocardiography,Western-blot analysis,TUNEL were performed 4 weeks after transplantation.Results Proliferation of BMSCs in DM group was significantly lower than that in non-DM group.Transplantation of BMSCs in the infarcted border zone improved cardiac function,Bcl-2 protein level in DM and non-DM group compared with control group,moreover,BAX protein level and TUNEL positive cells were decreased.Furthermore,compared with non-DM group,cardiac function and Bcl-2 protein level were decreased,however,BAX protein and TUNEL positive cells were improved.Conclusion BMSCs from CHD patients have proliferative properties.Transplantation of BMSCs can improve cardiac function by inhibiting apoptosis.But DM may decrease apoptosis resistance,which might impair the cardioprotective function of cells transplantation.

Objecttve To determine whether non-adherent bone marrow-derived mesenchymal stem cells (NA-BM-MSC) can differentiate into neuron-like cells in vitro and in vivo,especially in ischemic brain of mice. Methods NA-BM-MSC of mouse were indueed with conditioned medium containing epidermal growth factor and basic-fibroblast growth factor and demonstrated by immunocytochemistry for the expression of neuron specific nuclear protein and neurofilament-200. NA-BM-MSC from β-galactosidase transgenic mice constitutively expressing β-galactosidase were transplanted into the mice model of middle cerebral artery occlusion.LacZ staining and immunobistochemistry staining were performed to detect the survival,distribution and the differentiation of the donor cells in the ischemic brain. Results NA-BM-MSC can be induced into neuron specific nuclear protein and neurofilament-200 positive cells in vitro.LacZ staining showed that NA-BM-MSC can survive in ischemic brain and express β-galactosidase.Also,numbers of the neuron specific nuclear protein positive cells in β-galactosidase-positive cells were detected in the ischemic brain with double immunohistochemistry staining. Conclusions NA-BM-BMC can be induced to differentiate into neuron-like cells in vitro,and also can differentiate into neuron-like cells in ischemic brain tissue of the mice.

Objective To investigate the localization and expression of endothelial nitric oxide synthase (eNOS) within the wall of the human internal mammary arteries (LMA), radial arteries (RA) and the great saphenous veins (SV) using immunohistochemistry method. Methods Specimens were harvested from 20 patients undergoing coronary artery bypass grafting and submitted to light microscope analysis using immunohistochemistry method. Results The expression of eNOS was evident in the intima of LIMA, RA and SV and in the media of muscular LIMA and RA. No eNOS expression was found in the media of great saphenous veins. Semiquantitative and the imaging analysis indicated by gray level values revealed a higher eNOS expression in the wall of internal mammary artery, particularly at the level of the media. Conclusion Different expression of eNOS in the intima and media of LIMA, RA and SV may provide a histological explanation for the better results of the LIMA when used for coronary artery bypass grafting.

Objective To review the experience of treatment of atrial fibrillation (AF) after coronary artery bypass grafting (CABG), and to analyze its risk factors. Methods 110 patients were subjected to CABG. AF occurred in 26 of them after surgery. All these patients were treated with drugs or direct current. AF group and non-AF group were studied retrospectively, with an analysis of risk factors of AF. Results The incidence of AF after CABG was 23.6%. 19 patients were treated with Amiodarone, and 17 of them had sinus rhythm restored to normal (84.2%). In 3 of 4 patients, who were treated with Esmolol, sinus rhythm restored to normal (75%). All 3 patients who were treated with direct current had their sinus rhythm restored. The occurrence of AF was related to age, volume of left atrium, pathological change in proximal-median segment of right coronary artery, and the administration of ?-receptor blockade before surgery. It was indicated by logistic regression multiple factors analysis that both advanced age and abstinence of administration of ?-receptor blockade before surgery were individual risk factors for AF. Conclusion Ventricular rhythm should be controlled positively when AF occurred after CABG. Amiodarone, Esmolol and direct current were safe and effective treatment modalities. Patients with advanced age, large left atrium and pathological change in proximal-median segment of right coronary artery, should be treated with ?-receptor blockade to prevent AF.