Doxycycline stabilizes vulnerable plaque via inhibiting matrix metalloproteinases and attenuating inflammation in rabbits

Enhanced matrix metalloproteinases (MMPs) activity is implicated in the process of atherosclerotic plaque instability. We hypothesized that doxycycline, a broad MMPs inhibitor, was as effective as simvastatin in reducing the incidence of plaque disruption. Thirty rabbits underwent aortic balloon injury and were fed a high-fat diet for 20 weeks. At the end of week 8, the rabbits were divided into three groups for 12-week treatment: a doxycycline-treated group that received oral doxycycline at a dose of 10 mg/kg/d, a simvastatin-treated group that received oral simvastatin at a dose of 5 mg/kg/d, and a control group that received no treatment. At the end of week 20, pharmacological triggering was performed to induce plaque rupture. Biochemical, ultrasonographic, pathologic, immunohistochemical and mRNA expression studies were performed. The results showed that oral administration of doxycycline resulted in a significant increase in the thickness of the fibrous cap of the aortic plaque whereas there was a substantial reduction of MMPs expression, local and systemic inflammation, and aortic plaque vulnerability. The incidence of plaque rupture with either treatment (0% for both) was significantly lower than that for controls (56.0%, P<0.05). There was no significant difference between doxycycline-treated group and simvastatin-treated group in any serological, ultrasonographic, pathologic, immunohistochemical and mRNA expression measurement except for the serum lipid levels that were higher with doxycycline than with simvastatin treatment. In conclusion, doxycycline at a common antimicrobial dose stabilizes atherosclerotic lesions via inhibiting matrix metalloproteinases and attenuating inflammation in a rabbit model of vulnerable plaque. These effects were similar to a large dose of simvastatin and independent of serum lipid levels.     

Mesenchymal stem cell sheet transplantation combined with locally released simvastatin enhances bone formation in a rat tibia osteotomy model

Nonunion of fractured bones is a common clinical problem for orthopedic surgeons. This study aimed to investigate the effects of simvastatin locally applied from calcium sulfate (CS) combined with a mesenchymal stem cell (MSC) sheet on fracture healing. In vitro, the proliferation and differentiation of rat bone marrow–derived MSCs stimulated by simvastatin were investigated. In vivo, an osteotomy model was made in rat tibia, and fractured tibias were treated with CS, CS/simvastatin, CS/MSC sheet or simvastatin-loaded CS with MSC or untreated (control). Tibias were harvested at 2 or 8 weeks and underwent real-time quantitative polymerase chain reaction, x-ray, micro-CT and histological analysis. The expression levels of bone morphogenetic protein 2, alkaline phosphatase, osteocalcin, osteoprotegerin and vascular endothelial growth factor of simvastatin-induced MSCs increased with the concentrations of the simvastatin, significantly higher than those in the MSCs group. At 2 weeks, the CS/simvastatin/MSC sheet group showed significantly higher expressions of bone morphogenetic protein 2, alkaline phosphatase, osteocalcin, osteoprotegerin and vascular endothelial growth factor, with more callus formation around the fracture site compared with the other four groups. At 8 weeks, complete bone union was obtained in the CS/simvastatin/MSC sheet group. By contrast, newly regenerated bone tissue partially bridged the gap in the CS/simvastatin group and the CS/MSC sheet group; the control and CS group showed nonunion of the tibia. These results show that both simvastatin and the MSC sheet contributed to the formation of new bone and that the tibia fracture was completely healed by transplantation of the MSC sheet with locally applied simvastatin. Such MSC sheet with locally applied simvastatin might contribute to the treatment of fractures, bone delayed unions or nonunions in clinical practice.     

Autologous mesenchymal stem cells loaded in Gelfoam<Superscript>®</Superscript> for structural bone allograft healing in rabbits

This study was designed to evaluate the effect of autologous bone marrow mesenchymal stem cells (MSCs) seeded into Gelfoam^® on structural bone allograft healing. Thirty New Zealand white rabbits were divided into two groups. Segmental bone defect was created on diaphysis of the femur, and the defect was reconstructed with structural bone allograft. In experimental group, structural allograft was wrapped around by Gelfoam^® containing autologous MSCs, whereas cells were not included in control group. At 4, 8, 12 weeks, the femur of rabbits underwent radiographic and histologic evaluation for bony union. Bone morphogenic protein-2 (BMP-2), BMP-4, BMP-7, vascular endothelial growth factor (VEGF), and receptor activator of nuclear factor-kappa B ligand (RANKL) were measured within the grafted periosteal tissue. Bony union was not achieved in both groups at 4 and 8 weeks. At 12 weeks, three out of five femurs in experimental group were united, but one out of five in control group was united. Mean Taira scores were significantly different between two groups. The expression of BMP-2 was significantly higher at 4, 8 weeks, the expressions of BMP-4 and BMP-7 were significantly higher at 8 and 12 weeks, and the expression of VEGF and RANKL were significantly higher at all time points in experimental group. Incorporation of the structural bone allograft could be enhanced if allograft is covered with Gelfoam^® containing autologous MSCs. MSCs have influence on not only bone formation, but neo-angiogenesis, and bone resorption.     

bFGF/BMP/胶原膜加速颌骨骨折愈合的大体及X线观察

目的：了解胶原膜作为生长因子缓释材料治疗颌骨骨折的应用前景。方法：将100μg的rhBMP-2用1ml的bFGF溶液完全溶解;用移液器移出40μl的该溶液,滴加到面积为0.5cm×1cm的胶原膜组织块中,冻干后制成生长因子缓释系统;在12只新西兰大白兔两侧制成人工下颌骨骨折模型,左侧置放bFGF/BMP/胶原膜;右侧均为空白对照;术后2、4、12周行临床大体观察及X线片观察。结果：实验组骨折愈合速度明显快于对照组。术后2周,X线结果显示bFGF/BMP/胶原膜组骨折断端边缘模糊。对照组骨折线明显。术后4周,X线结果显示bFGF/BMP/胶原膜骨折线基本不可见,骨折对位良好,断端边缘基本消失,骨折无错位。对照组骨折下缘可见纤维性骨痂形成,骨折线模糊。术后12周,各组X线结果无差异,骨折部位接近正常骨组织。结论：bFGF/BMP/胶原膜能加速骨折愈合,提高骨折愈合效果。     

髓腔内固定联合低强度脉冲超声对兔股骨中段骨折愈合作用研究

摘要 目的：针对髓腔内固定联合低强度脉冲超声对兔股骨中段骨折愈合作用进行研究。方法：选择成年兔股骨中段骨折40只,作为本次的研究对象,将其平均分为对照组和观察组。所有兔子,在手术前禁水、禁食,对其右后肢进行备皮,称重、麻醉,对照组实施髓腔内固定治疗,观察组实施髓腔内固定联合低强度脉冲超声治疗。治疗后1、2、3、4周对兔子的骨折部位进行影像学检查确定兔子的骨折线模糊情况,并在各周采集样品进行组织学检查。治疗4周后对骨折愈合情况进行检查。结果：观察组愈合程度I级、II级、II级比例均低于对照组相应比例,差异具有统计学意义（P＜0.05）,观察组IV级、V级比例分别为35.0 %、55.0 %,均高于对照组的5.0 %、5.0 %,差异具有统计学意义（P＜0.05）;观察组兔子的在1 w、2 w、3 w、4 w骨折线模糊程度评分高于对照组相应时间评分,差异具有统计学意义（P＜0.05）。结论：在兔股骨中断骨折治疗中,实施髓腔内固定联合低强度脉冲超声,可以提高骨折的愈合速度,加速骨折修复,整体治疗效果显著,可以在临床上进行推广实施。     

The effects of Lepidium sativum seeds on fracture-induced healing in rabbits

The Lepidium sativum plant and seeds are well known in the community of Saudi Arabia and some other Arabic countries as a good mediator for fracture healing in the human skeleton. However, there is no scientific proof for this phenomenon, except for the positive observation noted publicly by traditional medicine practitioners and people in the community as well as clinically by the author. Those healed fractures in human beings observed clinically due to the consumption of L sativum seeds propagated the attention of the author to carry out this study, with the goal of proving it in the laboratory by inducing fractures in the midshaft of the left femur of 6 adult New Zealand White rabbits divided into 2 groups (control, n = 3 and test, n = 3). The test rabbits were fed soon after surgery with L sativum seeds mixed with their normal diet, whereas no seeds were given to the control group. X-rays of the induced fractures were taken at 6 and 12 weeks postoperatively to assess the healing of the fractures and documenting the healing by direct measurements of callus formation in millimeters at the longitudinal medial (LM) and longitudinal lateral (LL) and circumferential (CM) areas. The test group had a statistically significant increase in the healing of fractures compared with the control group (P < .001 for CM/6 weeks and P < .004 for CM and P < .043 for LM/12 weeks). We concluded that L sativum seeds had a marked influence on fracture healing in rabbits, clearly supporting their effects on human beings as a well-known natural element to promote fracture healing in traditional medicine. This, of course, has a marked clinical implication that needs to be investigated further.     

多孔n-HA/PA66支架复合rhBMP-2修复兔桡骨缺损的实验研究

目的 ：研究多孔纳米羟基磷灰石/聚酰胺66（nHA/PA66）骨修复材料作为骨组织工程支架复合基因重组人骨形态发生蛋白2（rhBMP2）后的成骨能力的变化,探讨加速nHA/PA66人工骨与受体骨愈合的方法。方法：选用新西兰大白兔双侧桡骨制作骨缺损模型,将nHA/PA66/rhBMP2复合材料植入左侧骨缺损处,右侧骨缺损以nHA/PA66植入作为实验对照,另做不植入任何材料的骨缺损空白对照。在1、2、4、8、12周各时相点分别进行大体观察、X线照片、组织学切片、免疫组化原位杂交进行检测图象分析。结果：nHA/PA66/BMP2与nHA/PA66组骨缺损均完全修复,而空白对照组骨缺损未见修复;2周时nHA/PA66与nHA/PA66/rhBMP2两组间原位杂交阳性细胞表达有统计学意义（ P<0.05）, 4周时nHA/PA66与nHA/PA66/rhBMP2两组间原位杂交阳性细胞表达无统计学意义（ P>0.05）,2周及4周实验和实验对照两组分别与空白对照组比较均无统计学意义（ P>0.05）,nHA/PA66/rhBMP2组较nHA/PA66组可加速人工骨/植入体/受体界面骨愈合。 结论：多孔nHA/PA66作为骨组织工程支架复合具有诱导成骨活性的rhBMP2后,增强了早期成骨能力,加速了其与受体骨的愈合。     

Increased levels of monohydroxy metabolites of arachidonic acid and linoleic acid in LDL and aorta from atherosclerotic rabbits.

Lipid peroxidation results in the formation of peroxy and hydroperoxy metabolites of polyunsaturated fatty acids which can directly or indirectly affect many cellular processes. Lipid hydroperoxides are rapidly metabolized to the corresponding monohydroxy products by various cellular peroxidases. We have measured the amounts of monohydroxy metabolites of linoleic acid (18:2) and arachidonic acid (20:4) in lipids derived from aorta and LDL from rabbits fed a diet enriched in cholesterol and peanut oil for either 8 or 15 weeks. Increased amounts of the 9-hydroxy, and, to a lesser extent, the 13-hydroxy metabolite of 18:2 were observed in aorta and LDL from cholesterol-fed rabbits at both 8 and 15 weeks. The amounts of esterified 11-, 12- and 15-hydroxy metabolites of 20:4 in aortae from cholesterol-fed rabbits were similar to controls after 8 weeks, but about 3-fold higher after 15 weeks. These monohydroxy metabolites of 20:4 were also detected in LDL lipids in cholesterol-fed rabbits. The greater amounts of hydroxy-18:2 in the cholesterol-fed group could be explained by an approx. 2-4-fold increase in 18:2 in aorta and LDL. In contrast, the amounts of 20:4 in aortic lipids were lower in cholesterol-fed rabbits than in controls. Thus, the percentage of esterified 20:4 which had been oxidized to its 11, 12, and 15-hydroxylated metabolites was about 5-times higher in the cholesterol-fed group. Our results would be consistent with the hypothesis that increased amounts of peroxidized 18:2 and 20:4 in lipids could be involved in the development of atherosclerotic lesions in cholesterol-fed rabbits.     

Ameliorative effects of autophagy inducer,simvastatin on alcohol-induced liver disease in a rat model

Alcoholic liver disease (ALD) encompasses a variety of liver injuries with various underlying mechanisms but still no effective treatment. So we aimed to monitor the influence of simvastatin on alcohol-induced liver injury and elucidate the underlying mechanisms of its cytoprotective effect. Thirty male albino rats were randomly divided into five equal groups. Group 1 (control): received a standard diet; group 2: received simvastatin (10 mg kg⁻¹ day ⁻¹) once a day orally for 8 weeks; group 3: received 20% ethanol (7.9 g kg ⁻¹ day ⁻¹) daily orally for 8 weeks; group 4: received 20% ethanol along with same simvastatin dose daily for 8 weeks; group 5: received 20% ethanol orally for 8 weeks then received the same simvastatin dose for the next 8 weeks. Serum alanine aminotransferase, aspartate aminotransferase, total cholesterol, triglycerides, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol were measured. Liver tissue malondialdehyde, reduced glutathione levels, and superoxide dismutase activity were estimated. B-cell lymphoma 2 and C/EBP homologous protein levels were evaluated by enzyme linked immunosorbent assay (ELISA). Light chain 3-II and peroxisome proliferation-activated receptor gamma messenger RNA expression was assessed by real-time polymerase chain reaction. Immunohistochemical staining was performed using anti-rat tumor necrosis factor-alpha antibody. Our results revealed that simvastatin treatment was able to ameliorate alcohol-induced liver damage; the improved biochemical data were confirmed by histopathological evaluation. Simvastatin being an autophagy inducer was able to prevent and reverse alcohol-induced liver changes via induction of autophagy, attenuation of oxidative stress, inflammation, and endoplasmic reticulum stress-induced apoptosis. Therefore, our findings suggest that treatment with simvastatin may be a useful approach in the management strategy of ALD.     

Simvastatin与rhG—CSF促进兔颈总动脉球囊损伤后内膜修复的实验研究

目的：观察辛伐他汀及重组人粒细胞集落刺激因子（rhG—CSF）在兔颈总动脉内膜损伤后对血管壁变化及外周血中CD34＋细胞含量的影响。方法：雄性新西兰大白兔48只,随机均分为：单纯损伤组,辛伐他汀组,rhG—CSF组及辛伐他汀和rhG—CSF联合组（简称联合组）,建立兔左颈总动脉内膜球囊导管损伤模型,术后给予辛伐他汀（10mg／kg／d经胃灌入）及rhG．CSF（100μg／a皮下注射）干预治疗,每组分别于术前1d、术后7d、14d、21d、28d抽取静脉血2ml,经流式细胞仪检测外周血中CD34＋细胞含量;4周后处死所有动物取损伤段血管,弹力纤维染色,计算内膜厚度、中膜厚度、管腔面积（S）、内膜面积（si）、中膜面积（Sm）TLSi／Sm比值评价血管再狭窄程度。结果：①术前4组之间相比外周血CD34＋细胞含量无明显差异（P〉0．05）;术后7d时各组外周血CD34＋细胞含量最高,后逐渐下降,28d较低,但仍高于术前含量;rhG—CSF组及联合组与对照组相比外周血CD34＋细胞明显增多（P〈O．01,P〈0．01）;术后7d、14天时辛伐他汀组与单纯损伤组相比外周血cD34＋细胞无明显差别（P〉0．05）。术后21d、28天时辛伐他汀组与单纯损伤组相比外周血CD34＋细胞有显著差异（P〈0．05）。②与单纯损伤组相比辛伐他汀组、rhG—CSF组及联合组Si／Sm比值明显减小（P〈0．05）;辛伐他汀组和rhG—CSF组两组间比较无显著差别（P〉0．05）;联合组分别与辛伐他汀组、rhG-CSF组比较血管内膜增生更少,具有显著性（P〈0．01,P〈0．01）,结论：本实验研究发现辛伐他汀可促进损伤内膜修复及预防血管再狭窄,长期服用可以增加外周血CD34＋细胞;rhG—CSF可明显增加外周血CD34＋细胞及预防血管在狭窄;辛伐他汀与rhG—CSF联合用药可明显增加外周血CD34＋细胞、加速内皮修复与预防再狭窄,较单一用药具有更好的疗效。     

The healing of facial bone fractures by the process of secondary union

The mechanism of healing of facial bone fractures was investigated in a rabbit model. Twelve New Zealand white rabbits underwent surgically induced fractures of the right infraorbital rim and fracture ostectomies (4 to 5 mm) of the left infraorbital rim. Animals were sacrificed 2, 4, and 8 weeks postfracture. Bone, including periosteum, obtained from each fracture or fracture osteoctomy site was divided longitudinally for hematoxylin and eosin staining, fluorescent microscopy, microangiography, and microradiography. Sequential fluorochrome labels of oxytetracycline (30 mg/kg), alizarin complexone (30 mg/kg), DCAF (20 mg/kg), and xylenol orange (90 mg/kg) were administered 24 hours preoperatively and at 1, 2, 4, and 8 weeks postfracture. All fracture and fracture ostectomy sites demonstrated vascular ingrowth, mineralization, and woven bone formation by 2 to 4 weeks postoperatively, beginning with a cartilage precursor. Subsequently, the woven bone was replaced with remodeled lamellar bone, resulting in complete bony healing by 8 weeks postoperatively. These steps were substantiated by microscopic, microradiographic, and radiologic examination of the specimens. This study demonstrates that fractures of the facial bones in a rabbit model heal by a process of new bone formation that resembles secondary union in endochondral bones.     

干预脂毒性改善糖尿病大鼠胰岛素分泌及氧化应激的损害

目的探讨干预脂毒性改善糖尿病大鼠胰岛分泌功能及氧化应激损害的机制。方法将大鼠分为4组①正常组（NC）,全程普通饲料喂养;②高脂组（HF）,全程高脂饲料喂养。糖尿病组,高脂饲料喂养8周后腹腔注射低剂量STZ（30mg/kg）,48h后行OGTT试验判断成模情况后分组。③糖尿病对照组（DM）,不给予药物干预;④血脂干预组（SIM）,灌胃辛伐他汀5mg/（kg.d）4周干预脂毒性。通过免疫组化染色观察胰岛B、A细胞形态学特点,RT-PCR测定胰腺内胰岛素原mRNA表达水平,DHE荧光染色检测胰岛中活性氧化产物ROS水平。结果与糖尿病对照组相比,干预脂毒性4周后血清胆固醇（TC）和甘油三酯（TG）水平分别下降了22.9%（P〈0.01）和57.0%（P〈0.05）。OGTT血糖水平均显著下降（P〈0.01）。胰岛中B细胞相对量是对照组的2.6倍（P〈0.01）,B细胞胞质内胰岛素水平增加了26.5%（P〈0.05）,胰岛素原mRNA表达升高18.3%（P〈0.01）;A细胞相对量减少了50%（P〈0.01）。血清丙二醛（MDA）水平和胰腺中ROS表达显著下降。结论辛伐他汀干预脂毒性4周可以显著改善糖尿病大鼠胰岛分泌功能和氧化应激损害。     

Age-related changes in the biomechanics of healing patellar tendon

By 2030, there will be 70 million people in the United States over the age of 65, and by 2050, 22% of the US population will be considered elderly. It is generally believed that injuries in the elderly heal slower and less completely than in adolescents or young adults. To evaluate aging effects on tissue repair a surgical injury was created in the middle third of one patellar tendon in 1- and 4-5-year-old New Zealand White rabbits. The biomechanical properties of the isolated repair tissues and contralateral normal tendon tissues were compared at 6, 12 and 26 weeks post-injury. We hypothesized that repair tissues would exhibit age-related reductions in biomechanical properties at all time intervals of healing, both based on raw data and when normalized to values from contralateral tendons. Repairs from both age groups were similar, with no significant increase in maximum stress, strain at maximum stress, or modulus between 6 and 12 weeks. At 26 weeks, the repairs in the 4-year-old rabbits had higher maximum stress values than repairs in the 1-year-old rabbits (p=0.03). There were no significant differences in the strain at maximum stress or modulus. When repair tissue properties were normalized to values in the contralateral normal tendon, the maximum stress of the patellar tendon repair tissue from the 4 year old was significantly greater than the corresponding value from the 1 year old at the 26 week time point (p=0.04). In conclusion, these findings do not support the presence of age-related declines in the biomechanics of healing tendon.     

Enhancement of tendon-bone healing with the use of bone morphogenetic protein-2 inserted into the suture anchor hole in a rabbit patellar tendon model

Background aimsSuture anchor fixation failure has been reported as a result of anchor loosening and migration during the tendon-bone repair. The aim of this study was to evaluate the effects of bone morphogenetic protein-2 (BMP-2) inserted into the suture anchor hole on bone formation and the tendon-bone healing.MethodsBoth back legs of 24 New Zealand White rabbits (n = 48) were used in this study. A metal suture anchor was then placed 5 mm below the cortex. In the control group, the space over the eyelet of the anchor (suture anchor hole) was not filled. In the experimental group, the suture anchor hole was filled with 0.1 mL of fibrin glue (group 2) or collagen gel (group 3) with 1 μg BMP-2. Histologic analysis, real-time-polymerase chain reaction, bone density and failure load measurement were performed, and differences were analyzed at 4 and 8 weeks.ResultsHistologic analysis revealed more abundant new bone, mature bone and organized fibrocartilage at the tendon-bone interface at 4 and 8 weeks in groups in which BMP-2 was applied. At 8 weeks, the failure load of groups 1, 2 and 3 was significantly different among the three groups (P = 0.01). After post hoc Tukey test, the failure load of group 2 was significantly higher than that of group 1 (P = 0.01).ConclusionsBMP-2, administrated as described in this study, improved tendon-bone healing and bone formation, resulting in improved biomechanical strength of the tendon-bone junction.     

Prostaglandin E1 dose-dependently promotes stability of atherosclerotic plaque in a rabbit model

This study evaluated the effect of prostaglandin E1 (PGE1) on the stability of atherosclerotic plaque. A vulnerable plaque model was established in rabbits, using balloon injury combined with a high-cholesterol diet. The rabbits were distributed into a control group, a low-dose PGE1 treatment group, a moderate-dose PGE1 treatment group, a high-dose PGE1 treatment group, and a simvastatin treatment group, with treatments lasting for 4?weeks. At week 13 (at the end of the experiments), atherosclerotic plaque was triggered by injection of Russell's viper venom (Chinese) and histamine. Serological, pathological, immunohistochemical, and gene-expression studies were subsequently performed. PGE1 treatment did not alter serum lipid levels; however, PGE1 dose-dependently increased the thickness of the fibrous caps, and decreased the plaque vulnerability index. The plaque contents of macrophage- and the mRNA levels of monocyte-chemotactic protein-1, matrix metalloproteinase-1, and matrix metalloproteinase-9 were markedly reduced in all of the PGE1 treatment groups, with the high-dose of PGE1 being more effective than the simvastatin treatment. These findings suggest that PGE1 dose-dependently enhances the stability of atherosclerotic plaque. The high-dose of PGE1 presented more protection in terms of inhibiting macrophage accumulation and inflammatory expression in plaque. Our findings suggest a novel drug for the treatment of atherosclerosis.     

Angiotensin II-accelerated vulnerability of carotid plaque in a cholesterol-fed rabbit model-assessed with magnetic resonance imaging comparing to histopathology

This study sought to reveal the effect of angiotensin II (Ang II)-induced atherosclerotic vulnerability in rabbits and to determine whether in vivo magnetic resonance imaging (MRI) can determine the effect of Ang II on atherosclerotic development over time. In total, 24 elderly male New Zealand white rabbits underwent an intravascular balloon injury in the left common carotid artery (LCCA) and were subsequently fed a high cholesterol diet for 12 weeks. At 8 weeks, rabbits were randomly assigned to receive either Ang II (1.4 mg/kg/d, Ang II group) or vehicle (phosphate-buffered saline, control) via a subcutaneous osmotic minipump for 4 weeks. The rabbits were imaged three times: at baseline and at 8 and 12 weeks. After the 12-week MRI scanning, rabbits were euthanized to obtain pathological and histological data. Atherosclerotic plaques were identified in the 21 rabbits that survived the 12-week trial. Typical feature of vulnerable plaques (VP), intraplaque hemorrhage, were observed in 6 of 10 animals (60.0%) in the Ang II group. The Cohen K value of MR imaging between the AHA classifications was 0.82 (0.73–0.91; P < 0.001). MRI revealed that the change in carotid morphology were significantly different between the Ang II and control group plaques. Our results support an important role for Ang II in plaque vulnerability by promoting intraplaque neovascularization and hemorrhage as well as inflammation. The vulnerable features induced by Ang II in rabbit carotid plaques could be accurately monitored with MRI in vivo and confirmed with histomorphology.     

Biological Characteristics and Effect of Human Umbilical Cord Mesenchymal Stem Cells (hUC-MSCs) Grafting with Blood Plasma on Bone Regeneration in Rats

We evaluated the biological characteristics/effect of human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) grafting with blood plasma on bone regeneration in rat tibia nonunion. SD rats (142) were randomly divided into four groups: fracture group (positive control); nonunion group (negative control); hUC-MSCs grafting with blood plasma group; and hUC-MSCs grafting with saline group. Rats were administered tetracycline (30 mg/kg) and calcein blue (5 mg/kg) 8 days before killing. The animals were killed under deep anesthesia at 4 and 8 weeks post fracture for radiological evaluation and histological/immunohistological studies. The hUC-MSCs grafting with blood plasma group was similar to fracture group: the fracture line blurred in 4 weeks and disappeared in 8 weeks postoperatively. Histological/immunohistological studies showed that hUC-MSCs were of low immunogenicity which merged in rat bone tissue, differentiated into osteogenic lineages, and completed the healing of nonunion. After stem cell transplantation, regardless of whether plasma or saline was used, new multi-center bone formation was observed; fracture site density was better in stem cell grafting with blood plasma group. We, therefore, concluded that the biological characteristics of hUC-MSCs-treated nonunion were different from the standard fracture healing process, and the proliferative and localization capacity of hUC-MSCs might benefit from the use of blood plasma.     

Anterior Cruciate Ligament Reconstruction in a Rabbit Model Using Silk-Collagen Scaffold and Comparison with Autograft

The objective of the present study was to perform an in vivo assessment of a novel silk-collagen scaffold for anterior cruciate ligament (ACL) reconstruction. First, a silk-collagen scaffold was fabricated by combining sericin-extracted knitted silk fibroin mesh and type I collagen to mimic the components of the ligament. Scaffolds were electron-beam sterilized and rolled up to replace the ACL in 20 rabbits in the scaffold group, and autologous semitendinosus tendons were used to reconstruct the ACL in the autograft control group. At 4 and 16 weeks after surgery, grafts were retrieved and analyzed for neoligament regeneration and tendon-bone healing. To evaluate neoligament regeneration, H&E and immunohistochemical staining was performed, and to assess tendon-bone healing, micro-CT, biomechanical test, H&E and Russell-Movat pentachrome staining were performed. Cell infiltration increased over time in the scaffold group, and abundant fibroblast-like cells were found in the core of the scaffold graft at 16 weeks postoperatively. Tenascin-C was strongly positive in newly regenerated tissue at 4 and 16 weeks postoperatively in the scaffold group, similar to observations in the autograft group. Compared with the autograft group, tendon-bone healing was better in the scaffold group with trabecular bone growth into the scaffold. The results indicate that the silk-collagen scaffold has considerable potential for clinical application.