BACKGROUND: To investigate the effect of complete rupture of the posterior cruciate ligament (PCL) on the biomechanics and histology of the medial collateral ligament (MCL).
METHODS: Seventy-two male rabbits were randomly divided into two groups: the ruptured group was treated with complete PCL amputation, while the intact group was only subjected to PCL exposure without amputation. Eighteen rabbits were randomly sacrificed at 8, 16, 24, and 40 weeks after the operation, and their specimens were processed for mechanical tensile testing, nano-indentation experiments, hematoxylin-eosin (HE) staining, and picrosirius-polarization staining.
RESULTS: There was no significant difference in the length and maximum displacement of the MCL between the ruptured group and the intact group at each time point. The maximum load of the ruptured group was significantly smaller than that of the intact group at 40 W. The elastic modulus and micro-hardness of the ruptured group increased significantly at 24 W and decreased significantly at 40 W. At 16 W and 24 W after PCL rupture, the number of type I collagen fibers and type III collagen fibers in the MCL of the ruptured group was significantly increased compared with that of the intact group. While the type I collagen fibers of the ruptured group were significantly decreased compared with the intact group at 40 W, there was no significant difference in type III collagen fibers between the ruptured group and the intact group.
CONCLUSIONS: PCL rupture has no significant effect on the mechanical and histological properties of MCL in a short period of time under physiological loading, but the histological and mechanical properties of MCL decrease with time.

OBJECTIVE: To evaluate the correlation between the Mohawk (MKX) expression level and the collagen fiber diameter of autologous hamstring tendon graft during the stable graft remodeling phase after anterior cruciate ligament (ACL) reconstruction.
METHODS: Between January 2018 and August 2018, patients who underwent arth-roscopic single-bundle anatomical ACL reconstruction with autologous hamstring tendons for at least 48 months and also underwent second-look arthroscopy were enrolled in study. During the second-look arthroscopic procedures, ACL graft biopsies were performed from the surface of central part of the ligament. MKX expressions of ACL grafts were analysed by real-time fluorescent quantitative PCR (qRT-PCR). The ultrastructure of collagen fibers of grafts were evaluated by transmission electron microscopy, which included average diameter of collagen fibers (D c), average diameter of large-diameter collagen fibers (D L), average diameter of small-diameter collagen fibers (D S), and large-small collagen fibers ratio (R L/S). The correlation between MKX expression level and graft collagen fiber diameter was calculated.
RESULTS: Twenty-six patients met the selection criteria and their ACL graft specimens were enrolled in the study. The interval between ACL reconstruction and second-look arthroscopy was 52-128 months, with an average of 78.6 months. Arthroscopic graft remodeling score was 3-6 (mean, 4.8). There were 17 cases of excellent remodeling and 9 cases of fair remodeling. All ACL grafts showed typical bimodal distributions of both large-diameter collagen fibers and small-diameter collagen fibers, but the ultrastructural characteristics of the graft collagen fibers were different according to different remodeling status under arthroscopy. The D C, D L, D S, and R L/S of the graft specimens were (65.2±9.3) nm, (91.6±10.5) nm, (45.7±8.6) nm, and 0.73±0.12, respectively. The relative expression level of MKX was 1.42±0.11, which was positively linearly correlated with D C, D L, and R L/S, and the correlation coefficient was statistically significant ( r=0.809, P=0.000; r=0.861, P=0.000; r=0.942, P=0.000), while there was no significant correlation between D S and relative expression level of MKX ( r=0.147, P=0.238). Regression analysis showed that the relative expression level of MKX could predict the D C, D L, and R L/S results of the ACL graft specimens ( P<0.05).
CONCLUSIONS: After autologous hamstring tendon grafts stepped into stabilized remodeling phase, MKX expression level could predict the diameter measurement results of collagen fibers and be used as an important evaluation basis for graft collagen anabolic metabolism.
UNASSIGNED: 探讨在自体腘绳肌腱移植重建前交叉韧带（anterior cruciate ligament，ACL）术后的移植物塑形稳定阶段，移植物 Mohawk（MKX）表达水平与胶原纤维直径的相关性。.
UNASSIGNED: 以 2018 年 1 月—8 月关节镜下自体腘绳肌腱单束重建 ACL 术后 48 个月以上、因移除胫骨端内固定物行二次关节镜探查患者的移植物为研究对象。术中对移植物塑形评分；取移植物中央表面标本，采用实时荧光定量 PCR（real-time fluorescent quantitative PCR，qRT-PCR）检测 ACL 移植物 MKX 表达水平；透射电镜下观察移植物胶原纤维超微结构，测量胶原纤维直径（D c）、大直径（≥90 nm）胶原纤维直径（D L）、小直径（<90 nm）胶原纤维直径（D S）以及大、小直径胶原纤维数量比值（R L/S）。计算 MKX 表达水平与胶原纤维直径的相关性。.
UNASSIGNED: 共 26 例患者符合选择标准，其 ACL 移植物标本纳入研究。ACL 重建术至二次关节镜探查时间为 52～128 个月，平均 78.6 个月。关节镜下移植物质量评分为 3～6 分，平均 4.8 分；塑形良好 17 例、塑形一般 9 例。透射电镜观察，ACL 移植物均表现为大直径与小直径胶原纤维双峰混合排列，与正常 ACL 类似。与塑形一般的移植物相比，塑形良好的移植物可见更丰富的大直径胶原纤维，且大、小直径胶原纤维间隔交叉分布更均匀、有序。移植物 D c、D L、D S 及 R L/S 分别为（65.2±9.3）nm、（91.6±10.5）nm、（45.7±8.6）nm、0.73±0.12。移植物 MKX 相对表达量为 1.42±0.11。相关分析显示，移植物 MKX 表达水平与 D c、D L 及 R L/S 成正相关（ r=0.809， P=0.000； r=0.861， P=0.000； r=0.942， P=0.000），与 D S 无相关（ r=0.147， P=0.238）。进一步回归分析示，MKX 表达水平可以预测移植物 D c、D L、R L/S（ P<0.05）。.
UNASSIGNED: 采用自体腘绳肌腱重建 ACL 移植物达塑形稳定后，MKX 表达水平可预测电镜下胶原纤维直径测量结果，提示其可作为移植物胶原合成代谢水平的重要评估依据。.

The mechanical properties of the aorta tissue is not only important for maintaining the cardiovascular health, but also is closely related to the development of cardiovascular diseases. There are obvious differences between the ventral and dorsal tissues of the descending aorta. However, the cause of the difference is still unclear. In this study, a biaxial tensile approach was used to determine the parameters of porcine descending aorta by analyzing the stress-strain curves. The strain energy functions Gasser-Ogden-Holzapfel was adopted to characterize the orthotropic parameters of mechanical properties. Elastic Van Gieson (EVG) and Sirius red stain were used to observe the microarchitecture of elastic and collagen fibers, respectively. Our results showed that the tissue of descending aorta had more orthotropic and higher elastic modulus in the dorsal region compared to the ventral region in the circumferential direction. No significant difference was found in hyperelastic constitutive parameters between the dorsal and ventral regions, but the angle of collagen fiber was smaller than 0.785 rad (45°) in both dorsal and ventral regions. The arrangement of fiber was inclined to be circumferential. EVG and Sirius red stain showed that in outer-middle membrane of the descending aorta, the density of elastic fibrous layer of the ventral region was higher than that of the dorsal region; the amount of collagen fibers in dorsal region was more than that of the ventral region. The results suggested that the difference of mechanical properties between the dorsal and ventral tissues in the descending aorta was related to the microstructure of the outer membrane of the aorta. In the relatively small strain range, the difference in mechanical properties between the ventral and dorsal tissues of the descending aorta can be ignored; when the strain is higher, it needs to be treated differently. The results of this study provide data for the etiology of arterial disease (such as arterial dissection) and the design of artificial blood vessel.
动脉组织的力学性能对于维持心血管健康具有重要意义，并与心血管相关疾病的发生发展密切相关。主动脉腹侧和背侧组织力学性能之间存在显著差异，但缺乏量化的力学性能参数，且其成因尚不清楚。本文以猪降主动脉腹侧与背侧组织为研究对象，通过双轴拉伸方法获取应力-应变曲线，分析组织正交各向异性，采用 Gasser-Ogden-Holzapfel 型应变能函数描述动脉组织力学性能参数，采用 Elastic Van Gieson（EVG）法和天狼星红染色法观测动脉组织弹性纤维和胶原纤维显微结构。结果表明，与降主动脉腹侧组织相比，降主动脉背侧组织表现出更明显的正交各向异性，且在周向上的弹性模量明显大于降主动脉腹侧组织。降主动脉腹侧和背侧组织的超弹本构参数之间差异均无统计学意义，但几乎所有降主动脉组织的纤维角度都小于 0.785 rad（45°），胶原纤维的排列更趋于周向。EVG 和天狼星红染色显示降主动脉腹侧外-中膜弹性纤维层密度明显高于背侧组织，外-中膜胶原纤维背侧多于腹侧。结果提示，猪降主动脉背侧组织与腹侧组织之间的力学性能差异与外-中膜组织中的微观结构有关。在相对较小的应变范围内，可忽略降主动脉腹侧与背侧组织力学性能的差异；当应变较高时，则需区别对待。本研究结果可为动脉疾病（如动脉夹层）的成因以及人工血管设计等提供数据参考。.

OBJECTIVE: We aimed to compare the well-established liver fibrosis (LF) markers in Japanese patients with chronic hepatitis B (CHB, n = 331) and chronic hepatitis C (CHC, n = 886) and to discuss possible causes of differences in results between CHB patients and CHC patients.
METHODS: Virtual touch quantification (VTQ) in acoustic radiation force impulse, Fibrosis-4 (Fib-4) index, aspartate aminotransferase to platelet ratio index (APRI), and hyaluronic acid (HA) were compared between the two cohorts. As an additional investigation, total collagen proportional area (TCPA, %) was tested using liver pathological samples (n = 83).
RESULTS: Significant LF (F2 or greater) and advanced LF (F3 or greater) were identified in 153 (46.2%) and 76 (23.0%) patients in the CHB cohort and 579 (65.3%) and 396 (44.7%) patients in the CHC cohort. The median VTQ, Fib-4 index, APRI, and HA values in the CHB cohort were 1.20 m/s, 1.36, 0.44, and 25 ng/mL; those in the CHC cohort were 1.32 m/s, 2.60, 0.74, and 65.5 ng/mL (P-values, all <0.0001). Similar tendencies were noted by F stage-based stratification. The median TCPA in the CHB cohort and the CHC cohort were 8.5% and 12.7% (P < 0.0006). The TCPA values in the CHC cohort were higher than those in the CHB cohort regardless of LF stage.
CONCLUSIONS: Values of LF markers in CHB patients can differ from those in CHC patients even in the same LF stage. Difference in total amount of collagen fiber in CHB and CHC appears to be linked to the difference.

BACKGROUND: Conventional anti-microbial therapy largely consisted of systemic administration of various drugs effective against periodontal pathogens, but fraught with several problems. Based on the concept of local drug delivery a bioresorbable device made of pure fibrillar collagen has been developed. The aim of this study was to study the release of Tetracycline from this collagen fiber (Type I collagen) impregnated with Tetracycline and its antibacterial activity against Porphyromonas gingivalis.
METHODS: Porphyromonas gingivalis was isolated from plaque samples of chronic periodontitis patients by using a CO2 incubator. DNA isolation was done followed by polymerase chain reaction (PCR) amplification to confirm the presence of bacteria. The release pattern of Tetracycline was assessed for a period of 10 days in water (group I) and Serum inoculated with Porphyromonas gingivalis (group II).
RESULTS: A significant presence of Tetracycline on all days in Group I and group II and the zone of inhibition was also present in both groups with a steady decline from day 1 to day 10.
CONCLUSIONS: Since the results were well within the therapeutic concentration of drug required to inhibit the growth of gram -ve bacteria (Porphyromonas gingivalis), this bioresorbable Tetracycline fiber has the potential for clinical application.