In vitro method to quantify and visualize mechanical wear in human meniscus subjected to joint loading

The mechanical wear and tear of soft connective tissue from repetitive joint loading is a primary factor in degenerative joint disease, and therefore methods are needed to accurately characterize wear in joint structures. Here, we evaluate the accuracy of using a structured light 3D optical scanning system and modeling software to quantify and visualize volume loss in whole human meniscus subjected to in vitro joint loading. Using 3D printed meniscus replicas with known wear volumes, we determined that this novel imaging method has a mean accuracy of approximately 13 mm3, corresponding to a mean error of less than 7% when measuring meniscal volumetric changes of 0.2 cm3 (size of a pea). The imaging method was then applied to measure the in vitro wear of whole human menisci at four time points when a single cadaveric knee was subjected to one million cycles of controlled joint loading. The medial and lateral menisci reached steady state volumetric reductions of 0.72 cm3 and 0.34 cm3 per million cycles, respectively. Colorimetric maps of linear wear depth revealed high wear and deformation in the posterior regions of both the medial and lateral menisci. For the first time, this study has developed a method to accurately characterize volume loss in whole meniscus subjected to in vitro joint loading. This 3D scanning method offers researchers a new investigative tool to study mechanical wear and joint degeneration in meniscus, and other soft connective tissues.

MRI study of medial meniscus degeneration of osteoarthritic knees with or without posterior root tear

Purpose

The purpose of this study was to compare the medial meniscus (MM) degeneration, meniscus extrusion, and tibial joint inclination by using MRI to consider the pathogenesis of posterior root tear (PRT) in medial-type knee osteoarthritis (KOA) both with and without medial meniscus posterior root tear (MMPRT).

Methods

This study used open MRI with flexion sagittal view and included 324 medial-type osteoarthritic knees with a Kellegren–Lawrence grade of 2 or less. Following the exclusion process, 151 knees were selected for MRI analysis. MM degeneration grading was performed according to Jerosch by 5 degrees of 0–4 in four different portions from anterior to posterior. MM medial extrusion (MMME), MM posterior extrusion (MMPE), medial tibial medial slope (MTMS), and medial tibial posterior slope (MTPS) were measured according to previous studies.

Results

MM degeneration in the anterior portion to MCL averaged 1.72 ± 0.67 in the PRT group (n = 48) and 1.40 ± 0.78 in the non-PRT group (n = 103). The degeneration grade was statistically higher in the PRT group than in the non-PRT group (p = 0.050). There was no difference in MM degeneration in the other three portions. MMME averaged 4.02 ± 1.12 mm in the PRT group and 3.11 ± 1.11 mm in the non-PRT group. MMPE averaged 4.22 ± 0.87 mm in the PRT group and 2.83 ± 1.12 mm in the non-PRT group. Both MMME and MMPE in the PRT group were statistically larger than those in the non-PRT group (p < 0.001). There was no difference in MTMS between the two groups. MTPS averaged 6.34 ± 2.25° in the PRT group and 5.28 ± 2.23° in the non-PRT group. The MTPS of the PRT group was statistically larger than that of the non-PRT group (p = 0.007).

Conclusion

The severity of MM degeneration, extrusion of MM, and degree of tibial slope were compared between medial-type KOA with and without PRT using an open MRI. MM degeneration was more severe anteriorly in the PRT group. The PRT group showed larger MMME and MMPE with greater MTPS.

Level of evidence

III. Retrospective cohort study.

Identification and validation of pivotal genes related to age-related meniscus degeneration based on gene expression profiling analysis and in vivo and in vitro models detection

BACKGROUND

The componential and structural change in the meniscus with aging would increase the tissue vulnerability of the meniscus, which would induce meniscus tearing. Here, we investigated the molecular mechanism of age-related meniscus degeneration with gene expression profiling analysis, and validate pivotal genes in vivo and in vitro models.

METHODS

The GSE45233 dataset, including 6 elderly meniscus samples and 6 younger meniscus samples, was downloaded from the Gene Expression Omnibus (GEO) database. To screen the differential expression of mRNAs and identify the miRNAs targeting hub genes, we completed a series of bioinformatics analyses, including functional and pathway enrichment, protein-protein interaction network, hub genes screening, and construction of a lncRNA-miRNA-mRNA network. Furthermore, crucial genes were examined in human senescent menisci, mouse senescent meniscus tissues and mouse meniscus cells stimulated by IL-1β.

RESULTS

In total, the most significant 4 hub genes (RRM2, AURKB, CDK1, and TIMP1) and 5 miRNAs (hsa-miR-6810-5p, hsa-miR-4676-5p, hsa-miR-6877-5p, hsa-miR-8085, and hsa-miR-6133) that regulated such 4 hub genes, were finally identified. Moreover, these hub genes were decreased in meniscus cells in vitro and meniscus tissues in vivo, which indicated that hub genes were related to meniscus senescence and could serve as potential biomarkers for age-related meniscus tearing.

CONCLUSIONS

In short, the integrated analysis of gene expression profile, co-expression network, and models detection identified pivotal genes, which elucidated the possible molecular basis underlying the senescence meniscus and also provided prognosis clues for early-onset age-related meniscus tearing.

Degeneration alters the biomechanical properties and structural composition of lateral human menisci

OBJECTIVE

Because the literature relating to the influence of degeneration on the viscoelasticity and tissue composition of human lateral menisci remains contradictory or completely lacking, the aim of this study was to fill these gaps by comprehensively characterising the biomechanical properties of menisci with regard to the degree of degeneration.

DESIGN

Meniscal tissue from 24 patients undergoing a total knee replacement was collected and the degeneration of each region classified according to Pauli et al. For biomechanical characterisation, compression and tensile tests were performed. Additionally, the water content was determined and infrared (IR) spectroscopy was applied to detect changes in the structural composition, particularly of the proteoglycan and collagen content.

RESULTS

With an increasing degree of degeneration, a significant decrease of the equilibrium modulus was detected, while simultaneously the water content and the hydraulic permeability significantly increased. However, the tensile modulus displayed a tendency to decrease with increasing degeneration, which might be due to the significantly decreasing amount of collagen content identified by the IR measurements.

CONCLUSION

The findings of the current study may contribute to the understanding of meniscus degeneration, showing that degenerative processes appear to mainly worsen viscoelastic properties of the inner circumference by disrupting the collagen integrity.

The underlying mechanism of partial anterior cruciate ligament injuries to the meniscus degeneration of knee joint in rabbit models

Background

The diagnosis, treatment, and efficacy evaluation of anterior cruciate ligament (ACL) partial rupture remains controversial. This research aims to investigate the underlying mechanism of partial ACL injuries to the meniscus degeneration in the rabbit knee.

Methods

Sixty New Zealand white rabbits were randomly divided into three groups including an experimental group, a sham group (n = 6), and a blank control group (n = 6). The experimental group is composed of an anteromedial bundle (AMB) rupture group (n = 24) and a posterolateral bundle (PLB) rupture group (n = 24). Rabbits in the experimental group were subjected to right hind limbs knee surgery to induce ACL part injury under the arthroscopy. Finally, eight rabbits including 6 in the model group and 2 in the control group were sampled randomly on the 2nd, 4th, and 8th weeks respectively. We observed the typical form of the meniscus through HE staining. Expressions of inflammatory factors including interleukin-1β (IL-1β) and IL-17 in the knee joint fluid were determined by means of an ELISA. Analysis of the mRNA expressions of matrix metalloproteinases-13(MMP-13) was performed to evaluate the inflammatory mediators in the pathogenesis of the meniscus.

Results

HE staining results showed that the surface was rough and the tissues were loose displaying collagen fibers of varying thickness. Both IL-1β and IL-17 in the synovial fluid and the positive rate of MMP-13 in addition to MMP-13 mRNA showed a demonstrable increase treads from the 2nd to the 8th week. The significant difference was found (P < 0.05) compared to the control group.

Conclusion

We conclude that the elevated levels of IL-1β and IL-17, along with increased MMP13 expression, resulted in meniscus degradation in the rabbit knee joint model with partial ACL injury.

Early degeneration of the meniscus revealed by microbiomechanical alteration in a rabbit anterior cruciate ligament transection model

Background

The microbiomechanical properties of the meniscus influence the cell response to the surrounding biomechanical environment ​and are beneficial to understand meniscus repairing and healing. To date, however, this information remains ambiguous. This study aims to characterise the microbiomechanical properties of the meniscus after degeneration in a rabbit anterior cruciate ligament transection (ACLT) model and to analyse the corresponding histology at the macroscale and chemical composition.

Methods

Twenty New Zealand white rabbits were used. Menisci were collected from the knee joints 4 and 8 weeks after the ACLT and from those of the corresponding control groups. The central portions of both medial and lateral menisci were investigated using atomic force microscopy, histological study, and an energy-dispersive spectrometer. The evaluation was conducted regionally within the inner, middle, and outer sites from the top layer (facing the femoral surface) to the bottom layer (facing the tibial surface) in both the lateral and medial menisci to obtain the site-dependent properties.

Results

At 4 weeks after surgery, the dynamic elastic modulus at the microlevel increased significantly at both the top and bottom layers compared with the intact meniscus (P ​= ​0.021). At 8 weeks after surgery, the stiffening occurred in all regions (P ​= ​0.030). The medial meniscus showed greater change than the lateral meniscus. All these microbiomechanical alterations occurred before the histological findings at the macroscale.

Conclusion

The microbiomechanical properties in the meniscus changed significantly after ACLT and were site dependent. Their alterations occurred before the histological changes of degeneration were observed.

The Translational Potential of this Article

The results of our study indicated that degeneration promoted meniscus stiffening. Thus, they provide a better understanding of the disease process affecting the meniscus. Our results might be beneficial to understand how mechanical forces distribute throughout the healthy and pathologic joint. They indicate the possibility of early diagnosis using a minimally invasive arthroscopic tool, as well as they might guide treatment to the healthy and pathologic meniscus and joint.

Substantive molecular and histological changes within the meniscus with tears

BACKGROUND

The meniscus plays a vital role in the normal biomechanics of the knee. However, it is not well studied at the molecular level. The purpose of this study was to determine whether molecular and pathological changes in the meniscal tissue vary depending on the presence or absence of meniscal and/or anterior cruciate ligament tear (ACL).

METHODS

Six normal menisci (group A), seven simple torn menisci (group B) and seven torn menisci with concomitant anterior cruciate ligament tears (group C) were collected. We observed the pathological changes in the menisci and used real-time polymerase chain reaction along with immunohistochemistry and in situ hybridisation to examine the levels of ACAN, ADAMTS5, COL10A1, CEBPβ, MMP13 and miR-381-3p, miR-455-3p, miR-193b-3p, miR-92a-3p, respectively. Patients were scored preoperatively and postoperatively using the Lysholm Knee Scoring Scale and International Knee Documentation Committee Subjective Knee Evaluation Form.

RESULTS

Compared with group A, the expression levels of ADAMTS5, COL10A1, CEBPβ, and MMP13 and all the miRNAs were increased while ACAN was down-regulated in groups B and C. Additionally, the gene expression and miRNA levels were higher in group C than that in group B, except for ACAN, which was lower. Several fibrochondrocytes strongly expressed ADAMTS5, CEBPβ, and MMP13 in groups B and C and had high levels of miR-381-3p and miR-455-3p than that in group A. Postoperative Lysholm and IKDC scores were higher in group B than in group C.

CONCLUSIONS

Our findings suggest that the meniscus tended to degenerate after it was injured, especially when combined with a torn ACL. The miRNAs investigated in this study might also contribute to meniscus degeneration. Patients with a combined injury patterns might have relatively worse joint function.

The medial open-wegde osteotomy generates progressive intrameniscal integrity changes in the lateral knee compartment: a prospective MR-assessment after valgic osteotomy in the varus gonarthritic knee

PURPOSE

Meniscal changes in the lateral knee compartment after medial-opening high tibial osteotomy (HTO) with valgic overcorrection have not been investigated clinically with magnetic resonance imaging (MRI). The hypothesis of this study was that HTO with valgic overcorrection affects the lateral compartment due to the change in the bearing axis and the shift in the pressure load from the medial to the lateral compartment. This should lead to an accelerated degeneration of the lateral compartment.

METHODS

Twenty-four patients (mean age, 45.7 ± 7.6 years) were prospectively and longitudinally monitored with MRI after medial-opening high tibial osteotomy. The degeneration of the meniscus was assessed at the anterior horn, pars intermedia, and posterior horn using the Stoller classification. The morphological changes were also assessed at the anterior horn, pars intermedia, and posterior horn using the relative vertical and transverse diameters of the examined part of the meniscus, according to the ratio maximal meniscal diameter/maximal tibial width. These parameters were analyzed preoperatively and at follow-up (mean 5.3 ± 1.5 years after surgery).

RESULTS

During the follow-up period, there were no significant morphological changes in either the anterior horn, pars intermedia, or posterior horn. Nor were there any correlations between the morphological parameters, bodyweight, and the follow-up period. Despite these findings, an MRI evaluation showed progressive degeneration in every part of the meniscus according to the Stoller classification, and this was significant at the anterior horn (p < 0.01), pars intermedia (p = 0.021), and posterior horn (p < 0.01).

CONCLUSION

High tibial osteotomy did not lead to morphological changes in the external meniscus over a follow-up period of 5.3 ± 1.5 years. However, progressive degeneration of the meniscus was observed in the imaging data. Further research is required to confirm the observed degeneration and to evaluate the consequences of the observed degeneration.