The novel epiligament theory: differences in healing failure between the medial collateral and anterior cruciate ligaments

Study on the mechanism of quercetin inducing mesenchymal stem cells to differentiate into fibroblasts through TGF-β1 and IGF-1

BACKGROUND

Stem cell differentiation has opened up new avenues for disease treatment, tissue repair, and drug development in the study of regenerative medicine, and has huge application prospects. This study aimed to explore the mechanism of quercetin on the differentiation of mesenchymal stem cells (MSCs) into fibroblasts.

METHODS

In this study, cell differentiation experiments and flow cytometry were used to detect the successful isolation of bone marrow MSCs from SD rats. Quercetin at 5, 10, and 20 μM was used as low, medium, and high doses to intervene in MSCs. The cell viability changes of ligament fibroblasts at 24, 48, and 72 hours after quercetin treatment were detected using a CCK-8 cell counting kit. Cell proliferative capacity was determined by flow cytometry. RT-qPCR measured the relative expression levels of TGF-β1, IGF-1, COL-Ⅰ, COL-Ⅲ, FN (fibronectin), and TNMD (Tenomodulin) in different experimental groups. Molecular docking experiments were conducted to explore the binding effect of quercetin on TGF-β1 and IGF-1 proteins.

RESULTS

Flow cytometry verified the successful isolation of MSCs, which had high expression of CD29 and CD73, while lower expression of CD90 and CD45. Experimental results show that low and medium doses of quercetin can enhance cell proliferation, while high doses have no significant effect on cells. Detection of cell proliferation through flow cytometry yielded similar results to CCK-8. Transwell experiments have shown that low and medium doses of quercetin can increase cell migration ability. In addition, RT-qPCR detection showed that quercetin can increase the mRNA expression of TGF-β1 and IGF-1, and promote the expression of COL-Ⅰ, COL-Ⅲ, FN, and TNMD genes in ligament fibroblasts. Molecular docking results showed that quercetin can bind firmly to TGF-β1 and IGF-1.

CONCLUSION

Overall, this study revealed the morphological characteristics and identification of MSCs, as well as the regulatory mechanism of quercetin on the behavior of ligament fibroblasts. Quercetin affects the proliferation and gene expression of ligament fibroblasts by regulating the expression of TGF-β1 and IGF-1, which may provide a new perspective for biomedical research on the skeletal system.

Do the Differences in the Epiligament of the Proximal and Distal Parts of the Anterior Cruciate Ligament Explain Their Different Healing Capacities? Quantitative and Immunohistochemical Analysis of CD34 and α-SMA Expression in Relation to the Epiligament Theory

The aim of this study was to assess the epiligament theory by determining the normal epiligament morphology of the proximal and distal parts of the anterior cruciate ligament in humans and analyzing the differences between them and the midportion of the ligament in terms of cell numbers and expression of CD34 and α-SMA. Samples were obtained from the anterior cruciate ligaments of 12 fresh knee joints. Monoclonal antibodies against CD34 and α-SMA were used for immunohistochemistry. Photomicrographs were analyzed using ImageJ software, version 1.53f. The cell density was higher in the epiligament than in the ligament connective tissue. Cell counts were higher in the proximal and distal thirds than in the midsubstance of the epiligament. CD34 was expressed similarly in the proximal and distal thirds, although it seemed slightly more pronounced in the distal third. α-SMA expression was more robust in the proximal than the distal part. The results revealed that CD34 and α-SMA are expressed in the human epiligament. The differences between the numbers of cells in the proximal and distal parts of the epiligament and the expression of CD34 and α-SMA enhance epiligament theory. Future investigations into improving the quality of ligament healing should not overlook the epiligament theory.

New insight into the morphological characteristics of patella cubiti

Accessory bones in the elbow region are rare anatomical variations with important clinical significance as they can be misdiagnosed as pathological lesions. Usually, they are asymptomatic and found incidentally during X-ray examination in the context of trauma. Although these bones have been previously described, their development is not fully understood. The present case provides complex macroscopic, X-ray and histological descriptions of a sesamoid bone in the posterior region of the elbow-patella cubiti and the related surrounding structures. Moreover, this report indicates the presence of a well-defined syndesmosis between patella cubiti and the proximal ulna.

Anatomical Tissue Engineering of the Anterior Cruciate Ligament Entheses

The firm integration of anterior cruciate ligament (ACL) grafts into bones remains the most demanding challenge in ACL reconstruction, since graft loosening means graft failure. For a functional-tissue-engineered ACL substitute to be realized in future, robust bone attachment sites (entheses) have to be re-established. The latter comprise four tissue compartments (ligament, non-calcified and calcified fibrocartilage, separated by the tidemark, bone) forming a histological and biomechanical gradient at the attachment interface between the ACL and bone. The ACL enthesis is surrounded by the synovium and exposed to the intra-articular micromilieu. This review will picture and explain the peculiarities of these synovioentheseal complexes at the femoral and tibial attachment sites based on published data. Using this, emerging tissue engineering (TE) strategies addressing them will be discussed. Several material composites (e.g., polycaprolactone and silk fibroin) and manufacturing techniques (e.g., three-dimensional-/bio-printing, electrospinning, braiding and embroidering) have been applied to create zonal cell carriers (bi- or triphasic scaffolds) mimicking the ACL enthesis tissue gradients with appropriate topological parameters for zones. Functionalized or bioactive materials (e.g., collagen, tricalcium phosphate, hydroxyapatite and bioactive glass (BG)) or growth factors (e.g., bone morphogenetic proteins [BMP]-2) have been integrated to achieve the zone-dependent differentiation of precursor cells. However, the ACL entheses comprise individual (loading history) asymmetric and polar histoarchitectures. They result from the unique biomechanical microenvironment of overlapping tensile, compressive and shear forces involved in enthesis formation, maturation and maintenance. This review should provide a road map of key parameters to be considered in future in ACL interface TE approaches.

[Diagnosis and treatment progress in the femoral insertion injury of medial collateral ligament of knee]

Objective

To summarize the diagnosis and treatment progress in the femoral insertion injury of the medial collateral ligament (MCL) of knee, and to provide a clinical reference for diagnosis and treatment.

Methods

The literature on the femoral insertion injury of the MCL of knee was widely reviewed. The incidence, mechanisms of injury and anatomy, the diagnosis and classification, and status of treatment were summarized.

Results

The mechanism of the femoral insertion injury of the MCL of knee is related to its anatomical and histological characteristics, as well as the abnormal valgus of the knee joint, excessive external rotation of the tibial platform and it is classified according to the injury characteristics to guide the refined and individualized clinical treatment.

Conclusion

Due to different understanding of femoral insertion injury of MCL of knee, the treatment methods are different, and thus is the healing effect. Additional studies are still needed to promote the healing of insertion injuries.

ACL repair for athletes?

Background

The current gold standard treatment for an anterior cruciate ligament (ACL) tear in an athlete is an arthroscopic ACL reconstruction with autografts. This restores the knee stability but is associated with unique complications like graft re-tear, kinesiophobia and graft donor site morbidity. ACL suture repair (ACLSR) is an attractive alternative method of surgical management of this injury.

Current science of ACLSR

The potential advantages of performing a repair are the preservation of native biology and proprioceptive function of ACL, elimination of a graft and preservation of bone stock. The purported benefits are better stability, reduction of kinesiophobia and faster rehabilitation. ACLSR is now performed only for proximal (femoral-sided) tears in the acute phase, when the tissue quality is good and using high-strength nonabsorbable sutures. There are several techniques for performing ACLSR but broadly speaking are either non-augmented, static augmented with suture tape, dynamic augmented or using bio-scaffolds.

Clinical outcome of ACLSR

There is a lot of literature on ACLSRs including case series, cohort studies and randomized controlled trials. The results from these studies are encouraging but mostly pertain to patient reported outcome measures, are in small numbers and in the short-term. The results are also inconsistent across different studies and not specifically performed for the athletic population. Moreover, most of these studies are from the innovator or designer surgeons and groups and have not been independently validated.

Conclusion

Currently, there is insufficient evidence to recommend ACLSR as a preferred method of managing even acute proximal tears in athletes. Improved rates of return to sports, lower retear rate and lesser kinesiophobia needs to be proven in athletes.