Up-regulation expressions of lysyl oxidase family in Anterior Cruciate Ligament and Medial Collateral Ligament fibroblasts induced by Transforming Growth Factor-Beta 1

RNA-seq reveals Lysyl oxidase as a potential biomarker of glomerular function in diabetic nephropathy in rats

PURPOSE

We downloaded the gene expression profiles of patients with diabetic nephropathyfrom the GEO database and combined it with differential gene analysis of rat transcriptome,our study employed animal models to examine the role of key hub genes in diabetic nephropathy and to pinpoint significant gene regulation in this disease.

METHODS

An examination of differential expression was performed using the online analysis tool GEO2R and the DN-related datasets GSE30528 and GSE1009 obtained from the GEO database. A comparison of gene expression between the normal and diabetic nephropathy groups was conducted using the RNA-seq technique. We further examined body weightchanges and detected the levels of blood glucose, 24-hour urine microalbumin, and expression ofIL-6 and TNF-α.We also measured the levels of Lysyl oxidase (LOX) using quantitative real-time PCR and western blotting.

RESULTS

We found that LOX was among the top 10 significantly differentially expressed genes in both the GEO database and transcriptome. Moreover, the levels of fasting blood glucose,24-h urine microalbumin, and expression of TNF-α and IL-6 were significantlyincreasedin the DNthanin the normal group (P < 0.05).

CONCLUSIONS

Our study demonstrates that the LOX gene is extensively expressed in diabetic nephropathy,with significantly upregulated expression and accompanying notable physiological markers such as TNF-α, IL-6, fasting blood glucose, and 24-hour urine microalbumin. The observed alterations indicate that the LOX gene has a potential biomarker function in the advancement of the disease.

TGF-β1 and Mechanical-Stretch Induction of Lysyl-Oxidase and Matrix-Metalloproteinase Expression in Synovial Fibroblasts Requires NF-κB Pathways

The imbalance in the expression of matrix metalloproteinases (MMPs) and lysyl oxidases (LOXs) in synovial fibroblasts (SFs) caused by mechanical injury and inflammatory response prevents injured anterior cruciate ligaments (ACLs) from self-healing. However, research on the effect of growth factors on SFs on regulating the microenvironment is limited. In this study, mechanical injury and exogenous transform growth factor-β1 (TGF-β1) were employed to mimic a joint-cavity microenvironment with ACL trauma. The function of the NF-κB transcription factor was further studied. The study found that the gene expression of LOXs (except LOXL-1), MMP-1, -2, and -3 in SFs was promoted by the combination of injurious mechanical stretching and TGF-β1 and that the upregulation of MMPs was higher than that of LOXs. In addition, MMP-2 activity induced by the combination of injurious stretch and TGF-β1 was inhibited by NF-κB inhibitors such as Bay11-7082 and Bay11-7085. The findings concluded that the synovium was an important regulator of the knee joint-cavity microenvironment after ACL injury and that the NF-κB pathway mediated the regulation of MMP-2 in SFs via mechanical factors and TGF-β1.

Effect of mechanical injury and IL-1β on the expression of LOXs and MMP-1, 2, 3 in PCL fibroblasts after co-culture with synoviocytes

BACKGROUND

Crosstalk between posterior cruciate ligament fibroblasts (PCLfs) and synoviocytes (SCs) significantly modifies the homeostatic balance of the extracellular matrix (ECM) and appears to post a prominent affection for wound healing of PCL. Interleukin-1β (IL-1β) is regarded as a critical factor in acute inflammatory events during ligament injury.

METHODS

In order to confirm the capability of SCs the response of lysyl oxidases (LOXs) and matrix metalloproteinases (MMPs) to IL-1β, the complex cues of the joint cavity following PCL injury were simulated and the effect of IL-1β on the expression of LOXs and MMPs in PCLfs were investigated. PCLfs in both the mono- and co-culture conditions were treated with IL-1β. Cell lysates were collected from the PCLfs and LOXs and MMP-1, 2, 3 expression quantified using quantitative real-time PCR and western bolting.

RESULTS

The results indicated that injury alone elevated the expression of LOXs and MMP-1, 2 and 3. But IL-1β significantly decreased the LOX, LOXL1, and LOXL3 expression, and simultaneously increased MMP-1, 2 and 3 expressions in injured PCLfs. Furthermore, co-culture further suppressed LOXs, but stimulated MMP-1, 2 and 3 expressions when subjected to both mechanical injury and IL-1β treatment. This possibly suggests that a number of soluble factors are secreted that act as mediators that amplify the response of SCs.

CONCLUSION

The results indicated that the SCs could affect the IL-1β-induction of LOXs inhibition and MMPs accumulation, which may be the underlying mechanism of the the poor healing response following PCL injury.

Role of the lysyl oxidase family in organ development (Review)

Lysyl oxidase proteins (LOXs) are amine oxidases, which are mainly located in smooth muscle cells and fibroblasts and serve an important role in the formation of the extracellular matrix (ECM) in a copper-dependent manner. Owing to the ability of LOX proteins to modulate crosslinking between collagens and to promote the deposition of other fibers, they serve crucially in organogenesis and the subsequent organ development, as well as disease initiation and progression. In addition, ECM formation significantly influences organ morphological formation in both cancer- and non-tumor-related diseases, in addition to cellular epigenetic transformation and migration, under the influence of LOXs. A number of different signaling pathways regulate the LOXs expression and their enzymatic activation. The tissue remodeling and transformation process shares some resemblance between oncogenesis and embryogenesis. Additionally the roles that LOXs serve appeared to be stressed during oncogenesis and tumor metastasis. It has also been indicated LOXs have a noteworthy role in non-tumor diseases. Nonetheless, the role of LOXs in systemic or local organ development and disease control remains unknown. In the present study, the essential roles that LOXs play in embryogenesis were unveiled partially, whereas the role of LOXs in organ or systematic development requires further investigations. The present review aimed to discuss the roles of members of the LOX family in the context of the remodeling of organogenesis and organ development. In addition, the consequences of the malfunction of these proteins related to the development of abnormalities and resulting diseases is discussed.

Downregulation of lysyl oxidase and lysyl oxidase-like protein 2 suppressed the migration and invasion of trophoblasts by activating the TGF-β/collagen pathway in preeclampsia

Preeclampsia is a pregnancy-specific disorder that is a major cause of maternal and fetal morbidity and mortality with a prevalence of 6–8% of pregnancies. Although impaired trophoblast invasion in early pregnancy is known to be closely associated with preeclampsia, the underlying mechanisms remain elusive. Here we revealed that lysyl oxidase (LOX) and LOX-like protein 2 (LOXL2) play a critical role in preeclampsia. Our results demonstrated that LOX and LOXL2 expression decreased in preeclamptic placentas. Moreover, knockdown of LOX or LOXL2 suppressed trophoblast cell migration and invasion. Mechanistically, collagen production was induced in LOX- or LOXL2-downregulated trophoblast cells through activation of the TGF-β1/Smad3 pathway. Notably, inhibition of the TGF-β1/Smad3 pathway could rescue the defects caused by LOX or LOXL2 knockdown, thereby underlining the significance of the TGF-β1/Smad3 pathway downstream of LOX and LOXL2 in trophoblast cells. Additionally, induced collagen production and activated TGF-β1/Smad3 were observed in clinical samples from preeclamptic placentas. Collectively, our study suggests that the downregulation of LOX and LOXL2 leading to reduced trophoblast cell migration and invasion through activation of the TGF-β1/Smad3/collagen pathway is relevant to preeclampsia. Thus, we proposed that LOX, LOXL2, and the TGF-β1/Smad3/collagen pathway can serve as potential markers and targets for clinical diagnosis and therapy for preeclampsia.

Cancer-associated proteins play a role in preeclampsia, a potentially life-threatening disorder of pregnancy marked by high blood pressure and protein in the urine. The causes of preeclampsia are poorly understood, but the tissue that nourishes the fetus, the placenta, is known to be involved. Knowing that for healthy placenta formation, cells called trophoblasts must show cancer cell-like behavior and invade the developing tissue, Li-Ping Jin and Kai Wang at Tongji University School of Medicine in Shanghai, China, and co-workers investigated the role of cancer-associated LOX proteins, previously linked to cell invasiveness. Preeclamptic placentas showed low LOX levels, poor trophoblast invasion, and excessive formation of collagen, an important connective tissue. Further analysis showed that this excessive collagen is broken down, becoming the diagnostic urinary protein. These results illuminate potential markers for early diagnosis and treatment of preeclampsia.

Transforming growth factor-β1 up-regulates connexin43 expression in osteocytes via canonical Smad-dependent signaling pathway

Connexin 43 (Cx43)-mediated gap junctional intercellular communication (GJIC) has been shown to be important in regulating multiple functions of bone cells. Transforming growth factor-β1 (TGF-β1) exhibited controversial effects on the expression of Cx43 in different cell types. To date, the effect of TGF-β1 on the Cx43 expression of osteocytes is still unknown. In the present study, we detected the expression of TGF-β1 in osteocytes and bone tissue, and then used recombinant mouse TGF-β1 to elucidate its effect on gap junctions (GJs) of osteocytes. Our data indicated that TGF-β1 up-regulated both mRNA and protein expression of Cx43 in osteocytes. Together with down-regulation of Cx43 expression after being treated with TGF-β type I receptor inhibitor Repsox, we deduced that TGF-β1 can positively regulate Cx43 expression in osteocytes. Thus we next focussed on the downstream signals of TGF-β and found that TGF-β1-mediated smads, Smad3 and Smad4, to translocate into nucleus. These translocated signal proteins bind to the promoter of Gja1 which was responsible for the changed expression of Cx43. The present study provides evidence that TGF-β1 can enhance GJIC between osteocytes through up-regulating Cx43 expression and the underlying mechanism involved in the activation of Smad-dependent pathway.

Presence of meniscus tear alters gene expression profile of anterior cruciate ligament tears

Anterior cruciate ligament (ACL) tears occur in isolation or in tandem with other intra-articular injuries such as meniscus tears. The impact of injury pattern on the molecular biology of the injured ACL is unknown. Here, we tested the hypothesis that the biological response of the ACL to injury varies based on the presence or absence of concomitant meniscus tear. We performed RNA-seq on 28 ACL tears remnants (12 isolated, 16 combined). In total, 16,654 transcripts were differentially expressed between isolated and combined injury groups at false discovery rate of 0.05. Due to the large number of differentially expressed transcripts, we undertook an Ensembl approach to discover features that acted as hub genes that did not necessarily have large fold changes or high statistical significance, but instead had high biological significance. Our data revealed a negatively correlated module containing 5,960 transcripts (down-regulated in combined injury) and a positively correlated module containing 2,260 transcripts (up-regulated in combined injury). TNS1, MEF2D, NOTCH3, SOGA1, and MLXIP were highly-connected hub genes in the negatively correlated module and SCN2A, CSMD3, LRC44, USH2A, and LRP1B were critical hub genes in the positively correlated module. Transcripts in the negatively correlated module were associated with biological adhesion, actin-filament organization, cell junction assembly, and cell matrix adhesion. The positively correlated module transcripts were enriched for neuron migration and exocytosis regulation. These findings indicate genes and pathways reflective of healing deficiency and gain of neurogenic signaling in combined ACL and meniscus tears, suggesting their diminished repair potential. The biological response of ACL to injury could have implications for healing potential of the ligament and the long term health of the knee. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2612-2621, 2018.

LOX-catalyzed collagen stabilization is a proximal cause for intrinsic resistance to chemotherapy

The potential of altering the tumor ECM to improve drug response remains fairly unexplored. To identify targets for modification of the ECM aiming to improve drug response and overcome resistance, we analyzed expression data sets from pre-treatment patient cohorts. Cross-evaluation identified a subset of chemoresistant tumors characterized by increased expression of collagens and collagen-stabilizing enzymes. We demonstrate that strong collagen expression and stabilization sets off a vicious circle of self-propagating hypoxia, malignant signaling, and aberrant angiogenesis that can be broken by an appropriate auxiliary intervention: Interfering with collagen stabilization by inhibition of lysyl oxidases significantly enhanced response to chemotherapy in various tumor models, even in metastatic disease. Inhibition of collagen stabilization by itself can reduce or enhance tumor growth depending on the tumor type. The mechanistical basis for this behavior is the dependence of the individual tumor on nutritional supply on one hand and on high tissue stiffness for FAK signaling on the other.

Influence of cartilage interstitial fluid on gene expression in cruciate ligament fibroblasts

Loading of articular cartilage during motion squeezes the fluid from the cartilage, termed cartilage interstitial fluid (CIF), which was found to influence gene expression in synovial membrane cells. After crucial ligaments damage, these cells are exposed to synovial fluid containing factors released from articular cartilage; the aim of the present study was to establish the influence of CIF and factors present in CIF (CIF-like cocktails) on crucial ligament fibroblasts. CIF was squeezed from articular-epiphyseal cartilage complexes of newborn rats. Fibroblasts were obtained from crucial ligaments of adult rat knee joints. Cells were cultured in control medium, CIF and CIF-like cocktails, and the expression of selected genes was evaluated using quantitative PCR. CIF stimulated the expression of HAS1, HAS2, aggrecan, lubricin, MMP3, TIMP3 and TGFβ1. Expression of collagen type I, versican, MMP2, TIMP2, TNF and IL1β was inhibited. The CIF-like cocktail stimulated HAS1, HAS2, collagen type I, versican, aggrecan, lubricin, TIMP1, TGFβ1, IL1β, IL6 and inhibited of MMP3 and TNF expression. Both agents exerted similar effects on the expression of HAS2, aggrecan, lubricin, TGFβ1 and TNF. CIF contains inhibitory and stimulatory factors affecting gene expression in crucial ligament fibroblasts and some of them were not included in the CIF-like cocktail. Due to the powerful influence of CIF on crucial ligament fibroblasts and the synovial membrane, further studies on its composition are needed. An improved CIF like-cocktail could be applied in the treatment of various joint or tendon ailments.

Differentiation of Human Amniotic Mesenchymal Stem Cells into Human Anterior Cruciate Ligament Fibroblast Cells by In Vitro Coculture

Anterior cruciate ligament injuries are common in humans, though cellular components of the knee have little regenerative or proliferation potential. This study investigated the differentiation of human amnion-derived mesenchymal stem cells (hAMSCs) into human anterior cruciate ligament fibroblasts (hACLFs) in vitro through induction with bFGF and TGF-β1 with coculture systems. Groups A and B comprised hAMSCs at the 3rd passage cultured with and without bFGF and TGF-β1, respectively; Groups C and D consisted of hAMSCs and hACLFs in monolayer coculture with and without bFGF and TGF-β1, respectively; Groups E and F were composed of hAMSCs and hACLFs in Transwell coculture with and without bFGF and TGF-β1, respectively. Cell morphology and proliferation were recorded. Protein expression and relative mRNA expression were evaluated in each group. Cell proliferation was significantly higher in the induced groups than in the noninduced groups. Protein expression increased over time with the highest expression observed in Group E. mRNA levels were significantly higher in Group E than in other groups. This study is the first to demonstrate the use of the Transwell coculture system for this purpose, and hAMSCs were successfully differentiated into hACLFs. Thus, hAMSCs may be a superior choice for hACLF differentiation via Transwell coculture.

Evaluation of cultured human dermal- and dermo-epidermal substitutes focusing on extracellular matrix components: Comparison of protein and RNA analysis

Treatment of full-thickness skin defects with split-thickness skin grafts is generally associated with contraction and scar formation and cellular skin substitutes have been developed to improve skin regeneration. The evaluation of cultured skin substitutes is generally based on qualitative parameters focusing on histology. In this study we focused on quantitative evaluation to provide a template for comparison of human bio-engineered skin substitutes between clinical and/or research centers, and to supplement histological data. We focused on extracellular matrix proteins since these components play an important role in skin regeneration. As a model we analyzed the human dermal substitute denovoDerm and the dermo-epidermal skin substitute denovoSkin. The quantification of the extracellular matrix proteins type III collagen and laminin 5 in tissue homogenates using western blotting analysis and ELISA was not successful. The same was true for assaying lysyl oxidase, an enzyme involved in crosslinking of matrix molecules. As an alternative, gene expression levels were measured using qPCR. Various RNA isolation procedures were probed. The gene expression profile for specific dermal and epidermal genes could be measured reliably and reproducibly. Differences caused by changes in the cell culture conditions could easily be detected. The number of cells in the skin substitutes was measured using the PicoGreen dsDNA assay, which was found highly quantitative and reproducible. The (dis) advantages of assays used for quantitative evaluation of skin substitutes are discussed.

[Gene expression of down-regulation of lysyl oxidases family in keratoconus corneal fibroblasts induced by combination of mechanical stretching and prostaglandin E 2]

In order to investigate the effects of mechanical stretching combined with prostaglandin E 2 (PGE 2) on the gene expression of lysyl oxidases (LOXs) in keratoconus, we treated cultured corneal fibroblasts from healthy human cornea and keratoconus patient cornea with PGE 2 and/or cyclic stretch (12% elongation, 0.1 Hz, 12 h). Real-time fluorescent quantitative polymerase chain reaction was used to detect the gene expression of LOXs. The results showed that the gene expression of LOXs in keratoconus group was significantly lower than that in the healthy one. Compared to the static control group, 12% stretching alone up-regulated gene expression of LOXL-2, LOXL-4 in the healthy group, whereas it down-regulated LOXL-3, LOXL-4 in the keratoconus group. Combination of 12% stretching and PEG 2 induced LOXL-4 down-regulation in in healthy group, and all LOXs except LOXL-1 in keratoconus group. The results suggested that combination of mechanical stretching and PGE 2 down-regulate the gene expression of LOXs in keratoconus. Lower LOXs expression may lead to impaired cross-linking, and thus to a loss of cohesion between collagen fibrils, affecting corneal structural stability by collagen lamellae slippage. This may facilitate the development of keratoconus. Exploring the effects of mechanical stretching and inflammatory factor on the expression LOXs in this paper will help us to understand the possible mechanism of how the keratoconus occurs and develops well, and provide the reference for the prevention and treatment of keratoconus.

The Role of the Lysyl Oxidases in Tissue Repair and Remodeling: A Concise Review

Tissue injury provokes a series of events containing inflammation, new tissue formation and tissue remodeling which are regulated by the spatially and temporally coordinated organization. It is an evolutionarily conserved, multi-cellular, multi-molecular process via complex signalling network. Tissue injury disorders present grievous clinical problems and are likely to increase since they are generally associated with the prevailing diseases such as diabetes, hypertension and obesity. Although these dynamic responses vary not only for the different types of trauma but also for the different organs, a balancing act between the tissue degradation and tissue synthesis is the same. In this process, the degradation of old extracellular matrix (ECM) elements and new ones' synthesis and deposition play an essential role, especially collagens. Lysyl oxidase (LOX) and four lysyl oxidase-like proteins are a group of enzymes capable of catalyzing cross-linking reaction of collagen and elastin, thus initiating the formation of covalent cross-links that insolubilize ECM proteins. In this way, LOX facilitates ECM stabilization through ECM formation, development, maturation and remodeling. This ability determines its potential role in tissue repair and regeneration. In this review, based on the current in vitro, animal and human in vivo studies which have shown the significant role of the LOXs in tissue repair, e.g., tendon regeneration, ligament healing, cutaneous wound healing, and cartilage remodeling, we focused on the role of the LOXs in inflammation phase, proliferation phase, and tissue remodeling phase of the repair process. By summarizing its healing role, we hope to shed light on the understanding of its potential in tissue repair and provide up to date therapeutic strategies towards related injuries.

VEGF-ablation therapy reduces drug delivery and therapeutic response in ECM-dense tumors

The inadequate transport of drugs into the tumor tissue caused by its abnormal vasculature is a major obstacle to the treatment of cancer. Anti-vascular endothelial growth factor (anti-VEGF) drugs can cause phenotypic alteration and maturation of the tumor's vasculature. However, whether this consistently improves delivery and subsequent response to therapy is still controversial. Clinical results indicate that not all patients benefit from antiangiogenic treatment, necessitating the development of criteria to predict the effect of these agents in individual tumors. We demonstrate that, in anti-VEGF-refractory murine tumors, vascular changes after VEGF ablation result in reduced delivery leading to therapeutic failure. In these tumors, the impaired response after anti-VEGF treatment is directly linked to strong deposition of fibrillar extracellular matrix (ECM) components and high expression of lysyl oxidases. The resulting condensed, highly crosslinked ECM impeded drug permeation, protecting tumor cells from exposure to small-molecule drugs. The reduced vascular density after anti-VEGF treatment further decreased delivery in these tumors, an effect not compensated by the improved vessel quality. Pharmacological inhibition of lysyl oxidases improved drug delivery in various tumor models and reversed the negative effect of VEGF ablation on drug delivery and therapeutic response in anti-VEGF-resistant tumors. In conclusion, the vascular changes after anti-VEGF therapy can have a context-dependent negative impact on overall therapeutic efficacy. A determining factor is the tumor ECM, which strongly influences the effect of anti-VEGF therapy. Our results reveal the prospect to revert a possible negative effect and to potentiate responsiveness to antiangiogenic therapy by concomitantly targeting ECM-modifying enzymes.

Influence of TNF-α and biomechanical stress on matrix metalloproteinases and lysyl oxidases expressions in human knee synovial fibroblasts

PURPOSE

It was reported that not only ACL but also the synovium may be the major regulator of matrix metalloproteinases (MMPs) in synovial fluids after ACL injury. In order to further confirm whether synovium is capable of regulating the microenvironment in the process of ACL injury, the complicated microenvironment of joint cavity after ACL injury was mimicked and the combined effects of mechanical injury and inflammatory factor [tumour necrosis factor-α (TNF-α)] on expressions of lysyl oxidases (LOXs) and MMPs in synovial fibroblasts derived from normal human synovium were studied.

METHODS

Human normal knee joint synovial fibroblasts were stimulated for 1-6 h with mechanical stretch and inflammatory factor (TNF-α). Total RNA was harvested, reverse transcribed and assessed by real-time polymerase chain reaction for the expression of LOXs and MMP-1, 2, 3 messenger RNAs. MMP-2 activity was assayed from the collected culture media samples using zymography.

RESULTS

Compared to control group, our results showed that 6% physiological stretch increased MMP-2 and LOXs (except LOXL-3), decreased MMP-1 and MMP-3; injurious stretch (12%) decreased LOXs (except LOXL-2)and increased MMP-1, 2 and 3; the combination of injurious stretch and TNF-α decreased LOXs and increased MMP-1, 2 and 3 in synovial fibroblasts in a synergistical manner.

CONCLUSION

This study demonstrated that combination of mechanical injury and inflammatory factors up-regulated the expressions of MMPs and down-regulated the expressions of LOXs in synovial fibroblasts, eventually alter the balance of tissue healing. Thus, synovium may be involved in regulating the microenvironment of joint cavity. Based on the mechanism, early interventions to inhibit the production of MMPs or promote the production of LOXs in the synovial fibroblasts should be performed to facilitate the healing of tissue.

Basic science of anterior cruciate ligament injury and repair

Injury to the anterior cruciate ligament (ACL) is one of the most devastating and frequent injuries of the knee. Surgical reconstruction is the current standard of care for treatment of ACL injuries in active patients. The widespread adoption of ACL reconstruction over primary repair was based on early perception of the limited healing capacity of the ACL. Although the majority of ACL reconstruction surgeries successfully restore gross joint stability, post-traumatic osteoarthritis is commonplace following these injuries, even with ACL reconstruction. The development of new techniques to limit the long-term clinical sequelae associated with ACL reconstruction has been the main focus of research over the past decades. The improved knowledge of healing, along with recent advances in tissue engineering and regenerative medicine, has resulted in the discovery of novel biologically augmented ACL-repair techniques that have satisfactory outcomes in preclinical studies. This instructional review provides a summary of the latest advances made in ACL repair. Cite this article: Bone Joint Res 2014;3:20-31.

Interleukin-1 beta influences on lysyl oxidases and matrix metalloproteinases profile of injured anterior cruciate ligament and medial collateral ligament fibroblasts

PURPOSE

The anterior cruciate ligament (ACL) is known to have a poor healing ability, especially in comparison with the medial collateral ligament (MCL) which can heal relatively well. Interleukin-1beta (IL-1β) is considered to be an important chemical mediator in the acute inflammatory phase of ligament injury. The role of IL-1β-induced expressions of lysyl oxidases (LOXs) and matrix metalloproteinases (MMPs), which respectively facilitate extracellular matrix (ECM) repair and degradation, is poorly understood. In this study, we aim to determine the intrinsic differences between ACL and MCL by characterising the differential expressions of LOXs and MMPs in response to IL-1β in the injury process.

METHODS

Semi-quantitative polymerase chain reaction (PCR), quantitative real-time PCR, Western blot, and zymography were performed.

RESULTS

We detected high expressions of IL-1β-induced LOXs in normal ACL and MCL. Then, we found IL-1β induced injured MCL to express more LOXs than injured ACL (up to 2.85-fold in LOX, 2.58-fold in LOXL-1, 1.89-fold in LOXL-2, 2.46-fold in LOXL-3 and 2.18-fold in LOXL-4). Meanwhile, we found IL-1β induced injured ACL to express more MMPs than injured MCL (up to 1.72-fold in MMP-1, 1.95-fold in MMP-2, 2.05-fold in MMP-3 and 2.3-fold in MMP-12). The further protein results coincided with gene expressions above.

CONCLUSIONS

Lower expressions of LOXs and higher expressions of MMPs might help to explain the poor healing ability of ACL.