Selective Matrix Metalloproteinase Research Articles

Benzisothiazolyliminothiazolidin‐4‐ones with Chondroprotective Properties: Searching for Potent and Selective Inhibitors of MMP‐13

Caring for cartilage: A potent and selective matrix metalloproteinase-13 (MMP-13) inhibitor has been discovered with a novel 2-benzisothiazolylimino-5-benzylidenethiazolidin-4-one scaffold. The structure–activity relationships of the three positional methoxybenzylidene isomers with respect to their chondroprotective effects was evaluated. Molecular modeling provided insight into the binding mode of these non-zinc-chelating (allosteric) inhibitors with MMP-13.

A therapeutic role for matrix metalloproteinase inhibitors in lung diseases?

Disruption of the balance between matrix metalloproteinases (MMPs) and their endogenous inhibitors is considered a key event in the development of pulmonary diseases such as chronic obstructive pulmonary disease, asthma, interstitial lung diseases and lung cancer. This imbalance often results in elevated net MMP activity, making MMP inhibition an attractive therapeutic strategy. Although promising results have been obtained, the lack of selective MMP inhibitors, together with limited knowledge regarding the exact functions of a particular MMP, hampers clinical application. This review discusses the involvement of different MMPs in lung disorders and future opportunities and limitations of therapeutic MMP inhibition.

Decrease in claudin‐2 expression enhances cell migration in renal epithelial madin–darby canine kidney cells

Migration of renal epithelial cells increases after renal tubular damage, but its mechanism has not been clarified in detail. Hyperosmotic stress increased a cellular injury concomitant with a decrease in mRNA and protein expression of claudin-2 in renal tubular epithelial Madin-Darby canine kidney cells. We hypothesized that claudin-2 is involved in the regulation of cell migration. To knockdown claudin-2 expression, we made the cells expressing doxycycline-inducible claudin-2 shRNA vector. Claudin-2 knockdown affected neither the endogenous expression levels of claudin-1, -3, -4, and -7 nor the Triton X-100 solubility of these claudins. Transepithelial electrical resistance was increased by claudin-2 knockdown without affecting permeability to FITC-dextran (4,000 Da). BrdU incorporation assay and cell counting revealed that cell proliferation and viability are unaffected by claudin-2 knockdown. In the wound-healing assay, the recovery rate of wound area was increased by claudin-2 knockdown. The mRNA expression and activity of matrix metalloproteinase-9 (MMP-9) were increased by claudin-2 knockdown. A selective MMP-9 inhibitor suppressed cell migration in the claudin-2 knockdown cells. Hyperosmotic stress increased the expression and activity of MMP-9, which were inhibited by claudin-2 overexpression. These results suggest that the decrease in claudin-2 expression enhances cell migration mediated by the increase in the expression and activity of MMP-9.

532‐nanometer potassium titanyl phosphate (KTP) laser‐induced expression of selective matrix metalloproteinases (MMP) in the rat larynx

The 532-nm KTP laser is clinically useful to induce benign vocal fold lesion regression without a fibrotic response. Previously, we described an in vivo model for KTP-induced injury in the rat larynx. This study uses this model to correlate the KTP-induced histologic and biochemical changes with the absence of long-term vocal fold fibrosis seen in clinical scenarios. In vivo. Unilateral vocal fold injury was induced via KTP laser at 10W (20mS pulse width) as described by our laboratory previously. Animals were subjected to serial endoscopic imaging from postoperative days 1 through 3. Animals were euthanized at 1 day, 4 weeks, and 12 weeks posttreatment and subjected to histologic analyses via hematoxylin and eosin and trichrome staining, as well as RT-PCR analyses for MMP-3, 9, transforming growth factor-beta (TGF-β), and COX-2 mRNA expression. Uninjured vocal folds were used as controls. Our study revealed gross healing of the vocal fold mucosa by 3 days posttreatment, and an immediate, moderate inflammatory infiltrate with no subsequent ultrastructural changes on histology. MMP-3 and COX-2 expression increased transiently, although no changes were seen in expression of MMP-9, an MMP involved in extracellular matrix remodeling, or TGF-β, a profibrotic cytokine. These data suggest that the KTP laser induces a modest inflammatory response, selective MMP expression, and no long-term fibrotic processes in a clinically relevant simulation.

Nonselective matrix metalloproteinase but not tumor necrosis factor-α inhibition effectively preserves the early critical colon anastomotic integrity

Increased matrix metalloproteinase (MMP) activity has been implicated in the pathogenesis of colorectal anastomotic leakage. Tumor necrosis factor-α (TNF-α) induces MMPs and may influence anastomosis repair. We assessed the efficacies of the nonselective hydroxamate MMP inhibitor GM6001, the selective hydroxamate MMP inhibitor AG3340 and a TNF-α antagonist with respect to anastomotic breaking strength of left-sided colon anastomoses in male Sprague-Dawley rats. Systemic GM6001 treatment effectively blocked MMP activity and maintained the initial breaking strength day 0 of the anastomoses when administered subcutaneously as daily depositions (100 mg/kg) or continuously (10 mg/kg/day). In contrast, the anastomotic biomechanic strength was lowered by 55% (p < 0.001) in vehicle-treated rats on postoperative day 3. GM6001 treatment increased breaking strength by 88% (p < 0.0005) compared with vehicle-treated rats day 3 and reduced (p = 0.003) the occurrence of spontaneous anastomotic dehiscence. Histologically, the anastomotic wound was narrower (p < 0.05) in the longitudinal direction in GM6001-treated animals whereas GM6001 had no significant effect on inflammatory cell infiltration or epithelialization. AG3340 (10 mg/kg) increased (p < 0.012) breaking strength by 47% compared with vehicle on day 3 but did not significantly prevent the reduction of the initial breaking strength on day 0. Although the increased TNF-α levels in the wound were attenuated, the anastomotic breaking strength was not improved (p = 0.62) by the TNF-α (10 mg/kg) inhibitor given systemically. Pharmacological nonselective MMP inhibition ought to be explored as a prophylactic regimen to reduce anastomotic complications following colorectal resection. The involvement of TNF-α was insignificant in anastomotic wound healing in an experimental model.

ARP101, a selective MMP-2 inhibitor, induces autophagy-associated cell death in cancer cells

Autophagy is a catabolic cellular process involving self-digestion and turnover of macromolecules and entire organelles. Autophagy is primarily a protective process in response to cellular stress, but it can be associated with cell death. Genetic evidence also supports autophagy function as a tumor suppressor mechanism. To identify specific regulators to autophagy, we screened the Lopac 1280 and the Prestwick chemical libraries using a cell-based screening system with autophagy marker (green fluorescence protein conjugated LC3 protein (GFP-LC3)). We identified ARP101, a selective matrix metalloproteinase-2 (MMP-2) inhibitor as one of the most potent inducer of autophagy. ARP101 treatment was highly effective in inducing the formation of autophagosome and conversion of LC3I into LC3II. Moreover, ARP101-induced autophagy was completely blocked in mouse embryo fibroblasts that lacked autophagy related gene 5 (ATG5 −/− MEF). Interestingly, cell death induced by ARP101 was not inhibited by zVAD, a pan caspase inhibitor, whereas, it was efficiently suppressed by addition of 3-methyladenine, an autophagy inhibitor. These results suggest that the selective MMP-2 inhibitor, ARP101, induces autophagy and autophagy-associated cell death.

Comparison of metalloproteinase protein and activity profiling

Proteolytic enzymes play fundamental roles in many biological processes. Members of the matrix metalloproteinase (MMP) family have been shown to take part in processes crucial in disease progression. The current study used the ExcelArray Human MMP/TIMP Array to quantify MMP and tissue inhibitor of metalloproteinase (TIMP) production in the lysates and media of 14 cancer cell lines and 1 normal cell line. The overall patterns were very similar in terms of which MMPs and TIMPs were secreted in the media versus associated with the cells in the individual samples. However, more MMP was found in the media (in both amount and variety). TIMP-1 was produced in all cell lines. MMP activity assays with three different fluorescence resonance energy transfer (FRET) substrates were then used to determine whether protein production correlated with function for the WM-266-4 and BJ cell lines. Metalloproteinase activity was observed for both cell lines with a general MMP substrate (Knight SSP), consistent with protein production data. However, although both cell lines promoted the hydrolysis of a more selective MMP substrate (NFF-3), metalloproteinase activity was confirmed only in the BJ cell line. The use of inhibitors to confirm metalloproteinase activities pointed to the strengths and weaknesses of in situ FRET substrate assays.

Matrix metalloproteinase-9 potentiates early brain injury after subarachnoid hemorrhage

Objective: This study investigated the role of matrix metalloproteinase-9 (MMP-9) in early brain injury after subarachnoid hemorrhage (SAH).Method: Sprague–Dawley male rats (n=36) weighing between 250 and 300 g were used. SAH was produced by injecting autologous arterial blood into the pre-chiasmatic cistern. MMP-9 protein expression and activity were measured by Western blot and zymogram; laminin expression and neuronal cell in hippocampus were studied by immunohistochemistry and TUNEL staining at 24 hours after SAH in the presence or absence of a selective MMP-9 inhibitor SB-3CT.Result: MMP-9 was activated by SAH and inhibited by SB-3CT at 24 hours after SAH (p<0.01). Laminin, the substrate of MMP-9, was decreased at 24 hours after SAH, and SB-3CT prevented laminin degradation. The number of TUNEL-positive neurons in hippocampus was increased after SAH and decreased by SB-3CT (p<0.01). In addition, brain water content and neurological functional abnormalities were attenuated by SB-3CT.Conclusion: MMP-9 may be involved in early brain injury through degradation of laminin and neuronal death, and inhibition of MMP-9 may be a potential direction for brain protection after SAH.

Profiling of matrix metalloproteinases and tissue inhibitors of metalloproteinases proteins in bladder urothelial carcinoma

We investigated the matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinase (TIMPs) proteins in transitional cell carcinoma (TCC) cell lines and surgical specimens of the bladder neoplasm. The expression level was correlated to the degree of cellular differentiation and invasiveness of bladder cancer. Panels of six TCC cell lines with different degrees of differentiation were tested with monoclonal antibodies (mAbs) to MMP-1, MMP-2, MMP-3, MMP-9a, MMP-9b, TIMP-1 and TIMP-2 by immunocytochemistry. Gelatin zymography was also conducted on the cell lines for MMP-2 and -9. In addition, immunohistochemistry with the mAbs to MMP and TIM molecules was performed on 30 TCC specimens. We found that TCC cell lines were stained positively for MMP-1 (6/6), weakly for MMP-9a (2/6), MMP9b (5/6) and TIMP-1 (3/6), and negatively for MMP-2 (3/6) and MMP-3 (3/6). Zymographic analysis of the cell lines showed a high level of MMP2 in the MGH-U4 cell line. In bladder cancer surgical specimens, all specimens were positive for MMP1 (30/30), 19 were positive for MMP-2 (63.3%), 21 positive for MMP-9a (70%) and 15 positive for MMP-9b (50%). The expression of MMP-2 was found to be positively correlated with higher-grade tumors (p=0.036) and the expression of MMP-9a and -9b was found to be positively correlated with tumor stage (p=0.012 and 0.023, respectively). However, the expression of MMP-1, MMP-3, TIMP-1 and TIMP-2 was not correlated with either tumor staging or grading. In conclusion, the expression of MMP-2 and -9 was correlated with high-grade or high-stage bladder tumors, respectively. However, this correlation was not observed with TCC cell lines in which high- and low-grade tumors are included. Immunohistochemical results on tumor lesions may have more clinical relevance, since in a given tumor microenvironment the interaction among tumor cells in situ and tumor-associated cells, such as neutrophils, macrophages, lymphocytes and endothelial cells, as well as environmental factors (hypoxia and pH), cytokines and growth factors released by these cells may be required for TCC to express selective MMPs and TIMPs. The selective expression of these molecules then regulates tumor progression.

Cartilage degradation biomarkers predict efficacy of a novel, highly selective matrix metalloproteinase 13 inhibitor in a dog model of osteoarthritis: Confirmation by multivariate analysis that modulation of type ii collagen and aggrecan degradation peptides parallels pathologic changes

To demonstrate that the novel highly selective matrix metalloproteinase 13 (MMP-13) inhibitor PF152 reduces joint lesions in adult dogs with osteoarthritis (OA) and decreases biomarkers of cartilage degradation. The potency and selectivity of PF152 were evaluated in vitro using 16 MMPs, TACE, and ADAMTS-4 and ADAMTS-5, as well as ex vivo in human cartilage explants. In vivo effects were evaluated at 3 concentrations in mature beagles with partial medial meniscectomy. Gross and histologic changes in the femorotibial joints were evaluated using various measures of cartilage degeneration. Biomarkers of cartilage turnover were examined in serum, urine, or synovial fluid. Results were analyzed individually and in combination using multivariate analysis. The potent and selective MMP-13 inhibitor PF152 decreased human cartilage degradation ex vivo in a dose-dependent manner. PF152 treatment of dogs with OA reduced cartilage lesions and decreased biomarkers of type II collagen (type II collagen neoepitope) and aggrecan (peptides ending in ARGN or AGEG) degradation. The dose required for significant inhibition varied with the measure used, but multivariate analysis of 6 gross and histologic measures indicated that all doses differed significantly from vehicle but not from each other. Combined analysis of cartilage degradation markers showed similar results. This highly selective MMP-13 inhibitor exhibits chondroprotective effects in mature animals. Biomarkers of cartilage degradation, when evaluated in combination, parallel the joint structural changes induced by the MMP-13 inhibitor. These data support the potential therapeutic value of selective MMP-13 inhibitors and the use of a set of appropriate biomarkers to predict efficacy in OA clinical trials.

Matrix metalloproteinase activity assays: Importance of zymography

Introduction: Matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases capable of degrading extracellular matrix, including the basement membrane. MMPs are associated with various physiological processes such as morphogenesis, angiogenesis, and tissue repair. Moreover, due to the novel non-matrix related intra- and extracellular targets of MMPs, dysregulation of MMP activity has been implicated in a number of acute and chronic pathological processes, such as arthritis, acute myocardial infarction, chronic heart failure, chronic obstructive pulmonary disease, inflammation, and cancer metastasis. MMPs are considered as viable drug targets in the therapy of the above diseases. Methods: For the development of selective MMP inhibitor molecules, reliable methods are necessary for target validation and lead development. Here, we discuss the major methods used for MMP assays, focusing on substrate zymography. We highlight some problems frequently encountered during sample preparations, electrophoresis, and data analysis of zymograms. Results and Discussion: Zymography is a widely used technique to study extracellular matrix-degrading enzymes, such as MMPs, from tissue extracts, cell cultures, serum or urine. This simple and sensitive technique identifies MMPs by the degradation of their substrate and by their molecular weight and therefore helps to understand the widespread role of MMPs in different pathologies and cellular pathways.

Alloxan Derivatives as Inhibitors of Matrix Metalloproteinase-2: Theoretical Calculations and Experimental Results

Matrix metalloproteinases (MMPs) are a family of structurally related zinc-containing endopeptidases involved in tissue remodelling and degradation of the extracellular matrix. The failure of common synthetic inhibitors makes the design of new selective and potent MMP inhibitors an extreme challenge in health care for the treatment of various pathological states such as inflammation, arthritis, and cancer. In this view, an over-expression of MMP-2 is supposed to be responsible for the occurrence of many different human tumours and inflammatory processes involving the hydrolysis of the type IV collagen, the main component of the basement membrane. A series of studies therefore focused on the design of new potential inhibitors biased towards MMP-2: campaigns of molecular virtual screening of several large chemical libraries resulted in a number of attractive hits. Interestingly, a shortlist of alloxan-like structures was selected with inhibition constants in the nM range. In this respect, we investigated a series of complexes of MMP-2 with alloxan inhibitors by thermodynamic integration in all atoms molecular dynamics simulations. We thus obtained quantitative differences in binding free energies for a list of alloxan compounds. On this basis, we were able to elucidate the molecular rationale for the remarkable inhibition exerted by these compounds with the ultimate aim of driving the synthesis of new more potent and selective derivatives that are at present awaiting for further experimental investigations through enzymatic assays.

Matrix Metalloproteinases in Vascular Disease - A Potential Therapeutic Target?

This paper aims to summarize the scientific rationale and future perspectives in the development of effective matrix metalloproteinase (MMP) modulators in the management of patients with arterial and venous disease. Pubmed, Embase and Cinahl databases were searched using the search terms 'MMP', 'matrix metalloproteinase', 'arterial disease', 'venous disease', 'aneurysm', 'vascular disease', 'atherosclerosis' and 'varicose veins'. Articles focussing on aneurysm disease, peripheral arterial disease, carotid stenosis and venous disorders were included. Animal studies assessing MMP expression have demonstrated that MMP-2 and MMP-9 may contribute to arterial aneurysm formation and in atherosclerosis. Human studies and animal models have shown that MMP-3 and MMP-9 may have a protective role against plaque development and destabilization whereas MMP-12 might promote these changes. In venous disease, increased expression of MMP-1, MMP-9 and MMP-13 have been shown in human varicose veins. MMP-2 and MMP-9 were also shown to be upregulated in experimentally induced venous hypertension and higher concentrations of MMP-2 in wound exudate and biopsies have been shown to correlate with impaired venous ulcer healing. The use of statins has become widespread in patients with arterial disease and MMP inhibition is likely to contribute to the mechanism of action. More selective MMP modulators are currently being developed, although clinical studies are currently lacking. MMPs have been directly implicated in the pathophysiology of many arterial and venous disorders and remain an important potential therapeutic target. Studies are needed to further develop and demonstrate the clinical benefits of MMP modulating agents.

A novel and selective membrane type-1 matrix metalloproteinase (MT1-MMP) inhibitor reduces cancer cell motility and tumor growth

Matrix metalloproteinases (MMPs), and especially membrane type-1 matrix metalloproteinase (MT1-MMP, MMP-14), play a role in cancer progression and can have a prognostic value. Various synthetic broad-spectrum MMP inhibitors have been developed but have had little success in cancer patient treatment owing to side effects. Until recently, selective targeting of specific MMPs has not been possible due to lack of specific inhibitors. Here we have developed a selective MT1-MMP peptideinhibitor GACFSIAHECGA, which did not affect the activities of many other MMPs including MMP-1, -2, -3, -7, -8, -9, -10, -11, -12, -13, -15, -17 or -20. In a fluorescent peptide cleavage assay it displayed an IC50 value of 150 μM. The peptide effectively inhibited the migration and invasion of cancer cell lines in vitro. Furthermore, in vivo the peptide reduced the growth of tongue carcinoma xenografts and prolonged the survival of mice. Overall these results suggest that selective MT1-MMP inhibitors may have utility as anticancer agents.

Selective Matrix Metalloproteinase Inhibitors for Cancer

The matrix metalloproteinases are a family of nearly 30 enzymes that are intimately involved in tissue remodeling. Disease processes associated with the matrix metalloproteinases are generally related to imbalance between the inhibition and activation of matrix metalloproteinases resulting in excessive degradation of the extracellullar matrix. These include osteoarthritis, rheumatoid arthritis, tumor metastasis and congestive heart failure. Despite massive research and development efforts, there are only two drugs launched on the market: periostat (doxycycline), a tetracycline used for periodontal disease and glucosemine sulfate, for osteoarthritis. Possible reasons for the low success rate of matrix metalloproteinase inhibitors in the clinic are mainly from unwanted side effects caused by their lack of selectivity, since inhibition of collagenase-1 may be responsible for the musculoskeletal side effects observed clinically with broad-spectrum inhibitors. Considering these data, many efforts were directed to developing a more selective second generation of inhibitors against the specific matrix metalloproteinases believed to be involved in the different pathologies. This review mainly focuses on selective matrix metalloproteinase inhibitors development on matrix metalloproteinases in terms of antitumor since the late 90s, in terms of synthetic compounds of low molecular mass incorporating specific zinc-binding groups, natural products and their derivatives. Through these methods, new hope is emerging in the form of synthetic and natural matrix metalloproteinase inhibitors for the prevention and treatment of cancer.

Distinct progression‐associated expression of tumor and stromal MMPs in HaCaT skin SCCs correlates with onset of invasion

Matrix metalloproteinases (MMPs) are critically involved in tumor invasion and metastasis. However, failure of broad spectrum MMP inhibitors in clinical trials emphasizes the need for detailed analyses of the specific role of different MMPs in tumor malignancy. Using HaCaT-keratinocyte clones representing distinct stages in skin squamous cell carcinoma (SCC) progression, we demonstrate the expression of specific tumor and stroma-derived MMPs with the onset and maintenance of tumor invasion. Although MMP-9-positive leukocytes are present in benign and malignant tumor transplants at the onset of stromal activation and angiogenesis, mRNA expression of stroma-derived MMP-9 as well as MMP-2, -13 and -14 is exclusively found in enhanced malignant tumor transplants. Their expression initiates with the onset of invasion, whereas being absent in early noninvasive stages of malignant transplants. In addition, a high expression of tumor-derived MMP-1, -2 and -14 contributes to malignant and invasive tumor growth. However, stroma-derived MMP-3 is exclusively restricted to very late-stage invasive and malignant transplants. The functional contribution of these proteases to invasive growth is supported by the gelatinolytic activity in the tumor transplants that again initiates with the onset of invasive growth suggesting a crucial role of MMP-2, -9, -13 and -14 for the establishment of a reactive stroma that promotes tumor invasion. These data demonstrate a complex cooperation of distinct tumor and stroma-derived MMPs in the establishment of malignant tumors and provide the basis for a more specific use of highly selective MMP inhibitors during distinct stages of tumor progression.

The role of MMP-9 in integrin-mediated hippocampal cell death after pilocarpine-induced status epilepticus

Recent studies demonstrate that matrix metalloproteinase-9 (MMP-9) is closely involved in the pathogenesis of epilepsy. This study investigated the role of MMP-9 in hippocampal cell death after pilocarpine-induced status epilepticus (SE). We showed that MMP-9 expression and activity significantly increased and β1-integrin levels decreased on day 3 after SE. β1-integrin degradation was also observed in hippocampal ex vivo extracts incubated with recombinant active MMP-9. Treatment with a selective MMP-9 inhibitor attenuated MMP-9 up-regulation, β1-integrin degradation, the reduction of ILK activity and Akt phosphorylation, and subsequent hippocampal damage after SE. However, co-treatment with anti-β1-integrin antibody almost completely blocked the protective effects of the MMP-9 inhibitor on both integrin-mediated survival signaling and hippocampal cell death. Our study demonstrates that MMP-9 induces apoptotic hippocampal cell death by interrupting integrin-mediated survival signaling after SE and suggests that MMP-9 may be a promising target for a neuroprotective approach to preventing seizure-induced hippocampal damage.

N-O-Isopropyl Sulfonamido-Based Hydroxamates: Design, Synthesis and Biological Evaluation of Selective Matrix Metalloproteinase-13 Inhibitors as Potential Therapeutic Agents for Osteoarthritis

Matrix metalloproteinase-13 (MMP-13) is a key enzyme implicated in the degradation of the extracellular matrix in osteoarthritis (OA). For this reason, MMP-13 synthetic inhibitors are being sought as potential therapeutic agents to prevent cartilage degradation and to halt the progression of OA. Herein, we report the synthesis and in vitro evaluation of a new series of selective MMP-13 inhibitors possessing an arylsulfonamidic scaffold. Among these potential inhibitors, a very promising compound was discovered exhibiting nanomolar activity for MMP-13 and was highly selective for this enzyme compared to MMP-1, -14, and TACE. This compound acted as a slow-binding inhibitor of MMP-13 and was demonstrated to be effective in an in vitro collagen assay and in a model of cartilage degradation. Furthermore, a docking study was conducted for this compound in order to investigate its binding interactions with MMP-13 and the reasons for its selectivity toward MMP-13 versus other MMPs.

Matrix Metalloprotease Inhibitors Suppress Initiation and Progression of Chondrogenic Differentiation of Mesenchymal Stromal Cells In Vitro

Mesenchymal stromal cells (MSC) are an attractive source for cell therapy and tissue engineering of joint cartilage. Common chondrogenic in vitro protocols, however, induce hypertrophic markers like COL10A1, matrix metalloproteinase 13 (MMP13), and alkaline phosphatase (ALP) reminiscent of endochondral bone formation. To direct MSC toward articular chondrocytes more specifically, a better understanding of the regulatory steps is desirable. Proteases are important players in matrix remodeling, display inhibitory effects on growth plate development and MMP13 inhibition prevented hypertrophy of bovine chondrocytes. The aim of this study was to evaluate whether the activity of proteases and MMPs, especially MMP13, is crucial for the transition of MSC toward mature chondrocytes and could allow to selectively influence aspects of early and late chondrogenic differentiation. Protease inhibitors were added during MSC chondrogenesis and stage-specific markers were assessed by histology, qPCR, and ALP quantification. Chondrogenesis was little affected by leupeptin, pepstatin, or aprotinin. In contrast, broad spectrum pan-MMP inhibitors dose dependently suppressed proteoglycan deposition, collagen type II and type X staining, ALP activity, and reduced SOX9 and COL2A1 expression. A selective MMP13 inhibitor allowed chondrogenesis and showed only weak effects on ALP activity. In conclusion, transition of MSC toward mature chondrocytes in vitro depended on molecules suppressed by pan-MMP inhibitors identifying chondrogenic differentiation of MSC as a sophistically regulated process in which catabolic enzymes are capable to directly influence cellular fate. In future therapeutic applications of diseased joints, the tested MMP13-specific inhibitor promises suppression of collagen type II degradation without imposing a risk to impair MSC-driven regeneration processes.

Roles of Matrix Metalloproteinases in Flow-Induced Outward Vascular Remodeling

Sustained hemodynamic stresses, especially high blood flow, result in flow-induced outward vascular remodeling. Our previous study showed that macrophage depletion reduced flow-induced outward remodeling of the rat common carotid artery, indicating that macrophages are critical in flow-induced outward vascular remodeling. Macrophage is known to release proteinases, including matrix metalloproteinases (MMPs). Degradation and loosening of extracellular matrix by MMPs may facilitate vascular remodeling. Therefore, we assessed the functions of MMPs in flow-induced outward vascular remodeling by using the flow-augmented common carotid artery model in mice. We validated that ligation of the left common carotid artery increased blood flow and luminal diameter of the right common carotid artery without significant change in blood pressure of mice. To assess the functions of MMPs in flow-induced outward vascular remodeling, we used doxycycline (broad-spectrum MMP inhibitor), SB-3CT (selective MMP inhibitor), MMP-9 knockout mice, and MMP-12 knockout mice. Although there was only a trend for doxycycline treatment to reduce flow-induced outward vascular remodeling, SB-3CT treatment significantly reduced flow-induced outward vascular remodeling. In addition, flow-induced outward vascular remodeling was significantly reduced in MMP-9 knockout mice, but not in MMP-12 knockout mice. These data revealed that MMPs, especially MMP-9, are critical in flow-induced outward vascular remodeling.