Caveolin-1 inhibits membrane-type 1 matrix metalloproteinase activity

Is the endotoxin-complement cascade the major driver in lipedema?

Lipedema is a poorly understood disorder of adipose tissue characterized by abnormal but symmetrical deposition of subcutaneous white adipose tissue (WAT) in proximal extremities. Here, we propose that the underlying cause for lipedema could be triggered by a selective accumulation of bacterial lipopolysaccharides (LPS; also known as endotoxin) in gluteofemoral WAT. Together with a malfunctioning complement system, this induces low-grade inflammation in the depot and raises its uncontrollable expansion. Correspondingly, more attention should be paid in future research to the endotoxemia prevalent in patients with lipedema. We would like to propose that proper management of endotoxemia can reduce the progression and even improve the state of disease in patients with lipedema.

Lipedema: Insights into Morphology, Pathophysiology, and Challenges

Lipedema is an adipofascial disorder that almost exclusively affects women. Lipedema leads to chronic pain, swelling, and other discomforts due to the bilateral and asymmetrical expansion of subcutaneous adipose tissue. Although various distinctive morphological characteristics, such as the hyperproliferation of fat cells, fibrosis, and inflammation, have been characterized in the progression of lipedema, the mechanisms underlying these changes have not yet been fully investigated. In addition, it is challenging to reduce the excessive fat in lipedema patients using conventional weight-loss techniques, such as lifestyle (diet and exercise) changes, bariatric surgery, and pharmacological interventions. Therefore, lipedema patients also go through additional psychosocial distress in the absence of permanent treatment. Research to understand the pathology of lipedema is still in its infancy, but promising markers derived from exosome, cytokine, lipidomic, and metabolomic profiling studies suggest a condition distinct from obesity and lymphedema. Although genetics seems to be a substantial cause of lipedema, due to the small number of patients involved in such studies, the extrapolation of data at a broader scale is challenging. With the current lack of etiology-guided treatments for lipedema, the discovery of new promising biomarkers could provide potential solutions to combat this complex disease. This review aims to address the morphological phenotype of lipedema fat, as well as its unclear pathophysiology, with a primary emphasis on excessive interstitial fluid, extracellular matrix remodeling, and lymphatic and vasculature dysfunction. The potential mechanisms, genetic implications, and proposed biomarkers for lipedema are further discussed in detail. Finally, we mention the challenges related to lipedema and emphasize the prospects of technological interventions to benefit the lipedema community in the future.

Membrane-type I matrix metalloproteinase (MT1-MMP), lipid metabolism and therapeutic implications

Lipids exert many essential physiological functions, such as serving as a structural component of biological membranes, storing energy, and regulating cell signal transduction. Dysregulation of lipid metabolism can lead to dyslipidemia related to various human diseases, such as obesity, diabetes, and cardiovascular disease. Therefore, lipid metabolism is strictly regulated through multiple mechanisms at different levels, including the extracellular matrix. Membrane-type I matrix metalloproteinase (MT1-MMP), a zinc-dependent endopeptidase, proteolytically cleaves extracellular matrix components, and non-matrix proteins, thereby regulating many physiological and pathophysiological processes. Emerging evidence supports the vital role of MT1-MMP in lipid metabolism. For example, MT1-MMP mediates ectodomain shedding of low-density lipoprotein receptor and increases plasma low-density lipoprotein cholesterol levels and the development of atherosclerosis. It also increases the vulnerability of atherosclerotic plaque by promoting collagen cleavage. Furthermore, it can cleave the extracellular matrix of adipocytes, affecting adipogenesis and the development of obesity. Therefore, the activity of MT1-MMP is strictly regulated by multiple mechanisms, such as autocatalytic cleavage, endocytosis and exocytosis, and post-translational modifications. Here, we summarize the latest advances in MT1-MMP, mainly focusing on its role in lipid metabolism, the molecular mechanisms regulating the function and expression of MT1-MMP, and their pharmacotherapeutic implications.

Hold on or Cut? Integrin- and MMP-Mediated Cell-Matrix Interactions in the Tumor Microenvironment

The tumor microenvironment (TME) has become the focus of interest in cancer research and treatment. It includes the extracellular matrix (ECM) and ECM-modifying enzymes that are secreted by cancer and neighboring cells. The ECM serves both to anchor the tumor cells embedded in it and as a means of communication between the various cellular and non-cellular components of the TME. The cells of the TME modify their surrounding cancer-characteristic ECM. This in turn provides feedback to them via cellular receptors, thereby regulating, together with cytokines and exosomes, differentiation processes as well as tumor progression and spread. Matrix remodeling is accomplished by altering the repertoire of ECM components and by biophysical changes in stiffness and tension caused by ECM-crosslinking and ECM-degrading enzymes, in particular matrix metalloproteinases (MMPs). These can degrade ECM barriers or, by partial proteolysis, release soluble ECM fragments called matrikines, which influence cells inside and outside the TME. This review examines the changes in the ECM of the TME and the interaction between cells and the ECM, with a particular focus on MMPs.

The MMP14-caveolin axis and its potential relevance for lipoedema

Lipoedema is associated with widespread adipose tissue expansion, particularly in the proximal extremities. The mechanisms that drive the development of lipoedema are unclear. In this Perspective article, we propose a new model for the pathophysiology of lipoedema. We suggest that lipoedema is an oestrogen-dependent disorder of adipose tissue, which is triggered by a dysfunction of caveolin 1 (CAV1) and subsequent uncoupling of feedback mechanisms between CAV1, the matrix metalloproteinase MMP14 and oestrogen receptors. In addition, reduced CAV1 activity also leads to the activation of ERα and impaired regulation of the lymphatic system through the transcription factor prospero homeobox 1 (PROX1). The resulting upregulation of these factors could effectively explain the main known features of lipoedema, such as adipose hypertrophy, dysfunction of blood and lymphatic vessels, the overall oestrogen dependence and the associated sexual dimorphism, and the mechanical compliance of adipose tissue.

Different Role of Caveolin-1 Gene in the Progression of Gynecological Tumors

Caveolin-1 (Cav-1), an integral membrane protein, is a principal component of caveolae and has been reported to play a promoting or inhibiting role in cancer progression. Gynecologic tumor is a group of tumors that affect the tissue and organs of the female reproductive system, especially cervical cancer. Cervical cancer, as one of the most common cancers, severely affects female health in developing countries in particular because of its high morbidity and mortality. This review summarizes some mechanisms of Cav-1 in the development and progression of gynecological tumors. The role of Cav-1 in tumorigenesis, including dysregulation of cell cycle, apoptosis and autophagy, adhesion, invasion, and metastasis, such as the formation of invadopodia and matrix metalloproteinase degradation are presented in detail. In addition, Cav-1 modulates autophagy and the formation of invadopodia and target regulated by miRNAs to affect tumor progress. Taken together, we find that, no matter Cav-1 expression in the tumor or stromal cells , Cav-1 has paradoxical role in different types of gynecological tumors in vivo or in vitro and even in the same tumor from the same organ.

Hypoxia Activates Src and Promotes Endocytosis Which Decreases MMP-2 Activity and Aggravates Renal Interstitial Fibrosis

The aggravation of renal interstitial fibrosis in the advanced-stage of chronic kidney disease is related to decreased matrix metalloproteinase-2 (MMP-2) activity, which is induced by hypoxia in the kidney; however, the specific mechanism remains unclear. We previously demonstrated that inhibition of Caveolin-1, a key gene involved in endocytosis, increased MMP-2 activity in hypoxic HK-2 cells. It has been reported that activated Src (phospho-Src Tyr416) is a key molecule in multiple fibrotic pathways. However, whether Src functions on the regulation of Caveolin-1 and MMP-2 activity in hypoxic HK-2 cells remains poorly understood. To explore the underlying mechanism, a rat model of renal interstitial fibrosis was established, then we observed obvious hypoxia in fibrotic kidney tissue and the protein levels of phospho-Src and Caveolin-1 increased, while MMP-2 activity decreased. Next, we treated HK-2 cells with the phospho-Src inhibitor PP1. Compared with normal cells grown in hypoxia, in cells treated with PP1, the protein levels of phospho-Src and Caveolin-1 decreased, as did the protein levels of the MMP-2-activity-regulated molecules RECK (reversion-inducing-cysteine-rich protein with kazal motifs) and TIMP-2 (tissue inhibitor of metalloproteinase-2), while the protein level of MT1-MMP (membrane type 1-matrix metalloproteinase) increased and MMP-2 activity was enhanced. Therefore, hypoxia promotes the phosphorylation of Src and phospho-Src can enhance the endocytosis of HK-2 cells, which leads to decreased MMP-2 activity and aggravates renal interstitial fibrosis.

MMP-2 and 9 in Chronic Kidney Disease

Gelatinases are members of the matrix metalloproteinase (MMPs) family; they play an important role in the degradation of the extracellular matrix (ECM). This effect is also crucial in the development and progression of chronic kidney disease (CKD). Its expression, as well as its activity regulation are closely related to the cell signaling pathways, hypoxia and cell membrane structural change. Gelatinases also can affect the development and progression of CKD through the various interactions with tumor necrosis factors (TNFs), monocyte chemoattractant proteins (MCPs), growth factors (GFs), oxidative stress (OS), and so on. Currently, their non-proteolytic function is a hot topic of research, which may also be associated with the progression of CKD. Therefore, with the in-depth understanding about the function of gelatinases, we can have a more specific and accurate understanding of their role in the human body.

Effects of autophagy and endocytosis on the activity of matrix metalloproteinase‑2 in human renal proximal tubular cells under hypoxia

Tubulointerstitial fibrosis is characterized by tubular atrophy with basement membrane thickening and accumulation of interstitial extracellular matrix (ECM). A decrease in the activity of matrix metalloproteinase‑2 (MMP‑2) may promote this process. Although proximal tubular cells are sensitive to oxygen deprivation, whether cellular autophagy or endocytosis induced by hypoxia can alter the activity of MMP‑2 remains to be elucidated. The aim of the present study was to investigate whether autophagy and endocytosis induced by hypoxia can have an effect on the activity of MMP‑2 in HK‑2 cells. The investigations involved exposing the HK‑2 cell line to an autophagy inhibitor, 3‑MA, or an endocytotic inhibitor, filipin. The mRNA expression of MMP‑2 was elevated in the hypoxic milieu. Furthermore, it was found that filipin increased the activity of MMP‑2 under hypoxia. These results suggested that autophagy and endocytosis were potential mediators for the altered expression of MMP‑2, and endocytosis was a potential target for regulating the activity of MMP‑2. These data suggested that hypoxia may be an important pro‑fibrogenic stimulus, which acts in part via endocytosis.

Mechanotransduction pulls the strings of matrix degradation at invadosome

Degradation of the extracellular matrix is a critical step of tumor cell invasion. Both protease-dependent and -independent mechanisms have been described as alternate processes in cancer cell motility. Interestingly, some effectors of protease-dependent degradation are focalized at invadosomes and are directly coupled with contractile and adhesive machineries composed of multiple mechanosensitive proteins. This review presents recent findings in protease-dependent mechanisms elucidating the ways the force affects extracellular matrix degradation by targeting protease expression and activity at invadosome. The aim is to highlight mechanosensing and mechanotransduction processes to direct the degradative activity at invadosomes, with the focus on membrane tension, proteases and mechanosensitive ion channels.

Caveolin-1 regulates the expression of tight junction proteins during hyperoxia-induced pulmonary epithelial barrier breakdown

BACKGROUND

Bronchopulmonary dysplasia (BPD) is a common complication in preterm infants that involves the downregulation of tight junction (TJ) proteins. However, the mechanism underlying downregulation of the expression of TJ proteins during at the early stages of hyperoxia-induced BPD remains to be understood. Here, we aimed to identify the role of caveolin-1 (Cav-1) in hyperoxia-induced pulmonary epithelial barrier breakdown.

METHODS

First, we established an in vitro pulmonary epithelial barrier models using primary type II alveolar epithelial cells (AEC-II) from newborn rats. AEC-II was assigned to the hyperoxic (85 % O2/5 % CO2) or normoxic (21 % O2/5 % CO2) groups. Second, AEC-II was transfected with Cav-1-siRNA to downregulate Cav-1 under normoxic exposure. Third, AEC-II was transfected with a cDNA encoding Cav-1 to upregulate Cav-1 expression under hyperoxic exposure. Then, expression levels of Cav-1 and TJ proteins were examined by immunofluorescence staining, reverse transcription-polymerase chain reaction, and Western blotting. The TJ structures visualized using a transmission electron microscope, and transepithelial resistance and apparent permeability coefficient of fluorescein isothiocyanate-dextran, which are indicators of barrier function, were measured.

RESULTS

Our data showed that exposure to hyperoxia disrupted the structure and function of the pulmonary epithelial barrier and decreased the ZO-1, occludin, claudin-4, and Cav-1 expression levels. Moreover, Cav-1 knockdown attenuated the expression of the other three genes and disrupted pulmonary epithelial barrier structure and function under normoxic exposure. However, Cav-1 upregulation markedly antagonized the hyperoxia-induced pulmonary epithelial barrier destruction and TJ protein loss.

CONCLUSIONS

This is the first study to present evidence illustrating the novel role of Cav-1 downregulation-mediated TJ protein loss in pulmonary epithelial barrier destruction during BPD.

Down-regulation of stromal caveolin-1 expression in esophageal squamous cell carcinoma: a potent predictor of lymph node metastases, early tumor recurrence, and poor prognosis

BACKGROUND

Recent studies have identified loss of stromal caveolin-1 (Cav-1) expression as a new prognostic histological characteristic in various types of human cancers. However, the clinical and pathological significance of stromal Cav-1 expression in esophageal squamous cell carcinoma (ESCC) remains largely unknown. We examined Cav-1 expression in both tumor and stromal cells in ESCC tissue by immunohistochemical analysis to evaluate its clinicopathological significance and prognostic value.

METHODS

A total of 110 patients with ESCC who underwent surgical resection were included in this study. The expression of Cav-1 in both tumor and stromal cells in esophageal tumor tissues was examined immunohistochemically.

RESULTS

Cav-1 expression was found in the cytoplasm of both tumor and stromal cells. Tumor Cav-1 overexpression was observed in 37.3 % tumors, which correlated to deeper tumor invasion (p = 0.038). Down-regulation of stromal Cav-1 expression was observed in 40.9 % tumors. The stromal Cav-1 down-regulation group had more lymph node metastases and more locoregional recurrences than those with higher expression (p = 0.020 and p = 0.002, respectively). In addition, down-regulation of stromal Cav-1 expression was associated with shorter disease-free survival (p < 0.001) and overall survival (p < 0.001). Multivariate analysis revealed that down-regulation of stromal Cav-1 expression was an independent prognostic factor for both disease-free survival (p = 0.028) and overall survival (p = 0.007).

CONCLUSIONS

Down-regulation of stromal Cav-1 expression in ESCC had high malignant potential. It predicts high-risk of lymph node metastases and locoregional recurrence, and it could be a powerful prognostic marker for patients with ESCC.

Caveolin-1 is a negative regulator of tumor growth in glioblastoma and modulates chemosensitivity to temozolomide

Caveolin-1 (Cav-1) is a critical regulator of tumor progression in a variety of cancers where it has been shown to act as either a tumor suppressor or tumor promoter. In glioblastoma multiforme, it has been previously demonstrated to function as a putative tumor suppressor. Our studies here, using the human glioblastoma-derived cell line U-87MG, further support the role of Cav-1 as a negative regulator of tumor growth. Using a lentiviral transduction approach, we were able to stably overexpress Cav-1 in U-87MG cells. Gene expression microarray analyses demonstrated significant enrichment in gene signatures corresponding to downregulation of MAPK, PI3K/AKT and mTOR signaling, as well as activation of apoptotic pathways in Cav-1-overexpressing U-87MG cells. These same gene signatures were later confirmed at the protein level in vitro. To explore the ability of Cav-1 to regulate tumor growth in vivo, we further show that Cav-1-overexpressing U-87MG cells display reduced tumorigenicity in an ectopic xenograft mouse model, with marked hypoactivation of MAPK and PI3K/mTOR pathways. Finally, we demonstrate that Cav-1 overexpression confers sensitivity to the most commonly used chemotherapy for glioblastoma, temozolomide. In conclusion, Cav-1 negatively regulates key cell growth and survival pathways and may be an effective biomarker for predicting response to chemotherapy in glioblastoma.

Role of caveolin-1 in fibrotic diseases

Fibrosis underlies the pathogenesis of numerous diseases and leads to severe damage of vital body organs and, frequently, to death. Better understanding of the mechanisms resulting in fibrosis is essential for developing appropriate treatment solutions and is therefore of upmost importance. Recent evidence suggests a significant antifibrotic potential of an integral membrane protein, caveolin-1. While caveolin-1 has been widely studied for its role in the regulation of cell signaling and endocytosis, its possible implication in fibrosis remains largely unclear. In this review we survey involvement of caveolin-1 in various cellular processes and highlight different aspects of its antifibrotic activity. We hypothesize that caveolin-1 conveys a homeostatic function in the process of fibrosis by (a) regulating TGF-β1 and its downstream signaling; (b) regulating critical cellular processes involved in tissue repair, such as migration, adhesion and cellular response to mechanical stress; and (c) antagonizing profibrotic processes, such as proliferation. Finally, we consider this homeostatic function of caveolin-1 as a possible novel approach in treatment of fibroproliferative diseases.

Caveolin-1 as a promoter of tumour spreading: when, how, where and why

Caveolae are non-clathrin invaginations of the plasma membrane in most cell types; they are involved in signalling functions and molecule trafficking, thus modulating several biological functions, including cell growth, apoptosis and angiogenesis. The major structural protein in caveolae is caveolin-1, which is known to act as a key regulator in cancer onset and progression through its role as a tumour suppressor. Caveolin-1 can also promote cell proliferation, survival and metastasis as well as chemo- and radioresistance. Here, we discuss recent findings and novel concepts that support a role for caveolin-1 in cancer development and its distant spreading. We also address the potential application of caveolin-1 in tumour therapy and diagnosis.

Restoration of caveolin-1 expression suppresses growth, membrane-type-4 metalloproteinase expression and metastasis-associated activities in colon cancer cells

Caveolin-1 (cav-1) and flotillin-1 are two major structural proteins associated with lipid rafts in mammalian cells. The membrane-type matrix metalloproteinases (MT-MMPs) are expressed at the cell surface, hydrolyze extracellular matrix, and play an important role in cancer cell migration and metastasis. Expression of cav-1, flotillin-1, and MT4-MMP in lysates and lipid rafts of LS174T and HM-7 colon cancer cells was determined. The impact of restoration of cav-1 expression on proliferation, adhesion, motility in vitro, and growth of implanted tumors in vivo was characterized. Cav-1 is not expressed in lipid rafts of the highly metastatic colon cancer cell line (HM-7), but expressed in cytosolic fractions of the parental lower metastatic cell line (LS174T). In contrast, MT4-MMP was expressed in lipid rafts of HM-7 cells but not in LS174T cells. Overexpression of cav-1 in HM-7 cells down-regulate proliferation, viability, wound closure, adhesion to laminin, invasion, and development of filopodial and lamellipodial structures in a dose-dependent manner. Cav-1 positive HM-7 clones ceased to express MT4-MMP in their lipid rafts. Comparative proteomic analyses of lipid rafts from cav-1 positive and cav-1 negative cells demonstrated de novo expression of flotillin-1 only on the cells expressing cav-1. Xenografting control cells devoid of cav-1 in nude mice induced development of bigger tumors expressing higher levels of proliferating cell nuclear antigen as compared to mice injected with cells expressing the highest cav-1 levels. We conclude that cav-1 orchestrates and reorganize several proteins in lipid rafts, activities directly associated with reduced tumorigenic and metastatic ability of colon cancer cells.

PPARα and PPARγ protect against HIV-1-induced MMP-9 overexpression via caveolae-associated ERK and Akt signaling

Activation of matrix metalloproteinase-9 (MMP-9) is involved in HIV-1-induced disruption of the blood-brain barrier (BBB). In the present study, we hypothesize that peroxisome proliferator-activated receptor (PPAR)-α or PPARγ can protect against HIV-1-induced MMP-9 overexpression in brain endothelial cells (hCMEC cell line) by attenuating cellular oxidative stress and down-regulation of caveolae-associated redox signaling. Exposure to HIV-1-infected monocytes induced phosphorylation of ERK1/2 and Akt in hCMEC by 2.5- and 3.6-fold, respectively; however, these effects were attenuated by overexpression of PPARα or PPARγ and by silencing of caveolin-1 (cav-1). Coculture of hCMEC with HIV-1-infected monocytes significantly induced MMP-9 promoter and enzyme activity by 3- to 3.5-fold. Promoter mutation studies indicated that SP-1 (g1940t_g1941t) is an essential transcription factor involved in induction of MMP-9 promoter by HIV-1. In addition, HIV-1-stimulated activity of MMP-9 promoter was inhibited by mutation of AP-1 site 2 (c1918t_a1919g) and both (but not individual) NF-κB binding sites (g1389c and g1664c). PPAR overexpression, ERK1/2 or Akt inhibition, and silencing of cav-1 all effectively protected against HIV-1-induced MMP-9 promoter activity, indicating a close relationship among HIV-1-induced cerebrovascular toxicity, redox-regulated mechanisms, and functional caveolae. Such a link was further confirmed in MMP-9-deficient mice exposed to PPARα or PPARγ agonist and injected with the HIV-1-specific protein Tat into cerebral vasculature. Overall, our results indicate that ERK1/2, Akt, and cav-1 are involved in the regulatory mechanisms of PPAR-mediated protection against HIV-1-induced MMP-9 expression in brain endothelial cells.

Role of phospholipases in fungal fitness, pathogenicity, and drug development - lessons from cryptococcus neoformans

Many pathogenic microbes, including many fungi, produce phospholipases which facilitate survival of the pathogen in vivo, invasion and dissemination throughout the host, expression of virulence traits and evasion of host immune defense mechanisms. These phospholipases are either secreted or produced intracellularly and act by physically disrupting host membranes, and/or by affecting fungal cell signaling and production of immunomodulatory effectors. Many of the secreted phospholipases acquire a glycosylphosphatidylinositol sorting motif to facilitate membrane and/or cell wall association and secretion. This review focuses primarily on the role of two members of the phospholipase enzyme family, phospholipase B (Plb) and phosphatidylinositol (PI)-specific phospholipase C (PI-C/Plc), in fungal pathogenesis and in particular, what has been learnt about their function from studies performed in the model pathogenic yeast, Cryptococcus neoformans. These studies have revealed how Plb has adapted to become an important part of the virulence repertoire of pathogenic fungi and how its secretion is regulated. They have also provided valuable insight into how the intracellular enzyme, Plc1, contributes to fungal fitness and pathogenicity – via a putative role in signal transduction pathways that regulate the production of stress-protecting pigments, polysaccharide capsule, cell wall integrity, and adaptation to growth at host temperature. Finally, this review will address the role fungal phospholipases have played in the development of a new class of antifungal drugs, which mimic their phospholipid substrates.

Lipid rafts and caveolin-1 are required for invadopodia formation and extracellular matrix degradation by human breast cancer cells

Invadopodia are ventral membrane protrusions through which invasive cancer cells degrade the extracellular matrix. They are thought to function in the migration of cancer cells through tissue barriers, which is necessary for cancer invasion and metastasis. Although many protein components of invadopodia have been identified, the organization and the role of membrane lipids in invadopodia are not well understood. In this study, the role of lipid rafts, which are cholesterol-enriched membrane microdomains, in the assembly and function of invadopodia in human breast cancer cells was investigated. Lipid rafts are enriched, internalized, and dynamically trafficked at invadopodia sites. Perturbation of lipid raft formation due to depleting or sequestering membrane cholesterol blocked the invadopodia-mediated degradation of the gelatin matrix. Caveolin-1 (Cav-1), a resident protein of lipid rafts and caveolae, accumulates at invadopodia and colocalizes with the internalized lipid raft membranes. Membrane type 1 matrix metalloproteinase (MT1-MMP), a matrix proteinase associated with invadopodia, is localized at lipid raft-enriched membrane fractions and cotrafficked and colocalized with Cav-1 at invadopodia. The small interfering RNA-mediated silencing of Cav-1 inhibited the invadopodia-mediated and MT1-MMP-dependent degradation of the gelatin matrix. Furthermore, Cav-1 and MT1-MMP are coexpressed in invasive human breast cancer cell lines that have an ability to form invadopodia. These results indicate that invadopodia are the sites where enrichment and trafficking of lipid rafts occur and that Cav-1 is an essential regulator of MT1-MMP function and invadopodia-mediated breast cancer cell invasion.

Rat forming incisor requires a rigorous ECM remodeling modulated by MMP/RECK balance

Reversion-inducing-cysteine-rich protein with Kazal motifs (RECK) is a single membrane-anchored MMP-regulator and regulates matrix metalloproteinases (MMP) 2, 9 and 14. In turn, MMPs are endopeptidases that play a pivotal role in remodeling ECM. In this work, we decided to evaluate expression pattern of RECK in growing rat incisor during, specifically focusing out amelogenesis process. Based on different kinds of ameloblasts, our results showed that RECK expression was conducted by secretory and post-secretory ameloblasts. At the secretory phase, RECK was localized in the infra-nuclear region of the ameloblast, outer epithelium, near blood vessels, and in the stellate reticulum. From the transition to the maturation phases, RECK was strongly expressed by non-epithelial immuno-competent cells (macrophages and/or dendritic-like cells) in the papillary layer. From the transition to the maturation stage, RECK expression was increased. RECK mRNA was amplified by RT-PCR from whole enamel organ. Here, we verified the presence of RECK mRNA during all stages of amelogenesis. These events were governed by ameloblasts and by non-epithelial cells residents in the enamel organ. Concluding, we found differential expression of MMPs-2, -9 and RECK in the different phases of amelogenesis, suggesting that the tissue remodeling is rigorously controlled during dental mineralization.