Tissue inhibitor of metalloproteinase 1 (TIMP-1) may be an autocrine growth factor in scleroderma fibroblasts

Tissue inhibitor of metalloproteinases 1 and 2 directly stimulate the bone-resorbing activity of isolated mature osteoclasts

Tissue inhibitor metalloproteinases 1 (TIMP-1) and 2 have been reported to inhibit bone resorption. However, here, we report the direct action of both TIMP-1 and TIMP-2 on isolated rabbit mature osteoclasts to stimulate their bone-resorbing activity at significantly lower concentrations (approximately ng/ml) than those (approximately microg/ml) required for the inhibition of bone resorption. The cell population used in this study consisted of a mature osteoclast population with >95% purity. TIMP-1 (approximately 50 ng/ml) and TIMP-2 (approximately 8-10 ng/ml) increased the pit area excavated by the isolated mature osteoclasts. The stimulatory effects of TIMPs were abolished by simultaneous addition of anti-TIMP antibodies. At higher concentrations, the stimulation of bone resorption decreased reversely to the control level. The magnitude of the stimulatory effect of TIMP-2 was more than that of TIMP-1. Metalloproteinase inhibitors such as BE16627B and R94138 could not replace TIMPs with respect to the bone-resorbing activity, suggesting that the osteoclast-stimulating activity of TIMPs was independent of the inhibitory activity on matrix metalloproteinases (MMPs). TIMPs stimulated tyrosine phosphorylation of cellular proteins in the isolated mature osteoclasts. Both herbimycin A, an inhibitor of tyrosine kinases, and PD98059 and U0126, inhibitors of mitogen-activated protein kinase (MAPK), completely blocked the TIMP-induced stimulation of osteoclastic bone-resorbing activity. On the plasma membrane of osteoclasts, some TIMP-2-binding proteins were detected by a cross-linking experiment. These findings show that TIMPs directly stimulate the bone-resorbing activity of isolated mature osteoclasts at their physiological concentrations and that the stimulatory action of TIMPs is likely to be independent of their activities as inhibitors of MMPs.

Differential growth regulation in human melanoma cell lines by TIMP-1 and TIMP-2

We investigated the role of tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2 in the growth regulation. Primary (PM-WK and KHm-4), recurrent primary (RPM-EP and RPM-MC), lymph node metastatic (MM-AN, MM-BP and MM-RU), and a visceral metastatic (MM-LH) melanoma cell lines were used. Reverse transcriptase-coupled polymerase chain reaction and Western blotting revealed that all expressed and produced TIMP-1 and TIMP-2 except for PM-WK, which neither expressed nor produced TIMP-1. TIMP-1 and TIMP-2 secretion levels were measured by enzyme-linked immunosorbent assay in supernatants of cells. We found that the TIMP-1 production level was correlated with the cell migration rate. Moreover, TIMP-1 enhanced the cell migration of PM-WK. The growth of the primary melanoma cell lines was stimulated by TIMP-1 and inhibited by TIMP-2. In contrast, the growth of the visceral metastatic melanoma cell line was stimulated by TIMP-2.

Matrix metalloproteinase-9 and tissue inhibitor of metalloproteinase-3 are key regulators of extracellular matrix degradation by mouse embryos

Embryo implantation in humans and rodents is a highly invasive yet tightly controlled process involving extracellular matrix (ECM) degradation. Matrix metalloproteinase 9 (MMP-9) has been implicated as the major facilitator of this ECM degradation. MMP-9 is expressed by the embryo's trophoblast cells, whereas tissue inhibitor of metalloproteinases 3 (TIMP-3) is expressed by the maternal uterine cells immediately adjacent to the trophoblast. We examined the functional roles of MMP-9 and TIMP-3 during in vitro ECM degradation by mouse embryos. Blastocysts were treated with either MMP-9 antisense or sense oligonucleotides and incubated on an ECM gel. The extent of ECM degradation exhibited by the blastocysts due to proteinase secretion was quantified. Embryos exposed to MMP-9 antisense oligonucleotides exhibited reduced ECM-degrading activity as compared with controls, and this reduced activity was correlated with the level of MMP-9 secreted by the embryos. The functional role of TIMP-3 was then examined by incubating blastocysts on an ECM gel that had been impregnated with various amounts of TIMP-3. In a dose-dependent manner, increases in TIMP-3 resulted in a reduction in ECM degradation and were correlated with diminished MMP-9 activity. These results provide important functional evidence that in vitro ECM degradation is regulated by embryo-derived MMP-9 and ECM-derived TIMP-3.

Differential expression of nitric oxide by dermal microvascular endothelial cells from patients with scleroderma

Vascular abnormalities in scleroderma are fundamental to the pathogenesis of this disease. The objective of this study was to characterize dermal microvascular endothelial cells (DMEC) isolated from scleroderma patients with respect to growth and expression of the constitutive form of endothelial nitric oxide synthase (eNOS). DMEC from patients with both systemic sclerosis (SSc) and localized scleroderma (Loc Scl) contained small intact microvascular structures in contrast to single cell isolations obtained from control skin. Immunoaffinity selection on anti-PECAM-1 beads yielded pure populations of DMEC expressing normal markers. While the morphology and initial growth of SSc DMEC closely paralleled control cells, the growth of SSc DMEC decreased with time in culture (doubling time of 3 days vs. 5 days). Expression of ecNOS mRNA was reduced in both Loc Scl and SSc as shown by semi-quantitative RT-PCR (p < 0.001). Western blots showed variable but generally lower ecNOS protein levels and decreased levels of nitrogen oxides in media were found from both SSc and Loc Scl relative to control cells. The results indicate an intrinsic defect in the mechanism of nitric oxide production in DMEC isolated from scleroderma patients and suggest its possible involvement in the pathophysiology of scleroderma.

TIMP-1/MMP-9 imbalance in an EBV-immortalized B lymphocyte cellular model: evidence for TIMP-1 multifunctional properties

Tissue inhibitors of metalloproteinases (TIMPs) were initially described as agents controlling metalloproteinase activity. The purpose of this study was to investigate the expression and the roles of TIMP-1 secreted by Epstein-Barr-virus (EBV)-immortalized B lymphocytes. TIMP-1 was isolated from conditioned medium of interleukin (IL)-1beta stimulated EBV-B lymphocytes; purified TIMP-1 was identified by mass spectrometry and immunochemistry. TIMP-1-free MMP-9 was quantified after purification by zymography and enzyme-linked immunosorbent assay. EBV-B lymphocyte-secreted TIMP-1 inhibited MMP-9 gelatinolytic activity resulting in decreased B-cell transmigration as measured in vitro. The release of huge amounts of TIMP-1 in proportion to MMP-9 from B lymphocytes after EBV transformation was shown to be correlated with secretion of IL-10 and dependent on culture time. In contrast, there was little TIMP-1 and almost no IL-10 released from native B cells, suggesting a possible IL-10 mediated autocrine regulation mechanism of TIMP-1 synthesis. The MMP-9/TIMP-1 imbalance observed in the culture medium of EBV-B lymphocytes (TIMP-1>MMP-9) and of native B cells (MMP-9>TIMP-1) is suggestive of a new function for TIMP-1. We propose that TIMP-1 acts as a survival factor controlling B-cell growth and apoptosis through an autocrine regulation process involving IL-10 secreted by EBV-B lymphocytes.

Differential effects of cyclosporin and tacrolimus on the expression of fibrosis-associated genes in isolated glomeruli from renal transplants

BACKGROUND

Chronic allograft nephropathy is characterized by an excessive accumulation of extracellular matrix proteins leading to glomerular and interstitial fibrosis. The aim of this study was to determine the effects of two different immunosuppressive agents (cyclosporin and tacrolimus) on the expression of the genes controlling extracellular matrix deposition in renal transplant glomeruli.

METHODS

Fifty-one renal transplant recipients were randomized to receive immunosuppression with either microemulsion cyclosporin or tacrolimus. Isolated glomeruli were plucked from protocol transplant biopsies performed 1 week, 3 months and 6 months after transplantation. Expression of the genes for collagen IValpha2, collagen III, matrix metalloproteinase 2, tissue inhibitor of metalloproteinases (TIMP) 1 and TIMP-2, tenascin and transforming growth factor (TGF) beta1 was studied by quantitative reverse transcriptase-polymerase chain reaction.

RESULTS

The expression of messenger RNA (mRNA) for collagen III and TIMP-1 was significantly higher in patients receiving cyclosporin therapy than in those having tacrolimus (P < 0.01); this finding was accounted for by differences in the biopsy material at 1 week. A significant difference in collagen III, TIMP-1 and TIMP-2 mRNA expression was also detected between patients depending on the source of renal donor (cadaveric or living). There were no significant differences in the level of glomerular TGF-beta1.

CONCLUSION

The data provide new in vivo evidence that tacrolimus may exert a less fibrogenic influence on transplant glomeruli than cyclosporin.

Matrix metalloproteinases in human melanoma

Cutaneous melanoma is a highly invasive and metastatic tumor. Degradation of basement membranes and extracellular matrix is an essential step in melanoma cell migration, invasion, and metastasis formation. Matrix metalloproteinases and their tissue inhibitors play a crucial role in these complex multistep processes. Melanoma cells may express a number of matrix metalloproteinase family members (MMP-1, MMP-2, MMP-9, MMP-13, and MT1-MMP) as well as their tissue inhibitors (TIMP-1, TIMP-2, and TIMP-3). Numerous studies have examined matrix metalloproteinases, their tissue inhibitors, and the molecules that regulate their expression and/or activation in melanoma cell lines in vitro and in vivo, and in human melanocytic lesions. Recent results have indicated that adhesion molecules such as CD44 and integrin alphavbeta3 are involved in positioning activated matrix metalloproteinase molecules on the cell surface of invasive tumor cells. In this review we evaluate these novel aspects of the role of matrix metalloproteinases and their tissue inhibitors in melanoma progression. We conclude that the balance between levels of activated matrix metalloproteinases and expression levels of their tissue inhibitors, and the coexpression of activated matrix metalloproteinases and adhesion molecules are important factors in determining melanoma cell invasion, tumor growth, and metastasis formation.

Relationship between cell-associated matrix metalloproteinase 9 and psoriatic keratinocyte growth

Primary cultures of psoriatic keratinocytes proliferated at a higher rate and produced lower amounts of matrix metalloproteinase 9 than normal keratinocytes cultured under similar conditions. Sup- plementation of psoriatic keratinocyte cell culture medium with batimastat or the use of a matrix metalloproteinase 9 blocking antibody further stimulated psoriatic keratinocyte growth. An increase in intracellular ceramide level enhanced matrix metalloproteinase 9 production and inhibited cell proliferation in parallel. Whether cells were treated with sphingomyelinase or not, however, conditioned media from psoriatic keratinocytes contained higher levels of tissue inhibitor of metalloproteinase-1 compared with matrix metalloproteinase 9 and secreted only the proenzyme form. Pro-matrix metalloproteinase 9, as well as active matrix metalloproteinase 9, was identified in membrane preparations of psoriatic keratinocytes, and enzyme amounts were greatly elevated following sphingomyelinase action. As (i) tissue inhibitor of metalloproteinase-1 antibody nearly totally abrogated keratinocyte growth and (ii) complexes of tissue inhibitor of metalloproteinase-1 and matrix metalloproteinase 9 were recovered in membrane extracts of sphingomyelinase-treated psoriatic keratinocytes, we postulate that an increased level of cell-associated matrix metalloproteinase 9 might compete for tissue inhibitor of metalloproteinase-1 binding to its receptor. As a consequence, the increased levels of matrix metalloproteinase 9 will decrease keratinocyte growth.

NMR structure of tissue inhibitor of metalloproteinases-1 implicates localized induced fit in recognition of matrix metalloproteinases

A high quality solution structure of the matrix metalloproteinase inhibitory N-terminal domain of recombinant human tissue inhibitor of metalloproteinases-1 (N-TIMP-1) has been determined. For the rigidly packed residues, the average RMSD to the mean structure is 0. 57 A for the backbone atoms and 1.00 A for all heavy atoms. Comparison of the solution structure of free N-TIMP-1 with the crystal structure of TIMP-1 bound to the catalytic domain of MMP-3 ( Gomis-R]uth et al., 1997 ) shows that the structural core of the beta barrel flanked by helices is nearly unchanged by the association with MMP-3, evident from a backbone RMSD of 1.15 A. However, clear differences in the conformation of the MMP-binding ridge of free and MMP-bound TIMP-1 suggest induced fit throughout the ridge. The MMP-dependent conformational changes in the ridge include a dramatic bending of AB loop residues Glu28 through Leu34, moderate hinge bending of the CD-loop about residues Ala65 and Cys70, and modest bending of the Cys1 through Pro6 segment. A large number of interresidue Nuclear Overhauser enhancements (NOEs) augmented by stereospecific assignments, torsion restraints, and dipolar couplings (an average of 18 non-trivial restraints per residue) engender confidence in these structural inferences. A tight cluster of three lysine residues and one arginine residue atop beta-strands A and B, and identical among TIMP sequences, form the heart of a highly conserved electropositive patch that may interact with anionic components of the extracellular matrix.

Serum levels of tissue inhibitor of metalloproteinases 2 in patients with systemic sclerosis

BACKGROUND

The serum tissue inhibitor of metalloproteinases 1 (TIMP-1) level was reported to be a useful indicator of disease activity, especially of lung fibrosis in patients with systemic sclerosis. TIMP-2 is also an important inhibitor of matrix metalloproteinases (MMPs), such as interstitial collagenase, gelatinase, and stromelysin, which control the metabolism of the extracellular matrix. However, serum levels of TIMP-2 in patients with systemic sclerosis (SSc) have not been investigated.

OBJECTIVE

We sought to determine the clinical significance of serum levels of TIMP-2 and MMP-2 in patients with SSc.

METHODS

Serum samples were obtained from 128 patients with SSc (68 with limited cutaneous SSc and 60 with diffuse cutaneous SSc). Twenty-seven serum samples from healthy age- and sex-matched individuals were also examined as controls. The TIMP-2 and MMP-2 levels were determined by means of sandwich enzyme-linked immunosorbent assays.

RESULTS

The serum TIMP-2 levels were elevated in 29 (22.7%) of the 128 patients with SSc and were significantly higher than those of the healthy control subjects. The serum TIMP-2 levels were significantly correlated with the extent of skin sclerosis in the patients with SSc. The incidence of decreased percentage of the diffusing capacity of lung for carbon monoxide (DLCO ) and that of an elevated erythrocyte sedimentation rate were significantly greater in the patients with elevated TIMP-2 levels compared with the patients with normal TIMP-2 levels (P <.05). When these patients were classified into 2 groups by disease activity, TIMP-2 levels were significantly more elevated in the high active group than in those low active group (P <.001). The serum MMP-2 levels of the patients with SSc were not significantly higher than those of the healthy control subjects.

CONCLUSION

These findings suggest that the serum TIMP-2 level is a useful marker of the extent of skin sclerosis and disease activity in patients with SSc. The balance of TIMP-2 and MMP-2 may play an important role in patients with SSc. Furthermore, TIMP-2 may be thought to contribute to the development of disease in patients with SSc.

Comparison of the expression of fibrosis-associated genes in glomeruli after renal transplantation between conventional cadaveric and non-heart-beating donors

BACKGROUND

The main difference between cadaveric heart-beating donors and non-heart-beating donors (NHBDs) is the degree of warm ischaemia to which the kidney is subjected. This study was designed to see if this affected the expression of fibrosis-associated genes in the early period after transplantation.

METHODS

A series of 29 cadaveric and 19 NHBD renal transplants was studied. Patients underwent protocol needle-core renal transplant biopsies at 1 week, 3 months and 6 months after transplantation. At least two individual glomeruli were isolated from each biopsy. Messenger RNA was extracted and genes of interest were amplified by reverse transcriptase-polymerase chain reaction, then quantified in an enzyme-linked immunosorbent assay system.

RESULTS

Delayed graft function was common in NHBD (17 of 19) compared with cadaveric transplants (six of 29) (P < 0.0001). Acute rejection rates were similar. The level of tissue inhibitor of metalloproteinase 1, an inhibitor of extracellular matrix degradation, was higher in kidneys from NHBDs at 1 week (P = 0.02). There were no other statistically significant differences in the expression of fibrosis-associated genes between the two groups.

CONCLUSION

Although the increased ischaemic injury in kidneys retrieved from NHBDs leads to a higher rate of delayed graft function, this does not translate into increased expression of fibrosis-associated genes after the first week.

Tissue inhibitor of metalloproteinases-1 (TIMP-1) binds to the cell surface and translocates to the nucleus of human MCF-7 breast carcinoma cells

To study cellular and subcellular localization of TIMP-1, we constructed a cDNA which would express a chimeric protein, TIMP-1-EGFP, having the enhanced green fluorescent protein of the jelly fish Aequorea victoria fused to the carboxyl-terminus of TIMP-1. Chinese Hamster Ovary (CHO) cells were stably transfected with the TIMP-1-EGFP expressing plasmid. The secreted chimera was processed through the endoplasmic reticulum and Golgi, as was shown by fluorescent confocal microscopy after incubations at temperatures which block processing at the intermediate compartment and the trans-Golgi network. In a co-culture system, secreted TIMP-1-EGFP could be visualized binding to the surface of MCF-7 breast carcinoma cells but not non-neoplastic HBL-100 breast epithelial cells. TIMP-1-EGFP localized to the nucleus of MCF-7 cells after 72 hrs in co-culture. These findings suggest that TIMP-1 may preferentially bind to and be taken up by malignant breast epithelial cells and that TIMP-1 may play a yet unidentified role in nuclear functions.

Tissue inhibitor of metalloprotease (TIMP)-1 and proliferative behaviour of clonal breast cancer cells

In the present paper, we have examined whether human tissue inhibitor of metalloprotease-1 (hTIMP-1) is able to exert a growth factor-like effect on two clonal cell lines (BC-3A and BC-61), isolated from a parental line of human breast carcinoma cells (8701-BC), and endowed with different growth and invasive behaviour 'in vitro' and in nude mouse. The data obtained indicate that only the more tumorigenic clonal cell line (BC-61) is responsive to hTIMP-1 treatment by increasing its proliferative rate in a dose-dependent manner. It was also found that BC-61 cells selectively express a transmembrane protein of about 80 kDa able to bind hTIMP-1 'in vitro' and 'in vivo' with high affinity (Kd of 0.07 +/- 0.004 nM), and that treatment of BC-61 cells with a proliferation-promoting concentration of hTIMP-1 is able to stimulate tyrosine-targeted phosphorylation. The cumulative results obtained strongly support the hypothesis that hTIMP-1, 'classically' regarded as a collagenase inhibitor, may be a crucial element of the extracellular signalling network during breast cancer development by controlling cell growth phenotype in autocrine and paracrine manner, and that intratumoural heterogeneity for the biological response to TIMP-1 may exist within the composite cell population of the primary tumour site.

Serum matrix metalloproteinase-9:Tissue inhibitor of metalloproteinase-1 ratio correlates with steroid responsiveness in moderate to severe asthma

Asthma presents a variable clinical response to corticosteroids (CS). Because CS more likely act on inflammation than on tissue remodeling, the presence of bronchial structural changes in certain asthmatics may explain their limited clinical response to CS. Matrix metalloproteinase-9 (MMP-9) and its inhibitor, tissue inhibitor of metalloproteinase-1 (TIMP-1), are, respectively, involved in tissue inflammatory processes and fibrogenic processes. Previous reports have suggested that MMP-9:TIMP-1 ratio may reflect the balance between these two processes in various diseases. This study evaluated the relation of this ratio and the response to CS in severe asthma. Twenty asthmatics with low baseline FEV1 (59 +/- 4% predicted) and >/= 30 % increase with beta2-agonist were recruited. Serum MMP-9 and TIMP-1 levels were measured and correlated with response to an oral CS trial (methylprenisolone 40 mg/d for 14 d). With oral CS, FEV1 changes (DeltaFEV1) ranged from -15 to +43%. The DeltaFEV1 closely correlated with the MMP-9:TIMP-1 ratios (rho = 0. 79, p = 0.0006). In conclusion, serum MMP-9: TIMP-1 ratio could predict the response of oral CS therapy in asthma. The low MMP-9:TIMP-1 ratio observed in subjects with little or no FEV1 improvement with CS supports the hypothesis that, in these asthmatic subjects, bronchial fibrogenesis predominates over inflammation.

The scarring processes in mucosal tissues after immune injury

OBJECTIVES

An important feature of the healing processes is scar formation which may be necessary for organism survival. If it proceeds to the pathological state, it may impair normal function. The purpose of this review is to focus on some of the factors that may influence this process after immune injury, comparing it in the skin and mucosa.

METHODS

A detailed literature search of peer-reviewed journals was conducted. Studies reported in all languages considered relevant and important were used, including humans, animals, and tissue culture.

RESULTS

Analysis of the data indicate that the scarring process is mainly dependent on (1) the type of the lesion, (2) the cause and duration of injury, and (3) the tissue involved and its microenvironment. Equally important is the large spectrum and heterogenicity in the biological activity of fibroblasts and their role in scar formation.

CONCLUSIONS

The process of scar formation is complex and multistep process and is affected and influenced by local and systemic factors. Although it appears irreversible, there are pharmacological agents available, and under investigation, that may minimize its detrimental effects.

Cell cycle-associated accumulation of tissue inhibitor of metalloproteinases-1 (TIMP-1) in the nuclei of human gingival fibroblasts

We first confirmed an earlier immunohistochemical study showing that immunoreactive TIMP-1-like protein accumulated in the nuclei of human gingival fibroblasts (Gin-1 cells), reaching a maximum in the S phase of the cell cycle (Li, H., Nishio, K., Yamashita, K., Hayakawa, T. and Hoshino, T. (1995). Nagoya J. Med. Sci. 58, 133–142). Then we isolated this protein from a nuclear extract of Gin-1 cells and demonstrated it to be identical to human recombinant TIMP-1 by western blotting, by a sandwich enzyme immunoassay for TIMP-1 and by an assay for matrix metalloproteinase inhibition. The amount of TIMP-1 in the cytosolic fraction of quiescent Gin-1 cells after stimulation by fetal calf serum increased continuously for 48 hours, whereas that in the nuclear extract showed a maximum at 24 hours (S phase) and significantly decreased thereafter. Gin-1 cells expressed mRNAs for both TIMP-2 and TIMP-3 together with mRNA for TIMP-1. However, neither TIMP-2 nor TIMP-3 proteins seemed to accumulate in the nuclei of Gin-1 cells. These facts strongly suggest that TIMP-1 accumulates specifically in the nuclei of Gin-1 cells in a cell cycle-dependent manner.

Activation of tissue inhibitor of metalloproteinases-3 (TIMP-3) mRNA expression in scleroderma skin fibroblasts

Excessive accumulation of fibrillar collagens is a hallmark of the cutaneous fibrosis in both systemic and localized scleroderma. Turnover of the collagenous extracellular matrix is dependent on the balance between collagenolytic matrix metalloproteinases and their specific inhibitors. We have examined the expression of the novel, matrix associated tissue inhibitor of metalloproteinases-3 (TIMP-3) in normal and scleroderma skin fibroblasts in culture and in vivo. The levels of TIMP-3 mRNA were elevated up to 2.5-fold in five of seven systemic sclerosis fibroblast strains, whereas TIMP-1 mRNA expression was elevated up to 1.8-fold in two and TIMP-2 mRNA expression up to 1.8-fold in two systemic sclerosis strains. Using in situ hybridization, TIMP-3 mRNA was detected in seven of 12 localized scleroderma skin samples, specifically in fibroblasts within fibrotic collagen fibers or in the vicinity of inflammatory cells. TIMP-1 mRNA was detected in three of eight scleroderma skin samples in fibroblasts adjacent to inflammatory cells. The expression of TIMP-3 mRNA by systemic sclerosis and normal skin fibroblasts was enhanced to a similar extent (by 8.6- and 8.1-fold, respectively) by transforming growth factor-beta, and suppressed down to 34 and 54%, respectively, by tumor necrosis factor-alpha. Specific activation of TIMP-3 gene expression in scleroderma skin fibroblasts in culture and in vivo suggests a role for TIMP-3 in the pathogenesis of dermal fibrosis via inhibition of turnover of fibrotic dermal extracellular matrix, possibly due to upregulation of TIMP-3 expression by transforming growth factor-beta.

The pathogenesis of cutaneous fibrosis

Cutaneous fibrosis is an integral component of a variety of human disorders including keloids, hypertrophic scar, and most notably, scleroderma. Each has its own etiology and unique clinical characteristics, but all involve the dysregulation of connective tissue metabolism, in particular, the activation of dermal fibroblasts. In this review, we examine various molecular events in scleroderma that may lead to fibroblast activation, and propose a new model to explain the persistence of such activation by scleroderma fibroblasts in the apparent absence of exogenous stimuli.

Recombinant TIMP-1 and -2 enhance the proliferation of rabbit corneal epithelial cells in vitro and the spreading of rabbit corneal epithelium in situ

PURPOSE

The repair of the corneal epithelium is modulated by matrix metalloproteinases. The present study examined the effects of recombinant (r-) tissue inhibitors of metalloproteinases-1 and -2 (TIMP-1 and -2) on the proliferation of cultured epithelial cells from rabbit cornea, and on the spreading of a sheet of squamous epithelium of rabbit cornea placed in an organ culture system.

METHODS

DNA synthesis of the cells, with or without r-TIMPs, was determined by an immunoassay for BrdU incorporation. Cell proliferation was assayed by measuring MTT mitochondrial activity. Epithelial spreading was evaluated by culturing small corneal blocks for 24 h in the presence or absence of each agent. Cryosections were prepared and the epithelial growth on the cut stromal surface was measured.

RESULTS

Each agent, r-TIMP-1 (at 50 and 100 ng/ml) and r-TIMP-2 (at 50 ng/ml) significantly enhanced the DNA synthesis and MTT activity of the corneal epithelial cells in vitro. Relative to the untreated control cells, DNA synthesis was increased 2.4-fold by r-TIMP-1 and 2.3-fold by r-TIMP-2. r-TIMP-1 (at 100 and 200 ng/ml) and r-TIMP-2 (at 10 and 50 ng/ml) each significantly enhanced the spreading of the corneal epithelium. Relative to the untreated control tissue, spreading of the epithelial sheet was increased 1.7-fold by r-TIMP-1 and 1.4-fold by r-TIMP-2. Higher concentrations of r-TIMP-1 and r-TIMP-2 did not further enhance either the DNA synthesis of the cultured cells or the spreading of the epithelium.

CONCLUSIONS

Exogenous TIMPs enhanced the spreading of the corneal epithelium and proliferation of cultured corneal epithelial cells. Findings suggest that endogenous TIMPs may influence the healing of corneal epithelium in vivo.