Involvement of premacular mast cells in the pathogenesis of macular diseases.

We previously reported on the elevated intravitreal activities of tryptase and chymase in association with idiopathic epiretinal membrane (ERM) and idiopathic macular hole (MH). In this present study, we investigated the potential intraocular production of these serine proteases, and measured and compared tryptase and chymase activities in the vitreous body and serum in ERM, MH, proliferative diabetic retinopathy (PDR), and rhegmatogenous retinal detachment (RRD) patients. In addition, nuclear staining with hematoxylin and eosin (H&E) and mast-cell staining with toluidine blue were performed on samples of the vitreous core and bursa premacularis (BPM) of MH. We also performed immunostaining on the above two regions of vitreous samples for MH with anti-tryptase antibody, anti-chymase antibody, anti-podoplanin antibody, anti-lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1) antibody, and anti-fibroblast antibody. Moreover, we performed immunostaining with anti-tryptase antibody and anti-chymase antibody on ERMs collected intraoperatively. Tryptase activity in the vitreous body was significantly higher in ERM and MH than in PDR. However, no significant differences were observed in the tryptase activity in the serum among these four diseases. Chymase activity in the vitreous body was significantly higher in MH than in the other three diseases, yet chymase activity in the serum was below detection limit in any of the diseases. Nuclear staining with H&E revealed an abundance of nuclei in the BPM region, but few in the surrounding area. Mast-cell staining with toluidine blue revealed that the BPM showed metachromatic staining. In immunostaining with anti-fibroblasts antibody, anti-tryptase antibody, anti-chymase antibody, anti-podoplanin antibody, and anti-LYVE-1 antibody, the BPM stained more strongly than the vitreous core. Tryptase and chymase-positive cells were also observed in ERM. These findings revealed that the presence of mast cells in the BPM potentially represent the source of these serine proteases. Moreover, the BPM, as a lymphatic tissue, may play an important role in the pathogenesis of macular disease.

Extracellular SOD and VEGF are increased in vitreous bodies from proliferative diabetic retinopathy patients.

PURPOSE: To evaluate the relationship between vascular endothelial growth factor (VEGF) and extracellular superoxide dismutase (EC-SOD) in vitreous body and serum in patients with proliferative diabetic retinopathy (PDR), and investigate the role of EC-SOD in PDR by evaluating its angiostatic effect, using an in vitro angiogenesis model. To investigate the role of EC-SOD in PDR by evaluating its angiostatic effect, using an in vitro angiogenesis model. METHODS: EC-SOD and VEGF concentrations in vitreous and serum samples from PDR and macular hole (MH) were measured by ELISA. The effects of EC-SOD on VEGF-induced proliferation, migration, and tube formation were evaluated using human umbilical vein endothelial cells (HUVECs). Moreover, the effects of EC-SOD on VEGF-induced proliferation and migration were evaluated in HUVECs and primary normal human retinal microvascular endothelial cells. RESULTS: Intravitreal concentrations of EC-SOD were significantly higher (p<0.01) in PDR (58.0+/-23.8 ng/ml, mean+/-SD) than in MH (29.3+/-6.6 ng/ml). Intravitreal concentrations of VEGF were dramatically higher (p<0.01) in PDR (798.2+/-882.7 pg/ml) than in MH (17.7+/-15.5 pg/ml). The serum concentrations of EC-SOD and VEGF did not differ between the two patient groups. The vitreous concentrations of VEGF correlated with those of EC-SOD in all patients (rs=0.61, p<0.001). In HUVECs, EC-SOD at 100 ng/ml significantly suppressed VEGF-induced proliferation and tube formation, but not VEGF-induced migration. CONCLUSIONS: EC-SOD was increased together with VEGF in the vitreous body from PDR patients, suggesting that EC-SOD may play a pivotal role in the pathogenesis of angiogenesis.

Effect of retinal laser photocoagulation on the activity of metalloproteinases and the alpha(2)-macroglobulin proteolytic state in the vitreous of eyes with proliferative diabetic retinopathy.

Panretinal photocoagulation (PRP) reduces the incidence of severe visual loss in proliferative diabetic retinopathy (PDR). The aim of the study was to determine the effect of PRP on the activity of matrix metalloproteinase-2 (MMP-2) and MMP-9, and also on the alpha(2)-Macroglobulin (alpha(2)M) proteolytic state in the vitreous of eyes with PDR. Vitreous samples were obtained from patients undergoing vitrectomy for the treatment of retinal diseases: 17 with PDR and eight with idiopathic macular hole (MH). Qualitative evaluation of the MMP-2 and MMP-9 activation status was performed by gelatin zymography and quantitative assay was carried out for vitreous total protein content and alpha(2)M. The proteolytic state of alpha(2)M was evaluated by Western blotting. Although all vitreous samples contained proMMP-2, increased proMMP-9 and active MMP-9 were detected in PDR samples without PRP. In addition, after PRP the proMMP-9 activity was significantly decreased, whereas the proMMP-2 activity was not affected. Enhanced total protein and alpha(2)M concentrations were observed in all vitreous samples from PDR patients with and without previous PRP compared with samples from patients with MH. However, a differential proteolytic state of alpha(2)M, expressed as 180/85-90kDa ratio, was detected among PDR patients with and without PRP treatment. Whereas a low 180/85-90kDa ratio of alpha(2)M in vitreous of PDR patients without PRP was observed, a high proportion of 180kDa subunit was principally detected in PDR with PRP. These results demonstrate that PDR occurs with an enhanced activity of MMP-9 and activation of alpha(2)M by proteinases, which is reversed after PRP. In addition, we suggest that alpha(2)M plays a key role in the control and regulation of the ocular neovascularization involved in the pathogenesis of ischemic retinal diseases such as PDR.

Correlation between angiotensin-converting enzyme, vascular endothelial growth factor, and matrix metalloproteinase-9 in the vitreous of eyes with diabetic retinopathy.

PURPOSE: To investigate the involvement of angiotensin-converting enzyme (ACE) with angiogenic factors, vascular endothelial growth factor (VEGF), and matrix metalloproteinase (MMP)-9 in the vitreous of eyes with proliferative diabetic retinopathy (PDR). DESIGN: Observational case series. METHODS: Angiotensin-converting enzyme activity in the vitreous was measured by using a synthetic substrate for ACE. VEGF and MMP-9 concentrations were determined by enzyme-linked immunosorbent assay. RESULTS: Vitreous ACE activity was significantly higher in eyes with PDR (1.4 +/- 1.3 mU/ml) than in eyes with macular holes (0.22 +/- 0.11 mU/ml). Vitreous VEGF concentration in the eyes with PDR (1067 +/- 1076 pg/ml) was significantly higher than in eyes with macular holes (34 +/- 5.5 pg/ml). Vitreous MMP-9 concentration was also significantly higher in eyes with PDR (7.5 +/- 3.8 ng/ml) than in eyes with macular holes (4.2 +/- 1.4 ng/ml). Significant correlations between ACE and VEGF (P < .01) and between ACE and MMP-9 (P < .01) were observed in the vitreous of eyes with PDR. CONCLUSIONS: Angiotensin-converting enzyme was significantly correlated with angiogenic factors, VEGF and MMP-9, in the vitreous of eyes with PDR.

Measurement of activities in two different angiotensin II generating systems, chymase and angiotensin-converting enzyme, in the vitreous fluid of vitreoretinal diseases: a possible involvement of chymase in the pathogenesis of macular hole patients.

PURPOSE: To investigate possible involvement of chymase and angiotensin-converting enzyme (ACE) in the pathogenesis of vitreoretinal diseases, both of which are related to the production of angiotensin II. METHODS: We measured chymase and ACE activities in the vitreous in the 54 affected eyes of 54 patients who had undergone vitreous surgery for idiopathic macular holes (MH, n = 14), proliferative diabetic retinopathy (PDR, n = 14), idiopathic epiretinal membranes (ERM, n = 13), and rhegmatogenous retinal detachment (RRD, n = 13). RESULTS: Chymase activities in the vitreous from patients with MH, PDR, ERM, and RRD were 1.87 +/- 0.53, 0.06 +/- 0.04, 0.40 +/- 0.12, and 0.08 +/- 0.03 (mean +/- SE) mU/mg protein, respectively, and ACE activities in the vitreous humor were 0.18 +/- 0.09, 0.30 +/- 0.07, 0.01 +/- 0.01, and 0.03 +/- 0.02 (mean +/- SE) mU/mg protein, respectively. Chymase activity was significantly elevated in MH among these diseases (p < 0.01, Scheffe), and ACE was significantly activated in PDR compared to ERM and RRD (p < 0.05, Scheffe). CONCLUSIONS: Our results suggest that two different angiotensin II generating systems are activated in human vitreous humor; an increased activity of chymase may play a possible role in the formation of macular holes.

[The pathogenesis of vitreoretinal diseases from the standpoint of molecular biology].

It is important to study the pathogenesis in vitreoretinal diseases to develop new medical therapy. We investigated the molecular mechanisms underlying the genesis of idiopathic macular hole, exudative age-related macular degeneration (AMD), and diabetic retinopathy. We observed high levels of chymase and tryptase activity in the vitreous humor of patients with idiopathic macular hole. This activity was significantly higher than in other vitreoretinal diseases. Immunohistochemical study using monkey eyes showed the possibility that Müller cells in foveal lesions have properties similar to retinal stem cells. Intravitreal injection of chymase induced apoptosis of foveal retinal cells and fibrous change of vitreoretinal interface in the macular area. Biochemical study using cultured human Müller cells revealed that chymase caused the inhibition of growth and the induction of apoptosis in dedifferentiated Müller cells treated with basic fibroblast growth factor (bFGF). These findings show that increased production of chymase and tryptase in mast cells could be related to the pathogenesis of idiopathic macular hole. Oxidative stress and arterosclerosis may be the major causes of exudative AMD. Paraoxonase (PON) is a polymorphic protein known to prevent oxidation of low-density lipoprotein (LDL). We analyzed PON genotypes and found that two types of polymorphism were significantly different between patients with AMD and control subjects. We also investigated serum oxidized low-density lipoprotein(oxLDL) levels, PON activity, and extracellular superoxide dismutase(EC-SOD) levels. All these factors were significantly higher in patients with AMD than in controls. Titers of IgA and IgG antibodies against chlamydia pneumoniae in the serum of AMD patients were also significantly higher than in controls. These results indicate that genetic factors related to PON polymorphisms, vascular damage caused by increment of serum oxLDL and malfunction of EC-SOD, and chronic inflammation provoked by clamydia pneumoniae infection may be involved in the pathogenesis of AMD. Excess accumulation of advanced glycation end products(AGEs) has a causative role in the development of diabetic complications. We determined the concentrations of three AGEs (pentosidine, carboxy-methyllysine, and crossline) and two cytokines (VEGF, IL-6) using ELISA. The levels of the three AGEs and two cytokines in the vitreous of patients with proliferative diabetic retinopathy(PDR) were significantly higher than in controls. The concentrations of VEGF and IL-6 were strongly correlated with the level of these AGEs. Cultured human Müller cells expressed both VEGF and IL-6 mRNA and these expressions were augmented after the treatment of AGEs, while also acting as photosensitizers and accelerating the degradation of hyaluronic acid in vitro. AGEs may consequently play an important role in the pathogenesis of diabetic retinopathy by inducing the production of VEGF and IL-6 in retinal Müller cells and the acceleration of vitreous liquefaction.

Matrix metalloproteinases in human diabetic and nondiabetic vitreous.

PURPOSE: To compare matrix metalloproteinase (MMP) activities in human vitreous samples from patients with diabetic retinopathy (DR) and other vitreoretinal diseases, and to investigate the factors influencing the MMP activities in human DR vitreous samples. METHODS: Thirty-one diabetic and 17 nondiabetic vitreous samples (from nine patients with macular holes and eight patients with epiretinal membranes) were examined. Samples collected at the time of pars plana vitrectomy were subjected to substrate zymography to conduct a quantitative analysis of MMP activity. Immunoblotting against antihuman MMP-1, 2, and 9 was performed to identify MMP in vitreous samples. The effects of posterior vitreous detachment (PVD), vitreous hemorrhage, proliferative membrane, traction detachment, and cystoid macular edema on MMP activities were investigated. RESULTS: All vitreous samples from both DR and non-DR patients showed a single band at the position of 72 kD, corresponding to MMP-2. Another band at 99 kD, corresponding to MMP-9, was detected significantly more often in DR samples than in non-DR samples: 45.2% and 0%, respectively (P = 0.0007). The number of samples showing a band from MMP-9 was significantly higher in partial PVD samples than in complete PVD samples: 66.7% and 15.4%, respectively (P = 0.001). CONCLUSION: The results indicated that MMP-9 may be involved in DR and that partial PVD may be related to the MMP-9 activity in DR.