- Email: [email protected]
Postoperative fluctuations of tissue plasminogen activator (t-PA) in aqueous humor of pseudophakes
articles Postoperative fluctuations of tissue plasminogen activator (t-PA) in aqueous humor of pseudophakes Fumiaki Yoshitomi, M.D., Ph.D., Eiichiro Utsumi, M.D., Ph.D., Masayasll Hayashi, M.D., Ph.D., Minoru Futenma, M.D., Ph.D., Ritsuko Yamada, M.D., Ph.D., Seiichi Yamada, M.D., Ph.D.
B'
;\
W studied the quantitativ' flu ctuations of ti ssu' plao,mil o~ 'n a ti ator (t-P,\) a ti it} an I a tigen in aqu 'OU'\ h1ll10r b ,for and aft'r c tt'a 'apsula atamet e trll ,tion and pol, (m ,th}1 III ,tha 'J Int·) posterior 'hamb 'r lens implantatim. h t-P\ a ti it 1· ,I \\as m ·a,>ur·d b solid ph as • hioimmunoas ... a ming I ono 'Ional antihod against an pit ope apart frol the a -Ii • sit • of t-P , and th . anlig'n b} ... I 'A. In out'} ali 'nts th' 111 'an pr 'op 'l'ath · 1, 'loft- '\ II ,ti,i t \ as ' 0.0664 ± 0,0-172 I Iml (Il'an ± D) and 0 th · 1 ti~ 'n, 0.175 _ 0.02-1 ng/n 1. h t-P'\ a ·tivit, I ,I in UC1U 'OU . humor \\-as ma k · 11 cI r as d on th fir ... t poo,top ·rativ cia, (0.0042 ± 0.00:17 1 1m I), I' '0"1' ,d on th c nnd da (O, 040:l ± 0.0251 Iml), and th 'n pro~r'ssh ,I} d· 'reas·d from th fourth to th • s' 'n th cia s. Ihe t-I> antigen I, el if H(jU 'ous humol' in 'r a, d on the fit st (O.:Hi) ± 0.108 ng/ml) Hnd 'ie 'oml (OAO:l ± 0.251 nglml) postop 'rati e da.·s and ~raduall } d cr ased from the fOUl th to s 'cnth cia s. nd'l' th· intr, cam ')'al ondilion o/'the fihrinol lie sst 'm, n..tolls fn ton , ',~., II ·dollS inOa 11m tion Qt' " 'nts afC· ,ti l~ th ' balan' , of c()a~IIIUli()n and fibrinol} .. is , nUl} induee th ' d ·crea ... ' or d pI ·lion ) t-I) 'ti it}, foil , . ,eI h th pupillar fibrin m 'mhnm ' formation. , 7, m~~ 'sl th,lt t fibril ous fluctualions of I-I)" ,cthit in HClu ous humor ma, a m mhran formation mer the I) surru(' '. .
r,
orels: (' tr,1 '(\p<;III:11 cataract (' tra 'lioll , llIolloclollal alltiho(h pol) (1llt'th) I m · th,H.'1 \ hltp ), POSlt'1 iOl ·h,Il11IH'r l ' l\s implantatio1l tissu{' phlsllllllog 'I ,Iclh .ltOI' (t- P\)
Fibrinous membrane formation involving the poly(methyl methacrylate) (PMMA) intraocular lens surface, lens capsule, and iris is among the postoperative complications experienced by the Japanese patient after extracapsular cataract extraction (ECCE) and intraocular lens (IOL) implantation. Investigators have reported this problem and speculated on its pathogenesis. l The aim of this report is to demonstrate the effect of the fibrinolytic system in
the anterior chamber and to elucidate a possible mechanism of this problem.
MATERIALS AND METHODS Samples of the aqueous humor were obtained at 11:00 AM-12:00 noon from eyes with a cataract that were having or bad had ECCE and PM MA posterior chamber lens implantation.
From the Department of Ophthalmology. General Shinkawabashi Hospital, KllIUlgawa, Risshou·kouseikai Hospital. Tokyo (Yoshitomi. Vtsumi. Hayashi . Futenma) and the Department of LlIhoratory Medicine. St. Marianna Vni.versity School of Medicine. Ktmllgawa (R. Yamada. S, Yamnda). Reprint requests to Fumiaki Yoshitomi. M.D., Ph, D .. Department of Ophthlllmolog!/. General SlJinkfltvahashi Hospital. 1·15. Shinkawa Street. Knwasaki·ku . Ktlwllsllki City, Ktmagawa. JapaH.
J CATARACT
REFRACT SURG-VOL 17, SEPTEMBER 1991
543
The pupils were dilated with topical tropicamide (0.5%), phenyl epinephrine (5.0%), and indomethacin (0.5%). After retrobulbar anesthesia and akinesia, an 11 mm to 12 mm fornix-based conjunctival flap was made. A four-plane incision was made at the corneoscleral border following Dobree's method. A preoperative aqueous humor volume of 1,150 I.d to 2000 JLI was aspirated with a 27 -gauge disposable needle. After the anterior chamber was filled with viscoelastic material, a can-opener anterior capsulotomy, lens nucleus delivery, and lens cortex aspiration were performed. The posterior chamber IOL (PMMA, modified C-Ioop) was implanted in the capsular bag. Topical indomethacin was given 30 minutes prior to and immediately before operating. The aqueous humor samples on the postoperative days were obtained at 11:00 AM12:00 noon by paracentesis with a 27-gauge needle. There were 32 preoperative samples. Postoperatively, eight were taken the first day, six on the second day, six on the fourth day, eight on the sixth day, and seven on the seventh day. Different patients were sampled each time. Venous blood samples were collected from 31 patients at 11:00 AM-12:00 noon without using venous occlusion. The patients' ages ranged from 55 to 93 years. The tissue plasminogen (t-PA) activity was measured using a modification of bioimmunoassay of t-PA described by Watanabe et al. 2 A dipstick coated with a monoclonal antibody (SP-322) against an epitope apart from the active site of t- PA was dipped into the sample and incubated at room temperature fe)r ten minutes. After washing with tris-HCI buffer (pH 7.4) containing 0.05% of polyoxyethylene sorbitan monolaurate, a piece of the dipstick was put into a microtiterplate. Two hundred microliters of 20 mM tris-HCI buffer containing 0.45 mM S-2251, 120 JLglml of BrCN-fibrinogen, and 0.042 JLM lysplasminogen were added as substrate solution. After incubating for 17 hours, the dipstick was removed and the color developed in each well was read as optical density at 40.5 nm. The t-PA activity was calculated by a standard curve. The rest of the samples were centrifuged, 3000 rpm, at 4DC for 30 minutes and the supernatant was stored at - 80DC for the measurement of t-PA antigen. The t- PA antigen was determined by enzymelinked immunosorbent assay3 using the same monoclonal antibody (SP-322) against a single chain of recombinant t-PA. The endothelial cell numbers and area of 1.3 corneas of eyes with a cataract were measured using a specular microscope (Konan-Keeler) before the surgery. Preoperative levels of t- PA activity and t- PA .544
J CATARACT
antigen in blood and aqueous humor from patients before cataract extraction and IOL implantation were measured, analyzed, and age correlated. Correlation analyses were performed between t-PA activity or t- PA antigen levels in blood and in aqueous humor, and between t-PA activity or t-PA antigen levels in aqueous humor and endothelial cell density or corneal area. These coefficients of correlation were tested for significant departure from zero using the t-test. Differences of t-PA activity and t- PA antigen levels in blood or aqueous humor preoperatively and at the seventh postoperative d'lY were tested with the F-test (one way analysis 'of variance).
RESULTS The t- PA activity level in aqueous humor from the 32 preoperative patients was 0.0664 ± 0.0472 IVlml (0.166 ± 0.119 nglml) (mean ± SD). No correlation between the t-PA activity level and age was observed. In blood, the t-PA activity level sampled from 31 cataract patients whose ages ranged from 55 to 93 years was 0.141 ± 0.009 IVlml (0.353 ± 0.021 nglml) and showed no Significant correlation with that in aqueous humor (r: 0.217, not significant) or age. The t-PA activity level in aqueous humor decreased on the first postoperative day (0.0042 ± 0.0037 IVlml), followed by prominent recovery on the second day (0.0403 ± 0.0251 IVlml). The t-PA activity level was significantly decreased on the fourth (0.004 IVlml), sixth (0.0122 ± 0.009 IVlml), and seventh (0.0228 ± 0.0186 IVlml) days (P<.Ol) (Figure 1).
. ... .... •• .... ** I
•
."
•
»
n
..... < .....
:.: 5
... ><
•
•
*
o~
c:
....
!ol
••
•• 0
2
4
6
7
hospital day
Fig. 1.
(Yoshitomi) Tissue plasminogen activator activity in aqueous humor obtained from patients with IOLs. The average value of t-PA activity levels on each day showed a significant difference (P<.Ol) by the one way analysis of variance.
REFHACT SUHG-VOL 17, SEPTEMBER 1991
. .. .....
•
I
:
•
0.5
::J
ID ::J
..• ::J
-
"-
, 6
hosp i tal day
Fig. 2.
(Yoshitomi) Tissue plasminogen activator antigen in aqueous humor obtained from IOL implanted patients. The average value oft-PA antigen levels on each day showed a significant difference (P<.Ol).
The mean preoperative level of t-PA antigen in aqueous humor was 0.176 ± 0.024 ng/ml. No correlation between the t-PA antigen level and age was observed. The t-PA antigen preoperative blood level was 4.33 ± 2.05 ng/ml and showed no significant correlation with that in aqueous humor (r: 0.127, ns) or age. The aqueous humor t-PA antigen level increased on the first (0.366 ± 0.108 ng/ml) and second (0.403 ± 0.251 ng/ml) postoperative days and then decreased on the fourth (0.286 ± 0.091 ng/ml), sixth (0.155 ± 0.130 ng/ml), and seventh (0.125 ± 0.070 ng/ml) days (Figure 2). The corneal endothelial cell density and cell area in 13 preoperative patients were 3,247 ± 259 cells/ mm 2 and 286 ± 89 /-Lm2, respectively. No correlation between these values and t- PA activity (r: 0.239, ns, r: 0.270, ns) or antigen (r: 0, ns) in the aqueous humor was observed.
DISCUSSION Fibrinous membrane formation involving the PMMA-IOL surface, lens capsule, and iris is a significant, serious postoperative complication in Japanese eyes after cataract and 10L surgery.] It is frequently an antecedent of other complications such as pupil irregularity, iris capture, and pupillary block. Investigators have reported this postoperative problem but until recently little about its pathogenesis was known. We determined the levels of t- PA activity and t- PA antigen in the aqueous humor obtained from patients before and after cataract and 10L surgery to investigate the fibrinolytic system in the anterior chamber and to elucidate the mechanism of fibrin formation on the 10L surface. In preoperative eyes, we detected 0.0664 IU/ml (0.166 nglml) of funcJ CATARACT
tionally active t-PA and 0.176 nglml oft-PA antigen in aqueous humor. No correlation between t- PA activity or t- PA antigen levels in aqueous humor and those in blood was observed. 4 ,5 We postulate that functionally active t- PA in the static aqueous humor is secreted from intraocular tissues such as corneal endothelial cells 6 -s and trabecular cells. 9 Therefore, the corneal endothelial cells not only maintain the transparency of the cornea, but may maintain homeostasis of the aqueous humor through the secretion of various bioactive substances such as t-PA. The inverse relationship between the t-PA enzymatic activity and the level of t- PA antigen that we found OIl the first postoperative day is puzzling. We consider that a marked decrease of t- PA activity and an increase of t-PA antigen on the first postoperative day reflects an intracameral hypercoagulable state following the inflammation stimulated by surgical trauma, leading to disruption of the blood-aqueous barrier and influx of vascular plasminogen activator inhibitor (PAl-I). The t-PA activity is influenced by multiple factors, such as specific t- PA inhibitor (PAl-I) and nonspecific inhibitors transported from plasma.]O, 11 Postoperatively the t-PA activity and t-PA antigen seemed to be altered under the regulation of intracameral PAl from plasma as well as the aqueous humor. On the second postoperative day the t-PA activity level increased to approach preoperative values, and antigen significantly increased following the production of secondary aqueous humor. On the fourth, sixth, and seventh postoperative days, the t-PA activity and antigen gradually decreased. This imbalance between coagulation and fibrinolysis, triggered by the activation of the intrinsic pathway of blood coagulation on the PMMA-IOL surface, produced the fibrin membrane formation. Figure 3 is a hypothetical schema of movement of t- PA and PAl under the conditions of blood-aqueous barrier disruption in the anterior chamber. The t-PA released from corneal endothelial cells and the other intraocular tissues have fibrinolytic activity in response to various stimuli in the aqueous humor. The t- PA released from vascular endothelial cells is transported into the anterior chamber because of bloodaqueous barrier disruption. However, we have not performed any experiments to discriminate local t-PA from vascular t- PA. Active t- PA f
REFRACT SURG-VOL 17, SEPTEMBER HJ91
545
Fig. 3.
Vascular .ndoth.lial c.lls
the fourth, sixth, and seventh days. The t-PA antigen showed bi-phasic changes, increasing on the first and second days and decreasing on the fourth, sixth, and seventh days. We also clinically observed the occurrence of fibrinous membrane formation over the IOL surface mainly on the first day and the fourth to seventh days, while new fibrinous membranes did not form on the second day. Under the intracameral conditions of the fibrinolytic system, various factors, e.g., serious inflammation or events affecting the balance of coagulation and fibrinolysis, may easily induce the decrease or depletion of t-PA activity, followed by pupillary fibrin membrane formation. We suggest that fluctuations of t-PA activity in aqueous humor may influence fibrinous membrane formation on the IOL surface. REFERENCES 1. Miyake K, Maekubo K, Miyake Y, Nishi 0. Pupillary fibrin membrane; a frequent early complication after posterior chamber lens implantation in Japan. Ophthalmology 1989; 96: 1228-1233 2. Watanabe S, Sasamata M, Katoh M, et al. t-PA activity assay method in blood sample using a dipstick coated with monoclonal antibody SP-322. Thromb Haemost 1989; 62:95
546
J CATARACT
(Yoshitomi) Hypothetical schema of movement of t-PA and PAl under the conditions of blood aqueous barrier disruption in the ocular chamber. The t-PA released from corneal endothelial cells and the other intraocular structures has fibrinolytic activity in response to various stimuli in the aqueous humor. The t-PA released from vascular endothelial cells is transported into the anterior chamber because of the disrupted bloodaqueous barrier. Activated t-PA forms a complex with PAI-1 and is inactjvated immediately. In this way, t-PA may play a role in preventing synechias from forming on intraocular organs or fibrin deposits adhering to the IOL surface under the regulation of PAI-1 functions.
3. Guesdon JL, Ternynck T, Avrameas S. The use of avidinbiotin interaction in immunoenzymatic techniques. J Histochem Cytochem 1979; 27:1131-1139 4. Yamada R, Yamada S, Nakamura M, et al. Tissue plasminogen activator in human aqueous humor. J Eye (Atarashii Ganka) 1988; 5:1331-1334 5. Tripathi RC, Park JK, Tripathi BJ, Millard CB. Tissue plasminogen activator in human aqueous humor and its possible therapeutic significance. Am J Ophthalmol 1988; 106:719-722 6. Fehrenbacher L, Gospodarowicz D, Shuman MA. Synthesis of plasminogen activator by bovine corneal endothelial cells. Exp Eye Res 1979; 29: 219-228 7. Fukushima M, Nakashima Y, Sueishi K. Thrombin enhances release of tissue plasminogen activator from bovine corneal endothelial cells. Invest Ophthalmol Vis Sci 1989; 30: 1576-1583 8. McDermott ML, Edelhauser HF, Hyndiuk RA, Koenig SB. Tissue plasminogen activator and the corneal endothelium. Am J Ophthalmol 1989; 108:91-92 9. Tripathi RC, Park JK, Tripathi BJ, Ts'ao C. Tissue plasminogen activator synthesis by trabecular cells and its implications for fibrinolytic therapy of the eye. Drug Dev Res 1989; 18:245-254 10. van Mourik JA, Lawrence DA, Loskutoff DJ. Purification of an inhibitor of plasminogen activator (antiactivator) synthesized by endothelial cells. J Bioi Chem 1984; 259:14914-14921 11. Kruithof EKO, Tran-Thang C, Ransijn A, Bachmann F. Demonstration of a fast-acting inhibitor of plasminogen activators in human plasma. Blood 1984; 64:907-913
REFRACT SURG-VOL 17, SEPTEMBER 1991
B'
;\
W studied the quantitativ' flu ctuations of ti ssu' plao,mil o~ 'n a ti ator (t-P,\) a ti it} an I a tigen in aqu 'OU'\ h1ll10r b ,for and aft'r c tt'a 'apsula atamet e trll ,tion and pol, (m ,th}1 III ,tha 'J Int·) posterior 'hamb 'r lens implantatim. h t-P\ a ti it 1· ,I \\as m ·a,>ur·d b solid ph as • hioimmunoas ... a ming I ono 'Ional antihod against an pit ope apart frol the a -Ii • sit • of t-P , and th . anlig'n b} ... I 'A. In out'} ali 'nts th' 111 'an pr 'op 'l'ath · 1, 'loft- '\ II ,ti,i t \ as ' 0.0664 ± 0,0-172 I Iml (Il'an ± D) and 0 th · 1 ti~ 'n, 0.175 _ 0.02-1 ng/n 1. h t-P'\ a ·tivit, I ,I in UC1U 'OU . humor \\-as ma k · 11 cI r as d on th fir ... t poo,top ·rativ cia, (0.0042 ± 0.00:17 1 1m I), I' '0"1' ,d on th c nnd da (O, 040:l ± 0.0251 Iml), and th 'n pro~r'ssh ,I} d· 'reas·d from th fourth to th • s' 'n th cia s. Ihe t-I> antigen I, el if H(jU 'ous humol' in 'r a, d on the fit st (O.:Hi) ± 0.108 ng/ml) Hnd 'ie 'oml (OAO:l ± 0.251 nglml) postop 'rati e da.·s and ~raduall } d cr ased from the fOUl th to s 'cnth cia s. nd'l' th· intr, cam ')'al ondilion o/'the fihrinol lie sst 'm, n..tolls fn ton , ',~., II ·dollS inOa 11m tion Qt' " 'nts afC· ,ti l~ th ' balan' , of c()a~IIIUli()n and fibrinol} .. is , nUl} induee th ' d ·crea ... ' or d pI ·lion ) t-I) 'ti it}, foil , . ,eI h th pupillar fibrin m 'mhnm ' formation. , 7, m~~ 'sl th,lt t fibril ous fluctualions of I-I)" ,cthit in HClu ous humor ma, a m mhran formation mer the I) surru(' '. .
r,
orels: (' tr,1 '(\p<;III:11 cataract (' tra 'lioll , llIolloclollal alltiho(h pol) (1llt'th) I m · th,H.'1 \ hltp ), POSlt'1 iOl ·h,Il11IH'r l ' l\s implantatio1l tissu{' phlsllllllog 'I ,Iclh .ltOI' (t- P\)
Fibrinous membrane formation involving the poly(methyl methacrylate) (PMMA) intraocular lens surface, lens capsule, and iris is among the postoperative complications experienced by the Japanese patient after extracapsular cataract extraction (ECCE) and intraocular lens (IOL) implantation. Investigators have reported this problem and speculated on its pathogenesis. l The aim of this report is to demonstrate the effect of the fibrinolytic system in
the anterior chamber and to elucidate a possible mechanism of this problem.
MATERIALS AND METHODS Samples of the aqueous humor were obtained at 11:00 AM-12:00 noon from eyes with a cataract that were having or bad had ECCE and PM MA posterior chamber lens implantation.
From the Department of Ophthalmology. General Shinkawabashi Hospital, KllIUlgawa, Risshou·kouseikai Hospital. Tokyo (Yoshitomi. Vtsumi. Hayashi . Futenma) and the Department of LlIhoratory Medicine. St. Marianna Vni.versity School of Medicine. Ktmllgawa (R. Yamada. S, Yamnda). Reprint requests to Fumiaki Yoshitomi. M.D., Ph, D .. Department of Ophthlllmolog!/. General SlJinkfltvahashi Hospital. 1·15. Shinkawa Street. Knwasaki·ku . Ktlwllsllki City, Ktmagawa. JapaH.
J CATARACT
REFRACT SURG-VOL 17, SEPTEMBER 1991
543
The pupils were dilated with topical tropicamide (0.5%), phenyl epinephrine (5.0%), and indomethacin (0.5%). After retrobulbar anesthesia and akinesia, an 11 mm to 12 mm fornix-based conjunctival flap was made. A four-plane incision was made at the corneoscleral border following Dobree's method. A preoperative aqueous humor volume of 1,150 I.d to 2000 JLI was aspirated with a 27 -gauge disposable needle. After the anterior chamber was filled with viscoelastic material, a can-opener anterior capsulotomy, lens nucleus delivery, and lens cortex aspiration were performed. The posterior chamber IOL (PMMA, modified C-Ioop) was implanted in the capsular bag. Topical indomethacin was given 30 minutes prior to and immediately before operating. The aqueous humor samples on the postoperative days were obtained at 11:00 AM12:00 noon by paracentesis with a 27-gauge needle. There were 32 preoperative samples. Postoperatively, eight were taken the first day, six on the second day, six on the fourth day, eight on the sixth day, and seven on the seventh day. Different patients were sampled each time. Venous blood samples were collected from 31 patients at 11:00 AM-12:00 noon without using venous occlusion. The patients' ages ranged from 55 to 93 years. The tissue plasminogen (t-PA) activity was measured using a modification of bioimmunoassay of t-PA described by Watanabe et al. 2 A dipstick coated with a monoclonal antibody (SP-322) against an epitope apart from the active site of t- PA was dipped into the sample and incubated at room temperature fe)r ten minutes. After washing with tris-HCI buffer (pH 7.4) containing 0.05% of polyoxyethylene sorbitan monolaurate, a piece of the dipstick was put into a microtiterplate. Two hundred microliters of 20 mM tris-HCI buffer containing 0.45 mM S-2251, 120 JLglml of BrCN-fibrinogen, and 0.042 JLM lysplasminogen were added as substrate solution. After incubating for 17 hours, the dipstick was removed and the color developed in each well was read as optical density at 40.5 nm. The t-PA activity was calculated by a standard curve. The rest of the samples were centrifuged, 3000 rpm, at 4DC for 30 minutes and the supernatant was stored at - 80DC for the measurement of t-PA antigen. The t- PA antigen was determined by enzymelinked immunosorbent assay3 using the same monoclonal antibody (SP-322) against a single chain of recombinant t-PA. The endothelial cell numbers and area of 1.3 corneas of eyes with a cataract were measured using a specular microscope (Konan-Keeler) before the surgery. Preoperative levels of t- PA activity and t- PA .544
J CATARACT
antigen in blood and aqueous humor from patients before cataract extraction and IOL implantation were measured, analyzed, and age correlated. Correlation analyses were performed between t-PA activity or t- PA antigen levels in blood and in aqueous humor, and between t-PA activity or t-PA antigen levels in aqueous humor and endothelial cell density or corneal area. These coefficients of correlation were tested for significant departure from zero using the t-test. Differences of t-PA activity and t- PA antigen levels in blood or aqueous humor preoperatively and at the seventh postoperative d'lY were tested with the F-test (one way analysis 'of variance).
RESULTS The t- PA activity level in aqueous humor from the 32 preoperative patients was 0.0664 ± 0.0472 IVlml (0.166 ± 0.119 nglml) (mean ± SD). No correlation between the t-PA activity level and age was observed. In blood, the t-PA activity level sampled from 31 cataract patients whose ages ranged from 55 to 93 years was 0.141 ± 0.009 IVlml (0.353 ± 0.021 nglml) and showed no Significant correlation with that in aqueous humor (r: 0.217, not significant) or age. The t-PA activity level in aqueous humor decreased on the first postoperative day (0.0042 ± 0.0037 IVlml), followed by prominent recovery on the second day (0.0403 ± 0.0251 IVlml). The t-PA activity level was significantly decreased on the fourth (0.004 IVlml), sixth (0.0122 ± 0.009 IVlml), and seventh (0.0228 ± 0.0186 IVlml) days (P<.Ol) (Figure 1).
. ... .... •• .... ** I
•
."
•
»
n
..... < .....
:.: 5
... ><
•
•
*
o~
c:
....
!ol
••
•• 0
2
4
6
7
hospital day
Fig. 1.
(Yoshitomi) Tissue plasminogen activator activity in aqueous humor obtained from patients with IOLs. The average value of t-PA activity levels on each day showed a significant difference (P<.Ol) by the one way analysis of variance.
REFHACT SUHG-VOL 17, SEPTEMBER 1991
. .. .....
•
I
:
•
0.5
::J
ID ::J
..• ::J
-
"-
, 6
hosp i tal day
Fig. 2.
(Yoshitomi) Tissue plasminogen activator antigen in aqueous humor obtained from IOL implanted patients. The average value oft-PA antigen levels on each day showed a significant difference (P<.Ol).
The mean preoperative level of t-PA antigen in aqueous humor was 0.176 ± 0.024 ng/ml. No correlation between the t-PA antigen level and age was observed. The t-PA antigen preoperative blood level was 4.33 ± 2.05 ng/ml and showed no significant correlation with that in aqueous humor (r: 0.127, ns) or age. The aqueous humor t-PA antigen level increased on the first (0.366 ± 0.108 ng/ml) and second (0.403 ± 0.251 ng/ml) postoperative days and then decreased on the fourth (0.286 ± 0.091 ng/ml), sixth (0.155 ± 0.130 ng/ml), and seventh (0.125 ± 0.070 ng/ml) days (Figure 2). The corneal endothelial cell density and cell area in 13 preoperative patients were 3,247 ± 259 cells/ mm 2 and 286 ± 89 /-Lm2, respectively. No correlation between these values and t- PA activity (r: 0.239, ns, r: 0.270, ns) or antigen (r: 0, ns) in the aqueous humor was observed.
DISCUSSION Fibrinous membrane formation involving the PMMA-IOL surface, lens capsule, and iris is a significant, serious postoperative complication in Japanese eyes after cataract and 10L surgery.] It is frequently an antecedent of other complications such as pupil irregularity, iris capture, and pupillary block. Investigators have reported this postoperative problem but until recently little about its pathogenesis was known. We determined the levels of t- PA activity and t- PA antigen in the aqueous humor obtained from patients before and after cataract and 10L surgery to investigate the fibrinolytic system in the anterior chamber and to elucidate the mechanism of fibrin formation on the 10L surface. In preoperative eyes, we detected 0.0664 IU/ml (0.166 nglml) of funcJ CATARACT
tionally active t-PA and 0.176 nglml oft-PA antigen in aqueous humor. No correlation between t- PA activity or t- PA antigen levels in aqueous humor and those in blood was observed. 4 ,5 We postulate that functionally active t- PA in the static aqueous humor is secreted from intraocular tissues such as corneal endothelial cells 6 -s and trabecular cells. 9 Therefore, the corneal endothelial cells not only maintain the transparency of the cornea, but may maintain homeostasis of the aqueous humor through the secretion of various bioactive substances such as t-PA. The inverse relationship between the t-PA enzymatic activity and the level of t- PA antigen that we found OIl the first postoperative day is puzzling. We consider that a marked decrease of t- PA activity and an increase of t-PA antigen on the first postoperative day reflects an intracameral hypercoagulable state following the inflammation stimulated by surgical trauma, leading to disruption of the blood-aqueous barrier and influx of vascular plasminogen activator inhibitor (PAl-I). The t-PA activity is influenced by multiple factors, such as specific t- PA inhibitor (PAl-I) and nonspecific inhibitors transported from plasma.]O, 11 Postoperatively the t-PA activity and t-PA antigen seemed to be altered under the regulation of intracameral PAl from plasma as well as the aqueous humor. On the second postoperative day the t-PA activity level increased to approach preoperative values, and antigen significantly increased following the production of secondary aqueous humor. On the fourth, sixth, and seventh postoperative days, the t-PA activity and antigen gradually decreased. This imbalance between coagulation and fibrinolysis, triggered by the activation of the intrinsic pathway of blood coagulation on the PMMA-IOL surface, produced the fibrin membrane formation. Figure 3 is a hypothetical schema of movement of t- PA and PAl under the conditions of blood-aqueous barrier disruption in the anterior chamber. The t-PA released from corneal endothelial cells and the other intraocular tissues have fibrinolytic activity in response to various stimuli in the aqueous humor. The t- PA released from vascular endothelial cells is transported into the anterior chamber because of bloodaqueous barrier disruption. However, we have not performed any experiments to discriminate local t-PA from vascular t- PA. Active t- PA f
REFRACT SURG-VOL 17, SEPTEMBER HJ91
545
Fig. 3.
Vascular .ndoth.lial c.lls
the fourth, sixth, and seventh days. The t-PA antigen showed bi-phasic changes, increasing on the first and second days and decreasing on the fourth, sixth, and seventh days. We also clinically observed the occurrence of fibrinous membrane formation over the IOL surface mainly on the first day and the fourth to seventh days, while new fibrinous membranes did not form on the second day. Under the intracameral conditions of the fibrinolytic system, various factors, e.g., serious inflammation or events affecting the balance of coagulation and fibrinolysis, may easily induce the decrease or depletion of t-PA activity, followed by pupillary fibrin membrane formation. We suggest that fluctuations of t-PA activity in aqueous humor may influence fibrinous membrane formation on the IOL surface. REFERENCES 1. Miyake K, Maekubo K, Miyake Y, Nishi 0. Pupillary fibrin membrane; a frequent early complication after posterior chamber lens implantation in Japan. Ophthalmology 1989; 96: 1228-1233 2. Watanabe S, Sasamata M, Katoh M, et al. t-PA activity assay method in blood sample using a dipstick coated with monoclonal antibody SP-322. Thromb Haemost 1989; 62:95
546
J CATARACT
(Yoshitomi) Hypothetical schema of movement of t-PA and PAl under the conditions of blood aqueous barrier disruption in the ocular chamber. The t-PA released from corneal endothelial cells and the other intraocular structures has fibrinolytic activity in response to various stimuli in the aqueous humor. The t-PA released from vascular endothelial cells is transported into the anterior chamber because of the disrupted bloodaqueous barrier. Activated t-PA forms a complex with PAI-1 and is inactjvated immediately. In this way, t-PA may play a role in preventing synechias from forming on intraocular organs or fibrin deposits adhering to the IOL surface under the regulation of PAI-1 functions.
3. Guesdon JL, Ternynck T, Avrameas S. The use of avidinbiotin interaction in immunoenzymatic techniques. J Histochem Cytochem 1979; 27:1131-1139 4. Yamada R, Yamada S, Nakamura M, et al. Tissue plasminogen activator in human aqueous humor. J Eye (Atarashii Ganka) 1988; 5:1331-1334 5. Tripathi RC, Park JK, Tripathi BJ, Millard CB. Tissue plasminogen activator in human aqueous humor and its possible therapeutic significance. Am J Ophthalmol 1988; 106:719-722 6. Fehrenbacher L, Gospodarowicz D, Shuman MA. Synthesis of plasminogen activator by bovine corneal endothelial cells. Exp Eye Res 1979; 29: 219-228 7. Fukushima M, Nakashima Y, Sueishi K. Thrombin enhances release of tissue plasminogen activator from bovine corneal endothelial cells. Invest Ophthalmol Vis Sci 1989; 30: 1576-1583 8. McDermott ML, Edelhauser HF, Hyndiuk RA, Koenig SB. Tissue plasminogen activator and the corneal endothelium. Am J Ophthalmol 1989; 108:91-92 9. Tripathi RC, Park JK, Tripathi BJ, Ts'ao C. Tissue plasminogen activator synthesis by trabecular cells and its implications for fibrinolytic therapy of the eye. Drug Dev Res 1989; 18:245-254 10. van Mourik JA, Lawrence DA, Loskutoff DJ. Purification of an inhibitor of plasminogen activator (antiactivator) synthesized by endothelial cells. J Bioi Chem 1984; 259:14914-14921 11. Kruithof EKO, Tran-Thang C, Ransijn A, Bachmann F. Demonstration of a fast-acting inhibitor of plasminogen activators in human plasma. Blood 1984; 64:907-913
REFRACT SURG-VOL 17, SEPTEMBER 1991