Subcellular localization of procollagen I and prolyl 4-hydroxylase in corneal endothelial cells.

To investigate the molecular mechanism of intracellular degradation of type I collagen in normal corneal endothelial cells (CEC), we studied the role of prolyl 4-hydroxylase (P4-H) and protein disulfide-isomerase (PDI; the beta subunit of P4-H) during procollagen I biosynthesis. When the subcellular localization of P4-H and PDI was determined, P4-H demonstrated a characteristic diffuse endoplasmic reticulum (ER) pattern, whereas PDI showed a slightly more restricted distribution within the ER. When colocalization of procollagen I with the enzymes was examined, procollagen I and PDI showed a large degree of colocalization. P4-H and procollagen I were predominantly colocalized at the perinuclear site. When colocalization of type IV collagen with PDI and P4-H was examined, type IV collagen was largely colocalized with PDI, which showed a wider distribution than type IV collagen. Type IV collagen is similarly colocalized with P4-H, except in some perinuclear sites. The colocalization profiles of procollagen I with both PDI and P4-H were not altered in cells treated with alpha,alpha'-dipyridyl compared to those of the untreated cells. The underhydroxylated type IV collagen demonstrated a colocalization profile with PDI similar to that observed with procollagen I, while the underhydroxylated type IV collagen was predominantly colocalized with P4-H at the perinuclear sites. Immunoblot analysis showed no real differences in the amounts of the beta subunit/PDI and the catalytic alpha subunit of P4-H in CEC compared to those of corneal stromal fibroblasts (CSF). When protein-protein association was determined, procollagen I was associated with PDI much more in CEC than it was in CSF, whereas type IV collagen showed no differential association specificity to PDI in both cells. Limited proteolysis of the newly synthesized intracellular procollagen I with pepsin showed that procollagen I in CEC was degraded by pepsin, whereas CSF contained type I collagen composed of alpha1(I) and alpha2(I). These findings suggest that procollagen I synthesized in CEC is not in triple helical conformation and that the improperly folded procollagen I may be preferentially associated with PDI before targeting to the intracellular degradation.

A histomorphometric study of corneal endothelial cells in normal human fetuses.

The purpose of this study was to investigate the histomorphometric change in the normal development of human fetal corneal endothelial cells. Eighty one human fetal corneas, ranging from 12 to 40 weeks of gestation, were examined. For determination of gross parameters, corneal diameter and height were measured. Then the corneal endothelium including Descemet's membrane was stained with hematoxylin-eosin using a flat preparation method. In addition to histologic examination under the light microscope, computer-assisted image analysis was performed to determine the cell area, coefficient of variation in cell area and cell density, in both central and peripheral cornea, from each specimen. Total cell count per cornea was obtained by multiplying endothelial cell density by corneal surface area. Linear and nonlinear regression analysis of gestational age and each parameter were used to model corneal endothelial development during the prenatal period. Fetal cornea grows rapidly throughout the prenatal period. During the same period, mean cell area and total cell count also increases gradually, but there is a steep increase in the total cell count in the early period and of the cell area in the late period. The mean cell density decreases rapidly from 16 015 to 6167 cell x mm(-2). There was no significant difference in all parameters except cell density, between the central and peripheral cornea and the difference in cell density was only 2%. In the early prenatal period, there is a rapid increase of total cell count by mitosis, whereas in the late period enlarged endothelial cells cover the rapidly widening inner corneal surface without a significant change in the total cell count.

Inhibition of fungal appressorium formation by pepper (Capsicum annuum) esterase.

A pepper esterase gene (PepEST) that is highly expressed during an incompatible interaction between pepper (Capsicum annuum) and the anthracnose fungus Colletotrichum gloeosporioides has been previously cloned. Glutathione-S-transferase-tagged recombinant PepEST protein expressed in Escherichia coli showed substrate specificity for p-nitrophenyl esters. Inoculation of compatible unripe pepper fruits with C. gloeosporioides spores amended with the recombinant protein did not cause anthracnose symptoms on the fruit. The recombinant protein has no fungicidal activity, but it significantly inhibits appressorium formation of the anthracnose fungus in a dose-dependent manner. An esterase from porcine liver also inhibited appressorium formation, and the recombinant protein inhibited appressorium formation in the rice blast fungus, Magnaporthe grisea. Inhibition of appressorium formation in M. grisea by the recombinant protein was reversible by treatment with cyclic AMP (cAMP) or 1,16-hexadecanediol. The results suggest that the recombinant protein regulates appressorium formation by modulating the cAMP-dependent signaling pathway in this fungus. Taken together, the PepEST esterase activity can inhibit appressorium formation of C. gloeosporioides, which may result in protection of the unripe fruit against the fungus.

Clinical features of traumatic corneal endothelial rings.

We report the clinical features and the course of traumatic corneal endothelial rings by trauma. Fourteen eyes (of fourteen patients) with traumatic endothelial rings (twelve cases of BB shot injury), were enrolled in this study. With median follow-up interval of 50 weeks, initial and final best corrected visual acuity, presence of combined injuries such as gross hyphema, and time of disappearance of traumatic endothelial rings were recorded. And specular microscopic examination was performed. The duration of existence of traumatic endothelial rings was mean 4.6 days. On the specular microscopic examination, the count of corneal endothelial cells in the injured eye decreased by mean 16.8% (ranged from 1 to 56%) than that in the opposite unjnjured eye. The duration of existence of traumatic endothelial rings was 3.5 days in the group without combined angle recession and was 6.1 days in the group with combined angle recession. We suggest that the possibility of traumatic corneal endothelial rings and resultant endothelial cell loss and their clinical potential should be always kept in mind in ocular trauma, particularly BB shot injury.

Subcellular localization of the expressed 18 kDa FGF-2 isoform in corneal endothelial cells.

PURPOSE: To determine the subcellular localization of 18 kDa FGF-2 after synthesis and before secretion into the extracellular matrix. METHODS: Corneal endothelial cells (CEC) were transfected with an expression vector coding for green fluorescent protein (GFP) and 18 kDa FGF-2. Expression of the fusion protein was determined by immunoblot analysis and the subcellular localization of the fusion protein was examined by immunocytochemical analysis. RESULTS: When the expression of the fusion protein was determined by immunoblot analysis, the expressed fusion protein had a molecular weight of 45 kDa, resulting from the 27 kDa GFP and 18 kDa FGF-2. Following a 90 min exposure of cells to the vector, the expressed 18 kDa FGF-2 was completely translocated to the nucleus within a 24 h incubation. When cells were further incubated for another 24 h, one-half of the fusion protein was retro-transported from the nucleus to the cytoplasm, largely to the membrane and focal adhesion site, while the other half remained in the nucleus. During a 72 h incubation, the fusion protein was completely translocated to the cytoplasm, where it was diffusely distributed and its staining potential was greatly lost. Transfected cells showed both a slight increase in cell proliferation and a down-regulation in the expression of the high affinity receptors of FGF. CONCLUSIONS: These results indicate that the 18 kDa FGF-2 is directly translocated from its synthetic site to the nucleus. The nuclear 18 kDa FGF-2 is then retro-transported to membrane/focal adhesion sites, after which the molecule may be secreted. When 18 kDa FGF-2 remains in the nucleus, there is a slight stimulatory activity of cell proliferation and a down-regulation of its receptor. These data suggest an intracellular action of 18 kDa FGF-2 through mechanisms independent of the receptor-mediated signaling pathways.

Posterior segment neovascularization associated with acute ophthalmic artery obstruction.

PURPOSE: To report previously unrecorded ocular neovascularization associated with acute ophthalmic artery obstruction (AOAO) that presents clinical manifestations of acute concomitant obstruction of the retinal and posterior ciliary circulations. METHODS: This report documents the clinical, fluorescein angiographic, and histopathologic findings in two patients with AOAO followed by posterior segment neovascularization. RESULTS: Ophthalmoscopic findings showed whitening of the posterior pole, arterial attenuation, and a pale optic disk. Serial fluorescein angiograms showed a nearly total shutdown of choroidal and retinal perfusion, degeneration of the retinal pigment epithelium and choriocapillaris, and eventual development of a huge neovascular frond at the posterior pole. Histopathologic examination of the enucleated eyeball showed inner retinal necrosis caused by central retinal artery obstruction, degeneration of the outer retina with choriocapillaris obstruction caused by impairment of choroidal circulation, and a thick preretinal neovascular frond at the posterior pole. CONCLUSIONS: These results suggest that AOAO can induce ocular neovascularization, which to the authors' knowledge has not yet been reported.

[Individualization and optimization of surgical treatment of the splenic traumatic injuries]. / Indyvidualizatsiia ta optymizatsiia khirunhichnoho likuvannia travmatychnoho ushkodzennia selezinky.

The frequency of organ-preservation was raised up to 24%, the frequency of the purulent-inflammatory complications was lowered to 15.7% as well as mortality--to 11.7% during performance of operations on spleen due to application of the proposed individualized staged approach and new methods of hemostasis.

Cell density of the corneal endothelium in human fetus by flat preparation.

PURPOSE: To count the number of the corneal endothelial cells per unit of tissue area in 25 human fetal eyes ranging from 12-40 weeks of gestation with the histologic method. METHODS: The endothelium including Descemet's membrane was stained with hematoxylin-eosin by the flat preparation method. We photographed the endothelium using light microscopy. The number of nuclei was counted on each photograph. A calibrated micrometer was photographed with the light microscopy, and this was used to measure the number of corneal endothelial cells per square millimeter. RESULTS: The prenatal endothelial cell density of the human cornea decreases rapidly from 14,095 cells/mm2 (12 weeks of gestation) to 6,820 cells/mm2 (40 weeks of gestation). CONCLUSION: The estimate of the endothelial cell density at 12 weeks of gestation is twofold higher than the estimate at 40 weeks of gestation.

Coexpression of a defensin gene and a thionin-like via different signal transduction pathways in pepper and Colletotrichum gloeosporioides interactions.

The anthracnose fungus, Colletotrichum gloeosporioides, interacts incompatibly with the ripe fruit of pepper (Capsicum annuum). It interacts compatibly with the unripe-mature fruit. We isolated a defensin gene, jl-l, and a thionin-like gene, PepThi, expressed in the incompatible interaction by using an mRNA differential display method. Both genes were developmentally regulated during fruit ripening, organ-specifically regulated, and differentially induced during the compatible and incompatible interactions. Expression of the PepThi gene was rapidly induced in the incompatible-ripe fruit upon fungal infection. The fungus-inducible PepThi gene is highly inducible only in the unripe fruit by salicylic acid. In both ripe and unripe fruit, it was induced by wounding, but not by jasmonic acid. Expression of the jl-l gene is enhanced by jasmonic acid in the unripe fruit but suppressed in the ripe fruit. These results suggest that both small and cysteine-rich protein genes are induced via different signal transduction pathways during fruit ripening to protect the reproductive organs against biotic and abiotic stresses.

Hsp47-dependent and -independent intracellular trafficking of type I collagen in corneal endothelial cells.

PURPOSE: Type I collagen is post-translationally regulated in corneal endothelial cells (CEC): CEC synthesize procollagen I and degrade it intracellularly. We investigated whether there is a Hsp47-independent pathway during intracellular trafficking of procollagen I. METHODS: Specific inhibitors were used to block intracellular transport of procollagen I and Hsp47. Immunocytochemical analysis was performed to determine the intracellular localization of the proteins of interest. RESULTS: When cells were treated with alpha,alpha'-dipyridyl, this specific inhibitor for collagen promoted retention in the endoplasmic reticulum (ER) of some of the underhydroxylated procollagen I, which was colocalized with Hsp47 in CEC. At the same time, another fraction of the alpha,alpha'-dipyridyl-induced underhydroxylated procollagen I was not located in the ER. When CEC were treated with brefeldin A, procollagen I and Hsp47 demonstrated a high degree of colocalization at the ER, whereas the inhibitor had less of an effect on the compartmentalization of procollagen I and prolyl 4-hydroxylase. When CEC were treated with either monensin or bafilomycin A1, procollagen I and Hsp47 were not colocalized: procollagen I was mostly localized at the Golgi area, while Hsp47 predominantly showed ER distribution. When colocalization of procollagen I and prolyl 4-hydroxylase was examined, a major population of procollagen I was not colocalized with prolyl 4-hydroxylase in the ER. CONCLUSIONS: These results indicate that some procollagen I and Hsp47 travel together from the ER to the cis-Golgi compartment and that a major population of procollagen I that may not be properly hydroxylated may be destroyed intracellularly via the Hsp47-independent pathway in CEC.

Morphological variations of the peripapillary circle of Zinn-Haller by flat section.

AIMS: To evaluate the morphometric and morphological variations of the circle of Zinn-Haller (CZH) in the human eye. METHODS: 42 human enucleated eyes were used in this study. After transverse flat thick sections were cut through the optic nerve and adjacent sclera, tissue sections were stained with haematoxylin and eosin or examined immediately by wet preparation under a light microscope. The average vessel diameter of the arterial circle and the average distance between the optic nerve head (ONH) and the arterial circle were determined. Various branching patterns of the CZH were also evaluated. RESULTS: The vessel diameter of the arterial circle was 123 (SD 75) microm (range 20-230 microm). The distance of the CZH from the ONH margin was 403 (352) microm (0-1050 microm). The CZH gave off branches to the optic nerve and to the peripapillary choroid (PPC) with various branching patterns especially at the entry point of paraoptic short posterior ciliary artery. CONCLUSIONS: The CZH exists within a variable distance from the ONH and its average diameter is similar to that of the central retinal vessels though it shows marked variation even in the same circle. The CZH also shows variable configurations in branching patterns. These variations may act as contributing factors that are responsible for the individual susceptibility of the anterior optic nerve and the PPC to circulatory disturbances.

Intracellular interaction of Hsp47 and type I collagen in corneal endothelial cells.

PURPOSE: Previous studies by the current investigators showed that type I collagen was posttranslationally regulated in corneal endothelial cells (CECs). These cells synthesize type I procollagen and degrade it intracellularly; however, when CECs are modulated with fibroblast growth factor-2 and/or corneal endothelium modulation factor, they synthesize and secrete type I collagen. Heat shock protein 47 (Hsp47), an endoplasmic reticulum resident protein, is known to function as a molecular chaperon in regulating procollagen folding and/or assembly. The interaction of Hsp47 with type I procollagen synthesis in CECs was also studied. METHODS: Expression of proteins was analyzed by radioactive labeling or immunoblot analysis. The steady state level of type I collagen and Hsp47 mRNAs was determined by northern blot analysis. Coprecipitation using immunoprecipitation followed by immunoblotting was performed to determine the association profile between Hsp47 and type I procollagen. Subcellular localization of Hsp47 and type I procollagen was determined by immunofluorescent staining. RESULTS: Normal and modulated cells expressed Hsp47 and Hsp70. The relative amount of Hsp47 produced by modulated cells was much higher than that of control cells, but the expression level of Hsp70 was the same in control and modulated cells. The steady state levels of type I collagen transcripts were higher in normal cells than in modulated cells, whereas modulated cells contained a much higher steady state level of Hsp47 mRNA. Type I procollagen was found to be associated with Hsp47 when analyzed by coprecipitation or cross-linking. The cytoplasmic localization profile of Hsp47 and type I collagen was different in normal cells, although a colocalization profile was observed to some degree. These two proteins were predominantly colocalized in the Golgi area in modulated CECs. CONCLUSIONS: Hsp47 may be involved in the synthesis and/or intracellular transport of type I collagen in CECs. Modulated cells that secrete type I collagen into the extracellular matrix express a higher level of Hsp47 than do control cells.

A cytochrome P450 gene is differentially expressed in compatible and incompatible interactions between pepper (Capsicum annuum) and the anthracnose fungus, Colletotrichum gloeosporioides.

The anthracnose fungus, Colletotrichum gloeosporioides, was previously shown to have an incompatible interaction with ripe-red fruit of pepper (Capsicum annuum). However, the fungus had a compatible interaction with unripe-mature-green fruit. Using mRNA differential display, we isolated and characterized a PepCYP gene expressed in the incompatible interaction. The PepCYP gene encodes a protein homologous to cytochrome P450 proteins containing a heme-binding domain. The expression level of PepCYP is higher in the incompatible interaction than in the compatible interaction, and then remains elevated in the incompatible interaction. In the compatible interaction, the expression of PepCYP is transient. The induction of PepCYP gene is up-regulated by wounding or jasmonic acid treatment during ripening. Analysis of PepCYP expression by in situ hybridization shows that the accumulation of PepCYP mRNA is localized in the epidermal cell layers, but not in the cortical cell layers. An examination of transverse sections of the fruits inoculated with the fungus shows that the fungus invades and colonizes the epidermal cell layers of the unripe fruit at 24 and 72 h after inoculation, respectively, but not those of the ripe fruit. These results suggest that the PepCYP gene product plays a role in the defense mechanism when the fungus invades and colonizes the epidermal cells of fruits in the incompatible interaction during the early fungal infection process.

Distribution of proteoglycans in the human trabecular meshwork: histochemical electron microscopic findings with cuprolinic blue.

The distribution of sulfated proteoglycans (PGs) in the normal human trabecular meshwork was studied by histochemical electron microscopy using the cationic dye, cuprolinic blue (CB).. The trabecular meshwork was obtained from human enucleated eyes and incubated for three days. After incubation, they were stained with 0.2% CB at a critical electrolyte concentration and prepared for histochemical electron microscopy. Ultrastructurally, PG-CB complexes were found as small punctate or filamentous structures, and were associated with collagen fibrils in the cores of the trabecular beams and the basal laminae of trabecular endothelial cells. In addition, large filamentous PG-CB complexes were mainly associated with areas of amorphous extracellular matrix between the collagen fiber bundles and in the fine fibrillar material near the basal laminae of endothelial cells of Schlemm's canal. This investigation resulted in an illustration of the ultrastructural distribution of PGs in the human trabecular meshwork. Further studies will be needed to specify the nature of PGs and their role in the aqueous outflow system.

Fluorescein angiographic features of choroidal insufficiency in anterior ischemic optic neuropathy.

Anterior ischemic optic neuropathy(AION) is known to be caused by circulatory disturbance in the anterior optic nerve(AON). Because the AON shares blood supply from the paraoptic short posterior ciliary artery with peripapillary choroid, the authors investigated the angiographic evidences of combined choroidal insufficiency in patients with acute AION. Fundus fluorescein angiograms from 30 eyes from 28 patients with acute AION were enrolled in this study. The diagnosis of acute AION was based primarily on angiographic evidences of filling delay of optic nerve head and the various clinical features, such as decreased visual acuity, visual field defects, afferent pupillary defect, and optic disc swelling. Angiographic evidences of combined choroidal filling delay were as follows: 1) circular or localized filling delay of peripapillary choroid in 15 eyes (50%), 2) generalized filling delay of posterior pole in 11 eyes (36.7%), 3) filling delay of unilateral choroid divided by watershed zone in 5 eyes (16.7%), and 4) choriocapillary filling delay in 10 eyes (33.3%). In this study, various types of choroidal insufficiency in patients with AION were observed, which helped us to differentiate AION from the other various diseases of the anterior optic nerve.

Cymbidium mosaic virus coat protein gene in antisense confers resistance to transgenic Nicotiana occidentalis.

The nucleotide sequence of the 3'-terminal region of the Korean isolate of cymbidium mosaic virus (CyMV-Ca) from a naturally infected cattleya was determined. The sequence contains an open reading frame (ORF) coding for the viral coat protein (CP) at the 3'-end and three other ORFs (triple gene block or movement protein) of CyMV. The CP gene encodes a polypeptide chain of 220 amino acids with a molecular mass of 23,760 Da. The deduced CP sequence showed a strong homology with those of two CyMVs reported. A construct of the CyMV-Ca CP gene in the antisense orientation in the plant expression vector pMBP1 was transferred via Agrobacterium tumefaciens-mediated transformation into Nicotiana occidentalis which is a propagation host of CyMV. The T1 progeny of the transgenic plants were inoculated with CyMV and found to be highly resistant to CyMV infection.

Fibroblast growth factor 2 uses PLC-gamma1 for cell proliferation and PI3-kinase for alteration of cell shape and cell proliferation in corneal endothelial cells.

PURPOSE: Fibroblast growth factor 2 (FGF-2) induces endothelial-mesenchymal modulation in corneal endothelial cells, including stimulation of cell proliferation and cell shape change and induction of fibrillar collagen. In the present study, we investigated whether FGF-2 uses distinct signaling pathways for individual biological activities. METHODS: Specific metabolic inhibitors were used to block cell proliferation, while reversion of cellular morphology (modulated with FGF-2) was determined using specific antibodies and inhibitors. Immunocytochemical analysis was performed to identify any changes observed in the cytoskeleton in relation to cell shape. Association of cytoskeleton molecules with phosphatidylinositol 3-kinase was determined using co-precipitation. Cell proliferation was assayed using a colorimetric method for determining the number of viable cells. RESULTS: The fibroblastic morphology induced by FGF-2 reverted to a polygonal shape in cells treated with anti-FGF-2 antibody, anti-phosphatidylinositol 3-kinase antibody, LY294002, and genistein, while anti-phospholipase C gamma1 antibody did not to reverse the modulated cell morphology. Cell proliferation mediated by FGF-2 was blocked by metabolic inhibitors (genistein, LY294002 and wortmannin); genistein inhibited FGF-mediated cell proliferation in a dose-response manner and had a maximum inhibition of 80% at 100 microM, while inhibitors of phosphatidylinositol 3-kinase had less inhibitory effect than did genistein. When cytoskeleton proteins were examined, the characteristic punctated staining profiles of vinculin observed in normal cells were maintained in fibroblastic corneal endothelial cells treated with FGF-2. The inhibitors that cause reversion of cell shape also demonstrated the punctated staining potential. Likewise, the staining profiles of alpha-actinin and smooth muscle alpha-actin were not altered, regardless of cell shape. Filamentous actin and alpha-actinin were co-localized to the cytoskeleton and phosphatidylinositol 3-kinase was associated with the cytoskeleton, regardless of cell shape. CONCLUSIONS: These findings indicate that FGF-2 uses distinct and/or dual signaling pathways for individual biological activities.

Co-cultivation of conjunctival epithelial cells and Chlamydia trachomatis: electron microscopic findings.

This study used primary culture of rabbit conjunctival epithelial cells to investigate the infection process of chlamydia. The epithelial cells isolated from conjunctiva of rabbit were initially cultured for three weeks. After attaining confluence they were infected with Chlamydia trachomatis (C. trachomatis) serotype D, and after co-cultivation for 24, 48, and 96 hours, electron microscopic study was performed. An inclusion body, a characteristic finding of chlamydial infection, was observed in the vicinity of the nucleus after 24 hours of co-cultivation. It contained a large number of elementary and reticulate bodies and their intermediate forms. Infectious particles known as elementary bodies were noted in the inclusion as 20 to 30 microns sized round bodies with an electron dense core. Reticulate bodies were also noted; they too were round but somewhat pleomorphic and larger than elementary bodies. Some reticulate bodies multiplied actively by means of binary fission. In this study, we observed the characteristic changes of C. trachomatis-infected cells; this in-vitro system might provide a suitable model for the study of some aspects of the pathogenesis of ocular chlamydia infection.

The ultrastructure of corneal epithelium after co-cultivation with herpes simplex virus.

To elucidate the ultrastructural change of corneal epithelium co-cultured with herpes simplex virus (HSV), the corneal epithelium of 3 rabbits was excised and cultivated in culture media. After 7 days, the Kos strain of herpes simplex virus was inoculated in the cultured cornea epithelium until cytopathic effect was occurred. It was fixed in the solution of 3% glutaraldehyde and examined with electronmicroscope. In co-cultured cells, the intercellular spaces had increased and microvilli were seen prominently. The virus particles that initiated the infection by fusing the viral envelope with the plasma membrane were also seen. The nuclear degeneration in an infected cell was prominent. The nuclear membrane was folded markedly, and the chromatin was degraded, condensed and displaced toward the nuclear membrane. Numerous viral particles and inclusion bodies were present in the nuclei. These findings suggest that the infectious process of herpes simplex virus in the human corneal epithelium may occur in a similar way. This result would be helpful in understanding the pathogenesis of herpes simplex epithelial keratitis.

Epithelial ingrowth of anterior chamber and anterior surface of vitreous.

This study is a case report of the histopathologic findings of the anterior chamber epithelial ingrowth in a patient who had penetrating injury in the right eye from an arrow approximately 20 years ago. The patient underwent the enucleation in the right eye due to pthisis bulbi and was fitted with a prosthetic eye. Specimens were prepared from the enucleated right eye for histopathologic observation using hematoxyllin-eosin to be observed under light microscopy. Epithelial ingrowth in the anterior chamber was noted in one layer or multi-layered epithelial cell growth. The ingrowth had spread to the posterior surface of the cornea to the anterior chamber angle, to the iris surface, and to the anterior surface of the vitreous. The finding suggests that epithelial ingrowth could invade even through a perforation site and spread wherever the cells could reach.