Effect of oxygen tension on the quantities of procollagenase-activating angiogenic factor present in the developing kitten retina

Matrix metalloproteinases and metalloproteinase inhibitors in human interphotoreceptor matrix and vitreous

PURPOSE

We wished to establish which matrix metalloproteinases (MMPs) and metalloproteinase inhibitors (TIMPs) were present in human interphotoreceptor matrix (IPM) and vitreous.

METHODS

IPM and vitreous were obtained from postmortem human eyebank eyes. Western immunoblots were probed with antibodies against human MMPs and TIMPs. Assays specific for elastase activity were also performed.

RESULTS

Immunoblot analysis indicated the presence of MMP-1 (interstitial collagenase), MMP-2 and MMP-9 (gelatinases A and B), MMP-3 (stromelysin-1) and TIMP-1, -2 and -3 in both IPM and vitreous. MMP-7 (matrilysin) and MMP-12 (metalloelastase) were not found in either IPM or vitreous.

CONCLUSIONS

This is the first demonstration of the MMPs and TIMPs in human IPM and of the TIMPs in human vitreous. While these enzymes are most likely involved in normal turnover within the extracellular matrices that surround the neural retina, they may also play a role in a number of retinal diseases, particularly proliferative diabetic retinopathy and age-related macular degeneration.

Secretory oedema in diabetic submandibular glands during parasympathetic nerve stimulation: relationship to microvascular abnormalities in streptozotocin-treated rats

1. Submandibular secretion during parasympathetic stimulation (5 Hz) was examined in streptozotocin-diabetic and age-matched control rats. 2. At 3 weeks, but not 3 and 6 months, flow rate was initially greater than in controls, but it declined rapidly after 30 min. 3. The reduction in flow rate was associated with oedema of the gland. 4. At 3 months, graded stimulation revealed a tendency to oedema at frequencies of 10 Hz and above. 5. Morphologically, submandibular capillary density was increased in diabetic rats. 6. Thus, in diabetes the submandibular gland appears less able to withstand continuous parasympathetic stimulation, due in part to an increase in tissue capillary area.

Cryotherapy for retinopathy of prematurity--a prospective study

Cryotherapy has been shown to reduce the unfavourable outcome in retinopathy of prematurity with stage 3 threshold disease by 50%. In a prospective study cryotherapy had a favourable outcome in 13 of 24 eyes with stage 3 threshold disease. The visual outcome, refraction, and complications of cryotherapy are discussed.

Effect of varying oxygen concentrations on the proliferation of retinal microvascular cells in vitro

Microvascular fragments and pure cultures of either retinal microvascular endothelial cells, retinal pericytes or Tenon's capsule fibroblasts were grown on a gas permeable substrate while exposed to varying oxygen concentrations (5, 10, 20, 40 and 95% oxygen). For all three cell types cell proliferation was greatest under the lowest oxygen concentration and decreased as the oxygen concentration increased. The decrease in the proliferative ability of cells exposed to the higher oxygen concentrations could be reversed if the cells were returned to a normoxic environment. Endothelial cells were the most sensitive to changes in oxygen tensions showing a proliferative response after 24 hr exposure as opposed to 48 hr for pericytes and fibroblasts. These results suggest a direct mechanism by which the intra-vitreal and intra-retinal oxygen tension may influence both the development of preretinal new vessels (in response to retinal ischaemia) and also the regression of neovascularization following scatter photocoagulation or vitrectomy.

Effect of partial cryoablation on retinopathy of prematurity

Cryotherapy has been shown to be an effective treatment for retinopathy of prematurity stage 3. It is said to reduce the unfavourable outcome of the disease by 50%. The accepted method of therapy includes ablation of the whole avascular retina from the ridge to the ora serrata. This is achieved by two to three rows of cryoapplications. When 360 degrees cryo treatment is performed, it requires 52 cryo applications. We present our method of cryotherapy which involves only one row of cryoapplications in the avascular retina anterior to the fibrovascular ridge. An average of 25-30 cryoapplications was required for a 360 degrees treatment. The anatomical results in 23 babies are presented. Complete regression of active retinopathy was found in all.

Low molecular weight angiogenesis factors

A number of substances have been proposed for the role of angiogenesis factors. Many of these are of protein origin and are therefore amenable to the tools of the molecular biologist. However a number of low molecular weight angiogenesis factors are emerging as important initiators and/or cofactors of neovascularization. Of these a number are known to stimulate angiogenesis indirectly, possibly through an inflammatory response. Some putative angiogenic factors stimulate microvessel endothelial cells nonspecifically, also causing migration and proliferation of large vessel cells. Others are specific for microvessel cells either for stimulating migration, proliferation or both. The nature and action of the low molecular weight factors in vivo and in vitro are reviewed.

Biometry of the crystalline lens in early-onset diabetes

Lenticular biometry on non-cataractous lenses has been studied by means of Scheimpflug photography and digital image analysis in 153 patients with early-onset insulin-dependent diabetes and 153 non-diabetic controls. Anteroposterior axial lens thickness, cortical thickness, nuclear thickness, anterior and posterior lenticular curvatures, and anterior chamber depth were assessed. Highly significant differences between the lenses of the diabetic subjects and non-diabetic controls were found. After the effect of age had been accounted for within the diabetic subgroup, diabetic duration was found to be a highly significant determinant of lens dimensions, such that age-related dimensional changes for various biometric parameters were accelerated by between 52% and 121% after the onset of diabetes. Because the diabetic duration of the early-onset diabetic subjects studied in this work was accurately known, this report is the first in which a precise assessment of the effect of 'true' diabetic duration on lens biometry has been possible.

Early diagnosis of the retinopathy of incontinentia pigmenti: successful treatment by cryotherapy

Prospective examination of the ocular fundi was carried out in the newborn female sibling of a girl with incontinentia pigmenti and bilateral retinopathy. At age 3 months the new baby's peripheral retina was found to be avascular in both eyes. At age 2 years progressive vascular proliferation at the watershed area between normal and abnormal retina led to bilateral vitreous haemorrhage. The new vessel tufts promptly regressed when the avascular area in each eye was treated by single-freeze cryotherapy and the blood in the vitreous absorbed. Cicatricial retinopathy was thereby prevented. Prospective retinal examination of newborn female siblings of children with incontinentia pigmenti is advised, with early cryotherapy recommended if progressive neovascularisation is detected.

Capillary endothelial-cell mitogenic activity in experimental branch vein occlusion

Since the 1940s, the major hypothesis regarding the stimulus for neovascularization occurring in diabetic retinopathy and other "ischemic" retinopathies has involved the release of a soluble angiogenic factor from the ischemic retina. We sought to test this by measuring the endothelial mitogenic activity that could be extracted from an ischemic retina caused by branch vein occlusion in the cat. We found that the extractable endothelial-cell mitogenic activity from normal retinal areas was similar to that in ischemic areas at 1, 2, and 7 days after the occlusion. In the area of occluded veins, the oxygen partial pressure was low (7 +/- 7 mm Hg) compared with the normal value (23 +/- 8 mm Hg). The data did not show any increase in soluble mitogenic factor release from the ischemic retina versus normal retinal areas under the conditions of this experiment.

Retinopathy of prematurity

Over the last decade major advances have been made in the understanding of the pathogenesis and evolution of retinopathy of prematurity (ROP). The increased survival of very small premature infants in modern neonatal intensive care units has led to the resurgence of this potentially blinding disease. ROP appears to be a multifactorial disease, the prevention of which is probably impossible even now, with the most accurate methods of blood gas monitoring and oxygen restriction. In addition to oxygen, there are a number of significant risk factors, such as birth weight and gestational age, ventilator hours, hyper and hypocarbia, hypoxia and acidosis, xanthine therapy and probably bright light. Current data suggest that the level of antioxidants in the immature retina is relatively low and therefore oxygen radicals which accumulate in the preterm baby's retina may play an important role in the pathogenesis of ROP. The treatment of the disease in both its "active" and "cicatricial" stages emphasizes the need for a new classification which could serve as a common international language through which results may be compared. Vitamin E was suggested in some studies to be helpful in preventing the severe stages of the disease, but its efficacy has yet to be proved. Treatment modalities such as photocoagulation, cryotherapy and vitrectomy are being tried as a means of therapy in the more advanced stages of the disease. Preliminary results of a large multicenter study support the efficacy of cryotherapy.

The effect of cryotherapy on oxygen-induced retinopathy in the newborn kitten

Partial cryotherapy was performed in the right eye of 14 kittens with experimental oxygen-induced retinopathy, while the left eye remained untreated as a control. Subsequent funduscopic examination and histopathological studies of all kittens showed no significant difference between the treated and untreated eyes with respect to the amount of neovascular proliferation. We attribute this negative result mainly to the fact that the cryoablation of the kittens' retina was incomplete, leaving a considerable amount of residual ischemic retina.

Incontinentia pigmenti: the development of pseudoglioma

A case is described of incontinentia pigmenti in an infant with relatively normal retinae at seven days after birth who went on to total blindness by three months. This was due to excessive neovascularisation of retinae and vitreous, leading to bilateral pseudoglioma.

Origin of disc new vessels assessed by videofluorography

Ten patients with disc neovascularisation of various aetiologies were studied to ascertain the origin of their new vessels. Fluorescein angiography was carried out with an image intensified video camera. A retinal artery derivation was demonstrated for the first time and was seen in three cases. Six further patients showed a retinal venous supply, and finally there was one from a choroidal source.

Experimental studies on the pathogenesis of retinopathy of prematurity

The angiogenic activity of various parts of the retina in kittens with oxygen-induced retinopathy has been studied by the use of a corneal micropocket technique and chorioallantoic assay. The results indicate that in retinopathy of prematurity the most important role in the pathogenesis of fibrovascular proliferation is played by the so-called primary avascular retina, that is, that part of the retina which has not yet been vascularised during ontogenesis.

Bovine and human pineal glands contain substantial quantities of endothelial cell stimulating angiogenic factor

Using a quantitative assay the amount of a low Mr endothelial cell stimulating angiogenesis factor (ESAF) has been determined in human pineal glands and bovine brain, retina, pineal gland, liver and kidney. Pineal glands contain approximately ten times as much ESAF as the retina or grey and white matter from the cerebral cortex and a hundred times as much as highly vascular tissues such as liver and kidney. The relevance of these findings to the highly vascular nature of the pineal gland is discussed.

Increased procollagenase activating angiogenic factor in the vitreous humour of oxygen treated kittens

Previous studies have demonstrated an increase in a low molecular weight angiogenic factor (ESAF) present in the retinae of kittens with oxygen induced retinopathy. The present paper describes differences in the quantity of ESAF extracted from the vitreous humour of control and oxygen treated animals and proposes a mechanism for the induction of intravitreal neovascularisation.