Long-Term Endothelial Cell Viability After Deep Anterior Lamellar Versus Penetrating Keratoplasty for Keratoconus

OBJECTIVES

We compared long-term endothelial cell survival after penetrating versus after deep anterior lamellar keratoplasty for keratoconus.

MATERIALS AND METHODS

We retrospectively compared 64 eyes of 55 patients who had penetrating keratoplasty and 40 eyes of 37 patients who had deep anterior lamellar keratoplasty for keratoconus (October 2003-February 2021). Best-corrected visual acuity, Goldmann applanation tonometry, fundus examination with 90D lens, and specular microscopy with CEM-530 (Nidek) were performed preoperatively and every 6 months postoperatively. Main outcomes were endothelial cell density, central corneal thickness, and visual acuity. Secondary outcomes were coefficient of variation, hexagonality, graft rejection episodes, and graft clarity.

RESULTS

We found no significant differences between the 2 treatment groups regarding patient age, donor age, preoperative vision, central corneal thickness, and recipient-donor trephine diameters. Mean follow-up was 92.5 months. In deep anterior lamellar keratoplasty, the endothelium was preserved significantly better for 10 years versus for penetrating keratoplasty. Mean endothelial density in penetrating versus deep anterior lamellar keratoplasty was 2006.7 versus 2354.7 cells/mm2 at 1 year (P = .010), 1170.5 versus 2048.2 at 5 years (P <.001), and 972.5 versus 1831.6 at 10 years (P < .001). Cumulative endothelial cell loss was 43% and 19.7% at 10 years for penetrating and anterior lamellar keratoplasty, respectively. Significantly more thickening of central cornea was shown in penetrating keratoplasty after 7 years. Corneal thickness was 583.0 µm in penetrating and 545.1 µm in deep anterior lamellar keratoplasty (P = .002) at 10 years. Vision gain and coefficient of variation were similar. Hexagonality decreased significantly in both groups at 10 years. Rates of rejection were 12.5% in penetrating and 7.5% in deep anterior lamellar keratoplasty. Graft survival rates were 97.5% and 96.9%, respectively.

CONCLUSIONS

In keratoconus, endothelial vitality is better preserved with deep anterior lamellar keratoplasty than with penetrating keratoplasty over a 10-year follow-up.

Development of Advanced Atherosclerotic Plaque by Injection of Inflammatory Proteins in a Rabbit Iliac Artery Model

PURPOSE

Appropriate animal models of atherosclerotic plaque are crucial to investigating the pathophysiology of atherosclerosis, as well as for the evaluation of the efficacy and safety of vascular devices. We aimed to develop a novel animal model that would be suitable for the study of advanced atherosclerotic lesions in vivo.

MATERIALS AND METHODS

Atherosclerotic plaque was induced in 24 iliac arteries from 12 rabbits by combining a high cholesterol diet, endothelial denudation, and injection into the vessel wall with either saline (n=5), olive oil (n=6), or inflammatory proteins [n=13, high-mobility group protein B1 (HMGB1) n=8 and tumor necrosis factor (TNF)-α n=5] using a Cricket™ Micro-infusion catheter. Optical coherence tomography (OCT) was performed to detect plaque characteristics after 4 weeks, and all tissues were harvested for histological evaluation.

RESULTS

Advanced plaque was more frequently observed in the group injected with inflammatory proteins. Macrophage infiltration was present to a higher degree in the HMGB1 and TNF-α groups, compared to the oil or saline group (82.1±5.1% and 94.6±2.2% compared to 49.6±14.0% and 46.5±9.6%, p-value<0.001), using RAM11 antibody staining. On OCT, lipid rich plaques were more frequently detected in the inflammatory protein group [saline group: 2/5 (40%), oil group: 3/5 (50%), HMGB1 group: 6/8 (75%), and TNF-α group: 5/5 (100%)].

CONCLUSION

These data indicate that this rabbit model of atherosclerotic lesion formation via direct injection of pro-inflammatory proteins into the vessel wall is useful for in vivo studies investigating atherosclerosis.

[Trabeculotomy with Schlemm's Canal Endothelium Removal and Deep Sclerectomy]

Purpose: To evaluate the effects of trabeculotomy (TLO) combined with Schlemm's canal endothelium removal (SER) and deep sclerectomy (DS). Method: This retrospective study involved 131 adults eyes, diagnosed with glaucoma that were enrolled with at least 1 year follow-up after TLO. Fifty three eyes received TLO+SER+DS and 78 eyes underwent TLO+DS without SER. SER was performed as peeling of Schlemm's canal endothelium opening under the scleral flap. Surgical success was defined by the need for additional glaucoma surgery, or intraocular pressure (IOP) ≤20 mmHg (criterion A) and ≤16 mmHg (criterion B). Results: The occurrence rate of transient ocular hypertension (≥30 mmHg) was significantly less (p<0.001) in SER (3.8%) compared with Non-SER (21.8%). SER decreased IOP at 3 years without significant efficacy in terms of lowered IOP compared with Non-SER. At 3 years, Kaplan-Meier survival analysis revealed that the success rate of SER was higher than Non-SER for criterion A (p=0.008), but comparable for criterion B (p=0.06). Conclusions: SER was effective for reducing the rate of transient ocular hypertension in TLO and controlling IOP≤20 mmHg in adult eyes.

The corneal endothelium as a standard for the assessment of complications in microsurgery

Endothelial cell morphology is an important parameter for the quality control of different surgical techniques, especially in the anterior segment. The minimizing effect of hyaluronic acid in implant surgery can be demonstrated by the decrease of endothelial cell loss as compared to standard techniques. Besides, we can show that the implantation of artificial lenses into the capsular bag is less traumatizing to the cornea than anterior chamber lenses. Other factors to control the surgical techniques are the keratoplastics, especially modified to different trephination techniques and last but not least YAG laser surgery of the cataract membranes. In the latter, there is a direct correlation between endothelial trauma and distance of focus and total energy. Even in isolated cases we can draw conclusions from endothelial morphology to intra-postoperative complications. New surgical techniques which could lead to damage of the cornea should be tested by endothelial cell analysis.

A novel therapeutic approach to non‐parasitic splenic cysts: Laparoscopic fenestration and endothelium obliteration

Splenic cyst is a relatively rare disease; true splenic cysts are classified as parasitic and non-parasitic cysts. Although most cysts are asymptomatic, large cyst cases show clinical symptoms, consisting mainly of dyspepsia and fullness in the upper left abdomen. Surgical intervention is recommended primarily for large cysts to prevent complications such as rupture, hemorrhage, and infection. This paper presents our experience of eleven laparoscopic procedures for non-parasitic splenic cysts. Laparoscopic fenestration was performed in all cases, and the cyst endothelium was destroyed . All operations were accomplished successfully. The mean operative time was 56 minutes (range 40-90 minutes). Intraoperative bleeding was 15 ml (range 5-30 ml), oral food intake was started on the first postoperative day. The median duration of postoperative hospitalization was 2.8 days (range 1-7 days). There were no postoperative complications. All cases were followed up for a period of 21 months to 5.5 years, and no recurrence occurred. Laparoscopic fenestration and endothelium obliteration is an advantageous approach to large non-parasitic splenic cysts with little postoperative pain, fast recovery, splenic tissue and splenism preservation, low complication rates, and a short hospital stay; it is easily accepted by patients. It yields favorable medium-term results. Our study confirms that good results can be achieved with an approach of laparoscopic fenestration and endothelium obliteration for simple non-parasitic splenic cysts.

Papillary endothelial hyperplasia of the adrenal gland: report of a case and review of the literature

Papillary endothelial hyperplasia (PEH) is a benign vascular proliferative process most frequently seen in the skin and integument, but may involve any of the visceral organs. It is a rare entity, with less than 30 cases of visceral PEH described in the literature. Adrenal papillary endothelial hyperplasia is an exceedingly rare process and is the basis of this review. A 66-year-old female was referred for evaluation of an asymptomatic 6 cm right adrenal mass. Computed tomography indicated that the lesion was solid and hypervascular. After appropriate workup, the patient underwent laparoscopic adrenalectomy. The pathologic analysis was consistent with adrenal PEH. The patient recovered without incident and is doing well at 1 year follow-up. A review of the world's literature on papillary endothelial hyperplasia (PEH), and in particular adrenal PEH, yields five previous reports of this entity, and no comprehensive review. A compilation of the now six patients with adrenal PEH reveals several common features: five of six patients were female and mean age was 64 years. The disease radiologically mimics adrenal cortical carcinoma mandating a surgical oncological technique. Pathologic differentiation from angiosarcoma can be a difficult task requiring evaluation by an experienced pathologist.

Influence of pressure on the endothelium of the saphenous vein coronary artery bypass graft

The aim of this study was to evaluate the influence of pressure applied while assessing the graft's tightness on the expression of adhesion molecules. Another goal was to find a correlation between the type of fluid (heparynized blood or saline) used during preparation of the conduit and the expression of the adhesion molecules. Saphenous vein fragments were obtained from 48 patients who had undergone coronary artery surgery. Expression of the following particles was evaluated: CD 31, ICAM 1, VCAM 1 and P-selectin. Expression of the CD 31 molecule was described as a percentage of the inner surface of the vessel showing positive immunocytochemical reaction. Expression of the remaining molecules (ICAM 1, VCAM 1, P-selectin) was assessed as the percentage of the surface, determined by CD 31 positive reaction. The expression of the adhesion molecules (ICAM 1, VCAM 1, P-selectin) was higher in the fragments of the vein exposed to pressure. In reference to VCAM 1 the difference, as compared with the control group, was: 250% in the fragments infused with blood and 270% in the fragments infused with saline, respectively. The differences for the ICAM 1 were approximately 300% in both experimental groups and 450% for the P-selectin with subtle differences between the two experimental groups. The loss of the endothelial surface (determined by the expression of the CD 31 antigen) was similar in the specimens flushed either with blood or saline, which indicates that the major cause of damage of the endothelium is influence of pressure on the conduit's wall. Mechanical widening of vessels results in the increased expression of the adhesion molecules on the surface of the endothelial cells, and, as a consequence, leads to rise in the leukocyte adhesion and loss of the functional properties of the transplanted veins.

ATP-dependent K+ channel activation in isolated normal and hypertensive newborn and adult porcine pulmonary vessels

The role of an ATP-dependent K+ channel (K(ATP)+) relaxation in the porcine pulmonary vasculature from birth to adulthood was investigated in vitro using levcromakalim on isolated, prostaglandin F2alpha (30 microM)-precontracted conduit arteries (CA), resistance arteries (RA), and veins (PV). Vessels from neonatal pulmonary hypertensive piglets exposed to chronic hypobaric hypoxia (CHH, 51 kPa) for 3 d, either from birth or from 3 d of age were also studied. Levcromakalim relaxed all vessels in a concentration- and glibenclamide-sensitive manner. In normal CA, the maximal extent of relaxation and sensitivity (EC50) increased between birth and 17 d. Endothelium-removal increased EC50 at 17 d only. Indomethacin (10 microM), but not N(G)-monomethyl-L-arginine (L-NMMA) (30 microM), inhibited relaxation in CA from newborn, 3-d-old, and adult animals. In RA, levcromakalim-induced relaxations did not change during development and endothelium-removal attenuated relaxations in 3-d-old but not in adult animals. At both ages in RA, L-NMMA attenuated relaxations and subsequent addition of L-arginine (1 mM) restored them. In PV, maximal relaxation increased between birth and 6 d with no change of EC50. At all ages, relaxation was partially endothelium-dependent and inhibited by L-NMMA (except in the newborn). Indomethacin only attenuated relaxations in veins from 6- and 17-d-old animals. CHH did not influence relaxant responses in CA and PV but decreased EC50 in RA. Thus K(ATP)+ channel activation caused relaxation from birth onward in all vascular segments with varying endothelium dependence. CHH did not affect relaxation in the large vessels and up-regulated those in RA. These findings indicate a possible role for K(ATP)+ channels during normal adaptation and a potential therapeutic role in the management of pulmonary hypertensive newborn infants.

Corneal endothelial cell loss following trephination

The amount of endothelial cell loss that occurs to the donor cornea during the trephination process was evaluated in 40 porcine eyes. A vital staining technique (alizarin red S and acid violet 19) was used to quantify the extent of endothelial damage and removal. Two types of corneal punches (Weck and H&I0 were used for trephination. The average amount of endothelial loss from the peripheral cornea was 7.9%, accounting for only a 3% loss of endothelial cells over the total surface area of the corneal button. a comparison of the Weck and H&I corneal punches showed no significant difference (P greater than 0.1) by Student's test for both endothelial cell damage and removal.

Corneal allograft rejection in bilateral penetrating keratoplasty: clinical and laboratory studies

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Crucial role of endothelium in the vasodilator response to increased flow in vivo

Experiments were designed to investigate the importance of vascular endothelium in the vasomotor response to increases in flow as observed in conduit arteries (flow-dependent dilation). The diameter changes of femoral arteries (sonomicrometry) in response to increases in flow before and after endothelial damage procedures were studied in 23 dogs anesthetized with sodium pentobarbital. The functional integrity of the endothelial cells underneath the diameter sensors was tested by intra-arterial acetylcholine (local acetylcholine dilation) applied proximally to the sensors while a constant flow was maintained. Unilateral augmentation of femoral arterial flow (4.6 +/- 1.9-fold) induced by peripheral vasodilation or by arteriovenous shunt, elicited dilation (increase in diameter, 116 +/- 91 microns) in 18 of 23 dogs, whereas the diameter of the contralateral control artery was not affected. Mechanical removal of the endothelial cells by means of a balloon catheter abolished both the flow-dependent dilation and the local acetylcholine dilation, whereas the vasomotor responses to norepinephrine and nitroglycerin were not affected. Brief perfusions (1 minute) of the arteries with cell-free hydrogen peroxide solution (90 mM) also abolished the flow-dependent dilation and attenuated the local acetylcholine dilation (by 27 +/- 19%; p less than 0.02), while the responses to norepinephrine and nitroglycerin were not altered. These results suggest that endothelial cells act as mediators of flow-dependent dilation.

A model of corneal re-endotheliazation after surgical trauma

A model for simulating the endothelial damage caused by surgery is described. The model consists of the introduction of a specially constructed instrument into the anterior chamber and using it for scraping the endothelium of a pre-determined, precisely quantifiable area of cornea. The process of healing of the scraped cornea can be followed and measured accurately by biomicroscopy, specular microscopy and histological techniques. The model can be used to study the qualitative and quantitative aspects of endothelium healing and the effects of the various endogenous, exogenous and iatrogenic factors on this process. The preliminary data presented shows that the healed endothelium consists of larger and less densly packed cells. The cell density is reduced by 43.3% after one scraping of 57% of the endothelium and by 69.2% after two such operations. Prolonged mild traumatic iritis causes the appearance of endothelial cells with incongruous shapes.

Pathophysiology and pharmacology of intraocular surgery

Meticulous studies of the pathophysiology of postoperative eyes are mandatory to find the means of reducing the risks of intraocular surgery. Various methods of examination developed for this purpose are described and their clinical significance discussed. The corneal endothelium shows no proliferative capacity even after injury and great care must be taken to protect this vulnerable cell layer. Drugs may be toxic to the corneal endothelium and their use during surgery must be exercised with caution. The intraocular irrigating solutions must contain calcium and have an appropriate salt composition. Pupillary constriction that occurs during extracapsular cataract extraction is due mainly to prostaglandins synthesized as a result of surgical trauma; this can be prevented by the preoperative use of topical indomethacin. Breakdown of the blood-aqueous barrier after intraocular surgery may also be due to a similar mechanism, and preoperative topical non-steroidal anti-inflammatory agents (indomethacin, flurbiprofen and diclofenac) can prevent this phenomenon, as studied by fluorophotometry. Topical indomethacin also prevents cystoid macular oedema after cataract surgery. Based on the biochemical findings on inflammation after tissue injury, a protocol for the preoperative and postoperative use of corticosteroid and non-steroidal anti-inflammatory agents is proposed for anterior segment surgery.

Scanning electron microscope study of microvenous grafts to artery

The healing of microvenous grafts to femoral arteries in the rabbit has been studied using scanning electron microscopy at intervals ranging from zero time to 5 months. Healing of the grafts followed a similar pattern to that of end-to-end repairs. Postoperative survival of the original endothelium was far superior in the vein than in the artery. Re-endothelialization was completed by 2 weeks. No dilation of the graft or aneurysm formation appeared. A detailed account of the healing vein grafts has been reported and will enable comparison of healing of microvascular heterografts.

The care of vascular endothelium in pediatric surgery

The influence of manipulating blood vessels by clamping, drying, stretching and surgical anastomotic technique on the subsequent integrity of blood vessel endothelium has been studied in the dog. Thrombogenesis at the vessel surface was found in all specimens where loss of endothelium had exposed subendothelial tissues. Whether thrombotic occlusion of the vessel followed depended upon several local factors including the amount of surface area damaged and volume of blood flow in the vessel. All modes of vessel manipulation studied led to significant endothelial damage. To prevent this damage in the clinical setting all possible methods to avoid the exposure of subendothelial tissues should be used. Endothelial integrity is the cornerstone to success in handling blood vessels and avoiding thrombogenesis. This study suggests that clamping of blood vessels should always be done with a minimum of force, only preventing blood flow, and not crushing the vessel wall. Endothelial surfaces should never be allowed to become dry. Stretching should be avoided as it can lead to thrombosis within intact blood vessels when the endothelium is disrupted. Suture anastomotic techniques should be used which minimize endothelial trauma and thus avoid subendothelial tissue reactions which in turn may jeopardize long-term patency and growth at anastomotic sites. In pediatric cases where growth is anticipated interrupted suture technique should be used. This study suggests that many techniques currently used in vascular surgery may be compromising to short and long-term blood vessel patency.