Delay In Corneal Wound Healing Research Articles

Therapeutic Potential of Mesenchymal Stem Cell-Secreted Factors on Delay in Corneal Wound Healing by Nitrogen Mustard

Ocular surface exposure to nitrogen mustard (NM) leads to severe ocular toxicity which includes the separation of epithelial and stromal layers, loss of endothelial cells, cell death, and severe loss of tissue function. No definitive treatment for mustard gas-induced ocular surface disorders is currently available. The research was conducted to investigate the therapeutic potential of mesenchymal stem cell-conditioned media (MSC-CM) in NM-induced corneal wounds. NM was added to different types of corneal cells, the ocular surface of porcine, and the ocular surface of mice, followed by MSC-CM treatment. NM significantly induced apoptotic cell death, cellular ROS (Reactive oxygen species), and reduced cell viability, metabolic gene expression, and mitochondrial function, and, in turn, delayed wound healing. The application of MSC-CM post NM exposure partially restored mitochondrial function and decreased intracellular ROS generation which promoted cell survival. MSC-CM therapy enhanced wound healing process. MSC-CM inhibited NM-induced apoptotic cell death in murine and porcine corneal tissue. The application of MSC-CM following a chemical insult led to significant improvements in the preservation of corneal structure and wound healing. In vitro, ex vivo, and in vivo results suggest that MSC-CM can potentially provide targeted therapy for the treatment of chemical eye injuries, including mustard gas keratopathy (MGK) which presents with significant loss of vision alongside numerous corneal pathologies.

Non-steroidal anti-inflammatory drug delays corneal wound healing by reducing production of 12-hydroxyheptadecatrienoic acid, a ligand for leukotriene B4 receptor 2

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used to reduce inflammation by suppressing cyclooxygenases (COXs). NSAID eye drops are frequently prescribed after ocular surgery to reduce inflammation and pain, but this treatment has clinically significant side effects, including corneal ulcer and perforation. The molecular mechanisms underlying these side effects remain unknown. Recently, the COX product 12(S)-hydroxyheptadeca-5Z,8E,10E-trienoic acid (12-HHT) was identified as an endogenous ligand for leukotriene B4 receptor 2 (BLT2), which is important in maintenance of epithelial homeostasis. We hypothesized that NSAID-dependent corneal damage is caused by reduced production of 12-HHT. Diclofenac eye drops decreased the abundance of downstream products of COX and delayed corneal wound healing in BALB/c mice. Expression of BLT2 was observed in murine ocular tissues including cornea, and in human corneal epithelial cell line and human primary corneal epithelial cells. In BLT2-knockout mice, corneal wound healing was delayed, but the diclofenac-dependent delay in corneal wound healing disappeared. 12-HHT accelerated wound closure both in BLT2-transfected corneal cell line and human primary corneal epithelial cells. Thus, our results reveal that NSAIDs delay corneal wound healing by inhibiting 12-HHT production, and suggest that stimulation of the 12-HHT/BLT2 axis represents a novel therapeutic approach to corneal wound healing.

Local Group 2 Innate Lymphoid Cells Promote Corneal Regeneration after Epithelial Abrasion

Corneal injuries and infections are the leading cause of blindness worldwide. Thus, understanding the mechanisms that control healing of the damaged cornea is critical for the development of new therapies to promptly restore vision. Innate lymphoid cells (ILCs) are a recently identified heterogeneous cell population that has been reported to orchestrate immunity and promote tissue repair in the lungs and skin after injury. However, whether ILCs can modulate the repair process in the cornea remains poorly understood. We identified a population of cornea-resident group 2 ILCs (ILC2s) in mice that express CD127, T1/ST2, CD90, and cKit. This cell population was relatively rare in corneas at a steady state but increased after corneal epithelial abrasion. Moreover, ILC2s were maintained and expanded locally at a steady state and after wounding. Depletion of this cell population caused a delay in corneal wound healing, whereas supplementation of ILC2s through adoptive transfer partially restored the healing process. Further investigation revealed that IL-25, IL-33, and thymic stromal lymphopoietin had critical roles in corneal ILC2 responses and that CCR2- corneal macrophages were an important producer of IL-33 in the cornea. Together, these results reveal the critical role of cornea-resident ILC2s in therestoration of corneal epithelial integrity after acute injury and suggest that ILC2 responses dependon local induction of IL-25, IL-33, and thymic stromal lymphopoietin.

The Delay of Corneal Wound Healing by Diclofenac in a Human Ex Vivo Front of the Eye Model and Rabbit Models

The anti-inflammatory drug diclofenac (DCF) relieves postsurgery eye pain and can delay corneal wound healing. This study established a human ex vivo eye model and demonstrates the delay of wound healing by DCF. Human and rabbit response to topical DCF (0.1%) was evaluated after an anterior keratectomy in 1) a New Zealand White rabbit in vivo study, and 2) ex vivo front of the eye models of rabbit and human, which included cornea and eye tissues that synthesize prostaglandins (iris, ciliary body, and conjunctiva). Rabbit corneal wound area in vivo was significantly greater because of DCF at 72 hr (1.72-fold) and 96 hr (2.8-fold), representing a 43% and 64% decrease in wound closure. In rabbit ex vivo eyes, wound area in the presence of DCF remained significantly greater: 1.74-fold at 48 hr and 2.6-fold at 72 hr, up to an 80% decrease in wound closure. In human eyes ex vivo, wound area in the DCF-exposed eyes was significantly greater (1.7-fold at 18 hr), representing a 50% decrease in closure. To further characterize DCF effects, gene expression changes specific to wound repair were evaluated in these ex vivo models. In rabbit cornea, DCF caused an upregulation of cytoskeletal remodeling and inflammation genes, and a decrease of immune response and stress response genes. In human cornea, DCF suppressed many cytoskeleton and remodeling genes and altered several apoptosis genes. This translational ex vivo front of the eye model to mimic in vivo findings strengthens the validity of the human ex vivo model and its potential for identifying clinical hazards.

Hypercalcemia Leads to Delayed Corneal Wound Healing in Ovariectomized Rats.

Hypercalcemia is often observed in postmenopausal women as well as in patients with primary hyperparathyroidism or malignant tumors. In this study, we investigated the relationship between calcium ion (Ca(2+)) levels in lacrimal fluid and the rate of corneal wound healing in hypercalcemia using ovariectomized (OVX) rat debrided corneal epithelium. We also determined the effects of Ca(2+) levels on cell adhesion, proliferation and viability in a human cornea epithelial cell line (HCE-T). The calcium content in bones of OVX rats decreased after ovariectomy. Moreover, the Ca(2+) content in the blood of OVX rats was increased 1 month after ovariectomy, and decreased. The Ca(2+) content in the lacrimal fluid of OVX rats was also increased after ovariectomy, and then decreased similarly as in blood. Corneal wound healing in OVX rats was delayed in comparison with Sham rats (control rats), and a close relationship was observed between the Ca(2+) levels in lacrimal fluid and the rate of corneal wound healing in Sham and OVX rats (y=-0.7863x+8.785, R=0.78, n=25). In addition, an enhancement in Ca(2+) levels caused a decrease in the viability in HCE-T cells. It is possible that enhanced Ca(2+) levels in lacrimal fluid may cause a decrease in the viability of corneal epithelial cells, resulting in a delay in corneal wound healing. These findings provide significant information that can be used to design further studies aimed at reducing corneal damage of patients with hypercalcemia.

Effect of Topical Administration of 0.8% Nalbuphine on the Cornea in Dogs after Phacoemulsification

It is suggested that topical application of opioids may provide localized analgesia without delay in corneal wound healing. This study was designed to evaluate the effect of topical application of 0.8% nalbuphine on post-operative ocular pain in dogs. Twelve eyes from 11 dogs undergoing phacoemulsification cataract surgery were divided into a nalbuphine group (n=6) and saline group (n=6). Postoperatively, the nalbuphine group received 0.1 ml of topical 0.8% alkalinized nalbuphine (pH 5.6) every 8 hr, and the saline group received 0.1 ml of topical saline (pH 5.9) as a placebo. All dogs received systemic postoperative pain managements with oral tramadol (4 mg/kg) and prednisolone (0.5 mg/kg) every 8 hr. All dogs received pre- and post-ophthalmic examinations. Pain was scored in the dogs using a pain scoring system modified from the University of Melbourne pain scale at 15, 30 and 60 min following the topical treatment on days 1 and 2 (24 and 48 hr after surgery). Eye blink frequency and corneal touch threshold (CTT) were recorded at the same time. There was no statistical difference in the pain score between groups. Significant decreases in CTT, blepharospasm and eye blink frequency were observed after the topical nalbuphine treatment. This indicated that topical application of 0.8% nalbuphine solution can produce a rapid reduction of corneal discomfort in dogs.

Effect of dexamethasone in combination with acetylcysteine at different times on corneal wound healing in dogs

Summary The purpose of this study was to evaluate the effects of different time combinations of dexamethasone and acetylcysteine on experimentally induced corneal ulcers in dogs. Experimental corneal wounds were created surgically to the anterior one third of the cornea in the center of all eyes of 15 mixed breed dogs. The eyes were divided into five groups according to planned post-operative medications: group 1, one drop of N- acetylcysteine 3% and one drop of dexamethasone 0.1% immediately after surgery; group 2, two drops of N- acetylcysteine 3% from day 1, one drop of N-acetylcysteine 3% and one drop of dexamethasone 0.1% from day 15; group 3, two drops of N-acetylcysteine 3%; group 4, two drops of dexamethasone 0.1%; group 5 (control), two drops of normal saline. When applied immediately after corneal ulceration, dexamethasone 0.1% (group 4) decreased corneal haze significantly and did not delay corneal wound healing. Addition of dexamethasone 0.1% to N-acetylcysteine 3% from day 15 (group 2) significantly suppressed opacity at two months after the beginning of the study, but when dexamethasone 0.1% associated to N-acetylcysteine 3% immediately after corneal ulceration (group 1), significant delay in corneal wound healing was induced. It is concluded that combination of dexamethasone 0.1% and NAC 3% immediately after surgery may delay corneal wound healing, also use of these drugs individually, has no obvious clinical effect on corneal haze. On the other hand, use of these drugs in combination with each other may reduce the corneal haze in later months after discontinuation of drugs. However, further studies using larger groups of animals are needed to demonstrate the effectiveness of these pharmacological modulators following experimentally induced corneal wounds in dogs.

Conjunctival impression cytology and tear‐film changes in patients with familial Mediterranean fever: authors’ reply

Editor, W e would like to thank Drs Lazar & Rothkoff (2009) for their interest in our recent article, which evaluated ocular surface changes in patients with familial Mediterranean fever (FMF) (Karalezli et al. 2009). We found that despite normal tear production, the ocular surface and tear-film functions of FMF patients differ from those of healthy individuals. We concluded that these changes might be related to the chronic inflammatory nature of FMF. Drs Lazar & Rothkoff stated that ocular surface changes in FMF patients might have resulted from the colchicine treament that they received. There are few case reports in the literature that report the delay of corneal wound healing in patients with FMF who are under colchicine treatment (Biedner et al. 1977; Alster et al. 1997; Leibovitch et al. 2003a, 2003b). However, there is no prospective randomized clinical study that evaluates the effect of colchicine on the ocular surface. Leibovitch et al. (2003a, 2003b) reported that very small quantities of colchicine were secreted in tears but they could not state whether the levels that were measured were in a toxic range. Further prospective randomized control-group studies are needed to confirm the effect of colchicine on the ocular surface and its correlation with the amount and duration of colchicine treatment.

Delay of Corneal Wound Healing in Patients Treated with Colchicine

Colchicine has a known adverse effect on wound healing through its inhibitory effect on tubulin-dependent cell functions and through collagenase activation. In the cornea, it has been shown in animal and in vitro studies to inhibit epithelium mitosis, fibroblast mitosis and migration, as well as to reduce collagen deposition. The authors report on two patients with corneal ulcers refractory to conventional treatment while the patients were undergoing oral colchicine therapy. The first patient was an 86-year-old woman who had been treated with oral colchicine because of rheumatoid arthritis. She was admitted to the authors' department with a deep corneal ulcer in the right eye for which she had been treated for 3 weeks with local antibiotics without any improvement. The second patient, a 60-year-old woman, was hospitalized because of a corneal ulcer in her left eye. She had been receiving oral colchicine therapy for mixed connective tissue disease. Treatment with local antibiotics was initiated but the condition of the eye worsened, ultimately resulting in corneal perforation. Withdrawal of oral colchicine therapy was followed by rapid corneal wound healing in both patients. The findings in these two patients suggest that colchicine may delay corneal wound healing. The authors suggest that in patients with corneal ulcers refractory to conventional treatment who are receiving colchicine, cessation of colchicine therapy should be considered.