[Corneal wound healing-Pathophysiology and principles]

[Wound healing after trabeculectomy : What and when in postoperative aftercare?]

Excessive wound healing in filtering glaucoma surgery is a key factor for a failed surgery. After the introduction of trabeculectomy in the 1960s many factors associated with an increased fibrotic reaction were recognized and methods were developed to influence postoperative wound healing. These range from the perioperative use of anti-inflammatory drugs and antimetabolites to the use of newer chemical compounds that influence the morphology of postoperative fibroblast growth. In the routine clinical practice, the fine tuning of therapeutic decisions plays a decisive role in the success or failure of filtration surgery.

Augenverätzungen

Chemical burns of the ocular surface (CBOS) are emergencies of highest urgency. Therefore, an adequate emergency care is mandatory. Following a precise analysis of the initial damage, a staged therapeutic approach is used to prevent persistent impairment of the ocular surface. In the acute stage, the prevention of complications is targeted (symblepharon, conjunctival scarring, lacrimal stenosis, corneal ulceration, intraocular inflammation, elevated intraocular pressure, etc.). In later stages, if complications have developed, a secondary restoration of the ocular surface is focussed. Sometimes this requires several surgical interventions. Based on a review of international literature, this review highlights the pathophysiology according to different chemical agents, CBOS stages as well as main therapy strategies in early and advanced stages of CBOS. Acute treatment aims to lower inflammation, oxidative stress and tries to promote reepithelialisation. Besides conjunctival scarring, loss of goblet cells and corneal opacification a limbal stem cell insufficiency is the most harming complication. Several new techniques have been developed to recover the ocular surface with a sufficient and clear epithelial layer in order to avoid neovascularization of the cornea. The knowledge concerning the high risk potential for persistent visual impairment in CBOS patients and the ability for appropriate emergency care should be kept in every physician's mind dealing with CBOS.

[Corneal wound healing-Pharmacological treatment]

Physiological wound healing of the cornea is a complex process and involves numerous multifactorial tissue processes. A proper wound healing, especially without the formation of light-scattering scars, is essential to preserve the integrity and function of the cornea. Misdirected wound healing is of vast clinical relevance as it can lead to corneal fibrosis and the loss of optical transparency with subsequent reduction of visual acuity, up to blindness. In addition to the understanding of the pathophysiological mechanisms, the knowledge of therapeutic concepts and options for treating corneal wound healing disorders and fibrosis is essential to counteract a permanent damage of the cornea as early as possible. Nowadays, various pharmacological and surgical options are available for treatment. The decision, appropriate selection and indication for the optimal treatment depend primarily on the genesis and clinical appearance of the corneal wound, fibrosis or scar. The treatment of wound healing disorders ranges from the use of topical therapy and supportive measures up to tissue replacement procedures. As long as the mechanical stability of the cornea is intact and wound healing processes are still ongoing, a pharmacological modulation is reasonable, which is discussed in this article.

C1q/TNF-Related Proteins 1, 6 and 8 Are Involved in Corneal Epithelial Wound Closure by Targeting Relaxin Receptor RXFP1 In Vitro

Inadequate wound healing of ocular surface injuries can lead to permanent visual impairment. The relaxin ligand-receptor system has been demonstrated to promote corneal wound healing through increased cell migration and modulation of extracellular matrix formation. Recently, C1q/tumor necrosis factor-related protein (CTRP) 8 was identified as a novel interaction partner of relaxin receptor RXFP1. Additional data also suggest a role for CTRP1 and CTRP6 in RXFP1-mediated cAMP signaling. However, the role of CTRP1, CTRP6 and CTRP8 at the ocular surface remains unclear. In this study, we investigated the effects of CTRP1, CTRP6, and CTRP8 on epithelial ocular surface wound closure and their dependence on the RXFP1 receptor pathway. CTRP1, CTRP6, and CTRP8 expression was analyzed by RT-PCR and immunohistochemistry in human tissues and cell lines derived from the ocular surface and lacrimal apparatus. In vitro ocular surface wound modeling was performed using scratch assays. We analyzed the effects of recombinant CTRP1, CTRP6, and CTRP8 on cell proliferation and migration in human corneal and conjunctival epithelial cell lines. Dependence on RXFP1 signaling was established by inhibiting ligand binding to RXFP1 using a specific anti-RXFP1 antibody. We detected the expression of CTRP1, CTRP6, and CTRP8 in human tissue samples of the cornea, conjunctiva, meibomian gland, efferent tear ducts, and lacrimal gland, as well as in human corneal, conjunctival, and meibomian gland epithelial cell lines. Scratch assays revealed a dose-dependent increase in the closure rate of surface defects in human corneal epithelial cells after treatment with CTRP1, CTRP6, and CTRP8, but not in conjunctival epithelial cells. Inhibition of RXFP1 fully attenuated the effect of CTRP8 on the closure rate of surface defects in human corneal epithelial cells, whereas the CTRP1 and CTRP6 effects were not completely suppressed. Conclusions: Our findings demonstrate a novel role for CTRP1, CTRP6, and CTRP8 in corneal epithelial wound closure and suggest an involvement of the relaxin receptor RXFP1 signaling pathway. This could be a first step toward new approaches for pharmacological and therapeutic intervention.