Epithelial basement membrane proteins perlecan and nidogen-2 are up-regulated in stromal cells after epithelial injury in human corneas

Abstract

The epithelial basement membrane (BM) is a specialized extracellular matrix that has been shown to have a critical role in corneal development, wound healing, and disease. Although the epithelial BM contributes to corneal homeostasis, relatively little is know about non-epithelial production of its components that may be important in defective regeneration of the epithelial basement membrane associated with opacity after photorefractive keratectomy. The purpose of the current study was to investigate stromal production of corneal epithelial BM proteins in wounded human corneas using immunohistochemistry. A total of five unwounded control eyes and five 30-minute epithelial-wounded corneas were obtained from fresh corneoscleral buttons removed from human eyes enucleated due to choroidal melanoma with normal anterior segments. In the wounded corneas, an eight mm patch of central corneal epithelium and epithelial BM was removed with a Beaver blade when the patient was under general anesthesia. Immunohistochemical analyses were performed to detect perlecan and nidogen-2 proteins–important components of the epithelial BM lamina lucida and lamina densa zones. Perlecan and nidogen-2 proteins were detected in the BM itself and at low levels in keratocytes in all unwounded corneas. After epithelial injury, both perlecan and nidogen-2 was expressed at high levels in stromal keratocytes, including superficial keratocytes in the early phases of apoptosis. Thus, after epithelial and epithelial BM injury, stromal keratocytes contribute important perlecan and nidogen-2 components to the regenerating epithelial BM.

A scar-like lesion is apparent in basement membrane after wound repair in vivo

“…These results indicate that, like for basement membrane growth, basement membrane repair is accomplished by utilizing soluble matrix proteins that reach damaged basement membranes simply by diffusing within the hemolymph, which bathes the basement membranes of the larval body. Interestingly, in corneal basement membrane wounds, nidogen and perlecan originate from non-epithelial stromal tissues [40], suggesting that the non-autonomy of basement membrane components is not limited to Drosophila .…”

Effect of Photobiomodulation on Wound Healing of the Corneal Epithelium through Rho-GTPase

“…At this phase, metabolic activity was increased and the cellular structure was reorganized for allowing the epithelial cells migration over the wound surface. 4 Additionally, intercellular adherens and gap junctions are also lost, desmosomes are remodeled, and structural proteins and actin filaments are assembled in preparation for cellular migration. 1 The epithelial healing process is referred to as the migration phase, in which cells begin to move and cover the epithelial defect.…”

“…1,2 Rapid healing of the corneal epithelium and the return of an intact basement membrane can restore the eye's normal mechanical barriers and prevent various epithelium-derived growth factors from leaking into the stroma. 3,4 Meanwhile, the use of low levels of visible or nearinfrared (NIR) light for reducing pain, inflammation, and edema, promoting healing of wounds, deeper tissues and nerves, and preventing tissue damage has been known. There are many studies on the use of light aiming to positively stimulate the healing process, but no report about corneal wound healing process.…”

Injury and defective regeneration of the epithelial basement membrane in corneal fibrosis: A paradigm for fibrosis in other organs?

“…Bowman's layer is damaged or destroyed at the site of many pathologies that lead to corneal fibrosis such as photorefractive keratectomy, lacerations, microbial infections, and acid and alkali burns. In any case, if present, Bowman's layer doesn't appear to impede stromal contributions to EBM regeneration since after corneal epithelial scrape injury in humans, that does not injure Bowman's layer, EBM components such as perlecan are produced in large quantities by keratocytes in the subepithelial stroma and likely penetrate Bowman's layer to the site of EBM regeneration [43]. In the corneal ectatic disease keratoconus, many breaks are typically noted in Bowman's layer in advanced cases treated with corneal transplantation [44].…”

“…Myofibroblasts are themselves opaque relative to keratocytes and secrete disordered collagen type 1, collagen type 3 and other matrix materials that disrupt the normal stromal lamellae to produce corneal opacity or scarring. C) Over months to years following the initial injury, keratocytes penetrate the anterior stromal myofibroblasts and facilitate EBM regeneration via the production of laminins, nidogens, and perlecan [38,39,43] in coordination with epithelial cell production of EBM components. We hypothesize that once the nascent laminin-332 layer is produced by the epithelium, more posterior EBM components must, at least in part, be derived from keratocytes to fully regenerate the EBM.…”