Targeting Cx26 Expression by Sustained Release of Cx26 Antisense from Scaffolds Reduces Inflammation and Improves Wound Healing

Abstract

The gap junction protein connexin 26 (Cx26) is expressed at high levels in naturally hyperthickened epidermal layers as well as pathological hyperkeratotic disease states, such as warts, psoriatic plaques, and chronic wound edges. The overexpression of Cx26 is also linked with inflammation, breakdown of the skin barrier function, and perturbed wound healing. Here, a collagen scaffold implanted into a rat excisional skin wound is used. This induces a foreign body type reaction characterized by epidermal thickening with elevated levels of Cx43 and Cx26, increased inflammation, and perturbed healing. This is reminiscent of a chronic skin wound. If the same scaffolds are coated with an antisense molecule specifically targeting Cx26 that has a slow sustained release, this prevents the abnormal upregulation of Cx26 protein at the wound edge. Knocking down Cx26 protein levels below those seen in normal wound healing has no adverse effects on the healing process but instead reduces the epidermal thickening and also the inflammatory response, while at the same time promotes the healing response. Treatment with Cx43/26 antisense may promote healing of chronic wounds. The Cx26 antisense may also be helpful in treating other skin conditions where Cx26 is overexpressed.

Connexins and the Epithelial Tissue Barrier: A Focus on Connexin 26

“…Up-regulation of CX26 is a characteristic of hyperproliferative epidermis in physiological conditions, such as vaginal and buccal epithelium, which shows a high proliferation rate, and pathological conditions, such as psoriatic epidermis, chronic non-healing wounds epidermis and viral warts [ 93 , 94 , 95 , 96 ]. CX26 expression is also induced during wound healing and skin hyperplasia stimulated by tumor promoters [ 40 ].…”

“…After 6 h of injury, CX43 is down-regulated in keratinocytes and fibroblast at the wound edge to allow cell migration followed by recovery of CX43 levels [ 95 ]. In contrast, CX26 and CX30 are up regulated in keratinocytes until the wound is closed [ 96 , 98 , 99 ] in the granular cell layer near the wound margins and in the basal cell layer at some distance from the wound [ 95 ]. Thus, Connexins play a pivotal role in a variety of aspects of the acute wound healing process and each step is associated with a different connexin environment [ 51 ].…”

“…This was successfully taken forward by Professor Colin Green and colleagues to clinical trials with exciting evidence in wound healing scenarios (https: //ocunexus.com/nexagon). Recently antisense technologies targeting CX26 were reported to reduce pro-inflammatory ATP release within the skin and were beneficial in in vivo wound healing studies, preventing CX26 upregulation at the wound edge, reducing inflammation, epidermal thickening and improving wound closure events [96]. Short connexin mimetic peptides targeting CX43, based on the original work pioneered by Professor Howard Evans and colleagues during the 1990s, provided a platform for peptide design effectively inhibiting both Gap Junction and Connexin hemichannels activity.…”

Cell Membrane-Coated Electrospun Fibers Enhance Keratinocyte Growth through Cell-Type Specific Interactions

“…The results from both studies suggest that the cell membrane coatings promote proliferation instead of attachment. As keratinocytes play an important role in re-epithelialization and have been targeted for wound healing and skin tissue engineering, , this platform can synergize with the current approaches that use electrospun fiber scaffolds to promote skin regeneration. , …”

Dysregulation of Connexin Expression Plays a Pivotal Role in Psoriasis

“…In the present study, we showed that the connexin mimetic peptide GAP27 that primarily inhibits Cx43 signalling reduced PGN-evoked cytokine release in adult fibroblasts that predominantly express CX43, further supporting strategies that target connexins’ therapeutic potential for chronic inflammatory conditions [ 43 ]. Antisense technologies targeting both Cx43 and Cx26 have reported benefits in in vivo wound healing studies, and a recent report by Becker and colleagues suggests that preventing upregulation of CX26 reduces inflammation and epidermal thickening [ 53 ]. Further studies are now warranted to explore if targeted inhibition of CX26 and CX30 in keratinocytes hold therapeutic benefit for psoriasis.…”