Abstract
Junctional adhesion molecule-A (JAM-A) belongs to the immunoglobulin superfamily, it predominantly exists at the tight junctions of epithelial and endothelial cells. JAM-A is known to regulate leukocyte trans-endothelial migration, however, how it affects the proliferation and migration of keratinocytes, the two essential steps during wound healing, has less been explored. In this study, we showed that JAM-A was significantly expressed in normal skin epidermis. RNAi-mediated JAM-A knockdown remarkably promoted the proliferation and migration of keratinocytes. We also found that loss of JAM-A increased the protein levels of p-FAK, p-Erk1/2, and p-JNK; however, FAK inhibitor PF-562271 restrained the expression of p-FAK and p-Erk1/2 elevated by JAM-A RNAi, but not p-JNK, and also slowed down keratinocyte proliferation and migration. Finally, in a rat wound model we showed that absence of JAM-A significantly promoted the wound healing process, while the use of PF-562271 or Erk1/2 inhibitor PD98059 repressed those effects. These data collectively demonstrate that suppressing JAM-A expression could promote the proliferation and migration of keratinocytes and accelerate the healing process of rat skin wounds, potentially via FAK/Erk pathway, indicating that JAM-A might serve as a potential therapeutic target for the treatment of chronic refractory wounds.
Highlights
The process of skin wound healing is well organized by multiple factors
Junctional adhesion molecule-A (JAM-A) predominantly exists in the epidermis of normal human skin It is known that JAM-A could regulate leukocyte transendothelial migration, we are curious about if JAM-A plays a role during the healing process
Immunohistochemistry (IHC) staining on paraffin sections of normal human skin showed that JAM-A predominantly located at the epidermal part of the skin, and concentrated at cell–cell interface, which coincides with previous reports that JAM-A is a putative tight junction protein, while JAM-A was absent in the dermis (Fig. 1c)
Summary
Re-epithelialization, a key step during wound healing, relies on two essential behaviors of keratinocytes: proliferation, and migration[1]. Junctional adhesion molecule-A (JAM-A, previously referred as JAM-1) is a 36-kD trans-membrane molecule and locates at tight junctions, which are formed between two adjacent epithelial or endothelial cells[2]. JAM-A has been implicated to participate in leukocyte migration across the endothelium[3], potentially via mitogen-activated protein kinase (MAPK) and/or focal adhesion kinase (FAK)mediated pathways, which are necessary for migration[4]. It is unknown whether JAM-A takes part in keratinocyte migration and cutaneous wound healing, and if so, which signaling is involved in these processes. JAM-A engaged in the formation of tight junctions and helps maintain the integrity of epithelia and endothelia[6,7]; JAM-A was found to accept certain sub-strains of the reovirus and promotes their invasion into cells[8]; JAM-A was show to act as a ligand during leukocyte migration across the endothelia[3]
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