The matricellular protein CCN1 mediates neutrophil efferocytosis in cutaneous wound healing

Abstract

Neutrophil infiltration constitutes the first step in wound healing, although their timely clearance by macrophage engulfment, or efferocytosis, is critical for efficient tissue repair. However, the specific mechanism for neutrophil clearance in wound healing remains undefined. Here we uncover a key role for CCN1 in neutrophil efferocytosis by acting as a bridging molecule that binds phosphatidylserine, the “eat-me” signal on apoptotic cells, and integrins αvβ3/αvβ5 in macrophages to trigger efferocytosis. Both knockin mice expressing a mutant CCN1 that is unable to bind αvβ3/αvβ5 and mice with Ccn1 knockdown are defective in neutrophil efferocytosis, resulting in exuberant neutrophil accumulation and delayed healing. Treatment of wounds with CCN1 accelerates neutrophil clearance in both Ccn1 knockin mice and diabetic Leprdb/db mice, which suffer from neutrophil persistence and impaired healing. These findings establish CCN1 as a critical opsonin in skin injury and suggest a therapeutic potential for CCN1 in certain types of non-healing wounds.

CCN1/CYR61-mediated meticulous patrolling by Ly6C low monocytes fuels vascular inflammation

“…Therefore, platelets have at least three functions in our model: (i) recruitment of Ly6C low monocytes; (ii) commitment to meticulous patrolling of Ly6C low monocytes; and (iii) promotion of cytokine production by Ly6C low monocytes via direct interaction and/or release of CCN1. Matricellular protein CYR61/CCN1 has been studied extensively in cancer development and wound healing (15,16,47,48). In addition to confirming the chemoattractant properties of CCN1 on monocytes/macrophages (18, 20, 21), we also show that CCN1 sustains the patrolling of Ly6C low monocytes and is important for the initiation of inflammation.…”

Human fibrocyte-derived exosomes accelerate wound healing in genetically diabetic mice

“…Western blot analysis of the expression of CK-14 at this time point showed a marked dose-dependent enhancement of the immunoreactivity for the keratinocyte marker in exosome-treated wounds (Fig. 3D), reflecting an accelerated re-epithelialization of the wounds [41]. Thus, the results of this proof-of-concept study suggest that the use of fibrocytes-derived exosomes for the treatment of diabetic ulcers may be feasible.…”

Recombinant CCN1 prevents hyperoxia-induced lung injury in neonatal rats

“…And this may be partially related to the ability of CCN1 to increase efferocytosis of neutrophils, as has been described for wound tissue (16). But, to further investigate CCN’s anti-inflammatory activity we also examined lung levels of inflammasome-related proteins.…”

“…Recombinant CCN1 (1 mg/kg) or placebo (equal volume) was administered by intraperitoneal (ip) injection on day 1, day 4, day 7 and day 9 during continuous room air or hyperoxia exposure. Murine recombinant CCN1 was produced using a baculovirus expression system and chromatographically purified (16) and the dose was used as referenced previously (17). Animals were sacrificed on day 11.…”

“…CCN1 largely exerts its anti-fibrotic effect by promoting cellular senescence and apoptosis and by attenuating TGF-β signaling (15, 17, 21). In addition, it has been recently demonstrated that CCN1 plays an important down-regulatory role in the early inflammatory phase of wound healing by stimulating the clearance of neutrophils via the process of efferocytosis (16). And CCN1 promotes angiogenesis by increasing VEGF receptor 2 (VEGFR2) expression, enhancing endothelial cell adhesion, migration and survival (18, 22).…”