LAIR-1 expression and its intrinsic function is normal in patients with systemic sclerosis.

LAIR-1 binds to in vitro and in vivo fibrotic extracellular matrix.

Fibrotic collagen products have compromised capacity to activate LAIR-1.

Absence of LAIR-1 in the bleomycin model for systemic sclerosis leads to increased skin fibrosis.

A functional LAIR-1 in patients with fibrotic diseases suggests a therapeutic opportunity to control fibrosis.

Tissue repair is disturbed in fibrotic diseases like systemic sclerosis (SSc), where the deposition of large amounts of extracellular matrix components such as collagen interferes with organ function. LAIR-1 is an inhibitory collagen receptor highly expressed on tissue immune cells. We questioned whether in SSc, impaired LAIR-1-collagen interaction is contributing to the ongoing inflammation and fibrosis.

We found that SSc patients do not have an intrinsic defect in LAIR-1 expression or function. Instead, fibroblasts from healthy controls and SSc patients stimulated by soluble factors that drive inflammation and fibrosis in SSc deposit disorganized collagen products in vitro, which are dysfunctional LAIR-1 ligands. This is dependent of matrix metalloproteinases and platelet-derived growth factor receptor signaling.

In support of a non-redundant role of LAIR-1 in the control of fibrosis, we found that LAIR-1-deficient mice have increased skin fibrosis in response to repeated injury and in the bleomycin mouse model for SSc. Thus, LAIR-1 represents an essential control mechanism for tissue repair. In fibrotic disease, excessive collagen degradation may lead to a disturbed feedback loop. The presence of functional LAIR-1 in patients provides a therapeutic opportunity to reactivate this intrinsic negative feedback mechanism in fibrotic diseases.

Fibrosis

Systemic sclerosis

LAIR-1

CD305

Collagen

Tissue repair

© 2024 The Authors. Published by Elsevier Ltd.