A thermo-responsive protein treatment for dry eyes

Abstract

Millions of Americans suffer from dry eye disease, and there are few effective therapies capable of treating these patients. A decade ago, an abundant protein component of human tears was discovered and named lacritin(Lacrt). Lacrt has prosecretory activity in the lacrimal gland and mitogenic activity at the corneal epithelium. Similar to other proteins placed on the ocular surface, the durability of its effect is limited by rapid tear turnover. Motivated by the rationale that a thermo-responsive coacervate containing Lacrt would have better retention upon administration, we have constructed and tested the activity of a thermo-responsive Lacrt fused to an Elastin-like polypeptide (ELP). Inspired from the human tropoelastin protein, ELP protein polymers reversibly phase separate into viscous coacervates above a tunable transition temperature. This fusion construct exhibited the prosecretory function of native Lacrt as illustrated by its ability to stimulate β-hexosaminidase secretion from primary rabbit lacrimal gland acinar cells. It also increased tear secretion from non-obese diabetic (NOD) mice, a model of autoimmune dacryoadenitis, when administered via intra-lacrimal injection. Lacrt ELP fusion proteins undergo temperature-mediated assembly to form a depot inside the lacrimal gland. We propose that these Lacrt ELP fusion proteins represent a potential therapy for dry eye disease and the strategy of ELP-mediated phase separation may have applicability to other diseases of the ocular surface.

TFOS DEWS II Tear Film Report

“…Some biomarkers -all extracellular ones deficient in dry eye - have shown benefits for ocular surface homeostasis and/or tearing in preclinical and, in some cases, clinical situations. Albumin [479], lactoferrin [480] and lacritin [481] each have prosurvival and wound healing activities [479,482]. When applied topically, albumin was reported to provide symptom relief in most dry eye patients with graft versus host disease [483].…”

Lacritin and other autophagy associated proteins in ocular surface health

“…3; (Karnati et al, 2013). Topical recombinant lacritin stimulates tear protein release both in dry eye mice (Vijmasi et al, 2014; Wang et al, 2015) and normal rabbits (Samudre et al, 2011). Similarly, lacritin monomer semi-purified from monkey tears triggers tear lipocalin secretion from monkey lacrimal acinar cells cultured in the presence of dry eye inflammatory cytokines, that under the same conditions are unresponsive to the acetylcholine receptor agonist carbachol (Fujii et al, 2013).…”

“…Ligation of coreceptor syndecan-1 (Ma et al, 2006; Zhang et al, 2013) is necessary for survival signaling (Wang et al, 2013). Recombinant human lacritin is active over a biphasic dose response curve with an optimum of 10 nM in human cell culture (Wang et al, 2006; Wang et al, 2013) and 4 μM (Samudre et al, 2011; Wang et al, 2015) to 20 μM (Wang et al, 2014) in preclinical studies. 1 μM appears to be the dose optimum for monkey tear lacritin applied to monkey lacrimal acinar cells (Fujii et al, 2013).…”

Elastin-like polypeptides: Therapeutic applications for an emerging class of nanomedicines

“…In comparison to a thermally-insensitive ELP control (LS96), LSI induced more profound corneal wound healing over a 12 hr timeframe. More recent data indicates that Lacritin-ELPs are also capable of phase separating in the lacrimal gland, where they mimic the functional effects of free lacritin by promoting tear protein exocytosis [125]. …”