Identification and quantification of thymosin β₄ in human saliva and tears

Thymosin β₄ (Tβ₄) is a ubiquitous, naturally occurring, 43-amino acid peptide that takes part in several biological activities including angiogenesis, inhibition of inflammation,wound healing, chemotaxis, and endothelial cell migration. Recent studies also indicate that Tβ₄ accelerates corneal wound healing and downregulates several proinflamatory chemokines and cytokines. In this study, we sought to determine whether Tβ₄ is naturally occurring in human tears and other human bodily fluids, such as saliva. Tear and saliva samples were analyzed by EIA to identify and quantify the amount of Tβ₄ present. Around 10-20 samples were collected from each of three different age groups: 15-20, 25-35, and >50 years old with n = 30 and n = 60 for tears and saliva, respectively. Exclusion criteria included the use of any topical ophthalmic or topical oral medication and/or history of ocular or oral surgery within the past 6 months. Tears were collected from both eyes using Schirmer's strips. Saliva samples were collected in sterile tubes and were then centrifuged to remove solid particles. Tβ₄ was found in tear and saliva samples in all age groups. The concentrations ranged from 0.5-7 μg/mL in tears and 0.2-3.6 μg/mL in saliva. In both fluids, Tβ₄ concentration varied with age and appeared to peak at ages 25-35 years. Studies are in progress to determine if Tβ₄ levels in saliva and tears demonstrate a circadian rhythm during a 24-h period, as well as to confirm that they vary with age and to explore if they vary with diseased states. This is the first study to report the presence of Tβ₄ in human tears and saliva. This finding raises the possibility that Tβ₄ acts as an endogenous agent contributing to the rapid healing of corneal and oralwounds. Considering that Tβ₄ facilitates reepithelialization and modulates anti-inflammatory mediators, Tβ₄ could potentially be used therapeutically in the treatment of (a) ocular surface disease and injury of eye and (b) various oral disorders, such as periodontal disease.