TSG-6 controls transcription and activation of matrix metalloproteinase 1 in conjunctivochalasis.

PURPOSE: To investigate the role of anti-inflammatory TSG-6 in controlling MMP-1 and MMP-3, which have been shown to be upregulated in conjunctivochalasis (CCh).

METHODS: Immunostaining of TSG-6 was compared between normal and CCh conjunctiva and Tenon's capsule. Second cultures of normal and CCh fibroblasts were transfected with or without TSG-6 siRNA and then with or without the addition of TNF-α or IL-1β. Cell lysates and culture media were collected to assess apoptosis with the use of ELISA and the expression of TSG-6, MMP-1, and MMP-3 transcripts and proteins with the use of qRT-PCR and Western blot analysis, respectively.

RESULTS: TSG-6 expression was constitutive in the in vivo normal conjunctival epithelium. Significantly more TSG-6-positive cells than normal specimens were noted in CCh subconjunctival tissue and Tenon's capsule. TSG-6 was constitutively expressed intracellularly by both resting normal and CCh fibroblasts but was secreted extracellularly only by resting CCh fibroblasts. Intracellular and extracellular TSG-6 proteins were markedly upregulated by TNF-α or IL-1β in normal and CCh fibroblasts. Active MMP-1 was found in CCh fibroblasts intracellularly and extracellularly, whereas only proMMP-1 was found intracellularly in normal fibroblasts. Knockdown by TSG-6 siRNA upregulated more MMP-1 than MMP-3 transcripts in normal and CCh fibroblasts. TSG-6 siRNA led to extracellular MMP-1 expression by normal fibroblasts such as CCh fibroblasts. This activation of MMP-1 was further enhanced by IL-1β. Cell apoptosis was higher in CCh fibroblasts and further aggravated by TSG-6 siRNA knockdown.

CONCLUSIONS: TSG-6 exerts an anti-inflammatory function by counteracting the transcription of MMP-1 and MMP-3 and the activation of MMP-1. Dysfunction of TSG-6 might play a role in the pathogenesis of CCh.