gms | German Medical Science

Age-related macula degeneration (AMD) is a leading cause of severe visual impairment in developed countries. The vision loss associated with AMD is the result of degenerative changes in the central region of the retina without real therapeutic approaches. Cross linking has been suggested as one of the mechanisms involved in the aging process. Among the various cross linking reactions, tissue transglutaminase II (tTG) catalyzed cross linking activity plays a role in aging. We investigated the age related expression and activity of tTG and its reaction product epsilon-gamma-glutamyl lysine (e-g) bonds.

The posterior pole of one couple of 12 eyes of human donors ranging from 18 to 80 years was preserved. Localization of tTG and its reaction product e-g was investigated immunohistochemically. The retinal pigmentepithelium (RPE) from the other 12 eyes was analyzed for tTG expression by RT-PCR and Western blot analysis.

A faint staining of tTG was observed in RPE of donors until the age of 36. The RPE of older donors showed a marked staining. RT-PCR analysis demonstrated an increase of mRNA expression in the RPE of old eyes about 3 fold. Western blot analysis showed a 4 fold expression of tTG compared to young donors. This increased activity was accompanied by an increased expression of e-g bonds in the RPE as well in Bruch´s membrane.

An increased expression and activity of tTG was demonstrated during the aging process of the RPE. These findings may play an important role in age-related diseases such as macular degeneration.