Abstract
Purpose: :
To identify the effect of PGF2α and matrix metalloproteinases (MMPs) in the degradation of collagen in human and porcine sclera.
Methods: :
Tissue explants excised from the posterior sclera of either porcine or human globes were incubated at 37oC in either serum–free DMEM/Hams F10 media containing 100nM PGF2α, serum–free media (Control) or MMP–enriched media for 6, 12, 24, 48 and 72 hours. The effect of these treatments on the architecture of the scleral collagen was analysed by x–ray diffraction studies. High–angle X–ray diffraction patterns were obtained using a Bruker AXS Nanostar small angle scattering station with a camera length of 4.4cm, which allowed the wide angle diffraction features of collagen to be observed to a resolution of 0.2nm. A 0.154nm X–ray beam is generated by a Kristalloflex 760 X–ray generator (Bruker AXS, Germany) and focused using cross–coupled Göbel mirrors and a 3–pinhole collimation system. A HI–STAR 2d detector and SAXS software was used for data collection.
Results: :
X–ray diffraction analysis allowed the integrity of the collagen helix to be examined in scleral tissue. The characteristic helical diffraction peak at a spacing of 0.268nm provided evidence of the intact collagen. The scatter, centred at 0.35nm, gave an indication of increased gelatinisation in human scleral samples. Integration of the peaks allowed analysis of the collagen:gelatin ratio. During the time course of treatment, gelatinisation occurred within the tissue samples treated with both MMP–enriched media and prostaglandin. This process appeared to be more acute in human sclera compared to porcine: occurring after 24 hours of incubation in human tissue and over a period of 72 hours in porcine tissue. The same degree of gelatinisation was not observed in control media.
Conclusions: :
Scleral collagen appears to undergo alterations in its architecture as a result of PGF2α and MMP treatment. This is consistent with previous studies that suggest a role for PGF2α in the activation of MMPs and the augmentation of aqueous uveoscleral outflow pathway. The targeting of MMP activity has great potential for a future therapeutic intervention in glaucoma.
Keywords: extracellular matrix • enzymes/enzyme inhibitors • anterior chamber