Sclera as a surrogate marker for determining AGE-modifications in Bruch's membrane using a Raman spectroscopy-based index of aging.

PURPOSE Raman spectroscopy is an effective probe of advanced glycation end products (AGEs) in Bruch's membrane. However, because it is the outermost layer of the retina, this extracellular matrix is difficult to analyze in vivo with current technology. The sclera shares many compositional characteristics with Bruch's membrane, but it is much easier to access for in vivo Raman analysis. This study investigated whether sclera could act as a surrogate tissue for Raman-based investigation of pathogenic AGEs in Bruch's membrane. METHODS Human sclera and Bruch's membrane were dissected from postmortem eyes (n = 67) across a wide age range (33-92 years) and were probed by Raman spectroscopy. The biochemical composition, AGEs, and their age-related trends were determined from data reduction of the Raman spectra and compared for the two tissues. RESULTS Raman microscopy demonstrated that Bruch's membrane and sclera are composed of a similar range of biomolecules but with distinct relative quantities, such as in the heme/collagen and the elastin/collagen ratios. Both tissues accumulated AGEs, and these correlated with chronological age (R(2) = 0.824 and R(2) = 0.717 for sclera and Bruch's membrane, respectively). The sclera accumulated AGE adducts at a lower rate than Bruch's membrane, and the models of overall age-related changes exhibited a lower rate (one-fourth that of Bruch's membrane) but a significant increase with age (P < 0.05). CONCLUSIONS The results suggest that the sclera is a viable surrogate marker for estimating AGE accumulation in Bruch's membrane and for reliably predicting chronological age. These findings also suggest that sclera could be a useful target tissue for future patient-based, Raman spectroscopy studies.

[1]  R. Moses,et al.  Elastin content of the scleral spur, trabecular mesh, and sclera. , 1978, Investigative ophthalmology & visual science.

[2]  I. W. Levin,et al.  Evidence for acyl chain trans/gauche isomerization during the thermal pretransition of dipalmitoyl phosphatidylcholine bilayer dispersions. , 1981, Biochimica et biophysica acta.

[3]  K. Meek,et al.  The inhibition of sugar-induced structural alterations in collagen by aspirin and other compounds. , 1994, Biochemical and biophysical research communications.

[4]  K. Meek,et al.  The effect of glycation on charge distribution and swelling behaviour of corneal and scleral collagen , 1996 .

[5]  H F Edelhauser,et al.  Human sclera: thickness and surface area. , 1998, American journal of ophthalmology.

[6]  R. Guymer,et al.  Changes in Bruch’s membrane and related structures with age , 1999, Progress in Retinal and Eye Research.

[7]  J. Rada,et al.  Proteoglycan composition in the human sclera during growth and aging. , 2000, Investigative ophthalmology & visual science.

[8]  Alan W. Stitt,et al.  Advanced glycation: an important pathological event in diabetic and age related ocular disease , 2001, The British journal of ophthalmology.

[9]  H. Barr,et al.  Medical applications of Raman spectroscopy: from proof of principle to clinical implementation. , 2002, Biopolymers.

[10]  J. S. Rada,et al.  Interaction of lumican with aggrecan in the aging human sclera. , 2004, Investigative ophthalmology & visual science.

[11]  J. Beattie,et al.  Effect of excitation wavelength on the Raman spectroscopy of the porcine photoreceptor layer from the area centralis. , 2005, Molecular vision.

[12]  A. Dawnay,et al.  Advanced Glycation End Product Free Adducts Are Cleared by Dialysis , 2005, Annals of the New York Academy of Sciences.

[13]  C. Krafft,et al.  Biomedical applications of Raman and infrared spectroscopy to diagnose tissues , 2006 .

[14]  J. Renwick Beattie,et al.  Prediction of adipose tissue composition using raman spectroscopy: Average properties and individual fatty acids , 2006, Lipids.

[15]  John J. McGarvey,et al.  Raman microscopy of porcine inner retinal layers from the area centralis , 2007, Molecular vision.

[16]  Claus Borggaard,et al.  Classification of Adipose Tissue Species using Raman Spectroscopy , 2007, Lipids.

[17]  M. Boulton,et al.  Confocal Raman microscopy can quantify advanced glycation end product (AGE) modifications in Bruch's membrane leading to accurate, nondestructive prediction of ocular aging , 2007, FASEB journal : official publication of the Federation of American Societies for Experimental Biology.

[18]  A. Pawlak,et al.  Advanced Glycation as a Basis for Understanding Retinal Aging and Noninvasive Risk Prediction , 2008, Annals of the New York Academy of Sciences.

[19]  Werner Gellermann,et al.  Resonance Raman imaging of macular pigment distributions in the human retina. , 2008, Journal of the Optical Society of America. A, Optics, image science, and vision.

[20]  J. Marshall,et al.  Human transscleral albumin permeability and the effect of topographical location and donor age. , 2008, Investigative ophthalmology & visual science.

[21]  Anna Pawlak,et al.  Raman spectroscopy of advanced glycation end products (AGEs), possible markers for progressive retinal dysfunction , 2008 .

[22]  M. Bottlang,et al.  Scleral biomechanics in the aging monkey eye. , 2009, Investigative ophthalmology & visual science.

[23]  John J. McGarvey,et al.  Effect of signal intensity normalization on the multivariate analysis of spectral data in complex `real-world' datasets , 2009 .

[24]  J. Stewart,et al.  Exogenous collagen cross-linking reduces scleral permeability: modeling the effects of age-related cross-link accumulation. , 2009, Investigative ophthalmology & visual science.

[25]  J. Glenn,et al.  The role of advanced glycation end products in retinal ageing and disease. , 2009, Biochimica et biophysica acta.

[26]  A. Pawlak,et al.  Multiplex analysis of age-related protein and lipid modifications in human Bruch's membrane. , 2010, FASEB journal : official publication of the Federation of American Societies for Experimental Biology.

[27]  J. Renwick Beattie,et al.  Optimising reproducibility in low quality signals without smoothing; an alternative paradigm for signal processing , 2011 .