¹H NMR Spectroscopy Characterization of Porcine Vitreous Humor in Physiological and Photoreceptor Degeneration Conditions

Abstract

Citation: Elmi A, Ventrella D, Laghi L, et al. 1 H NMR spectroscopy characterization of porcine vitreous humor in physiological and photoreceptor degeneration conditions. Invest Ophthalmol Vis Sci. 2019;60:741-747. https://doi.org/10.1167/iovs. PURPOSE. Qualitative and quantitative analysis of vitreous humor (VH) is important to discriminate between physiological and pathological conditions and may be particularly helpful when using animal models for ophthalmologic research. The aim of the present study was to investigate the physiological qualitative/quantitative composition of the VH of the standard pig using a metabolomics approach based on 1 H nuclear magnetic resonance (NMR) spectroscopy. A secondary aim was the characterization of the VH of the porcine model of photoreceptor degeneration induced with iodoacetic acid (IAA), widely used in the biomedical field, and comparison with the physiological one.METHODS. VH samples were collected from 30 pigs (17 in the physiological condition and 13 treated with IAA) upon vitrectomy and analyzed by means of 1 H NMR spectroscopy for characterization. RESULTS.On all analyzed samples, 40 molecules could be identified and quantified, with lactate being the most abundant in both physiological and photoreceptor degeneration conditions. Upon comparison, only 17 molecules showed statistical differences: In the IAA group, glucose and glutamine increased, while lactate, 4-amynobutyrate, hypoxanthine, dicarboxylic acids (succinate and fumarate), amino acids with their derivatives (creatine, alanine, valine, lysine, leucine, glycine, taurine, and isoleucine), and choline with its precursor sn-glycero-3phosphocholine decreased.CONCLUSIONS. The results validate the metabolic impairment determined by glycolysis inhibition upon systemic IAA administration. In conclusion, this work represents the first characterization of the porcine VH metabolome in physiological conditions and provides additional information for the characterization and refinement of the IAA-induced photoreceptor degeneration model. T he vitreous humor (VH) is a highly hydrated (>98%)jellified extracellular matrix mainly constituted by different types of collagen fibrils, 1 in particular II, V/XI, IX, 2 and hyaluronan, a nonsulphate glycosaminoglycan (GAG) structure that fills the spaces between collagen fibrils. 3 The VH is considered to be virtually acellular except for the presence of a small number of hyalocytes. 4 When looking at its anatomic features, VH is enclosed in and attached to the pars plana of the retina and makes contact with the lens. 5 VH has different functions including mediating the metabolic requirements of the lens, stopping the leakage of cells and large macromolecules from the vascular stream into the vitreous cavity, 6 and acting as a diffusional barrier to the free movement of molecules between the anterior and posterior eye. 7 Furthermore, VH seems to act as a reservoir for several compounds unable to cross the blood-retinal barrier (BRB) such as proteins and other solutes. 8 In recent d...

The porcine iodoacetic acid model of retinal degeneration: Morpho-functional characterization of the visual system

“…Inhibition of glycolysis and cell stress, confirmed by 1H-NMR vitreous humor characterization in pigs after 30 days of IAA treatment (Elmi et al, 2019), may provoke three types of events: apoptosis, necrosis or autophagy. Further investigations of the mechanisms of cell death could elucidate the toxic effect of IAA on photoreceptor degeneration.…”

Biocompatibility of a Conjugated Polymer Retinal Prosthesis in the Domestic Pig

“…Domestic pigs were weighted and sedated with an intramuscular (IM) injection of Tiletamine-Zolazepam (Zoletil, Virbac, Prague, Czechia) (5 mg/kg). After 15 min, general anesthesia was induced with 8% sevoflurane (SevoFlo, Esteve, Barcelona, Spain), administered through a mask in a 1:1 oxygen/air mixture and maintained with the same halogenated agent (3%) after orotracheal intubation (Elmi et al, 2019). Lactated Ringer infusion was set at a rate of 10 ml/kg/h through the auricular vein (left ear).…”

Branched-Chain Amino Acids Metabolism and Their Roles in Retinopathy: From Relevance to Mechanism

“…Except for the retina, BCAAs were significantly increased in the serum [31,47] and plasma [29] of DR rats. Elmi et al [48] collected vitreous humor from pigs treated with iodoacetic acid (IAA), the porcine model of photoreceptor degeneration. Their results showed that BCAAs were decreased in the vitreous humor in the IAA group, compared to physiological conditions.…”