Eyeworld

EW NEWS & OPINION 26 February 2016 by Matt Young and Gloria D. Gamat EyeWorld Contributing Writers of goat vitreous humour at various time points (0, 6, 12, 18, and 24 hours) after death using a metabolo- mic approach. "The major time-related com- positional changes, here detected, were the increase of lactate, hypox- anthine, alanine, total glutathione, choline/phosphocholine, creatine, and myo-inositol and the decrease of glucose and 3-hydroxybutyrate," the research team reported. Metabolomic profiling, empha- sized Rosa and colleagues, is a pow- erful tool in determining ongoing differences in the composition of vitreous humour. This knowledge, they noted, may be utilized in the future in investigating various phys- iological and pathological condi- tions. "These results strengthen the hypothesis that the ongoing me- tabolomic profile, described in our animal model, may be representative of the energy metabolism derange- ment secondary to death and may be applied to human samples," they reported. Using a similar approach, an earlier study explored the metabo- lomic signature of different topo- graphical areas of the vitreous hu- mour in an animal model. Reporting in the May 2014 issue of PLoS One, Locci and colleagues described that a unique metabolomic signature be- longing to each area of the vitreous humour was observed. Other related studies As the biochemistry of the human vitreous becomes fully understood, its physiological and pathological role in vitreoretinal disorders will be more appreciated. For example, in the February 2015 issue of Proteomics Clinical Applications, Monteiro and col- leagues reported the diverse protein components present in the vitreous humour that can influence retinal physiology. This includes growth factors, hormones, transporter pro- teins, and enzymes. "The protein composition of vit- reous humour has been described as being altered in a number of disease states," Monteiro and colleagues re- ported. "Therefore, attempts aiming at establishing a map of vitreous humour proteins and detecting pu- tative biomarkers for ocular illness or protein fluctuations with puta- tive physiologic significance were conducted over the last two decades, using proteomic approaches." Therapeutic targets derived from vitreous humour proteomics, accord- ing to Monteiro and colleagues, are those related to vasoproliferative fac- tors appearing in the vitreous, which are implicated in neovascularization and also fibrovascular proliferation of the retina during ocular disease. In the January 2015 issue of BioMed Research International, Rosa and colleagues reported findings on metabolite composition profiles logical values for vitreous sodium, potassium, chloride, calcium, mag- nesium, glucose, lactate, osmolality, and beta-hydroxybutyrate, and has implications for characterizing the changes that occur in the vitreous profile in the event of diseases. "We have described the normal concentration of sodium, potassi- um, chloride, calcium, magnesium, glucose, lactate, osmolality, and beta-hydroxybutyrate within human vitreous humour in vivo," the re- searchers reported. "The vitreous of males and females are very similar; diabetic vitreous is significantly lower in magnesium and higher in glucose," they added. According to Dr. Kokavec, further research will determine the role of vitreous biochemistry on the presence and development of ocular disease, as a diagnostic marker of systemic disease, and on the chemi- cal stability of intravitreal therapeu- tic agents currently available. "The vitreous and serum have significant differences in sodium, potassium, chloride, calcium, glucose and lactate concentration; significant differences in vitreous sodium, potassium, chloride, cal- cium, magnesium and lactate were found between our data and that within Adler's Physiology of the Eye (11th edition)," the team reported at RANZCO. The biochemical makeup of the human vitreous is pinpointed for the first time A mong the structural components of the eye, the vitreous occupies the most space. Its appear- ance and composition, which change with age, have critical consequences to ocular health and disease. However, due to its invisible na- ture and gel-like structure, studying the biochemistry and pathophysi- ology of the vitreous humour has proved to be complicated in the past. Findings from animal studies reported in recent years have shed light on the physiology and patho- biology of the eye, leading to the evolution of therapeutic modalities capable of reducing the incidence of blindness. Establishing the composition of human vitreous At the 2015 annual scientific con- gress of the Royal Australian and New Zealand College of Ophthal- mologists (RANZCO) in Wellington, New Zealand, a team of experts from the South Australian Institute of Ophthalmology (SAIO), University of Adelaide, Australia, presented their findings on the composition of the normal human vitreous based on average patient data. "We have undertaken an obser- vational study to determine the nor- mal biochemical profile of vitreous humour," said Jan Kokavec, MBBS, BSc, clinical associate lecturer, University of Adelaide, Australia. Their findings, Dr. Kokavec said, have highlighted significant differ- ences between the composition of normal human vitreous humour and that of a popular vitreous substi- tute, BSS Plus (Alcon, Forth Worth, Texas). "Moreover, our research has identified significant differences between the vitreous composition of diabetics and non-diabetics," he added. Popularly known estimates of the composition of the human vitreous humour originate from 1960s animal studies. Current data from the SAIO team has established the physio- There is more to the human vitreous than "protects the eye" In the study, the vitreous samples were frozen until analysis. Source: Jan Kokavec, MBBS, BSc

• Cover