Identification of Trauma-Related Biomarkers Following Blast Injuries to the Eye

Abstract

 

Purpose

 

Injuries to neural tissue result in the expression of specific biomarkers, due to the activation of repair processes or apoptotic signaling pathways. In the case of blast injuries to the eye, detection of these biomarkers may provide useful metrics for diagnosis, prognosis, and therapy. The present investigation is designed to use matrix assisted laser desorption ionization time of flight (MALDI/TOF) to identify protein biomarkers in the eyes of animal models exposed to calibrated blasts from a shock tube.

 

Methods

 

To prepare for live animal experiments, ex vivo porcine eyes were commercially obtained and exposed to blasts produced by a 17” diameter shock tube, with peak pressure ranging from 48.3 to 151.5 kPa and positive pulse duration from 2.1 to 2.8 ms, depending on the number of aluminum disks placed between the driver chamber and the expansion chamber. Following blast or sham exposure, ocular samples were flash frozen and cut into 20-µm thick sections. The sections were transferred to indium titanium oxide-coated slides and coated with sinapinic acid as the matrix agent. Protein signatures were detected in these sections over a range of 7,000 to 50,000 m/z using a Bruker Daltonics Ultraflextreme MALDI/TOF.

 

Results

 

The optic nerves of the eyes were probed with the laser set to 28% of maximum power. A representative mass spectrum obtained from a control eye (not subjected to a blast) is shown in Fig 1, while a spectrum obtained from an eye subjected to a blast of 120.9 kPA peak pressure and 2.5 ms duration is shown in Figure 2.

 

Conclusions

 

The spectra from the control eye (Figure 1) and eye subjected to blast trauma (Figure 2) are similar, but not identical. There is a peak at m/z = 37,500 in the control eye that is not present in the blast-subjected eye, and there is a sharp peak at m/z = 12,200 present only in the blast eye. Because ex vivo tissue would not be expected to express new proteins, these differences are unlikely to result from blast effects, but rather may represent variations between ocular samples or perhaps the specific metabolic state or stress level of the animals when slaughtered. Nevertheless, these results indicate this experimental approach has the sensitivity to detect trauma-induced biomarkers. Ongoing work is directed at the identification of the specific proteins observed in the MALDI spectra.

 

 

Figure 1. MALDI spectrum from control eye.

 

 

Figure 2. MALDI spectrum from blast eye.

 

Keywords: 742 trauma • 637 pathology: experimental • 629 optic nerve