Omental tissue is a highly vascularized organ and a rich source of angiogenic factors. A new omental dissection method was designed. The greater omentum consists of a thin double layer of mesothelial cells that is attached to the greater gastric curvature. It folds back on itself and returns to the transverse colon and reaches beyond to the posterior peritoneum. Rat omental pedicle was excised and characterized by immunohistochemical staining. It showed that omental tissue is rich in laminin (green-labeled tissues, Figure 1A) because it was strongly immunoreactive to laminin. Laminin is a glycoprotein which is a constituent of basement membranes [19]. It is also found to promote neuron axonal regeneration after injury [20]. Omental tissue is known to be rich in vascular endothelium. In the present study, the RECA-1-immunoreactive cells (red color, Figure 1B) could be detected. Under the microscope, the rat omentum was marked obviously with laminin and RECA-1. We also found that the omentum is rich in adipocytes, which have a lower density and can be suspended in PBS after centrifugation. This characteristic is quite similar to that of fat tissue (Figure 1).

Traumatic injury to spinal cord initiates a series of cellular and molecular events. Early intervention may limit the extent of tissue injury. Because no resorption of the omentum occurs, it is necessary to trim all tissue and use only the amount necessary to reconstruct the wound. The vascular anatomy of the omentum permits the isolation of a flap within the major omental graft. A piece of omentum graft was implanted to the injury epicenter immediately after eliciting severe contusive SCI in the rats. The hindlimb performance of these SCI rats was monitored weekly up to 6 weeks post-injury. The time course of hindlimb locomotor recovery (the BBB score) in SCI rats treated with saline or omental graft was recorded (Figure 2). Beginning 3 weeks post-treatment onward, the omentum-grafted SCI rats maintained significantly higher BBB scores, indicating functional recovery throughout 6 weeks post-injury (from the 3rd to the 6th week, 5.0 vs. 8.2, 5.2 vs. 8.3, 5.3 vs. 8.4, 5.5 vs. 8.6, p < 0.05, respectively).

At 6 weeks post-injury, the two groups of contusive SCI rats with or without omentum graft were anesthetized and perfused intravascularly with 4% paraformaldehyde. The thoracic regions of the spinal cords were sectioned in the sagittal plane (10 µm thick) and processed for hematoxylin and eosin (H&E) staining as well as IHC. The result showed that the omental graft better preserved the injured spinal cord, compared to SCI without treatment (Figure 3). The quantitative results of H&E staining showed that the omental graft significantly reduced the cavity (43.9 ± 2.1 vs. 24.4 ± 3.0, p < 0.05) in the injured epicenter of the spinal cord (Figure 3B). Further histological assessment with immunofluorescent class III β-tubulin staining in longitudinal spinal cord sections was consistent with the results of H&E staining. As shown in Figure 4, the omentum-grafted contused rats had higher axonal densities in the lesions at 6 weeks after SCI (Figure 4B3 compared to Figure 4A3). Quantitative stereological analysis of tissue areas (areas 2, 3, 4) revealed a significant difference in area 3 (9.9 ± 2.3 vs. 17.2 ± 1.4, p < 0.05) among the samples studied (Figure 4C–E). The omentum-grafted rat spinal cords possessed more preserved class III β-tubulin (+) nerve fibers than those of contusive SCI rats without treatment.