Experimental Study Of The Eyelid Reconstru-ction In Situ With The Acellular Xenogeneic Dermal Matrix

ObjectiveThe ophthalmol plastic reconstruction surgery needs various kinds of repairing materials; the reserved allogeneic sclera is one of the most popularly used materials. However, the allogeneic sclera source is limitied, the application cost is relatively high, and it is hard to obtain the sclera from hospitals without eye banking facilities. In addition, the allogeneic sclera transplant has the risk of infection. Therefore it is necessary to seek a more economical for the ophthalmol plastic reconstruction surgery.The acellular xenogeneic dermal matrix (Xeno-ADM) is a kind of dermis substitute obtained from xenogeneic porcine skin with special handling to remove its cell components. During the manufacturing process of Xeno-ADM, the epidermis, the cell and the antigenicity are removed; the complete and continued basement membrane and dermis collagen network were kept in the papillary layer to keep its normal arrangement and tension fiber. The Xeno-ADM is one of the important research projects in recent years. This experiment focused on using Xeno-ADM to replace the tarsal cartilages in the analogue of rabbit eyelid defect and to perform the eyelid reconstruction in situ. With the evidence from the histology and cytology experiment, Xeno-ADM proved to be a substitute of palpebral cartilages for clinical use, which provides the verification to broaden the application of the Xeno-ADM in ophthalmology.MethodThirty-six New Zealand rabbits were divided into two groups randomly. Establishment of the rabbits unilateral eyelid defect model, the eyelid reconstruction in situ were performed with either acellular xenogeneic dermal matrix or allogeneic sclera at random. The rabbits were clinically examined for inflammation and impant exposure and sacrificed 1, 2, 4, 6, 8 and 12 weeks after implantation. The eyelid with implant ( Xeno-ADM or allogeneic sclera ) were dislodged and the specimens were assessed histopathologically and ultrastructually with light microscopies respectively for evaluation of change of juncture between implant and autoallergic tarsal plates including inflammation, vascularization and confluence. The 4, 8 and 12 weeks specimens were assessed with transmission electron microscope micro structural changes of the above organizations.Results1. When the eyelid reconstruction in situ were performed with either acellular xenogeneic dermal matrix or allogeneic sclera, there were similar reaction and change between them. But Xeno-ADM as repairing materials, it invokes more little immunological and inflammatory reaction than that of the allogeneic sclera. Moreover, no implants shedding, exposure or infection happened postoperatively; good blood supply and no cellular necrosis. The conjunctiva grew well on the surface of the implant ( Xeno-ADM or allogeneic sclera).2. With the light microscopy, 2 weeks after implantation, the borderline between Xeno-ADM implant and autoallergic tarsal becomes fuzzy; while at the conjuction area, some complete capillary structure and a few fibroblasts were seen growing into the implant. 8 weeks after implantation, the borderline transitions gradually. Relatively larger new blood vessels were seen obviously growing at the center of the Xeno-ADM implant with complete endothelial cell in the blood vessels. 12 weeks after implantation, the arrange of the collagen network of the acellular dermal matrix lost the directivity, and both the vertically and the horizontally arranged new collagen could been seen; The new small vessels and proliferative neurofibra tubulus could been found among the Xeno-ADM implant. However, a few fibroblasts and small new vessels were only observed 4 weeks after implantation in allogeneic sclera group. At 1, 2, 4, 6 and 8 weeks after implantation, the inflammatory cells (neutral granular cells, uni-nuclear cells), the lymphocytes and the plasmocytes are less than those of the allogeneic sclera implants, and the blood vessel grows faster, the new collagen grows into implant faster. There is no statistical difference between two groups when the experiment ended.3. With the electron microscopy, histopathological change and cellular change in form of the Xeno-ADM are similar to those of the allogeneic sclera.Conclusion1. As the substitute of tarsal cartilages, when the eyelid reconstruction in situ were performed with either acellular xenogeneic dermal matrix or allogeneic sclera, there were similar histopathological and immunological change between them. This process could be divided into three stages (1) inflammation reaction stage (1-2 weeks after the implants ); (2) the cell infiltration and the textile fiber growth stage ( 2 weeks - 2 months after the implants ); (3) the scar organization production stage (2-3 months after the implants ).2. Xeno-ADM as repairing materials, as the support for eyelid's soft tissue's growth in the eyelid reconstruction in situ, it invokes more little immunological and inflammatory reaction than that of the allogeneic sclera. Furthermore, inflammatory reaction after operation regresses quickly; no implants shedding, exposure or infection happened postoperatively; good blood supply and no cellular necrosis. The conjunctiva grew well on the surface of the acellular dermal matrix.3. As the substitute of tarsus in supporting the eyelid, Xeno-ADM possesses flexibility and tenacity and resembles the construction, function and color of autoallergic tarsal. Graft rejective reaction doesn't invoke obviously. Xeno-ADM and tarsus produced the new collagen to unite them with each other.In brief, as the substitute of tarsal cartilages, the Xeno-ADM retained the basic ingredients of the collagen fiber and the small blood vessel, which allows the host cells, the new blood vessel and the new collagen to grow into the eyelid to unite the transplant. Therefore, it can act as a superordinary biological scaffold to utilize in blepharop lasty .