Experimental Study Of Acellular Xenograft Dermal Matrix As The Sclera Substitute

PURPOSEThe ophthalmol plastic reconstruction surgery normally needs various kinds of repairing materials; the reserved allogeneic sclera is one of the most popularly used materials. However, the allogeneic sclera source is limited, the application cost is relatively high, and it is hard to obtain the sclera from the hospitals without eye banking facilities. In addition, the allogeneic sclera transplant has the risk of infection. Therefore it is necessary to seek a more ideal material which is more easily obtained, stronger and more economicalfor 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. Thisexperiment focused on using Xeno-ADM to replace the sclera as the wrapping material for hydroxy apatite (HA) ocular implants after the rabbit eye enucleation and to repair the rabbit sclera defect. With the evidence from the histology and cytology experiment, Xeno-ADM proved to be a substitute of sclera for clinical use, which provides the verification to broaden the application of the Xeno-ADM in ophthalmology.METHODS1. Establishment of the rabbit unilateral eye enucleation model, the sockets were implanted with HA spherical implants wrapped 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 sockets with Xeno-ADM or allogeneic sclera were exenterated and the specimens were assessed histopathologically and ultrastructually with light microscopies respectively for evaluation of changes including inflammation and vascularization. The 4, 8 and the 12 w specimens were assessed with transmission electron microscopy micro structural changes of the above organizations.2. Establishment of the rabbit model with sclera defect, the defect area was replaced with Xeno-ADM. The rabbits were clinically examined for inflammation and eyeball healing.sacriflced 2,4 weeks after implantation. The sockets with Xeno-ADM were exenterated and the specimens were assessed histopathologically and ultrastructually with light microscopies respectively for evaluation of changes including inflammation and vascularization.RESULTS1. The sockets were implanted with HA spherical implants wrapped with either acellular xenogenic dermal matrix or allogeneic sclera. It wasobserved that the Xeno-ADM had less inflammation and quicker recovery compared to the allogeneic solera, there were no HA exposure, and blood run well without any necrosis .2. With the ligth microscopy, 2 weeks after implantation, some completecapillary structures were observed in the. Xeno-ADM implants , and the blood cells could be found in the vessels with a few fibroblasts; while at the conjuction area, a few new blood vessels and collagen were seen growing into implant sockets. 8 weeks after implantation, relatively larger new blood vessels were seen obviously growing at the center of the implant sockets 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 horizontally arranged new collagen could be seen; The gaps in the sockets were completely filled up with the tightly arranged new collagen, in which a few fibroblasts were seen. The new blood cells and the collagen grown into the sockets were only observed 4 weeks after the implantation. At 1, 2, 4, 6, 8 and the 12w after the implantation, the inflammatory cells (neutral granular cells, uni-nuclear cells), the lymphocytes and the macrophages are less than those of the allogeneic sclera implants, and the blood vessel grows faster, the new collagen grows into the sockets faster.3. With the electron microscopy, the lymphocyte , the macrophages and the fibroblasts cells of the Xeno-ADM were found to be more mature and active than those of the allogeneic sclera.4. In the sclera defect repair group, there was no obvious inflammation andeyeball deformation observed. 2 weeks after implantation, the partial inflammatory cells invasion were seen with the light microscopy, and there was an obvious border line between the Xeno-ADM and the sclera. 4 weeks after implantation, the inflammatory cells were reduced noticeably, the Xeno-ADM and the sclera completely merged with each other.CONCLUSION1. After the sockets were implanted with HA spherical implants wrapped with either acellular xenogenic 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...