Histology Outcome Of Acellular Dermal Matrix After Being Transplanted Under The Mucoperiosteum Of The Hard Palate

Objective:To demonstrate if the denuded bone of the hard palate and the formation of scar tissues on it can lead to disturbance in maxillary's growth, and discuss the reason of it. And observe the histology outcome of acellular dermal matrix(ADM) after being transplanted under the mucoperiosteum of the hard palateMethods:Part1:Thirty three-week-old male Wister rats were randomly divided into 3 groups. 10 rats in control group (no treatment on the hard palate); 10 rats in 1/3 bone denudation group (remove about 1/3 of the hard palate's mucoperiosteum ); and 10 in 3/4 bone denudation group (remove about 3/4 of the hard palate's mucoperiosteum). All rats will be killed to compare the length and width of their palate after 12 weeks of the surgery.Part2:Four 1.5cm×2.5cm allograft, 0.8mm thick, were obtained from 4 Wistar rats'back skin with a dermatome, then divided into 8 pieces, all about 1cm2 square. Donor skin was treated with 1M NaCl 4℃for about 48 hours to rip away the cuticular layers, the remained dermis were immerged into 0.5%Triton X-100, shaking in 28℃for about 48 hours to wash away cells in it and obtain acellular dermal matrix(ADM). ADM was stored in asepsis normal saline in 4℃after antibiotic treatment. Take sample of the ADM to do histology observation, and transplant 6 pieces of ADM under the mucoperiosteum of 6 adult female Wister rats'hard palate, to estimate the ADM's antigenicity and the regenerate of collagen tissues in it.Part3:45 female 12-week-old Wistar rats were selected as experimental group, two lateral incisions were made along the gingival marginal of hard palate, and the mucoperiosteum was peeled off from the bone. Then transplant the ADM to the space between mucoperiosteum and denuded bone of the hard palate, make the basement membrane surface towards mucoperiosteum. All the animals will be sacrificed at 2nd,4th,6th,10th,14th,21st,28th,42nd,56th day after the operation, 5 in every time, to see the morphologic changes of the hard palate, and take samples to do histology observation, and also do immunohistochemical staining of collagen type I to see it's regeneration. As a contrastive observation, another 30 female 12-week-old Wistar rats were used, do the same operation but transplant variant skin to the space between mucoperiosteum and denuded bone of the hard palate.Results:1.The width of palate in 3/4 bone denudation group and 1/3 bone denudation group were significantly narrower than that of the control group, the width of the palate in 3/4 bone denudation group also significantly narrower than that of the 1/3 bone denudation group. There is no demonstrated statistical difference between the length of palate between the three groups. Necrotic bone appeared in the mid palate of the rats in 3/4 bone denudation group, and all rats in that group had an osteal cranny, the wounds were repaired by scar tissues.2.There's no cell constituents remained in the acellular dermal matrix (ADM) made by NaCl and TritonX-100 method, collagen frame remained relative integrity, and the immunocompetence of this material is very low, also the biocompatibility of the ADM is very well.3.After being transplanted between the mucoperiosteum and denuded bone of the hard palate, inflammatory reaction in ADM was serious at the first week, but will clear off step by step after 10 days. From the 2nd day after operation, fibroblast begin to invade into the ADM, collagen fibers and elastic fibers regenerate gradually, loosen tissues were absorbed. At the 56th day after operation, regeneration accomplished, the ADM survived under the mucoperiosteum. The joint of bone and ADM was compactness, and no formation of scar tissues. The collagen fibers of ADM are grossness and arranging in horizontal direction, no necrotic bone appeared on the hard palate. Inflammatory reaction was serious after transplanting variant skin under the mucoperiosteum of the hard palate. At the 14th day after transplanting, the inflammatory became more serious, the graft didn't grow together with the mucoperiosteum, and after 3 weeks there's no grafts left, the inflammatory clear off gradually.Conclusions:1. The bone denudation of the hard palate can lead to disturbance in maxillary's growth, the formation and contracture of scar tissues, and the inflammation and putrescence of the denudate bone are two important factors.2. NaCl-Triton method can remove the cellular components from the dermal matrix completely, as the collagen frame remained relative integrity. The immunocompetence of this material is in very low level. ADM made by this technique can be used in alligraft.3. After being transplanted to the space between mucoperiosteum and denuded bone of the hard palate, ADM do not cause immunological rejection, and survive well. The regeneration of collagen fibers are suit for the hard palate's function. Also the ADM can protect the denudate bone and restrain the formation of scar tissues on it. It can play an important role in the operation of cleft palate repairing.