Objective: To investigate the histocompatibility of acellular xenogenic pig dermal matrix (Xeno-ADM) after transplanted into the rabbit eyelids.
Methods: Thirty-eight New Zealand rabbits were divided into two groups randomly. After excising a 5 mm x 4 mm tarso-conjunctiva flap from one lower eyelid of each rabbit, Xeno-ADM and allogenic sclera were implanted in these two groups separately. Samples of implanted material were collected for histological examination in 1, 2, 4, 6, 8, 12 and 16 weeks after the operation. RIA method was employed to determine the contents of IL-2 and IL-6 in the homogenate fluid from local tissues and in peripheral blood.
Results: Compared to the control group, after the operation, the conjunctival congestion, effusion, inflammatory reaction and red swelling of the eyelid subsided faster in the treated group. No rejection or necrosis occurred in transplanted rabbits. At 16 weeks after operation, SNK-q test showed there was no obvious difference in the average breadth and height of the eyelids (P > 0.05) between these two groups and normal rabbits. Histological examination of sections of eyelid tissues stained by HE staining and observed under light microscope showed that at 1, 2, 4, 6, 8, 12 and 16 weeks postoperatively, eyelids implanted with Xeno-ADM had less inflammatory reaction, fewer lymphocytes infiltrating and higher vascularization with faster ingrowths of new collagen fibers, as compared with the sclera-implanted group. This also indicated that Xeno-ADM had a good compatibility. Statistical analysis of immunogenic indexes indicated that the level of IL-2 and IL-6 in the homogenate fluid at 6-8 weeks postoperatively was greater than those in 1, 2, 4 weeks after implantation. The level of IL-2 and IL-6 rose significantly after the operation and reached a peak value at the 6 th week (experimental group, IL-2, 0.292 81 ng/ml) and 8 th week (experimental group, IL-6, 118.258 pg/ml; control group, IL-2, 0.277 99 ng/ml and IL-6, 255.871 pg/ml). The level of IL-2 and IL-6 dropped significantly at the 12th week and raised again at the 16th week, therefore, the concentration achieved another peak value in the control group (IL-2, 1.363 41 ng/ml; IL-6, 622.863 pg/ml), which was much higher than those in the first peak. The level of IL-2 and IL-6 in peripheral blood 1 week after the transplantation was higher than the preoperative level. These two indexes increased gradually with marked fluctuation, particularly in 4 - 8 weeks after implantation, both of them reached the peak values at that period, which was similar to the inflammation reaction changes in the implanted groups. With replicated testing and analysis of variance (ANOVA), neither the type of treatment nor the time factor had any effect on the levels of IL-2 and IL-6 in the serum, and there was no significant difference between experimental group and control group (P > 0.05).
Conclusions: Xeno-ADM shows good histocompatibility to New Zealand rabbits, which can induce neovascular and collagen fibers grow into implanted tissues. Therefore, this can be used to support the eyelids as a substitution for the tarsus. High levels of IL-2 and IL-6 can be detected in local tissues and in the serum after Xeno-ADM transplantation, but no statistical differences present between the dynamic changes of the level of both ILs in Xeno-ADM group and allogenic sclera group. Xeno-ADM could be an ideal substitute for allogenic sclera in the reconstruction of eye lids and could be used broadly in ophthalmology. However, as a hetero-transplantation material used clinically, further ethical and immunological studies are required.