| BackgroundWith the developments of plastic surgical technique and biomaterial, the skill of soft tissue filling has improved rapidly in recent years. Soft tissue filling technique can be used to solve the problems of innate or acquired maxillofacial soft tissue sag and asymmetry. It is of great clinical importance to find an ideal soft tissue filling. Application of facial soft tissue filling materials has become a hot topic in the research of scholars around the world. There are many types of soft tissue filling materials. Soft tissue filling materials, being in the field of cosmetic surgery, also have a new development. Because of minimally invasive and operational simplicity, injected packing material becomes popular among the various kinds of filling materials, directing the future development for the soft tissue materials.As a heterogeneous or allogeneic matrix material after being decellularized, acellular dermal matrix is the rise of a new type of tissue substitue, retaining the three-dimensional structure of normal collagen scaffold in dermal extracellular matrix and providing a good support for tissue regeneration. Acellular dermal matrix has been used in the field of burn plastic surgery and oral surgery from the mid 1990 s, obtaining the good clinical effects. There are scholars trying to use acellular dermal matrix as a soft tissue filling material in cosmetic surgery such as repairing the maxillofacial soft tissue defect, labial ministry beauty, eyes filling and nasolabial groove filling. Therefore, this study was to explore the effect and mechanism in the animal after being implanted the sheet of acellular dermal matrix or the particles of acellular dermal matrix. It will make a basement for the acllelular dermal matrix to be micronized further and produce an injection type of acllelular dermal matrix, inspecting of providing a more ideal soft tissue filling for clinical use.ObjectiveUsing the sheet of acellular dermal matrix, the particles of acellular dermal matrix and hyaluronic acid gel as soft tissue fillings to build soft tissue augmentation model in animals, the study was to evaluate the filling effect by measuring the volumes and the heights of tissue augmentation in the graft sites; to explore the mechanism by tissue morphological observation in the graft sites of rabbit ears and propotion of type I to Ⅲ collagen; to discuss the feasibility whether the acllelular dermal matrix will be micronized further and produce an injection type of acllelular dermal matrix.Methods1. The ears of rabbits were injected with gel fillings in a volume of 0.05 ml, 0.10 ml and 0.15 ml, and each group of 6 samples. The volumes of the tissue augmentation in the graft sites were detected by a 3D optical scanner. All the samples were embedded in OCT and sectioned in-20℃. The heights of the tissue augmentation in the sagittal sections were measured.2.1.0 cm×1.0 cm×1mm acellular dermal matrix sheet (Heal-All dental restorations membrane) was bladed into 1 mm×1 mm×1 mm particles. A size of 1.0 cm×1.0 cm subcutaneous pocket between dermal and cartilage stealth was made after a 1.0-centimeter incision made on the dorsal surface on the ear of the rabbit. The hydrated acellular dermal matrix sheets and the hydrated acellular dermal matrix particles were implanted in the pockets respectively, and then the specimens were harvested in 1 w、2 w、1 m、3m、6m、9 m. The ears of rabbits were injected with hyaluronic acid gel in a volume of 0.10 ml and were harvested in 1 w、2 w、1m、3 m、6 m. Three treatment groups in every graft time were of 6 samples.6 blank areas in the ears of 6 rabbits were chosen as control group. The volumes of the tissue augmentation in the graft sites were detected by a 3D optical scanner. There were 4 samples in each group of every graft time to be scanned and detected by Micro-CT. The volume of the graft sites with different soft tissue filling materials in different time were compared by SPSS20.0 statistical analysis software.3. All the specimens were fixed in 4% paraformaldehyde, decalcified in EDTA, sequentially dehydrated, and then embedded in paraffin. Pathological specimens were sectioned and applied with HE staining and Masson staining, Sirius red staining. The tissue morphology was observed and the heights were measured in the graft sites using Image-pro plus 6.0 software. Sirius red staining sections were observed under polarized light and the propotion of type I to Ⅲ collagen were measured by Image-pro plus 6.0 software (red and green in the same picture of the ratio of area).Results1. The volumes of the tissue augmentation with injection of 0.05 ml,0.10 ml and 0.15 ml were (57.277±9.772) mm3, (106.785±10.568) mm3 and (129.686±28.896) mm3. The volumes of the tissue augmentation in the three groups compared with the injection volumes, differences were not significant (P =0.128>0.05;P=0.177>0.05; P=0.146>0.05). The heights of the tissue augmentation were (2.300±0.182)mm,(2.797±0.279)mm,(2.890±0.411)mm. The heights of the tissue augmentation with injection of 0.05 ml were lower than 0.10 ml group and 0.15 ml group (P=0.001<0.05;P=0.000<0.05).When the injection volume increased from0.05 ml to 0.10 ml, the heights of the tissue augmentation increased. There was no statistically significant difference between 0.10 ml group and 0.15 ml group in the heights of the tissue augmentation (P=0.441>0.05).It meant that when the injection volume increased from0.10 ml to 0.15 ml, the height of the tissue augmentation made no significant change.2. Neither infection nor necrosis was found in the graft sites. All the experiment animals were in good conditions after the operation. Effects of the soft tissue augmentation of the acellular dermal matrix particles group and acellular dermal matrix sheet group in 9 m were not obvious, which could not be detected by the 3D optical scanner or by the Micro-CT. The results measured by the 3D optical scanner and the Micro-CT were consistent, and three kinds of materials showed effect on soft tissue augmentation.In overall, the acellular dermal matrix particles group, acellular dermal matrix sheet group and hyaluronic acid gel group decreased as time passed, which decreased fast in the first month and then slowed down in 3 m～6 m. The mean value of acellular dermal matrix particles group in every graft time was close to the acellular dermal matrix sheet group. The mean value of hyaluronic acid gel group in every graft time was lower than the acellular dermal matrix particles group.Statistical analysis:According to the results measured by the 3D optical scanner and the Micro-CT, only the main effect of graft time and soft tissue filling should be analyzed.The volumes in 6 m of the three groups, were compared with 1w、2w,1m and 3 m separately. Measured by the 3D optical scanner and Micro-CT, in the hyaluronic acid gel group (P=0.005<0.05;P=0.042<0.05), there was statistical difference between 6 m and 3 m; both in the acellular dermal matrix particles group (P=0.415>0.05, P=0.227>0.05)and in the acellular dermal matrix sheet group (P= 0.186>0.05, P=0.170>0.05), there were no statistical differences between 6 m and 3 m. In 2 w, both volumes in the acellular dermal matrix particles group (P=0.002<0.05; P=0.005<0.05) and in the acellular dermal matrix particles group (P=0.001<0.05; P=0.012<0.05) were larger than in the hyaluronic acid gel group.3. HE staining results:In 1 w and 2 w, acellular dermal matrix groups:lots of lymphocytes and red blood cells were gathering in the graft sites in all the treatment groups; and fibroblasts invaded in graft sites. The materials were absorbed in acellular dermal matrix particles group and acellular dermal matrix sheet group, while the new fiber grew in from different directions, replacing the original fiber in the materials and reconstructing as the host tissue at last. In the hyaluronic acid gel group, a temporary scaffold formed by the material and the new born fibers was for the cell to grow and then the scaffold degraded gradually.Masson staining results:New fibers were grown into graft sites in the acellular dermal matrix particles group, acellular dermal matrix sheet group and hyaluronic acid gel group, and the amount of fiber increased as time passed. The fiber surrounded and replaced the implant materials in the both of acellular dermal matrix groups, which had a disordered arrangement in the early period and then arranged compact and tidy In the hyaluronic acid gel group, the fiber formed a scaffold that supported the cells to grow, and as the time passed the fibrous scaffold broke down.Sirius red staining results:the type I collagen was red or yellow and type Ⅲ collagen was green observed under polarized light. On the slides, noncollagenous material was dark. The area with red or yellow in every view of the treatment group section changed over time. The acellular dermal matrix particles group:in the early period, the type Ⅲ collagen increased gradually, which distributed between particles and particles then invaded in the center of the particles. As the time pass, the type III collagen decreased and the type I collage increased. In 6 m and 9 m, the type I collage became the mainly fiber in the graft sites and the collagen fiber arranged similar to the surrounding tissue. The acellular dermal matrix sheet group: in the early period, the type Ⅲ collagen surrounded the sheet, and then invaded from the base surface to the dermal surface. As the time pass, the type Ⅲ collagen was replaced by the type I collagen.Results of the Ⅰ/Ⅲ type collagen propotion:in overall, the Ⅰ/Ⅲ type collagen propotion of the graft site decreased in the first 2 w and then inclined, which was closed to the propotion of the normal tissue in 6 m and 9 m. The regular change propotion of the collagen was accord to the process of healing after the body trauma. In 6 m, compared with the blank group, the acellular dermal matrix particles group(P=0.455>0.05), the acellular dermal matrix sheet group(P=0.688>0.05), the hyaluronic acid gel group(P=0.339>0.05), there were no statistically significant differences.In 9 m, compared with the blank group, both the acellular dermal matrix particles group(P=0.330>0.05) and the acellular dermal matrix sheet group (P=0.418>0.05), there were no statistically significant differences.Results of the height in the graft sites:the acellular dermal matrix particles group, the acellular dermal matrix sheet group and the hyaluronic acid gel group decreased as time passed, which decreased fast in the first month and then slowed down. In 6 m、9 m, the heights in the graft sites were closed to the blank group. Different from the volumes, the heights in the hyaluronic acid gel group were highest among the 3 groups after 1 m. In 6 m, there was no statistical difference between the acellular dermal matrix sheet group and the blank group (P=0.056>0.05).In 9 m, compared with the blank group, both the acellular dermal matrix particles group(P=0.790>0.05) and the acellular dermal matrix sheet group(P=0.790>0.05),there were no statistical differences.Conclusions:1.0.05-0.10 ml is an optimal injection volume range to evaluate the tissue augmentation in the rabbit ear after the injection of gel fillings.2. Acellular dermal matrix particles, acellular dermal matrix sheet and hyaluronic acid gel have a favorable effect in soft tissue augmentation, evaluated by the volumes and the heights in the graft sites. When the acellular dermal matrix sheet granulated in to 1 mm×1mm×1mm, the acellular dermal matrix particles gained almost the same effect as the sheet in the tissue augmentation, and showed better stability than the hyaluronic acid gel. It is feasible that the acllelular dermal matrix can be micronized further and produces an injection type of acllelular dermal matrix.3. After the implantation of acellular dermal matrix particles and acellular dermal matrix sheet in the ears of the rabbits, according to the change of histology, the acellular dermal matrix were absorbed in the graft sites while the new fibers grew in and the collagen fibers became mature gradually. At last, the tissue in the graft sites reconstructed as the host tissue. |
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