| BackgroundSoft tissue expansion technology has been a well-established technique for reconstruction of large defects. However, the long expansion cycle is one of the main disadvantages of this technique. How to improve expansion efficiency without damaging the structure of the skin has been a big problem, and researchers have tried a variety of methods, but the effect are very limited. Adipose-derived stem cells are a kind of highly self-renewal and pluripotent stem cells. Currently, it has become a research hotspot of repair and reconstruction of tissue and organ. In the field of plastic surgery, many studies have confirmed ADSCs have a variety of positive roles in skin and soft tissue reconstruction. However, the impact of ADSCs on expanded flap is still poorly understood.ObjectivesFirst, the clinical application of tissue expansion technique was reviewed. At the same time of affirming its incomparable advantages, its disadvantage of low expansion efficiency was pointed out. In animal experiments, ADSCs were injected into the skin before expansion. The expansion efficiency and skin’s histological structures were examined. In addition, after ADSCs were labeled with BrdU, their migration and distribution was detected. The ultimate goal of this research is to provide a possible way to improve the tissue expansion efficiency for clinical use.MethodsThis study is divided two parts. The first is the experience summarization of clinical application of soft tissue expansion technology, and the second is animal experiment.The first partThe application of expanded forehead flaps for cervicofacial rehabilitation from 2000 to 2013 was systematically reviewed. The expanded forehead flaps was classified based on the blood supply. According to different faciocervical aesthetic units, the types of expanded forehead flaps were collected, including the expansion information, surgical procedures, and follow-up data. At last, a strategy for selecting expanded forehead flaps in terms of deformities or lesions location and size is developed.The second part1. Experiment grouping:12 wuzhishan pigs were divided 3 groups. Group A:3 pigs were used to compare the influence of expansion versus expansion+acupuncture on the skin; Group B:3 pigs were the effect of expansion+acupuncture versus expansion+ acupuncture+PBS on skin; Group C:6 pigs were used to compare the influence of expansion+acupuncture+PBS versus expansion+acupuncture+ADSCs on the skin. Intra-group comparison was adopted. Two 200ml round expanders were embedded in each side of the pig’s dorsum. The skin measured 1×1cm2 in the central region of every flap was tattooed as the research target.2. Culture, examination and labeling of ADSCs:SVF was obtained by enzymatic digestion method and then cultured and expanded in vitro in order to gaining purified ADSCs. When expanded to the third passage (P3), ADSCs were labelled by BrdU. The adipogenic and osteogenic differention ability of ADSCs were detected.3. Expansion of flap:The BrdU-labelled ADSCs were injected into the tattooed area of the flap in the right side of each porcine in group C. All the flaps were expanded once a week, and 30ml sterile saline was injected into the expander every time. The expansion period was 12 weeks.4. Examination of expansion efficiency:After termination of expansion, the size of expanded tattooed skin was measured using 3D laser scanner. The increased area of expanded skin in each group was compared.5. Skin histological examination:epidermal thickness and dermal thickness were measured using hematoxylin-eosin staining; the number of proliferating cells in epidermal layer was counted using immumohistochemical staining of PCNA; the content of collagen and elastic fiber were measured using sirius red staining and Verhoeff’s iron hematocylin staining, respectively; the vascular density was measured using immumohistochemical staining of α-SMA; the ultrastructure of expanded skin was observed under scanning electron microscope and transmission electron microscope. The migration, proliferation, and possible differentiation of ADSCs were traced by BrdU immunofluorescence.Results:The first partFour types of expanded forehead flaps were used for the faciocervical reconstruction of 143 patients. Type Ⅰ was a pre-expanded local flap used for repairing defects of the partial forehead unit, subunits of the periorbital unit, or partial involvement of the two adjacent units. Type Ⅱ was an expanded paramedian forehead flap used for resurfacing the nose, orbital unit, upper cheek unit, and partial involvement of these adjacent units. Type Ⅲ was a bilateral pedicled expanded forehead flap for the reconstruction of the lower face and anterior neck. Type Ⅳ was a unilateral pedicled expanded forehead flap, based on the superficial temporal vessels, used to reconstruct the ipsilateral part of the middle face. The long expansion period is still a main disadvantage of tissue expansion.The second part1. The ADSCs of the 6 pigs in group C have no significant difference in either adipogenic differentiation potential or osteogenic differentiation ability. The BrdU labelling procedure has no significant effect on the cell viability and differentiation of ADSCs.2. Both group A and C had 1 pig undergoing one expander ruptured. In group B, expander exposure occurred in 1 pig due to flap necrosis, and the same complication occurred in 2 pigs in group C. After excluding the expanded flaps which had complications, the flaps that can be used for experimental study in group A, B and C were 5 pairs,5 pairs and 9 pairs, respectively.3. In group A, the expansion volume for the expanders in the left and right back of pigs were 352.20±2.59ml, and 355.20±3.03ml, respectively. In group B, the ultimate volume of the expanders in the left and right dorsum were 353.00±4.53ml, and 353.20±4.15ml, respectively. In group C, the final volume of the expanders in the left and right dorsum were,354.22±2.91ml, and 355.44±1.74ml, respectively. The intra-group comparison showed all of them had no significant difference.4. After expansion, in group A, the size of expanded flaps in the pig’s left back increased 0.644±0.068 cm2, and the right side increased 0.662±0.067 cm2; In group B, the increased area of expanded flaps in the pig’s left and right back were 0.642±0.079 cm2, and 0.650±0.070 cm2, respectively. In group C, the pig’s left expanded flaps increase 0.632±0.083cm2, and the right increased 0.908±0.131cm2. Both group A and B had no significant difference between the increased flap size in the pig’s left and right dorsum, while the size of the right expanded flap had a significant increase compared with the left flap (p<0.05).5. In group A and B, there is no significant difference in epidermal thickness and dermal thickness between the left and right flaps, while in group C, both the epidermal thickness and dermal thickness of the right flaps had a slight increased (not reach statistical significance) compared to the left flaps.6. The PCNA positive cells in the epidermal layer of the right expanded skin had no significant difference from the left both in group A and B. However, within group C, the right expanded skin showed significantly higher PCNA positive cells number than the left flap (p<0.05).7. Picro-sirius red staining showed that the collagen content of right expanded skin in group A, B and C did not have a significant increase when compared to their own left control flaps. However, in group C the collagen content of right skin did show a slight increase relative to its left control flaps.8. As elastic fiber content, the same trend as collagen content was found in all groups. In addition, the elastic fiber distributed paralleling with the skin in flaps with injection of ADSCs, but it had a disorganized and fragmental structure in other flaps.9. For the α-SMA+vessels, there was no significant difference between the right skin and the left control skin in both group A and B. In group C, the number of arterioles in the right expanded skin had a significant increase compared with the left flap (p<0.05).10. Ultrastructural examination showed a modified tridimensional architecture of the derm, which showed a reduced diameter and a high dense of collagen fibers in the skin with ADSCs injection when compared with other control flaps. Another relevant finding was the filaments in the collagen fibers distributed more compactly in the ADSCs injecting skins than other flaps.11. The BrdU-labeled ADSCs were present until week 4 but were then undetectable. Most of them distributed in the dermal layer and a few located in the epidermal layer.ConclusionsThe first partThe four types of expanded forehead flap can be used for the reconstruction of different faciocervical units. Based on the location and size of the defect or lesion, the selection of these flaps can be planned preoperatively. The disadvantage of long expansion period for tissue expansion technology still needs further studies to solve.The second partIt can improve expansion efficiency for tissue expansion technique with the help of ADSCs injection. ADSCs can improve cell proliferation, angiogenesis and extracellular matrix formation through direct action (pluripotent differentiation) and indirect action (paracrine). The number of proliferating cells in the epidermis increased and also did the fibroblasts in dermal layer. The function of fibroblasts also enhanced. All these resulted in thickening of the epidermis and dermal thickness and increase of dermal collagen and elastic fiber content. In addition, ADSCs may also alter the collagen fibers compliance under tension so that it is conducive to the skin expansion. |
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