The Effects On Microvessel Of Skin Flap In Different Skin Expansion Ways

Objective: The expressions of VEGF and CD31 were studied in different ways of skin expansion and to discuss the best suitable clinical ways and to provide the theory basis.Methods: 1 Experimental animal: Sixty-two male New Zealand big white rabbits, 6 months old, and weighted from 2 to 3Kg, were provided by Laboratory Animal Center of Hebei Medical University.2 Groups: Sixty-two rabbits were randomly divided into 5 groups: Group A (repeatedly rapid expansion), Group B (rapid expansion), Group C (conventional expansion), Group D (embedding but not expansion) and Group E (normal control). Group A and B with 20 rabbits each were divided into five subgroups by the different maintenance time. Group C with 16 rabbits was divided into four subgroups by the different maintenance time. Group D with 5 rabbits was divided into five subgroups by the different maintenance time. Group E with 1 rabbit was normal control group.3 Animal model preparation: The experimental animals were weighed and then performed intravenous anesthesia with 2.5g/L pentobarbitol sodium (25mg/Kg). Skin incisions were done between two sulcus auriculae posterior. Forehead skin was bluntly separated from the skull periosteum by blood vessel forceps. The expander of 50ml was embededed. Since the third days after operations, expansion was begun. Group A: Twenty millilitres sterile saline was injected into expander and maintained for 30 min and then pumdbacked compeletly.There was a three hours'interval to the next injection. The expansion procedure was repeated for three times and in the fatal expansion saline was pumdbacked 15 ml. The injection was completed for 10 days. Group B: Five millilitres sterile saline was injected into expander at once a day. The injection was completed for 10 days. Group C: Five millilitres sterile saline was injected into expander at every three days.The injection was completed for 28 days. E: normal. 4 Specimen collections and processing: In different maintainace time, the tissues of 1×1cm were incised from the center of the expanded flap under general anaesthesia. The specimens were fixed in 10% formaldehyde fluid, dehydrated, transparented, soaked the wax, embedded, and then made 4μm sections. 5 Observation index and methods: 5.1 macroscopic observation of general specimen 5.2 the observation of light microscope 5.3 Immunohistochemical methods and image analysis system were used to examine the expressions of VEGF and CD31 in expanded skin flaps. 6 Statistical Methods: All data were presented as mean±SD and processed by SPSS 11.5 statistical package. P<0.05 was considered as significant difference.Results:1 General observation: All the experimental animals had no complications such as infections, reveal of expanders and necrosis in skin flaps. 2 Histological observations: At different maintenance time, blood vessels were obviously hyperplasia and mainly centered in papillary layer, network layer and surroundings of hair follicle. 3 Microvascular densities (MVD): MVDs in group A, B and C at maintaining-for-1 week were relatively high. With the duration of the maintenance time, MVD showed a downward trend and reached the lowest level at maintaining-for-4 week and then increased again. At maintaining-for-1,2,3,4 week, MVD of group A was significantly higher than that of group B and C (P<0.05) but group B and group C had no significant difference (P>0.05). At maintaining-for-6 week, MVD of group A was higher than that of group B (P<0.05). MVD of group A and B at maintaining-for-6 week were significantly higher than that of group C maintaining-for-4 week (P < 0.05). 4 VEGF expressions: The expressions of VEGF in group A, B and C at maintaining-for-1 week were relatively high. With the duration of the maintenance time, VEGF expression showed a downward trend and reached the lowest level at maintaining-for-4 week and then increased again. At maintaining-for-1 week, VEGF expression of group A was significantly higher than that of group B and C (P<0.05) but group and group C had no significant difference (P>0.05). At maintaining-for-2,3,4 week, the comparison of VEGF expression of group A with group B and C had no significant difference(P > 0.05). At maintaining-for-6 week, VEGF expression of group A has no significant different compared with that of group B (P>0.05). VEGF expression of group A and B at maintaining-for-6 week were significantly higher than that of group C at maintaining-for-4 week (P<0.05). 5 The relationship between VEGF and MVD: The distribution of VEGF-positive cells had a high degree coincidence with vascular density. VEGF-positive expression was significantly correlated with MVD (r=0.889, P<0.001).Conclusions: 1 The repeatedly rapid expansion ways can effectively improved vascular density in the expansion skin flaps and superior to rapid expansion and conventional expansion ways. 2 The repeatedly rapid expansion ways can effectively improved the synthesis and secretion of VEGF in the expansion flaps, and promoted the generation of blood vessel. 3 Vascular degree of expansion had close correlation with the maintenance period and the stimulus intensity. Microvasculature stability was at maintaining-for-4 week. 4 The repeatedly rapid expansion ways can not only promote vascularization degree of expansion flap but also shorten the period of treatment.