To study the effect of granulation tissue injection of micropar skin pulp on the healing of traumatic chronic wound in rats.

Sixty SD male rats were selected to make wounds of 3.0 cm×3.0 cm in the back and sewed on the inner edge of the wound with wire coils. The rats were divided into 3 groups according to the random number table method, which were general wound group, chronic wound group and micropar skin pulp group. There were 20 rats in each group. The general wound group was treated with anti-infective therapy and the routine dressing change after the wound was caused by the back. The chronic wound group was treated with anti-infection treatment and routine dressing change after the formation of the back wound. Chronic wound formation was completed by intramuscular injection of hydrocortisone for 7 days. After the formation of the wound on the back of the micropar skin pulp group, anti-infection treatment and the routine dressing change were given, intramuscular injection of hydrocortisone was performed for 7 days in a row to interfere with the formation of the chronic wound, and the microne was prepared from the skin on the lateral side of the right thigh of the rats and injected under granulation tissue. The observation of wound surface was started next day after the completion of modeling, which was set as the observation day. The wound healing of each group was observed on the 7th, 14th, 21st, 28th day of observation and the wound healing rate was calculated. Granulation tissues on 14th day of observation were retained and observed for hematoxylin-eosin staining and CD31 immunohistochemical staining. The distribution of new capillaries was observed under hematoxylin -eosin staining and the expression of CD31, microvessel density of the wound were observed by CD31 immunohistochemical staining. Data were analyzed with one-way analysis of variance and LSD-t test.

On the 14th day of observation, the wound of the general wound group was significantly reduced, the skin climbing of the chronic wound group was not obvious, and most of the wound was healed in the micropar skin pulp group. On the 28th day of observation, there was remaining wound in the general wound group, the wound healing in the chronic wound group were not obvious, most of wounds in the micropar skin pulp group healed. On the 14th, 21st, 28th day of observation, the healing rates of the general wound group were (51.09±0.94)%, (75.43±0.92)%, (86.51±0.57)%, and healing rates of the chronic wound group were (20.30±0.95)%, (35.59±1.18)%, (45.82±1.35)%, and the healing rates of the micropar skin pulp group were (39.00±0.86)%, (64.62±0.15)%, (91.25±0.87)%, the comparative differences were statistically significant (F=1 993.60, 6 475.02, 9 984.47, with P values below 0.05). Comparing the chronic wound group with the general wound group and the micropar skin pulp group respectively on the 14th day of observation, the differences were statistically significant (t=89.90, 50.93, with P values below 0.05). Comparing the chronic wound group with the general wound group and the micropar skin pulp group respectively on the 21st day of observation, the differences were statistically significant (t=117.90, 116.10, with P values below 0.05). Comparing the chronic wound group with the general wound group and the micropar skin pulp group respectively on the 28th day of observation, the differences were statistically significant (t=86.43, 94.29, with P values below 0.05). On the 14th day of observation, hematoxylin-eosin staining was observed on the wound surface, a little new capillaries were observed in the general wound group, no obvious new capillaries were observed in chronic wound group, a large number of new capillaries were observed in the micropar skin pulp group.On the 14th day of observation, the immunohistochemical comparison of CD31 (The positive expression of CD31 was brown-yellow) showed that brown-yellow particles were scattered in the general wound group, while brown-yellow particles were sparsely distributed in the chronic wound group, and a large number of brown-yellow particles could be seen in the micropar skin pulp group.On the 14th day of observation, the comparison of microvascular density was observed, the comparison of microvascular density in the general wound group, the chronic wound group, the micropar skin pulp group were (49.20±17.96), (37.32±9.57), (64.93±20.29) (individual/field of view), the comparative differences were statistically significant (F=34.09, P<0.05), and the chronic wound group was compared with the general wound group, micropar skin pulp group, the differences were statistically significant (t=3.23, 11.50, with P values below 0.05).

Granulation tissue injection of micropan skin pulp can promote vascular proliferation in traumatic chronic wounds in rats, and the wound healing rate is significantly higher, and the wound healing time is shorter.