Introduction: The result of the regeneration of the cut nerve trunk depends on the regeneration of its specific components (restoration of function) and the nonspecific plastic properties of the connective tissue (scar formation). These processes are in a certain balance, which depends on many factors.

Aim: is to study the features of the developing regenerative neuroma (RN) of the sciatic nerve under conditions of granulocyte colony stimulating factor (G-CSF) modulation.

Materials and methods: The work was performed on 40 male Wistar rats. They were  undergone neurotomy of the right sciatic nerve. 20 animals were injected subcutaneously with G-CSF (Lenograstim) at a dose of 50 mg / kg from 1 to 3 days of the experiment. The rest of the animals (control) were injected an equivalent volume of saline. Harvesting of the nerve and then general histological examination of the neuroma was performed 1, 3, 7, and 14 days after neurotomy.

Results: It was shown that G-CSF, despite a significant increase in blood leukocytes on days 1 and 3 of the experiment, reduced the inflammatory infiltration of RN, primarily by granulocytes (3, 7 and 14 days). In this case, the number of fibroblastic cells was less than in the control and connective tissue fibers were formed in a smaller volume. The forming regenerate had more newly formed thin-walled blood vessels. From the side of the ends of the severed RN nerve, Schwann cells actively penetrated, gradually forming cords. They often had a larger volume than in the control. In the composition of the forming RN, starting from day 3 of the experiment, and on subsequent days, large, rounded or irregularly shaped cells with a rounded small homogeneous nucleus and abundant weakly basophilic cytoplasm were found in a significant amount. They visually differed from macrophages, and their number was higher than lymphocytes, in some areas by 10 times. On the 14th day of the experiment, they could form strands, fields of different sizes. Visually, it looked like an accumulation of homogeneous cells in the lacunae.

Conclusions: Under conditions of action of high doses of G-CSF, inflammatory infiltration and plastic reaction of the connective tissue in the developing RN are inhibited. The process of penetration into the RN of Shavnov’s cells is somewhat activated. Cells appear in the RN and gradually accumulate until the 14th day, but they visually cannot be unambiguously attributed to neural, connective tissue or hematogenous.