Fig. 1. Phases of the oral mucosal wound defect regeneration. А. Granulation tissue containing macrophages and fibroblasts at the wound defect site (day 3, group 2; ×900; stain: toluidine blue). B. TGFβ1 expression by the granulation tissue cells at the wound defect site, hematoxylin staining of nuclei (day 3, group 1; 900×). C. Loose fibrous connective tissue at the wound defect site showing extensive cell infiltration (day 7, group 1; stain: hematoxylin and eosin; ×400). D. Differentiated fibroblast (day 7, group 2; TEM, 5000×). E. Dense fibrous connective tissue showing cell infiltration (day 12, group 1; stain: hematoxylin and eosin; 400×). F. Macroscopic features after the wound defect regeneration. Soft tissue loss. Scar, 4.5 mm in length. G. Fibrocyte showing no synthetic activity (day 12, group 2; TEM, 5000×). H. CD68 expression by the connective tissue cells, hematoxylin staining of nuclei (day 12, group 2; 400×). FT — dense fibrous connective tissue, I — cell infiltration, EU — euchromatin, HH — heterochromatin, RER — rough endoplasmic reticulum, М — mitochondrion, V — vesicles, MP — macrophage, FB — fibroblast; ++++ — very strong staining; +++ — strong staining; ++ — moderate staining; + — weak staining; ‒ — no detectable staining

Fig. 2. Scheme of the oral mucosal wound defect regeneration pathomorphogenesis in cases of using/not using a polymeric piezoelectric membrane. ↑ — slightly increased expression; ↑↑ — moderately increased expression; ↑↑↑ — markedly increased expression; ↓ — decreased expression. 1 — according to Morikawa M, Derynck R, et al. [5]; 2 — according to Xu X, Gu SУ, et al. [11]; 3 — according to Zhang T, Wang XF, et al. [12]