## 3 Results and Discussion
### Immunohistochemical Staining of Dorsal Skin Tissue in Nude Mice  
The epidermis consists of the stratum basale, stratum spinosum, stratum granulosum, and SC. The physical barrier of the skin is composed primarily of the SC and tight junctions (TJs) [51]. The SC forms a continuous layer of keratinocytes, which serve as the first line of defense of the skin, whereas TJs control the permeability of substances such as small molecules, electrolytes, and water while preventing pathogen invasion [33]. TJs are composed primarily of two multiprotein complexes. The transmembrane protein claudin-1 is expressed abundantly in keratinocytes and directly interacts with cytoplasmic plaques [52]. Claudin-1-deficient mice exhibit abnormalities in the stratum granulosum and, in severe cases, die within one day of birth [53]. The basement membrane (BM) is a multimolecular structure composed primarily of laminin and type IV collagen. It is firmly  
Figure 6: Effects of the administration of LPTWK10 viable cells or LPTWK10 spray-dried supernatant powders on dorsal histopathological findings (**A–I**) H&E stain, (**J**) epidermis thickness level and (**K–S**) MT stain in UVB-induced nude mice. (**A,K**) NC, (**B,L**) UVB, (**C,M**) PC, (**D,N**) LPLD, (**E,O**) LPMD, (**F,P**) LPHD, (**G,Q**) SPLD, (**H,R**) SPMD, and (**I,S**) SPHD. Original magnification, 400\(\times\); scale bar = 100 \(\upmu\)m. Data are presented as mean \(\pm\) SD (\(n\) = 7 or 8). H&E: hematoxylin and eosin; UVB: ultraviolet B; NC: normal control; PC: positive control; LPLD, LPMD and LPHD: administration of LPTWK10 viable cells at 2 \(\times\) 10\({}^{8}\) CFU/kg bw/day, 2 \(\times\) 10\({}^{9}\) CFU/kg bw/day and 2 \(\times\) 10\({}^{10}\) CFU/kg bw/day, respectively; SPLD, SPMD and SPHD: administration of LPTWK10 spray-dried supernatant powders at 0.30 g/kg bw/day, 0.60 g/kg bw/day, and 1.20 g/kg bw/day, respectively. Black arrow: epidermis thickness. Values with different uppercase letters were significantly different by [PERSON]’s multiple range test (\(p<0.05\)). anchored between the epidermis and dermis and can regulate epidermal differentiation, proliferation, and epidermal-dermal interactions. UV-induced damage to the BM results in the formation of a multilayered structure that contributes to the aging of the dermis and epidermis [54; 55]. Increased ROS levels are a key factor in skin photoaging. Following UV irradiation, ROS are generated in the epidermis and dermis, resulting in the degradation of the BM and ECM, disruption of cell-cell adhesion, and apoptosis, ultimately leading to the disruption of barrier function and reduction in the water content of the skin [23; 55]. Figures 7-9 show the immunohistochemical staining results of dorsal skin tissue sections, wherein target proteins appear brown. At week 13, claudin-1, laminin, and type IV collagen levels in the dorsal skin tissues of the UVB-treated group were lower than those in the NC group. These levels increased in all three groups on treatment with LPTWK10 or the spray-dried LPTWK10 supernatant at low, medium, and high doses. The results indicate that LPTWK10 or the spray-dried LPTWK10 supernatant decelerates the degradation of claudin-1, laminin, and type IV collagen proteins in the skin, thereby ameliorating the impairment of skin barrier function. In addition, the increase in stratum corneum hydration observed in our results may be linked to the ability of LPTWK10 to enhance the skin barrier function, thereby reducing moisture loss and improving overall skin hydration levels. Figure 7: Effects of the administration of LPTWK10 or LPTWK10 spray-dried supernatant powders on dorsal immunohistochemistry stain (claudin-1) in UVB-induced nude mice. **(A)** NC, **(B)** UVB, **(C)** PC, **(D)** LPLD, **(E)** LPMD, **(F)** LPHD, **(G)** SPLD, **(H)** SPMD, and **(I)** SPHD. Original magnification, 100\(\times\); scale bar = 200 \(\upmu\)m. Data are presented as mean \(\pm\) SD (\(n\) = 7 or 8).