The assessment of the protective impact of spidroin extract against UV-A radiation damage by using earthworms (Aporrectodea caliginosa) as a robust human skin model via macroscopic and histological observations

Abstract

Numerous studies have confirmed the damage caused by excessive exposure to ultraviolet-A rays. Malignant melanoma and skin cancer are two of the most serious health consequences. Thus, the UV-A protectant is intended to protect the skin, especially the two primary layers of skin (epidermis that represents the interface between the body and its surroundings and dermis). Spider silk is the most powerful natural fibre due to its regeneration, biocompatibility, antimicrobial, wound healing, antiseptic, and blood clotting properties. This work targeted to determine the protective effect of spidroin extract against UV-A radiation damage. Earthworms Aporrectodea caliginosa were collected from Assiut University's farm. Each set of ten earthworms was separated into six groups and placed in a plastic container. Webs of spiders collected from trees and old houses. Spidroin was extracted and utilised in this work to determine the potential effects of topical application on UV-A protection. The experiment is divided into two sections: (1) UV-A exposure and (2) the use of spidroin extract to protect the earthworms from ultraviolet radiation. Two control groups (1،2) of worms were not received UV-A exposure, and four groups (3,4,5,6) were exposed to UVR-A. In contrast, groups (5,6) were received spidroin extract before exposure to UV-A. Each group from the groups (3,4,5,6) was exposed for three consecutive days (¼ hour/day, ½ hour/day, and 1 h/day), using a UV-Lamp with a wavelength of 366 nm. The histopathological changes revealed that after 1⁄4 h of UV exposure, the cuticle was swollen with a slightly detached epithelium. The cuticle was down after 1⁄2 h of exposure, and the epidermis was totally damaged and necrosed. After 1 h, the exposure showed destruction of the epidermis in the circular muscle with a loss of muscle filament integrity, varying size, and altered nucleus form, along with mild disintegration of longitudinal muscle. Spidroin extract is critical for earthworm protection against UV-A radiation damage and able to regeneration. For the first time, morphological and histological analysis was established to detect the Spidroin extract evaluated for topical application on earthworms. Earthworms can be considered as a robust human skin model prior to UV-A exposure. It induces a complete protective effect against UV-A radiation damage in earthworms.

Keywords: Aporrectodea caliginosa; Earthworm; Spidroin extract; UV-A radiation.

Fig. 1

Macroscopic observation of earthworms (Aporrectodeacaliginosa) (A) the control group (1) and(B,C,D,E and F) control regenerated (group, 2) regeneration of earthworms (A.caliginosa) after induction of surgical wounds and examination of wound healing and regeneration; worms were left untreated to the mercy of natural healing and cut in the first six segments (circle).per.(peristomium), pro.(prostomium)

Fig. 2

Tissue structure of (Aporrectodea caliginosa) (A) group (1) (control group) showed normal structure of earthworm: cuticle (C), epidermis (Ep) arrow, circular muscle (C.M.) and longitudinal muscle (L.M.), Histopathological changes in group (3) (B) After ¼ hr exposure, the cuticle (Cu) swelled with slightdetached epithelium (arrow), (C) After ½ hr exposure showed Slight desquamation of epithelial layer, (D) After 1 h exposure showed complete necrosis and desquamation of epithelium. H&E. bar = 50 µm

Fig. 3

Tissue structure of (Aporrectodea caliginosa) (A) (control group 2) showed normal structure of earthworm: wall cuticle (C), epidermis (Ep) arrow, circular muscle (C.M.) and longitudinal muscle (L.M.), Histopathological changes in group (4) (B) After ¼ hr exposure showed cloudy swelling and progressivehypertrophy of the epidermis(arrow), (C) After ½ hr exposure, the cuticle shows breakdown, and the epidermis completely damaged and necrosed, (D) After 1 h exposure showed complete destruction of the epidermis accompanied with of necrosis circular muscleand mild disintegration of longitudinal muscle (H&E. bar = 50)

Fig. 4

Macroscopic observation of (A): the earthworms of group(4) after UV-A exposure,(B), the earthworms of group(5) after UV-A exposure,(C): the earthworms of group(6) after UV-A exposure. Photomicrograph of: Tissue structure of (Aporrectodea caliginosa) (D,E),group(4)(E,H),group(5)and (F,I),group(6): cuticle (C), epidermis (Ep) arrow, circular muscle (C.M.) and longitudinal muscle (L.M.). H&E. bar = 50 µm

Fig. 5

Mortality of earthworms (Aporrectodea caliginosa) after UV-A exposure: (A, B, C) group(3) and (D,E and F)group (4), Shows significant mortality after exposure to UV-A (one-way ANOVA, N = 10, P < 0.001)

Fig. 6

Mortality of earthworms (Aporrectodea caliginosa)after UV-A exposure: (A, B, C) group(5) and (D,E and F)group (6), Shows significant mortality after exposure to UV-A (one:way ANOVA, N = 10, P < 0.0001)

Fig. 7

Mortality of earthworms (Aporrectodea caliginosa) after UV-A exposure in groupa(3,4,5 and 6) for three days