Poly(ethylene glycol) diglycidyl ether (PEGDE) is widely used to cross-link polymers, particularly in the pharmaceutical and biomaterial sectors. However, the subcutaneous toxicity of PEGDE has not yet been assessed. PEGDE samples (500–40,000 μg/mouse) were subcutaneously injected into the paraspinal dorsum of BALB/c male mice. Cage-side observations were carried out with measurement of organ weight, body weight variation, and feed intake, as well as histopathological characterization on day 28 post-exposure. Mice that received 40,000 μg of PEGDE showed severe toxic response and had to be euthanized. Subcutaneous injection of PEGDE did not alter feed intake and organ weight; however, the body weight variation of mice injected with 20,000 μg of PEGDE was significantly lower than that of the other groups. Exposure to 10,000 and 20,000 μg of PEGDE induced epidermal ulcer formation and hair loss. The histology of skin tissue in mice administered with 20,000 μg of PEGDE showed re-epithelialized or unhealed wounds. However, the liver, spleen, and kidneys were histologically normal. Collectively, PEGDE, particularly above 10,000 μg/mouse, caused subcutaneous toxicity with ulceration, but no toxicity in the other organs. These results may indicate the optimal concentration of subcutaneously injected PEGDE.

Prolactin is essential for mammary gland development and lactation. Progesterone also induces ductal branching and alveolar formation via initial secretory differentiation within the mammary gland. Herein, we aimed to evaluate the role of progesterone as a prolactin substitute for the production of cell-cultured milk components in MAC-T cells. Cells were treated with various hormones such as prolactin (PRL), progesterone (P4), 17β-estradiol (E2), cortisol (COR), and insulin (INS) for 5 d. MAC-T cells cultured in a P4 differentiation media (2500 ng/mL of P4, 25 ng/mL of E2, 25 ng/mL of COR, and 25 ng/mL of INS) showed similar levels of E74-like factor 5 (Elf5) and milk component synthesis (α-casein, β-casein, α-lactalbumin, β-lactoglobulin, and triglycerides) compared to those cultured in a PRL differentiation media (5000 ng/mL of PRL, 500 ng/mL of CORT, and 50 ng/mL of INS). The levels of α-casein and triglycerides in the optimal P4 differentiation media were present at comparable levels to those in the PRL differentiation media. Our results demonstrated that P4 induces the activation of Elf5 and the synthesis of milk components in MAC-T cells, similar to PRL. Therefore, P4 may be used as an effective substitute of PRL for cell-cultured milk production in in vitro frameworks.

Cultivated meat relies on the production of muscle tissue using cell culture techniques. Myogenesis is a cellular differentiation process in which muscle satellite cells (SC) transform into myoblasts, or myotubes. The extracellular matrix (ECM) plays a pivotal role in meat quality, myogenesis, SC proliferation, and muscle tissue development to replicate meat texture. Because fibrotic differentiation and ECM are involved in the myogenic process, we aimed to induce myogenesis in SC using fibrotic differentiation of adipose tissue-derived mesenchymal stem cells (ADSC). ADSC, fibroblasts (FC), and SC were isolated from the back fat, ear margin tissues, and femur muscle tissues, respectively, of a 1-year-old Berkshire piglet. ADSC were treated with connective tissue growth factor (CTGF; 0, 12.5, 25, or 50 ng/mL) for 72 h to induce fibrotic differentiation. Conditioned media from differentiated ADSC and FC were prepared and labeled CA-CM and F-CM, respectively. SC were exposed to CA-CM or F-CM to assess their effects on myogenesis. The results demonstrated α-smooth muscle actin and collagen I as the optimal markers for assessing fibrotic differentiation in ADSC. CTGF significantly elevated both mRNA and protein expression of α-smooth muscle actin and collagen I (P < 0.05), suggesting that CTGF acts as an inducer of fibrotic differentiation in ADSC. Moreover, CTGF elevated the expression of ECM components (laminin, fibronectin, and collagen I) in ADSC (P < 0.05). mRNA expression of myogenesis-related genes (MyoG, MyoD, Myf5, and Myf6) increased in SC exposed to both CA-CM and F-CM (P < 0.05). Our data revealed that fibrotic differentiation of ADSC increased ECM production, and ECM-containing conditioned medium induced myogenesis in SC. These findings indicate that ECM-containing conditioned medium is a good option for enhancing myogenesis in SC, with potential implications for cultivated meat production.