Laminins, a family of 16 distinct ECM proteins, are crucial for tissue formation, maintenance, and homeostasis, with expression tightly regulated in space and time. As key components of basement membranes (BM), intact laminins are vital for healthy tissue function, while mutations in laminin genes result in diseases like Pierson syndrome and Epidermolysis bullosa, affecting organs such as muscles, nerves, and skin.

Laminin proteins interact with integrin and non-integrin receptors, such as dystroglycan and syndecan, and bind essential growth factors (GF), modulating GF release. As large trimeric proteins, intact laminins provide structural integrity and bioactivity critical for BM functionality. In contrast, fragmented laminins lack these properties, are not naturally produced in healthy tissues, and fail to support tissue homeostasis. Studies show pluripotent stem cells (PSCs) with LAMA5-KO cannot survive without exogenous laminin 521, supporting the essential role of laminin 521 for PSC survival and expansion.

Our study demonstrates the superiority of full-length recombinant laminin-521 in supporting human PSCs compared to fragmented laminins. Full-length laminin-521 significantly enhances PSC survival, proliferation, and migration, enabling single-cell seeding without the need for ROCK inhibitors. Importantly, PSCs cultured on intact laminin-521 exhibit enhanced migratory capacity, achieving complete wound closure in migration assays, whereas fragmented laminins support only 50% closure under the same conditions.

These findings highlight the importance of full-length laminin-521 in recreating natural cellular microenvironments, which is crucial for advancing PSC culture techniques, improving differentiation protocols, and refining disease modeling and gene-editing strategies.