What is laminin’s role in the basement membrane formation and function?
The basement membrane (BM) and interstitial matrix are the two distinct types of extracellular matrix (ECM) found in multicellular organisms, and while they have overlapping functions such as providing structural support, they also differ significantly in their composition, organization, and functions(reviewed in 1).
The BM is a sheet-like ECM that is a relatively thin, dense structure that underlies or surrounds many types of tissues and cells, such as epithelial and connective tissues(reviewed in 2-4). BMs provide essential support for complex tissue formation and function; thus, it is logical that it plays an essential role in tissue shape, tissue force resistance, tissue repair, and many other functions.
The major structural elements of the basement membrane are laminin and type IV collagen polymeric networks that are connected with perlecan and nidogen(reviewed in 2-4). Laminin is a heterotrimeric glycoprotein that is essential for initiating BM assembly(reviewed in 5, 6), but also interacts with cell surface receptors, to regulate cell anchoring and signaling functions that modulate cell migration, polarity, differentiation, and proliferation. Thus, it is not surprising that genetic disruption or dysfunction in laminin assembly and function contributes to several human diseases(reviewed in 3, 5, 6).
While there has been significant breakthroughs in the laminin field such as solving laminin’s structure and effective classification of the 16 isoforms of laminin(reviewed in 5), several questions remain unanswered, such how does laminin contribute to BM stability, repair, and turnover; how does laminin influence the BM during specialized tissue development; and what is laminin’s role in supporting tissue structures in response to different mechanical forces.
Additional questions include, what is the precise role of each of the laminin isoforms, how do they interact with the more than 200 different basement membrane components(reviewed in 4), and what determines which components are present in the BMs of distinct tissue types. In order to effectively investigate these laminin questions, effective tools such as fluorescent laminins for microscopy studies, force measurement tools, specialized animal models, and others are needed. Below, we look at how fluorescent laminins have been used in assays addressing some of these critical laminin questions.
How are investigators using purified labeled laminin to study critical questions about laminin biology?
Purified laminin is an essential research tool that can be used in a variety of assays to help investigators precisely manipulate a critical ECM component to understand how it affects their target cell or tissue. Fluorescent laminin is particularly important as it allows investigators to validate micropatterning substrates, perform microscopy studies investigating the crosstalk between the BM and cells, and is invaluable when developing novel biomaterials and substrates; several of these applications are discussed below.
Studying how specialized substrates affect cellular function
Understanding how the composition, shape, structure and other properties of the surrounding ECM impacts a cells function is critical towards defining the role of the ECM in tissue formation and function. Investigators use fluorescently labeled laminin (LMN01 and LMN02) to create specialized substrates.
For instance, investigators grew epithelial cells in hollow alginate tubes supplemented with red fluorescent laminin (LMN01) and analyzed their changes via confocal imaging to see how the cell properties were impacted by growth in this environment7. In another example, a specialized electrically active hydrogel composed of alginate-laminin-and PEDOT:PSS was developed to use for in vitro neural cell cultures8.Fluorescently labeled laminin was used to validate proper laminin distribution in the electrically active hydrogels.
Another group used a polyacrylamide hydrogel coated with laminin to study how different substates affect neuronal differentiation and maturation9. HiLyte 488™ laminin (LMN02) was used to visualize the conjugation to these hydrogels. In a different approach, fluorescent laminin (LMN01) was also used to create an uneven ECM, by adding patches or clumps of laminin to transwell filters to study how it impacts monolayer “tissue-like” formation10.
Studying ECM patterning:
Understanding how ECM micropatterned substrates affect cell force, function, and signaling is critical to defining its role both physiologically and pathologically. Here are several examples where our fluorescent laminin was used to verify laminin micropatterning that was used to assess cell adhesion11, cell contraction12, 13, confined migration studies14, and others14.
Use of laminin for growth of specialized tissue
As investigators seek to further define the role of the basal membrane and/or laminin in tissue formation and function, it will be important to establish models with proper BM substrates. Recently, Fiore et al., sought to understand the impacts of the BM on tissue architecture as it relates to tumor progression15. Skin tissue was grown in the presence of fluorescently-labeled laminin (LMN01) followed by being embedding in OCT, antibody labeling of target proteins, and visualization via immunofluorescence microscopy.
