Protein composition and biomechanical properties of in vivo-derived basement membranes

Abstract

Basement membranes (BMs) evolved together with the first metazoan species approximately 500 million years ago. Main functions of BMs are stabilizing epithelial cell layers and connecting different types of tissues to functional, multicellular organisms. Mutations of BM proteins from worms to humans are either embryonic lethal or result in severe diseases, including muscular dystrophy, blindness, deafness, kidney defects, cardio-vascular abnormalities or retinal and cortical malformations. In vivo-derived BMs are difficult to come by; they are very thin and sticky and, therefore, difficult to handle and probe. In addition, BMs are difficult to solubilize complicating their biochemical analysis. For these reasons, most of our knowledge of BM biology is based on studies of the BM-like extracellular matrix (ECM) of mouse yolk sac tumors or from studies of the lens capsule, an unusually thick BM. Recently, isolation procedures for a variety of BMs have been described, and new techniques have been developed to directly analyze the protein compositions, the biomechanical properties and the biological functions of BMs. New findings show that native BMs consist of approximately 20 proteins. BMs are four times thicker than previously recorded, and proteoglycans are mainly responsible to determine the thickness of BMs by binding large quantities of water to the matrix. The mechanical stiffness of BMs is similar to that of articular cartilage. In mice with mutation of BM proteins, the stiffness of BMs is often reduced. As a consequence, these BMs rupture due to mechanical instability explaining many of the pathological phenotypes. Finally, the morphology and protein composition of human BMs changes with age, thus BMs are dynamic in their structure, composition and biomechanical properties.

Vital dyes increase the rigidity of the internal limiting membrane

“…Previous AFM studies showed that the mechanical strength is in the mPa range, very similar to the articular cartilage and about 1000-fold stronger than cell layers. 18,24,25 Our results underline previous reports 20 describing that the average stiffness of the ILM is over fivefold higher at the retinal side as compared with the vitreal side. This difference nicely explains the fact that the ILM curls up towards its vitreal side after peeling.…”

The extracellular matrix in breast cancer predicts prognosis through composition, splicing, and crosslinking

“…The BM subtending the retina (which has a similar laminin-rich composition) has a modulus between 1 and 4 MPa, with a difference in matrix biomechanics between its two faces [38], suggesting that despite the thinness of this structure it specializes into sides.…”

“…Breast cancer is not a single disease [38]: breast cancer prognosis varies with expression of key hormone receptors: estrogen receptor (ER), progesterone receptor (PR) and her2/neu/ ERbB2 (Her2) [56] histologic grade [57], and presence of metastasis. Recent evidence suggests that the microenvironment in these tumors is different [58,59].…”

Biomaterials for spinal cord repair

“…Previously, it was shown that various basement membranes containing a full arsenal of ECM molecules enhance neurite outgrowth in vitro [73,74] and axonal extension in the lesioned adult brain [74] . Basement membrane is a specific type of ECM secreted by support cells and composed of >20 different molecules [75] . They are of specific interest for axon regeneration due to their crucial role in regeneration in the damaged peripheral nerve [76] .…”

“…Basement membrane is a specific type of ECM secreted by support cells and composed of >20 different molecules [75] . They are of specific interest for axon regeneration due to their crucial role in regeneration in the damaged peripheral nerve [76] .Although it is typically difficult to isolate and manipulate these fragile substrates without causing damage, recent advances have made successful isolation of various basement membranes possible [75] . Several combination ECM materials isolated from mammalian sources are commercially available [52,77] , while others are in various stages of development and characterization [19,[78][79][80] .…”