Mesenchymal stem cells

Laminin 521 is widely expressed in the bone marrow and is an efficient substrate for MSC adhesion and proliferation

Laminins are widely expressed in bone marrow, synthesized by human bone marrow stromal cells. The laminin α4 and α5 chain isoforms (laminin 411, 421, 511 and 521) are the most abundant laminin isoforms but laminin 332 and laminin 211 are also expressed (Siler, 2000; Klees, 2005; Gu, 1999; Yang, 2015). In a recent protocol for bone marrow mesenchymal stem cells (MSCs) culture from Yang et al., the authors show that coating with both Biolaminin 521 and 511 significantly increases the adhesion of bone marrow stromal cells (BMSCs) cultures compared to BSA coated or uncoated plates. Moreover, the protocol can easily be translated to MSCs from different origins (Yang, 2016).

This study is supported by a publication by Jiang et al. where the authors show that mesenchymal stem cell sheets attach dose-dependent onto Biolaminin 521-coated nanodot films. The coating improved cell adhesion as well as proliferation and after harvesting by a light-induced detachment method, the cells were viable and did not have any significant DNA oxidative damage. In addition, the sheets maintain multilineage potential, including osteogenic, adipogenic, and chondrogenic differentiation (Jiang, 2017). In addition, scalable process development has shown that the use of Biolaminin 521 provides more consistent bioprocesses, shorter process time and reduction in Cost of Goods (unpublished data).

Laminin 332 has also been shown to be an important component of the bone marrow microenvironment and expressed by bone marrow-derived MSCs in culture (Siler, 2002: Klees, 2005; Hashimoto, 2006). Incubation of MSCs in the presence of a coated or soluble form of laminin 332 effectively promotes attachment and proliferation while keeping their differentiation potential (Hashimoto, 2006). Laminin 332 has also shown to be a strong adhesive substrate for a small subpopulation of bone marrow mononuclear cells and for peripheral blood platelets (Siler, 2002). 

Integrin alpha-6 is a stemness marker of bone marrow MSCs and is a major receptor of laminin 521

Laminin 521 is a strong inducer of α6 integrins. In bone marrow MSCs, integrin α6 is preferentially expressed in fetal and early progenitor cells present in low‐passage, low‐density cultures and the integrin α6 expression of BMSCs gradually decreases during in vitro passaging (Yang, 2015). Integrin α6‐positive MSCs also possess higher CFU‐F formation ability and differentiation potential than integrin α6-negative cells (Lee, 2009; Yang, 2015). In a study by Yang et al., the authors show integrin α6 is a stemness marker of BMSCs which is correlated with cell adhesion on Biolaminin 521 and 511. Pre‐blocking of integrin α6 on BM-MSCs inhibit the adhesion of fetal BM-MSCs to these laminin substrates and dramatically decrease the differentiation of BM-MSCs (Yang, 2015). Moreover, inflammatory conditions have been shown to down-regulated integrin α6 in BM-MSCs resulting in decreased adhesion to laminins, impaired differentiation and increased migration (Yang, 2015). Integrin α6 also enhances multipotency and maintains the stemness of umbilical cord blood‐derived MSCs and hESCs through the direct regulation of the pluripotency factors OCT4 and SOX2 (Yu, 2012).

Adhesion of MSCs to laminin 332 activates ERK signaling pathways, inducing osteogenic differentiation

Adhesion of MSCs to laminin 332 via the α3B1 integrin has been shown to activate extracellular signal-related kinase (ERK), inducing osteogenic differentiation (Klees, 2005). Contrary, when laminin 332 is present in the differentiation medium it has been shown to suppresses the chondrogenic differentiation of MSC (Hashimoto, 2006). Laminin 332 activates ERK 1 and ERK 2 signaling pathways, consequently leading to the expression of osteogenic marker genes (osteopontin, osteocalcin, and ALP). In addition, both the γ2 and α3 chain of laminin 332 contains potential cysteine-rich regions that may bind bone morphogenic proteins (BMPs) and thereby induce differentiation of osteoprogenitor cells (Klees, 2005).

Laminin alpha-4 influences adipose tissue structure and function in a depot-specific manner

MSCs which undergo adipocyte differentiation increase the expression of all the structural components, including laminin 421 and 411. The α4 chain of laminin is also present in the BM surrounding fully differentiated adipocytes. Both in vitro-produced adipocytes and/or tissue fat cells have been shown to express laminin 411 as well as the integrin receptor α6β1, which is the major adipocytes laminin receptor (Noro, 2013; Vaicik, 2014).

Protocol:

Bone marrow mesenchymal stem cells adhesion assay