HOW TO CULTURE CARDIAC CELLS ON LAMININ SUBSTRATES

Laminin expression in muscle tissue

Laminin-211 and laminin-221 are expressed specifically in the basal lamina of striated muscles and an expression deficiency in the alpha-2 laminins results in muscular dystrophy, accompanied by a dilated cardiomyopathy (Oliviéro, 2000). Laminin isoforms containing the alpha-2, -4 and -5 subunits are critically important for the maintenance and development of heart muscle tissue (Miner, 1997). During stem cell cardiac differentiation, a distinct swish in expression profile of laminin subunits have been reported with laminin-411/421 pre-dominantly expressed early in progenitors and laminin-211/221 expressed later in cardiomyocytes (Ja, 2015). In the adult heart, the main laminin isoforms expressed are laminin-211 and laminin-221 but laminin-521 has also shown to be expressed.

Effective cardiomyocyte differentiation on laminin-211 and laminin-521

In a publication by a group of Japanese scientist, they have shown that with the use of cardiac muscle specific laminin-211, human iPSCs can be effectively be differentiated into cardiomyocytes using small molecules (Minami, 2012). The same researches later published another article with Shinya Yamanaka as co-author, where they again used laminin-211 for cardiac differentiation of human iPSC (Hirata, 2014). Laminin-211 has also been used for culture of adult human cardiomyocytes (Kuroda, 2015).

Laminin-521 also has properties that improves isolation and expansion of adult stem cells and progenitors. In a publication by Kuroda et al., iPSCs were efficiently expanded and differentiated to cardiomyocytes on laminin-521 (Kuroda, 2015). Dr. Joseph Wu´s lab also showed that laminin-521 is an optimal matrix for chemically defined differentiation of human iPSC to cardiomyocytes (Burridge, 2014). Laminin-521 was compared to 5 other feeder-free matrices and the authors concluded that:

• Laminin-521 had the fastest human iPSC growth rate
• Laminin-521 generated the highest number of cardiomyocytes
• Only laminin-521 could sustain long-term adhesion (>15 d) during cardiac differentiation in chemically defined medium

This in in coordance with recent data presented by researchers at Icagen Inc. demonstrate that the laminin-521 cell culture matrix maintains the differentiation potential of mouse and human satellite cell-derived myoblasts, even during long-term culture expansion (Penton, 2016). Laminin-521 support increased proliferation during expansion and superior differentiation with myotube hypertrophy, larger myotubes and higher amounts of nuclei per myotube. Moreover, Penton et al. show that laminin-521 support more consistent and reliable differentiation over long-term culture and is the only substrate facilitating high-level fusion following long-term culture. Laminin-521 support increased differentiation potential without altering the traditional Pax7/MyoD paradigm and the results are translational across several mouse backgrounds, human cells and disease states.