Low Oxygen Tension and Synthetic Nanogratings Improve the Uniformity and Stemness of Human Mesenchymal Stem Cell Layer

A free-standing, robust cell sheet comprising aligned human mesenchymal stem cells (hMSCs) offers many interesting opportunities for tissue reconstruction. As a first step toward this goal, a confluent, uniform hMSC layer with a high degree of alignment and stemness maintenance needs to be created. Hypothesizing that topographical cue and a physiologically relevant low-oxygen condition could promote the formation of such an hMSC layer, we studied the culture of hMSCs on synthetic nanogratings (350 nm width and 700 nm pitch) and either under 2 or 20% O-2. Culturing hMSCs on the nanogratings highly aligned the cells, but it tended to create patchy layers and accentuate the hMSC differentiation. The 2% O-2 improved the alignment and uniformity of hMSCs, and reduced their differentiation. Over a 14-day culture period, hMSCs in 2% O-2 showed uniform connexon distribution, secreted abundant extracellular matrix (ECM) proteins, and displayed a high progenicity. After 21-day culture on nanogratings, hMSCs exposed to 2% O-2 maintained a higher viability and differentiation capacity. This study established that a 2% O-2 culture condition could restrict the differentiation of hMSCs cultured on nanopatterns, thereby setting the foundation to fabricate a uniformly aligned hMSC sheet for different regenerative medicine applications.