Co-Culture of Mammalian Cells and Photosynthetic Microorganisms for Oxygen Supply in Engineered Tissues.

Ensuring an adequate supply of oxygen remains a significant challenge in the development of large engineered tissue constructs in the field of tissue engineering. To address this, novel strategies have recently been introduced, including the incorporation of photosynthetic microorganisms into engineered tissues. However, to take the full advantage of this co-culture approach, careful selection of photosynthetic microorganisms and a better understanding of their long-term interactions with mammalian cells are required. Here, we first examined the effects of continuous 28-day light exposure on the proliferation and biofunctionality of mammalian cells. We observed that articular cartilage-derived chondroprogenitor cells (ACPCs) did better withstand light exposure under chondrogenic conditions than mesenchymal stromal cells (MSCs). Next, four different photosynthetic microorganisms, capable of growing at 37°C, were co-cultured with cartilage cells. Among them, Leptolyngbya sp. (Leptolyngbya) and Synechococcus sp. (Synechococcus) did not compromise the morphology and chondrogenic capacity of mammalian cells in vitro over 28 days, whereas Chlorella sorokiniana (Chlorella) inhibited chondrogenesis. This inhibition might due to excessive oxygen release by Chlorella in chondrogenic culture medium, as Leptolyngbya and Synechococcus did not produce detectable oxygen under the same culture conditions. To further explore their potential for oxygen delivery to other tissue-derived cells, we also assessed the growth rate and oxygen production of these four microorganisms in different mammalian cell culture media. We found that the composition, especially the presence of trace elements in tissue medium, critically influenced oxygen production. The tested microorganisms were able to grow and release oxygen in different mammalian cell culture media typically used for the propagation of cardiac, cartilage and liver cells, highlighting their flexible metabolic pathways across the different environments. This study emphasizes the importance of carefully selecting photosynthetic microorganisms for different tissue types, ensuring a balance between oxygen production and the specific nutritional demands of mammalian cells.