Cell culture conditions: from outer space-like conditions to the mimicking of complex in vivo environments

Dear Readers, Imagine yourselves at the outer space, the void that lies beyond the uppermost reaches of the earth's atmosphere, comprising all other objects in the universe 7. Although it is a void, outer space may be thought of as an environment, where unprotected humans would perish. The principal environmental characteristic of outer space is the vacuum, where gas molecules are practically nonexistent and pressure is nearly zero, whose net effect on a human body would be unconsciousness and massive tissue damage in few seconds. The temperature range found in outer space also comprises a major obstacle, along microgravity and different types of radiation 7. Getting trouble in wondering such completely different environment? The multiple Oscar laureate movie picture "Gravity" 4 can give us an astonishing picture of this scenario. Interestingly, with scientific accuracy the movie opening title card states: " At 600KM above planet earth the temperature fluctuates between +258 and-148 degrees Fahrenheit. There is nothing to carry sound. No air pressure. No oxygen. Life in space is impossible ". Obviously, the outer space exploration relies on scientific advances to mimic at outer space environment the minimal conditions that support human life, at least for a given time period. Back from outer space reverie to 'regular' laboratory science, where usually we try to mimic at dishes, flasks and wells environments the minimal conditions that support cell life in vitro. As non-adherent cells, lymphocytes float in culture media similarly to humans at microgravity. Floating through a room/culture flask does not reproduce the standard routine of human and leukocytes, and consequently, impact the outcome of its biological process and responses. Indeed, it is more than clear that 'providing minimal conditions for maintaining cells alive' is not enough to fully mimick in vivo tissue environment 9. Given the recent advances in the understanding of the mechanobiology of cellular functions 10 , the necessity of reproducing in vitro the extracellular matrix derived mechanical support, and consequently resulting signals, became evident. even in the case of adherent leukocytes, it has becoming clear that biological outcome of the adhesion in plastic surfaces differs from the adhesion in surfaces that resemble the extracellular matrix. Importantly, the raise and evolution of 3D culture systems seems to meet the expectation of researchers from different fields to improve in vitro systems. In a more ambitious endeavor, 3D printing of complex cellular scaffolds has experienced considerable improvement, not only in …