Eco matters; In & Out.

In vitro culture of cells and tissues were undertaken to understand the intricacies of cellular biology per se until recently, when such in vitro grown cells and tissues have started evolving as tools of regenerative medicine. Only after such clinical applications of in vitro cultured cells and tissues became a possibility, various criteria about the compatibility of in vitro environments to the cells and tissues have gained significant attention.

Among the in vitro cultured cells, chondrocytes pop up as one of the most approved cell-based products by regulatory authorities of many countries including the USA, Europe and Japan[. In this procedure, it has been reported by several studies that human articular chondrocytes (HACs) when cultured as monolayer, they tend to de-differentiate[ whereas 3D cultures help to establish the native hyaline phenotype[. Variations of such significance in the in vitro behaviour of other cell types have also been reported in literature[ which clearly demonstrate that in vitro environments play a crucial role in maintaining cells with the proper phenotype and functionality for clinical transplantation.

Another major factor which needs to be studied thoroughly is cellular senescence in the in vitro environment. Though cells derived from older individuals may share cellular and molecular phenotypes with in vitro senescent cells, in vitro acquired cellular senescence is a proven phenomenon[. While the ‘Hayflick limit’ specifies a particular number of maximum population doubling for a specific cell type in vitro, the same cell type in vivo may undergo more than the Hayflick limit specified population doubling in a lifetime without senescence[ creating the need for improvising current in vitro cell culture techniques to reflect what occurs in vivo.

Given the above background, the goal of in vitro cell and tissue engineering is to grow cells with optimal functionality while simultaneously preventing uncontrolled or premature differentiation and the onset of senescence[. Stressing the importance of in vitro environments, even regulatory agencies like the US-FDA use in vitro manipulation as a gauge to classify cell therapies[.

In this issue, a diverse assortment of articles ranging from the use of scaffolds for in vitro culture by Gomathysankar et al[ to employing tools for in vivo transplantation of cells by Maiti et al[and Fauzi et al[ have been published. During regenerative medicine applications, cells undergo several transitions across environments, starting with an in vivo to in vitro transition when harvested from the body and subjected to culture-expansion or tissue engineering kind of processing and then a reversal back to an in vivo environment. While the factors and materials employed in the in vitro eco-system are known, their effects are known though to an extent, some of their implications still remain unknown and the mechanisms of those implications are largely obscure[. These bunch of changes in the whole eco-system inside-out and vice versa need a meticulous and flawless assessment which is indispensable in improvising the clinical outcome of regenerative medicine applications.