Editing Tissue engineering (section)

=== Cell sources ===
[[File:Mouse embryonic stem cells.jpg|thumb|[[Mus musculus|Mouse]] [[Mammalian embryogenesis|embryonic]] stem cells]]

''Primary cells'' are those directly isolated from host tissue. These cells provide an ex-vivo model of cell behavior without any genetic, epigenetic, or developmental changes; making them a closer replication of in-vivo conditions than cells derived from other methods.<ref>{{cite web | vauthors = Welser, Jennifer, et al. | title = Primary Cells Versus Cell Lines | publisher= ScienCell Research Laboratories | date = November 2015 |url=https://sciencellonline.com/blog/primary-cells-versus-cell-lines/}}</ref> This constraint however, can also make studying them difficult. These are mature cells, often terminally differentiated, meaning that for many cell types proliferation is difficult or impossible. Additionally, the microenvironments these cells exist in are highly specialized, often making replication of these conditions difficult.<ref>{{cite book | vauthors = Buttery LD, Bishop AE | title = Biomaterials, Artificial Organs and Tissue Engineering| chapter = Introduction to tissue engineering | volume = 279 | issue = 5349 | pages = 193–200 | date = 2005 | doi = 10.1533/9781845690861.4.193| isbn = 9781855737372}}</ref>

''Secondary cells'' A portion of cells from a primary culture is moved to a new repository/vessel to continue being cultured. Medium from the primary culture is removed, the cells that are desired to be transferred are obtained, and then cultured in a new vessel with fresh growth medium.<ref>{{cite book | vauthors = Malik, Parth, et al. | title = Practical Approach to Mammalian Cell and Organ Culture | chapter = Mammalian Cell Culture Types and Guidelines of Their Maintenance | publisher= Springer Nature | date = January 2023 | pages = 233–259 | doi = 10.1007/978-981-19-1731-8_6-2 | isbn = 978-981-19-1730-1 |chapter-url=https://link.springer.com/referenceworkentry/10.1007/978-981-19-1731-8_6-2}}</ref>  A secondary cell culture is useful in order to ensure that cells have both the room and nutrients that they require to grow. Secondary cultures are most notably used in any scenario in which a larger quantity of cells than can be found in the primary culture is desired. Secondary cells share the constraints of primary cells (see above) but have an added risk of contamination when transferring to a new vessel.{{cn|date=April 2025}}