Regulatory Issues: Down to the Bare Bones - Engineered Bone: Tissue Engineering Intelligence Unit - page 214

Prerequisites for Cell Banks (If the Cell/Biological Component
of a Composite Is Retrieved from or Storaged Into)
The current guideline suggests to preserve any specific and characterized cell population
in a cell bank to be able to recover the cell population used for somatic therapies. This may
not be feasible for therapeutical applications, such as in the case of cartilage reconstruction
where the autologous chondrocytes are few and can be expanded for a limited amount of
cycles. 18 The “bank” itself should be composed of the “main storage cell bank” (MCB) and
of a “working cell bank” (WCB). 11 The MCB is defined as the collection of aliquots of
homogeneous cell populations that have been previously characterized in terms of genotype,
phenotype, biological functions and purity and that, when feasable, were obtained by clonal
expansion. The MCB must be preserved in at least three different locations in appropriate
liquid nitrogen containers.
The WCB is the collection of the aliquots of an homogeneous cell population obtained
from a single aliquot of the MCB via in vitro amplification for a defined amount of time and/
or cell cycles. Cell culturing conditions must be described in detail. Aliquots, obtained either
from the MCB or the WBC cannot be reinserted in the bank once used. The cellular compo-
nent of the composite originates from one WCB aliquot.
Procedural operations performed to constitute an MCB or a WCB must be described in
detail. Issues related to the cryopreservation of the cells are critical. The specific protocols must
indicate:
• the composition of the preserving solution. Several solutions are commercially available. It
is mandatory that cryopreservants are eliminated from the cell suspension before use. A low
toxicity at the concentrations used and a total absence of mutagenicity effects are also man-
datory;
• the precise temperature at which cells must be preserved; alarmed and backed-up systems
are required for -80 ° C freezers and liquid nitrogen containers to prevent power and/or
temperature failures. Upper and lower limits for working temperatures must be determined;
• the maximal duration of the preservation time for every manufactured product (to be esti-
mated with proper experiments if not available);
• operational procedures and timings for freezing and thawing passages (in most cases, cyto-
toxicity of the cryopreservants at standard room temperature imposes an extremely rapid
thawing procedure);
• the detailed description of all the parameters to assess the cell viability in the in the ex-
panded cell population on a short and long term (colony forming efficiency and life span,
respectively). Procedure must grant a defined percentage of viable cells;
• the precise location of each container. Aliquot amount and identity of each cell/tissue com-
ponent should be recorded on a specific register.
A proper risk assessment/management should anyhow follow the general scheme proposed
in Figure 2 (adapted from EN-ISO 14971). 17
Procedure (Checking in Vitro Expansion and/or Engineering
of the Cell Components)
Cell components are potentially subjected to several biological risks during the expansion
and/or storage phases; to ensure the manufacturing quality, intermediate and final products
should be tested for the following:
Cell Identity
The identity and composition of the cell population through the different manufacturing
phases must be determined. A set of genotypical, phenotypical and functional markers must be
available to follow and unequivocally identify the proper cell type. 18