Cell suspension culture disadvantages

An important disadvantage which is frequently mentioned in the literature is the low degree of cell differentiation in suspension cultures of plant cells. As product formation in plants largely occurs in differentiated tissue, it seems reasonable that the undifferentiated state might not favor the formation of secondary products. In some cases, for example, the production of ajmalicine in cultures of Catharanthus roseus, it is indeed shown that the product, originally formed in the roots of the plant, is better produced in hairy root cultures than in cell suspension cultures. 

Scale-up of cell cultures makes use of suspension cultures (erythropoietic cells or microcarriers) or, less often use of capillary beds (hollow fibre systems or glass bead columns), but these suffer from the same disadvantages seen with smaller scale cultures ( 3.4.4). In particular, nutrients are depleted as the medium flows through long columns or beds and high rates of flow coupled with recirculation are often employed. Nevertheless, Organon have used a hollow fibre dialysis system for production of monoclonal antibodies (Schonherr et al., 1985). Invitron s hollow fibre system has been used to produce cell conditioned media and the Cell-Pharm System (Jencons Ltd. Appendix 3) will produce up to 20 g cell secreted product per month. 

Once isolated, hepatocytes can be used either in suspension cultures or as monolayer cultures, where they are allowed to attach to culture dishes. In the case of suspension cultures, a very limited amount of equipment is needed, but a disadvantage is that the cells can only be used for a few hours. Monolayer cultures stay viable for several days or weeks, but their use requires the presence of tissue culture facilities, in order to work under sterile conditions. 

ESNPCs are used by many labs for research and are most commonly derived using retinoic acid (RA) addition to embryoid body (EB) suspension cultures in an 8-day protocol (4-/4-t) developed by Bain et al. (1995). These cells can then be dissociated or left as EBs (Willerth et al. 2006) and used in in vitro studies or transplanted (either as whole EBs or single cells, after dissociation) (Johnson et al. 2010b, McDonald et al. 1999). They are generally amenable to dissociation when used for two-dimensional (2D) cell culture, but have low viabihty in vitro or in vivo in three-dimensional (3D) scaffolds/ culture systems. Another disadvantage is that there are residual undifferentiated ESCs (10-30%) at the end of this protocol that need to be purified prior to transplantation to prevent tumor formation (Johnson et al. 2010a). 

More recently, there has been much effort to replace animal tests with in vitro test models, such as isolated tissues and cell cultures (Hutak and Jacaruso 1996). These have some advantages in that they are less costly than in vivo tests, use relatively simple methodology and can be used to identify primary changes at the cellular level. The disadvantages are that they do not mimic the eye response, they cannot be used to evaluate insoluble materials (e.g., suspensions), and the various methods differ widely in their ability to predict irritancy potential. It is conceivable that in vitro methods could be used for primary screening tests, while more standard in vivo methods are used to verify the result. 

---