87Another study on drug screening used iPSCs to assess and control the activity of
new drugs to treat some diseases, such as neurological diseases (Egawa et al. 2012 ;
Xu and Zhong 2013 ) and liver disease (Choi et al. 2013 ). Many studies have sug-
gested that patient-derived iPSCs may provide a useful tool for screening drug
candidates.
Using iPSCs to prognosticate effi cacy and toxicity could help to reduce the cost
and duration of drug development processes. iPSCs may also help overcome many
of the challenges and shortcomings associated with disease modeling and drug
screening. The promise of iPSCs for regenerative medicine and drug screening is
likely to be expanded in the near future.
4.3.2 Regenerative Medicine
The discovery of iPSCs has introduced a novel approach in regenerative medicine.
Reprogramming of somatic cells has marvelous potential for clinical uses (Cherry
and Daley 2013 ). Although adult stem cells have high potential for degenerative
disease, these obstacles could be overcome by limitation of cells and restriction of
differentiation capacity. Physiological profi le matches in allogeneic stem cell trans-
plantation are also a risk and restriction of adult stem cells. Scientists believe that
iPSCs could be used in degenerative disease treatment by generating autologous
cells (Cherry and Daley 2013 ), correcting gene mutation, differentiating into spe-
cifi c tissues, and transferring these to the patient (Cherry and Daley 2013 ). iPSCs
represent an unlimited source of cells that can be used to form functional organ
structures. In fact, iPSCs have potential for cell therapies because of their capacity
for differentiation into a variety of cell types including neural cells, cardiomyocytes,
islet cells, and hepatocytes (Hirschi et al. 2014 ). However, guidelines and safety
issues of these cells should be considered to reduce side effects and increase thera-
peutic effects.
A number of publications on iPSC generation protocols are available, and many
studies have focused on how to develop and enhance large-scale production of
specifi c cell types from iPSCs or directed differentiation into specifi c lineages
(Hirschi et al. 2014 ). Many factors have been discovered that contribute to differen-
tiation of iPSCs into specifi c cell types, such as chemicals, growth factors, signaling
inhibitors, cytokines, and biophysical stimulation. Furthermore, a number of culture
methods have been explored to promote cell differentiation such as coculture with
supporting cells and 3D cultures.
In addition, many approaches have been examined to direct reprogramming to
reduce the risks of iPSCs. It is believed that direct reprogramming from somatic
cells into a specifi c cell type would eradicate the generation of pluripotent cells
(Hirschi et al. 2014 ).
4 New Trends in Clinical Applications of Induced Pluripotent Stem Cells