**4. Application of iPSC-based tissue regeneration**

hiPSC-derived cells or organoids are becoming promising resources for disease modeling and therapeutical applications. In general, somatic cells from patients can be reprogrammed to hiPSCs. In turn, patient-specific hiPSCs can be converted into target organs using established protocols. These *in vitro* derived organs can be used for multiple purposes, including patientspecific disease modeling, drug testing, therapy screening, and transplantation.

screening is no longer a process that is limited by the responses of targeted organ, it can also

hiPSC-Based Tissue Organoid Regeneration http://dx.doi.org/10.5772/intechopen.76997 111

The nature of the disease and desired genetic modification, efficiency and accuracy of gene repair methodology, as well as cell state will determine the success of gene therapy [102]. In theory, monogenic diseases dictated by a dysfunctional copy of the causative gene would be reversed by introducing a wild-type copy of the gene into cells [103, 104]. Over 80% of rare diseases are considered to have a genetic origin [105], which means the precise gene editing technologies can be practically used to correct these genetic factors. The application of genome editing technologies in therapeutic trials have been reported in many diseases, such as retinal diseases [106], lysosomal storage diseases [107], arthritis [108], and neurological disorders [109, 110]. In contrast, polygenic diseases that require simultaneous multiple altera-

Gang et al. presented a highly efficient and reproducible protocol to edit the genome of hiP-SCs through the combined use of the CRISPR/Cas9 RNA-guided nuclease and piggyBac (bacterial artificial chromosome) transposase [112]. Their method can result in efficient, targeted genome editing and concurrent "scarless" transgene excision. Satoru et al. reported using gene editing with engineered site-specific endonuclease technology to treat dominant-negative disorders by targeting only the mutant allele while leaving the normal allele intact [113]. Using precise gene editing technology to correct gene mutations from hiPSCs generated from patients combined with hiPSC differentiation into target cells/organs for transplantation pro-

tions of the genome are more challenging to treat with gene therapy [111].

vides an immense promise for the future of gene therapy (**Figure 10**).

**Figure 10.** The summary of gene therapy applying precise genome editing technology in hiPSCs.

provide an evaluation of systemic responses.

*4.2.2. Gene therapy*

#### **4.1. Personalized disease modeling**

The biggest advantage of the hiPSC technology lies in its patient-specific feature. hiPSC-derived 3D organoid models have recently emerged as a powerful tool to recapitulate and investigate the physiologically-relevant process of disease onset and progression *in vitro*. This model system leverages the self-renewal and multi-lineage differentiation capability of multipotent stem cells and their intrinsic self-organization regenerative ability to form 3D tissue architecture. Importantly, hiPSCs can be derived from patients with known hereditary genetic mutations that are associated with a higher risk of a particular disease. This provides a valuable approach to determine whether additional genetic alterations are needed to interact with the known mutations, thereby contributing to disease susceptibility, initiation, and progression [92].

Several hiPSC-derived, inherited human disease models have been used to reproduce cancers associated with those high-risk patients [93, 94]. A hiPSC-derived osteosarcoma model for Li-Fraumeni syndrome has yielded promising results in displaying disease pathogenesis and carcinogenesis events commonly found in relevant human cells [95]. Cystic Fibrosis (CF) is an inherit disease of secretory glands. Among all the organs, pancreas is the earliest and most severely affected organs impacted by CF. hiPSC-derived pancreatic epithelial cells can be used to study personalized CF development [96]. Kyle et al. [81] used hiPSC-derived gastric organoids to model the pathophysiological response of the human stomach to *H. pylori* infection. In addition, Miguel et al. reported using hiPSC-derived colonic organoids to model family APC mutation-associated colon cancer initiation [83]. More and more hiPSCs-based disease models will be established.

#### **4.2. Therapeutic applications**

#### *4.2.1. Drug screening*

Organoids differentiated from patient-derived hiPSCs can be used to build a screening platform to develop and validate therapeutic approaches. hiPSC-derived organoids have a line of features that make them suitable models. Using a defined protocol, hiPSC-derived organoids become an unlimited resource for a specific patient. The *in vitro* direction of organ differentiation allows the rapid and robust generation of organoids with identical features. Most importantly, the organoids are 3D based mini-tissues that consist of multiple cell types, and that recapitulate the tissue structures *in vivo*. Thus, the drug screening results are more applicable *in vivo*. As an example, hiPSC-based drug screening for Huntington's disease has been established [97] developed. The applications of hiPSCs that have been reprogramed from patients of heritable, genetic diseases has been summarized by Wonhee Suh in a review paper [98].

Biomimetic tissues on a chip have been developed for drug discovery [99]. Organ-on-a-chip is based on microfluidic technology and has been proposed as a novel cell-based assay tool in pre-clinical studies. Furthermore, the concept of body-on-a-chip, which is stands for multiple organs connected through microfluid devices, can mimic multiple interactions between organs [100]. Applying hiPSC research to the concept of organ-on-a-chip has provided a promising future for the development of the patient-specific body-on-a-chip [101]. Drug screening is no longer a process that is limited by the responses of targeted organ, it can also provide an evaluation of systemic responses.

#### *4.2.2. Gene therapy*

protocols. These *in vitro* derived organs can be used for multiple purposes, including patient-

The biggest advantage of the hiPSC technology lies in its patient-specific feature. hiPSC-derived 3D organoid models have recently emerged as a powerful tool to recapitulate and investigate the physiologically-relevant process of disease onset and progression *in vitro*. This model system leverages the self-renewal and multi-lineage differentiation capability of multipotent stem cells and their intrinsic self-organization regenerative ability to form 3D tissue architecture. Importantly, hiPSCs can be derived from patients with known hereditary genetic mutations that are associated with a higher risk of a particular disease. This provides a valuable approach to determine whether additional genetic alterations are needed to interact with the known mutations, thereby contribut-

Several hiPSC-derived, inherited human disease models have been used to reproduce cancers associated with those high-risk patients [93, 94]. A hiPSC-derived osteosarcoma model for Li-Fraumeni syndrome has yielded promising results in displaying disease pathogenesis and carcinogenesis events commonly found in relevant human cells [95]. Cystic Fibrosis (CF) is an inherit disease of secretory glands. Among all the organs, pancreas is the earliest and most severely affected organs impacted by CF. hiPSC-derived pancreatic epithelial cells can be used to study personalized CF development [96]. Kyle et al. [81] used hiPSC-derived gastric organoids to model the pathophysiological response of the human stomach to *H. pylori* infection. In addition, Miguel et al. reported using hiPSC-derived colonic organoids to model family APC mutation-associated colon cancer initiation [83]. More and more hiPSCs-based disease models

Organoids differentiated from patient-derived hiPSCs can be used to build a screening platform to develop and validate therapeutic approaches. hiPSC-derived organoids have a line of features that make them suitable models. Using a defined protocol, hiPSC-derived organoids become an unlimited resource for a specific patient. The *in vitro* direction of organ differentiation allows the rapid and robust generation of organoids with identical features. Most importantly, the organoids are 3D based mini-tissues that consist of multiple cell types, and that recapitulate the tissue structures *in vivo*. Thus, the drug screening results are more applicable *in vivo*. As an example, hiPSC-based drug screening for Huntington's disease has been established [97] developed. The applications of hiPSCs that have been reprogramed from patients of heritable, genetic diseases has been summarized by Wonhee Suh in a review paper [98].

Biomimetic tissues on a chip have been developed for drug discovery [99]. Organ-on-a-chip is based on microfluidic technology and has been proposed as a novel cell-based assay tool in pre-clinical studies. Furthermore, the concept of body-on-a-chip, which is stands for multiple organs connected through microfluid devices, can mimic multiple interactions between organs [100]. Applying hiPSC research to the concept of organ-on-a-chip has provided a promising future for the development of the patient-specific body-on-a-chip [101]. Drug

specific disease modeling, drug testing, therapy screening, and transplantation.

**4.1. Personalized disease modeling**

110 Tissue Regeneration

will be established.

*4.2.1. Drug screening*

**4.2. Therapeutic applications**

ing to disease susceptibility, initiation, and progression [92].

The nature of the disease and desired genetic modification, efficiency and accuracy of gene repair methodology, as well as cell state will determine the success of gene therapy [102]. In theory, monogenic diseases dictated by a dysfunctional copy of the causative gene would be reversed by introducing a wild-type copy of the gene into cells [103, 104]. Over 80% of rare diseases are considered to have a genetic origin [105], which means the precise gene editing technologies can be practically used to correct these genetic factors. The application of genome editing technologies in therapeutic trials have been reported in many diseases, such as retinal diseases [106], lysosomal storage diseases [107], arthritis [108], and neurological disorders [109, 110]. In contrast, polygenic diseases that require simultaneous multiple alterations of the genome are more challenging to treat with gene therapy [111].

Gang et al. presented a highly efficient and reproducible protocol to edit the genome of hiP-SCs through the combined use of the CRISPR/Cas9 RNA-guided nuclease and piggyBac (bacterial artificial chromosome) transposase [112]. Their method can result in efficient, targeted genome editing and concurrent "scarless" transgene excision. Satoru et al. reported using gene editing with engineered site-specific endonuclease technology to treat dominant-negative disorders by targeting only the mutant allele while leaving the normal allele intact [113]. Using precise gene editing technology to correct gene mutations from hiPSCs generated from patients combined with hiPSC differentiation into target cells/organs for transplantation provides an immense promise for the future of gene therapy (**Figure 10**).

**Figure 10.** The summary of gene therapy applying precise genome editing technology in hiPSCs.

#### *4.2.3. Transplantation*

Given that hiPSCs are pluripotent stem cells which can be propagated unlimitedly and protocols for their differentiation into different cells/organoids have been established, hiPSC-derived micro-tissues are a potentially innovative material source for transplantation. In addition, immune rejection will be minimized when essentially returning the hiPSC-derived tissue to the original patient. For mature cells that have no or limited regenerative ability, such as cardiomyocytes, neurons, and pancreatic cells, hiPSC-derived cell/organoids are especially valuable for tissue repair. There are a series of clinical studies evaluating hiPSC-cells/organoids for treatment of neural degeneration, diabetes, heart failure, and retinal cells [114]. Although research on the application of hiPSCs in therapy have shown encouraging progress, there are some concerns involving the safety of hiPSC-based cell transplantation. Tumor risk and acquired gene mutations are major concerns.

**Acknowledgements**

**Conflict of interest**

**Author details**

**References**

2001-2009

2014;**522**:2707-2728

Reports. 2016;**6**:312-320

2016;**67**:2161-2176

This work was supported by the National Institutes of Health (2R01CA151610), the Fashion Footwear Charitable Foundation of New York, Inc., the Margie and Robert E. Petersen

hiPSC-Based Tissue Organoid Regeneration http://dx.doi.org/10.5772/intechopen.76997 113

Ying Qu, Nur Yucer, Veronica J. Garcia, Armando E. Giuliano and Xiaojiang Cui\*

of progress. Nature Reviews. Drug Discovery. 2016;**16**(2):115-130

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Foundation, and the Linda and Jim Lippman Research Fund.

All the authors declare no conflict of interest.

\*Address all correspondence to: xiaojiang.cui@cshs.org

Cedars-Sinai Medical Center, Los Angeles, CA, United States
