Impaired migration of autologous induced neural stem cells from patients with schizophrenia and implications for genetic risk for psychosis
Introduction
Neurodevelopment is an astounding endeavor through which, via neuronal migration, a lump of embryonal cells unfold into an organ consisting of >1011 cells, including neurons and glia (Lois and Alvarez-Buylla, 1994; von Bartheld et al., 2016). Schizophrenia (SZ) has long been considered a disorder of neurodevelopment since researches in the 1980s proposed the neurodevelopmental hypothesis of SZ. The hypothesis states that early developmental brain abnormalities, especially those in the prefrontal cortex, interact with the normal maturation process to culminate in the onset of psychosis (Murray and Lewis, 1987; Weinberger, 1987). Indeed, several cytoarchitectural studies from postmortem brains of patients with this debilitating disorder point to defective neuronal migration in early developmental stages (Weinberger, 1995). However, as the human brain during its development is usually inaccessible to investigations requiring biopsy or invasive procedures, explicit examination of neurodevelopmental deficits that could deepen our understanding of the disorder was infeasible.
Recent advances in stem cell technologies have enabled the derivation of neuron- or neural stem cell-like cells from various tissues of patients without the biopsy of their brains (Brennand and Gage, 2011; Buchsbaum and Cappello, 2019). Since the pioneering work by Brennand and Gage et al. (Brennand et al., 2011), who presented the first direct evidence of neurodevelopmental abnormalities in SZ using induced pluripotent stem cell (iPSC) techniques, subsequent studies have demonstrated that induced neural stem cells (iNSCs) derived from SZ patients, which resemble their fetal brain tissue, indeed present deficits in neurodevelopmental capability including neuronal migration (Brennand et al., 2015; Casas et al., 2018). These investigations were a pivotal milestone in SZ research in that, for the first time, abnormal phenotypes of living human cells derived from patients were studied and modelled (Tran et al., 2013). However, the process of reprogrammed iPSC generation incorporates exogeneous genetic expression of “Yamanaka factors” (OCT4, KLF4, SOX2, C-MYC), whose overexpression can induce pluripotency in somatic cells (Takahashi et al., 2007). Notably, despite these historic achievements in SZ research, it has been argued that introduction of “Yamanaka factors” into iPSCs accompanies some mutations, whose extent and mechanisms are still elusive (Araki et al., 2020). These mutations may lead to considerable heterogeneity within iPSC clones and might also impede the interpretation of resultant phenotypes (Bhutani et al., 2016; Rouhani et al., 2016), necessitating further relevant studies. Our group has previously developed a small molecule (SM)-based lineage switch method that induces iNSCs from human adipose-derived mesenchymal stem cells (hADSCs) by a cellular reprogramming method without exogeneous genetic manipulations (Park et al., 2017), enabling further exploration of the impact of the disease itself and genetic liability on neural cells. The iNSCs derived by the SM-based lineage switch showed morphological, functional, and molecular features of human neural stem cells (NSCs). Also, the lineage switch of iNSCs toward a neural fate was demonstrated with microarray analyses showing gene expression signatures of human NSCs (Park et al., 2017).
On the other hand, researchers have long highlighted an undoubtable fact about SZ—the devastating disorder runs in families and has a genetic basis (Sullivan et al., 2012). Consequently, numerous researchers have assembled and investigated cohorts of the offspring of patients with SZ, i.e., individuals at “genetic high risk” (GHR) for psychosis, to study the pathophysiology of SZ in the developing brains (Cannon et al., 1994; Erlenmeyer-Kimling et al., 1997; Grunebaum et al., 1974; Hodges et al., 1999; Ingraham et al., 1995; Mirsky et al., 1995; Tienari et al., 2003). These epidemiological studies have focused on identifying risk factors and on providing a basis for prevention and early intervention (Cornblatt, 2002). However, despite the invaluable findings from these extensive studies, they revealed little about the mode of transmission of SZ, and research on more reliable and valid predictors of psychosis is still lacking. In addition, the mechanism by which those at high risk develop florid psychosis is still not truly understood (Hodges et al., 1999). Since neurodevelopmental processes such as neuronal migration are regulated by genetic factors, disrupted neurodevelopment and SZ liability could be mediated by a common genetic liability (Jaaro-Peled et al., 2009). To our knowledge, despite the potential relevance of stem cell technology to this question, there are few published data on the phenotypes of iNSCs derived from GHR individuals.
Here, our aims were to 1) investigate the cellular phenotypes, including the migration capability, of iNSCs derived from patients with SZ using a SM-based lineage switch technique without genetic modifications and 2) derive iNSCs from GHR individuals with high genetic liability using a SM-based lineage switch method and investigate their cellular phenotypes.
Section snippets
Participants
Three patients diagnosed with SZ, 3 GHR individuals, and 3 matched healthy controls (HCs) participated in this study. The participants were recruited from the Seoul Youth Clinic, a center providing early intervention, prevention, and management services for young people at risk for psychosis (Lee et al., 2020), and the outpatient clinic of Seoul National University Hospital (SNUH), Korea. Data were collected from November 15, 2013, to February 4, 2016. Potential participants were enrolled after
Demographic and clinical characteristics
Demographic characteristics were not different among the groups (age, χ2 = 5.637, P = .060; education years, χ2 = 2.111, P = .348). All but one GHR participant (GHR-1) were males, and all participants were of Korean ancestry. The level of functioning measured with the Global Assessment of Functioning (GAF) was significantly lower in individuals with SZ (χ2 = 6.161, P = .046). All patients with SZ were taking atypical antipsychotics with mean (±SD) chlorpromazine (CPZ) equivalent dose of 191.67
Discussion
The main finding of this study is the novel demonstration of impaired migration capability of SZ-iNSCs induced with the SM-based lineage switch compared to that of HC-iNSCs. Reduced expression of the neural precursor cell marker Sox2 in SZ-iNSCs was also observed. Furthermore, examinations of GHR-iNSCs revealed mostly normal phenotypes, except for a GHR individual who later converted into overt psychosis whose iNSCs showed migratory defects similar to those of SZ-iNSCs.
This study reports
Conclusion
In conclusion, we report a novel finding of impaired migration in genetically unmodified SZ-iNSCs and in some GHR-iNSCs, which is the first explicit demonstration of the postulation that neurodevelopmental abnormalities might be present in SZ (Insel, 2010; Lawrie et al., 1999; Murray and Lewis, 1987; Weinberger, 1987). Additionally, we found alterations in gene expression in SZ-iNSCs, which hint at mechanisms such as dysfunctional neurogenesis by which genetic liability leads to anomalous
Role of funding sources
The funders had no role in the study design, data collection, data analysis, or writing of the manuscript.
CRediT authorship contribution statement
Concept and design: TY Lee, Chang, and Kwon; Acquisition, analysis, or interpretation of data: Junhee Lee, Song, J Kang, Juhee Lee, EK Choe, Chon, SW Kim, and Chun; Drafting of the manuscript: Junhee Lee and Song; Critical revision of the manuscript: All authors; Statistical analysis: Junhee Lee, Song, and TY Lee; Obtained funding: Kwon and Chang; Administrative or technical support: J Kang, Juhee Lee, TY Lee, M Kim, and SW Kim; Supervision: Kwon and Chang.
Declaration of competing interest
The authors declare no conflict of interests.
Acknowledgements
This work was supported by the National Research Foundation (NRF) of Korea [Grant no. 2017M3C7A1029610 to JSK and 2019R1A2C1087192 to MSC], and by the Ministry of Health & Welfare, Republic of Korea [Grant no. HI20C0253 and HU21C0113 to MSC]. The statistical analyses of this study were carried out with supports by Medical Research Collaborating Center (MRCC) of SNUH.
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