Research

Generation of human cell types

Human cell

We are using human pluripotent stem cells (human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs)) to differentiate cell types that are affected in diseases of the peripheral nervous system (PNS). Because primary patient PNS cells in large numbers are nearly impossible to access for research this technology enables the study of disease mechanisms and provides a platform for drug screening.

We have developed in vitro differentiation protocols to derive neural crest cells (Zeltner et al, 2014, JoVE), peripheral sensory neurons (Zeltner et al., patented – proprioceptors) and autonomic neurons (Zeltner et al, 2016, Nature Medicine). We are expanding this work to generate the sensory neuron subtypes, nociceptors and mechanoceptors, sympatho-adrenal progenitors, adreno-genital progenitors, sympathetic neurons (Saito-Diaz et al., 2019, Wu et al., 2020 JOVE), adrenal gland medulla and adrenal gland cortex and prefrontal cortical neurons (Cederquist et al., 2020). We are interested in understading how these cells are affected in inherited and acquired disorders that specifically affect these cell types.

Furthermore, we are working on generating adrenal gland organoids, i.e. 3D structures representing the human organ. This will allow in depth study of adrenal gland development as well as modeling diseases affecting adrenal gland tissues.

Disease modeling, disease mechanism studies and drug discovery

neurons

hPSC-based disease modeling is a powerful tool of modern medicine, that allows the in depth study of cellular, molecular and biochemical mechanism of human disease. In essence, this technology is based on the generation of iPSCs from patients and healthy control subjects, their differentiation into cell types that are specifically affected in the disease and the phenotypic and functional comparison between the groups. In theory, this technology may allow personalized medicine, where treatments could be tailored to individual patients (or patient groups).

Familial Dysautonomia (FD) is a debilitating developmental and degenerative disorder that primarily affects derivatives of the neural crest (NC), such as the peripheral nervous system (PNS). FD patients present with mild or severe disease, despite carrying the identical, homozygous point mutation in the ELP1 gene. The reason for this remains unknown.
Using hPSCs, we were able to identify in vitro phenotypes at various stages of development capturing severe and mild FD. Only cells from severe but not mild FD patients showed neurodevelopmental defects. Interestingly however, both severe and mild FD cells display neurodegenerative defects. Thus, degeneration is the primary culprit in mild FD. We further were able to elucidate the molecular mechanistic reason why severe and mild FD symptoms differ. Severe, but not mild patients harbor an additional modifier mutation in lamininβ4 (LAMB4) that may specifically affect FD-sensitive cell types, such as NC and sensory neurons (Zeltner et al., 2016, Nature Medicine).

Current work aims at investigating the mechanistic consequences of the LAMB4 mutation and how it leads to severe FD. We discovered that, possibly due to the LAMB4 mutation, the extracellular matrix (ECM) is defective, which leads to both developmental and degenerative defects in FD.
Our work further has elucidated that sympathetic neurons (symNs) in FD are electrically hyperactive. We are investigating both the cellular and molecular consequences underlying this phenomenon.

Additionally, we are investigating a small molecule compound, that was discovered in a high-throughput drug screening approach. This compound was able to rescue one of the severe FD phenotypes. Current work aims at understanding the mode of action of this compound with the goal to develop it into a novel treatment option for FD and possibly other peripheral neuropathies.

Cellular effects of stress

stress diagram

Stress affects a growing number of people worldwide and is involved in causation of multiple disorders. It is well established that pathological stress changes the biology of the brain on the cellular and molecular level. We focus on investigating how pathological stress changes the biology of the PNS, specifically sympathetic neurons and cells of the adrenal gland (medulla and cortex). These are the three cell types in the body that transmit stress signals from the brain to the internal organs enabling us to physically react. Furthermore, these signals are working improperly in pathological stress disorders. The greater goal of such studies is to understand the effects of stress on the PNS in detail in order to identify novel biomarkers that may lead to novel drug candidates for the treatment of such disorders.

We address this research in two approaches: 1. By generating iPSCs derived from patients who suffer from PTSD (in collaboration with Grady Trauma Project at Emory). We will differentiate these iPSCs into neurons and assess disease related phenotypes. 2. We are generating 3D cellular structures that mimic the adrenal glands (called organoids). Such organoids will be employed to assess adrenal gland disorders as well as the effects of stress on the adrenal glands.