Endocrine Abstracts

GnRH neurons are vital for reproductive competence. These neurons originate mainly in the nasal epithelium and migrate to the preoptic region of the hypothalamus during foetal development. Defective migration may result in Hypogonadotropic Hypogonadism (HH), a condition in which puberty is never or only partially achieved.

Little is known about the molecular ontogeny and regulation of GnRH neurons. Their anatomical localisation and small numbers (about 1000) makes experimental studies extremely difficult. Immortalised GnRH-releasing cell lines have provided functional insights but they carry several limitations. Human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs) have been differentiated into many neuronal types but not into mature GnRH neurons.

We have created GnRH-expressing neurons from hESCs and iPSCs. iPSCs were generated by reprogramming dermal fibroblasts from Kallmann’s Syndrome patients and unaffected family members. iPSCs lines were karyotypically normal and displayed pluripotency features, including self-renewal, expression of pluripotency markers, and ability to differentiate to cells of all three germ layers. GnRH-expressing neurons were produced by generating Neural Progenitor Cells (NPCs) through prolonged BMP inhibition over several passages. NPCs express early neuronal markers such as PAX6 and Nestin and can be passaged and expanded. Terminal differentiation was achieved by incubating the cells in basal neuronal media supplemented with FGF8. After 21 days neurons express mature neuronal markers TUJ1 and MAP2. GnRH expression can be detected by immunocytochemistry and RT-PCR. Mature neurons also express CXCR4 but very little to no KISSR1.

We plan to use this system to investigate basal and stimulated GnRH release. We will also investigate developmental changes over time by extending the culture period. Our model of GnRH neurons derived from hESCs/iPSCs could provide a reliable system for studying molecular mechanisms underlying developmental changes and conditions such as HH.