Stem Cell & Regenerative Medicine

Biography

Biography: Kaixuan Zhao

Abstract

T-type Ca²⁺ channels operate in embryonic stem cells, but conduct relatively small Ca²⁺ currents in mature human β cells. In certain pathological contexts, e.g., when T-type Ca²⁺ channels undergo elevated expression, they mediate exaggerated Ca²⁺ influx to dissipate β cell maturity. This prompted us to hypothesize that altered T-type Ca²⁺ channel activity in human iPSC-derived islet (hiPSC-islet) cells affect maturation. To test our hypothesis, we transplanted hiPSC-isles into the anterior chamber of the eye (ACE) of immunodeficient mice, intravitreally infused T-type Ca²⁺ channel blocker NNC55-0396 and performed in vivo and ex vivo measurements. In vivo stereomicroscopy showed that transplanted hiPSC-islets underwent initial adhesion to, gradual integration with and eventual engraftment as well as survival on the iris. In vivo confocal microscopy revealed that intracameral hiPSC-islets were satisfactorily vascularized and displayed intense light scattering signals, reflecting the abundance of zinc-insulin crystals inside insulin secretory granules, within two months post-transplantation. Furthermore, intravitreally-infused NNC55-0396 did not influence the macromorphology, vascularization and light scattering signals. Interestingly, ex vivo [Ca²⁺]_i measurements disclosed that intravitreally-infused NNC55-0396 significantly decreased basal [Ca²⁺]_i levels and increased glucose-stimulated [Ca²⁺]_i responses in intact hiPSC-isles. In conclusion, the present study verifies that the immunodeficient mouse ACE can serve as a unique site for pharmacological manipulation of in vivo maturation of hiPSC-islets. These cells can not only be micro-imaged intravitally, noninvasively and longitudinally, but also retrieved without suffering physical and chemical disturbance for more precise ex vivo studies, as exemplified here by [Ca²⁺]_i measurements. Importantly, our data demonstrate that inhibition of T-Type Ca²⁺ channels facilitates glucose-dependent Ca²⁺ signaling in hiPSC-islets. These findings are important and support the notion that altered T-type Ca²⁺ channel activity may serve as a key signal in hiPSC-islet cell maturation.