Signaling Molecules Regulating Pancreatic Endocrine Development from Pluripotent Stem Cell Differentiation

Abstract

Diabetes is one of the leading causes of death globally. Currently, the donor pancreas is the only source of human islets, placing extreme constraints on supply. Hence, it is imperative to develop renewable islets for diabetes research and treatment. To date, extensive efforts have been made to derive insulin-secreting cells from human pluripotent stem cells with substantial success. However, the in vitro generation of functional islet organoids remains a challenge due in part to our poor understanding of the signaling molecules indispensable for controlling differentiation pathways towards the self-assembly of functional islets from stem cells. Since this process relies on a variety of signaling molecules to guide the differentiation pathways, as well as the culture microenvironments that mimic in vivo physiological conditions, this review highlights extracellular matrix proteins, growth factors, signaling molecules, and microenvironments facilitating the generation of biologically functional pancreatic endocrine cells from human pluripotent stem cells. Signaling pathways involved in stepwise differentiation that guide the progression of stem cells into the endocrine lineage are also discussed. The development of protocols enabling the generation of islet organoids with hormone release capacities equivalent to native adult islets for clinical applications, disease modeling, and diabetes research are anticipated.

Characterization of stem-cell-derived islets during differentiation and after implantation

“…Generation of b cells from hPSCs is based on a complex differentiation protocol that mimics the stages of pancreatic and b cell development during embryogenesis through addition of growth factors and different small molecules (Huang et al, 2020). Despite targeted activation of signaling pathways toward b cells, non-endocrine cells cannot be completely avoided throughout the differentiation process, but several strategies are being studied to enrich the endocrine populations and remove pluripotent cells and proliferating progenitors from the SC-islets.…”

Making human pancreatic islet organoids: Progresses on the cell origins, biomaterials and three-dimensional technologies

“…Few reports have attempted to design a proportion of α, β, δ and other accessory cells in making islet organoid (Table 1 ), which led to the different structures between islet organoid and native islet and may also lead to the immature status of β cells. There have been many robust differentiation approaches to generate β cells 151 , 152 , and these β cells somewhat still resemble the immature stage observed in the fetal pancreas 153 . Most β cells differentiation approaches are based on the combination of growth factors and small chemical molecules targeting specific signal pathway, such as WNT 154 - 156 , but the internal secretion regulatory and physical interactions surrounding the β cells were ignored 15 , 157 , 158 .…”

Cryopreservation of engineered tissues and organoids

“…Retinoic acid, a fundamental signaling molecule in vertebrate endoderm development, is employed to direct differentiation into pancreatic progenitors [26,27,29]. SANT1, an inhibitor of the Sonic hedgehog pathway, enhances pancreatic specification [26,27,30], while LDN193189, an inhibitor of the bone morphogenetic pathway, facilitates conversion into pancreatic endocrine precursors [26,27,31]. Alk5i, an inhibitor of the transforming growth factor-β type I receptor kinase (ALK5), and the small thyroid hormone T3 (L-3,3´,5-triiodothyronine) are employed in the late stage of differentiation to generate insulin-positive β-like cells (Fig.…”