The overarching focus of the Snoeck laboratory is stem cell biology, and consists of two major vignettes: hematopoietic stem cells (HSCs), the historical focus of the lab, and a more recently developed project on lung development from human pluripotent stem cells (hPSCs).

The respiratory system arises from buds on the ventral anterior foregut endoderm (AFE) that undergo a stereotyped branching process followed by specialization of the airway epithelium in the stalks while, distally, alveoli develop where gas exchange will take place. We have published a strategy to achieve the generation of developmental lung progenitors from hPSCs. These were capable of further differentiation into airway and, predominantly, distal lung cells in 2D cultures. Recapitulation of lung development from human pluripotent stem cells (hPSCs) in three dimensions (3D) would allow innovative strategies for disease modeling, drug discovery and regenerative medicine. While organoids containing a variety of lung and airway epithelial cells have been generated from hPSCs. a 3D system that emulates lung development and allows disease modeling has not yet been realized. We developed a culture system where lung bud organoids (LBOs) are generated from hPSCs that develop into branching airway and alveolar structures after xenotransplantation. In 3D culture LBOs undergo branching morphogenesis and distal lung development. 

We are currently using these models to examine mechanisms underlying alveolar epithelial cells specification and establishment of alveolar architecture. Further studies also focus on mechanisms of proximodistal specification, with a focus on the generation of basal cells, and as well cell fate choices during terminal alveolar development. The generation of proximal airway stem cells (basal cells) would a major advance in the modeling and treatment of cystic fibrosis.

An important focus is modeling of idiopathic pulmonary fibrosis (IPF). IPF is an intractable lung disease with a median survival of 3-4 years. 30-40,000 Americans die from this disease each year. As currently no curative treatments are available except for lung transplantation, innovative approaches are urgently needed. Developing such approaches requires insight into pathogenesis. The nature of some predisposing mutations strongly suggests a key role for dysfunction of surfactant-producing type II alveolar epithelial (ATII) cells. Given the current state-of-the-art, the best, and perhaps the only, opportunity to gain insight into the pathogenesis of IPF is attempting to model this disease using induced pluripotent state (iPS) or genome edited ES cells. Our LBO model allowed recapitulation of fibrosis in hPSCs with engineered mutations in HPS1, which predispose with high penetrance to idiopathic pulmonary fibrosis (IPF). 

Hematopoietic stem cells (HSCs) in the bone marrow (BM) sustain the production of all blood cell lineages through differentiation into progenitors with progressively more restricted lineage potential. Despite decades of research, a coherent understanding of the mechanisms involved in the regulation of their quiescence, self-renewal and differentiation is still lacking however. As HSCs rely on glycolysis for ATP production, little attention has been given to the study of mitochondrial function in HSCs. We discovered that mitochondrial dynamics in HSCs are regulated by an essential regulator of HSC function discovered by us, Prdm16, which in turn induces Mitofusin 2 (Mfn2). Deletion of Mfn2 leads to mitochondrial fragmentation and impaired maintenance of subset of HSCs with extensive lymphoid potential. The underlying mechanism is based on regulation of intracellular calcium and NFAT. Mfn2-deletion furthermore induced HSC cycling through activation of interferon-induced genes, indicating that mitochondria are an important platform for the regulation of HSC maintenance and quiescence. Further studies will focus on the predominantly ATP-independent roles of mitochondria in HSC function, focusing on mitochondrial dynamics, mitochondria-ER interactions, autophagy and mitophagy, and calcium regulation. A major focus is the role of mitochondrial maintenance mechanism in the aging of stem cells.