Sub-Retinal Delivery of Human Embryonic Stem Cell Derived Photoreceptor Progenitors in rd10 Mice

Regeneration of photoreceptor cells using human pluripotent stem cells is a promising therapy for the treatment of both hereditary and aging retinal diseases at advanced stages. We have shown human recombinant retina-specific laminin isoform matrix is able to support the differentiation of human embryonic stem cells (hESCs) to photoreceptor progenitors. In addition, sub-retinal injection of these cells has also shown partial restoration in the rd10 rodent and rabbit models. Sub-retinal injection is known to be an established method that has been used to deliver pharmaceutical compounds to the photoreceptor cells and retinal pigmented epithelial (RPE) layer of the eye due to its proximity to the target space. It has also been used to deliver adeno-associated viral vectors into the sub-retinal space to treat retinal diseases. The sub-retinal delivery of pharmaceutical compounds and cells in the murine model is challenging due to the constraint in the size of the murine eyeball. This protocol describes the detailed procedure for the preparation of hESC-derived photoreceptor progenitor cells for injection and the sub-retinal delivery technique of these cells in genetic retinitis pigmentosa mutant, rd10 mice. This approach allows cell therapy to the targeted area, in particular the outer nuclear layer of the retina, where diseases leading to photoreceptor degeneration occur.

Microbial exposure during early human development primes fetal immune cells

The human fetal immune system begins to develop early during gestation; however, factors responsible for fetal immune-priming remain elusive. We explored potential exposure to microbial agents in utero and their contribution toward activation of memory T cells in fetal tissues. We profiled microbes across fetal organs using 16S rRNA gene sequencing and detected low but consistent microbial signal in fetal gut, skin, placenta, and lungs in the 2^nd trimester of gestation. We identified several live bacterial strains including Staphylococcus and Lactobacillus in fetal tissues, which induced in vitro activation of memory T cells in fetal mesenteric lymph node, supporting the role of microbial exposure in fetal immune-priming. Finally, using SEM and RNA-ISH, we visualized discrete localization of bacteria-like structures and eubacterial-RNA within 14^th weeks fetal gut lumen. These findings indicate selective presence of live microbes in fetal organs during the 2^nd trimester of gestation and have broader implications toward the establishment of immune competency and priming before birth.

Single-Cell RNA-seq Reveals Angiotensin-Converting Enzyme 2 and Transmembrane Serine Protease 2 Expression in TROP2+ Liver Progenitor Cells: Implications in Coronavirus Disease 2019-Associated Liver Dysfunction

The recent coronavirus disease 2019 (COVID-19) pandemic is caused by severe acute respiratory syndrome coronavirus 2. COVID-19 was first reported in China (December 2019) and is now prevalent across the globe. Entry of severe acute respiratory syndrome coronavirus 2 into mammalian cells requires the binding of viral Spike (S) proteins to the angiotensin-converting enzyme 2 receptor. Once entered, the S protein is primed by a specialized serine protease, transmembrane serine protease 2 in the host cell. Importantly, besides the respiratory symptoms that are consistent with other common respiratory virus infections when patients become viremic, a significant number of COVID-19 patients also develop liver comorbidities. We explored whether a specific target cell-type in the mammalian liver could be implicated in disease pathophysiology other than the general deleterious response to cytokine storms. Here, we used single-cell RNA-seq to survey the human liver and identified potentially implicated liver cell-type for viral ingress. We analyzed ~300,000 single cells across five different (i.e., human fetal, healthy, cirrhotic, tumor, and adjacent normal) liver tissue types. This study reports on the co-expression of angiotensin-converting enzyme 2 and transmembrane serine protease 2 in a TROP2+ liver progenitor population. Importantly, we detected enrichment of this cell population in the cirrhotic liver when compared with tumor tissue. These results indicated that in COVID-19-associated liver dysfunction and cell death, a viral infection of TROP2+ progenitors in the liver might significantly impair liver regeneration in patients with liver cirrhosis.