Proliferative vitreoretinopathy is a vision-threatening response to penetrating ocular injury, for which there is no satisfactory treatment. In this disorder, retinal pigment epithelial cells, abandon their attachment to Bruch's membrane on the scleral side of the retina, transform into motile fibroblast-like cells, and migrate through the retinal wound to the vitreal surface of the retina, where they secrete membrane-forming proteins. Annexin A2 is a calcium-regulated protein that, in complex with S100A10, assembles plasmin-forming proteins at cell surfaces. Here, we show that, in proliferative vitreoretinopathy, recruitment of macrophages and directed migration of retinal pigment epithelial cells are annexin A2-dependent, and stimulated by macrophage inflammatory protein-1α/β. These factors induce translocation of annexin A2 to the cell surface, thus enabling retinal pigment epithelial cell migration following injury; our studies reveal further that treatment of mice with intraocular antibody to either annexin A2 or macrophage inflammatory protein dampens the development of proliferative vitreoretinopathy in mice.
© 2024. The Author(s).

In eukaryotic cells, DNA double strand breaks (DSB) are primarily repaired by canonical non-homologous end joining (c-NHEJ), homologous recombination (HR) and alternative NHEJ (alt-NHEJ). Zinc finger and SCAN domain containing 4 (ZSCAN4), sporadically expressed in 1-5% mouse embryonic stem cells (mESCs), is known to regulate genome stability by promoting HR.
Here we show that ZSCAN4 promotes DNA repair by acting with Poly (ADP-ribose) polymerase 1 (PARP1), which is a key member of the alt-NHEJ pathway. In the presence of PARP1, ZSCAN4-expressing mESCs are associated with lower extent of endogenous or chemical induced DSB comparing to ZSCAN4-negative ones. Reduced DSBs associated with ZSCAN4 are abolished by PARP1 inhibition, achieved either through small molecule inhibitor or gene knockout in mESCs. Furthermore, PARP1 binds directly to ZSCAN4, and the second ⍺-helix and the fourth zinc finger motif of ZSCAN4 are critical for this binding.
These data reveal that PARP1 and ZSCAN4 have a protein-protein interaction, and shed light on the molecular mechanisms by which ZSCAN4 reduces DSB in mESCs.
© 2023. Society of Chinese Bioscientists in America (SCBA).

Proliferative vitreoretinopathy (PVR) is a chronic, fibrosing, vision-threatening response to retinal injury that occurs in approximately half of individuals with penetrating ocular trauma, as well as in patients with rhegmatogenous retinal detachment or giant retinal tear. Current treatment for this common cause of post-traumatic blindness, remains unsatisfactory. Here, we show for the first time that the PVR reaction is profoundly blunted in a standard model system in annexin A2-deficient mice. We identify a new pathway whereby secretion of macrophage chemokines (macrophage inflammatory proteins, [MIP-1alpha and MIP-1beta]) signal the translocation of annexin A2 from the cytoplasm to the cell surface of retinal pigment epithelial cells (RPEs). Surface expression of A2 enables RPEs to activate surface proteases that allow them to delaminate, migrate to the vitreal surface of the retinal, and begin to secrete epiretinal membrane-forming proteins. RPE cell migration is markedly reduced in the injured retina in annexin A2-deficient mice, and antibody blockade of A2 appears to prevent PVR in wild type mice. We conclude that A2 may be a tractable, intraocular target for the prevention of PVR following eye injury.

Receptor-interacting protein kinase 1 (RIPK1) is a key mediator of regulated cell death (including apoptosis and necroptosis) and inflammation, both drivers of COPD pathogenesis. We aimed to define the contribution of RIPK1 kinase-dependent cell death and inflammation in the pathogenesis of COPD.
We assessed RIPK1 expression in single-cell RNA sequencing (RNA-seq) data from human and mouse lungs, and validated RIPK1 levels in lung tissue of COPD patients via immunohistochemistry. Next, we assessed the consequences of genetic and pharmacological inhibition of RIPK1 kinase activity in experimental COPD, using Ripk1 S25D/S25D kinase-deficient mice and the RIPK1 kinase inhibitor GSK'547.
RIPK1 expression increased in alveolar type 1 (AT1), AT2, ciliated and neuroendocrine cells in human COPD. RIPK1 protein levels were significantly increased in airway epithelium of COPD patients compared with never-smokers and smokers without airflow limitation. In mice, exposure to cigarette smoke (CS) increased Ripk1 expression similarly in AT2 cells, and further in alveolar macrophages and T-cells. Genetic and/or pharmacological inhibition of RIPK1 kinase activity significantly attenuated airway inflammation upon acute and subacute CS exposure, as well as airway remodelling, emphysema, and apoptotic and necroptotic cell death upon chronic CS exposure. Similarly, pharmacological RIPK1 kinase inhibition significantly attenuated elastase-induced emphysema and lung function decline. Finally, RNA-seq on lung tissue of CS-exposed mice revealed downregulation of cell death and inflammatory pathways upon pharmacological RIPK1 kinase inhibition.
RIPK1 kinase inhibition is protective in experimental models of COPD and may represent a novel promising therapeutic approach.
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Current treatments for salivary gland (SG) hypofunction are palliative and do not address the underlying cause or progression of the disease. SG-derived stem cells have the potential to treat SG hypofunction, but their isolation is challenging, especially when the tissue has been damaged by disease or irradiation for head and neck cancer. In the current study, we test the hypothesis that multipotent bone marrow-derived mesenchymal stem cells (BM-MSCs) in a rat model are capable of trans-differentiating to the SG epithelial cell lineage when induced by a native SG-specific extracellular matrix (SG-ECM) and thus may be a viable substitute for repairing damaged SGs.
Rat BM-MSCs were treated with homogenates of decellularized rat SG-ECM for one hour in cell suspension and then cultured in tissue culture plates for 7 days in growth media. By day 7, the cultures contained cell aggregates and a cell monolayer. The cell aggregates were hand-selected under a dissecting microscope, transferred to a new tissue culture dish, and cultured for an additional 7 days in epithelial cell differentiation media. Cell aggregates and cells isolated from the monolayer were evaluated for expression of SG progenitor and epithelial cell specific markers, cell morphology and ultrastructure, and ability to form SG-like organoids in vivo.
The results showed that this approach was very effective and guided the trans-differentiation of a subpopulation of CD133-positive BM-MSCs to the SG epithelial cell lineage. These cells expressed amylase, tight junction proteins (Cldn 3 and 10), and markers for SG acinar (Aqp5 and Mist 1) and ductal (Krt 14) cells at both the transcript and protein levels, produced intracellular secretory granules which were morphologically identical to those found in submandibular gland, and formed SG-like organoids when implanted in the renal capsule in vivo.
The results of this study suggest the feasibility of using autologous BM-MSCs as an abundant source of stem cells for treating SG hypofunction and restoring the production of saliva in these patients.
© 2022. The Author(s).