Xiaorui Yu

Rationale: Mesenchymal stem cells (MSCs) possess potent immunomodulatory capability, but occasionally, clinical application of MSCs is hindered by compromised cell functionality and insufficient therapeutic efficacy.

Photoreceptor apoptosis is the main pathological feature of retinal degenerative diseases; however, the underlying molecular mechanism has not been elucidated. Recent studies have shown that N‐myc downstream regulated gene 2 (NDRG2) exerts a neuroprotective effect on the brain and spinal cord. In addition, our previous studies have confirmed that NDRG2 is expressed in mouse retinal photoreceptors and counteracts N ‐methyl‐ N ‐nitrosourea (MNU)‐induced apoptosis. However, the underlying molecular mechanism remains unclear. In this study, we observed that the expression of NDRG2 was not only significantly inhibited in photoreceptors after MNU treatment but also after hydrogen peroxide treatment, and photoreceptor apoptosis was alleviated or aggravated after overexpression or knockdown of NDRG2 in the 661W photoreceptor cell line, respectively. The apoptosis inhibitor Z‐VAD‐FMK rescued photoreceptor apoptosis induced by MNU after NDRG2 knockdown. Next, we screened and identified tissue inhibitor of metalloproteinases 3 (TIMP3) as the downstream molecule of NDRG2 in 661W cells by using quantitative real‐time polymerase chain reaction. TIMP3 exerts a neuroprotective effect by inhibiting the expression of matrix metalloproteinases (MMPs). Subsequently, we found that signal transducer and activator of transcription 3 (STAT3) mediated the NDRG2‐associated regulation of TIMP3. Finally, we overexpressed NDRG2 in mouse retinal tissues by intravitreally injecting an adeno‐associated virus with mouse NDRG2 in vivo . Results showed that NDRG2 upregulated the expression of phospho‐STAT3 (p‐STAT3) and TIMP3, while suppressing MNU‐induced photoreceptor apoptosis and MMP expression. Our findings revealed how NDRG2 regulates the STAT3/TIMP3/MMP pathway and uncovered the molecular mechanism underlying its neuroprotective effect on mouse retinal photoreceptors.

Photoreceptor apoptosis is recognized as one key pathogenesis of retinal degeneration, the counteraction of which represents a promising approach to safeguard visual function. Recently, mesenchymal stem cell transplantation (MSCT) has demonstrated immense potential to treat ocular disorders, in which extracellular vesicles (EVs), particularly exosomes, have emerged as effective ophthalmological therapeutics. However, whether and how MSCT protects photoreceptors against apoptotic injuries remains largely unknown. Here, we discovered that intravitreal MSCT counteracted photoreceptor apoptosis and alleviated retinal morphological and functional degeneration in a mouse model of photoreceptor loss induced by N-methyl-N-nitrosourea (MNU). Interestingly, effects of MSCT were inhibited after blockade of exosomal generation by GW4869 preconditioning. Furthermore, MSC-derived exosomal transplantation (EXOT) effectively suppressed MNU-provoked photoreceptor injury. Notably, therapeutic efficacy of MSCT and EXOT on MNU-induced retinal degeneration was long-lasting as photoreceptor preservance and retinal maintenance were detected even after 1–2 months post to injection for only once. More importantly, using a natural occurring retinal degeneration model caused by a nonsense mutation of Phosphodiesterase 6b gene (Pde6b^mut), we confirmed that MSCT and EXOT prevented photoreceptor loss and protected long-term retinal function. In deciphering therapeutic mechanisms regarding potential exosome-mediated communications, we identified that miR-21 critically maintained photoreceptor viability against MNU injury by targeting programmed cell death 4 (Pdcd4) and was transferred from MSC-derived exosomes in vivo for functional regulation. Moreover, miR-21 deficiency aggravated MNU-driven retinal injury and was restrained by EXOT. Further experiments revealed that miR-21 mediated therapeutic effects of EXOT on MNU-induced photoreceptor apoptosis and retinal dysfunction. These findings uncovered the efficacy and mechanism of MSCT-based photoreceptor protection, indicating exosomal miR-21 as a therapeutic for retinal degeneration.

Zinc finger protein 804A (ZNF804A) has been identified by genome‑wide association studies as a robust risk gene in schizophrenia, but how ZNF804A contributes to schizophrenia and its upstream regulation remains unknown. Previous studies have indicated that microRNAs (miRs) are key factors that regulate the expression levels of their target genes. The present study revealed significantly increased expression of miR‑148b‑3p in the peripheral blood of patients with first‑onset schizophrenia compared with healthy controls, and bioinformatics analysis predicted that the ZNF804A gene is a target of miR‑148b‑3p. Therefore, the present study investigated the possible upstream regulation of ZNF804A by miR‑148b‑3p in the human neuroblastoma SH‑SY5Y cell line, and assessed the implications for schizophrenia. The results revealed significantly reversed expression levels of miR‑148b‑3p (P=0.0051) and ZNF804A (P=0.0218) in the peripheral blood of patients with first‑onset schizophrenia compared with healthy individuals. Furthermore, it was demonstrated that miR‑148b‑3p directly targeted ZNF804A via binding to conserved target sites in the 3'‑untranslated region of ZNF804A mRNA, where it inhibited the endogenous expression of ZNF804A at both the mRNA (P=0.048) and protein levels (P=0.013) in SH‑SY5Y cells. Furthermore, miR‑148b‑3p was revealed to regulate the expression levels of catechol‑O‑methyltransferase (COMT) and serine protease 16 (PRSS16) by targeting ZNF804A in SH‑SY5Y cells. Collectively, the present results indicated that there was a direct upstream regulation of the schizophrenia risk gene ZNF804A by miR‑148b‑3p, which contributed to the regulation of the downstream genes COMT and PRSS16. Thus, the miR‑148b‑3p/ZNF804A/COMT/PRSS16 pathway may play an important role in the pathophysiology of schizophrenia, and may serve as a potential target in drug discovery and gene therapy for this disorder.

Photoreceptor cell death is recognized as the key pathogenesis of retinal degeneration, but the molecular basis underlying photoreceptor-specific cell loss in retinal damaging conditions is virtually unknown. The N-myc downstream regulated gene (NDRG) family has recently been reported to regulate cell viability, in particular NDRG1 has been uncovered expression in photoreceptor cells. Accordingly, we herein examined the potential roles of NDRGs in mediating photoreceptor-specific cell loss in retinal damages. By using mouse models of retinal degeneration and the 661 W photoreceptor cell line, we showed that photoreceptor cells are indeed highly sensitive to light exposure and the related oxidative stress, and that photoreceptor cells are even selectively diminished by phototoxins of the alkylating agent N-Methyl-N-nitrosourea (MNU). Unexpectedly, we discovered that of all the NDRG family members, NDRG2, but not the originally hypothesized NDRG1 or other NDRG subtypes, was selectively expressed and specifically responded to retinal damaging conditions in photoreceptor cells. Furthermore, functional experiments proved that NDRG2 was essential for photoreceptor cell viability, which could be attributed to NDRG2 control of the photo-oxidative stress, and that it was the suppression of NDRG2 which led to photoreceptor cell loss in damaging conditions. More importantly, NDRG2 preservation contributed to photoreceptor-specific cell maintenance and retinal protection both in vitro and in vivo. Our findings revealed a previously unrecognized role of NDRG2 in mediating photoreceptor cell homeostasis and established for the first time the molecular hallmark of photoreceptor-specific cell death as NDRG2 suppression, shedding light on improved understanding and therapy of retinal degeneration.

Bone tissue regeneration was closely associated with osteogenesis and angiogenesis. The harmonious regulation of osteogenetic and angiogenic growth factors would enhance bone regeneration, while the imbalance of that would lead to local excessive bone formation or vascular mass due to exogenous delivery. Therefore, microRNA is believed to regulate multiple metabolism progress through endogenous signaling pathways on the gene level. In this work, we identified microRNA 378 as a positive regulator of osteogenesis and angiogenesis simultaneously and also observed an increase of microRNA 378 than control in human bone marrow mesenchymal stem cells (hBMMSCs) after osteoblast induction. Besides, osteogenetic and angiogenic gene expression increased simultaneously after overexpression of microRNA 378. Moreover, alizarin red staining and alkaline phosphatase (ALP) staining enhanced, and secretion of vascular endothelial growth factor (VEGF) increased. In this way, we believed miR378 was an ideal target to osteogenesis-angiogenesis coupling for bone regeneration, which provides a potential tool for the gene therapy of bone regeneration.

Retinal degenerative diseases are characterized by photoreceptor cell loss. Photoreceptor cell loss leading to retinal degeneration can be induced by N-methyl-N-nitrosourea (MNU), which was widely used to mimic the pathology. However, the mechanism by which MNU induces photoreceptor cell loss is still largely unknown. The purpose of the present study was to investigate whether phosphorylation of glycogen synthase kinase-3β (p-GSK-3β) is a potent mediator of MNU-induced retinal degeneration and how p-GSK-3β affects the process. MNU-induced photoreceptor cell loss was evaluated in Sprague-Dawley (SD) rat retinas. GSK-3β and Akt expression levels did not change during MNU-induced retinal degeneration but the phosphorylation of GSK-3β and Akt was decreased by MNU treatment. Lithium chloride (LiCl), which increases p-GSK-3β level and active-β-catenin level, reversed retinal degeneration induced by MNU treatment. These results suggest that GSK-3β activation is closely related to photoreceptor cell loss and that the application of the GSK-3β inhibitor LiCl could activate Wnt/β-catenin signaling pathway and reduce photoreceptor cell loss induced by MNU. Our findings indicate that inhibition of GSK-3β activation may be a potential therapeutic target for retinal degeneration induced by photoreceptor cell loss.