The Implementation of the 2020 Roadmap to Promote Good Registration Management (GRM) in APEC Region.

BACKGROUND: To promote the efficiency and quality of registration for medical products, the Asia-Pacific Economic Cooperation (APEC) Regulatory Harmonization Steering Committee (RHSC) has implemented a 2020 roadmap to promote the concept of GRM since 2011. Key outcomes of this roadmap are discussed in this article to provide recommendations for improved regulatory practices and accelerated regulatory convergence. METHODS: Adoption of relevant guidelines and delivery of training programs from the APEC Training Centers of Excellence for Regulatory Science (CoEs) have played a key role to promote capacity building, cooperation and convergence in good review practices (GRevPs) and good submission practices (GSubPs) for medical products among APEC economies. A key performance indicator (KPI) survey among the drug regulatory authorities (RAs) of APEC economies was conducted to understand the progress of this roadmap. RESULTS: The CoE programs have provided a unique opportunity to promote dialogues between regulatory authorities and industry and efficiently disseminated the concept of GRM among APEC economies. The results of the KPI survey indicated significant progress in the status of implementing GRevPs over the last ten years. CONCLUSIONS: To accelerate regulatory convergence among APEC economies, it is necessary to promote mutual trust and cooperation in approval of medical products over the time. Continuous training in GRevPs and GSubPs through the CoE platform would set the stage to achieve the goal in the next decade.

N-terminal functional domain of Gasdermin A3 regulates mitochondrial homeostasis via mitochondrial targeting.

BACKGROUND: The epidermis forms a critical barrier that is maintained by orchestrated programs of proliferation, differentiation, and cell death. Gene mutations that disturb this turnover process may cause skin diseases. Human GASDERMIN A (GSDMA) is frequently silenced in gastric cancer cell lines and its overexpression has been reported to induce apoptosis. GSDMA has also been linked with airway hyperresponsiveness in genetic association studies. The function of GSDMA in the skin was deduced by dominant mutations in mouse gasdermin A3 (Gsdma3), which caused skin inflammation and hair loss. However, the mechanism for the autosomal dominance of Gsdma3 mutations and the mode of Gsdma3's action remain unanswered. RESULTS: We demonstrated a novel function of Gsdma3 in modulating mitochondrial oxidative stress. We showed that Gsdma3 is regulated by intramolecular fold-back inhibition, which is disrupted by dominant mutations in the C-terminal domain. The unmasked N-terminal domain of Gsdma3 associates with Hsp90 and is delivered to mitochondrial via mitochondrial importer receptor Tom70, where it interacts with the mitochondrial chaperone Trap1 and causes increased production of mitochondrial reactive oxygen species (ROS), dissipation of mitochondrial membrane potential, and mitochondrial permeability transition (MPT). Overexpression of the C-terminal domain of Gsdma3 as well as pharmacological interventions of mitochondrial translocation, ROS production, and MPT pore opening alleviate the cell death induced by Gsdma3 mutants. CONCLUSIONS: Our results indicate that the genetic mutations in the C-terminal domain of Gsdma3 are gain-of-function mutations which unmask the N-terminal functional domain of Gsdma3. Gsdma3 regulates mitochondrial oxidative stress through mitochondrial targeting. Since mitochondrial ROS has been shown to promote epidermal differentiation, we hypothesize that Gsdma3 regulates context-dependent response of keratinocytes to differentiation and cell death signals by impinging on mitochondria.

APEC Workshop Report of Good Review Practices on Medical Products.

As part of the implementation of the 2020 Good Review Practices (GRevP) Roadmap championed by Chinese Taipei in the Asia-Pacific Economic Cooperation (APEC) Regulatory Harmonization Steering Committee (RHSC), the Taiwan Food and Drug Administration (TFDA) organized 2 workshops. The purpose of these workshops was to address the fundamental elements of a well-designed regulatory review system, to provide complementary modules for GRevP and approaches to the exchange and the use of product assessment reports between regulatory authorities, and to further promote regulatory efficiencies and best practices. The workshops brought together 81 regulatory representatives from 15 economies for the basic workshop and 133 from 20 economies for the advanced workshop. Participants forged a common understanding of GRevP and highlighted its importance. While the adoption of GRevP is key to building trust between agencies, each economy should address its needs and adopt its own best practices based on its resources and environment. The outcomes of these workshops could be used as a framework for the development of a GRevP best-practice document or could serve as material for further training in each economy.

Differential response of epithelial stem cell populations in hair follicles to TGF-ß signaling.

Epidermal stem cells residing in different locations in the skin continuously self-renew and differentiate into distinct cell lineages to maintain skin homeostasis during postnatal life. Murine epidermal stem cells located at the bulge region are responsible for replenishing the hair lineage, while the stem cells at the isthmus regenerate interfollicular epidermis and sebaceous glands. In vitro cell culture and in vivo animal studies have implicated TGF-ß signaling in the maintenance of epidermal and hair cycle homeostasis. Here, we employed a triple transgenic animal model that utilizes a combined Cre/loxP and rtTA/TRE system to allow inducible and reversible inhibition of TGF-ß signaling in hair follicle lineages and suprabasal layer of the epidermis. Using this animal model, we have analyzed the role of TGF-ß signaling in distinct phases of the hair cycle. Transient abrogation of TGF-ß signaling does not prevent catagen progression; however, it induces aberrant proliferation and differentiation of isthmus stem cells to epidermis and sebocyte lineages and a blockade in anagen re-entry as well as results in an incomplete hair shaft development. Moreover, ablation of TGF-ß signaling during anagen leads to increased apoptosis in the secondary hair germ and bulb matrix cells. Blocking of TGF-ß signaling in bulge stem cell cultures abolishes their colony-forming ability, suggesting that TGF-ß signaling is required for the maintenance of bulge stem cells. At the molecular level, inhibition of TGF-ß signaling results in a decrease in both Lrig1-expressing isthmus stem cells and Lrg5-expressing bulge stem cells, which may account for the phenotypes seen in our animal model. These data strongly suggest that TGF-ß signaling plays an important role in regulating the proliferation, differentiation, and apoptosis of distinct epithelial stem cell populations in hair follicles.

Notch signaling prevents mucous metaplasia in mouse conducting airways during postnatal development.

Goblet cell metaplasia and mucus overproduction contribute to the pathogenesis of chronic lung diseases, including asthma and chronic obstructive pulmonary disease (COPD). Notch signaling regulates cell fate decisions and is crucial in controlling goblet cell differentiation in the gut epithelium. Little is known, however, about how endogenous Notch signaling influences the goblet cell differentiation program that takes place in the postnatal lung. Using a combination of genetic and in vitro approaches here we provide evidence of a novel role for Notch in restricting goblet cell differentiation in the airway epithelium during the postnatal period. Conditional inactivation of the essential Notch pathway component Pofut1 (protein O-fucosyltransferase1) in Tgfb3-Cre-expressing mice resulted in an aberrant postnatal airway phenotype characterized by marked goblet cell metaplasia, decreased Clara cell number and increase in ciliated cells. The presence of the same phenotype in mice in which the Notch transcriptional effector Rbpjk was deleted indicated the involvement of the canonical Notch pathway. Lineage study in vivo suggested that goblet cells originated from a subpopulation of Clara cells largely present in proximal airways in which Notch was disrupted. The phenotype was confirmed by a panel of goblet cell markers, showed no changes in cell proliferation or altered expression of proinflammatory cytokines and was associated with significant downregulation of the bHLH transcriptional repressor Hes5. Luciferase reporter analysis suggested that Notch directly repressed MUC5AC transcription in lung epithelial cells. The data suggested that during postnatal life Notch is required to prevent Clara cells from differentiating into goblet cells.

Notch signaling regulates late-stage epidermal differentiation and maintains postnatal hair cycle homeostasis.

BACKGROUND: Notch signaling involves ligand-receptor interactions through direct cell-cell contact. Multiple Notch receptors and ligands are expressed in the epidermis and hair follicles during embryonic development and the adult stage. Although Notch signaling plays an important role in regulating differentiation of the epidermis and hair follicles, it remains unclear how Notch signaling participates in late-stage epidermal differentiation and postnatal hair cycle homeostasis. METHODOLOGY AND PRINCIPAL FINDINGS: We applied Cre/loxP system to generate conditional gene targeted mice that allow inactivation of critical components of Notch signaling pathway in the skin. Rbpj, the core component of all four Notch receptors, and Pofut1, an essential factor for ligand-receptor interactions, were inactivated in hair follicle lineages and suprabasal layer of the epidermis using the Tgfb3-Cre mouse line. Rbpj conditional inactivation resulted in granular parakeratosis and reactive epidermal hyperplasia. Pofut1 conditional inactivation led to ultrastructural abnormalities in the granular layer and altered filaggrin processing in the epidermis, suggesting a perturbation of the granular layer differentiation. Disruption of Pofut1 in hair follicle lineages resulted in aberrant telogen morphology, a decrease of bulge stem cell markers, and a concomitant increase of K14-positive keratinocytes in the isthmus of mutant hair follicles. Pofut1-deficent hair follicles displayed a delay in anagen re-entry and dysregulation of proliferation and apoptosis during the hair cycle transition. Moreover, increased DNA double stand breaks were detected in Pofut1-deficent hair follicles, and real time PCR analyses on bulge keratinocytes isolated by FACS revealed an induction of DNA damage response and a paucity of DNA repair machinery in mutant bulge keratinocytes. SIGNIFICANCE: our data reveal a role for Notch signaling in regulating late-stage epidermal differentiation. Notch signaling is required for postnatal hair cycle homeostasis by maintaining proper proliferation and differentiation of hair follicle stem cells.