An anti-inflammatory activation sequence governs macrophage transcriptional dynamics during tissue injury in zebrafish.

Macrophages are essential for tissue repair and regeneration. Yet, the molecular programs, as well as the timing of their activation during and after tissue injury are poorly defined. Using a high spatio-temporal resolution single cell analysis of macrophages coupled with live imaging after sensory hair cell death in zebrafish, we find that the same population of macrophages transitions through a sequence of three major anti-inflammatory activation states. Macrophages first show a signature of glucocorticoid activation, then IL-10 signaling and finally the induction of oxidative phosphorylation by IL-4/Polyamine signaling. Importantly, loss-of-function of glucocorticoid and IL-10 signaling shows that each step of the sequence is independently activated. Lastly, we show that IL-10 and IL-4 signaling act synergistically to promote synaptogenesis between hair cells and efferent neurons during regeneration. Our results show that macrophages, in addition to a switch from M1 to M2, sequentially and independently transition though three anti-inflammatory pathways in vivo during tissue injury in a regenerating organ.

Single-cell transcriptome analysis reveals three sequential phases of gene expression during zebrafish sensory hair cell regeneration.

Loss of sensory hair cells (HCs) in the mammalian inner ear leads to permanent hearing and vestibular defects, whereas loss of HCs in zebrafish results in their regeneration. We used single-cell RNA sequencing (scRNA-seq) to characterize the transcriptional dynamics of HC regeneration in zebrafish at unprecedented spatiotemporal resolution. We uncovered three sequentially activated modules: first, an injury/inflammatory response and downregulation of progenitor cell maintenance genes within minutes after HC loss; second, the transient activation of regeneration-specific genes; and third, a robust re-activation of developmental gene programs, including HC specification, cell-cycle activation, ribosome biogenesis, and a metabolic switch to oxidative phosphorylation. The results are relevant not only for our understanding of HC regeneration and how we might be able to trigger it in mammals but also for regenerative processes in general. The data are searchable and publicly accessible via a web-based interface.

Anti-biofilm activity of α-mangostin isolated from Garcinia mangostana L.

This study was carried out to further examine the anti-biofilm activity of α-mangostin (αMG) isolated from Garcinia mangostana L. grown in Vietnam, against a strongly biofilm producing Streptococcus mutans, a major causative agent of dental caries. The obtained data indicated that topical applications (twice-daily, 60 s exposure each) of 150 µM αMG during biofilm formation on the surfaces of hydroxyapatite disks (sHA) by S. mutans UA159 resulted in 30.7% reduction in biofilm accumulation after 68 h of growth. The treatment did not affect the viability of S. mutans cells in the biofilms. The surface activities of two key enzymes responsible for biofilm formation, i.e. the glycosyltransferases GtfB and GtfC, were reduced by 20 and 35%, respectively (vs. vehicle control, P < 0.05). Interestingly, αMG specifically targeted S. mutans in mixed biofilms, resulting in the decrease of the S. mutans population and total biofilm biomass. αMG was also found to accumulate within the biofilm of S. mutans up to 4.5 µg/biofilm, equal to a concentration of >10 µM/biofilm. In conclusion, this study confirmed anti-biofilm activity of αMG against S. mutans. A brief exposure to αMG may suppress biofilm formation by targeting key enzymes imvolved in biofilm formation.