Eggs hatch after about a week into tiny aquatic larvae that may molt up to a dozen times into increasingly larger bodies (instars). The last larval instar emerges from the water, breathes air (!), attaches to vegetation, and begins metamorphosis. A winged dragonfly emerges from a crack in the exoskeleton (now called the exuvia), pumping fluid into its new body and wings to expand and stiffen them. The immature dragonfly is called a teneral and is highly vulnerable to predation before its body is fully stiffened, colored, and functional. Depending on climate and migratory status, adults live for a few weeks to a month.
In regards to inflammation, the content released by our composite scaffold as well as PRPr treatment did not interfere with macrophage polarization per se, i.e., without an induction toward M1 or M2 phenotype. During physiological wound healing, macrophages drift from the initial pro-inflammatory M1 phenotype toward a resolution M2 phenotype over time (Mantovani et al., 2013). Therefore, a robust response from macrophages is essential in order to ensure that their function is fulfilled in all stages of the wound healing process. On the other hand, in chronic wounds, where inflammation persists, macrophages are found mainly in M1 pro-inflammatory phenotype (Krzyszczyk et al., 2018). Also, it has been established that PRP contains both pro and anti-inflammatory cytokines (Amable et al., 2013). In our study, we showed that the presence of PRPr and the composite scaffold did not modify the macrophage response in growth (M0) medium. However, when macrophages were challenged with pro- or anti-inflammatory factors (M1 and M2 medium, respectively), the secretion of both pro- (MIP1α and TNFα) and anti-inflammatory (IL1-ra) cytokines were modulated; PRPr dampened the production of MIP1α and the content released from our composite scaffolds allowed macrophages to secrete both MIP1α and TNFα to the same levels as 10% FBS, while increasing the level of IL1-ra secretion. Indeed, anti-inflammatory effects of PRP have previously been reported in different applications (Zhang et al., 2013; Moussa et al., 2017; Abdul Ameer et al., 2018); although other groups reported stimulation of both M1 and M2 markers (Escobar et al., 2018). The study of macrophage polarization is an evolving field, with several cytokines and markers expressed by subpopulations that may go beyond the classical M1/M2 and pro-/anti-inflammatory phenotypes (Chávez-Galán et al., 2015). Therefore, further work is needed to fully elucidate the role of PRP and our composite scaffold in inflammation, particularly in the context of wound healing. 2b1af7f3a8