Lyophilized Human Amnionic Membrane Modulates the Macrophage Response During Wound Healing

Introduction: The immune system is central to progressing an injury through the wound healing cascade. However, comorbidities often lead to dysregulation of the inflammatory response and are implicated in wound chronicity or stalling in the inflammatory phase, necessitating clinical intervention. The amniotic membrane protects the developing fetus during gestation. The immunomodulatory properties of amniotic membrane may be leveraged therapeutically in wound healing through the application of amniotic tissue allografts. This study investigates the influence of lyophilized human amnion chorion membrane (LHACM*) on the acute inflammatory response of macrophages in vitro and in vivo.Methods:LHACM allografts were prepared using the PURION® process, consisting of gentle cleansing, lyophilization and terminal sterilization. Human THP-1 macrophages were challenged with lipopolysaccharide (LPS) and human interferon gamma (IFNγ), in the presence or absence of various doses of LHACM eluate, and subsequently harvested for measurement of viability by flow cytometry. Additionally, macrophages grown in the presence or absence of LHACM were fed CFSE-labeled dead Jurkat cell debris to measure efferocytosis. In vivo, excisional wounds were created on the dorsum of athymic nude mice followed by application of LHACM. Macrophage response was evaluated by flow cytometry on day 3 post treatment.Results:LHACM decreases macrophage death amid pro-inflammatory stimulation with LPS and IFNγ and exhibits no cytotoxic effect on resting macrophages at the concentrations tested. Macrophages treated with LHACM exhibit a blended macrophage phenotype and increase the rate at which macrophages consume dead cell debris. In vivo, LHACM does not influence the overall number of macrophages in the wound; however, LHACM does alter the ratio of macrophage phenotypes in favor of a pro-repair phenotype.Discussion: These data demonstrate that LHACM modulates features of inflammatory macrophage biology in vitro by enhancing pro-reparative functions including cell survival and efferocytosis. Furthermore, in vivo data revealed the influence of LHACM on macrophage polarization. LHACM enhances the presence of pro-reparative macrophages. This data suggests a potential cellular mechanism by which LHACM facilitates an efficient and appropriate inflammatory response to support the healing cascade and tissue repair.References: