Occurrence of Lymphangiogenesis in Peripheral Nerve Autografts Contrasts Schwann Cell-Induced Apoptosis of Lymphatic Endothelial Cells In Vitro

Abstract

Peripheral nerve injuries pose a major clinical concern world-wide, and functional recovery after segmental peripheral nerve injury is often unsatisfactory, even in cases of autografting. Although it is well established that angiogenesis plays a pivotal role during nerve regeneration, the influence of lymphangiogenesis is strongly under-investigated. In this study, we analyzed the presence of lymphatic vasculature in healthy and regenerated murine peripheral nerves, revealing that nerve autografts contained increased numbers of lymphatic vessels after segmental damage. This led us to elucidate the interaction between lymphatic endothelial cells (LECs) and Schwann cells (SCs) in vitro. We show that SC and LEC secretomes did not influence the respective other cell types’ migration and proliferation in 2D scratch assay experiments. Furthermore, we successfully created lymphatic microvascular structures in SC-embedded 3D fibrin hydrogels, in the presence of supporting cells; whereas SCs seemed to exert anti-lymphangiogenic effects when cultured with LECs alone. Here, we describe, for the first time, increased lymphangiogenesis after peripheral nerve injury and repair. Furthermore, our findings indicate a potential lymph-repellent property of SCs, thereby providing a possible explanation for the lack of lymphatic vessels in the healthy endoneurium. Our results highlight the importance of elucidating the molecular mechanisms of SC–LEC interaction.

ESWT Diminishes Axonal Regeneration following Repair of the Rat Median Nerve with Muscle-In-Vein Conduits but Not after Autologous Nerve Grafting

“…Our study was also among the first [ 49 , 77 , 92 , 93 ] to shine light on the involvement of lymphatic vasculature and lymphangiogenesis, respectively, in peripheral nerve repair and regeneration. Interestingly, we found that the number of lymphatics was drastically increased in both ANGs and MCVs following median nerve reconstruction.…”

“…We hypothesize that this observation can be explained by a study recently published by our group. In this work, we showed for the first time that Schwann cells induce apoptosis of lymphatic endothelial cells when cocultured in vitro via extended filopodia-like protrusions [ 49 ]. While this, on the one hand, explains the absence of lymphatic vessels inside uninjured murine peripheral nerves, these findings can be further extrapolated to the findings in the study at hand.…”

“…The IKOSA platform (KML Vision) was adopted to train two state-of-the-art deep neural network models in a supervised fashion. To quantify the lymphatic vessels, we applied our previously trained model to our image data as described elsewhere [ 49 ].…”

“… Schematic of the repaired median nerve with histological sections and their respective localization indicated as proximal, start graft, mid graft and distal. Dotted lines indicate histological cutting planes [ 49 ]. …”

Comprehensive ex vivo and in vivo preclinical evaluation of novel chemo enzymatic decellularized peripheral nerve allografts

“…Peripheral nerves (PNs) are highly specialized organs that connect the central nervous system through motor, sensory or autonomic pathways, with distal target organs ( Carriel et al, 2014 ). Histologically, PNs are composed to two well-defined tissues, the parenchyma or functional unit, formed by peripheral nerve fibers (PNFs), and the stroma or structural unit, formed by three specialized layers of connective tissue (the epineurium, the perineurium and the endoneurium) that provide blood and lymphatic vessels, and confer the structural and biomechanical properties to these essential organs ( Geuna et al, 2009 ; Hromada et al, 2022 ). Due to their wide anatomical distribution PNs are often affected by traumatic injuries of diverse nature or iatrogenic injuries during surgical procedures ( Robinson, 2000 ).…”