Motor and sensory Schwann cell phenotype commitment is diminished by extracorporeal shockwave treatment in vitro

Schwann Cells Contribute to Alveolar Bone Regeneration by Promoting Cell Proliferation

The plasticity of Schwann cells (SCs) following nerve injury is a critical feature in the regeneration of peripheral nerves as well as surrounding tissues. Here, we show a pivotal role of Schwann cell-derived cells in alveolar bone regeneration through the specific ablation of proteolipid protein 1 (Plp)-expressing cells and the transplantation of teased nerve fibers and associated cells. With inducible Plp specific genetic tracing, we observe that Plp⁺ cells migrate into wounded alveolar defect and dedifferentiate into repair SCs. Notably, these cells barely transdifferentiate into osteogenic cell lineage in both SCs tracing model and transplant model, but secret factors to enhance the proliferation of alveolar skeletal stem cells (aSSCs). As to the mechanism, this effect is associated with the upregulation of extracellular matrix (ECM) receptors and receptor tyrosine kinases (RTKs) signaling and the downstream extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase (MAPK) pathway and the phosphoinositide 3-kinase-protein kinase B (PI3K-Akt) pathway. Collectively, our data demonstrate that SCs dedifferentiate after neighboring alveolar bone injury and contribute to bone regeneration mainly by a paracrine function. © 2022 American Society for Bone and Mineral Research (ASBMR).

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

Investigations reporting positive effects of extracorporeal shockwave therapy (ESWT) on nerve regeneration are limited to the rat sciatic nerve model. The effects of ESWT on muscle-in-vein conduits (MVCs) have also not been investigated yet. This study aimed to evaluate the effects of ESWT after repair of the rat median nerve with either autografts (ANGs) or MVCs. In male Lewis rats, a 7 mm segment of the right median nerve was reconstructed either with an ANG or an MVC. For each reconstructive technique, one group of animals received one application of ESWT while the other rats served as controls. The animals were observed for 12 weeks, and nerve regeneration was assessed using computerized gait analysis, the grasping test, electrophysiological evaluations and histological quantification of axons, blood vessels and lymphatic vasculature. Here, we provide for the first time a comprehensive analysis of ESWT effects on nerve regeneration in a rat model of median nerve injury. Furthermore, this study is among the first reporting the quantification of lymphatic vessels following peripheral nerve injury and reconstruction in vivo. While we found no significant direct positive effects of ESWT on peripheral nerve regeneration, results following nerve repair with MVCs were significantly inferior to those after ANG repair.

Physical Considerations for In Vitro ESWT Research Design

In vitro investigations, which comprise the bulk of research efforts geared at identifying an underlying biomechanical mechanism for extracorporeal shock wave therapy (ESWT), are commonly hampered by inadequate descriptions of the underlying therapeutic acoustical pressure waves. We demonstrate the necessity of in-situ sound pressure measurements inside the treated samples considering the significant differences associated with available applicator technologies and cell containment. A statistical analysis of pulse-to-pulse variability in an electrohydraulic applicator yields a recommendation for a minimal pulse number of n = 300 for cell pallets and suspensions to achieve reproducible treatments. Non-linear absorption behavior of sample holders and boundary effects are shown for transient peak pressures and applied energies and may serve as a guide when in-situ measurements are not available or can be used as a controllable experimental design factor. For the use in microbiological investigations of ESWT we provide actionable identification of common problems in describing physical shockwave parameters and improving experimental setups by; (1) promoting in-situ sound field measurements, (2) statistical evaluation of applicator variability, and (3) extrapolation of treatment parameters based on focal and treatment volumes.