Abstract
Severe peripheral nerve injuries often result in partial repair and lifelong disabilities in patients. New surgical techniques and better graft tissues are being studied to accelerate regeneration and improve functional recovery. Currently, limited tools are available to provide in vivo monitoring of changes in nerve physiology such as myelination and vascularization, and this has impeded the development of new therapeutic options. We have developed a wide-field and label-free functional microscopy platform based on angiographic and vectorial birefringence methods in optical coherence tomography (OCT). By incorporating the directionality of the birefringence, which was neglected in the previously reported polarization-sensitive OCT techniques for nerve imaging, vectorial birefringence contrast reveals internal nerve microanatomy and allows for quantification of local myelination with superior sensitivity. Advanced OCT angiography is applied in parallel to image the three-dimensional vascular networks within the nerve over wide-fields. Furthermore, by combining vectorial birefringence and angiography, intraneural vessels can be discriminated from those of the surrounding tissues. The technique is used to provide longitudinal imaging of myelination and revascularization in the rodent sciatic nerve model, i.e. imaged at certain sequential time-points during regeneration. The animals were exposed to either crush or transection injuries, and in the case of transection, were repaired using an autologous nerve graft or acellular nerve allograft. Such label-free functional imaging by the platform can provide new insights into the mechanisms that limit regeneration and functional recovery, and may ultimately provide intraoperative assessment in human subjects.
Highlights
Peripheral nerve injuries (PNIs) affect an estimated 20 million Americans each year, with an annual cost to the US healthcare system estimated at $150 billion[1]
By measuring the vectorial birefringence properties of the peripheral nerve microenvironment, we have demonstrated new capabilities to longitudinally characterize critical biological parameters of the peripheral nerve
In comparison to existing microscopies, the Optical coherence tomography (OCT) methods demonstrated here offer higher speeds, deeper imaging, wider-fields, and the ability to characterize multiple parameters without transgenic modifications or exogenous labels. The latter can be a critical advantage in many experimental settings including trauma, wherein, for example, label-based angiography is degraded by extravasation due to high permeability of wound vessels
Summary
Peripheral nerve injuries (PNIs) affect an estimated 20 million Americans each year, with an annual cost to the US healthcare system estimated at $150 billion[1]. Multiphoton, coherent anti-Stokes Raman scattering (CARS), and stimulated Raman scattering (SRS) microscopies have been applied to the peripheral nervous system[13,14,15,16,17,18,19], and provide a unique visualization of critical nerve parameters Because these microscopies interrogate small fields and image only to several hundred microns of depth in tissue, they do not effectively report on properties that span larger scales. We show that the combination of vectorial birefringence and angiography within the same platform allows intraneural vessels to be discriminated from those of the surrounding tissue, and thereby provides a clearer measure of function of the revascularized tissue We use this platform to record longitudinal (i.e., over time) measures of nerve degeneration and regeneration processes across crush and transection/repair injuries, and across different graft types. The results demonstrate wide-field vectorial birefringence OCT and angiography as a powerful tool in the study of PNIs, and in the in vivo evaluation of novel repair procedures and graft materials
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
