Regenerative capacity in the lamprey spinal cord is not altered after a repeated transection

Abstract

29 The resilience of regeneration in vertebrate tissues is not well understood. Yet 30 understanding how well tissues can regenerate after repeated insults, and identifying 31 any limitations, is an important step towards elucidating the underlying mechanisms of 32 tissue plasticity. This is particularly challenging in tissues such as the nervous system, 33 which contain a large number of terminally differentiated cells (i.e. neurons) and that 34 often exhibits limited regenerative potential in the first place. However, unlike mammals 35 that exhibit very little spinal cord regeneration, many non-mammalian vertebrate 36 species, including lampreys, fishes, amphibians and reptiles, regenerate their spinal 37 cords and functionally recover even after a complete spinal cord transection. It is well 38 established that lampreys undergo full functional recovery of swimming behaviors after 39 a single spinal cord transection, which is accompanied by tissue repair at the lesion as 40 well as axon and synapse regeneration. Here, using the lamprey model, we begin to 41 explore resilience of spinal cord regeneration after a second spinal re-transection. We 42 report that by all functional and anatomical measures tested, the lampreys regenerated 43 after spinal re-transection just as robustly as after single transections. Recovery of 44 swimming behaviors, axon regeneration, synapse and cytoskeletal distributions, and 45 neuronal survival were nearly identical after a single spinal transection or a repeated 46 transection. Thus, regenerative potential in the lamprey spinal cord is largely unaffected 47 by spinal re-transection, indicating a greater persistent regenerative potential than exists 48 in some other highly-regenerative models. These findings establish a new path for 49 uncovering pro-regenerative targets that could be deployed in non-regenerative 50 conditions.

A Low Cost Antibody Signal Enhancer Improves Immunolabeling in Cell Culture, Primate Brain and Human Cancer Biopsy

“…ASE applicability can also be appreciated from other examples in the literature. Lamprey spinal cord cryosections were processed for triple immunofluorescence using ASE following repeated spinal transections to evaluate the resilience of its neuroregenerative capacity (Hanslik et al, 2019). Rodent brains were processed for triple immunogold electron microscopy using ASE, revealing a subcellular relocalization from the synapse periphery to within the synaptic cleft of GABA-A receptors during mutanthuntingtin evoked neurodegeneration (Rosas-Arellano et al, 2018).…”

Swimming kinematics and performance of spinal transected lampreys with different levels of axon regeneration

“…Following video recording at 10.5 weeks post injury, the descending reticulospinal axons were bulk labeled in order to assess the extent of axon regeneration, as previously described (Armstrong et al, 2003; Hanslik et al, 2018; Lau et al, 2013). Briefly, animals were re-anesthetized in MS-222, and a second spinal lesion was made 0.5 cm rostral to the original transection site.…”

“…By alternating these contractions on each side of the body the lamprey can generate successive traveling waves that make up each swimming cycle (McClellan, 1989; Williams, 1989; Williams and McMillen, 2015). The speed of the observed body wave is slower than that of the muscle contraction as a result of the interaction of forces acting on the body which include the forces generated by the muscles and the resistive forces of the fluid acting on the body (Ding et al, 2012; Tytell et al, 2010; Williams, 1989; Williams and McMillen, 2015) Demonstrating the robustness of this behavior, within several months after a complete spinal cord transection, lampreys are able to achieve robust recovery of swimming behaviors (Cohen et al, 1999; Hanslik et al, 2018; Katz et al, 2020; McClellan, 1989; McClellan, 1994; Oliphint et al, 2010; Rovainen, 1976; Selzer, 1978). Remarkably, they can also recover normal swimming after a second spinal re-transection (Hanslik et al, 2018).…”

“…Lampreys spontaneously recover swimming behaviors within 8-12 weeks after their spinal cord is transected rostrally at the level of the 5th gill due, in part, to long-distance regeneration of descending axons (McClellan, 1994; Oliphint et al, 2010; Rovainen, 1976). Initially, such transected animals are completely paralyzed (Hanslik et al, 2018; Oliphint et al, 2010). Axon regeneration begins two to three weeks after spinal cord transection with axons beginning to regenerate and some observed locomotor function just caudal to where the spinal cord was transected.…”

“…Despite lampreys being well documented as robust regenerators after a rostral spinal cord transection (e.g. in the gill region) and progressing from paralysis to full mobility within 10-12 weeks post injury, the extent of axon regeneration supporting this behavioral recovery is variable from animal-to-animal (Cohen et al, 1986; Hanslik et al, 2018; Oliphint et al, 2010; Rovainen, 1976; Selzer, 1978). Therefore, to understand the relationship between neural regeneration and behavioral recovery, we quantified the kinematics and swimming abilities of larval lampreys that had different levels of axon regeneration across the site of spinal transection and compared performance of control lamprey (non-transected) to lamprey who recovered from having their spinal cord transected 10.5 weeks prior at the 5 th gill or at mid-body.…”