Spinal cord injury transiently alters Meissner's corpuscle density in the digit pads of macaque monkeys

Abstract

Meissner's corpuscles (MCs) are cutaneous mechanoreceptors found in glabrous skin and are exquisitely sensitive to light touch. Along with other receptors, they provide continuous sensory feedback that informs the execution of fine manual behaviors. Following cervical spinal deafferentation injuries, hand use can be initially severely impaired, but substantial recovery occurs over many weeks, even when ~95% of the original input is permanently lost. While most SCI research focuses on central neural pathway responses, little is known about the role of peripheral receptors in facilitating recovery. We begin to address this by asking the following: (1) What is the normal pattern of MCs in the distal pads of all five digits in the macaque monkey (with hands similar to humans)? (2) What happens to these receptors 4–5 months following either a dorsal column lesion (DCL) or a combined dorsal root/dorsal column lesion (DRL/DCL), when functional recovery is largely complete? (3) What happens chronically, 12–14 months later? Our findings show that in normal monkeys, MCs are densest in the distal pads of the opposing thumb and index finger, with the greatest concentration on the thumb. This reflects a close functional relationship between receptor density and precision grip. At 4–5 months post‐injury, there was a (~30%) loss of MCs on the deafferented digits of the injured hand compared with the contralateral side. However, 12–14 months after a DRL/DCL, receptor densities had returned to normal levels. Our findings indicate a complex peripheral response and highlight the importance of the periphery in shaping central changes.

Reorganization of the Primate Dorsal Horn in Response to a Deafferentation Lesion Affecting Hand Function

“…3, 4), yet it is difficult to determine whether sensory perception has returned to normal or whether they experience hypersensitivity of the affected fingers. We know that Meissner's corpuscles, which reduce in number over the months following a DRL/DCL, repopulate within a year post-lesion (Crowley et al, 2019), but we do not know whether their functionality could be considered normal. In addition, little is known about the functionality of the afferent or efferent sprouts at any of the C1-T2 segmental levels, or whether this growth is useful or maladaptive (Florence et al, 1994;Koerber et al, 1994).…”

“…And, even though the overall input territory to the dorsal horn remained significantly reduced at this time point, this sprouting was considerable. Importantly, recovery has occurred at this point, so the greatly reduced afferent population, fed by a reduced number of peripheral receptors (Crowley et al, 2019), is able to support a high level of digit function (Darian-Smith and Ciferri, 2005).…”

Reorganization of the Primate Dorsal Horn in Response to a Deafferentation Lesion Affecting Hand Function

“…And, even though the overall input territory to the dorsal horn remained significantly reduced at this time-point, this sprouting was considerable. Importantly, manual dexterity has recovered at this point, so the greatly reduced afferent population, fed by a reduced number of peripheral receptors (Crowley et al, 2019), is able to support a high level of digit function (Darian-Smith and Ciferri, 2005).…”

Re-evaluation of the distribution of Meissner’s corpuscles in human skin

“…Because many Meissner’s corpuscles are on the hands and feet, most studies have examined them in the fingertips and palms. Differences in the distribution of Meissner’s corpuscles have been reported between the hands of males and females, by finger region, and in patients with neurological diseases [ 9 - 11 ].…”