Study of human cutaneous sensory corpuscles using double immunolabelling and confocal laser scanning microscopy

Pacinian corpuscles in the human fetal foot: A study using 3D reconstruction and immunohistochemistry

PURPOSE

Our group had recently described human hand Pacinian corpuscles (PCs): the hand PCs are not simply arranged along the digital palmar nerves but often exhibited specific morphologies known uncommonly. However, there is still no or few information about human foot PCs.

MATERIALS AND METHODS

We observed transverse sections of all five toes including the interdigital area obtained from 12 feet of eight fetuses at 28-33 weeks (crown-rump length 230-290mm). Serial sections were prepared for 3D reconstructions and measurement.

RESULTS

Foot PCs were characterized by (1) a dense distribution in the interdigital area in contrast to a few PCs in the distal tip of the all five toes; (2) abundant dorsal PCs including those in the nail bed and: (3) a long chain of PCs in the flexor tendon sheath of all five toes. Therefore, a distal dominance was not evident in the foot in contrast to the hand and, a tendon sheath contained much greater numbers of PCs than the hand. A tree-like or bouquet-like arrangement of PCs along a short perforating artery to the palmar digital skin was seen in the foot as we had described in the hand. The tree of foot PCs was sometimes seen laying transversely along the digital skin surface, not toward the skin.

CONCLUSION

It is still unknown that, in utero, how the PCs distribution became different between the hand and foot: it might be determined genetically in a region-specific manner.

Two-Photon Imaging of DiO-Labelled Meissner Corpuscle in Living Mouse's Fingertip

Meissner corpuscles are the fast adapting type I (FA-I) mechanoreceptor that locates at the dermal papillae of skin. The Meissner corpuscle is well known for its complex structure, consisting of spiral axons, lamellar cells, and a collagen capsule. Fluorescent microscopy has become a convenient method for observing the Meissner corpuscle and its inner structure. This method requires preparing samples with fingertip cross-sections and performing antibody staining before observation. Various kinds of microscopy can be used for observation, such as confocal microscopy, transmission electron microscopy (TEM), or scanning electron microscopy (SEM). Although the anatomical shape, distribution, and components of Meissner corpuscle are recognized, they have been mostly determined from observations of fixed tissues. Therefore, knowledge of mechanical transduction is limited by the lack of in vivo experiments and individual differences among samples. In this study, we propose a novel less invasive imaging method that incorporates a staining technique with lipophilic carbocyanine [Formula: see text] and two-photon microscopy. This combination allows us to repetitively observe the Meissner corpuscle in a living mouse.

Brain-derived neurotrofic factor and its receptor TrkB are present, but segregated, within mature cutaneous Pacinian corpuscles of Macaca fascicularis

Some mechanoreceptors in mammals depend totally or in part on the neurotrophins brain-derived neurotrophic factor (BDNF) and neurotrophin-4 (NT-4), and their receptor TrkB, for development and maintenance. These actions are presumably exerced regulating the survival of discrete sensory neurons in the dorsal root ganglia which form mechanoreceptors at the periphery. In addition, the cells forming the mechanoreceptors also express both neurotrophins and their receptors although large differences have been described among species. Pacinian corpuscles are rapidly adapting low-threshold mechanoreceptors whose dependence from neurotrophins is not known. In the present study, we analyzed expression of TrkB and their ligands BDNF and NT-4 in the cutaneous Pacinian corpuscles of Macaca fascicularis using immunohistochemistry and fluorescent microscopy. TrkB immunoreactivity was found in Pacinian corpuscles where it co-localized with neuron-specific enolase, and occasionally with S100 protein, thus suggesting that TrkB expression is primarily into axons but also in the lamellar cells and even in the outer core. On the other hand, BDNF immunoreactivity was found the inner core cells where it co-localized with S100 protein but also in the innermost layers of the outer core; NT-4 immunostaining was not detected. These results describe for the first time the expression and distribution of a full neurotrophin system in the axon-inner core complex of mature Pacinian corpuscles. The data support previous findings demonstrating large differences in the expression of BDNF-TrkB in mammalian mechanoreceptors, and also suggest the existence of a retrograde trophic signaling mechanism to maintain morphological and functional integrity of sensory neurons supplying Pacinian corpuscles.

The Meissner and Pacinian sensory corpuscles revisited new data from the last decade

This article reviews the biochemical, physiological, and experimental data cumulated during the last decade on the Meissner and Pacinian corpuscles. It includes information about (i) the localization of molecules recently detected in sensory corpuscles; (ii) the unsolved problem of the accessory fibers in sensory corpuscles and the occurrence of myelin within them; (iii) the development of sensory corpuscles, especially their neuronal and growth factor dependency; (iv) the composition and functional significance of the extracellular matrix as an essential part of the mechanisms involved in the genesis of the stimuli generated in sensory corpuscles; (v) the molecular basis of mechanotransduction; (vi) a miscellaneous section containing sparse new data on the protein composition of sensory corpuscles, as well as in the proteins involved in live-death cell decisions; (vii) the changes in sensory corpuscles as a consequence of aging, the central, or peripheral nervous system injury; and finally, (viii) the special interest of Meissner corpuscles and Pacinian corpuscles for pathologists for the diagnosis of some peripheral neuropathies and neurodegenerative diseases.

Pacinian corpuscle development involves multiple Trk signaling pathways

The development of crural Pacinian corpuscles was explored in neonatal mutant mice lacking nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT3) or neurotrophin-4 (NT4), or their cognate Trk receptors. Deficits of the corpuscles and their afferents were greatest in NT3, less in BDNF, and least in NT4 null mice. Deletion of NGF or p75(NTR) genes had little or no impact. No Pacinian corpuscles were present in NT3;BDNF and NT3;NT4 double or NT3;BDNF;NT4 triple null mice. Deficits were larger in NT3 than TrkC mutants and were comparable to deficits observed in TrkB or TrkA mutants. Afferents of all corpuscles coexpressed TrkA and TrkB receptors, and some afferents coexpressed all three Trk receptors. Our results suggest that multiple neurotrophins, in particular NT3, regulate the density of crural Pacinian corpuscles, most likely by regulating the survival of sensory neurons. In addition, NT3/TrkB and/or NT3/TrkA signaling plays a greater role than NT3/TrkC signaling in afferents to developing Pacinian corpuscles.

Pathophysiological tissue changes associated with repetitive movement: a review of the evidence

Work-related musculoskeletal disorders (WMSDs) represent approximately one third of workers' compensation costs in US private industry, yet estimates of acceptable exposure levels for forceful and repetitive tasks are imprecise, in part, due to lack of measures of tissue injury in humans. In this review, the authors discuss the scope of upper-extremity WMSDs, the relationship between repetition rate and forcefulness of reaching tasks and WMSDs, cellular responses to injury in vivo and in vitro, and animal injury models of repetitive, forceful tasks. The authors describe a model using albino rats and present evidence related to tissue injury and inflammation due to a highly repetitive reaching task. A conceptual schematic for WMSD development and suggestions for further research are presented. Animal models can enhance our ability to predict risk and to manage WMSDs in humans because such models permit the direct observation of exposed tissues as well as motor behavior.

Development of Meissner-like and Pacinian sensory corpuscles in the mouse demonstrated with specific markers for corpuscular constituents

The development of Meissner-like and Pacinian corpuscles was studied in mice [from postnatal day (Pd) 0 to 42] by using immunohistochemistry for specific corpuscular constituents. The battery of antigens investigated included PGP 9.5 protein and neurofilaments, as markers for the central axon; S100 protein, vimentin, and p75(LNGFR) protein, to show Schwann-related cells; and epithelial membrane antigen to identify perineurial-related cells. In Meissner-like corpuscles immunoreactivity (IR) for neuronal markers was found by Pd7 and later. The lamellar cells of these corpuscles expressed first S100 protein IR (Pd7 to Pd42), then vimentin IR (Pd12 to Pd42), and transitory p75(LNGFR) IR (Pd7 to Pd19-20). Vimentin IR, but not epithelial membrane antigen, was detected in the capsule-like cells of the Meissner-like corpuscles. On the other hand, the density of Meissner-like corpuscles progressively increased from Pd0 to Pd19-20. Pacinian corpuscles were identified by Pd7. From this time to Pd42 the central axon showed IR for neuronal markers, and the inner core cells were immunoreactive for S100 protein. Moreover, vimentin IR was detected in the inner core cells by Pd19 and later. Unexpectedly, the central axons displayed S100 protein IR (from Pd7 to P28), while p75(LNGFR) protein IR or epithelial membrane antigen IR were never detected. Taken together, and based on the expression of the assessed antigens alone, the present results suggest that the Meissner-like and the Pacinian corpuscles in mice become mature around Pd19-Pd28 and Pd20, respectively. Furthermore, these results provide a baseline timetable for future studies in the normal or altered development of sensory corpuscles in mice since specific sensory corpuscles are functionally associated with different subtypes of sensory neurons the development of which is selectively disturbed in genetically manipulated mice.

PS-100 and NF 70-200 double immunolabeling for human digital skin meissner corpuscle 3D imaging

For detailed study of complex structures such as corpuscular mechanoreceptors, confocal microscopy can be used with multiple immunolabeling that identifies specifically different subcomponents. In addition, anatomic interpretation is enhanced by three-dimensional reconstruction. Confocal laser micrographs, reconstructed from serial images 1 microm thick of human skin Meissner corpuscles simultaneously immunostained for neurofilaments (NF 70-200) and protein S-100 (PS-100), clearly reveal the complex 3D relationship between Schwann-related lamellar cells immunoreactive for PS-100 and the nerve fibers marked by NF 70-200. The nerve fiber, after branching into the corpuscle, divides into several ramifications, presenting discoidal expansions and flattened fringed sections. The mean nerve diameter was 4 microm +/- 1 (2-5 microm) and the mean size of the discoidal expansions was 15 microm +/- 1 (7-30 microm). Corpuscle size varied from 30-140 +/- 1 microm in length and from 20-60 +/- 1 microm in diameter. This study confirms the presence of neural discoidal areas in Meissner's corpuscles, which are probably involved to some extent with the transduction process. Despite the accuracy of immunolabeling and imaging, an extracorpuscular neural network was never observed in the vicinity of corpuscles, thus giving doubt as to their existence. (J Histochem Cytochem 48:295-302, 2000)

Immunohistochemical localization of neurocalcin in human sensory neurons and mechanoreceptors

The localization of neurocalcin in the developing and adult human peripheral nervous system (dorsal root and sympathetic ganglia (DRG, SG), and enteric nervous system (ENS)) was investigated using immunohistochemistry. A subpopulation of large-sized neurons in DRG of 9 and 12 weeks old embryos showed immunoreactivity (IR), whereas the sympathetic ganglia or enteric neurons did not. In adults, neurocalcin IR was restricted to a subpopulation of large (13%) and intermediate (15%) sized neurons in DRG. The protein was also found in muscular (67%) and cutaneous (12%) nerve fibers, as well as in the axons supplying muscular (muscle spindles, Golgi's tendon organs, and perimysial Pacinian corpuscles) and cutaneous (Meissner's but not Pacinian corpuscles) mechanoreceptors, as well as motor end-plates. Present results demonstrate that neurocalcin in both developing and adult humans can be used as a specific marker for a subpopulation of sensory neurons coupled to proprioception and touch, and for axons of motoneurons forming motor end-plates.

p75 and TrkA neurotrophin receptors in human skin after spinal cord and peripheral nerve injury, with special reference to sensory corpuscles

Human skin, including nerves and sensory corpuscles, displays immunoreactivity (IR) for low- (p75) and high-affinity (TrkA-like) receptors for nerve growth factor (NGF), the best characterized member of the family of neurotrophins. This study was designed to analyze the changes induced by spinal cord and peripheral nerve injuries in the expression of neurotrophin receptors in digital skin, with special reference to nerves and sensory corpuscles. Skin biopsy samples were obtained from 1) the hand and toes of normal subjects, 2) below the level of the lesion of patients with spinal cord injury affecting dorsal and lateral funiculi, 3) the cutaneous territory of entrapped peripheral nerves (median and ulnar nerves), and 4) the cutaneous territory of sectioned and grafted nerves (median nerve). The pieces were formalin-fixed and paraffin-embedded, cut in serial sections, and processed for immunohistochemistry using antibodies against human p75 and TrkA proteins. The percentage of sensory corpuscles displaying IR for p75 and TrkA-like, as well as the intensity of IR developed within them, was assessed using quantitative image analysis. Spinal cord severance causes a decrease in p75 IR in Meissner and Pacinian corpuscles, whereas TrkA-like IR did not vary. In other nonnervous tissues (i.e., epidermis, sweat glands), both p75 and TrkA-like IR was diminished or even absent. Similar but more severe changes were encountered in the skin from the territory of entrapped nerves. Finally, in subjects with sectioned-grafted nerves, p75 IR was found close to controls in nerves, reduced in Meissner corpuscles, and absent in the inner core of the Pacinian ones; TrkA-like IR was in the perineurium, a small percentage of Meissner corpuscles (about 7%), and the outer core and capsule of the Pacinan corpuscles. In the nonnervous tissues, p75 IR was practically absent, whereas TrkA-like IR did not change. No changes in the expression of neurotrophin receptors were observed in Merkel cells of the different groups. Present results show the following: 1) expression of nerve p75 IR in human cutaneous sensory corpuscles is sensitive to central deafferentation, to blockade or difficulty in axonal transport, and to disruption of axonal continuity independently of possible restoration of axonal integrity due to grafts; 2) expression of TrkA-like IR in nerves and sensory corpuscles is sensitive only to nerve transection; 3) the corpuscular Schwann-related cells are the only cells involved in the above modifications, the perineurial cells remaining unchanged; 4) the expression of p75 and TrkA-like IR by Merkel cells is independent of normal innervation; 5) an adequate innervation of the skin seems to be necessary for the expression of p75 but not TrkA-like in nonneuronal cells, especially in the epidermis. A role for NGF in the maintenance of epidermis integrity is discussed.