Nerve Transfers for Brachial Plexus Reconstruction in Patients over 60 Years

Negative expectations regarding nerve reconstruction in the elderly prevail in the literature, but little is known about the effectiveness of nerve transfers in patients with brachial plexus injuries aged over 60 years. We present a series of five patients (1 female, 4 male) aged between 60 and 81 years (median 62.0 years) who underwent nerve reconstruction using multiple nerve transfers in brachial plexopathies. The etiology of brachial plexus injury was trauma (n = 2), or iatrogenic, secondary to spinal surgical laminectomy, tumor excision and radiation for breast cancer (n = 3). All but one patient underwent a one-stage reconstruction including neurolysis and extra-anatomical nerve transfer alone (n = 2) or combined with anatomical reconstruction by sural nerve grafts (n = 2). One patient underwent a two-stage reconstruction, which involved a first stage anatomical brachial plexus reconstruction followed by a second stage nerve transfer. Neurotizations were performed as double (n = 3), triple (n = 1) or quadruple (n = 1) nerve or fascicular transfers. Overall, at least one year postoperatively, successful results, characterized by a muscle strength of M3 or more, were restored in all cases, two patients even achieving M4 grading in the elbow flexion. This patient series challenges the widely held dogma that brachial plexus reconstruction in older patients will produce poor outcomes. Distal nerve transfers are advantageous as they shorten the reinnervation distance. Healthy, more elderly patients should be judiciously offered the whole spectrum of reconstructive methods and postoperative rehabilitation concepts to regain useful arm and hand function and thus preserve independence after a traumatic or nontraumatic brachial plexus injury.

Spinal cord from body donors is suitable for multicolor immunofluorescence

Immunohistochemistry is a powerful tool for studying neuronal tissue from humans at the molecular level. Obtaining fresh neuronal tissue from human organ donors is difficult and sometimes impossible. In anatomical body donations, neuronal tissue is dedicated to research purposes and because of its easier availability, it may be an alternative source for research. In this study, we harvested spinal cord from a single organ donor 2 h (h) postmortem and spinal cord from body donors 24, 48, and 72 h postmortem and tested how long after death, valid multi-color immunofluorescence or horseradish peroxidase (HRP) immunohistochemistry is possible. We used general and specific neuronal markers and glial markers for immunolabeling experiments. Here we showed that it is possible to visualize molecularly different neuronal elements with high precision in the body donor spinal cord 24 h postmortem and the quality of the image data was comparable to those from the fresh organ donor spinal cord. High-contrast multicolor images of the 24-h spinal cords allowed accurate automated quantification of different neuronal elements in the same sample. Although there was antibody-specific signal reduction over postmortem intervals, the signal quality for most antibodies was acceptable at 48 h but no longer at 72 h postmortem. In conclusion, our study has defined a postmortem time window of more than 24 h during which valid immunohistochemical information can be obtained from the body donor spinal cord. Due to the easier availability, neuronal tissue from body donors is an alternative source for basic and clinical research.

Structural and molecular characteristics of axons in the long head of the biceps tendon

The innervation of the long head of the biceps tendon (LHBT) is not sufficiently documented. This is a drawback since pathologies of the LHBT are a major source of shoulder pain. Thus, the study aimed to characterize structurally and molecularly nervous elements of the LHBT. The proximal part of 11 LHBTs was harvested intraoperatively. There were 8 female and 3 male specimens. Age ranged from 66 to 86 years. For structural analyses, nervous elements were viewed in the transmission electron microscope. For molecular characterization, we used general neuronal markers including antibodies against neurofilament and protein gene product 9.5 (PGP9.5) as well as specific neuronal markers including antibodies against myelin basic protein (MBP), calcitonin gene-related product (CGRP), substance P (SP), tyrosine hydroxylase (TH), and growth-associated protein 43 (GAP43). Anti-neurofilament and anti-PGP9.5 visualized the overall innervation. Anti-MBP visualized myelination, anti-CGRP and anti-SP nociceptive fibers, anti-TH sympathetic nerve fibers, and anti-GAP43 nerve fibers during development and regeneration. Immunolabeled sections were analyzed in the confocal laser scanning microscope. We show that the LHBT contains unmyelinated as well as myelinated nerve fibers which group in nerve fascicles and follow blood vessels. Manny myelinated and unmyelinated axons exhibit molecular features of nociceptive nerve fibers. Another subpopulation of unmyelinated axons exhibits molecular characteristics of sympathetic nerve fibers. Unmyelinated sympathetic fibers and unmyelinated nociceptive fibers express proteins that are found during development and regeneration. Present findings support the hypothesis that ingrowth of nociceptive fibers are the source of chronic tendon pain.

Axonal components of nerves innervating the human arm

OBJECTIVE

Axons traveling within the brachial plexus are responsible for the dexterous control of human arm and hand movements. Despite comprehensive knowledge on the topographical anatomy of nerves innervating the human upper limbs, the definite quantity of sensory and motor axons within this neural network remains elusive. Our aim was to perform a quantitative analysis of the axonal components of human upper limb nerves based on highly specific molecular features from spinal cord level to the terminal nerves at wrist level.

METHODS

Nerve specimen harvest at predefined harvesting sites (plexus roots and cords as well as major nerves originating from the brachial plexus innervating the arm and hand) was performed in 9 human heart-beating organ donors. Double immunofluorescence staining using antibodies against choline-acetyltransferase and neurofilament was performed to differentiate motor and sensory axons on nerve cross sections.

RESULTS

Three hundred fifty thousand axons emerge from the spinal cord to innervate the human upper limb, of which 10% are motor neurons. In all nerves studied, sensory axons outnumber motor axons by a ratio of at least 9:1. The sensory axon contribution increases when moving distally, whereas only 1,700 motor axons reach the hand to innervate the intrinsic musculature.

INTERPRETATION

Our results suggest that upper limb motor execution, and particularly dexterous coordination of hand movement, require an unexpectedly low number of motor neurons, with a large convergence of afferent input for feedback control. Ann Neurol 2017;82:396-408.

Nerve grafts bridging the thenar branch of the median nerve to the ulnar nerve to enhance nerve recovery: a report of three cases

We report a nerve graft procedure bridging the thenar branch of the median nerve to the ulnar nerve in three patients with ulnar nerve transection and defect at the mid-forearm. Ulnar nerve function was evaluated with electroneurography and quantitative sensory-motor testing before and after surgery, and at a 6-year follow-up. After surgery all patients showed electroneurographic evidence of median nerve innervation of the intrinsic muscles normally innervated by the ulnar nerve. The average strength was Grade 4 in the intrinsic muscles originally supplied by the ulnar nerve at the final follow-up. Our results indicate that the thenar branch of the median nerve may support ulnar nerve regeneration and so help prevent intrinsic muscles from irreversible atrophy, but our report is preliminary. This procedure should be validated by future clinical data, especially those with complete ulnar nerve transection at or above the elbow.

LEVEL OF EVIDENCE

IV.

Palisade Endings Are a Constant Feature in the Extraocular Muscles of Frontal-Eyed, But Not Lateral-Eyed, Animals

Purpose

To test whether palisade endings are a general feature of mammalian extraocular muscles (EOMs).

Methods

Thirteen species, some frontal-eyed (human, monkey, cat, and ferret), and others lateral-eyed (pig, sheep, calf, horse, rabbit, rat, mouse, gerbil, and guinea pig) were analyzed. Palisade endings were labeled by using different combinations of immunofluorescence techniques. Three-dimensional reconstructions of immunolabeled palisade endings were done.

Results

In all frontal-eyed species, palisade endings were a consistent feature in the rectus EOMs. Their total number was high and they exhibited an EOM-specific distribution. In particular, the number of palisade endings in the medial recti was significantly higher than in the other rectus muscles. In the lateral-eyed animals, palisade endings were infrequent and, when present, their total number was rather low. They were only found in ungulates (sheep, calf, pig, and horse) and in rabbit. In rodents (rat, guinea pig, mouse, and gerbil) palisade endings were found infrequently (e.g., rat) or were completely absent. Palisade endings in frontal-eyed species and in some lateral-eyed species (pig, sheep, calf, and horse) had a uniform morphology. They generally lacked α-bungarotoxin staining, with a few exceptions in primates. Palisade endings in other lateral-eyed species (rabbit and rat) exhibited a simplified morphology and bound α-bungarotoxin.

Conclusions

Palisade endings are not a universal feature of mammalian EOMs. So, if they are proprioceptors, not all species require them. Because in frontal-eyed species, the medial rectus muscle has the highest number of palisade endings, they likely play a special role in convergence.

Langerhans cell maturation is accompanied by induction of N-cadherin and the transcriptional regulators of epithelial-mesenchymal transition ZEB1/2

Langerhans cells (LCs) are a unique subset of dendritic cells (DCs) that express epithelial adhesion molecules, allowing them to form contacts with epithelial cells and reside in epidermal/epithelial tissues. The dynamic regulation of epithelial adhesion plays a decisive role in the life cycle of LCs. It controls whether LCs remain immature and sessile within the epidermis or mature and egress to initiate immune responses. So far, the molecular machinery regulating epithelial adhesion molecules during LC maturation remains elusive. Here, we generated pure populations of immature human LCs in vitro to systematically probe for gene-expression changes during LC maturation. LCs down-regulate a set of epithelial genes including E-cadherin, while they upregulate the mesenchymal marker N-cadherin known to facilitate cell migration. In addition, N-cadherin is constitutively expressed by monocyte-derived DCs known to exhibit characteristics of both inflammatory-type and interstitial/dermal DCs. Moreover, the transcription factors ZEB1 and ZEB2 (ZEB is zinc-finger E-box-binding homeobox) are upregulated in migratory LCs. ZEB1 and ZEB2 have been shown to induce epithelial-to-mesenchymal transition (EMT) and invasive behavior in cancer cells undergoing metastasis. Our results provide the first hint that the molecular EMT machinery might facilitate LC mobilization. Moreover, our study suggests that N-cadherin plays a role during DC migration.

Identification of Axl as a downstream effector of TGF-β1 during Langerhans cell differentiation and epidermal homeostasis

Transforming growth factor-β1 (TGF-β1) is a fundamental regulator of immune cell development and function. In this study, we investigated the effects of TGF-β1 on the differentiation of human Langerhans cells (LCs) and identified Axl as a key TGF-β1 effector. Axl belongs to the TAM (Tyro3, Axl, and Mer) receptor tyrosine kinase family, whose members function as inhibitors of innate inflammatory responses in dendritic cells and are essential to the prevention of lupus-like autoimmunity. We found that Axl expression is induced by TGF-β1 during LC differentiation and that LC precursors acquire Axl early during differentiation. We also describe prominent steady-state expression as well as inflammation-induced activation of Axl in human epidermal keratinocytes and LCs. TGF-β1-induced Axl enhances apoptotic cell (AC) uptake and blocks proinflammatory cytokine production. The antiinflammatory role of Axl in the skin is reflected in a marked impairment of the LC network preceding spontaneous skin inflammation in mutant mice that lack all three TAM receptors. Our findings highlight the importance of constitutive Axl expression to tolerogenic barrier immunity in the epidermis and define a mechanism by which TGF-β1 enables silent homeostatic clearing of ACs to maintain long-term self-tolerance.

miR-146a is differentially expressed by myeloid dendritic cell subsets and desensitizes cells to TLR2-dependent activation

Langerhans cells (LCs) in epithelia and interstitial dendritic cells (intDCs) in adjacent connective tissues represent two closely related myeloid-derived DC subsets that exert specialized functions in the immune system and are of clinical relevance for cell therapy. Both subsets arise from monocyte-committed intermediates in response to tissue-associated microenvironmental signals; however, molecular mechanisms underlying myeloid DC subset specification and function remain poorly defined. Using microarray profiling, we identified microRNA (miRNA) miR-146a to be constitutively expressed at higher levels in human LCs compared with intDCs. Moreover, miR-146a levels were low in monocytes and nondetectable in neutrophil granulocytes. Interestingly, constitutive high miR-146a expression in LCs is induced by the transcription factor PU.1 in response to TGF-beta1, a key microenvironmental signal for epidermal LC differentiation. We identified miR-146a as a regulator of monocyte and DC activation but not myeloid/DC subset differentiation. Ectopic miR-146a in monocytes and intDCs interfered with TLR2 downstream signaling and cytokine production, without affecting phenotypic DC maturation. Inversely, silencing of miR-146a in LCs enhanced TLR2-dependent NF-kappaB signaling. We therefore conclude that high constitutive miR-146a levels are induced by microenvironmental signals in the epidermis and might render LCs less susceptible to inappropriate activation by commensal bacterial TLR2 triggers at body surfaces.

Transcriptional pattern analysis of adrenergic immunoregulation in mice. Twelve hours norepinephrine treatment alters the expression of a set of genes involved in monocyte activation and leukocyte trafficking

We investigated in vivo effects of norepinephrine (NE) on the transcription of 200 immunologically relevant genes in the mouse. Balb/c mice were s.c. implanted with NE containing retard tablets. Twelve hours later, splenic mRNA was prepared and hybridized onto cDNA microarrays containing the sequences of the major cytokines, their receptors and all CD-antigens of the mouse. Consistent results were obtained with a set of five genes: in the NE-treated animals four genes (CXCR4, VCAM1, IL-1R2, CD 14) were found 2-8 fold upregulated as compared to sham treated animals, whereas the gene for CCR3 was downregulated (< 0.5 fold). The findings were confirmed using quantitative reverse transcriptase Real Time PCR. These first results prove the usefulness of gene microarray technology towards transcription pattern analysis in neuroimmune interactions. Furthermore, they support the relevance of catecholamines in the regulation of leukocyte migration and the inflammatory response.