The exaggerated flux through polyol pathway during diabetes is thought to be a major cause of lesions in the peripheral nerves. Here, we used aldose reductase (

Progressive loss of pain perception and cutaneous nerve fibers are frequently observed in diabetic patients. We evaluated the feasibility of using thy1-YFP mice that express the yellowish-green fluorescent protein (YFP) in all of their sensory/motor neurons for noninvasive monitoring of cutaneous nerve fiber loss during diabetes. Fluorescent fibers in skin sections from the leg of thy1-YFP mice stained positive for the neuron-specific protein gene product 9.5 (PGP9.5), indicating that the cutaneous fluorescent fibers are indeed nerve fibers. In diabetic thy1-YFP mice, significant small cutaneous nerve fiber loss in the leg was observed at 3 months following the onset of diabetes, but loss of heat-induced pain perception occurred as early as 1 month following the onset of diabetes, indicating that functional impairment of sensory nerves precedes cutaneous nerve fiber loss. Immunostaining of skin sections of mice killed at 6 months following the onset of diabetes showed that parallel to the loss of small fluorescent nerve fibers, there was a significant decrease in fibers stained positive for calcitonin gene-related peptide, substance P, and purinoreceptor subtype in diabetic thy1-YFP mice. These mice will be useful for noninvasive monitoring of cutaneous nerve fiber degeneration and loss of heat-induced pain perception during diabetes and for the assessment of efficacy of therapeutic treatment of diabetic neuropathy. Diabetes 54: [3112][3113][3114][3115][3116][3117][3118] 2005 N europathy is one of the most common and debilitating complications in diabetic patients. Peripheral sensory and motor nerve fibers, as well as autonomic nerve fibers, are affected (1). Lesions in the cutaneous sensory fibers may lead to hyperalgesia or hypoalgesia, depending on the stage or the severity of the disease. Hypoalgesia renders patients unaware of the wounds on their lower limbs and, together with impaired wound healing, often causes foot ulceration and gangrene, which may require amputation. There is evidence that the cutaneous nerve might be involved in wound healing as well. Impaired wound healing in diabetic mice was found to be associated with a reduced level of nerve growth factor at the wound site, presumably due to a reduced number of epidermal nerve fibers (2); nerve growth factor has been shown to accelerate wound healing (3,4). In addition to nerve growth factor, the cutaneous nerve may secrete other neurotransmitters and neuromodulators, including catecholamines, acetylcholine, substance P, calcitonin gene-related peptide (CGRP), ␣-melanocyte-stimulating hormone, and other agents (5). Some of these neuromodulators are known to regulate immune and inflammatory reactions (5). Thus, lesions in the cutaneous nerves contribute to lack of awareness to injuries, impaired wound healing, and impairment in skin immune defense, all key factors contributing to diabetic foot ulceration. Diabetic neuropathy is the leading cause of lower-limb amputation, underscoring the importance of monitoring the integrity of the cutaneous n...

The neural and glial cells of the intrinsic ganglia of the enteric nervous system (ENS) are derived from the hindbrain neural crest at the vagal level. The Hoxb3 gene is expressed in the vagal neural crest and in the enteric ganglia of the developing gut during embryogenesis. We have identified a cis-acting enhancer element b3IIIa in the Hoxb3 gene locus. In this study, by transgenic mice analysis, we examined the tissue specificity of the b3IIIa enhancer element using the lacZ reporter gene, with emphasis on the vagal neural crest cells and their derivatives in the developing gut. We found that the b3IIIa-lacZ transgene marks only the vagal region and not the trunk or sacral region. Using cellular markers, we showed that the b3IIIa-lacZ transgene was expressed in a subset of enteric neuroblasts during early development of the gut, and the expression was maintained in differentiated neurons of the myenteric plexus at later stages. The specificity of the b3IIIa enhancer in directing gene expression in the developing ENS was further supported by genetic analysis using the Dom mutant, a spontaneous mouse model of Hirschsprung's disease characterized by the absence of enteric ganglia in the distal gut. The colonization of lacZ-expressing cells in the large intestine was incomplete in all the Dom/b3IIIa-lacZ hybrid mutants we examined. To our knowledge, this is the only vagal neural crest-specific genetic regulatory element identified to date. This element could be used for a variety of genetic manipulations and in establishing transgenic mouse models for studying the development of the ENS. Developmental Dynamics 233:473-483, 2005.