Severe depletion of intraepidermal nerve fibers in skin biopsies of pancreas transplant recipients

Abstract

Background: The minimally invasive method of skin biopsy with intraepidermal nerve fiber (IENF) counts may be used to analyze nerve regeneration in pancreas transplant (PTx) recipients. We assessed IENF counts as a database for long-term follow-up of diabetic neuropathy.

Methods: Skin biopsies were performed using a 3-mm punch from lower thigh and upper calf areas of 16 (13 pancreas/kidney, 3 pancreas alone) PTx patients (mean +/- SD: age, 45+/-8 years; type 1 diabetes duration, 27 +/- 8 years) at 1 month posttransplant. Ten healthy gender- and age-matched controls (C) were also examined. After fixation and freezing, 40-microm sections were stained using rabbit polyclonal antibody to the panaxonal marker PGP 9.5 followed by mouse antirabbit IgG antibody conjugated with rhodamine. Samples were imaged with a digital camera, mounted on a microscope, and equipped for fluorescence. The average number of IENF per millimeter length of epidermis was derived. Clinical neuropathy was assessed by foot vibration perception thresholds (VPT) with a biothesiometer (normal values < mean + 2 SD of C).

Results: Significantly lower IENF densities were found in skin biopsies from PTx (PTx vs C: thigh, 0.74 +/- 0.88 vs 9.74 +/- 2.41 IENF/mm; calf, 0.34 +/- 0.91 vs 7.66 +/- 3.16 IENF/mm; P < .001). IENF were totally absent from the thigh and calf samples of 7 and 12 PTxs, respectively. Clinical neuropathy (VPT > 21 V) was present in all but one PTx.

Conclusions: Severe intraepidermal nerve fiber depletion is present in the lower limb area of pancreas transplant recipients with neuropathy. Long-term follow-up would probably be necessary to assess the possibility of posttransplant nerve fiber regeneration.