Proteomics of Human Nerve Biopsies in Diabetic Neuropathy and After Nerve Injury Using Quantitative Mass Spectrometry of Posterior Interosseous, Sural and Digital Nerves

Department of Translational Medicine - Hand Surgery, Lund University, Malmö Sweden

C. Welinder, R. Perez, D. Frostadottir

Proteomic analysis of human peripheral nerve biopsies in neuropathy and after nerve injury, focusing on degeneration and regeneration as well as to time after injury, remains an underexplored research area. These studies investigate molecular patterns in various human nerve biopsies from subjects with diabetic neuropathy as well as in subjects with a digital nerve injury, analyzing short-term proteomic differences between proximal and distal nerve ends in the latter. Quantitative mass spectrometry was employed to analyze protein composition in posterior interosseous nerves in subjects without and with type 1 and type 2 diabetes, as well as in proximal and distal nerve ends of 26 injured digital nerves: latter within 48 hours after injury in connection with nerve repair. A mass spectrometry method was developed for uninjured human sural nerves, enabling analysis of up to 2619 proteins in nerve specimens weighing ≥1.2 mg, using RIPA buffer in combination with 8M Urea and a Bullet Blender. In subjects with type 1 diabetes, in which a shift to smaller myelinated diameter nerve fibers was seen, indicating degeneration and regeneration, a tendency for increased protein intensity of Heat Shock Proteins (like HSP27) was observed among approximately 2500 identified proteins. In injured digital nerves, a total of 3914 proteins were identified, with 127 proteins showing abundance differences between proximal and distal nerve ends within the first 48 hrs. Downregulated proteins in distal nerve end were associated with synaptic transmission, autophagy, neurotransmitter regulation, cell adhesion and migration. Conversely, proteins upregulated in the distal nerve end were implicated in cellular stress response, neuromuscular junction stability and muscle contraction, neuronal excitability and neurotransmitter release, synaptic vesicle recycling and axon guidance and angiogenesis. Proteomic analysis of small nerve biopsies can reveal dynamic cellular responses in neuropathy in diabetes and after nerve injury in humans.