Impaired counterregulatory response of glucagon to hypoglycemia is a common complication of type 1 diabetes (T1D). One proposed contributor to abnormal glucagon secretion is decreased sympathetic innervation in T1D islets. To systematically assess the innervation of human pancreatic tissues, we examined samples from donors with recent-onset T1D (<10 years, age 13-45 years, n = 4), longstanding T1D (>10 years, age 27-63 years, n = 3), and nondiabetic controls (age 10-52 years, n = 4). Islet and exocrine tissue innervation was visualized by pan-neuronal marker tubulin β-3 and analyzed by a 2-D morphometry and 3-D rendering. By quantifying the nerve fiber length (1.9±0.4 nm/μm2) and density (646±94 fibers/mm2), we found that innervation in control human islets was nearly 20-fold less than previously reported in mouse islets. In contrast to mouse, human exocrine tissue was far more innervated than islets with fiber length of 6.8±0.4 nm/μm2(p<0.05), and density of 1336±50 fibers/mm2(p<0.05). The 3-D analysis showed that nerve fibers follow extracellular matrix (ECM) formed around acini and from there, they extend further into islets along the ECM made by islet vasculature. Although T1D islets were primarily composed of α cells, the islet area was similar to controls (control: 15.7±1.5 mm2, recent-onset T1D: 16.5±1.4 mm2, long-standing T1D: 15.3±1.5 mm2; p>0.05), and so was the 3-D arrangement of nerve fibers in exocrine tissue and islets. Regardless of T1D duration, the islet fiber length (recent-onset: 1.5±0.2 nm/μm2; long-standing: 1.0±0.2 nm/μm2) and density (recent-onset: 623±61 fibers/mm2; longstanding: 486±49 fibers/mm2), as well as exocrine fiber length (recent-onset: 5.2±.5 nm/μm2; longstanding: 5.8±0.4 nm/μm2) and density (recent-onset: 1119±77 fibers/mm2; longstanding: 1537±72 fibers/mm2) did not differ from controls (p>0.05). These data indicate that neuronal patterning of human pancreas is significantly different from that of mouse and islet innervation does not appear to be altered in T1D.
T.M. Richardson: None. R. Haliyur: None. R. Aramandla: None. R. Bottino: Research Support; Self; Imagine Pharma. A.C. Powers: None. M. Brissova: None.