Extended Data Fig. 4: Histological analysis of the porcine small intestine after S-NeuroString implantation.

Representative hematoxylin-and-eosin-stained cross-sections of porcine small intestine, showing different section from each condition: control porcine jejunum and porcine jejunum implanted with S-NeuroString in the lumen for 7 days. No differences in cellularity and cellular composition were present in the lamina propria mucosae between the control and fiber-implanted segment from the different animal samples. There are no signs of lesions or inflammatory response, highlighting the importance of our soft technology for long term interfacing with the GI tissue. There was a focally accentuated goblet cell (enterocytes that secrete mucus in the lumen) hyperplasia and increased amounts of mucus within the intestinal crypts and the intestinal lumen of the fiber section as compared to the control sample (observed only in Pig 3 out of a total of 4 pigs). Depending on the sampling location and experimental surgical procedures, mural myodegeneration is most likely unrelated to the intraluminal fiber. Observed mesothelial hyperplasia can occur with intra-abdominal irritations, such as surgical manipulation – very common in abdominal surgeries. This observation was made on all samples, both controls and fiber-implanted segments. Desquamation of epithelial cells is present in all samples and interpreted as postmortem finding, a common degradation and separation of the epithelial cells from the mucosa of intestine that happens after death.