Exploring human splenic red pulp vasculature in virtual reality: details of sheathed capillaries and the open capillary network

Abstract

We reconstructed serial sections of a representative adult human spleen to clarify the unknown arrangement of the splenic microvasculature, such as terminal arterioles, sheathed capillaries, the red pulp capillary network and venules. The resulting 3D model was evaluated in virtual reality (VR). Capillary sheaths often occurred after the second or third branching of a terminal arteriole and covered its capillary side or end branches. The sheaths started directly after the final smooth muscle cells of the arteriole and consisted of cuboidal CD271++ stromal sheath cells surrounded and infiltrated by B lymphocytes and macrophages. Some sheaths covered up to four sequential capillary bifurcations thus forming bizarre elongated structures. Each sheath had a unique form. Apart from symmetric dichotomous branchings inside the sheath, sheathed capillaries also gave off side branches, which crossed the sheath and freely ended at its surface. These side branches are likely to distribute materials from the incoming blood to sheath-associated B lymphocytes and macrophages and thus represent the first location for recognition of blood-borne antigens in the spleen. A few non-sheathed bypasses from terminal arterioles to the red pulp capillary network also exist. Red pulp venules are primarily supplied by sinuses, but they also exhibit a few connections to the capillary network. Thus, the human splenic red pulp harbors a primarily open microcirculation with a very minor closed part.

In focus in HCB

“…In previous investigations, Steiniger and colleagues (2007Steiniger and colleagues ( , 2014Steiniger and colleagues ( , 2018 have established the cellular phenotype as well as the location and form of capillary sheaths in 3D. In their present study (Steiniger et al 2021), they used multiple labeling immunohistochemistry to detect smooth muscle α-actin, endothelial Fig. 1 Localization of myosin VI in mouse developing spermatids during the Golgi and cap phases (From Zakrzewski et al 2021) cells with anti-CD34, resident sheath cells with anti-CD271, and B lymphocytes with anti-CD20 (Fig.…”

Inspection of Histological 3D Reconstructions in Virtual Reality

“…For QC, the original data is simultaneously displayed with the reconstruction. User annotations and mesh painting facilitate VA. With our application, novel research results concerning the microanatomy of human spleens became viable for the first time; our findings have been established and published in a series of papers (Steiniger et al, 2018a(Steiniger et al, ,b, 2021.…”

“…While it is possible to trace a single entity through a series, gaining a full 3D perception is impossible without a full-fledged 3D reconstruction. An inspection of our reconstructions in VR (Steiniger et al, 2018a(Steiniger et al, ,b, 2021 was much faster than a typical inspection of 3D data without VR (Steiniger et al, 2016), as section 6 details.…”

“…The healing of damaged regions (Lobachev, 2020) is an optional step. The step "mesh coloring" involves, e. g., coloring of selected components (Steiniger et al, 2018a(Steiniger et al, ,b, 2021 or visualization of shape diameter function (Steiniger et al, 2016). QC is used as initial visual analytics.…”

“…Figure 2 documents a QC session from "outside." The presented method has been extensively used in microanatomical research (Lobachev, 2018;Steiniger et al, 2018aSteiniger et al, ,b, 2021Lobachev et al, 2019).…”