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Advances in tissue labeling and clearing methods include improvement of tissue transparency, better preservation of fluorescence signal, compatibility with immunostaining and large sample volumes. However, as existing methods share the common limitation that they can only be applied to human tissue slices, rendering intact human organs transparent remains a challenge. Here, we describe experimental details of the small-micelle-mediated human organ efficient clearing and labeling (SHANEL) pipeline, which can be applied for cellular mapping of intact human organs. We have successfully cleared multiple human organs, including kidney, pancreas, heart, lung, spleen and brain, as well as hard tissue like skull. We also describe an advanced volumetric imaging system using a commercial light-sheet fluorescence microscope that can accommodate most human organs and a pipeline for whole-organ imaging and visualization. The complete experimental process of labeling and clearing whole human organs takes months and the analysis process takes several weeks, depending on the organ types and sizes. This protocol describes labeling, clearing, imaging and cellular-level three-dimensional image reconstruction of intact human organs achieved with the help of a novel tissue clearing and labeling technology and a commercially available microscope.

Stress urinary incontinence presents a condition not only found in female elderlies, but also in young athletes participating in high-impact sports such as volleyball or trampolining. Repeated jumps appear to be a predisposing factor. Yet the pathophysiology remains incompletely elucidated to date; especially with regard to the influence of the surrounding buttock tissues including gluteus maximus. The present study assessed the morpho-mechanical link between gluteus maximus and the pelvic floor female bodies. 25 pelves obtained from Thiel embalmed females were studied in a supine position. Strands of tissues connecting gluteus maximus with the pelvic floor obtained from 20 sides were assessed mechanically. Plastinates were evaluated to verify the dissection findings. In total, 49 hemipelves were included for data acquisition. The fascia of gluteus maximus yielded connections to the subcutaneous tissues, the fascia of the external anal sphincter and that of obturator internus and to the fascia of the urogenital diaphragm. The connection between gluteus maximus and the urogenital diaphragm withstood an average force of 23.6 ± 17.3 N. Cramér φ analyses demonstrated that the connections of the fasciae connecting gluteus maximus with its surroundings were consistent in the horizontal and sagittal planes, respectively. In conclusion, gluteus maximus is morphologically densely linked to the pelvic floor via strands of connective tissues investing the adjacent muscles. Though gluteus maximus has also been reported to facilitate urinary continence, the here presented morpho-mechanical link suggests that it may also have the potential to contribute to urinary stress incontinence. Future research combining clinical imaging with in-situ testing may help substantiate the potential influence from a clinical perspective.

Analysis of entire transparent rodent bodies after clearing could provide holistic biological information in health and disease, but reliable imaging and quantification of fluorescent protein signals deep inside the tissues has remained a challenge. Here, we developed vDISCO, a pressure-driven, nanobody-based whole-body immunolabeling technology to enhance the signal of fluorescent proteins by up to two orders of magnitude. This allowed us to image and quantify subcellular details through bones, skin and highly autofluorescent tissues of intact transparent mice. For the first time, we visualized whole-body neuronal projections in adult mice. We assessed CNS trauma effects in the whole body and found degeneration of peripheral nerve terminals in the torso. Furthermore, vDISCO revealed short vascular connections between skull marrow and brain meninges, which were filled with immune cells upon stroke. Thus, our new approach enables unbiased comprehensive studies of the interactions between the nervous system and the rest of the body.

Background: The pancreas develops from two independent buds that fuse to form the adult organ. Ontogeny has largely been neglected in pancreatic surgery. This study aims to demonstrate that the adult pancreas can still be divided into morphogenetic units based on its embryological compartments and connective tissue borders for potential therapeutic purposes. Methods: Ten donor bodies (four female, six male, aged 73–101 years) were used. Manual dissection, guided by the common bile duct to locate the embryological fusion plane, was performed to divide the pancreatic tissue. Immunohistochemical staining for pancreatic polypeptide differentiated the pancreatic tissue by embryological origin and was used to quantify dissection accuracy. Results: Landmark-guided dissection successfully separated the pancreas along a connective tissue plane in seven cases. The resulting compartments were distinctly divided along the dissection plane into an area rich in pancreatic polypeptide and an area with low accumulation. Two cases showed deviations from the dissection plane at the histological level. One case contained tumor tissue, interfering with the utilization of landmarks. Conclusions: Landmark-guided dissection of the pancreas based on its embryological fusion plane allows for reliable separation into morphogenetic compartments. Immunohistochemical staining for pancreatic polypeptide effectively differentiates tissue origins. This approach may enable more precise, differentiated pancreatic resections and tailored treatments, with potential for refinement in routine surgical practice. Approaching the pancreatic tissue with regard to its ontogenetic origin and its clearly distinguishable compartments might even enable tailored treatment beyond refined surgical procedures.

Background Malrotation of the bowel due to imperfect embryologic development is a rare condition with a wide spectrum of resulting anatomical variations. Similar conditions are achieved in the adult by derotating the bowel via the Cattell-Braasch maneuver. However, possible preparational bias might compromise the resulting topography. Case presentation We present a case of atypical malrotation of the bowel in a cadaver study using a 96-year-old Caucasian male specimen with incidental finding of the pathology post mortem with no known surgical intervention in the abdomen during his lifetime. We compare the topography and abdominal layers with the anatomy of a 98-year-old Caucasian female specimen where the Cattell-Braasch maneuver was used to revert the embryologic development. Conclusions Reverting the embryologic development in the adult via Cattell-Braasch maneuver enables to mirror inherent malrotation and reestablishes the position of the bowel prior to its rotation. The Cattell-Braasch maneuver is further validated in this study by showing that it is able to demonstrate essential layers for surgical interventions without damaging their integrity. Atypical malrotation unmasks those fascial border-like layers, which are often hidden due to adhesions and fusing of tissue during the usual embryologic development. Developmental defects present a chance to explore essential surgical layers that are otherwise masked by artifacts due to fusion of layers of connective tissue.

PurposeTo investigate the innervation pattern of the sacroiliac region, especially with regard to the sacroiliac joint (SIJ). Dorsal SIJ innervation was analyzed and described. Our main hypothesis was that nerves reach the SIJ dorsally, passing ligamental compartments, as this would explain dorsal SIJ pain.MethodsTo examine sacroiliac innervation, we followed the nerves in over 50 specimens over several years. Plastinated slices were evaluated, nerves in the region were stained histologically, and the data were summarized as 3D models.ResultsThe Rami communicans and posterior branches of the spinal nerves and their branches that form a dorsal sacral plexus and communicating branches, together with corresponding vessels, were observed to form neurovascular bundles embedded by tiny fatty connectives in gaps and tunnels. Branches of L5-S1 pass the inner sacroiliac ligaments (the interosseous sacroiliac ligament and axial interosseous ligament). The outer sacroiliac ligaments (posterior sacroiliac ligaments, long posterior sacroiliac ligament, sacrotuberal ligament, thoracolumbar fascia) are passed by the S1-S4 branches. However, although the paths of these nerves are in the direction of the SIJ, they do not reach it. It is possible that impingement of the neurovascular bundles may result in pain. Moreover, the gaps and tunnels connect to the open dorsal SIJ.ConclusionOur findings suggest that Bogduk’s term “sacroiliac pain” correlates to “sacroiliac innervation”, which consists of “inner-” and “outer sacroiliac ligament innervation”, and to ventral “SIJ pain”. The watery gaps and tunnels observed could play a significant role in innervation and thus in the origins of SIJ pain.Level of evidenceIndividual cross-sectional studies with consistently applied reference standard and blinding.

PurposeIntraforaminal ligaments (IFL) are of great interest to anatomists and clinicians to fully understand the detailed anatomy of the neuroforamina and to diagnose unclear radicular symptoms. Studies published until now have described radiological imaging of the IFLs using magnetic resonance imaging (MRI) on donor bodies. In the present study, we investigated the detectability of lumbar IFLs in vivo in adults using the high spatial resolution of the constructive interference in steady state (CISS) sequence.MethodsA total of 14 patients were studied using a 1.5 T MRI scanner. The lumbar spine was imaged using the parasagittal CISS sequence, and the detectability of the IFLs was assessed for each lumbar level. All image datasets were analyzed by a radiologist, an orthopedic surgeon, and an anatomist. Interrater reliability was expressed as Fleiss’ Kappa. Using a single data set, a three-dimensional (3D) model was created to map the location of the IFLs within the intervertebral foramen (IF) and the immediate surrounding vessels.ResultsOverall, the radiologist was able to detect IFLs in 60% of all imaged IFs, the orthopedic surgeon in 62%, and the anatomist in 66%. Fleiss’ Kappa for the various segments varies from 0.71 for L4/5 up to 0.90 for L3/4.ConclusionLumbar IFLs were successfully detected in vivo in every patient. The detection frequency varied from 42–86% per IF. We demonstrated reproducible imaging of the IFLs on MRI, with good interrater reliability. The present study was a launching point for further clinical studies investigating the potential impact of altered IFLs on radicular pain.

The ability of muscle to generate force depends on its architecture and health condition. MR-based diffusion tensor imaging of muscle (mDTI) is an innovative approach for showing the fiber arrangement for the whole muscle volume. For accurate calculations of fiber metrics, muscle segmentation prior to tractography is regarded as necessary. Since segmentation is known to be operator dependent, it is important to understand how segmentation affects tractography. The aim of this study was to compare the results of deterministic fiber tracking based on muscle models generated by two independent operators. In addition, this study compares the results with a segmentation-free approach. Fifteen subjects underwent mDTI of the right shoulder. The results showed that mDTI can be successfully applied to complex joints such as the human shoulder. Furthermore, operator segmentation did not influence the results of fiber tracking and fascicle length (FL), fiber volume (FV), fractional anisotropy (FA), axial diffusivity (AD), radial diffusivity (RD), and mean diffusivity (MD) showed excellent intraclass correlation estimates (≥ 0.975). As an exploratory approach, the segmentation-free fiber tracking showed significant differences in terms of mean fascicle length. Based on these findings, we conclude that tractography is not sensitive to small deviations in muscle segmentation. Furthermore, it implies that mDTI and automatic segmentation approaches or even a segmentation-free analysis can be considered for evaluation of muscle architecture.

The osseo-ligamentous lumbopelvic complex is essential for musculoskeletal load transfer, yet location-specific material data and standardized test protocols remain scarce, which is a hindrance for comparability. Based on 91 specimen locations per cadaver (five cadavers, average age: 77.3 years), we developed detailed methods for specimen preparation and mechanical testing (bending, tensile, and compression) with defined boundary conditions. Multiple measurements were taken to assess repeatability. The proposed methods allow us to identify location-specific properties of the lumbopelvic system for the first time. Cortical bone exhibited an elastic modulus of 1750 MPa and an ultimate strength of 28.2 MPa, while those of trabecular bone were 32.7 MPa and 1.26 MPa, and soft tissues revealed values of 148 MPa and 14.3 MPa for fascial tissue and 103 MPa with 10.7 MPa for ligamentous tissue, respectively. The quantified properties for cortical and trabecular bone and soft tissues not only enhance the comparability of material properties but also support more accurate numerical simulations and implant design. Furthermore, the ease of implementation and standardization of these methods enable their widespread application, as well as the accumulation of a broad database and the setting of benchmarks for future investigations.

The ligaments in coherence with the capsule of the hip joint are known to contribute to hip stability. Nevertheless, the contribution of the mechanical properties of the ligaments and gender- or side-specific differences are still not completely clear. To date, comparisons of the hip capsule ligaments to other tissues stabilizing the pelvis and hip joint, e.g. the iliotibial tract, were not performed. Hip capsule ligaments were obtained from 17 human cadavers (9 females, 7 males, 13 left and 8 right sides, mean age 83.65 ± 10.54 years). 18 iliofemoral, 9 ischiofemoral and 17 pubofemoral ligaments were prepared. Uniaxial stress-strain properties were obtained from the load-deformation curves before the secant elastic modulus was computed. Strain, elastic modulus and cross sections were compared. Strain and elastic modulus revealed no significant differences between the iliofemoral (strain 129.8 ± 11.1%, elastic modulus 48.8 ± 21.4 N/mm2), ischiofemoral (strain 128.7 ± 13.7%, elastic modulus 37.5 ± 20.4 N/mm2) and pubofemoral (strain 133.2 ± 23.7%, elastic modulus 49.0 ± 32.1 N/mm2) ligaments. The iliofemoral ligament (53.5 ± 15.1 mm2) yielded a significantly higher cross section compared to the ischiofemoral (19.2 ± 13.2 mm2) and pubofemoral (15.2 ± 7.2 mm2) ligament. No significant gender- or side-specific differences were determined. A comparison to the published data on the iliotibial tract revealed lower elasticity and less variation in the ligaments of the hip joint. Comparison of the mechanical data of the hip joint ligaments indicates that their role may likely exceed a function as a mechanical stabilizer. Uniaxial testing of interwoven collagen fibers might lead to a misinterpretation of the mechanical properties of the hip capsule ligaments in the given setup, concealing its uniaxial properties. This underlines the need for a polyaxial test setup using fresh and non-embalmed tissues.