Faculty Bibliography

There is constant remodeling in a cirrhotic liver resulting in cirrhosis being spatially heterogeneous. The Laennec system, and, more recently the Beijing classification, have been used to sub-classify various degrees of cirrhosis. It is unknown how these two schemes compare with each other, how they are impacted by geographic variation, and how they correlate with clinical outcomes. Five needle biopsies were obtained from 20 explanted cirrhotic HCV livers at the time of transplantation. Collagen proportionate area (CPA) was measured by computerized quantitative morphometry. The Laennec system (4A-4C indicating increasing degrees of cirrhosis) and Beijing classification (P-progressive, R-regressive, I-indeterminate) were assessed and then correlated with CPA. Geographical variation using CPAs was calculated by the coefficient of variation (CoV). CPA of Laennec 4C cirrhosis was higher than 4A (p = 0.00008) or 4B (p = 0.0002). The CPA of the P pattern was greater than the R (p = 0.002) or I patterns (p = 0.037). The mean CoV of the five CPAs was 47.3 ± 4.5%, suggesting a significant degree of geographic variation. There was 100% overlap between the Beijing R pattern and Laennec 4A, and 80% overlap between the P pattern and Laennec 4C. Patients' platelet counts of P pattern were lower than R pattern (p = 0.008) or I pattern (p = 0.024), while Laennec 4C was lower than 4A (p = 0.036) and 4B patients (p = 0.7). There was no correlation between CPA, Laennec stage, or Beijing classification and MELD score, liver weights, total bilirubin, or albumin levels. The Laennec system and the Beijing classification are highly correlated with CPA in cirrhosis. This study confirms that there is a significant degree of geographic variation in terms of fibrosis content and cirrhosis morphology throughout the liver.

PURPOSE/OBJECTIVE:To determine whether histotripsy can create human-scale transcostal ablations in porcine liver without causing severe thermal wall injuries along the beam path. MATERIALS AND METHODS/METHODS:Histotripsy was applied to the liver using a preclinical prototype robotic system through a transcostal window in six female swine. A 3.0 cm spherical ablation zone was prescribed. Duration of treatment (75 min) was longer than a prior subcostal treatment study (24 min, 15 s) to minimize beam path heating. Animals then underwent contrast-enhanced MRI, necropsy, and histopathology. Images and tissue were analyzed for ablation zone size, shape, completeness of necrosis, and off-target effects. RESULTS:). Edema was noted in the body wall overlying the ablation on T2 MRI in 5/5 (one animal did not receive MRI), though there was no gross or histologic evidence of injury to the chest wall at necropsy. At gross inspection, lung discoloration in the right lower lobe was present in 5/6 animals (mean size: 1 × 2 × 4 cm) with alveolar hemorrhage, preservation of blood vessels and bronchioles, and minor injuries to pneumocytes noted at histology. CONCLUSION/CONCLUSIONS:Transcostal hepatic histotripsy ablation appears feasible, effective, and no severe injuries were identified in an acute porcine model when prolonged cooling time is added to minimize body wall heating.

The transition from pluripotent to somatic states marks a critical event in mammalian development, but remains largely unresolved. Here we report the identification of SS18 as a regulator for pluripotent to somatic transition or PST by CRISPR-based whole genome screens. Mechanistically, SS18 forms microscopic condensates in nuclei through a C-terminal intrinsically disordered region (IDR) rich in tyrosine, which, once mutated, no longer form condensates nor rescue SS18^-/- defect in PST. Yet, the IDR alone is not sufficient to rescue the defect even though it can form condensates indistinguishable from the wild type protein. We further show that its N-terminal 70aa is required for PST by interacting with the Brg/Brahma-associated factor (BAF) complex, and remains functional even swapped onto unrelated IDRs or even an artificial 24 tyrosine polypeptide. Finally, we show that SS18 mediates BAF assembly through phase separation to regulate PST. These studies suggest that SS18 plays a role in the pluripotent to somatic interface and undergoes liquid-liquid phase separation through a unique tyrosine-based mechanism.

INTRODUCTION:This study was performed to determine the feasibility and safety of creating superficial histotripsy treatment in a live porcine thyroid model. METHODS:The porcine thymus comparable in size, shape and location to the human thyroid was used for this study. This model has been used for thyroid surgery studies due to the diminutive size of the porcine thyroid. Four female swine underwent a total of eight histotripsy treatments performed with a prototype therapy system (HistoSonics, Inc., Ann Arbor, MI). Two treatments were performed in each animal: a spherical 1.0 × 1.0 × 1.0 cm and ovoid 1.0 × 1.0 × 2.0 cm treatment zones. MRI immediately post-procedure was evaluated for histotripsy treatment zone size and imaging appearance, followed immediately by sacrifice. Tissue was then reviewed for percent cellular destruction and precision. RESULTS: > 0.05 vs. prescribed). MRI demonstrated well demarcated treatment zones and imaging findings consistent with cellular destruction. Histology demonstrated sharp transitions to normal tissue (mean 0.33 (+/- 0.13) cm), and high degrees of cellular destruction (mean 76% (+/- 12.5), range of 50-100%) in the treated tissue. Edema within the overlying muscle was seen in 2/8 treatments. CONCLUSION:Histotripsy is capable of safely creating precise histotripsy treatments within the superficial neck of a porcine thyroid model without evidence of considerable complications.