Background: During the development of different mouse liver resection models for the study of hepatic regeneration and basic liver pathology a significant lack of relevant anatomical data of the mouse liver became obvious. It has been shown, however, that different mouse liver lobes exhibit different regenerative capacities (less for the caudate lobe). In order to create a mouse model with standardized resections allowing a meaningful study of adaptive and regenerative responses the following basic anatomical studies of the mouse liver were undertaken.
Methods: In Balb/c mice (n=32, 18-26g) and Black 6 transgenic blue mice (n=69, 19-27g) liver mass and individual liver lobe weights were determined. The detailed three-dimensional anatomy of the hepatic vascular system was studied with corrosion casts (n=8). For scanning electron microscopy (EM) the mouse liver was perfused with a Mercox solution. Casts were sputtered with gold (10 nm) and examined in a Philips XL 30 FEG scanning electron microscope.
Results: When comparing liver weight (LW)/ bodyweight (BW) ratio significant strain specific differences were detected. In Balb/c mice liver weight (LW) was increasing up to a mouse body weight (BW) of 23.6g ± 1.6gr and decreasing thereafter (LW (g) = -0.0022*BW [g]2 + 0.1025*BW [g]).). In contrast the LW in the Black 6 transgenic mice showed a linear increase with increasing BW. In Balb/c mice vascular corrosion casts demonstrated a single vascular pedicle in the right superior, right inferior and caudate lobes. In contrast, a common pedicle was seen for medial and left lobes in 26%, explaining the necrosis of the left lobe after medial lobe resection in around 30% of cases.In Balb/c mice histological sections vascular density, total vascular luminal area and calculated volumes of liver lobules were not different between liver lobes. EM showed significantly smaller hepatic lobules in the cudate lobe (when compared with the right superior lobe) with significantly increased vascular density.
Conclusions: Relative mouse liver mass varies considerably with bodyweight and strain. A common vascular pedicle of the medial and left lobe in Balb/c mice explains the inhomogeneous perfusion of the liver remnant after some isolated medial lobe resections. This resection is therefore not recommended. A higher vascular density in the caudate lobe with smaller hepatic lobules as seen in EM might explain the impaired hepatic regenerative capacity. Our anatomical data underline the importance of careful selection of the appropriate microsurgical model when studying mechanisms of liver regeneration and basic liver pathologies.