Laparoscopic hepatectomy in cirrhotics: safe if you adjust technique.

BACKGROUND: Minimally invasive liver surgery is a growing field, and a small number of recent reports have suggested that laparoscopic liver resection (LLR) is feasible even in patients with cirrhosis. However, parenchymal transection of the cirrhotic liver is challenging due to fibrosis and portal hypertension. There is a paucity of data regarding the technical modifications necessary to safely transect the diseased parenchyma. METHODS: Patients undergoing LLR by a single surgeon between 2008 and 2015 were reviewed. Patients with cirrhosis were compared to those without cirrhosis to examine differences in surgical technique, intraoperative characteristics, and outcomes (including liver-related morbidity and general postoperative complication rates). RESULTS: A total of 167 patients underwent LLR during the study period. Forty-eight (29 %) had cirrhosis, of which 43 (90 %) had hepatitis C. Most had Child-Pugh class A disease (85 %). Compared to noncirrhotics, patients with cirrhosis were older, had more comorbidities, and were more likely to have hepatocellular carcinoma. Precoagulation before parenchymal transection was used more frequently in cirrhotics (65 vs. 15 %, P < 0.001), and mean portal triad clamping time was longer (32 vs. 22 min, P = 0.002). There were few conversions to open surgery, though hand-assisted laparoscopy was used as an alternative to converting to open in three patients with cirrhosis. Blood loss was relatively low for both groups. Although there were more postoperative complications among cirrhotics (38 vs. 13 %, P = 0.001), this was almost entirely due to a higher rate of minor (Clavien-Dindo I or II) complications. Liver-related morbidity, major complications, and mortality rates were similar. CONCLUSIONS: LLR is safe for selected patients with cirrhosis. The added complexity associated with the division of diseased liver parenchyma may be overcome with some form of technique modification, including more liberal use of precoagulation, portal triad clamping, or a hand-assist port.

The promotion of a constructive macrophage phenotype by solubilized extracellular matrix.

The regenerative healing response of injured skeletal muscle is dependent upon a heterogeneous population of responding macrophages, which show a phenotypic transition from the pro-inflammatory M1 to the alternatively activated and constructive M2 phenotype. Biologic scaffolds derived from mammalian extracellular matrix (ECM) have been used for the repair and reconstruction of a variety of tissues, including skeletal muscle, and have been associated with an M2 phenotype and a constructive and functional tissue response. The mechanism(s) behind in-vivo macrophage phenotype transition in skeletal muscle and the enhanced M2:M1 ratio associated with ECM bioscaffold use in-vivo are only partially understood. The present study shows that degradation products from ECM bioscaffolds promote alternatively activated and constructive M2 macrophage polarization in-vitro, which in turn facilitates migration and myogenesis of skeletal muscle progenitor cells.

Hydrogels derived from central nervous system extracellular matrix.

Biologic scaffolds composed of extracellular matrix (ECM) are commonly used repair devices in preclinical and clinical settings; however the use of these scaffolds for peripheral and central nervous system (CNS) repair has been limited. Biologic scaffolds developed from brain and spinal cord tissue have recently been described, yet the conformation of the harvested ECM limits therapeutic utility. An injectable CNS-ECM derived hydrogel capable of in vivo polymerization and conformation to irregular lesion geometries may aid in tissue reconstruction efforts following complex neurologic trauma. The objectives of the present study were to develop hydrogel forms of brain and spinal cord ECM and compare the resulting biochemical composition, mechanical properties, and neurotrophic potential of a brain derived cell line to a non-CNS-ECM hydrogel, urinary bladder matrix. Results showed distinct differences between compositions of brain ECM, spinal cord ECM, and urinary bladder matrix. The rheologic modulus of spinal cord ECM hydrogel was greater than that of brain ECM and urinary bladder matrix. All ECMs increased the number of cells expressing neurites, but only brain ECM increased neurite length, suggesting a possible tissue-specific effect. All hydrogels promoted three-dimensional uni- or bi-polar neurite outgrowth following 7 days in culture. These results suggest that CNS-ECM hydrogels may provide supportive scaffolding to promote in vivo axonal repair.

A murine model of volumetric muscle loss and a regenerative medicine approach for tissue replacement.

Volumetric muscle loss (VML) resulting from traumatic accidents, tumor ablation, or degenerative disease is associated with limited treatment options and high morbidity. The lack of a reliable and reproducible animal model of VML has hindered the development of effective therapeutic strategies. The present study describes a critical-sized excisional defect within the mouse quadriceps muscle that results in an irrecoverable volumetric defect. This model of VML was used to evaluate the efficacy of a surgically placed inductive biologic scaffold material composed of porcine small intestinal submucosa-extracellular matrix (SIS-ECM). The targeted placement of an SIS-ECM scaffold within the defect was associated with constructive tissue remodeling including the formation of site-appropriate skeletal muscle tissue. The present study provides a reproducible animal model with which to study VML and shows the therapeutic potential of a bioscaffold-based regenerative medicine approach to VML.

Partial characterization of the Sox2+ cell population in an adult murine model of digit amputation.

Tissue regeneration in response to injury in adult mammals is generally limited to select tissues. Nonmammalian species such as newts and axolotls undergo regeneration of complex tissues such as limbs and digits via recruitment and accumulation of local and circulating multipotent progenitors preprogrammed to recapitulate the missing tissue. Directed recruitment and activation of progenitor cells at a site of injury in adult mammals may alter the default wound-healing response from scar tissue toward regeneration. Bioactive molecules derived from proteolytic degradation of extracellular matrix (ECM) proteins have been shown to recruit a variety of progenitor cells in vitro and in vivo to the site of injury. The present study further characterized the population of cells accumulating at the site of injury after treatment with ECM degradation products in a well-established model of murine digit amputation. After a mid-second phalanx digit amputation in 6-8-week-old adult mice, treatment with ECM degradation products resulted in the accumulation of a heterogeneous population of cells, a subset of which expressed the transcription factor Sox2, a marker of pluripotent and adult progenitor cells. Sox2+ cells were localized lateral to the amputated P2 bone and coexpressed progenitor cell markers CD90 and Sca1. Transgenic Sox2 eGFP/+ and bone marrow chimeric mice showed that the bone marrow and blood circulation did not contribute to the Sox2+ cell population. The present study showed that, in addition to circulating progenitor cells, resident tissue-derived cells also populate at the site of injury after treatment with ECM degradation products. Although future work is necessary to determine the contribution of Sox2+ cells to functional tissue at the site of injury, recruitment and/or activation of local tissue-derived cells may be a viable approach to tissue engineering of more complex tissues in adult mammals.

The effect of source animal age upon the in vivo remodeling characteristics of an extracellular matrix scaffold.

Biologic scaffolds composed of mammalian extracellular matrix (ECM) are routinely used for the repair and reconstruction of injured or missing tissues in a variety of pre-clinical and clinical applications. However, the structural and functional outcomes have varied considerably. An important variable of xenogeneic biologic scaffolds is the age of the animal from which the ECM is derived. The present study compared the in vivo host response and remodeling outcomes of biologic scaffolds composed of small intestinal submucosa (SIS)-ECM harvested from pigs that differed only in age. Results showed that there are distinct differences in the remodeling characteristics as a consequence of source animal age. Scaffolds derived from younger animals were associated with a more constructive, site appropriate, tissue remodeling response than scaffolds derived from older animals. Furthermore, the constructive remodeling response was associated with a dominant M2 macrophage response.

Recruitment of progenitor cells by an extracellular matrix cryptic peptide in a mouse model of digit amputation.

Biologic scaffolds composed of extracellular matrix (ECM) have been used successfully in preclinical models and humans for constructive remodeling of functional, site-appropriate tissue after injury. The mechanisms underlying ECM-mediated constructive remodeling are not completely understood, but scaffold degradation and site-directed recruitment of both differentiated and progenitor cells are thought to play critical roles. Previous studies have shown that degradation products of ECM scaffolds can recruit a population of progenitor cells both in vitro and in vivo. The present study identified a single cryptic peptide derived from the α subunit of the collagen III molecule that is chemotactic for a well-characterized perivascular stem cell in vitro and causes the site-directed accumulation of progenitor cells in vivo. The oligopeptide was additionally chemotactic for human cortical neural stem cells, rat adipocyte stem cells, C2C12 myoblast cells, and rat Schwann cells in vitro. In an adult murine model of digit amputation, treatment with this peptide after mid-second phalanx amputation resulted in a greater number of Sox2+ and Sca1+,Lin- cells at the site of injury compared to controls. Since progenitor cell activation and recruitment are key prerequisites for epimorphic regeneration in adult mammalian tissues, endogenous site-directed recruitment of such cells has the potential to alter the default wound healing response from scar tissue toward regeneration.

An isolated cryptic peptide influences osteogenesis and bone remodeling in an adult mammalian model of digit amputation.

Biologic scaffolds composed of extracellular matrix (ECM) have been used successfully in preclinical models and humans for constructive remodeling of functional, site-appropriate tissue after injury. The mechanisms underlying ECM-mediated constructive remodeling are not completely understood, but scaffold degradation and site-directed recruitment of progenitor cells are thought to play critical roles. Previous studies have identified a cryptic peptide derived from the C-terminal telopeptide of collagen IIIα that has chemotactic activity for progenitor cells. The present study characterized the osteogenic activity of the same peptide in vitro and in vivo in an adult murine model of digit amputation. The present study showed that the cryptic peptide increased calcium deposition, alkaline phosphatase activity, and osteogenic gene expression in human perivascular stem cells in vitro. Treatment with the cryptic peptide in a murine model of mid-second phalanx digit amputation led to the formation of a bone nodule at the site of amputation. In addition to potential therapeutic implications for the treatment of bone injuries and facilitation of reconstructive surgical procedures, cryptic peptides with the ability to alter stem cell recruitment and differentiation at a site of injury may serve as powerful new tools for influencing stem cell fate in the local injury microenvironment.