Malawer type I/V proximal humerus reconstruction after tumor resection: a systematic review.

BACKGROUND: Several reconstruction methods exist for Malawer type I/V proximal humerus reconstruction after bone tumor resection; however, no consensus has been reached regarding the preferred methods. METHODS: We conducted a literature search on various types of proximal humerus oncologic reconstruction methods. We collected data on postoperative functional outcomes assessed based on Musculoskeletal Tumor Society (MSTS) scores, 5-year reconstruction survival rates, and complications. We calculated each reconstruction's weighted mean based on the sample size and standard errors. Complications were categorized based on the Henderson classification. Based on these integrated data, our primary objective is to propose an optimal strategy for proximal humerus reconstruction after bone tumor resection. RESULTS: We examined various reconstruction techniques, including modular prosthesis (752 patients in 21 articles), osteoarticular allograft (142 patients in six articles), allograft prosthesis composites (236 patients in 12 articles), reverse shoulder total arthroplasty (141 patients in 10 articles), composite reverse shoulder total arthroplasty (33 patients in four articles), claviculo-pro-humero technique (51 patients in six articles), and cement spacer (207 patients in four articles). Weighted mean MSTS scores were: modular prosthesis (73.8%), osteoarticular allograft (74.4%), allograft prosthesis composites (79.2%), reverse shoulder total arthroplasty (77.0%), composite reverse shoulder total arthroplasty (76.1%), claviculo-pro-humero technique (75.1%), and cement spacer (69.1%). Weighted 5-year reconstruction survival rates were modular prosthesis (85.4%), osteoarticular allograft (67.6%), allograft prosthesis composites (85.2%), reverse shoulder total arthroplasty (84.1%), and cement spacer (88.0%). Reconstruction survival data was unavailable for composite reverse shoulder total arthroplasty and claviculo-pro-humero technique. Major complications included shoulder joint instability: modular prosthesis (26.2%), osteoarticular allograft (41.5%), allograft prosthesis composites (33.9%), reverse shoulder total arthroplasty (17%), composite reverse shoulder total arthroplasty (6.1%), claviculo-pro-humero technique (2.0%), and cement spacer (8.7%). Aseptic loosening of the prosthesis occurred: modular prosthesis (3.9%) and reverse shoulder total arthroplasty (5.7%). Allograft fracture was observed in 54.9% of patients with osteoarticular allograft. CONCLUSION: The complication profiles differed among reconstruction methods. Weighted mean MSTS scores exceeded 70% in all methods except cement spacer, and the 5-year reconstruction survival rate surpassed 80% for all methods except osteoarticular allograft. Proximal humerus reconstruction after bone tumor resection should consider potential complications and patients' individual factors.

Outcomes of Window Therapy with Carboplatin and Ifosfamide for Pediatric Osteosarcoma: A Case Series.

For the treatment of osteosarcoma, cisplatin (CDDP) can be substituted by carboplatin (CBDCA) to reduce toxicity. We report a single institution experience of CBDCA-based regimen. Two to three cycles of CBDCA + ifosfamide (IFO) therapy (window therapy) were administered as neoadjuvant therapy for osteosarcoma. Depending on the response of window therapy, the subsequent protocols were determined; for good responders, surgery is performed, and postoperative therapies with CBDCA + IFO, adriamycin (ADM) and high-dose methotrexate (MTX) were administered; for stable disease, the postoperative regimens were advanced before surgery, and the remaining amount of postoperative chemotherapy is deduced; for progressive disease, CBDCA-based regimen is changed to CDDP-based regimen. From 2009 to 2019, seven patients were treated with this protocol. During the window therapy, two patients (28.6%) were assessed as good responders and completed the regimen as planned. Four patients (57.1%) had stable disease, and the chemotherapy schedules were modified. One patient (14.2%) with progressive disease was shifted to the CDDP-based regimen. At final follow-up, four patients showed no evidence of disease and three patients died of the disease. Since the efficacy during window therapy was limited, a CBDCA-based regimen in the neoadjuvant setting was considered insufficient for performing adequate surgery.

Bone Metastases from Gastric Cancer Resembling Paget's Disease: A Case Report.

Systemic osteosclerotic lesions are frequently caused by multiple bone metastases or systemic metabolic disorders. However, bone metastasis from gastric cancer is rare. Herein, we describe such a case, with radiographic and clinical findings resembling Paget's disease. The patient was an 80-year-old Japanese woman with a history of early gastric cancer, treated by partial gastrectomy 2 years prior. The patient sought medical care for chronic low back pain. On imaging, systemic sclerotic lesions were observed throughout the spine and pelvis, with an increase in bone mineral density from 0.86 g/cm3 (2 years prior) to 1.38g/cm3 (current visit) in the lumbar spine. Elevated serum levels of osteoblastic and osteolytic markers were identified. A bone biopsy was used to confirm the diagnosis of metastatic gastric cancer. The patient was treated with TS-1 and denosumab, with normalization of abnormal metabolic markers and alleviation of the back pain. Bone metastasis is reported in only 10% of cases of gastric cancer and, thus, is relatively rare. Therefore, our case of gastric cancer recurrence presenting with mixed osteoblastic and osteolytic bone lesions similar to Paget's disease is relevant to the report. Bone biopsy is necessary for an accurate diagnosis.

Effect of Neoadjuvant Therapies on Soft Tissue Sarcomas with Tail-like Lesions: A Multicenter Retrospective Study.

Several types of soft tissue sarcomas have peripheral infiltrative growth characteristics called tail-like lesions. The efficacy of neoadjuvant therapy for tumors with tail-like lesions has not been elucidated. From 2012 to 2019, we analyzed 36 patients with soft tissue sarcoma with tail-like lesions treated with neoadjuvant therapy, including chemotherapy, radiotherapy, or both. The effect of neoadjuvant therapy on the tail sign was investigated by analyzing the change in tail-like lesions during neoadjuvant therapy and histological responses. The median length of the tail-like lesion reduced from 29.5 mm at initiation to 19.5 mm after neoadjuvant therapy. The extent of shrinkage in tail-like lesions was related to the histopathological responses in the main part of the tumor. Complete disappearance of the tail-like lesion was observed in 12 patients; however, it was not related to achieving a microscopically negative margin. The oncologic outcomes did not significantly differ between cases with and without the complete disappearance of tail-like lesions. This study indicated that the shrinkage of tail-like lesions did not have a significant effect on complete resection or improvements of clinical outcomes. A more comprehensive evaluation is needed to elaborate on the surgical strategy.

Different patterns of pneumothorax in patients with soft tissue tumors treated with pazopanib: A case series analysis.

To investigate pneumothorax patterns in pazopanib treatment by focusing on the positional relationship between the visceral pleura and metastatic lung tumor, we examined 20 patients with advanced soft tissue tumors who developed lung metastases and underwent pazopanib treatment between 2012 and 2019. Pneumothorax was classified into two types based on the location of the metastatic lesion around the visceral pleural area before pazopanib treatment: subpleural type, within 5 mm from the pleura; and central type, >5 mm from the pleura. We investigated the rates of pneumothorax and the associated risk factors. Five patients experienced pneumothorax (three subpleural and two central types). Cavitation preceded pneumothorax in 83% of patients and led to connection of the cavitated cyst of the metastatic lesion to the chest cavity in the shorter term in patients with the subpleural type. Conversely, a more gradual increase in the cavity size and sudden cyst rupture were observed in the central type. The risk factors for pneumothorax were cavitation after initiating pazopanib and intervention before pazopanib, either ablation or surgery. The location of the metastatic lesions was not a risk factor for the occurrence of pneumothorax. In conclusion, pneumothorax is an adverse event associated with pazopanib treatment. Therefore, attention must be paid to predisposing factors such as the formation of cavitation after pazopanib initiation and previous interventions to the lungs. Moreover, because subpleural pneumothorax tends to occur earlier than the central type, a different time course can be anticipated based on the positional relationships of the metastatic lesions to the visceral pleura.

Myelolipoma mimicking osteosarcoma in the distal femur.

INTRODUCTION AND IMPORTANCE: Periosteal reactions indicate malignant bone tumors, including osteosarcoma; establishing an accurate diagnosis is key to determining the most appropriate treatment strategy. We describe a rare case of myelolipoma in the distal femur metaphysis with massive extraskeletal lesions and periosteal reactions. CASE PRESENTATION: A 25-year-old woman was referred to our hospital to treat a gradually expanding mass around her knee that grew to the size of a baby's head. She had a history of hydrocephalus caused by congenital cytomegalovirus infection and was bedridden for life. Radiography showed a prominent osteoblastic rim and osteolytic lesion with a moth-eaten appearance. Osteosarcoma was suspected due to excessive extraskeletal invasion and periosteal reactions. T1- and T2-weighted magnetic resonance images showed a high-signal-intensity homologous lesion. Biopsy specimens contained adipose and hematopoietic tissues. A myelolipoma was diagnosed. Due to her fragility, surgical intervention was suspended. Two years after diagnosis, the tumor size did not change. CLINICAL DISCUSSION: Myelolipomas are benign tumors that typically arise from the adrenal gland and rarely develop in the extremities. This type of tumor typically does not cause any tumor-related symptoms or endocrine disturbances and has been reported as a type of incidentaloma. To effectively manage myelolipoma patients, differential diagnosis of tumors mimicking malignant bone tumors is important. CONCLUSION: We successfully managed a destructive ectopic myelolipoma in the distal femoral metaphysis, with massive extraskeletal lesions and periosteal reactions. Clinicians should appropriately differentiate myelolipoma from tumors mimicking malignant bone tumors.

Ocular findings in Japanese patients with hydroxychloroquine retinopathy developing within 3 years of treatment.

PURPOSE: To describe the characteristics of Japanese patients with hydroxychloroquine (HCQ) retinopathy developing within 3 years of treatment outset. STUDY DESIGN: Retrospective case series METHODS: Three patients with HCQ retinopathy developing within 3 years of treatment outset have been identified in Japan since HCQ became available in 2015. Their medical charts, containing optical coherence tomography (OCT), fundus autofluorescence imaging, and visual field tests, were reviewed. RESULTS: The treatment durations and cumulative doses until onset were 29-36 months and 182-326 g, respectively. The first patient had possible pre-existing maculopathy, although the abnormalities were ambiguous. The second and third patients had impaired renal function. The patients did not complain of severe visual disturbance at diagnosis, but visual field loss and disruption of the outer retinal segments consisting of a parafoveal pattern in the first case and a pericentral pattern (localized, 8 or more degrees from the center of the fovea) in the second and third cases were clearly observed on OCT. Even after HCQ discontinuation, their retinopathy showed slight progression on the visual field tests and OCT images. A blood sample was obtained from 1 patient on the day after HCQ discontinuation, and the whole blood level of HCQ was measured using validated liquid chromatography-tandem mass spectrometry. The HCQ level 27 h after the last dose was high, at 2240 ng/mL (suggested threshold > 1733 ng/mL). CONCLUSION: Ophthalmologic screening from the initiation of HCQ treatment detected 3 cases of HCQ retinopathy developing within 3 years of treatment outset, including a patient with a high blood level of HCQ.

The dipeptide prolyl-hydroxyproline promotes cellular homeostasis and lamellipodia-driven motility via active ß1-integrin in adult tendon cells.

Collagen-derived hydroxyproline (Hyp)-containing peptides have a variety of biological effects on cells. These bioactive collagen peptides are locally generated by the degradation of endogenous collagen in response to injury. However, no comprehensive study has yet explored the functional links between Hyp-containing peptides and cellular behavior. Here, we show that the dipeptide prolyl-4-hydroxyproline (Pro-Hyp) exhibits pronounced effects on mouse tendon cells. Pro-Hyp promotes differentiation/maturation of tendon cells with modulation of lineage-specific factors and induces significant chemotactic activity in vitro. In addition, Pro-Hyp has profound effects on cell proliferation, with significantly upregulated extracellular signal-regulated kinase phosphorylation and extracellular matrix production and increased type I collagen network organization. Using proteomics, we have predicted molecular transport, cellular assembly and organization, and cellular movement as potential linked-network pathways that could be altered in response to Pro-Hyp. Mechanistically, cells treated with Pro-Hyp demonstrate increased directional persistence and significantly increased directed motility and migration velocity. They are accompanied by elongated lamellipodial protrusions with increased levels of active ß1-integrin-containing focal contacts, as well as reorganization of thicker peripheral F-actin fibrils. Pro-Hyp-mediated chemotactic activity is significantly reduced (p < 0.001) in cells treated with the mitogen-activated protein kinase kinase 1/2 inhibitor PD98059 or the α5ß1-integrin antagonist ATN-161. Furthermore, ATN-161 significantly inhibits uptake of Pro-Hyp into adult tenocytes. Thus, our findings document the molecular basis of the functional benefits of the Pro-Hyp dipeptide in cellular behavior. These dynamic properties of collagen-derived Pro-Hyp dipeptide could lead the way to its application in translational medicine.

Conditional targeting in mice reveals that hepatic homogentisate 1,2-dioxygenase activity is essential in reducing circulating homogentisic acid and for effective therapy in the genetic disease alkaptonuria.

Alkaptonuria is an inherited disease caused by homogentisate 1,2-dioxygenase (HGD) deficiency. Circulating homogentisic acid (HGA) is elevated and deposits in connective tissues as ochronotic pigment. In this study, we aimed to define developmental and adult HGD tissue expression and determine the location and amount of gene activity required to lower circulating HGA and rescue the alkaptonuria phenotype. We generated an alkaptonuria mouse model using a knockout-first design for the disruption of the HGD gene. Hgd tm1a -/- mice showed elevated HGA and ochronosis in adulthood. LacZ staining driven by the endogenous HGD promoter was localised to only liver parenchymal cells and kidney proximal tubules in adulthood, commencing at E12.5 and E15.5 respectively. Following removal of the gene trap cassette to obtain a normal mouse with a floxed 6th HGD exon, a double transgenic was then created with Mx1-Cre which conditionally deleted HGD in liver in a dose dependent manner. 20% of HGD mRNA remaining in liver did not rescue the disease, suggesting that we need more than 20% of liver HGD to correct the disease in gene therapy. Kidney HGD activity which remained intact reduced urinary HGA, most likely by increased absorption, but did not reduce plasma HGA nor did it prevent ochronosis. In addition, downstream metabolites of exogenous 13C6-HGA, were detected in heterozygous plasma, revealing that hepatocytes take up and metabolise HGA. This novel alkaptonuria mouse model demonstrated the importance of targeting liver for therapeutic intervention, supported by our observation that hepatocytes take up and metabolise HGA.

Roles of fibronectin isoforms in neonatal vascular development and matrix integrity.

Fibronectin (FN) exists in two forms-plasma FN (pFN) and cellular FN (cFN). Although the role of FN in embryonic blood vessel development is well established, its function and the contribution of individual isoforms in early postnatal vascular development are poorly understood. Here, we employed a tamoxifen-dependent cFN inducible knockout (cFN iKO) mouse model to study the consequences of postnatal cFN deletion in smooth muscle cells (SMCs), the major cell type in the vascular wall. Deletion of cFN influences collagen deposition but does not affect life span. Unexpectedly, pFN translocated to the aortic wall in the cFN iKO and in control mice, possibly rescuing the loss of cFN. Postnatal pFN deletion did not show a histological aortic phenotype. Double knockout (dKO) mice lacking both, cFN in SMCs and pFN, resulted in postnatal lethality. These data demonstrate a safeguard role of pFN in vascular stability and the dispensability of the individual FN isoforms in postnatal vascular development. Complete absence of FNs in the dKOs resulted in a disorganized tunica media of the aortic wall. Matrix analysis revealed common and differential roles of the FN isoforms in guiding the assembly/deposition of elastogenic extracellular matrix (ECM) proteins in the aortic wall. In addition, we determined with two cell culture models that that the two FN isoforms acted similarly in supporting matrix formation with a greater contribution from cFN. Together, these data show that pFN exerts a critical role in safeguarding vascular organization and health, and that the two FN isoforms function in an overlapping as well as distinct manner to maintain postnatal vascular matrix integrity.

Transcription factor scleraxis vitally contributes to progenitor lineage direction in wound healing of adult tendon in mice.

Tendon is a dense connective tissue that transmits high mechanical forces from skeletal muscle to bone. The transcription factor scleraxis (Scx) is a highly specific marker of both precursor and mature tendon cells (tenocytes). Mice lacking scx exhibit a specific and virtually complete loss of tendons during development. However, the functional contribution of Scx to wound healing in adult tendon has not yet been fully characterized. Here, using ScxGFP-tracking and loss-of-function systems, we show in an adult mouse model of Achilles tendon injury that paratenon cells, representing a stem cell antigen-1 (Sca-1)-positive and Scx-negative progenitor subpopulation, display Scx induction, migrate to the wound site, and produce extracellular matrix (ECM) to bridge the defect, whereas resident tenocytes exhibit a delayed response. Scx induction in the progenitors is initiated by transforming growth factor ß (TGF-ß) signaling. scx-deficient mice had migration of Sca-1-positive progenitor cell to the lesion site but impaired ECM assembly to bridge the defect. Mechanistically, scx-null progenitors displayed higher chondrogenic potential with up-regulation of SRY-box 9 (Sox9) coactivator PPAR-γ coactivator-1α (PGC-1α) in vitro, and knock-in analysis revealed that forced expression of full-length scx significantly inhibited Sox9 expression. Accordingly, scx-null wounds formed cartilage-like tissues that developed ectopic ossification. Our findings indicate a critical role of Scx in a progenitor-cell lineage in wound healing of adult mouse tendon. These progenitor cells could represent targets in strategies to facilitate tendon repair. We propose that this lineage-regulatory mechanism in tissue progenitors could apply to a broader set of tissues or biological systems in the body.

Micrometer scale guidance of mesenchymal stem cells to form structurally oriented large-scale tissue engineered cartilage.

Current clinical methods to treat articular cartilage lesions provide temporary relief of the symptoms but fail to permanently restore the damaged tissue. Tissue engineering, using mesenchymal stem cells (MSCs) combined with scaffolds and bioactive factors, is viewed as a promising method for repairing cartilage injuries. However, current tissue engineered constructs display inferior mechanical properties compared to native articular cartilage, which could be attributed to the lack of structural organization of the extracellular matrix (ECM) of these engineered constructs in comparison to the highly oriented structure of articular cartilage ECM. We previously showed that we can guide MSCs undergoing chondrogenesis to align using microscale guidance channels on the surface of a two-dimensional (2-D) collagen scaffold, which resulted in the deposition of aligned ECM within the channels and enhanced mechanical properties of the constructs. In this study, we developed a technique to roll 2-D collagen scaffolds containing MSCs within guidance channels in order to produce a large-scale, three-dimensional (3-D) tissue engineered cartilage constructs with enhanced mechanical properties compared to current constructs. After rolling the MSC-scaffold constructs into a 3-D cylindrical structure, the constructs were cultured for 21days under chondrogenic culture conditions. The microstructure architecture and mechanical properties of the constructs were evaluated using imaging and compressive testing. Histology and immunohistochemistry of the constructs showed extensive glycosaminoglycan (GAG) and collagen type II deposition. Second harmonic generation imaging and Picrosirius red staining indicated alignment of neo-collagen fibers within the guidance channels of the constructs. Mechanical testing indicated that constructs containing the guidance channels displayed enhanced compressive properties compared to control constructs without these channels. In conclusion, using a novel roll-up method, we have developed large scale MSC based tissue-engineered cartilage that shows microscale structural organization and enhanced compressive properties compared to current tissue engineered constructs. STATEMENT OF SIGNIFICANCE: Tissue engineered cartilage constructs made with human mesenchymal stem cells (hMSCs), scaffolds and bioactive factors are a promising solution to treat cartilage defects. A major disadvantage of these constructs is their inferior mechanical properties compared to the native tissue, which is likely due to the lack of structural organization of the extracellular matrix of the engineered constructs. In this study, we developed three-dimensional (3-D) cartilage constructs from rectangular scaffold sheets containing hMSCs in micro-guidance channels and characterized their mechanical properties and metabolic requirements. The work led to a novel roll-up method to embed 2-D microscale structures in 3-D constructs. Further, micro-guidance channels incorporated within the 3-D cartilage constructs led to the production of aligned cell-produced matrix and enhanced mechanical function.

Molecular Cues Guiding Matrix Stiffness in Liver Fibrosis.

Tissue and matrix stiffness affect cell properties during morphogenesis, cell growth, differentiation, and migration and are altered in the tissue remodeling following injury and the pathological progression. However, detailed molecular mechanisms underlying alterations of stiffness in vivo are still poorly understood. Recent engineering technologies have developed powerful techniques to characterize the mechanical properties of cell and matrix at nanoscale levels. Extracellular matrix (ECM) influences mechanical tension and activation of pathogenic signaling during the development of chronic fibrotic diseases. In this short review, we will focus on the present knowledge of the mechanisms of how ECM stiffness is regulated during the development of liver fibrosis and the molecules involved in ECM stiffness as a potential therapeutic target for liver fibrosis.

Macrophage-secreted granulin supports pancreatic cancer metastasis by inducing liver fibrosis.

Pancreatic ductal adenocarcinoma (PDAC) is a devastating metastatic disease for which better therapies are urgently needed. Macrophages enhance metastasis in many cancer types; however, the role of macrophages in PDAC liver metastasis remains poorly understood. Here we found that PDAC liver metastasis critically depends on the early recruitment of granulin-secreting inflammatory monocytes to the liver. Mechanistically, we demonstrate that granulin secretion by metastasis-associated macrophages (MAMs) activates resident hepatic stellate cells (hStCs) into myofibroblasts that secrete periostin, resulting in a fibrotic microenvironment that sustains metastatic tumour growth. Disruption of MAM recruitment or genetic depletion of granulin reduced hStC activation and liver metastasis. Interestingly, we found that circulating monocytes and hepatic MAMs in PDAC patients express high levels of granulin. These findings suggest that recruitment of granulin-expressing inflammatory monocytes plays a key role in PDAC metastasis and may serve as a potential therapeutic target for PDAC liver metastasis.

Loss of fibulin-4 results in abnormal collagen fibril assembly in bone, caused by impaired lysyl oxidase processing and collagen cross-linking.

The extracellular matrix protein fibulin-4 has been shown to be indispensable for elastic fiber assembly, but there is also evidence from human mutations that it is involved in controlling skeletal development and bone stability. Fibulin-4 mutations were identified in patients suffering from vascular abnormality and/or cutis laxa, and some of these patients exhibited bone fragility, arachnodactyly and joint laxity. In order to elucidate the role of fibulin-4 in bone structure and skeletal development, we analyzed structural changes in skeletal tissues of Fbln4(-/-) mice. Immunostaining confirmed that fibulin-4 is highly expressed in cartilage, bone, ligaments and tendons. No morphological abnormalities were found in the skeleton of Fbln4(-/-) mice as compared to wild type littermates except forelimb contractures as well as unusually thick collagen fibrils. Furthermore, fibulin-4 deficiency caused enhanced susceptibility of bone collagen for acid extraction, consistent with significantly reduced lysylpyridinoline and hydroxylysylpyridinoline cross-links in bone. In accordance with that, the amount of lysyl oxidase in long bones and calvaria was strongly decreased and proteolytic activation of lysyl oxidase was reduced in fibulin-4 deficient osteoblasts, while addition of recombinant fibulin-4 rescued the activation. The finding suggested that fibulin-4 is important for the proteolytic activation of lysyl oxidase which has a pivotal role in cross-linking of collagen and elastin.

Molecular Mechanism Responsible for Fibronectin-controlled Alterations in Matrix Stiffness in Advanced Chronic Liver Fibrogenesis.

Fibrosis is characterized by extracellular matrix (ECM) remodeling and stiffening. However, the functional contribution of tissue stiffening to noncancer pathogenesis remains largely unknown. Fibronectin (Fn) is an ECM glycoprotein substantially expressed during tissue repair. Here we show in advanced chronic liver fibrogenesis using a mouse model lacking Fn that, unexpectedly, Fn-null livers lead to more extensive liver cirrhosis, which is accompanied by increased liver matrix stiffness and deteriorated hepatic functions. Furthermore, Fn-null livers exhibit more myofibroblast phenotypes and accumulate highly disorganized/diffuse collagenous ECM networks composed of thinner and significantly increased number of collagen fibrils during advanced chronic liver damage. Mechanistically, mutant livers show elevated local TGF-ß activity and lysyl oxidase expressions. A significant amount of active lysyl oxidase is released in Fn-null hepatic stellate cells in response to TGF-ß1 through canonical and noncanonical Smad such as PI3 kinase-mediated pathways. TGF-ß1-induced collagen fibril stiffness in Fn-null hepatic stellate cells is significantly higher compared with wild-type cells. Inhibition of lysyl oxidase significantly reduces collagen fibril stiffness, and treatment of Fn recovers collagen fibril stiffness to wild-type levels. Thus, our findings indicate an indispensable role for Fn in chronic liver fibrosis/cirrhosis in negatively regulating TGF-ß bioavailability, which in turn modulates ECM remodeling and stiffening and consequently preserves adult organ functions. Furthermore, this regulatory mechanism by Fn could be translated for a potential therapeutic target in a broader variety of chronic fibrotic diseases.

Three Huntington's Disease Specific Mutation-Carrying Human Embryonic Stem Cell Lines Have Stable Number of CAG Repeats upon In Vitro Differentiation into Cardiomyocytes.

Huntington disease (HD; OMIM 143100), a progressive neurodegenerative disorder, is caused by an expanded trinucleotide CAG (polyQ) motif in the HTT gene. Cardiovascular symptoms, often present in early stage HD patients, are, in general, ascribed to dysautonomia. However, cardio-specific expression of polyQ peptides caused pathological response in murine models, suggesting the presence of a nervous system-independent heart phenotype in HD patients. A positive correlation between the CAG repeat size and severity of symptoms observed in HD patients has also been observed in in vitro HD cellular models. Here, we test the suitability of human embryonic stem cell (hESC) lines carrying HD-specific mutation as in vitro models for understanding molecular mechanisms of cardiac pathology seen in HD patients. We have differentiated three HD-hESC lines into cardiomyocytes and investigated CAG stability up to 60 days after starting differentiation. To assess CAG stability in other tissues, the lines were also subjected to in vivo differentiation into teratomas for 10 weeks. Neither directed differentiation into cardiomyocytes in vitro nor in vivo differentiation into teratomas, rich in immature neuronal tissue, led to an increase in the number of CAG repeats. Although the CAG stability might be cell line-dependent, induced pluripotent stem cells generated from patients with larger numbers of CAG repeats could have an advantage as a research tool for understanding cardiac symptoms of HD patients.

A thyroid hormone receptor/KLF9 axis in human hepatocytes and pluripotent stem cells.

Biological processes require close cooperation of multiple transcription factors that integrate different signals. Thyroid hormone receptors (TRs) induce Krüppel-like factor 9 (KLF9) to regulate neurogenesis. Here, we show that triiodothyronine (T3) also works through TR to induce KLF9 in HepG2 liver cells, mouse liver, and mouse and human primary hepatocytes and sought to understand TR/KLF9 network function in the hepatocyte lineage and stem cells. Knockdown experiments reveal that KLF9 regulates hundreds of HepG2 target genes and modulates T3 response. Together, T3 and KLF9 target genes influence pathways implicated in stem cell self-renewal and differentiation, including Notch signaling, and we verify that T3 and KLF9 cooperate to regulate key Notch pathway genes and work independently to regulate others. T3 also induces KLF9 in human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSC) and this effect persists during differentiation to definitive endoderm and hiPSC-derived hepatocytes. Microarray analysis reveals that T3 regulates hundreds of hESC and hiPSC target genes that cluster into many of the same pathways implicated in TR and KLF9 regulation in HepG2 cells. KLF9 knockdown confirms that TR and KLF9 cooperate to regulate Notch pathway genes in hESC and hiPSC, albeit in a partly cell-specific manner. Broader analysis of T3 responsive hESC/hiPSC genes suggests that TRs regulate multiple early steps in ESC differentiation. We propose that TRs cooperate with KLF9 to regulate hepatocyte proliferation and differentiation and early stages of organogenesis and that TRs exert widespread and important influences on ESC biology.

Transforming growth factor-ß-independent role of connective tissue growth factor in the development of liver fibrosis.

We previously identified transforming growth factor (TGF)-ß signaling as a fibronectin-independent mechanism of type I collagen fibrillogenesis following adult liver injury. To address the contribution of TGF-ß signaling during the development of liver fibrosis, we generated adult mice lacking TGF-ß type II receptor (TGF-ßIIR) from the liver. TGF-ßIIR knockout livers indeed showed a dominant effect in reducing fibrosis, but fibrosis still remained approximately 45% compared with control and fibronectin knockout livers. Unexpectedly, this was accompanied by significant up-regulation of connective tissue growth factor mRNA levels. Organized type I collagen networks in TGF-ßIIR knockout livers colocalized well with fibronectin. We provide evidence that elimination of TGF-ßIIR is not sufficient to completely prevent liver fibrosis. Our results indicate a TGF-ß-independent mechanism of type I collagen production and suggest connective tissue growth factor as its potent mediator. We advocate combined elimination of TGF-ß signaling and connective tissue growth factor as a potential therapeutic target by which to attenuate liver fibrosis.