Characterization of interstitial Cajal progenitors cells and their changes in Hirschsprung's disease

Interstitial cells of Cajal (ICC) are critical to gastrointestinal motility. The phenotypes of ICC progenitors have been observed in the mouse gut, but whether they exist in the human colon and what abnormal changes in their quantity and ultrastructure are present in Hirschsprung’s disease (HSCR) colon remains uncertain. In this study, we collected the surgical resection of colons, both proximal and narrow segments, from HSCR patients and normal controls. First, we identified the progenitor of ICC in normal adult colon using immunofluorescent localization techniques with laser confocal microscopy. Next, the progenitors were sorted to observe their morphology. We further applied flow cytometry to examine the content of ICC progenitors in these fresh samples. The ultrastructural changes in the narrow and proximal parts of the HSCR colon were observed using transmission electron microscopy (TEM) and were compared with the normal adult colon. The presumed early progenitor (c-Kit^lowCD34⁺Igf1r⁺) and committed progenitor (c-Kit⁺CD34⁺Igf1r⁺) of ICC exist in adult normal colon as well as in the narrow and proximal parts of the HSCR colon. However, the proportions of mature, early and committed progenitors of ICC were dramatically reduced in the narrow segment of the HSCR colon. The proportions of mature and committed progenitors of ICC in the proximal segment of the HSCR colon were lower than in the adult normal colon. Ultrastructurally, ICC, enteric nerves, and smooth muscle in the narrow segment of the HSCR colon showed severe injury, including swollen vacuola or ted mitochondria, disappearance of mitochondrial cristae, dilated rough endoplasmic reticulum, vesiculation and degranulation, and disappearance of the caveolae on the ICC membrane surface. The contents of ICC and its progenitors in the narrow part of the HSCR colon were significantly decreased than those of adult colon, which may be associated with HSCR pathogenesis.

Tissue engineered esophagus by mesenchymal stem cell seeding for esophageal repair in a canine model

PURPOSE

Acellular porcine small intestinal submucosa (SIS) has been successfully used for esophagoplasty in dogs. However, this has not led to complete epithelialization and muscular regeneration. We undertook the present study to assess the effect of tissue-engineered esophagus generated by seeding bone marrow mesenchymal stem cells (BMSCs) onto an SIS scaffold (BMSCs-SIS) in a canine model.

METHODS

We cultured, passaged, and measured autologous BMSCs and myoblasts with cell proliferation and immunohistochemical assays. We labeled the third passage of BMSCs with PKH-26, a fluorescent dye, before seeded it onto the SIS. We resected canine cervical esophagus to generate a defect 5 cm in length and 50% in circumference, which we repaired with BMSCs-SIS or SIS alone.

RESULTS

Four weeks later, barium esophagram demonstrated that esophageal lumen surface of the patch graft was smoother in the BMSCs-SIS group compared with the SIS group. Histological examination suggested a strong similarity between BMSCs and esophageal myoblasts in terms of morphology and function. Although both BMSCs-SIS and SIS repaired the esophageal defects, we noted complete re-epithelialization with almost no inflammation only in the former group. By 12 wk after the surgery, we observed long bundles of skeletal muscles only in the BMSCs-SIS group, where the microvessel density was also much greater.

CONCLUSIONS

Bone marrow mesenchymal stem cells on an SIS scaffold can promote re-epithelialization, revascularization, and muscular regeneration. This approach may provide an attractive option for esophageal regeneration.

The arterial and cardiac epicardium in development, disease and repair

The importance of the epicardium covering the heart and the intrapericardial part of the great arteries has reached a new summit. It has evolved as a major cellular component with impact both in development, disease and more recently also repair potential. The role of the epicardium in development, its differentiation from a proepicardial organ at the venous pole (vPEO) and the differentiation capacities of the vPEO initiating cardiac epicardium (cEP) into epicardium derived cells (EPDCs) have been extensively described in recent reviews on growth and transcription factor pathways. In short, the epicardium is the source of the interstitial, the annulus fibrosus and the adventitial fibroblasts, and differentiates into the coronary arterial smooth muscle cells. Furthermore, EPDCs induce growth of the compact myocardium and differentiation of the Purkinje fibers. This review includes an arterial pole located PEO (aPEO) that provides the epicardium covering the intrapericardial great vessels. In avian and mouse models disturbance of epicardial outgrowth and maturation leads to a broad spectrum of cardiac anomalies with main focus on non-compaction of the myocardium, deficient annulus fibrosis, valve malformations and coronary artery abnormalities. The discovery that in disease both arterial and cardiac epicardium can again differentiate into EPDCs and thus reactivate its embryonic program and potential has highly broadened the scope of research interest. This reactivation is seen after myocardial infarction and also in aneurysm formation of the ascending aorta. Use of EPDCs for cell therapy show their positive function in paracrine mediated repair processes which can be additive when combined with the cardiac progenitor stem cells that probably share the same embryonic origin with EPDCs. Research into the many cell-autonomous and cell-cell-based capacities of the adult epicardium will open up new realistic therapeutic avenues.

[Comparison of myogenic differentiation ability of adipose-derived stem cells from different sites in rabbit]

OBJECTIVE

To compare the myogenic differentiation ability in vitro of rabbit adipose-derived stem cells (ADCSs) from different sites so as to provide ideal seed cells for repair and reconstruction of urinary tract.

METHODS

Adipose tissues were obtained from the nape of the neck, post peritoneum, and vicinity of epididymis of a 4-month-old male New Zealand rabbit and ADSCs were harvested through collagenase digestion. ADSCs were purified by differential attachment method. The protein marker CD44 of rabbit ADSCs was used to identify the stem cells by immunocytochemistry, then the 5th generation of ADSCs were induced to differentiate into adipogenic, osteogenic, and myogenic cells. Multi-differentiation was confirmed by Oil red O staining, von Kossa staining, and RT-PCR. Myogenic differentiation abilities of ADSCs from 3 different sites were compared between the control group (L-DMEM medium containing 10%FBS) and the experimental group (myogenic medium) by RT-PCR method.

RESULTS

ADSCs could be easily isolated from adipose tissues of the nape of the neck, post peritoneum, and vicinity of epididymis. ADSCs displayed a typical cobblestone morphology. Brown particles could be seen in ADSCs by CD44 immunocytochemistry staining. Oil red O staining showed red fat drops in ADSCs after 14 days of adipogenic culture. Black matrix could be seen in ADSCs by von Kossa staining after 28 days of osteogenic culture. RT-PCR detection showed moderate alpha-actin expression in the control group and strong alpha-actin expression in the experimental group after 42 days of myogenic culture. The growth rate of alpha-actin from the adipose tissue of post peritoneum (28.622% +/- 4.879%) was significantly lower (P < 0.05) than those from the adipose tissues of the nape of the neck (35.471% +/- 3.434%) and vicinity of epididymis (38.446% +/- 4.852%).

CONCLUSION

The ADSCs from different sites show different myogenic differentiation abilities in vitro. ADSCs from the adipose tissues of the nape of the neck and vicinity of epididymis can be used as ideal seed cells for tissue engineering of lower urinary tract.

[Effects of interferon-gamma on tubular epithelial-myofibroblast transdifferentiation in vitro]

OBJECTIVE

To investigate the effects of interferon-gamma (IFN-gamma) on tubular epithelial-myofibroblast transdifferentiation (TEMT) induced by transforming growth factor (TGF-beta1).

METHODS

The normal rat kidney tubular epithelial cells (NRK52E) were cultured and divided into blank (NRK52E cells only) control group, TGF-beta1 (3 ng/mL) treated group, IFN-gamma (1000 IU/mL) treated group, and IFN-gamma inhibition group (TGF-beta1 3 ng/mL + IFN-gamma 200, 400, 600, 1000, 2000, 3000 IU/mL). After 72 hours of treatment, the morphology of cells was observed under phase-contrast microscopy and scanning electron microscopy. The expressions of a-smooth muscle actin (alpha-SMA) and connective tissue growth factor (CTGF) were detected by immunocytochemistry. Flowcytometry was employed to measure the percentage of alpha-SMA+ cells and the mean channel fluorescence (MCF). The expressions of alpha-SMA mRNA and CTGF mRNA were examined by reverse transcription-polymerase chain reaction analyses (RT-PCR). The level of collagen in the culture supernatant was measured by Enzyme-linked immunoadsordent assay (ELISA).

RESULTS

NRK52E cells cultured in the control group showed a classic cobblestone morphology. TGF-beta1 induced NRK52E cells to transdifferentiate into myofibroblast-like cells, which showed strong alpha-SMA immunostaining. The TGF-beta1 treated cells had higher percentage of a-SMA+ cells, MCF and alpha-SMA mRNA, increased CTGF mRNA expression, and ascended collagen III than the blank controls (P<0.05). IFN-gamma treated alone did not make any changes to the cell morphology, the expressions of alpha-SMA mRNA and CTGF mRNA and the level of collagen III (P>0.05). IFN-gamma exerted a strong inhibitory effect on the TEMT induced by TGF-beta1. With the increase of IFN-gamma, the percentage of alpha-SMA+ cells, the level of collagen III, and the expressions of alpha-SMA mRNA and CTGF mRNA decreased (P<0.05).

CONCLUSION

IFN-gamma inhibits the TEMT induced by TGF-beta1 and reduces the level of collagen III.

Functional tissue-engineered blood vessels from bone marrow progenitor cells

OBJECTIVE

Stem cells have significant potential for development of cell-based therapeutics for cardiovascular tissue regeneration.

METHODS

We developed a novel method for isolating smooth muscle cells (SMC) from ovine bone marrow using a tissue-specific promoter and fluorescence-activated cell sorting.

RESULTS

As compared to vascular SMC, bone marrow-derived smooth muscle progenitor cells (BM-SMPC) exhibited similar morphology, showed higher proliferation potential and expressed several SMC markers including alpha-actin, calponin, myosin heavy chain, smoothelin, caldesmon and SM22. When embedded in fibrin hydrogels, BM-SMPC contracted the matrix and displayed receptor- and non-receptor-mediated contractility, indicating that BM-SMPC can generate force in response to vasoreactive agonists. We also prepared tissue-engineered blood vessels from BM-SMPC and BM-derived endothelial cells and implanted them into the jugular veins of lambs. As early as five weeks post-implantation, grafted tissues displayed a confluent endothelial layer overlaying the medial layer in which BM-SMPC were aligned circumferentially and synthesized significant amounts of collagen. In contrast to previous results with vascular SMC, BM-SMPC synthesized high amounts of elastin that was organized in a fibrillar network very similar to that of native vessels.

CONCLUSIONS

Our results suggest that BM-SMPC may be useful in studying SMC differentiation and have high potential for development of cell therapies for the treatment of cardiovascular disease.

Developmental basis of vascular smooth muscle diversity

The origins of vascular smooth muscle are far more diverse than previously thought. Lineage mapping studies show that the segmental organization of early vertebrate embryos leaves footprints on the adult vascular system in the form of a mosaic pattern of different smooth muscle types. Moreover, evolutionarily conserved tissue forming pathways produce vascular smooth muscle from a variety of unanticipated sources. A closer look at the diversity of smooth muscle origins in vascular development provides new perspectives about how blood vessels differ from one another and why they respond in disparate ways to common risk factors associated with vascular disease. The origins of vascular smooth muscle are far more diverse than previously thought. A closer look at the diversity of smooth muscle origins in vascular development provides new perspectives about how blood vessels differ from one another and why they respond in disparate ways to common risk factors associated with vascular disease.

Isoform-specific regulation of the actin-organizing protein palladin during TGF-beta1-induced myofibroblast differentiation

Contractile myofibroblasts are responsible for remodeling of extracellular matrix during wound healing; however, their continued activity results in various fibrocontractive diseases. Conversion of fibroblasts into myofibroblasts is induced by transforming growth factor-beta1 (TGF-beta1) and is hallmarked by the neo-expression of alpha-smooth muscle actin (alpha-SMA), a commonly used myofibroblast marker. Moreover, myofibroblast differentiation and acquisition of the contractile phenotype involves functionally important alterations in the expression of actin-organizing proteins. We investigated whether myofibroblast differentiation is accompanied by changes in the expression of palladin, a cytoskeletal protein that controls stress fiber integrity. Palladin is expressed as several isoforms, including major 3Ig (90 kDa) and 4Ig (140 kDa) forms that differ in their N-terminal sequence. Expression of the 4Ig isoform is strongly induced in fibroblast stress fibers upon TGF-beta1 treatment preceding alpha-SMA upregulation. TGF-beta1 induced upregulation of palladin is mediated both by Smad and mitogen-activated protein kinase pathways. Furthermore, palladin 4Ig-isoform is co-expressed with alpha-SMA in vivo in experimental rat wounds and in human myofibroblast-containing lesions. Taken together these results identify palladin 4Ig as a novel marker of myofibroblast conversion in vitro and in vivo. They also provide for the first time information about the signaling cascades involved in the regulation of palladin expression.

The common bile duct ligation in rat: A relevant in vivo model to study the role of mechanical stress on cell and matrix behaviour

Common bile duct ligation leads to bile accumulation and liver fibrosis. In this model, little attention has been dedicated to the modification of the common bile duct. We have studied by histochemistry and immunohistochemistry, 3 and 5 days after ligation, the connective tissue modifications of the common bile duct wall. After bile duct ligation, compared with normal bile duct, a strong increase of the bile duct diameter, due to bile stasis, and a thickness of the bile duct wall were observed; numerous myofibroblasts expressing alpha-smooth muscle actin appeared in parallel with the detection of many proliferating connective tissue cells. These myofibroblasts secreted very early high amount of elastic fibre components, elastin and fibrillin-1. Elastic fibre increase was also observed close to the epithelial cell layer. Procollagen type III deposition was also induced 3 days after ligation but decreased thereafter, underlining that myofibroblasts modify their synthesis of extracellular matrix components to comply with the request. We show here that common bile duct ligation represents an invaluable model to study myofibroblastic differentiation and extracellular matrix adaptation produced by an acute mechanical stress.

A Knitted, Fibrin-Covered Polycaprolactone Scaffold for Tissue Engineering of the Aortic Valve

State-of-the-art tissue engineered heart valves are not strong enough to withstand aortic blood pressure levels. When a strong and slowly degrading scaffold is used, the starting position of valvular tissue engineering is a stronger valve and seeded cells are allowed more time to create a strong extracellular matrix. A polycaprolactone knitted patch with leaflets was developed as a valvular scaffold. It was sutured into a tube and covered with fibrin gel. The opening and closing behavior and leakage of knitted scaffolds without cells were studied and compared to those of stentless porcine valves. An MTT test was performed on polycaprolactone and fibrin. A loading device was developed to study the durability of the knitted scaffold. The scaffold showed proper opening and it showed coaptation upon closing, but a 39 +/- 3% (n = 3) leakage, compared to a 8 +/- 1% (n = 3) leakage of tested porcine valves. MTT tests showed that polycaprolactone and fibrin are biocompatible materials. Durability testing of the knitted scaffold (n = 1) did not show rupture after ten million loading cycles. A tissue engineering process that includes cell culture will have to show whether this scaffold, besides mechanically reliable and biocompatible, is suitable to lead to a functional, nonregurgitant, durable aortic valve.

Nicotine inhibits myofibroblast differentiation in human gingival fibroblasts

Cigarette smoking has been suggested as a risk factor for several periodontal diseases. It has also been found that smokers respond less favorably than non-smokers to periodontal therapy. Previous work in our lab has shown that nicotine inhibits human gingival cell migration. Since myofibroblasts play an important role in wound closure, we asked if nicotine affects gingival wound healing process by regulating myofibroblast differentiation. Human gingival fibroblasts (HGFs) from two patients were cultured in 10% fetal bovine serum cell culture medium. Cells were pretreated with different doses of nicotine (0, 0.01, 0.1, and 1 mM) for 2 h, and then incubated with transforming growth factor beta (TGF-beta1) (0, 0.25, 0.5, and 1 ng/ml) with or without nicotine for 30 h. The expression level of alpha-smooth muscle actin (alpha-SMA), a specific marker for myofibroblasts, was analyzed by Western blots, immunocytochemistry, and real-time polymerase chain reaction (real-time PCR). Phosphorylated p38 mitogen-activated protein kinase (Phospho-p38 MAPK) activity was analyzed by Western blots. TGF-beta1 induced an increase of alpha-SMA protein and mRNA expression, while nicotine (1 mM) inhibited the TGF-beta1-induced expression of alpha-SMA but not beta-actin. Nicotine treatment down-regulated TGF-beta1-induced p38 MAPK phosphorylation. Our results demonstrated for the first time that nicotine inhibits myofibroblast differentiation in human gingival fibroblasts in vitro; supporting the hypothesis that delayed wound healing in smokers may be due to decreased wound contraction by myofibroblasts.

[Role of connective tissue growth factor in human renal tubular epithelial cell transdifferentiation in vitro]

OBJECTIVE

To observe the effect of connective tissue growth factor (CTGF) on the transdifferentiation of human renal tubular epithelial cells and to explore the influence of CTGF antisense oligodeoxynucleotide (ASODN) transfection on the transdifferentiation process induced by transforming growth factor-beta1 (TGF-beta1).

METHODS

Human renal tubular epithelial cells of the strain HKC were cultured and divided into 3 groups: (1) negative control group, (2) low dose CTGF group, treated with recombinant human CTGF (rhCTGF) with the terminal concentration of 2.5 microg/L, and (3) high dose CTGF group, treated with rhCTGF with the terminal concentration of 5.0 microg/L). To evaluate the contribution of CTGF to the transdifferentiation induced by TGF-beta1, Another HKC cells were divided into 4 groups: (1) untreated control group (Group C), (2) Group T, stimulated by TGF-beta1 (10.0 microg/L), (3) Group S, stimulated by sense ODN transfection + TGF-beta1 (10.0 microg/L), and (4) Group A, stimulated by antisense ODN transfection + TGF-beta1 (10.0 microg/L). RT-PCR was used to detect the mRNA expression of alpha-smooth muscle actin (alpha-SMA) and collagen type IV (col IV) mRNA. Indirect immunofluorescence assay and flow cytometry were used to assess the level of intracellular alpha-SMA protein. ELISA was used to determine the concentration of col IV in the media.

RESULTS

The normal HKC cells were round and the HKC cells stimulated with rhCTGF became elongated. Upon the stimulation of different concentrations of rhCTGF, the expression of alpha-SMA mRNA increased markedly (both P < 0.01), while the mRNA expression of collagen type IV gene was down-regulated significantly (both P < 0.01). The percentage of alpha-SMA positive cells was significantly higher in the stimulated groups than that in negative control with significant difference among any 2 groups (38.9%, 65.5% vs. 2.4% respectively, all P < 0.01). Under this condition, collagen type IV secreted into the culture medium was lowered markedly upon the induction of CTGF (P < 0.01). RT-PCR analysis showed that the CTGF gene expression was upregulated by TGF-beta1 stimulation and peaked in 3 hours, and the alpha-SMA expression was upregulated by TGF-beta1 stimulation, however, peaked in 6 hours. The CTGF mRNA expression of the HKC cells transfected with CTGF ASODN that was stimulated by TGF-beta1 10 microg/L was significantly suppressed (P < 0.01) and the alpha-SMA mRNA expression induced by TGF-beta1 10 microg/L was significantly inhibited by CTGF ASODN transfection (P < 0.01). Indirect immunofluorescence assay showed that normal HKC cells did not express alpha-SMA, 48 hours after stimulation of TGF-beta1 10 microg/L the HKC cells showed expression of alpha-SMA in the cytoplasm, and the intracytoplasmic alpha-SMA expression was significantly down-regulated by the transfection of CTGF ASODN (P < 0.01).

CONCLUSION

CTGF can promote the transdifferentiation of human renal tubular epithelial cells towards myofibroblast (MyoF) in vitro, and CTGF blockade results in a dramatic inhibition of TGF-beta-induced transdifferentiation of renal tubular cells. So CTGF may be a crucial factor in promoting tubular-epithelial myofibroblast transdifferentiation.

Fgf10expression identifies parabronchial smooth muscle cell progenitors and is required for their entry into the smooth muscle cell lineage

Lineage formation in the lung mesenchyme is poorly understood. Using a transgenic mouse line expressing LacZ under the control of Fgf10 regulatory sequences, we show that the pool of Fgf10-positive cells in the distal lung mesenchyme contains progenitors of the parabronchial smooth muscle cells. Fgf10 gene expression is slightly repressed in this transgenic line. This allowed us to create a hypomorphic Fgf10 phenotype by expressing the LacZtransgene in a heterozygous Fgf10 background. Hypomorphic Fgf10 mutant lungs display a decrease inβ-galactosidase-positive cells around the bronchial epithelium associated with an accumulation of β-galactosidase-expressing cells in the distal mesenchyme. This correlates with a marked reduction of α smooth muscle actin expression, thereby demonstrating that FGF10 is mostly required for the entry of mesenchymal cells into the parabronchial smooth muscle cell lineage. The failure of exogenous FGF10 to phosphorylate its known downstream targets ERK and AKT in lung mesenchymal cultures strongly suggests that FGF10 acts indirectly on the progenitor population via an epithelial intermediate. We provide support for a role of epithelial BMP4 in mediating the formation of parabronchial smooth muscle cells.

Myogenesis during holothurian intestinal regeneration

Echinoderms are well known as being able to regenerate body parts and thus provide excellent models for studying regenerative processes in adult organisms. We are interested in intestinal regeneration in the sea cucumber, Holothuria glaberrima, and focus here on the regeneration of intestinal muscle components. We have used immunohistochemical techniques to describe the formation of the intestinal muscle layers. Myoblasts are first observed within the regenerating structure, adjacent to the coelomic epithelia. Within a few days, these cells acquire muscle markers and form a single cell layer that underlies the epithelia. Animals injected with BrdU at various regeneration stages have been subsequently analyzed for the presence of muscle differentiation markers. BrdU-labeled muscle nuclei are observed in myocytes of 3-week regenerates, showing that these cells originate from proliferating precursors. The peak in muscle precursor proliferation appears to occur during the second week of regeneration. Therefore, new muscle cells in the regenerating intestine originate from precursors that have undergone cell division. Our results suggest that the precursor cells arise from the coelomic epithelia. We also provide a comparative view of muscle regeneration in an echinoderm, a topic of interest in view of the many recent studies of muscle regeneration in vertebrate species.

Alterations in endothelial cell proliferation and apoptosis contribute to vascular remodeling following hind-limb ischemia in rabbits

Hind-limb ischemia is a potent stimulus for angiogenesis. However, capillary density does not change in tibialis anterior muscle (TA) following hind-limb ischemia, despite increases in angiogenic growth factors. The objective of this study was to determine whether changes in proliferation and apoptosis occurred in the same muscle. In total, 19 New Zealand white rabbits underwent femoral artery ligation and excision and the ischemic and contra-lateral (control) TA muscles were harvested after 1 (n = 7), 5 (n = 7) and 21 (n= 5). Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) was used to detect apoptosis and double staining was used to identify the apoptotic cell types. Proliferation was assessed by immunohistochemistry for proliferating cell nuclear antigen (PCNA) and [3H]thymidine incorporation, in vitro. TUNEL positive nuclei were greater in ischemic than control muscle at 1 day (1.83 +/- 0.70% vs 1.03 +/- 0.20%), 5 days (2.13 +/- 0.50% vs 1.21 +/- 0.42%) and at 21 days the difference was statistically significant (3.42 +/- 0.80% vs 0.96 +/- 0.40%, p < 0.01). The majority of TUNEL positive nuclei were endothelial (Tie2 positive) cells. The number of PCNA positive cells in ischemic versus control muscle was similar at 1 day (0.71 +/- 0.20% vs 0.53 +/- 0.20%) and 5 days (1.28 +/- 0.30% vs 0.77 +/- 0.30%), but was significantly (p < 0.05) reduced in ischemic muscle at 21 days (0.18 +/- 0.20% vs 1.35 +/- 0.30%) with no difference in [3H]thymidine incorporation. Directionally opposite changes in endothelial cell proliferation and apoptosis occur in TA muscle following hind-limb ischemia. Modulating apoptosis in ischemic skeletal muscle may present a novel therapeutic target in peripheral arterial disease.