Identification of two types of smooth muscle cells from rabbit urinary bladder

Live births from urine derived cells

Here we report urine-derived cell (UDC) culture and subsequent use for cloning which resulted in the successful development of cloned canine pups, which have remained healthy into adulthood. Bovine UDCs were used in vitro to establish comparative differences between cell sources. UDCs were chosen as a readily available and noninvasive source for obtaining cells. We analyzed the viability of cells stored in urine over time and could consistently culture cells which had remained in urine for 48hrs. Cells were shown to be viable and capable of being transfected with plasmids. Although primarily of epithelial origin, cells were found from multiple lineages, indicating that they enter the urine from more than one source. Held in urine, at 4°C, the majority of cells maintained their membrane integrity for several days. When compared to in vitro fertilization (IVF) derived embryos or those from traditional SCNT, UDC derived embryos did not differ in total cell number or in the number of DNA breaks, measured by TUNEL stain. These results indicate that viable cells can be obtained from multiple species' urine, capable of being used to produce live offspring at a comparable rate to other cell sources, evidenced by a 25% pregnancy rate and 2 live births with no losses in the canine UDC cloning trial. This represents a noninvasive means to recover the breeding capacity of genetically important or infertile animals. Obtaining cells in this way may provide source material for human and animal studies where cells are utilized.

Isolation, expansion and characterization of porcine urinary bladder smooth muscle cells for tissue engineering

Background

A key requirements for therapy utilizing the tissue engineering methodologies is use of techniques which have the capability to yield a high number of cells, from small tissue biopsy in a relatively short time. Up to date there was no optimal methods of isolation and expansion of urinary bladder smooth muscle cells (UB-SMCs). The aim of this study was to compare isolation and expansion techniques of UB-SMCs to select the most repeatable and efficient one.

Method

Five protocols of porcine UB- SMCs isolation including enzymatic and explant techniques and three expansion techniques were compared. Isolation effectiveness was evaluated using trypan blue assay. Cell phenotype was confirmed by immunofluorescence staining. Proliferation rate was analyzed using MTT and X- Celligence system. Cellular senescence was assessed measuring β-galactosidase activity.

Results

Enzymatic methods using collagenase with dispase (method I) or collagenase only (method III) allowed to isolate much larger number of cells than the methods using trypsin with collagenase (method II) and collagenase after digestion with trypsin (method IV). The success rate of establishment of primary culture was the highest when the isolated cells were cultured in the Smooth muscle Growth Medium-2 (SmGM-2). Expression of the smooth muscle markers- alpha smooth muscle actin and smoothelin was the highest for cells isolated by enzymatic method I and cultured in SmGM-2. There was no significant signs of cell senescence until the 8th passage.

Conclusion

The most efficient method of establishment of porcine UB-SMCs culture is enzymatic digestion of urinary bladder tissue with collagenase and dispase and culture of isolated cells in SmGM-2. This method was up to 10 times more efficient than other methods used for isolation and culture of UB-SMCs. This is an easy and consistent method for obtaining high numbers of urinary bladder smooth muscle cells.

Myosin II isoforms in smooth muscle: heterogeneity and function

Both smooth muscle (SM) and nonmuscle class II myosin molecules are expressed in SM tissues comprising hollow organ systems. Individual SM cells may express one or more of multiple myosin II isoforms that differ in myosin heavy chain (MHC) and myosin light chain (MLC) subunits. Although much has been learned, the expression profiles, organization within contractile filaments, localization within cells, and precise roles in various contractile functions of these different myosin molecules are still not well understood. However, data supporting unique physiological roles for certain isoforms continues to build. Isoform differences located in the S1 head region of the MHC can alter actin binding and rates of ATP hydrolysis. Differences located in the MHC tail can alter the formation, stability, and size of the myosin thick filament. In these distinct ways, both head and tail isoform differences can alter force generation and muscle shortening velocities. The MLCs that are associated with the lever arm of the S1 head can affect the flexibility and range of motion of this domain and possibly the motion of the S2 and motor domains. Phosphorylation of MLC(20) has been associated with conformational changes in the S1 and/or S2 fragments regulating enzymatic activity of the entire myosin molecule. A challenge for the future will be delineation of the physiological significance of the heterogeneous expression of these isoforms in developmental, tissue-specific, and species-specific patterns and or the intra- and intercellular heterogeneity of myosin isoform expression in SM cells of a given organ.

Distribution of phenotypically disparate myocyte subpopulations in airway smooth muscle

Phenotype and functional heterogeneity of airway smooth muscle (ASM) cells in vitro is well known, but there is limited understanding of these features in vivo. We tested whether ASM is composed of myocyte subsets differing in contractile phenotype marker expression. We used flow cytometry to compare smooth muscle myosin heavy chain (smMHC) and smooth muscle-α-actin (sm-α-actin) abundance in myocytes dispersed from canine trachealis. Based on immunofluorescent intensity and light scatter characteristics (forward and 90° side scatter), 2 subgroups were identified and isolated. Immunoblotting confirmed smMHC and sm-α-actin were 10- and 5-fold greater, respectively, in large, elongate myocytes that comprised ~60% of total cells. Immunohistochemistry revealed similar phenotype heterogeneity in human bronchial smooth muscle. Canine tracheal myocyte subpopulations isolated by flow cytometry were used to seed primary subcultures. Proliferation of subcultures established with myocytes exhibiting low levels of smMHC and sm-α-actin was ~2× faster than subcultures established with ASM cells with a high marker protein content. These studies demonstrate broad phenotypic heterogeneity of myocytes in normal ASM tissue that is maintained in cell culture, as demonstrated by divergent proliferative capacity. The distinct roles of these subgroups could be a key determinant of normal and pathological lung development and biology.Key words: flow cytometry, phenotype, heterogeneity, asthma, differentiation.

CHARACTERIZATION OF THE CONTROL OF INTRACELLULAR [CA 2+ ] AND THE CONTRACTILE PHENOTYPE OF CULTURED HUMAN DETRUSOR SMOOTH MUSCLE CELLS

PURPOSE

We measured the functional properties of cultured human detrusor myocytes with respect to their ability to regulate their intracellular [Ca2+] and generate force in collagen matrices.

MATERIALS AND METHODS

Human detrusor biopsies were dissociated into single cells by collagenase treatment and used immediately or cultured in D-valine medium and subsequently used after culture trypsinization. Intracellular [Ca2+] was measured in Fura-2 loaded myocytes. Cell force development was measured by incorporating cells into a collagen gel and attaching it to an isometric strain gauge.

RESULTS

Carbachol was equally effective in generating Ca transients in freshly isolated and cultured cells. Carbachol potency (pEC50) and the magnitude of Ca2+ transients were similar. Adenosine triphosphate potency was decreased in cultured cells and Ca2+ transients showed properties consistent with a purinoceptor shift from a purinergic subtype. Temporal restitution of Ca2+ transients was similar in the 2 groups, indicative of retained intracellular Ca2+ stores in cultured cells. Cultured cells (approximately 10(6)) embedded in collagen gel generated a force about 10 times greater than that generated by gel alone. The cell dependent force could be further increased by adding carbachol.

CONCLUSIONS

Cultured cells retain the ability to generate agonist induced intracellular Ca2+ transients. There was no evidence that the cell culture altered the properties of muscarinic receptors, although purinoceptor mediated properties were altered. Restitution experiments indicated that functional intracellular Ca2+ stores were retained in cultured cells. Cultured cells also retained a contractile phenotype, especially in response to carbachol. The magnitude of force was attenuated, which may be a function of the biomechanical properties of the gel used to embed the cells.

Bladder smooth muscle cell phenotypic changes and implication of expression of contractile proteins (especially caldesmon) in rats after partial outlet obstruction

BACKGROUND

The purpose of the present study was to investigate morphological changes in bladder smooth muscle of rats with partial outlet obstruction. We investigated smooth muscle cell phenotypic changes and implication of synthetic phenotype in contractility decrease and bladder compliance after bladder outlet obstruction.

METHODS

Partial bladder outlet obstruction was introduced in female rats. Bladder were removed at 1, 3, 6, 10 and 20 weeks after the obstruction. Temporal pattern of changes in bladder mass, light microscopic pathogenesis and phenotypic expression of the bladder smooth muscle cells in the electron micrographs were investigated. Expression of contractile protein was also investigated by the immunoblotting method.

RESULTS

Marked increase in bladder mass with marked thickening of smooth muscle layer was observed at 1 week after obstruction. The ratio of myocytes exhibiting contractile and synthetic phenotypes was almost constant until 6 weeks after the obstruction, but thereafter, synthetic phenotypes gradually increased and the ratio (synthetic/contractile phenotype) was 1.5-fold at 20 weeks after the obstruction. Caldesmon was most markedly expressed after the obstruction among contractile proteins examined by the immunoblotting method.

CONCLUSION

Phenotypic changes were confirmed in bladder smooth muscle, and the decrease of the ratio of contractile phenotype was observed after long-term obstruction of the bladder outlet. Among the contractile proteins in the bladder smooth muscle cell, caldesmon was considered a reliable marker for predicting the pathogenetic conditions of the bladder.

Heterogeneity of bladder myocytes in vitro: modulation of myosin isoform expression

We studied the expression of myosin heavy chain isoforms differing at the N-terminal (SM-A, SM-B) and the C-terminal (SM1, SM2) regions and non-muscle myosin heavy chain II-A and II-B (NMMHC II-A and B) in newborn and adult rabbit bladder smooth muscle cells (SMCs) and in cultures of enzymatically dissociated neonatal detrusor. RT-PCR analyses revealed that 94.5+/-3.27% of MHC transcripts of the adult bladder SMCs contained the 21-nucleotide insert (SM-B) compared with 83.8+/-3.2% in the newborn bladder, with the remainder of the mRNA being non-inserted (SM-A). In 3, 7, and 10 days of primary culture (proliferating, confluent, and post-confluent, respectively) and up to 4 subculture passages, bladder myocytes expressed predominantly SM-A. Immunofluorescence microscopy revealed heterogeneity in cultured myocytes, i.e. SM-B positive cells coexisting with negatively stained cells. In adult bladder, the C-terminal isoforms SM1 and SM2 represented, 43.1+/-4.3% and 56.89 + 4.3% of the mRNA, respectively, while newborn bladders expressed 72.5+/-7% SM1 and 27.5+/-7% SM2. Upon culturing, cells predominantly expressed SM1 at both the mRNA and protein levels. NMMHC II-A was expressed by both adult and newborn bladders and in culture, whereas NMMHC II-B was expressed at low levels only in newborn bladders, but upregulated in culture. These data indicate that bladder myocytes in vitro undergo modulation with relative overexpression of SM-A and SM1 and upregulation of NMMHC II-B. Information on the mechanisms responsible for this modulation in vitro might provide an understanding of the nature of altered myosin isoform expression associated with smooth muscle dysfunction in certain bladder diseases.

Molecular mechanisms of phenotypic plasticity in smooth muscle cells

Morphological, functional, molecular and cell biology studies have revealed a striking multifunctional nature of individual smooth muscle cells (SMC). SMCs manifest phenotypic plasticity in response to changes in environment and functional requirements, acquiring a range of structural and functional properties bounded by two extremes, called "synthetic" and "contractile." Each phenotypic state is characterized by expression of a unique set of structural, contractile, and receptor proteins and isoforms that correlate with differing patterns of gene expression. Recent studies have identified signaling pathways and transcription factors (e.g., RhoA GTPase/ROCK, also known as Rho kinase, and serum response factor) that regulate the transcriptional activities of genes encoding proteins associated with the contractile apparatus. Mechanical plasticity of contractile-state smooth muscle further extends SMC functional diversity. This may also be regulated, in part, by the RhoA GTPase/ROCK pathway, via reorganization of cytoskeletal and contractile proteins. Future studies that define transcriptional and posttranscriptional mechanisms of SMC plasticity are necessary to fully understand the role of SMC in the pathogenesis and morbidity of human diseases of the airways, vasculature, and gastrointestinal tract.

Expression of smooth muscle myosin light chain 17 and unloaded shortening in single smooth muscle cells

These experiments were performed to test the hypotheses that myosin light chain 17 (MLC(17)) a and b isoform expression varies between individual vascular smooth muscle (SM) cells and that their expression correlates with cell unloaded shortening velocity. Single SM cells isolated from rabbit aorta and carotid arteries were used to measure unloaded shortening velocity and subsequently were analyzed via RT-PCR for MLC(17) a and b mRNA ratio. The MLC(17b/a) mRNA and protein ratios from adjacent tissue sections correlate very well (R(2) = 0.68), allowing use of the mRNA ratio to predict the protein ratio. The rabbit MLC(17) isoform protein sequence was found to be similar to, but unique from, the swine, mouse, and chicken sequences. Isolated single SM cells from the aorta and carotid have resting lengths of 70-280 microm and shorten to 33-88 microm after contraction. Isolated cell maximum unloaded shortening velocity is highly variable (0.5-7.5 microm/s) but becomes more uniform when normalized to initial cell length (0.01-0.05 cell lengths/s). Carotid cells activated in the presence of okadaic acid (1 microm) have mean maximal unloaded shortening velocities not significantly different from carotid cells activated without okadaic acid (0.016 vs. 0.019 cell lengths/s). Resting cell length before activation is significantly correlated with final cell length after unloaded shortening. Neither initial cell length, final cell length, total cell length change, nor maximum unloaded shortening velocity (absolute or normalized) was significantly correlated with single-cell MLC(17b/a) mRNA ratio. These studies were performed in isolated single SM cells where unloaded shortening velocity and MLC(17b/a) mRNA ratios were measured in the same cell. In this preparation, the three-dimensional organization and milieu of the cell is kept intact, but without the intercellular heterogeneity concerns of multicellular preparations. These results suggest the MLC(17b/a) ratio is variable between individual SM cells from the same tissue, but it is not a determinant of unloaded shortening velocity in single SM cells.

Divergent differentiation paths in airway smooth muscle culture: induction of functionally contractile myocytes

We tested the hypothesis that prolonged serum deprivation would allow a subset of cultured airway myocytes to reacquire the abundant contractile protein content, marked shortening capacity, and elongated morphology characteristic of contractile cells within intact tissue. Passage 1 or 2 canine tracheal smooth muscle (SM) cells were grown to confluence, then serum deprived for up to 19 days. During serum deprivation, two differentiation pathways emerged. One-sixth of the cells developed an elongated morphology and aligned into bundles. Elongated myocytes contained cables of contractile myofilaments, dense bodies, gap junctions, and membrane caveoli, ultrastructural features of contractile SM in tissue. These cells immunostained intensely for SM alpha-actin, SM myosin heavy chain (MHC), and SM22 (an SM-specific actin-binding protein), and Western analysis of culture lysates disclosed 1.8 (SM alpha-actin)-, 7.7 (SM MHC)-, and 5.8 (SM22)-fold protein increases during serum deprivation. Immunoreactive M3 muscarinic receptors were present in dense foci distributed throughout elongated, SM MHC-positive myocytes. ACh (10(-3) M) induced a marked shortening (59.7 +/- 14.4% of original length) in 62% of elongated myocytes made semiadherent by gentle proteolytic digestion, and membrane bleb formation (a consequence of contraction) occurred in all stimulated cells that remained adherent and so did not shorten. Cultured airway myocytes that did not elongate during serum deprivation instead became short and flattened, lost immunoreactivity for contractile proteins, lacked the M3 muscarinic-receptor expression pattern seen in elongated cells, and exhibited no contractile response to ACh. Thus we demonstrate that prolonged serum deprivation induces distinct differentiation pathways in confluent cultured tracheal myocytes and that one subpopulation acquires an unequivocally functional contractile phenotype in which structure and function resemble contractile myocytes from intact tissue.

Cellular terrain surrounding sympathetic nerve pathways in the rat orbit: comparisons of orbital connective tissue and smooth muscle cell phenotypes

Sympathetic axons are abundant within some orbital tissues but are absent from others. This study investigated cellular phenotypes of tissues containing sympathetic nerves en passage and compared these with phenotypes in regions devoid of sympathetic nerves and with smooth muscle targets. Two primary orbital smooth muscle targets, the tarsal muscle and orbital muscle, contained many synaptophysin-immunoreactive nerves. Target cells had ultrastructural features typical of smooth muscle and were immunoreactive for alpha-smooth muscle actin, smooth muscle myosin heavy chain, desmin, vinculin, and laminin, but not non-muscle myosin, vimentin, fibronectin, or type IV collagen; nerve growth factor (NGF) mRNA was detected by reverse transcription-polymerase chain reaction. Periorbital sheath devoid of sympathetic nerves contained elongated fibroblasts that were immunoreactive for vimentin, non-muscle myosin, and fibronectin, but not for alpha-smooth muscle actin, smooth muscle myosin heavy chain, vinculin, desmin, laminin, or type IV collagen, and did not express NGF mRNA. Regions of periorbital sheath containing sympathetic nerves had few synaptophysin-immunoreactive varicosities. Cells in this region contained myofilaments, ribosomes, and rough endoplasmic reticulum and were larger than tarsal muscle cells. They expressed NGF mRNA and showed a unique immunophenotype, reacting for vimentin, alpha-smooth muscle actin and myosin heavy chain, desmin, vinculin, laminin, and type IV collagen. This phenotype reflects both fibroblast and smooth muscle features similar to myofibroblasts or transdifferentiated smooth muscle described in other tissues. The spatial association between these cells and sympathetic nerves suggests that they may be involved in axon guidance or maintenance.