TGF-β1 regulates differentiation of bone marrow mesenchymal stem cells

Mesenchymal stromal/stem cells (MSCs) are a small population of stromal cells present in most adult connective tissues, such as bone marrow, fat tissue, and umbilical cord blood. MSCs are maintained in a relative state of quiescence in vivo but, in response to a variety of physiological and pathological stimuli, are capable of proliferating then differentiating into osteoblasts, chondrocytes, adipocytes, or other mesoderm-type lineages like smooth muscle cells (SMCs) and cardiomyocytes. Multiple signaling networks orchestrate MSCs differentiating into functional mesenchymal lineages. Among these, transforming growth factor-β1 (TGF-β1) has emerged as a key player. Hence, we summarize the effects of TGF-β1 on differentiation of MSCs toward different lineages. TGF-β1 can induce either chondrogenic or SMC differentiation of MSCs in vitro. However, it requires cell-cell and cell-matrix interactions, similar to development of these tissues in vivo. The effect of TGF-β1-regulated osteogenic differentiation of MSCs in vitro depends on the specific culture conditions involved. TGF-β1 inhibits adipogenic differentiation of MSCs in monolayer culture. Using this information, we may optimize the culture conditions to differentiate MSCs into desired lineages.

Transforming growth factor-beta increases the expression of vascular smooth muscle cell markers in human multi-lineage progenitor cells

BACKGROUND

Vascular smooth muscle cell (SMC) differentiation is an essential component of vascular repair and tissue engineering. However, currently used cell models for the study of SMC differentiation have several limitations. Multi-lineage progenitor cells (MLPCs) originate from human umbilical cord blood and are cloned from a single cell. The object of this study was to investigate whether MLPCs could differentiate into SMCs in vitro with induction by transforming growth factor beta1 (TGF-beta1).

MATERIAL/METHODS

MLPCs were treated without or with TGF-beta1 (1 and 5 ng/mL) in mesenchymal stem cell media plus 1% FBS for 7 days. Total RNA was isolated from the MLPCs, and semi-quantitative real-time PCR was performed to test the following mRNA levels: early and late phase SMC-specific markers, two endothelial cell (EC)-specific markers, endothelial progenitor cell (EPC) marker CD34, TGF-beta1 accessory protein CD105, and adhesion molecule CD146.

RESULTS

TGF-beta1 (1 ng/mL) significantly increased the mRNA levels of SMC-specific markers SM22α, calponin-1, SM α-actin, caldesmon, tropomyosin and MLCK as well as adhesion molecule CD146. The mRNA levels of EC-specific markers VE-cadherin and VEGFR-2, EPC marker CD34 and TGF-beta1 accessory protein CD105 were decreased significantly, after MLPC were treated with TGF-beta1 (1 ng/mL). TGF-beta1 at 5 ng/mL showed similar effect on the expression of these genes.

CONCLUSIONS

This study demonstrates that in the presence of TGF-beta1, MLPCs undergo SMC lineage differentiation indicating that MLPCs are a promising cell model for SMC lineage differentiation studies, which may contribute to advances in vascular repair and tissue engineering.

Expansion of the human adipose-derived stromal vascular cell fraction yields a population of smooth muscle-like cells with markedly distinct phenotypic and functional properties relative to mesenchymal stem cells

Adipose tissue contains a heterogeneous cell population composed of endothelial cells, adipocytes, smooth muscle cells (SMC), and mesenchymal progenitors and stromal cells that meet the criteria put forth by the International Society for Cellular Therapy as defining mesenchymal stem cells (MSC). In this study, we expanded the stromal vascular fraction (SVF) of human adipose tissue and characterized the resulting adherent primary cell cultures by quantitative reverse transcription-polymerase chain reaction, antigen expression, protein fingerprinting, growth kinetics, in vitro tri-lineage differentiation bioactivity, and functional responses to small molecules modulating SMC-related developmental pathways and compared the results to those obtained with functionally validated MSC cultures. SVF-derived initial cultures (P0) were expanded in a defined medium that was not optimized for MSC growth conditions, neither were recombinant cytokines or growth factors added to the media to direct differentiation. The adherent cell cultures derived from SVF expansion under these conditions had markedly distinct phenotypic and biological properties relative to functionally validated MSC cultures. SVF-derived adherent cell cultures retained characteristics consistent with the SMC subpopulation within adipose tissue--phenotype, gene, and protein expression--that were independent of passage number and source of SVF (n=4 independent donors). SVF-derived cells presented significantly less robust in vitro tri-lineage differentiation bioactivity relative to validated MSC. Expanded SVF cells and MSC had opposite responses to the thromboxane A2 mimetic U46619, demonstrating an unambiguous functional distinction between the two cell types. Taken together, these data support the conclusions that SVF cells expanded under the conditions described in these studies are accurately described as adipose-derived SMC and represent a cellular subpopulation of adipose SVF that is separate and distinct from other classes of adipose-derived cells.

Characterization of smooth muscle differentiation of purified human skeletal muscle-derived cells

The purpose of this study is to characterize the smooth muscle differentiation of purified human muscle-derived cells (hMDCs). The isolation and purification of hMDCs were conducted by modified preplate technique and Dynal CD34 cell selection. Smooth muscle cell differentiation was induced by the use of smooth muscle induction medium (SMIM) and low-serum medium. The gene expressions at the mRNA and protein levels of undifferentiated and differentiated hMDCs were tested by RT-PCR, Western blot and immunofluorescence studies. Western blot and immunofluorescence studies demonstrated the purified hMDCs cultured in SMIM for 4 weeks and expressed significant amount of smooth muscle myosin heavy chain (MHC) and α-smooth muscle actin (ASMA). The cells cultured in low-serum medium for 4 weeks also expressed ASMA, while the control group did not. RT-PCR analysis showed increased gene expression of smooth muscle markers, such as ASMA, Calponin, SM22, Caldesmon, Smoothelin and MHC when purified hMDCs were exposed to SMIM for 2 and 4 weeks when compared to the controls. In conclusion, we confirmed the smooth muscle differentiation capability of purified hMDCs. The gene expression of smooth muscle differentiation of purified hMDCs was characterized. These cells may be potential biomaterials for human tissue regeneration.

Bone marrow mesenchymal stromal cell therapy for external urethral sphincter restoration in a rat model of stress urinary incontinence

OBJECTIVE

To assess the effect of intra-sphincteric injections of bone marrow mesenchymal stromal cells (MSCs) on Valsalva leak point pressure (VLPP) changes in an animal model of stress urinary incontinence (SUI).

MATERIALS AND METHODS

Twenty-four female Sprague-Dawley rats underwent bilateral pudendal nerve section to induce SUI. Six rats were SUI controls, 6 received periurethral injection of Plasma-Lyte (SUI placebo control) and 12 were given periurethral injection of PKH26-labeled MSCs. Four weeks after injection, conscious cystometry was undertaken in animals and VLPP recorded. All groups were sacrificed, and frozen urethra sections were submitted to pathology and immunohistochemistry assessment.

RESULTS

Rat MSCs were positive for the cell surface antigens CD44, CD73, CD90, and RT1A, and negative for CD31, CD45, and RT1B, confirming their stem cell phenotype. In vitro, differentiated MSCs expressed α-smooth muscle actin (SMA) and desmin, markers of smooth and striated muscles in vivo. Immunohistochemistry of rat urethras revealed PKH26-labeled MSCs in situ and at the injection site. LPP was significantly improved in animals injected with MSCs. Mean LPP was 24.28 ± 1.47 cmH(2) O in rats implanted with MSCs and 16.21 ± 1.26 cmH(2) O in SUI controls (P<0.001). Atrophic urethras with implanted MSCs were positively stained for myosin heavy chain and desmin.

CONCLUSION

Rat MSCs have the ability to differentiate and skew their phenotype towards smooth and striated muscles, as demonstrated by SMA up-regulation and desmin expression. Periurethral injection of MSCs in an animal model of SUI restored the damaged external urethral sphincter and significantly improved VLPP.

Application of mesenchymal stromal cells in urological diseases

The application of stem cells and their use in tissue-engineering approaches is emerging in clinical therapeutic intervention strategies. The use of adult stem cells, either autologous or allogenic, does not raise ethical concerns, in contrast to embryonic stem cells. Mesenchymal stromal cells (MSCs) can be easily obtained from bone marrow or from adipose tissue and further expanded in vitro. Due to their differentiation capacity, MSCs are very attractive for tissue engineering purposes. Furthermore, MSCs secrete a variety of mediators that have beneficial effects on the regenerating tissue. In this review we give an insight into stem cell hierarchy, define the properties of MSCs and summarize recent reports of their administration in urological diseases.