Human bronchial fibroblasts exhibit a mesenchymal stem cell phenotype and multilineage differentiating potentialities

Evidence of chondrocyte turnover in lung cartilage, with the probable participation of nestin-positive cells

Healthy adult cartilage is thought to have little or no capacity to renewal, and cell turnover has not been reported in lung cartilage. We report that chondrocyte turnover occurs in lung cartilage, found in an unrelated study. Lung specimens from CD1 mice of 2, 6, 12, 18 or 24 months were fixed in 10% neutral-buffered formalin and paraffin-embedded. Apoptosis was analysed by in situ end-labelling of fragmented DNA. Proliferating cell nuclear antigen (PCNA) and nestin were examined by immunohistochemistry. Apoptosis and PCNA were detected in lung chondrocytes. Serial section analysis showed that cells in apoptosis were different from PCNA-positive cells, indicating that turnover was occurring. Chondrocytes were negative for nestin. Nestin-positive cells were present in connective tissue associated with cartilage, in some specimens in close proximity of it and in perivascular cells. Thus cell turnover in lung cartilage is possible, which may be mediated by nestin-positive cells.

Anti-inflammatory role and immunomodulation of mesenchymal stem cells in systemic joint diseases: potential for treatment

INTRODUCTION

Mesenchymal stem cells (MSCs) are multipotent stromal cells characterized by their ability to differentiate into adipocytes, chondrocytes, osteocytes and a number of other lineages. Investigation into their use has increased in recent years as characterization of their immunomodulatory properties has developed, and their role in the pathophysiology of joint disease has been suggested.

AREAS COVERED

MSCs demonstrate immunosuppressive functionality by suppressing T- and B-cell responses following activation by cytokines such as IL-6 and IL-1α. They also can be induced to exert pro-inflammatory effects in the presence of acute inflammatory environment due to the actions of TNF-α and IFN-γ. In inflammatory joint diseases such as rheumatoid arthritis, MSCs in bone marrow migrate to joints by a TNF-α-dependent mechanism and may be in part responsible for the disease process. MSCs have also been demonstrated in increased numbers in periarticular tissues in osteoarthritis, which may reflect an attempt at joint regeneration.

EXPERT OPINION

Clinical applications for MSCs have shown promise in a number of inflammatory and autoimmune disorders. Future work is likely to further reveal the immunosuppressive characteristics of MSCs, their role in the pathophysiology of joint diseases and provide the basis for new avenues for treatment.

Mesenchymal stem cells in non-small cell lung cancer--different from others? Insights from comparative molecular and functional analyses

BACKGROUND

Cancer-associated fibroblasts (CAF) play a vital role in lung cancer initiation and progression. Although mesenchymal stem cells (MSC) are considered progenitor cells of fibroblasts and show cancer modulating abilities themselves, analyses on their presence and properties in lung cancer are lacking so far.

METHODS

We performed a comparative molecular and functional analysis of MSC derived from non-small cell lung cancer (NSCLC) and corresponding normal lung tissue (NLT) of a total of 15 patients. MSC were identified and selected according to their mesenchymal multilineage differentiation capability and surface marker profile.

RESULTS

Compared to NLT-MSC, NSCLC-MSC showed accelerated growth kinetics and reduced sensitivity to cisplatin. Karyotyping, comparative genomic hybridization and multiplex fluorescence in situ hybridization revealed no chromosomal aberrations. However, gene expression profiling of NSCLC- and NLT-MSC indicated variable expression of 62 genes involved in proliferation, DNA repair, apoptosis, extracellular matrix synthesis, tissue remodeling and angiogenesis. Differential expression of the selected candidate genes butyrylcholinesterase, clusterin and quiescin Q6 sulfhydryl oxidase 1 was validated by quantitative real-time PCR and, on protein level, by immunohistochemical analyses of original tumor tissue. Upon exposure to tumor cell-conditioned medium or transforming growth factor-β, both, NSCLC-MSC and NLT-MSC acquired expression of α-smooth muscle actin (α-SMA), a major characteristics of CAF.

CONCLUSIONS

This study indicates that NSCLC tissue contains MSC with specific molecular and functional properties. These cells might represent a progenitor reservoir for CAF and thus crucially contribute to lung cancer progression.

Tracheal regeneration: evidence of bone marrow mesenchymal stem cell involvement

OBJECTIVES

Recent advances in airway transplantation have shown the ability of ex vivo or in vivo tracheal regeneration with bioengineered conduits or biological substitutes, respectively. Previously, we established a process of in vivo-guided tracheal regeneration using vascular allografts as a biological scaffold. We theorized that tracheal healing was the consequence of a mixed phenomenon associating tracheal contraction and regeneration. The aim of the present study was to determine the role that bone marrow stem cells play in that regenerative process.

METHODS

Three groups of 12 rabbits underwent a gender-mismatched aortic graft transplantation after tracheal resection. The first group received no cells (control group), the second group had previously received autologous green fluorescent protein-labeled mesenchymal stem cell transplantation, and the third group received 3 labeled mesenchymal stem cell injections on postoperative days 0, 10, and 21.

RESULTS

The clinical results were impaired by stent complications (obstruction or migration), but no anastomotic leakage, dehiscence, or stenosis was observed. The rabbits were killed, and the trachea was excised for analysis at 1 to 18 months after tracheal replacement. In all 3 groups, microscopic examination showed an integrated aortic graft lined by metaplastic epithelium. By 12 months, immature cartilage was detected among disorganized elastic fibers. Positive SRY gene detection served as evidence for engraftment of cells derived from the male recipient. EF-green fluorescent protein detection showed bone marrow-derived mesenchymal stem cell involvement.

CONCLUSIONS

The results of the present study imply a role for bone marrow stem cells in tracheal regeneration after aortic allografting. Studies are necessary to identify the local and systemic factors stimulating that regenerative process.

Exploring the stem cell and non-stem cell constituents of human breast milk

The immense potency of nutritional components of human breast milk and importance of breastfeeding is known worldwide. Recent researches had identified stem cells as integral component of human breast milk. Nevertheless, there is little proof of evidence on the stem cell constituents of breast milk. It is imperative to explore the cellular constituents of human breast milk, including of stem cells, to open new avenue in child's development and regeneration. Thus, we aimed at identifying the cellular constituents of human breast milk by phenotypic characterisation of diverse cell surface markers of hematopoietic stem cells (CD 34, CD 133, CD 117), mesenchymal stem cells (CD 90, CD 105, CD 73), myoepithelial cells (CD 29, CD 44), Immune cells (CD 209, CD 86, CD 83, CD 14, CD 13, HLADR, CD 45), as well as cell adhesion molecules (CD 31, CD 54, CD 166, CD 106, CD 49d), and other markers (ABCG2, CD140b) using flowcytometry. We found a lower expression of CD 34 (13.07 ± 2.0 %), CD 90 (7.79 ± 0.8 %) and CD 73 (2.19 ± 0.41 %), indicating scanty hematopoietic and mesenchymal stem cell population in human breast milk. On contrary, myoepithelial progenitors, cell adhesion molecules, immune cells and growth factors were identified as the major constituents of breast milk. Overall, this study illuminates the benefits of breast feeding as breast milk encompasses heterogeneous cellular components that benefits child's growth, immunity and development. However, further research on these constituents of human breast milk will widen their applicability in treatment of neonatal disorders.

RNA-seq analysis reveals different dynamics of differentiation of human dermis- and adipose-derived stromal stem cells

BACKGROUND

Tissue regeneration and recovery in the adult body depends on self-renewal and differentiation of stem and progenitor cells. Mesenchymal stem cells (MSCs) that have the ability to differentiate into various cell types, have been isolated from the stromal fraction of virtually all tissues. However, little is known about the true identity of MSCs. MSC populations exhibit great tissue-, location- and patient-specific variation in gene expression and are heterogeneous in cell composition.

METHODOLOGY/PRINCIPAL FINDINGS

Our aim was to analyze the dynamics of differentiation of two closely related stromal cell types, adipose tissue-derived MSCs (AdMSCs) and dermal fibroblasts (FBs) along adipogenic, osteogenic and chondrogenic lineages using multiplex RNA-seq technology. We found that undifferentiated donor-matched AdMSCs and FBs are distinct populations that stay different upon differentiation into adipocytes, osteoblasts and chondrocytes. The changes in lineage-specific gene expression occur early in differentiation and persist over time in both AdMSCs and FBs. Further, AdMSCs and FBs exhibit similar dynamics of adipogenic and osteogenic differentiation but different dynamics of chondrogenic differentiation.

CONCLUSIONS/SIGNIFICANCE

Our findings suggest that stromal stem cells including AdMSCs and dermal FBs exploit different molecular mechanisms of differentiation to reach a common cell fate. The early mechanisms of differentiation are lineage-specific and are similar for adipogenic and osteogenic differentiation but are distinct for chondrogenic differentiation between AdMSCs and FBs.

Comparison of epithelial differentiation and immune regulatory properties of mesenchymal stromal cells derived from human lung and bone marrow

Mesenchymal stromal cells (MSCs) reside in many organs including lung, as shown by their isolation from fetal lung tissues, bronchial stromal compartment, bronchial-alveolar lavage and transplanted lung tissues. It is still controversial whether lung MSCs can undergo mesenchymal-to-epithelial-transition (MET) and possess immune regulatory properties. To this aim, we isolated, expanded and characterized MSCs from normal adult human lung (lung-hMSCs) and compared with human bone marrow-derived MSCs (BM-hMSCs). Our results show that lung-MSCs reside at the perivascular level and do not significantly differ from BM-hMSCs in terms of immunophenotype, stemness gene profile, mesodermal differentiation potential and modulation of T, B and NK cells. However, lung-hMSCs express higher basal level of the stemness-related marker nestin and show, following in vitro treatment with retinoic acid, higher epithelial cell polarization, which is anyway partial when compared to a control epithelial bronchial cell line. Although these results question the real capability of acquiring epithelial functions by MSCs and the feasibility of MSC-based therapeutic approaches to regenerate damaged lung tissues, the characterization of this lung-hMSC population may be useful to study the involvement of stromal cell compartment in lung diseases in which MET plays a role, such as in chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis.

Perivascular localization of dermal stem cells in human scalp

In mammalian skin, the existence of stem cells in the dermis is still poorly understood. Previous studies have indicated that mesenchymal stem cells (MSCs) are situated as pericytes in various mammalian tissues. We speculated that the human adult dermis also contains MSC-like cells positive for CD34 at perivascular sites similar to adipose tissue. At first, stromal cells from adult scalp skin tissues showed colony-forming ability and differentiated into mesenchymal lineages (osteogenic, chondrogenic and adipogenic). Three-dimensional analysis of scalp skin with a confocal microscope clearly demonstrated that perivascular cells were positive for not only NG2, but also CD34, immunoreactivity. Perivascular CD34-positive cells were abundant around follicular portions. Furthermore, CD34-positive cell fractions collected with magnetic cell sorting were capable of differentiating into mesenchymal lineages. This study suggests that dermal perivascular sites act as a niche of MSCs in human scalp skin, which are easily accessible and useful in regenerative medicine.

Mesenchymal stromal cells and fibroblasts: a case of mistaken identity?

The plastic-adherent fibroblast-looking cells that can be isolated and culture-expanded from bone marrow and many other tissues are widely known as mesenchymal stromal cells (MSC). In addition to their fibroblast-like morphology, they are characterized by a panel of cell-surface markers and their potential to differentiate into bone, fat and cartilage. Based on their intriguing immunomodulatory and regenerative properties, MSC are being investigated as cellular therapeutics for a variety of clinical indications. However, many questions regarding the true identity and functionality of these cells in vivo remain unanswered. Fibroblasts, known for a much longer time but still poorly characterized, are also considered to be a ubiquitous stromal element of almost all tissues and are believed to play a role in tissue homeostasis. Despite the presence of MSC and fibroblasts in almost all tissues, similar morphology and other shared characteristics, the exact relationship between MSC and fibroblasts has remained undetermined. In this review, based on recent and old, but often neglected, literature it is suggested that ex vivo culture-expanded MSC and fibroblasts are indistinguishable by morphology, cell-surface markers, differentiation potential and immunologic properties.

Therapeutic effects of human STRO-3-selected mesenchymal precursor cells and their soluble factors in experimental myocardial ischemia

Stromal precursor antigen (STRO)-3 has previously been shown to identify a subset of adult human bone marrow (BM)-derived mesenchymal lineage precursors, which may have cardioprotective potential. We sought to characterize STRO-3-immunoselected and culture-expanded mesenchymal precursor cells (MPCs) with respect to their biology and therapeutic potential in myocardial ischemia. Immunoselection of STRO-3⁺ MPCs enriched for fibroblastic colony forming units from unfractionated BM mononuclear cells (MNCs). Compared to mesenchymal stem cells conventionally isolated by plastic adherence, MPCs demonstrated increased proliferative capacity during culture expansion, expressed higher levels of early ‘stem cell’ markers and various pro-angiogenic and cardioprotective cytokines, and exhibited greater trilineage developmental efficiency. Intramyocardial injection of MPCs into a rat model of myocardial infarction (MI) promoted left ventricular recovery and inhibited left ventricular dilatation. These beneficial effects were associated with cardioprotective and pro-angiogenic effects at the tissue level, despite poor engraftment of cells. Treatment of MI rats with MPC-conditioned medium (CM) preserved left ventricular function and dimensions, reduced myocyte apoptosis and fibrosis, and augmented neovascularization, involving both resident vascular cells and circulating endothelial progenitor cells (EPCs). Profiling of CM revealed various cardioprotective and pro-angiogenic factors, which had biological activity in cultures of myocytes, tissue-resident vascular cells and EPCs. Prospective immunoselection of STRO-3⁺ MPCs from BM MNCs conferred advantage in maintaining a population of immature MPCs during ex vivo expansion. Transplantation of culture-expanded MPCs into the post-MI heart resulted in therapeutic benefit, attributable at least in part to paracrine mechanisms of action. Thus, MPCs represent a promising therapy for myocardial ischemia.

Glycine decarboxylase activity drives non-small cell lung cancer tumor-initiating cells and tumorigenesis

Identification of the factors critical to the tumor-initiating cell (TIC) state may open new avenues in cancer therapy. Here we show that the metabolic enzyme glycine decarboxylase (GLDC) is critical for TICs in non-small cell lung cancer (NSCLC). TICs from primary NSCLC tumors express high levels of the oncogenic stem cell factor LIN28B and GLDC, which are both required for TIC growth and tumorigenesis. Overexpression of GLDC and other glycine/serine enzymes, but not catalytically inactive GLDC, promotes cellular transformation and tumorigenesis. We found that GLDC induces dramatic changes in glycolysis and glycine/serine metabolism, leading to changes in pyrimidine metabolism to regulate cancer cell proliferation. In the clinic, aberrant activation of GLDC correlates with poorer survival in lung cancer patients, and aberrant GLDC expression is observed in multiple cancer types. This link between glycine metabolism and tumorigenesis may provide novel targets for advancing anticancer therapy.

Myogenic Properties of Human Mesenchymal Stem Cells Derived from Three Different Sources

Mesenchymal stem cells (MSCs) of mammals have been isolated from many tissues and are characterized by their aptitude to differentiate into bone, cartilage, and fat. Differentiation into cells of other lineages like skeletal muscle, tendon/ligament, nervous tissue, and epithelium has been attained with MSCs derived from some tissues. Whether such abilities are shared by MSCs of all tissues is unknown. We therefore compared for three human donors the myogenic properties of MSCs from adipose tissue (AT), bone marrow (BM), and synovial membrane (SM). Our data show that human MSCs derived from the three tissues differ in phenotype, proliferation capacity, and differentiation potential. The division rate of AT-derived MSCs (AT-MSCs) was distinctly higher than that of MSCs from the other two tissue sources. In addition, clear donor-specific differences in the long-term maintenance of MSC proliferation ability were observed. Although similar in their in vitro fusogenic capacity with murine myoblasts, MSCs of the three sources contributed to a different extent to skeletal muscle regeneration in vivo. Transplanting human AT-, BM-, or SM-MSCs previously transduced with a lentiviral vector encoding β-galactosidase into cardiotoxin-damaged tibialis anterior muscles (TAMs) of immunodeficient mice revealed that at 30 days after treatment the frequency of hybrid myofibers was highest in the TAMs treated with AT-MSCs. Our finding of human-specific β-spectrin and dystrophin in hybrid myofibers containing human nuclei argues for myogenic programming of MSCs in regenerating murine skeletal muscle. For the further development of MSC-based treatments of myopathies, AT-MSCs appear to be the best choice in view of their efficient contribution to myoregeneration, their high ex vivo expansion potential, and because their harvesting is less demanding than that of BM- or SM-MSCs.

Isolation and characterization of resident mesenchymal stem cells in human glomeruli

We recently found that human glomeruli deprived of the Bowman's capsule contain a population of CD133(-)CD146(+) cells that coexpress the typical mesenchymal stem cells (MSCs) markers (such as CD29, CD105, and CD73) and renal specific stem cell markers (such us CD24 and Pax2). This population exhibited in vitro self-renewal capability, clonogenicity, and multipotency. Beside to osteogenic, adipogenic, and chondrogenic differentiation, these cells when cultured in appropriate culture conditions were able to differentiate into endothelial cells, epithelial cells expressing podocytes markers, and mesangial cells. These populations may have a role in the physiological cell turnover and/or in the response to renal injury. Herein, we present a review of the experimental procedures used for isolation and characterize MSCs resident in human adult glomeruli.

Effect of mechanical stimulation on the differentiation of cord stem cells

In this study, we evaluated the effect of mechanical stimulation on the differentiation of umbilical cord-derived mesenchymal stem cells (UC-MSCs) in osteogenic medium using a Flexcell system that imposed cyclic uniaxial mechanical stimulation at a strain of 0%, 5%, or 10% (5 s of stretch and 15 s of relaxation) for 10 days. The expression of MSC surface antigens (CD73, CD90, and CD105) was significantly decreased as strain increased. Mechanical stimulation inhibited the growth of UC-MSCs and slightly raised lactate dehydrogenase production. Mechanically stimulated groups produced more elastin and sulfated glycosaminoglycan than unstimulated groups and these increases were in proportion to the degree of strain. Reverse transcription-polymerase chain reaction analysis revealed that mechanical stimulation induced a significant increase in the mRNA expression of osteoblast differentiation markers. The mRNA levels of osteopontin, osteonectin, and type I collagen in the 5% and 10% strained groups were significantly higher than those in the 0% strained group. From the Western blot analysis, UC-MSCs produced bone sialoprotein and vimentin in a mechanical strain-dependent manner. Thus, cyclic mechanical loading was able to enhance the differentiation of human UC-MSCs into osteoblast-like cells as determined by osteogenic gene and protein expression. Furthermore, this finding has important implications for the use of the combination of mechanical and osteogenic differentiation media for UC-MSCs in tissue engineering and regenerative medicine.

Mesenchymal stem cells: biology, pathophysiology, translational findings, and therapeutic implications for cardiac disease

Mesenchymal stem cells (MSCs) are a prototypical adult stem cell with capacity for self-renewal and differentiation with a broad tissue distribution. Initially described in bone marrow, MSCs have the capacity to differentiate into mesoderm- and nonmesoderm-derived tissues. The endogenous role for MSCs is maintenance of stem cell niches (classically the hematopoietic), and as such, MSCs participate in organ homeostasis, wound healing, and successful aging. From a therapeutic perspective, and facilitated by the ease of preparation and immunologic privilege, MSCs are emerging as an extremely promising therapeutic agent for tissue regeneration. Studies in animal models of myocardial infarction have demonstrated the ability of transplanted MSCs to engraft and differentiate into cardiomyocytes and vasculature cells, recruit endogenous cardiac stem cells, and secrete a wide array of paracrine factors. Together, these properties can be harnessed to both prevent and reverse remodeling in the ischemically injured ventricle. In proof-of-concept and phase I clinical trials, MSC therapy improved left ventricular function, induced reverse remodeling, and decreased scar size. This article reviews the current understanding of MSC biology, mechanism of action in cardiac repair, translational findings, and early clinical trial data of MSC therapy for cardiac disease.

The CD271 expression could be alone for establisher phenotypic marker in Bone Marrow derived mesenchymal stem cells

Mesenchymal stem cells (MSCs) are of great interest for their potential use in cellular therapies. To define the population more precisely, diverse surface markers have been used. We propose here to use CD271 as the sole marker for MSCs in fresh bone marrow. We compared CD271+ populations to the presence or absence of five defined markers for MSCs: CD90+, CD105+, CD45-, CD34- and CD79. The correlations between markers were evaluated and analyzed with a Pearson's correlation test. We found that the average percentage of cells expressing the combination of markers CD90+, CD105+, CD45-, CD34- and CD79- was 0.54%, and that the average percentage average of CD271+ cells was 0.53%. The results were significant (p<0.05). The exclusive use of CD271 as a marker for MSCs from fresh samples of bone marrow appears to be highly selective. Using CD271 as the sole identification marker for MSCs could reduce costs and accelerate the process of identifying MSCs for the field of cellular therapy.

Tumour-associated fibroblasts and mesenchymal stem cells: more similarities than differences

Tumour-associated fibroblasts (TAFs) are part of the tumour stroma, providing functional and structural support for tumour progression and development. The origin and biology of TAFs are poorly understood, but within the tumour environment, TAFs become activated and secrete different paracrine and autocrine factors involved in tumorigenesis. It has been shown that bone marrow mesenchymal stem cells (MSCs) can be recruited into the tumours, where they proliferate and acquire a TAF-like phenotype. We attempted to determine to what extent TAFs characteristics in vitro juxtapose to MSCs’ definition, and we showed that TAFs and MSCs share immunophenotypic similarities, including the presence of certain cell surface molecules [human leukocyte antigen-DR subregion (HLA-DR), CD29, CD44, CD73, CD90, CD106 and CD117]; the expression of cytoskeleton and extracellular matrix proteins, such as vimentin, α-smooth muscle actin, nestin and trilineage differentiation potential (to adipocytes, chondrocytes and osteoblasts). When compared to MSCs, production of cytokines, chemokines and growth factors showed a significant increase in TAFs for vascular endothelial growth factor, transforming growth factor-β1, interleukins (IL-4, IL-10) and tumour necrosis factor α. Proliferation rate was highly increased in TAFs and fibroblast cell lines used in our study, compared to MSCs, whereas ultrastructural details differentiated the two cell types by the presence of cytoplasmic elongations, lamellar content lysosomes and intermediate filaments. Our results provide supportive evidence to the fact that TAFs derive from MSCs and could be a subset of ‘specialized’ MSCs.

Lung-derived mesenchymal stromal cell post-transplantation survival, persistence, paracrine expression, and repair of elastase-injured lung

While multipotent mesenchymal stromal cells have been recently isolated from adult lung (L-MSCs), there is very limited data on their biological properties and therapeutic potential in vivo. How L-MSCs compare with bone marrow-derived MSCs (BM-MSCs) is also unclear. In this study, we characterized L-MSC phenotype, clonogenicity, and differentiation potential, and compared L-MSCs to BM-MSCs in vivo survival, retention, paracrine gene expression, and repair or elastase injury after transplantation. L-MSCs were highly clonogenic, frequently expressed aldehyde dehydrogenase activity, and differentiated into osteocytes, chondrocytes, adipocytes, myofibroblasts, and smooth muscle cells. After intravenous injection (2 h), L-MSCs showed greater survival than BM-MSCs; similarly, L-MSCs were significantly more resistant than BM-MSCs to anchorage independent culture (4 h) in vitro. Long after transplantation (4 or 32 days), a significantly higher number of CD45(neg) L-MSCs were retained than BM-MSCs. By flow cytometry, L-MSCs expressed more intercellular adhesion molecule-1 (ICAM-1), platelet derived growth factor receptor alpha (PDGFRα), and integrin α2 than BM-MSCs; these proteins were found to modulate endothelial adherence, directional migration, and migration across Matrigel in L-MSCs. Further, L-MSCs with low ICAM-1 showed poorer lung retention and higher phagocytosis in vivo. Compared with BM-MSCs, L-MSCs expressed higher levels of several transcripts (e.g., Ccl2, Cxcl2, Cxcl10, IL-6, IL-11, Hgf, and Igf2) in vitro, although gene expression in vivo was increased by L-MSCs and BM-MSCs equivalently. Accordingly, both L-MSCs and BM-MSCs reduced elastase injury to the same extent. This study demonstrates that tissue-specific L-MSCs possess mechanisms that enhance their lung retention after intravenous transplantation, and produce substantial healing of elastase injury comparable to BM-MSCs.

Osteogenic and adipogenic differentiation potential of an immortalized fibroblast-like cell line derived from porcine peripheral blood

Primary fibroblast-like cells isolated from the peripheral blood of a healthy pig were immortalized by transduction of cells with a replication-defective retrovirus vector expressing the E6/E7 proteins of human papillomavirus type 16 (pLXSN-16E6E7). The immortalized cells grow rapidly in cell culture and exhibit a distinct cell surface phenotype that was positive for CD90, CD44, collagen I, and vimentin and negative for CD14 and MHC II. Additionally, these immortalized blood derived-fibroblast-like cells had the potential to differentiate into osteoblasts and adipocytes in vitro as evidenced by the deposition of calcium, increased alkaline phosphatase activity, upregulated osteogenic and adipogenic marker gene expression, and accumulation of fat droplets in cells when osteogenic (dexamethasone, ascorbic acid, and β-glycerophosphate) or adipogenic supplements (dexamethasone, 3-isobutyl-1-methylxanthine, indomethacin, and insulin) were added to the culture. Overall, the results suggest that the immortalized blood-derived fibroblast-like cells exhibit some of the features of mesenchymal precursor cells, which may have implications in tissue repair and remodeling process.

Immunomodulative effects of mesenchymal stem cells derived from human embryonic stem cells in vivo and in vitro

OBJECTIVE

Human embryonic stem cells (hESCs) have recently been reported as an unlimited source of mesenchymal stem cells (MSCs). The present study not only provides an identical and clinically compliant MSC source derived from hESCs (hESC-MSCs), but also describes the immunomodulative effects of hESC-MSCs in vitro and in vivo for a carbon tetrachloride (CCl(4))-induced liver inflammation model.

METHODS

Undifferentiated hESCs were treated with Rho-associated kinase (ROCK) inhibitor and induced to fibroblast-looking cells. These cells were tested for their surface markers and multilineage differentiation capability. Further more, we analyzed their immune characteristics by mixed lymphocyte reactions (MLRs) and animal experiments.

RESULTS

hESC-MSCs show a homogenous fibroblastic morphology that resembles bone marrow-derived MSCs (BM-MSCs). The cell markers and differentiation potential of hESC-MSCs are also similar to those of BM-MSCs. Unlike their original cells, hESC-MSCs possess poor immunogenicity and can survive and be engrafted into a xenogenic immunocompetent environment.

CONCLUSIONS

The hESC-MSCs demonstrate strong inhibitory effects on lymphocyte proliferation in vitro and anti-inflammatory infiltration properties in vivo. This study offers information essential to the applications of hESC-MSC-based therapies and evidence for the therapeutic mechanisms of action.

IL-4 induces differentiation of human embryonic stem cells into fibrogenic fibroblast-like cells

BACKGROUND

Fibroblast heterogeneity is recognized, and fibroblasts from diseased tissues, including those of asthmatic subjects, have functional phenotypes that differ from normal tissue. However, progenitor-progeny relationships and the factors that control fibroblast differentiation are poorly defined.

OBJECTIVE

We sought to determine whether IL-4 could alter the functional phenotype of fibroblasts during their differentiation from stem/progenitor cells.

METHODS

Using a 3-dimensional collagen gel system, we obtained embryoid bodies derived from human embryonic stem cells and recovered spindle-shaped cells consistent with fibroblasts that had differentiated in the presence or absence of IL-4.

RESULTS

IL-4-induced fibroblast-like cells were more active in contraction of collagen gels, migration, and production of fibronectin than control (without IL-4) cells. IL-4-induced cells demonstrated less expression of miR-155, which modulated contraction, migration, and fibronectin production. These differences persisted in culture without further addition of IL-4, suggesting the differentiated phenotype might be a permanent alteration.

CONCLUSION

The current study demonstrates that IL-4 induces differentiation of stem/precursor cells into fibroblast-like cells that demonstrate a more fibrogenic phenotype, which is due to reduced expression of miR-155. These findings provide a novel mechanism for the persistent abnormalities in IL-4-related diseases and a novel target to regulate tissue remodeling by fibroblasts.

Hepatocyte differentiation of human fibroblasts from cirrhotic liver in vitro and in vivo

BACKGROUND

Mesenchymal stem cells (MSCs) and fibroblasts have intimate relationships, and the phenotypic homology between fibroblasts and MSCs has been recently described. The aim of this study was to investigate the hepatic differentiating potential of human fibroblasts in cirrhotic liver.

METHODS

The phenotypes of fibroblasts in cirrhotic liver were labeled by biological methods. After that, the differentiation potential of these fibroblasts in vitro was characterized in terms of liver-specific gene and protein expression. Finally, an animal model of hepatocyte regeneration in severe combined immunodeficient (SCID) mice was created by retrorsine injection and partial hepatectomy, and the expression of human hepatocyte proteins in SCID mouse livers was checked by immunohistochemical analysis after fibroblast administration.

RESULTS

Surface immunophenotyping revealed that a minority of fibroblasts expressed markers of MSCs and hepatic epithelial cytokeratins as well as alpha-smooth muscle actin, but homogeneously expressed vimentin, desmin, prolyl 4-hydroxylase and fibronectin. These fibroblasts presented the characteristics of hepatocytes in vitro and differentiated directly into functional hepatocytes in the liver of hepatectomized SCID mice.

CONCLUSIONS

This study demonstrated that fibroblasts in cirrhotic liver have the potential to differentiate into hepatocyte-like cells in vitro and in vivo. Our findings infer that hepatic differentiation of fibroblasts may serve as a new target for reversion of liver fibrosis and a cell source for tissue engineering.

Culture media for the differentiation of mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) can be isolated from various tissues such as bone marrow aspirates, fat or umbilical cord blood. These cells have the ability to proliferate in vitro and differentiate into a series of mesoderm-type lineages, including osteoblasts, chondrocytes, adipocytes, myocytes and vascular cells. Due to this ability, MSCs provide an appealing source of progenitor cells which may be used in the field of tissue regeneration for both research and clinical purposes. The key factors for successful MSC proliferation and differentiation in vitro are the culture conditions. Hence, we here summarize the culture media and their compositions currently available for the differentiation of MSCs towards osteogenic, chondrogenic, adipogenic, endothelial and vascular smooth muscle phenotypes. However, optimal combination of growth factors, cytokines and serum supplements and their concentration within the media is essential for the in vitro culture and differentiation of MSCs and thereby for their application in advanced tissue engineering.

Human dermal fibroblasts exhibit delayed adipogenic differentiation compared with mesenchymal stem cells

Human dermal fibroblasts (FBs) express mesenchymal stem cell (MSC)-specific cell surface markers and differentiate into several cell types under appropriate conditions. Molecular mechanisms controlling the early stages of differentiation of dermal FBs and MSCs isolated from different sources have not been well studied. Here, we have analyzed the cell type-specific changes of adipose tissue-derived mesenchymal stem cells (AdMSCs) and dermal FBs in the process of differentiation into adipocytes and osteoblasts. Analysis of gene expression in the course of adipogenic differentiation of AdMSCs and FBs isolated from the same individuals revealed a time lag in the induction of adipogenesis-related genes in FBs compared with AdMSCs, a phenomenon not previously described. Further, preliminary evidence suggests that delayed adipogenesis of FBs is related to the delayed induction of preadipocyte transcription factor ZNF423 in FBs. These findings clearly show that AdMSCs and FBs have similar developmental potential but different molecular control mechanisms of initial stages of adipogenic differentiation.

Human breast milk is a rich source of multipotent mesenchymal stem cells

Putative stem cells have been isolated from various tissue fluids such as synovial fluid, amniotic fluid, menstrual blood, etc. Recently the presence of nestin positive putative mammary stem cells has been reported in human breast milk. However, it is not clear whether they demonstrate multipotent nature. Since human breast milk is a non-invasive source of mammary stem cells, we were interested in examining the nature of these stem cells. In this pursuit, we could succeed in isolating and expanding a mesenchymal stem cell-like population from human breast milk. These cultured cells were examined by immunofluorescent labeling and found positive for mesenchymal stem cell surface markers CD44, CD29, SCA-1 and negative for CD33, CD34, CD45, CD73 confirming their identity as mesenchymal stem cells. Cytoskeletal protein marker analysis revealed that these cells expressed mesenchymal stem cells markers, namely, nestin, vimentin, smooth muscle actin and also manifests presence of E-Cadherin, an epithelial to mesenchymal transition marker in their early passages. Further we tested the multipotent differentiation potential of these cells and found that they can differentiate into adipogenic, chondrogenic and oesteogenic lineage under the influence of specific differentiation cocktails. This means that these mesenchymal stem cells isolated from human breast milk could potentially be "reprogrammed" to form many types of human tissues. The presence of multipotent stem cells in human milk suggests that breast milk could be an alternative source of stem cells for autologous stem cell therapy although the significance of these cells needs to be determined.

Ovalbumin sensitization and challenge increases the number of lung cells possessing a mesenchymal stromal cell phenotype

Background

Recent studies have indicated the presence of multipotent mesenchymal stromal cells (MSCs) in human lung diseases. Excess airway smooth muscle, myofibroblasts and activated fibroblasts have each been noted in asthma, suggesting that mesenchymal progenitor cells play a role in asthma pathogenesis. We therefore sought to determine whether MSCs are present in the lungs of ovalbumin (OVA)-sensitized and challenged mice, a model of allergic airways disease.

Methods

Balb/c mice were sensitized and challenged with PBS or OVA over a 25 day period. Flow cytometry as well as colony forming and differentiation potential were used to analyze the emergence of MSCs along with gene expression studies using immunochemical analyses, quantitative polymerase chain reaction (qPCR), and gene expression beadchips.

Results

A CD45-negative subset of cells expressed Stro-1, Sca-1, CD73 and CD105. Selection for these markers and negative selection against CD45 yielded a population of cells capable of adipogenic, osteogenic and chondrogenic differentiation. Lungs from OVA-treated mice demonstrated a greater average colony forming unit-fibroblast (CFU-F) than control mice. Sorted cells differed from unsorted lung adherent cells, exhibiting a pattern of gene expression nearly identical to bone marrow-derived sorted cells. Finally, cells isolated from the bronchoalveolar lavage of a human asthma patient showed identical patterns of cell surface markers and differentiation potential.

Conclusions

In summary, allergen sensitization and challenge is accompanied by an increase of MSCs resident in the lungs that may regulate inflammatory and fibrotic responses.

In vivo bone formation by progeny of human embryonic stem cells

The derivation of osteogenic cells from human embryonic stem cells (hESCs) or from induced pluripotent stem cells for bone regeneration would be a welcome alternative to the use of adult stem cells. In an attempt to promote hESC osteogenic differentiation, cells of the HSF-6 line were cultured in differentiating conditions in vitro for prolonged periods of time ranging from 7 to 14.5 weeks, followed by in vivo transplantation into immunocompromised mice in conjunction with hydroxyapatite/tricalcium phosphate ceramic powder. Twelve different medium compositions were tested, along with a number of other variables in culture parameters. In differentiating conditions, HSF-6-derived cells demonstrated an array of diverse phenotypes reminiscent of multiple tissues, but after a few passages, acquired a more uniform, fibroblast-like morphology. Eight to 16 weeks post-transplantation, a group of transplants revealed the formation of histologically proven bone of human origin, including broad areas of multiple intertwining trabeculae, which represents by far the most extensive in vivo bone formation by the hESC-derived cells described to date. Knockout-Dulbecco's modified Eagle's medium-based media with fetal bovine serum, dexamethasone, and ascorbate promoted more frequent bone formation, while media based on α-modified minimum essential medium promoted teratoma formation in 12- to 20-week-old transplants. Transcription levels of pluripotency-related (octamer binding protein 4, Nanog), osteogenesis-related (collagen type I, Runx2, alkaline phosphatase, and bone sialoprotein), and chondrogenesis-related (collagen types II and X, and aggrecan) genes were not predictive of either bone or teratoma formation. The most extensive bone was formed by the strains that, following 4 passages in monolayer conditions, were cultured for 23 to 25 extra days on the surface of hydroxyapatite/tricalcium phosphate particles, suggesting that coculturing of hESC-derived cells with osteoconductive material may increase their osteogenic potential. While none of the conditions tested in this study, and elsewhere, ensured consistent bone formation by hESC-derived cells, our results may elucidate further directions toward the construction of bone on the basis of hESCs or an individual's own induced pluripotent stem cells.

Paracrine mechanisms of stem cell reparative and regenerative actions in the heart

Stem cells play an important role in restoring cardiac function in the damaged heart. In order to mediate repair, stem cells need to replace injured tissue by differentiating into specialized cardiac cell lineages and/or manipulating the cell and molecular mechanisms governing repair. Despite early reports describing engraftment and successful regeneration of cardiac tissue in animal models of heart failure, these events appear to be infrequent and yield too few new cardiomyocytes to account for the degree of improved cardiac function observed. Instead, mounting evidence suggests that stem cell mediated repair takes place via the release of paracrine factors into the surrounding tissue that subsequently direct a number of restorative processes including myocardial protection, neovascularization, cardiac remodeling, and differentiation. The potential for diverse stem cell populations to moderate many of the same processes as well as key paracrine factors and molecular pathways involved in stem cell-mediated cardiac repair will be discussed in this review. This article is part of a special issue entitled, "Cardiovascular Stem Cells Revisited".

Multilineage differentiation potential of fibroblast-like stromal cells derived from human skin

Adult stem cells that reside in adult tissues have been deemed to possess great potential for clinical application because of their capabilities of self-renewal and differentiation. However, the limitations such as infection risks and low isolation rate make the search for appropriate source to be continued. Here, we demonstrate isolation of progenitors from human foreskin tissue samples, which have fibroblast-like morphology and could be easily propagated for more than 50 passages. These foreskin-derived fibroblast-like stromal cells (FDSCs) expressed CD90, CD105, CD166, CD73, SH3, and SH4, which is similar to the immunophenotypes of human bone marrow-derived mesenchymal stem cells. In comparison with Hs68, the human fibroblast cell line, FDSCs are positive for CD105 and absent for CD54 expression. Further, FDSCs could be induced to differentiate into osteocytes, adipocytes, neural cells, smooth muscle cells, Schwann-like cells, and hepatocyte-like cells. Interestingly, when cultured in Dulbecco's modified Eagle's medium/F12 medium, FDSCs can form spheres with increased expression levels of fibronectin and vimentin. In conclusion, foreskin can serve as a valuable source of multipotent cells with the capabilities for endodermal, mesodermal, and ectodermal cells. Coupled with the advantages of their easy access, isolation, and propagation, these foreskin-derived stromal cells might be of potential use in future studies in stem cell differentiation and therapeutic application.

Stem cell therapy for cystic fibrosis: current status and future prospects

Although cystic fibrosis (CF), an autosomal recessive disease caused by mutations in the gene encoding for the CF transmembrane conductance regulator (CFTR), seems a good candidate for gene therapy, 15 years of intense investigation and a number of clinical trials have not yet produced a viable clinical gene-therapy strategy. In addition, the duration of gene expression has been shown to be limited, only lasting 1-4 weeks. Therefore, alternative approaches involve the search for, and use of, stem cell populations. Bone marrow contains different stem cell types, including hematopoietic stem cells and multipotent mesenchymal stromal cells. Numerous studies have now demonstrated the ability of hematopoietic stem cells and mesenchymal stromal cells to home to the lung and differentiate into epithelial cells of both the conducting airways and the alveolar region. However, engraftment of bone marrow-derived stem cells into the airways is a very inefficient process. Detailed knowledge of the cellular and molecular determinants governing homing to the lung and transformation of marrow cells into lung epithelial cells would benefit this process. Despite a very low level of engraftment of donor cells into the nose and gut, significant CFTR mRNA expression and a measurable level of correction of the electrophysiological defect were observed after transplantation of wild-type marrow cells into CF mice. It is uncertain whether this effect is due to the presence of CFTR-expressing epithelial cells derived from donor cells or to the immunomodulatory role of transplanted cells. Finally, initial studies on the usefulness of umbilical cord blood and embryonic stem cells in the generation of airway epithelial cells will be discussed in this review.

Autocrine production of TGF-beta1 promotes myofibroblastic differentiation of neonatal lung mesenchymal stem cells

We have isolated mesenchymal stem cells (MSCs) from tracheal aspirates of premature infants with respiratory distress. We examined the capacity of MSCs to differentiate into myofibroblasts, cells that participate in lung development, injury, and repair. Gene expression was measured by array, qPCR, immunoblot, and immunocytochemistry. Unstimulated MSCs expressed mRNAs encoding contractile (e.g., ACTA2, TAGLN), extracellular matrix (COL1A1 and ELN), and actin-binding (DBN1, PXN) proteins, consistent with a myofibroblast phenotype, although there was little translation into immunoreactive protein. Incubation in serum-free medium increased contractile protein (ACTA2, MYH11) gene expression. MSC-conditioned medium showed substantial levels of TGF-beta1, and treatment of serum-deprived cells with a type I activin receptor-like kinase inhibitor, SB-431542, attenuated the expression of genes encoding contractile and extracellular matrix proteins. Treatment of MSCs with TGF-beta1 further induced the expression of mRNAs encoding contractile (ACTA2, MYH11, TAGLN, DES) and extracellular matrix proteins (FN1, ELN, COL1A1, COL1A2), and increased the protein expression of alpha-smooth muscle actin, myosin heavy chain, and SM22. In contrast, human bone marrow-derived MSCs failed to undergo TGF-beta1-induced myofibroblastic differentiation. Finally, primary cells from tracheal aspirates behaved in an identical manner as later passage cells. We conclude that human neonatal lung MSCs demonstrate an mRNA expression pattern characteristic of myofibroblast progenitor cells. Autocrine production of TGF-beta1 further drives myofibroblastic differentiation, suggesting that, in the absence of other signals, fibrosis represents the "default program" for neonatal lung MSC gene expression. These data are consistent with the notion that MSCs play a key role in neonatal lung injury and repair.

Isolation and characterization of chicken lung mesenchymal stromal cells and their susceptibility to avian influenza virus

In this study, we isolated and characterized mesenchymal stromal cells (MSCs) from the lungs of 1- to 2-week-old chickens. Microscopically, the cultured cells showed fibroblast-like morphology. Phenotypically these cells expressed CD44, CD90, CD105 and the transcription factor PouV, which has been shown to be critical for stem cell self-renewal and pluripotency. The multipotency of chicken MSCs was demonstrated by their ability to undergo adipogenic and osteogenic differentiation. Like chicken bone marrow MSCs and mammalian MSCs, chicken lung MSCs had immunoregulatory activity and profoundly suppressed the proliferative capacity of T cells in response to a mitogenic stimulus. Next, we examined the susceptibility of these cells to H1N1 and H9N5 avian influenza (AI) viruses. The lung MSCs were shown to express known influenza virus alpha-2,3 and alpha-2,6 sialic acid receptors and to support replication of both the avian H1N1 and avian H9N5 influenza strains. Viral infection of MSCs resulted in cell lysis and cytokine and chemokine production. Further characterization of lung MSCs in chicken and other mammalian species may help in understanding the pathogenesis of infectious and non-infectious lung diseases and the mechanisms of lung injury repair.

Mesenchymal stem cells as therapeutic tools and gene carriers in liver fibrosis and hepatocellular carcinoma

Mesenchymal stem (stromal) cells (MSCs) are a source of circulating progenitors that are able to generate cells of all mesenchymal lineages and to cover cellular demands of injured tissues. The extent of their transdifferentiation plasticity remains controversial. Cells with MSC properties have been obtained from diverse tissues after purification and expansion in vitro. These cellular populations are heterogeneous and under certain conditions show pluripotent-like properties. MSCs present immunosuppressive and anti-inflammatory features and high migratory capacity toward inflamed or remodeling tissues. In this study we review available data regarding factors and signaling axes involved in the chemoattraction and engraftment of MSCs to an injured tissue or to a tissue undergoing active remodeling. Moreover, experimental evidence in support of uses of MSCs as vehicles of therapeutic genes is discussed. Because of its regenerative capacity and its particular immune properties, the liver is a good model to analyze the potential of MSC-based therapies. Finally, the potential application of MSCs and genetically modified MSCs in liver fibrosis and hepatocellular carcinoma (HCC) is proposed in view of available evidence.

The natural and engineered 3D microenvironment as a regulatory cue during stem cell fate determination

The concept of using stem cells as self-renewing sources of healthy cells in regenerative medicine has existed for decades, but most applications have yet to achieve clinical success. A main reason for the lack of successful stem cell therapies is the difficulty in fully recreating the maintenance and control of the native stem cell niche. Improving the performance of transplanted stem cells therefore requires a better understanding of the cellular mechanisms guiding stem cell behavior in both native and engineered three-dimensional (3D) microenvironments. Most techniques, however, for uncovering mechanisms controlling cell behavior in vitro have been developed using 2D cell cultures and are of limited use in 3D environments such as engineered tissue constructs. Deciphering the mechanisms controlling stem cell fate in native and engineered 3D environments, therefore, requires rigorous quantitative techniques that permit mechanistic, hypothesis-driven studies of cell-microenvironment interactions. Here, we review the current understanding of 2D and 3D stem cell control mechanisms and propose an approach to uncovering the mechanisms that govern stem cell behavior in 3D.

Immunohistochemical localization of the STRO-1 antigen in developing rat teeth by light microscopy and electron microscopy

STRO-1 is a cell-surface antigen. A cell population that is positive for the anti-STRO-1 antibody has been shown to contain mesenchymal stem cells. STRO-1-positive cells have been reported to reside in dental pulp and periodontal ligaments as well as in bone marrow. However, the tissue localization of STRO-1 in developing teeth is not clear. The present study was designed to investigate the spatiotemporal localization of STRO-1 in developing rat teeth by immunohistochemistry using light microscopy and electron microscopy. Wistar rats at ages 2, 3, 6 and 12 weeks postnatum and embryos at 18 days postcoitum were fixed with 4% paraformaldehyde. Mandibles and maxillae were resected and decalcified in 10% EDTA. The specimens were embedded in paraffin, and sections were cut and processed for immunohistochemistry using the anti-STRO-1 antibody. Selected specimens were frozen, sectioned and processed for immunoelectron microscopy. Immunoreactions for STRO-1 were identified in some bone marrow cells. Some odontoblasts and dental pulp cells showed positive immunoreactivity in developing rat tooth crowns and roots. Alveolar osteoblasts, cementoblasts and periodontal ligament cells were also immunoreactive. Electron microscopy localized the antigen in plasma membrane and some vesicles in dental pulp cells and odontoblasts. The study suggests that the STRO-1 antigen is involved in the differentiation of mesenchymal cell lineages and formation of the matrix in dental tissues.

Cutaneous mesenchymal stem cells: status of current knowledge, implications for dermatopathology

Stem cell biology is currently making its impact on medicine, which will probably increase over the next decades. It not only influences our therapeutic thinking caused by the enormous plasticity of stem cells but also affects diagnostic and conceptual aspects of dermatopathology. Although our knowledge of the keratinocytic stem cells located within the follicular bulge has exploded exponentially since their discovery in 1990, the concept of cutaneous mesenchymal stem cells (MSCs) is new. Described initially in 2001 in mice, MSCs later were also found in the human dermis. The connective tissue sheath and the papilla of the hair follicle probably represent the anatomical niche for cutaneous MSCs. In line with the cancer stem cell hypothesis, mutations of these cells may be the underlying basis of mesenchymal skin neoplasms, such as dermatofibrosarcoma protuberans. Furthermore, research on cutaneous MSCs may impact our thinking on the interaction of the epithelial component of skin neoplasms with their surrounding stroma. We are only in the early stages to recognize the importance of the potential contributions of cutaneous MSC research to dermatopathology, but it is not inconceivable to assume that they could be tremendous, paralleling the early discovery of the follicular bulge as a stem cell niche.

Phenotypic characterization of distinct human bone marrow-derived MSC subsets

Very recently, we identified two distinct mesenchymal stem cell (MSC) subsets in primary bone marrow (BM) that differ in their expression pattern (CD271(bright)MSCA-1(dim)CD56(+) and CD271(bright)MSCA-1(bright)CD56(-)) and morphology as well as in their clonogenic and differentiation capacity. Here we analyzed the cell surface antigen expression in these subsets in more detail and compared the profiles with the expression pattern on cultured MSCs. Most of the tested antigens, including CD13, CD15, CD73, CD140b, CD144, CD146, and CD164, are expressed at similar levels in both primary BM populations. However, a number of markers were differentially expressed. Of these, CD166 (ALCAM), CD200, and CD106 (VCAM-1) showed an almost selective expression on either CD271(bright)MSCA-1(dim)CD56(+) (increased CD166 and CD200 expression) or CD271(bright)MSCA-1(bright)CD56(-) (increased CD106 expression) MSCs, respectively. Additional markers with elevated expression on CD56(+) MSCs include F9-3C2F1, HEK-3D3, HEK5-1B3, and W1C3 antigens, whereas CD10, CD26, CD106, 7C5G1, 9A3G2, 56A1C2, 66E2D11, HEK-3D6, HEK4-1A1, HEK4-2D6, W1D6, W4A5, W7C6, and W8B2 (MSCA-1) antigens showed increased expression in the CD56(-) population. The majority of the analyzed markers found on primary MSCs were also expressed on cultured MSCs. However, in contrast to primary MSCs, HEK7-1C4, W1C3, W1D6, and W4A5 antigens were absent on the cultured counterparts. 7G5G1 and 9A3G2 antigens showed reduced, and HEK-3D6, F9-3C2, and HEK-3D3 showed increased expression on cultured cells. The extended knowledge about the phenotype of the two subsets and the identification of novel MSC markers may result in the isolation of attractive starting populations for applications in regenerative medicine.

Identification of mesenchymal stromal cells in human lung parenchyma capable of differentiating into aquaporin 5-expressing cells

The lack of effective therapies for end-stage lung disease validates the need for stem cell-based therapeutic approaches as alternative treatment options. In contrast with exogenous stem cell sources, the use of resident progenitor cells is advantageous considering the fact that the lung milieu is an ideal and familiar environment, thereby promoting the engraftment and differentiation of transplanted cells. Recent studies have shown the presence of multipotent 'mesenchymal stem cells' in the adult lung. The majority of these reports are, however, limited to animal models, and to date, there has been no report of a similar cell population in adult human lung parenchyma. Here, we show the identification of a population of primary human lung parenchyma (pHLP) mesenchymal stromal cells (MSCs) derived from intraoperative normal lung parenchyma biopsies. Surface and intracellular immunophenotyping by flow cytometry revealed that cultures do not contain alveolar type I epithelial cells or Clara cells, and are devoid of the following hematopoietic markers: CD34, CD45 and CXCR4. Cells show an expression pattern of surface antigens characteristic of MSCs, including CD73, CD166, CD105, CD90 and STRO-1. As per bone marrow MSCs, our pHLP cells have the ability to differentiate along the adipogenic, osteogenic and chondrogenic mesodermal lineages when cultured in the appropriate conditions. In addition, when placed in small airway growth media, pHLP cell cultures depict the expression of aquaporin 5 and Clara cell secretory protein, which is identified with that of alveolar type I epithelial cells and Clara cells, respectively, thereby exhibiting the capacity to potentially differentiate into airway epithelial cells. Further investigation of these resident cells may elucidate a therapeutic cell population capable of lung repair and/or regeneration.