Derivation of functional smooth muscle cells from multipotent human hair follicle mesenchymal stem cells

Human hair follicle-derived mesenchymal stem cells promote tendon repair in a rabbit Achilles tendinopathy model

BACKGROUND

Hair follicles are easily accessible and contain stem cells with different developmental origins, including mesenchymal stem cells (MSCs), that consequently reveal the potential of human hair follicle (hHF)-derived MSCs in repair and regeneration. However, the role of hHF-MSCs in Achilles tendinopathy (AT) remains unclear. The present study investigated the effects of hHF-MSCs on Achilles tendon repair in rabbits.

METHODS

First, we extracted and characterized hHF-MSCs. Then, a rabbit tendinopathy model was constructed to analyze the ability of hHF-MSCs to promote repair in vivo . Anatomical observation and pathological and biomechanical analyses were performed to determine the effect of hHF-MSCs on AT, and quantitative real-time polymerase chain reaction, enzyme-linked immunosorbent assay, and immunohistochemical staining were performed to explore the molecular mechanisms through which hHF-MSCs affects AT. Furthermore, statistical analyses were performed using independent sample t test, one-way analysis of variance (ANOVA), and one-way repeated measures multivariate ANOVA as appropriate.

RESULTS

Flow cytometry, a trilineage-induced differentiation test, confirmed that hHF-derived stem cells were derived from MSCs. The effect of hHF-MSCs on AT revealed that the Achilles tendon was anatomically healthy, as well as the maximum load carried by the Achilles tendon and hydroxyproline proteomic levels were increased. Moreover, collagen I and III were upregulated in rabbit AT treated with hHF-MSCs (compared with AT group; P  < 0.05). Analysis of the molecular mechanisms revealed that hHF-MSCs promoted collagen fiber regeneration, possibly through Tenascin-C (TNC) upregulation and matrix metalloproteinase (MMP)-9 downregulation.

CONCLUSIONS

hHF-MSCs can be a treatment modality to promote AT repair in rabbits by upregulating collagen I and III. Further analysis revealed that treatment of AT using hHF-MSCs promoted the regeneration of collagen fiber, possibly because of upregulation of TNC and downregulation of MMP-9, thus suggesting that hHF-MSCs are more promising for AT.

Ficoll density gradient sedimentation isolation of pelage hair follicle mesenchymal stem cells from adult mouse back skin: a novel method for hair follicle mesenchymal stem cells isolation

Background

Hair follicle mesenchymal stem cells (HF-MSCs) have great potential for cell therapy. Traditional method to isolate whisker HF-MSC is time-consuming and few in cell numbers. How to quickly and conveniently obtain a large number of HF-MSC for experimental research is a problem worth exploring.

Methods

Two-step Ficoll Density Gradient Sedimentation (FDGS) was performed to isolate pelage HF-MSC from adult mice. The characteristic of the isolated cells was identified and compared with whisker HF-MSC by immunofluorescence staining, flow cytometry, three-lineage differentiation and hair follicle reconstruction. Pelage HF-MSC and exosomes were injected into the dorsal skin of mice as well as hair follicle organ culture to explore its role in promoting hair growth. The cells and exosomes distribution were located by immunofluorescence staining.

Results

Isolated pelage HF-MSC expressed similar markers (ALP, Versican, NCAM, Nestin), showed similar growth pattern, possessed similar mesenchymal stem cells function and hair follicle induction ability as whisker HF-MSC. A large number of cells can be obtained with fewer mice compared to traditional method. Injected pelage HF-MSC promoted hair growth by secreting exosomes.

Conclusion

A large number of Pelage HF-MSC can be isolated by FDGS, which can promote hair growth by secreting exosomes which may target the dermal papilla and hair matrix region of host hair follicle.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03051-3.

Current Progress in Vascular Engineering and Its Clinical Applications

Coronary heart disease (CHD) is caused by narrowing or blockage of coronary arteries due to atherosclerosis. Coronary artery bypass grafting (CABG) is widely used for the treatment of severe CHD cases. Although autologous vessels are a preferred choice, healthy autologous vessels are not always available; hence there is a demand for tissue engineered vascular grafts (TEVGs) to be used as alternatives. However, producing clinical grade implantable TEVGs that could healthily survive in the host with long-term patency is still a great challenge. There are additional difficulties in producing small diameter (<6 mm) vascular conduits. As a result, there have not been TEVGs that are commercially available. Properties of vascular scaffolds such as tensile strength, thrombogenicity and immunogenicity are key factors that determine the biocompatibility of TEVGs. The source of vascular cells employed to produce TEVGs is a limiting factor for large-scale productions. Advanced technologies including the combined use of natural and biodegradable synthetic materials for scaffolds in conjunction with the use of mesenchyme stem cells or induced pluripotent stem cells (iPSCs) provide promising solutions for vascular tissue engineering. The aim of this review is to provide an update on various aspects in this field and the current status of TEVG clinical applications.

Tissue Engineering and Regeneration of the Human Hair Follicle in Androgenetic Alopecia: Literature Review

Androgenetic alopecia (AGA) is an androgen-dependent process and represents the most frequent non-scarring alopecia. Treatments for AGA do not always achieve a satisfactory result for the patient, and sometimes cause side effects that lead to discontinuation of treatment. AGA therapeutics currently includes topical and oral drugs, as well as follicular unit micro-transplantation techniques. Tissue engineering (TE) is postulated as one of the possible future solutions to the problem and aims to develop fully functional hair follicles that maintain their cyclic rhythm in a physiological manner. However, despite its great potential, reconstitution of fully functional hair follicles is still a challenge to overcome and the knowledge gained of the key processes in hair follicle morphogenesis and biology has not yet been translated into effective replacement therapies in clinical practice. To achieve this, it is necessary to research and develop new approaches, techniques and biomaterials. In this review, present and emerging hair follicle bioengineering strategies are evaluated. The current problems of these bioengineering techniques are discussed, as well as the advantages and disadvantages, and the future prospects for the field of TE and successful hair follicle regeneration.

Hair follicle-derived mesenchymal stem cells decrease alopecia areata mouse hair loss and reduce inflammation around the hair follicle

Background

Alopecia areata (AA) is a common autoimmune hair loss disease with increasing incidence. Corticosteroids are the most widely used for hair loss treatment; however, long-term usage of hormonal drugs is associated with various side effects. Mesenchymal stem cells (MSCs) therapy has been studied extensively to curb autoimmune diseases without affecting immunity against diseases.

Methods

Hair follicle-derived MSCs (HF-MSCs) were harvested from the waste material of hair transplants, isolated and expanded. The therapeutic effect of HF-MSCs for AA treatment was investigated in vitro AA-like hair follicle organ model and in vivo C3H/HeJ AA mice model.

Results

AA-like hair follicle organ in vitro model was successfully established by pre-treatment of mouse vibrissa follicles by interferon-γ (IFN-γ). The AA-like symptoms were relieved when IFN-γ induced AA in vitro model was co-cultured with HF-MSC for 2 days. In addition, when skin grafted C3H/HeJ AA mice models were injected with 10⁶ HF-MSCs once a week for 3 weeks, the transcription profiling and immunofluorescence analysis depicted that HF-MSCs treatment significantly decreased mouse hair loss and reduced inflammation around HF both in vitro and in vivo.

Conclusions

This study provides a new therapeutic approach for alopecia areata based on HF-MSCs toward its future clinical application.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02614-0.

Hair Follicle Stem Cells for Tissue Regeneration

With the positive outcomes of various cell therapies currently under pre-clinical and clinical studies, there is a significant interest in novel stem cell sources with unique therapeutic properties. Studies over the past two decades or so demonstrated the feasibility to isolate multipotent/pluripotent stem cells from hair follicles. The easy accessibility, high proliferation and differentiation ability as well as lack of ethical concerns associated with this stem cell source make hair follicle stem cells (HFSCs) attractive candidate for cell therapy and tissue engineering. This review discusses the various stem cell types identified in rodent and human hair follicles and ongoing studies on the potential use of HFSCs for skin, bone, cardio-vascular, and nerve tissue engineering.

MEF/KSF-conditioned culture medium: An effective method for in vitro culture of mouse dermal papilla cells with osteogenic differentiation potential

Hair follicle stem cells are pluripotent and have a self-renewal capacity and multi-differentiation potential in vitro. As hair follicle stem cells can be easily sampled from the skin and hair of clinical patients at a considerable quantity, these cells have potential applications in wound repair and skin tissue engineering. Effective approaches for the in vitro culture and amplification of mouse hair follicle stem cells, as well as the in vitro osteogenic differentiation potential and cell source when obtaining mouse-separated cells were examined. Serial subculture was performed in different culture systems. Cell source was detected based on the relevant surface markers derived from mouse hair follicles at the gene and protein levels, and the differential potential was determined. The proliferative ability of hair follicle-derived stem cells obtained from mouse embryonic fibroblast (MEF)/keratinocyte serum-free medium (KSF)-conditioned medium was the highest among all culture systems. The induced group had a stronger osteogenic differentiation potential compared with the non-induced group, indicating that the cells obtained from MEF/KSF-conditioned medium were cells derived from the hair follicle dermal papilla. Therefore, the strong osteogenic differentiation potential of the hair follicle-derived mesenchymal stem cells was screened with MEF/KSF-conditioned culture medium following amplification, and biological characteristics similar to those of hair follicle dermal papilla cells were observed.

Human Dental Pulp-Derived Mesenchymal Stem Cell Potential to Differentiate into Smooth Muscle-Like Cells In Vitro

Previous studies have shown that mesenchymal stem cells (MSCs) derived from various tissue sources can be differentiated into smooth muscle-like cells (SMLCs) in vitro. In this paper, dental pulp-derived mesenchymal stem cells (DPSCs) were evaluated for their differentiation ability towards smooth muscle-like cells (SMLCs) under the effect of widely used cytokines (TGF-β1 and PDGF-BB) with special focus on different culturing environments. For this purpose, both the commercially used culturing plates (Norm-c) and 0.1% gelatin-precoated (Gel-c) plates were used. Isolated cells displayed plastic adherence, pluripotency and cell surface marker profiling, and adipogenic and osteogenic differentiation potential with lineage specific marker expression. Differentiated cells induced under different culturing plates showed successful differentiation into SMLCs by positively expressing smooth muscle cell (SMC) specific markers both at the mRNA and protein levels. Gelatin coating could substantially enhance DPSC differentiation potential than Norm-c-induced cells. However, the absence of mature marker MHY-11 by immunostaining results from all treatment groups further indicated the development of immature and synthetic SMLCs. Finally, it was concluded that DPSC differentiation ability into SMLCs can be enhanced under cytokine treatment as well as by altering the cellular niche by precoating the culturing plates with suitable substrates. However, to get fully functional, contractile, and mature SMLCs, still many different cytokine cocktail combinations and more suitable coating substrates will be needed.

RNA-seq reveals tight junction-relevant erythropoietic fate induced by OCT4 in human hair follicle mesenchymal stem cells

BACKGROUND

Human hair follicle mesenchymal stem cells (hHFMSCs) isolated from hair follicles possess multilineage differentiation potential. OCT4 is a gene critically associated with pluripotency properties. The cell morphology and adhesion of hHFMSCs significantly changed after transduction of OCT4 and two subpopulations emerged, including adherent cells and floating cell. Floating cells cultured in hematopoietic induction medium and stimulated with erythropoetic growth factors could transdifferentiate into mature erythrocytes, whereas adherent cells formed negligible hematopoietic colonies. The aim of this study was to reveal the role of cell morphology and adhesion on erythropoiesis induced by OCT4 in hHFMSCs and to characterize the molecular mechanisms involved.

METHODS

Floating cell was separated from adherent cell by centrifugation of the upper medium during cell culture. Cell size was observed through flow cytometry and cell adhesion was tested by disassociation and adhesion assays. RNA sequencing was performed to detect genome-wide transcriptomes and identify differentially expressed genes. GO enrichment analysis and KEGG pathway analysis were performed to analysis the functions and pathways enriched by differentially expressed genes. The expression of tight junction core members was verified by qPCR and Western blot. A regulatory network was constructed to figure out the relationship between cell adhesin, cytoskeleton, pluripotency, and hematopoiesis.

RESULTS

The overexpression of OCT4 influenced the morphology and adhesion of hHFMSCs. Transcripts in floating cells and adherent cells are quite different. Data analysis showed that upregulated genes in floating cells were mainly related to pluripotency, germ layer development (including hematopoiesis lineage development), and downregulated genes were mainly related to cell adhesion, cell junctions, and the cytoskeleton. Most molecules of the tight junction (TJ) pathway were downregulated and molecular homeostasis of the TJ was disturbed, as CLDNs were disrupted, and JAMs and TJPs were upregulated. The dynamic expression of cell adhesion-related gene E-cadherin and cytoskeleton-related gene ACTN2 might cause different morphology and adhesion. Finally, a regulatory network centered to OCT4 was constructed, which elucidated that he TJ pathway critically bridges pluripotency and hematopoiesis in a TJP1-dependent way.

CONCLUSIONS

Regulations of cell morphology and adhesion via the TJ pathway conducted by OCT4 might modulate hematopoiesis in hHFMSCs, thus developing potential mechanism of erythropoiesis in vitro.

Influence of culture media on the derivation and phenotype of fetal-derived placental mesenchymal stem/stromal cells across gestation

INTRODUCTION

Derivation of pure fetal placental mesenchymal stem/stromal cells (pMSCs) is key to understand their role in placental development. However, isolated pMSCs are often contaminated by maternal-derived decidual MSCs (dMSCs). EGM-2 medium promotes the derivation of term fetal pMSCs, but the extent of first-trimester maternal pMSC contamination remains unclear. Culture media can also affect MSC phenotype. Here, we examined the effects of culture media on maternal pMSC contamination and fetal pMSC phenotype across gestation.

METHODS

pMSCs were derived from first-trimester or term placentae in advanced-DMEM/F12 medium or EGM-2 medium. Proportions of maternal (XX) and fetal (XY) cells in male pMSC cultures were determined by fluorescence in-situ hybridization. pMSC phenotype was analysed by flow cytometry, immunohistochemistry and Alamar blue proliferation assays.

RESULTS

When derived in advanced-DMEM/F12, all first trimester pMSC isolates exhibited maternal contamination (>72% XX cells, n = 5), whilst 7/9 term pMSC isolates were >98% fetal. When derived in EGM-2, all first trimester (n = 4) and term (n = 9) pMSC isolates contained 95-100% fetal cells. Fetal pMSCs in EGM-2 proliferated 2-fold (first-trimester) or 4-fold (term) faster than those in advanced-DMEM/F12 (p < 0.05, n = 3). Fetal pMSCs in both media expressed the generic MSC marker profile (CD90⁺, CD105+, CD73⁺, CD31-, CD34-, CD144-). However, pMSCs transferred from EGM-2 to advanced-DMEM/F12 increased expression of smooth muscle cell markers calponin and α-smooth muscle actin, and decreased expression of the vascular cell marker VEGFR2 (n = 3).

CONCLUSIONS

Deriving first-trimester pMSC in EGM-2 dramatically reduces maternal dMSC contamination. Media affects fetal pMSC phenotype, and careful consideration should be given to application specific culture conditions.

Human hair follicle-derived mesenchymal stem cells: Isolation, expansion, and differentiation

Hair follicles are easily accessible skin appendages that protect against cold and potential injuries. Hair follicles contain various pools of stem cells, such as epithelial, melanocyte, and mesenchymal stem cells (MSCs) that continuously self-renew, differentiate, regulate hair growth, and maintain skin homeostasis. Recently, MSCs derived from the dermal papilla or dermal sheath of the human hair follicle have received attention because of their accessibility and broad differentiation potential. In this review, we describe the applications of human hair follicle-derived MSCs (hHF-MSCs) in tissue engineering and regenerative medicine. We have described protocols for isolating hHF-MSCs from human hair follicles and their culture condition in detail. We also summarize strategies for maintaining hHF-MSCs in a highly proliferative but undifferentiated state after repeated in vitro passages, including supplementation of growth factors, 3D suspension culture technology, and 3D aggregates of MSCs. In addition, we report the potential of hHF-MSCs in obtaining induced smooth muscle cells and tissue-engineered blood vessels, regenerated hair follicles, induced red blood cells, and induced pluripotent stem cells. In summary, the abundance, convenient accessibility, and broad differentiation potential make hHF-MSCs an ideal seed cell source of regenerative medical and cell therapy.

Culture and Differentiation of Human Hair Follicle Dermal Papilla Cells in a Soft 3D Self-Assembling Peptide Scaffold

Hair follicle dermal papilla cells (HFDPC) are a specialized cell population located in the bulge of the hair follicle with unique characteristics such as aggregative behavior and the ability to induce new hair follicle formation. However, when expanded in conventional 2D monolayer culture, their hair inductive potency is rapidly lost. Different 3D culture techniques, including cell spheroid formation, have been described to restore, at least partially, their original phenotype, and therefore, their hair inductive ability once transplanted into a recipient skin. Moreover, hair follicle dermal papilla cells have been shown to differentiate into all mesenchymal lineages, but their differentiation potential has only been tested in 2D cultures. In the present work, we have cultured HFDPC in the 3D self-assembling peptide scaffold RAD16-I to test two different tissue engineering scenarios: restoration of HFDPC original phenotype after cell expansion and osteogenic and adipogenic differentiation. Experimental results showed that the 3D environment provided by RAD16-I allowed the restoration of HFDPC signature markers such as alkaline phosphatase, versican and corin. Moreover, RAD16-I supported, in the presence of chemical inductors, three-dimensional osteogenic and adipogenic differentiation. Altogether, this study suggests a potential 3D culture platform based on RAD16-I suitable for the culture, original phenotype recovery and differentiation of HFDPC.

Engineering the mode of morphogenetic signal presentation to promote branching from salivary gland spheroids in 3D hydrogels

Previously we developed a fibrin hydrogel (FH) decorated with laminin-111 peptides (L_1p-FH) and supports three-dimensional (3D) gland microstructures containing polarized acinar cells. Here we expand on these results and show that co-culture of rat parotid Par-C10 cells with mesenchymal stem cells produces migrating branches of gland cells into the L1_p-FH and we identify FGF-7 as the principal morphogenetic signal responsible for branching. On the other hand, another FGF family member and gland morphogen, FGF-10 increased proliferation but did not promote migration and therefore, limited the number and length of branched structures grown into the gel. By controlling the mode of growth factor presentation and delivery, we can control the length and cellularity of branches as well as formation of new nodes/clusters within the hydrogel. Such spatial delivery of two or more morphogens may facilitate engineering of anatomically complex tissues/mini organs such as salivary glands that can be used to address developmental questions or as platforms for drug discovery. STATEMENT OF SIGNIFICANCE: Hyposalivation leads to the development of a host of oral diseases. Current treatments only provide temporary relief. Tissue engineering may provide promising permanent solutions. Yet current models are limited to salivary spheroids with no branching networks. Branching structures are vital to an effective functioning gland as they increase the surface area/glandular volume ratio of the tissue, allowing a higher output from the small-sized gland. We describe a strategy that controls branch network formation in salivary glands that is a key in advancing the field of salivary gland tissue engineering.

NANOG Attenuates Hair Follicle-Derived Mesenchymal Stem Cell Senescence by Upregulating PBX1 and Activating AKT Signaling

Stem cells derived from elderly donors or harvested by repeated subculture exhibit a marked decrease in proliferative capacity and multipotency, which not only compromises their therapeutic potential but also raises safety concerns for regenerative medicine. NANOG-a well-known core transcription factor-plays an important role in maintaining the self-renewal and pluripotency of stem cells. Unfortunately, the mechanism that NANOG delays mesenchymal stem cell (MSC) senescence is not well-known until now. In our study, we showed that both ectopic NANOG expression and PBX1 overexpression (i) significantly upregulated phosphorylated AKT (p-AKT) and PARP1; (ii) promoted cell proliferation, cell cycle progression, and osteogenesis; (iii) reduced the number of senescence-associated-β-galactosidase- (SA-β-gal-) positive cells; and (iv) downregulated the expression of p16, p53, and p21. Western blotting and dual-luciferase activity assays showed that ectopic NANOG expression significantly upregulated PBX1 expression and increased PBX1 promoter activity. In contrast, PBX1 knockdown by RNA interference in hair follicle- (HF-) derived MSCs that were ectopically expressing NANOG resulted in the significant downregulation of p-AKT and the upregulation of p16 and p21. Moreover, blocking AKT with the PI3K/AKT inhibitor LY294002 or knocking down AKT via RNA interference significantly decreased PBX1 expression, while increasing p16 and p21 expression and the number of SA-β-gal-positive cells. In conclusion, our findings show that NANOG delays HF-MSC senescence by upregulating PBX1 and activating AKT signaling and that a feedback loop likely exists between PBX1 and AKT signaling.

PBX homeobox 1 enhances hair follicle mesenchymal stem cell proliferation and reprogramming through activation of the AKT/glycogen synthase kinase signaling pathway and suppression of apoptosis

BACKGROUND

PBX homeobox 1 (PBX1) is involved in the maintenance of the pluripotency of human embryonic and hematopoietic stem cells; however, the effects of PBX1 in the self-renewal and reprogramming of hair follicle mesenchymal stem cells (HF-MSCs) are unclear. The AKT/glycogen synthase kinase (GSK) 3β pathway regulates cell metabolism, proliferation, apoptosis, and reprogramming, and p16 and p21, which act downstream of this pathway, regulate cell proliferation, cell cycle, and apoptosis induced by reprogramming. Here, we aimed to elucidate the roles of PBX1 in regulating the proliferation and reprogramming of HF-MSCs.

METHODS

A lentiviral vector designed to carry the PBX1 sequence or PBX1 short hairpin RNA sequence was used to overexpress or knock down PBX1. The roles of PBX1 in proliferation and apoptosis were investigated by flow cytometry. Real-time polymerase chain reaction was performed to evaluate pluripotent gene expression. Dual-luciferase reporter assays were performed to examine the transcriptional activity of the NANOG promoter. Western blotting was performed to identify the molecules downstream of PBX1 involved in proliferation and reprogramming. Caspase3 activity was detected to assess HF-MSC reprogramming. The phosphatidylinositol 3-kinase/AKT inhibitor LY294002 was used to inhibit the phosphorylation and activity of AKT.

RESULTS

Overexpression of PBX1 in HF-MSCs increased the phosphorylation of AKT and nuclear translocation of β-catenin, resulting in the progression of the cell cycle from G0/G1 to S phase. Moreover, transfection with a combination of five transcription factors (SOMKP) in HF-MSCs enhanced the formation of alkaline phosphatase-stained colonies compared with that in HF-MSCs transfected with a combination of four transcription factors (SOMK). PBX1 upregulated Nanog transcription by activating the promoter and promoted the expression of endogenous SOX2 and OCT4. Furthermore, PBX1 expression activated the AKT/glycogen synthase kinase (GSK) 3β pathway and reduced apoptosis during the early stages of reprogramming. Inhibition of phospho-AKT or knockdown of PBX1 promoted mitochondrion-mediated apoptosis and reduced reprogramming efficiency.

CONCLUSIONS

PBX1 enhanced HF-MSC proliferation, and HF-MSCs induced pluripotent stem cells (iPSC) generation by activating the AKT/GSK3β signaling pathway. During the reprogramming of HF-MSCs into HF-iPSCs, PBX1 activated the NANOG promoter, upregulated NANOG, and inhibited mitochondrion-mediated apoptosis via the AKT/GSK3β pathway during the early stages of reprogramming.

Vascular aging: Molecular mechanisms and potential treatments for vascular rejuvenation

Aging is the main risk factor contributing to vascular dysfunction and the progression of vascular diseases. In this review, we discuss the causes and mechanisms of vascular aging at the tissue and cellular level. We focus on Endothelial Cell (EC) and Smooth Muscle Cell (SMC) aging due to their critical role in mediating the defective vascular phenotype. We elaborate on two categories that contribute to cellular dysfunction: cell extrinsic and intrinsic factors. Extrinsic factors reflect systemic or environmental changes which alter EC and SMC homeostasis compromising vascular function. Intrinsic factors induce EC and SMC transformation resulting in cellular senescence. Replenishing or rejuvenating the aged/dysfunctional vascular cells is critical to the effective repair of the vasculature. As such, this review also elaborates on recent findings which indicate that stem cell and gene therapies may restore the impaired vascular cell function, reverse vascular aging, and prolong lifespan.

Hair follicle-derived mesenchymal cells support undifferentiated growth of embryonic stem cells

The aim of the present study was to investigate whether feeder layers composed of human hair follicle-derived mesenchymal stem cells (hHFDCs) are able to support human embryonic stem cells (hESCs). hHFDCs and mouse embryonic fibroblasts (MEFs) were isolated and cultured in Dulbecco's modified Eagle's medium (DMEM)/F-12 and low-glucose DMEM, respectively. hHFDCs were passaged three times and subsequently characterized. hHFDCs and MEFs were mitotically inactivated with mitomycin C for 3 h prior to co-culture with H9-hESCs. hESCs were initially established on a mouse feeder layer, subsequently transferred onto a human feeder layer and split every 5 days. Cell morphology, expression of specific 'undifferentiation' markers and growth factors, and the differentiation capacity of hESCs grown on the hHFDC feeder layer were analyzed. hHFDCs are adherent to plastic, possess the classic mesenchymal stem cell phenotype [they express cluster of differentiation (CD)90, CD73 and CD105] and are able to differentiate into adipocytes, chondroblasts and osteocytes, indicating that these cells are multipotent. Population-doubling time analysis revealed that hHFDCs rapidly proliferate over 34.5 h. As a feeder layer, hHFDC behaved similarly to MEF in maintaining the morphology of hESCs. The results of alkaline phosphatase activity, reverse transcription-quantitative polymerase chain reaction analysis of the expression of pluripotency transcription factors [octamer-binding transcription factor 4 (Oct4), Nanog and sex determining region Y-box 2], and immunofluorescence assays of markers (stage-specific embryonic antigen-4 and Oct4) in hESCs co-cultured over hHFDC, indicated that the undifferentiated state of hESCs was preserved. No change in the level of growth factor transcripts (bone morphogenetic protein 4, fibroblast growth factor-2, vascular endothelial growth factor, Pigment epithelium-derived factor and transforming growth factor-β1) was detected for either feeder layer prior to or following inactivation. Similar phenotypes of embryoid body formation, size and morphology were observed in the hHFDC and MEF feeders. In conclusion, hHFDC maintained hESCs in an undifferentiated state comparable to MEF in standard conditions, which may be an important finding regarding the establishment of stem cell-based translational applications.

NANOG Restores Contractility of Mesenchymal Stem Cell-Based Senescent Microtissues

Mesenchymal stem cells (MSCs) have been extensively used in the field of tissue engineering as a source of smooth muscle cells (SMCs). However, recent studies showed deficits in the contractile function of SMCs derived from senescent MSCs and there are no available strategies to restore the contractile function that is impaired due to cellular or organismal senescence. In this study, we developed a tetracycline-regulatable system and employed micropost tissue arrays to evaluate the effects of the embryonic transcription factor, NANOG, on the contractility of senescent MSCs. Using this system, we show that expression of NANOG fortified the actin cytoskeleton and restored contractile function that was impaired in senescent MSCs. NANOG increased the expression of smooth muscle α-actin (ACTA2) as well as the contractile force generated by cells in three-dimensional microtissues. Interestingly, NANOG worked together with transforming growth factor-beta1 to further enhance the contractility of senescent microtissues. The effect of NANOG on contractile function was sustained for about 10 days after termination of its expression. Our results show that NANOG could reverse the effects of stem cell senescence and restore the myogenic differentiation potential of senescent MSCs. These findings may enable development of novel strategies to restore the function of senescent cardiovascular and other SMC-containing tissues.

Epidermal Growth Factor Induces Proliferation of Hair Follicle-Derived Mesenchymal Stem Cells Through Epidermal Growth Factor Receptor-Mediated Activation of ERK and AKT Signaling Pathways Associated with Upregulation of Cyclin D1 and Downregulation of p16

The maintenance of highly proliferative capacity and full differentiation potential is a necessary step in the initiation of stem cell-based regenerative medicine. Our recent study showed that epidermal growth factor (EGF) significantly enhanced hair follicle-derived mesenchymal stem cell (HF-MSC) proliferation while maintaining the multilineage differentiation potentials. However, the underlying mechanism remains unclear. Herein, we investigated the role of EGF in HF-MSC proliferation. HF-MSCs were isolated and cultured with or without EGF. Immunofluorescence staining, flow cytometry, cytochemistry, and western blotting were used to assess proliferation, cell signaling pathways related to the EGF receptor (EGFR), and cell cycle progression. HF-MSCs exhibited surface markers of mesenchymal stem cells and displayed trilineage differentiation potentials toward adipocytes, chondrocytes, and osteoblasts. EGF significantly increased HF-MSC proliferation as well as EGFR, ERK1/2, and AKT phosphorylation (p-EGFR, p-ERK1/2, and p-AKT) in a time- and dose-dependent manner, but not STAT3 phosphorylation. EGFR inhibitor (AG1478), PI3K-AKT inhibitor (LY294002), ERK inhibitor (U0126), and STAT3 inhibitor (STA-21) significantly blocked EGF-induced HF-MSC proliferation. Moreover, AG1478, LY294002, and U0126 significantly decreased p-EGFR, p-AKT, and p-ERK1/2 expression. EGF shifted HF-MSCs at the G1 phase to the S and G2 phase. Concomitantly, cyclinD1, phosphorylated Rb, and E2F1expression increased, while that of p16 decreased. In conclusion, EGF induces HF-MSC proliferation through the EGFR/ERK and AKT pathways, but not through STAT-3. The G1/S transition was stimulated by upregulation of cyclinD1 and inhibition of p16 expression.

In vitro culture of rat hair follicle stem cells on rabbit bladder acellular matrix

Background

The aim of this work was to create a xenogeneic cell scaffold complex with rabbit bladder acellular matrix and rat hair follicle stem cells, to study the feasibility of construct tissue engineer bladder through biocompatibility of hair follicle stem cells and heterogeneous bladder acellular matrix.

Material and Methods

New Zealand rabbit bladder acellular matrix was prepared. Scanning electron microscope and Masson staining were used to analyse the acellular material. Two-steps precipitation method was used to place the third generation of hair follicle stem cells onto the surface of the bladder acellular matrix. The in vitro cell growth on the scaffold complex was regularly monitored through an inverted microscope. Cell growth curve was established and histological examination and scanning electron microscopic were used to analyse the progresses of the cell growth on the matrix material.

Results

The prepared bladder acellular matrix was white, translucent and membranous. It possessed a fibrous network and collagen structure without any significant cell residues as displayed by the scanning electron microscope, and Masson staining. After 48 h of culture, observation by inverted microscope showed that the hair follicle stem cells grew well around the bladder acellular matrix. After 1 week of culture, scanning electron microscopy showed that the hair follicle stem cells spread and adhered on the surface of the scaffold.

Conclusions

The in vitro culture of rat hair follicle stem cells and the rabbit bladder acellular matrix possessed a good biocompatibility, which provides a good experiment support for hair follicle stem cells to repair the bladder defects disease.

Isolation and characterization of hair follicle stem cells from Arbas Cashmere goat

In this study, highly purified hair follicle stem cells from Arbas Cashmere goat (gHFSCs) were isolated using enzyme digestion and adhesion to type IV collagen. The biological characteristics of the gHFSCs were identified by morphological observation, growth curve, markers assay and differentiation in vitro. The gHFSCs were in small cell size with typical cobblestone morphology, good adhesion and high refractive index. Immunocytochemistry staining showed the cells were expressing Krt15, Krt19, CD34, Itgβ1 and Krt14. Cell growth curve indicated that cultured gHFSCs had strong proliferation ability. Krt14 and CD34 were high expressed at the mRNA level, respectively, 39.68 and 24.37 times of the Cashmere goat keratinocytes, and krt15 expression was 5.62 times and itgβ1 expression was 1.81 times higher (p < 0.01). Western blot detected the expression of all the above markers. After osteogenic induction, the cells were positive for Von Kossa staining and expressed Osteocalcin. Sulfated proteoglycans in cartilaginous matrices were positively stained by Alcian blue after chondrogenic induction and COL2A1 was expressed. In myogenic induction, Hoechst 33342 staining evidenced cytoplasm fusion and positive expression of MyoG was detected by immunocytochemistry.

miR-128 regulates differentiation of hair follicle mesenchymal stem cells into smooth muscle cells by targeting SMAD2

Human hair follicle mesenchymal stem cells (hHFMSCs) are an important source of cardiovascular tissue engineering for their differentiation potential into smooth muscle cells (SMCs), yet the molecular pathways underlying such fate determination is unclear. MicroRNAs (miRNAs) are non-coding RNAs that play critical roles in cell differentiation. In present study, we found that miR-128 was remarkably decreased during the differentiation of hHFMSCs into SMCs induced by transforming growth factor-β1 (TGF-β1). Moreover, overexpression of miR-128 led to decreased expression of SMC cellular marker proteins, such as smooth muscle actin (SMA) and calponin, in TGF-β1-induced SMC differentiation. Further, we identified that miR-128 targeted the 3'-UTR of SMAD2 transcript for translational inhibition of SMAD2 protein, and knockdown of SMAD2 abrogated the promotional effect of antagomir-128 (miR-128 neutralizer) on SMC differentiation. These results suggest that miR-128 regulates the differentiation of hHFMSCs into SMCs via targeting SMAD2, a main transcription regulator in TGF-β signaling pathway involving SMC differentiation. The miR-128/SMAD2 axis could therefore be considered as a candidate target in tissue engineering and regenerative medicine for SMCs.

Destruction of the arrector pili muscle and fat infiltration in androgenic alopecia

BACKGROUND

Androgenic alopecia (AGA) is the most common hair loss condition in men and women. Hair loss is caused by follicle miniaturization, which is largely irreversible beyond a certain degree of follicular regression. In contrast, hair loss in telogen effluvium (TE) is readily reversible. The arrector pili muscle (APM) connects the follicle to the surrounding skin.

OBJECTIVES

To compare histopathological features of the APM in AGA and TE.

METHODS

Archival blocks of 4-mm scalp punch biopsies from eight patients with AGA and five with TE were obtained. New 4-mm biopsies from five normal cases were used as controls. Serial 7-μm sections were stained with a modified Masson's trichrome stain. 'Reconstruct' software was used to construct and evaluate three-dimensional images of the follicle and APM.

RESULTS

The APM degenerated and was replaced by adipose tissue in all AGA specimens. Remnants of the APM remained attached to the hair follicle. There was no fat in the normal skin specimens. Fat was seen in two of five TE specimens but could be attributed to these patients also showing evidence of AGA. Quantitative analysis showed that muscle volume decreased and fat volume increased significantly (P < 0·05) in AGA compared with controls.

CONCLUSIONS

APM degeneration and replacement with fat in AGA has not previously been described. The underlying mechanism remains to be determined. However, we speculate that this phenomenon might be related to depletion of stem or progenitor cells from the follicle mesenchyme, explaining why AGA is treatment resistant.

Fabrication of tissue-engineered vascular grafts with stem cells and stem cell-derived vascular cells

INTRODUCTION

Cardiovascular disease is the leading cause of mortality worldwide. Current surgical treatments for cardiovascular disease include vascular bypass grafting and replacement with autologous blood vessels or synthetic vascular grafts. However, there is a call for better alternative biological grafts.

AREAS COVERED

Tissue-engineered vascular grafts (TEVGs) are promising novel alternatives to replace diseased vessels. However, obtaining enough functional and clinically usable vascular cells for fabrication of TEVGs remains a major challenge. New findings in adult stem cells and recent advances in pluripotent stem cells have opened a new avenue for stem cell-based vascular engineering. In this review, recent advances on stem cell sourcing for TEVGs including the use of adult stem cells and pluripotent stem cells and advantages, disadvantages, and possible future implementations of different types of stem cells will be discussed. In addition, current strategies used during the fabrication of TEVGs will be highlighted.

EXPERT OPINION

The application of patient-specific TEVGs constructed with vascular cells derived from immune-compatible stem cells possesses huge clinical potential. Advances in lineage-specific differentiation approaches and innovative vascular engineering strategies will promote the vascular regeneration field from bench to bedside.

Lentivirus Live Cell Array for Quantitative Assessment of Gene and Pathway Activation during Myogenic Differentiation of Mesenchymal Stem Cells

Stem cell differentiation involves multiple cascades of transcriptional regulation that govern the cell fate. To study the real-time dynamics of this complex process, quantitative and high throughput live cell assays are required. Herein, we developed a lentiviral library of promoters and transcription factor binding sites to quantitatively capture the gene expression dynamics over a period of several days during myogenic differentiation of human mesenchymal stem cells (MSCs) harvested from two different anatomic locations, bone marrow and hair follicle. Our results enabled us to monitor the sequential activation of signaling pathways and myogenic gene promoters at various stages of differentiation. In conjunction with chemical inhibitors, the lentiviral array (LVA) results also revealed the relative contribution of key signaling pathways that regulate the myogenic differentiation. Our study demonstrates the potential of LVA to monitor the dynamics of gene and pathway activation during MSC differentiation as well as serve as a platform for discovery of novel molecules, genes and pathways that promote or inhibit complex biological processes.

CD90 is upregulated in gastric cancer tissues and inhibits gastric cancer cell apoptosis by modulating the expression level of SPARC protein

Cluster of differentiation 90 (CD90) (Thy-1) plays important roles in the oncogenesis in various types of malignancies. In the present study, we investigated the expression of CD90 in gastric cancer (GC) tissues by q-PCR, immunohistochemistry (IHC), and western blot technologies. The results showed that CD90 was overexpressed in gastric cancer tissues compared with the level in the adjacent non‑cancerous tissues. To explore the possible mechanism of CD90 in GC, we elucidated the effect of CD90 on the apoptosis of AGS gastric cancer cells, and found that a considerable decrease in apoptotic cells was observed for AGS cells with CD90 overexpression. Meanwhile, the rate of apoptotic cells was increased in the AGS cells with CD90 interference (siCD90) compared with that in the AGS cells. Cell apoptosis is closely related to a reduction in mitochondrial membrane potential (ΔΨm) and an increase in intracellular reactive oxygen species (ROS) and calcium ion (Ca2+) concentrations. Our results showed that overexpression of CD90 in the AGS gastric cancer cells led to an increase in ΔΨm and a decrease in intracellular ROS and Ca2+ concentrations. At the same time, siCD90 reduced ΔΨm and the increase in intracellular ROS and Ca2+ concentrations. Furthermore, we identified and confirmed that CD90 functions by modulating the expression level of secreted protein, acidic, cysteine‑rich (osteonectin) (SPARC) in vitro through LC‑MS/MS analyses and western blot technology. In summary, our results suggest that CD90 is upregulated in gastric cancer and inhibits gastric cancer cell apoptosis by modulating the expression level of SPARC protein.

Feasibility of human hair follicle-derived mesenchymal stem cells/CultiSpher(®)-G constructs in regenerative medicine

The use of human mesenchymal stem cells (hMSCs) in cell therapies has increased the demand for strategies that allow efficient cell scale-up. Preliminary data on the three-dimensional (3D) spinner culture describing the potential use of microcarriers for hMSCs culture scale-up have been reported. We exploited a rich source of autologous stem cells (human hair follicle) and demonstrated the robust in vitro long-term expansion of human hair follicle-derived mesenchymal stem cells (hHF-MSCs) by using CultiSpher(®)-G microcarriers. We analyzed the feasibility of 3D culture by using hHF-MSCs/CultiSpher(®)-G microcarrier constructs for its potential applicability in regenerative medicine by comparatively analyzing the performance of hHF-MSCs adhered to the CultiSpher(®)-G microspheres in 3D spinner culture and those grown on the gelatin-coated plastic dishes (2D culture), using various assays. We showed that the hHF-MSCs seeded at various densities quickly adhered to and proliferated well on the microspheres, thus generating at least hundreds of millions of hHF-MSCs on 1 g of CultiSpher(®)-G within 12 days. This resulted in a cumulative cell expansion of greater than 26-fold. Notably, the maximum and average proliferation rates in 3D culture were significantly greater than that of the 2D culture. However, the hHF-MSCs from both the cultures retained surface marker and nestin expression, proliferation capacity and differentiation potentials toward adipocytes, osteoblasts and smooth muscle cells and showed no significant differences as evidenced by Edu incorporation, cell cycle, colony formation, apoptosis, biochemical quantification and qPCR assays.

Magnetofection Mediated Transient NANOG Overexpression Enhances Proliferation and Myogenic Differentiation of Human Hair Follicle Derived Mesenchymal Stem Cells

We used magnetofection (MF) to achieve high transfection efficiency into human mesenchymal stem cells (MSCs). A custom-made magnet array, matching well-to-well to a 24-well plate, was generated and characterized. Theoretical predictions of magnetic force distribution within each well demonstrated that there was no magnetic field interference among magnets in adjacent wells. An optimized protocol for efficient gene delivery to human hair follicle derived MSCs (hHF-MSCs) was established using an egfp-encoding plasmid, reaching approximately ∼50% transfection efficiency without significant cytotoxicity. Then we applied the optimized MF protocol to express the pluripotency-associated transcription factor NANOG, which was previously shown to reverse the effects of organismal aging on MSC proliferation and myogenic differentiation capacity. Indeed, MF-mediated NANOG delivery increased proliferation and enhanced the differentiation of hHF-MSCs into smooth muscle cells (SMCs). Collectively, our results show that MF can achieve high levels of gene delivery to MSCs and, therefore, may be employed to moderate or reverse the effects of cellular senescence or reprogram cells to the pluripotent state without permanent genetic modification.

Cyclosporine A increases hair follicle growth by suppressing apoptosis-inducing factor nuclear translocation: a new mechanism

Cyclosporine A (CsA) enhances hair growth through caspase-dependent pathways by retarding anagen-to-catagen phase transition in the hair follicle growth cycle. Whether apoptosis-inducing factor (AIF), a protein that induces caspase-independent apoptosis, can regulate the hair follicle cycle in response to CsA is currently unclear. Here, we show that the pro-hair growth properties of CsA are in part due to blockage of AIF nuclear translocation. We first isolate hair follicles from murine dorsal skin. We then used Western blot, immunohistochemistry and immunofluorescence to evaluate the expression and localization of AIF in hair follicles. We also determined whether modulation of AIF was responsible for the effects of CsA at the anagen-to-catagen transition. AIF was expressed in hair follicles during the anagen, catagen and telogen phases. There was significant nuclear translocation of AIF as hair follicles transitioned from anagen to late catagen phase; this was inhibited by CsA, likely due to reduced cyclophilin A expression and attenuated AIF release from mitochondria. However, we note that AIF translocation was not completely eliminated, which likely explains why the transition to catagen phase was severely retarded by CsA, rather than being completely inhibited. We speculate that blockade of the AIF signalling pathway is a critical event required for CsA-dependent promotion of hair growth in mice. The study of AIF-related signalling pathways may provide insight into hair diseases and suggest potential novel therapeutic strategies.

Differential effects of culture senescence and mechanical stimulation on the proliferation and leiomyogenic differentiation of MSC from different sources: implications for engineering vascular grafts

We examined the effects of senescence on the proliferation and leiomyogenic differentiation potential of mesenchymal stem cells (MSCs) isolated from bone marrow (BM-MSCs) or hair follicles (HF-MSCs). To this end, we compared ovine HF-MSCs and BM-MSCs in terms of their proliferation and differentiation potential to the smooth muscle cell lineage. We discovered that HF-MSCs are less susceptible to culture senescence compared with BM-MSCs. We hypothesized that application of mechanical forces may enhance the contractility and mechanical properties of vascular constructs prepared from senescent MSCs. Interestingly, HF-MSCs and BM-MSCs responded differently to changes in the mechanical microenvironment, suggesting that despite phenotypic similarities, MSCs from different anatomic locations may activate different pathways in response to the same microenvironmental factors. In turn, this may also suggest that cell-based tissue regeneration approaches may need to be tailored to the stem cell origin, donor age, and culture time for optimal results.

Acellular blood vessels combined human hair follicle mesenchymal stem cells for engineering of functional arterial grafts

Tissue-engineered vessels offer options for autologous vascular grafts in cardiovascular repair and regeneration. The experiments aimed to construct functional arterial grafts by combining human hair follicle mesenchymal stem cells (HF-MSCs) with acellular umbilical arteries. We isolated mesenchymal stem cells from human hair follicles. Under appropriate culture conditions, these cells displayed CD44, CD90 and CD105, and exhibited the potential for differentiation to adipocytes, osteoblasts and chondrocytes. Very promisingly, HF-MSCs expressed the vascular smooth muscle specific markers in the presence of transforming growth factor-β. We created acellular arterial scaffolds by digesting human umbilical arteries with trypsin and sodium dodecyl sulfate. These acellular arterial scaffolds retained major components of the extracellular matrix. The mechanical properties of these acellular arterial scaffolds were very similar to those of native blood vessels. We then seeded HF-MSCs into acellular arterial scaffolds and found that they still expressed vascular smooth muscle specific markers. The arterial grafts derived from HF-MSCs demonstrated vasoreactivity in response to humoral constrictors. We constructed arterial grafts that are very close to native blood vessels in their structures and physiological functions. These properties suggest that these arterial grafts could be used as small diameter arterial grafts for cardiovascular repair and regeneration.

Multipotent neural crest stem cell-like cells from rat vibrissa dermal papilla induce neuronal differentiation of PC12 cells

Bone marrow mesenchymal stem cells (BMSCs) transplants have been approved for treating central nervous system (CNS) injuries and diseases; however, their clinical applications are limited. Here, we model the therapeutic potential of dermal papilla cells (DPCs) in vitro. DPCs were isolated from rat vibrissae and characterized by immunocytofluorescence, RT-PCR, and multidifferentiation assays. We examined whether these cells could secrete neurotrophic factors (NTFs) by using cocultures of rat pheochromocytoma cells (PC12) with conditioned medium and ELISA assay. DPCs expressed Sox10, P75, Nestin, Sox9, and differentiated into adipocytes, osteoblasts, smooth muscle cells, and neurons under specific inducing conditions. The DPC-conditioned medium (DPC-CM) induced neuronal differentiation of PC12 cells and promoted neurite outgrowth. Results of ELISA assay showed that compared to BMSCs, DPCs secreted more brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF). Moreover, we observed that, compared with the total DPC population, sphere-forming DPCs expressed higher levels of Nestin and P75 and secreted greater amounts of GDNF. The DPCs from craniofacial hair follicle papilla may be a new and promising source for treating CNS injuries and diseases.

Lentiviral arrays for live-cell dynamic monitoring of gene and pathway activity during stem cell differentiation

Uncovering the complexity of mesenchymal stem cell (MSC) differentiation requires novel methods to capture the dynamics of the process in a quantitative and high-throughput manner. To this end, we developed a lentiviral array (LVA) of reporters to capture the dynamics of gene and pathway activity during MSC differentiation into adipogenic, chondrogenic, and osteogenic lineages. Our results identified signature promoters and pathways with unique activation profile for each MSC lineage. In combination with chemical inhibitors, lineage-specific reporters predicted the effects of signaling pathway perturbations on MSC differentiation. Interestingly, some pathways were critical for differentiation into all lineages, while others had differential effects on each lineage. Our study suggests that when combined with large chemical or siRNA libraries, the reporter LVA can be used to uncover novel genes and signaling pathways affecting complex biological processes such as stem cell differentiation or reprogramming.

Engineered hair follicle mesenchymal stem cells overexpressing controlled-release insulin reverse hyperglycemia in mice with type L diabetes

Genetically engineered stem cells that overexpress genes encoding therapeutic products can be exploited to correct metabolic disorders by repairing and regenerating diseased organs or restoring their function. Hair follicles are readily accessible and serve as a rich source of autologous stem cells for cell-based gene therapy. Here we isolated mesenchymal stem cells from human hair follicles (HF-MSCs) and engineered them to overexpress the human insulin gene and release human insulin in a time- and dose-dependent manner in response to rapamycin. The engineered HF-MSCs retained their characteristic cell surface markers and retained their potential to differentiate into adipocytes and osteoblasts. When mice with streptozotocin-induced type 1 diabetes were engrafted with these engineered HF-MSCs, these cells expressed and released a dose of human insulin, dramatically reversed hyperglycemia, and significantly reduced death rate. Moreover, the engineered HF-MSCs did not form detectable tumors throughout the 120-day animal tests in our experiment. Our results show that HF-MSCs can be used to safely and efficiently express therapeutic transgenes and therefore show promise for cell-based gene therapy of human disease.

Cadherin-11 regulates both mesenchymal stem cell differentiation into smooth muscle cells and the development of contractile function in vivo

Although soluble factors, such as transforming growth factor β1 (TGF-β1), induce mesenchymal stem cell (MSC) differentiation towards the smooth muscle cell (SMC) lineage, the role of adherens junctions in this process is not well understood. In this study, we found that cadherin-11 but not cadherin-2 was necessary for MSC differentiation into SMCs. Cadherin-11 regulated the expression of TGF-β1 and affected SMC differentiation through a pathway that was dependent on TGF-β receptor II (TGFβRII) but independent of SMAD2 or SMAD3. In addition, cadherin-11 activated the expression of serum response factor (SRF) and SMC proteins through the Rho-associated protein kinase (ROCK) pathway. Engagement of cadherin-11 increased its own expression through SRF, indicative of the presence of an autoregulatory feedback loop that committed MSCs to the SMC fate. Notably, SMC-containing tissues (such as aorta and bladder) from cadherin-11-null (Cdh11(-/-)) mice showed significantly reduced levels of SMC proteins and exhibited diminished contractility compared with controls. This is the first report implicating cadherin-11 in SMC differentiation and contractile function in vitro as well as in vivo.

Human amniotic fluid stem cell differentiation along smooth muscle lineage

Functional smooth muscle engineering requires isolation and expansion of smooth muscle cells (SMCs), and this process is particularly challenging for visceral smooth muscle tissue where progenitor cells have not been clearly identified. Herein we showed for the first time that efficient SMCs can be obtained from human amniotic fluid stem cells (hAFSCs). Clonal lines were generated from c-kit(+) hAFSCs. Differentiation toward SM lineage (SMhAFSCs) was obtained using a medium conditioned by PDGF-BB and TGF-β1. Molecular assays revealed higher level of α smooth muscle actin (α-SMA), desmin, calponin, and smoothelin in SMhAFSCs when compared to hAFSCs. Ultrastructural analysis demonstrated that SMhAFSCs also presented in the cytoplasm increased intermediate filaments, dense bodies, and glycogen deposits like SMCs. SMhAFSC metabolism evaluated via mass spectrometry showed higher glucose oxidation and an enhanced response to mitogenic stimuli in comparison to hAFSCs. Patch clamp of transduced hAFSCs with lentiviral vectors encoding ZsGreen under the control of the α-SMA promoter was performed demonstrating that SMhAFSCs retained a smooth muscle cell-like electrophysiological fingerprint. Eventually SMhAFSCs contractility was evident both at single cell level and on a collagen gel. In conclusion, we showed here that hAFSCs under selective culture conditions are able to give rise to functional SMCs.

Purification and functional assessment of smooth muscle cells derived from mouse embryonic stem cells

OBJECTIVE

To obtain a pure population of smooth muscle cells (SMC) derived from mouse embryonic stem cells (ESC) and further assess their functions.

METHODS

A vector, expressing both puromycin resistance gene (puro(r) ) and enhanced green fluorescent protein (EGFP) gene driven by smooth muscle 22α (SM22α) promoter, named pSM22α-puro(r)-IRES2-EGFP was constructed and used to transfect ESC. Transgenic ESC (Tg-ESC) clones were selected by G418 and identified by PCR amplification of puro(r) gene. The characteristics of Tg-ESC were detected by alkaline phosphatase (ALP) staining, SSEA-1 immunofluorescence and teratoma formation test in vivo. After induction of SMC differentiation by all-trans retinoic acid, differentiated Tg-ESC were treated with 10 µg/mL puromycin for three days to obtain purified SMC (P-SMC). Percentage of EGFP(+) cells in P-SMC was assessed by flow cytometer. Expressions of smooth muscle specific markers were detected by immunostaining and Western blotting. Proliferation, migration and contractility of P-SMC were analyzed by growth curve, trans-well migration assay, and carbachol treatment, respectively. Finally, both P-SMC and unpurified SMC (unP-SMC) were injected into syngeneic mouse to see teratoma development.

RESULTS

Tg-ESC clone was successfully established and confirmed by PCR detection of puro(r) gene in its genomic DNA. The Tg-ESC was positive for ALP staining, SSEA-1 staining and formed teratoma containing tissues derived from three germ layers. After retinoic acid induction, large amount of EGFP positive cells outgrew from differentiated Tg-ESC. Three days of puromycin treatment produced a population of P-SMC with an EGFP(+) percentage as high as 98.2% in contrast to 29.47% of unP-SMC. Compared with primary mouse vascular smooth muscle cells (VSMC), P-SMC displayed positive, but lowered expression of SMC-specific markers including SM α-actin and myosin heavy chain (SM-MHC) detected either, by immunostaining, or immunoblotting, accelerated proliferation, improved migration (99.33 ± 2.04 vs. 44.00 ± 2.08 migrated cells/field, P < 0.05), and decreased contractility in response to carbachol (7.75 ± 1.19 % vs. 16.50 ± 3.76 % in cell area reduction, P < 0.05). In vivo injection of unP-SMC developed apparent teratoma while P-SMC did not.

CONCLUSIONS

We obtained a pure population of ESC derived SMC with less mature (differentiated) phenotypes, which will be of great use in research of vascular diseases and in bio-engineered vascular grafts for regenerative medicine.

Poly(ethylene glycol)-block-cationic polylactide nanocomplexes of differing charge density for gene delivery

Representing a new type of biodegradable cationic block copolymer, well-defined poly(ethylene glycol)-block-cationic polylactides (PEG-b-CPLAs) with tertiary amine-based cationic groups were synthesized by thiol-ene functionalization of an allyl-functionalized diblock precursor. Subsequently the application of PEG-b-CPLAs as biodegradable vectors for the delivery of plasmid DNAs (pDNAs) was investigated. Via the formation of PEG-b-CPLA:pDNA nanocomplexes by spontaneous electrostatic interaction, pDNAs encoding luciferase or enhanced green fluorescent protein were successfully delivered to four physiologically distinct cell lines (including macrophage, fibroblast, epithelial, and stem cell). Formulated nanocomplexes demonstrated high levels of transfection with low levels of cytotoxicity and hemolysis when compared to a positive control. Biophysical characterization of charge densities of nanocomplexes at various polymer:pDNA weight ratios revealed a positive correlation between surface charge and gene delivery. Nanocomplexes with high surface charge densities were utilized in an in vitro serum gene delivery inhibition assay, and effective gene delivery was observed despite high levels of serum. Overall, these results help to elucidate the influence of charge, size, and PEGylation of nanocomplexes upon the delivery of nucleic acids in physiologically relevant conditions.

Differential and synergistic effects of mechanical stimulation and growth factor presentation on vascular wall function

We investigated the hypothesis that immobilizing TGF-β1 within fibrin hydrogels may act in synergy with cyclic mechanical stimulation to enhance the properties of vascular grafts. To this end, we engineered a fusion TGF-β1 protein that can covalently anchor to fibrin during polymerization upon the action of factor XIII. We also developed a 24-well based bioreactor in which vascular constructs can be mechanically stimulated by distending the silastic mandrel in the middle of each well. TGF-β1 was either conjugated to fibrin or supplied in the culture medium and the fibrin-based constructs were cultured statically for a week followed by cyclic distention for another week. The tissues were examined for myogenic differentiation, vascular reactivity, mechanical properties and ECM content. Our results showed that some aspects of vascular function were differentially affected by growth factor presentation vs. pulsatile force application, while others were synergistically enhanced by both. Overall, this two-prong biomimetic approach improved ECM secretion, vascular reactivity and mechanical properties of vascular constructs. These findings may be applied in other tissue engineering applications such as cartilage, tendon or cardiac regeneration where growth factors TGF-β1 and mechano-stimulation play critical roles.

Drug-resistant colon cancer cells produce high carcinoembryonic antigen and might not be cancer-initiating cells

Purpose

We evaluated the higher levels of carcinoembryonic antigen (CEA) secreted by the LoVo human colon carcinoma cells in a medium containing anticancer drugs. Drug-resistant LoVo cells were analyzed by subcutaneously xenotransplanting them into mice. The aim of this study was to evaluate whether the drug-resistant cells isolated in this study were cancer-initiating cells, known also as cancer stem cells (CSCs).

Methods

The production of CEA was investigated in LoVo cells that were cultured with 0–10 mM of anticancer drugs, and we evaluated the increase in CEA production by the LoVo cells that were stimulated by anticancer drug treatment. The expression of several CSC markers in LoVo cells treated with anticancer drugs was also evaluated. Following anticancer drug treatment, LoVo cells were injected subcutaneously into the flanks of severe combined immunodeficiency mice in order to evaluate the CSC fraction.

Results

Production of CEA by LoVo cells was stimulated by the addition of anticancer drugs. Drug-resistant LoVo cells expressed lower levels of CSC markers, and LoVo cells treated with any of the anticancer drugs tested did not generate tumors within 8 weeks from when the cells were injected subcutaneously into severe combined immunodeficiency mice. These results suggest that the drug-resistant LoVo cells have a smaller population of CSCs than the untreated LoVo cells.

Conclusion

Production of CEA by LoVo cells can be stimulated by the addition of anticancer drugs. The drug-resistant subpopulation of LoVo colon cancer cells could stimulate the production of CEA, but these cells did not act as CSCs in in vivo tumor generation experiments.

Animal models for vascular tissue-engineering

Because of rise in cardiovascular disease throughout the world, there is increasing demand for small diameter blood vessels as replacement grafts. The present review focuses on the animal models that have been used to test small-diameter TEVs with emphasis on the attributes of each model. Small animal models are used to test short-term patency and address mechanistic hypotheses; and large, preclinical animal models are employed to test long-term patency, remodeling and function in an environment mimicking human physiology. We also discuss recent clinical trials that employed laboratory fabricated TEVs and showed very promising results. Ultimately, animal models provide a testing platform for optimizing vascular grafts before clinical use in patients without suitable autologous vessels.

Maintenance of high proliferation and multipotent potential of human hair follicle-derived mesenchymal stem cells by growth factors

Cell therapy and cell-based tissue engineering is becoming increasingly important in regenerative medicine. Stem cells that are characterized by self-renewal, high proliferation and multiple differentiation potentials have attracted attention in cell-based regenerative medicine. Maintaining the aforementioned characteristics of stem cells is the first key step in cell-based regenerative medicine. Basic fibroblast growth factor (bFGF) is a well-known growth factor that efficiently maintains the self-renewal, high proliferation and multilineage differentiation potential of stem cells. Whether or not other growth factors, such as acidic fibroblast growth factor (aFGF) and epidermal growth factor (EGF) have similar effects has yet to be fully elucidated. Human hair follicle-derived mesenchymal stem cells (HF-MSCs) were obtained by organ culture. They exhibited surface markers of bone marrow mesenchymal stem cells as shown by positive staining for CD44, CD73, CD90 and CD105, and they also displayed trilineage differentiation potentials into adipocytes, chondrocytes and osteoblasts by cytochemistry and qRT-PCR. Flow cytometry analysis showed that up to 70% of HF-MSCs cultured in the presence of aFGF, bFGF or EGF stayed at the G0/G1 phase. Proliferation analysis showed that both bFGF and EGF at as low as 1 ng/ml and aFGF at above 5 ng/ml levels significantly increased the proliferation of HF-MSCs by cell counting. Consistent with proliferation analysis, immunofluorescence staining showed that more than 95% of HF-MSCs cultured in the presence of aFGF, bFGF and EGF were positively stained for proliferating cell nuclear antigen. HF-MSCs cultured in the presence of aFGF, bFGF or EGF retained marked trilineage differentiation potentials. By contrast, HF-MSCs cultured in the absence of bFGF, aFGF and EGF lost multipotency.

Hair follicle: a novel source of multipotent stem cells for tissue engineering and regenerative medicine

The adult body harbors powerful reservoirs of stem cells that enable tissue regeneration under homeostatic conditions or in response to disease or injury. The hair follicle (HF) is a readily accessible mini organ within the skin and contains stem cells from diverse developmental origins that were shown to have surprisingly broad differentiation potential. In this review, we discuss the biology of the HF with particular emphasis on the various stem cell populations residing within the tissue. We summarize the existing knowledge on putative HF stem cell markers, the differentiation potential, and technologies to isolate and expand distinct stem cell populations. We also discuss the potential of HF stem cells for drug and gene delivery, tissue engineering, and regenerative medicine. We propose that the abundance of stem cells with broad differentiation potential and the ease of accessibility makes the HF an ideal source of stem cells for gene and cell therapies.

A novel lentivirus for quantitative assessment of gene knockdown in stem cell differentiation

Loss of gene function is a valuable tool for screening genes in cellular processes including stem cell differentiation differentiation. However, the criteria for evaluating gene knockdown are usually based on end-point analysis and real-time, dynamic information is lacking. To overcome these limitations, we engineered a shRNA encoding LentiViral Dual Promoter vector (shLVDP) that enabled real-time monitoring of mesenchymal stem (MSC) differentiation and simultaneous gene knockdown. In this vector, the activity of the alpha-smooth muscle actin (αSMA) promoter was measured by the expression of a destabilized green fluorescent protein, and was used as an indicator of myogenic differentiation; constitutive expression of discosoma red fluorescent protein was used to measure transduction efficiency and to normalize αSMA promoter activity; and shRNA was encoded by a doxycycline (Dox)-regulatable H1 promoter. Importantly, the normalized promoter activity was independent of lentivirus titer allowing quantitative assessment of gene knockdown. Using this vector, we evaluated 11 genes in the TGF-β1 or Rho signaling pathway on SMC maturation and on MSC differentiation along the myogenic lineage. As expected, knockdown of genes such as Smad2/3 or RhoA inhibited myogenic differentiation, while knocking down the myogenic differentiation inhibitor, Klf4, increased αSMA promoter activity significantly. Notably, some genes for example, Smad7 or KLF4 showed differential regulation of myogenic differentiation in MSC from different anatomic locations such as bone marrow and hair follicles. Finally, Dox-regulatable shRNA expression enabled temporal control of gene knockdown and provided dynamic information on the effect of different genes on myogenic phenotype. Our data suggests that shLVDP may be ideal for development of lentiviral microarrays to decipher gene regulatory networks of complex biological processes such as stem cell differentiation or reprogramming.

Functional vascular smooth muscle cells derived from human induced pluripotent stem cells via mesenchymal stem cell intermediates

AIMS

Smooth muscle cells (SMC) play an important role in vascular homeostasis and disease. Although adult mesenchymal stem cells (MSC) have been used as a source of contractile SMC, they suffer from limited proliferation potential and culture senescence, particularly when originating from older donors. By comparison, human induced pluripotent stem cells (hiPSC) can provide an unlimited source of functional SMC for autologous cell-based therapies and for creating models of vascular disease. Our goal was to develop an efficient strategy to derive functional, contractile SMC from hiPSC.

METHODS AND RESULTS

We developed a robust, stage-wise, feeder-free strategy for hiPSC differentiation into functional SMC through an intermediate stage of multipotent MSC, which could be coaxed to differentiate into fat, bone, cartilage, and muscle. At this stage, the cells were highly proliferative and displayed higher clonogenic potential and reduced senescence when compared with parental hair follicle mesenchymal stem cells. In addition, when exposed to differentiation medium, the myogenic proteins such as α-smooth muscle actin, calponin, and myosin heavy chain were significantly upregulated and displayed robust fibrillar organization, suggesting the development of a contractile phenotype. Indeed, tissue constructs prepared from these cells exhibited high levels of contractility in response to receptor- and non-receptor-mediated agonists.

CONCLUSION

We developed an efficient stage-wise strategy that enabled hiPSC differentiation into contractile SMC through an intermediate population of clonogenic and multipotent MSC. The high yield of MSC and SMC derivation suggests that our strategy may facilitate an acquisition of the large numbers of cells required for regenerative medicine or for studying vascular disease pathophysiology.

Stem cell sources for vascular tissue engineering and regeneration

This review focuses on the stem cell sources with the potential to be used in vascular tissue engineering and to promote vascular regeneration. The first clinical studies using tissue-engineered vascular grafts are already under way, supporting the potential of this technology in the treatment of cardiovascular and other diseases. Despite progress in engineering biomaterials with the appropriate mechanical properties and biological cues as well as bioreactors for generating the correct tissue microenvironment, the source of cells that make up the vascular tissues remains a major challenge for tissue engineers and physicians. Mature cells from the tissue of origin may be difficult to obtain and suffer from limited proliferative capacity, which may further decline as a function of donor age. On the other hand, multipotent and pluripotent stem cells have great potential to provide large numbers of autologous cells with a great differentiation capacity. Here, we discuss the adult multipotent as well as embryonic and induced pluripotent stem cells, their differentiation potential toward vascular lineages, and their use in engineering functional and implantable vascular tissues. We also discuss the associated challenges that need to be addressed in order to facilitate the transition of this technology from the bench to the bedside.

Smooth muscle and other cell sources for human blood vessel engineering

Despite substantial progress in the field of vascular tissue engineering over the past decades, transition to human models has been rather challenging. The limited replicative life spans of human adult vascular cells, and their slow rate of collagenous matrix production in vitro, have posed important hurdles in the development of mechanically robust and biologically functional engineered grafts. With the more recent advances in the field of stem cells, investigators now have access to a plethora of new cell source alternatives for vascular engineering. In this paper, we review various alternative cell sources made available more recently for blood vessel engineering and also present some recent data on the derivation of smooth muscle cells from human induced pluripotent stem cells.