Stem cells in adult skeletal muscle

Cell Therapy in the Treatment of Coronary Heart Disease

Heart failure is a leading cause of death in patients who have suffered a myocardial infarction. Despite the timely use of modern reperfusion therapies such as thrombolysis, surgical revascularization and balloon angioplasty, they are sometimes unable to prevent the development of significant areas of myocardial damage and subsequent heart failure. Research efforts have focused on developing strategies to improve the functional status of myocardial injury areas. Consequently, the restoration of cardiac function using cell therapy is an exciting prospect. This review describes the characteristics of various cell types relevant to cellular cardiomyoplasty and presents findings from experimental and clinical studies investigating cell therapy for coronary heart disease. Cell delivery methods, optimal dosage and potential treatment mechanisms are discussed.

Three-Dimensional Imaging Analysis for Skeletal Muscle

Skeletal muscle is a highly ordered tissue composed of a complex network of a diverse variety of cells. The dynamic spatial and temporal interaction between these cells during homeostasis and during times of injury gives the skeletal muscle its regenerative capacity. In order to properly understand the process of regeneration, a three-dimensional (3-D) imaging process must be conducted. While there have been several protocols studying 3-D imaging, it has primarily been focused on the nervous system. This protocol aims to outline the workflow for rendering a 3-D image of the skeletal muscle using spatial data from confocal microscope images. This protocol uses the ImageJ, Ilastik, and Imaris software for 3-D rendering and computational image analysis as both are relatively easy to use and have powerful segmentation capabilities.

Biomedical applications of muscle-derived stem cells: from bench to bedside

INTRODUCTION

Skeletal muscle-derived stem cells (Sk-MDSCs) are considered promising sources of adult stem cell therapy. Skeletal muscle comprises approximately 40-50% of the total body mass with marked potential for postnatal adaptive response, such as muscle hypertrophy, hyperplasia, atrophy, and regenerative capacity. This strongly suggests that skeletal muscle contains various stem/progenitor cells related to muscle-nerve-vascular tissues, which would support the above postnatal events even in adulthood.

AREA COVERED

The focus of this review is the therapeutic potential of the Sk-MDSCs as an adult stem cell autograft. For this purpose, the validity of cell isolation and purification, tissue reconstitution capacity in vivo after transplantation, comparison of the results of basic mouse and preclinical human studies, potential problematic and beneficial aspects, and effective usage have been discussed following the history of clinical applications.

EXPERT OPINION

Although the clinical application of Sk-MDSCs began as a therapy for the systemic disease of Duchenne muscular dystrophy, here, through the unique local injection method, therapy for severely damaged peripheral nerves, particularly the long-gap nerve transection, has been introduced. The beneficial aspects of the use of Sk-MDSCs as the source of local tissue transplantation therapy have also been discussed.

Platelet-rich plasma enhances the repair capacity of muscle-derived mesenchymal stem cells to large humeral bone defect in rabbits

Mesenchymal stem cell-based therapy is a highly attractive strategy that promotes bone tissue regeneration. The aim of the present study was to evaluate the combination effect of muscle-derived mesenchymal stem cells (M-MSCs) and platelet-rich plasma (PRP) on bone repair capacity in rabbits with large humeral bone defect. Precise cylindrical bone defects of 10 mm diameter and 5 mm depth were established in rabbit humeral bones, which were unable to be repaired under natural conditions. The rabbits received treatment with M-MSCs/PRP gel, M-MSCs gel, or PRP gel, or no treatment. The bone tissue regeneration was evaluated at day 0-90 after surgery by HE morphological staining, Lane-Sandhu histopathological scoring, tetracycline detection, Gomori staining and micro-computed tomography. Beyond that, Transwell assay, CCK8 assay, Western blot analysis and ALP activity detection were performed in M-MSCs in vitro with or without PRP application to detect the molecular effects of PRP on M-MSCs. We found that the repair effect of M-MSCs group or PRP group was limited and the bone defects were not completely closed at post-operation 90 d. In contrast, M-MSCs/PRP group received obvious filling in the bone defects with a Lane-Sandhu evaluation score of 9. Tetracycline-labeled new bone area in M-MSCs/PRP group and new mineralized bone area were significantly larger than that in other groups. Micro-computed tomography result of M-MSCs/PRP group displayed complete recovery of humeral bone at post-operation 90 d. Further in vitro experiment revealed that PRP significantly induced migration, enhanced the growth, and promoted the expression of Cbfa-1 and Coll I in M-MSCs. In conclusion, PRP application significantly enhanced the regeneration capacity of M-MSCs in large bone defect via promoting the migration and proliferation of M-MSCs, and also inducing the osteogenic differentiation.

Italian consensus conference on guidelines for conservative treatment on lower limb muscle injuries in athlete

Provide the state of the art concerning (1) biology and aetiology, (2) classification, (3) clinical assessment and (4) conservative treatment of lower limb muscle injuries (MI) in athletes. Seventy international experts with different medical backgrounds participated in the consensus conference. They discussed and approved a consensus composed of four sections which are presented in these documents. This paper represents a synthesis of the consensus conference, the following four sections are discussed: (i) The biology and aetiology of MIs. A definition of MI was formulated and some key points concerning physiology and pathogenesis of MIs were discussed. (ii) The MI classification. A classification of MIs was proposed. (iii) The MI clinical assessment, in which were discussed anamnesis, inspection and clinical examination and are provided the relative guidelines. (iv) The MI conservative treatment, in which are provided the guidelines for conservative treatment based on the severity of the lesion. Furthermore, instrumental therapy and pharmacological treatment were discussed. Knowledge of the aetiology and biology of MIs is an essential prerequisite in order to plan and conduct a rehabilitation plan. Another important aspect is the use of a rational MI classification on prognostic values. We propose a classification based on radiological investigations performed by ultrasonography and MRI strongly linked to prognostic factors. Furthermore, the consensus conference results will able to provide fundamental guidelines for diagnostic and rehabilitation practice, also considering instrumental therapy and pharmacological treatment of MI. Expert opinion, level IV.

In Utero Stem Cell Transplantation: Potential Therapeutic Application for Muscle Diseases

Muscular dystrophies, myopathies, and traumatic muscle injury and loss encompass a large group of conditions that currently have no cure. Myoblast transplantations have been investigated as potential cures for these conditions for decades. However, current techniques lack the ability to generate cell numbers required to produce any therapeutic benefit. In utero stem cell transplantation into embryos has been studied for many years mainly in the context of hematopoietic cells and has shown to have experimental advantages and therapeutic applications. Moreover, patient-derived cells can be used for experimental transplantation into nonhuman animal embryos via in utero injection as the immune response is absent at such early stages of development. We therefore propose in utero transplantation as a potential method to generate patient-derived humanized skeletal muscle as well as muscle stem cells in animals for therapeutic purposes as well as patient-specific drug screening.

From skeletal muscle to stem cells: an innovative and minimally-invasive process for multiple species

Bone marrow and adipose tissue represent the two most commonly exploited sources of adult mesenchymal stem cells for musculoskeletal applications. Unfortunately the sampling of bone marrow and fat tissue is invasive and does not always lead to a sufficient number of cells. The present study describes a novel sampling method based on microbiopsy of skeletal muscle in man, pigs, dogs and horses. The process includes explant of the sample, Percoll density gradient for isolation and subsequent culture of the cells. We further characterized the cells and identified their clonogenic and immunomodulatory capacities, their immune-phenotyping behavior and their capability to differentiate into chondroblasts, osteoblasts and adipocytes. In conclusion, this report describes a novel and easy-to-use technique of skeletal muscle-derived mesenchymal stem cell harvest, culture, characterization. This technique is transposable to a multitude of different animal species.

Effect of mesenchymal stem cells on induced skeletal muscle chemodenervation atrophy in adult male albino rats

The present research was conducted to evaluate the effect of bone marrow derived mesenchymal stem cells (BM-MSCs) as a potential therapeutic tool for improvement of skeletal muscle recovery after induced chemodenervation atrophy by repeated local injection of botulinum toxin-A in the right tibialis anterior muscle of adult male albino rats. Forty five adult Wistar male albino rats were classified into control and experimental groups. Experimental group was further subdivided into 3 equal subgroups; induced atrophy, BM-MSCs treated and recovery groups. Biochemical analysis of serum LDH, CK and Real-time PCR for Bcl-2, caspase 3 and caspase 9 was measured. Skeletal muscle sections were stained with H and E, Mallory trichrome, and Immunohistochemical reaction for Bax and CD34. Improvement in the skeletal muscle histological structure was noticed in BM-MSCs treated group, however, in the recovery group, some sections showed apparent transverse striations and others still affected. Immunohistochemical reaction of Bax protein showed strong positive immunoreaction in the cytoplasm of muscle fibers in the induced atrophy group. BM-MSCs treated group showed weak positive reaction while the recovery group showed moderate reaction in the cytoplasm of muscle fibers. Immunohistochemical reaction for CD34 revealed occasional positive CD34 stained cells in the induced atrophy group. In BM-MSCs treated group, multiple positive CD34 stained cells were detected. However, recovery group showed some positive CD34 stained cells at the periphery of the muscle fibers. Marked improvement in the regenerative capacity of skeletal muscles after BM-MSCs therapy. Hence, stem cell therapy provides a new hope for patients suffering from myopathies and severe injuries.

Contributions of muscle-resident progenitor cells to homeostasis and disease

Adult skeletal muscle maintains a homeostatic state with modest levels of cellular turnover, unlike the skin or blood. However, the muscle is highly sensitive to tissue injury, which unleashes a cascade of regenerative and inflammatory processes. Muscle regeneration involves cross-talk between numerous cytokine signaling axes, and the coordinated activity of multiple muscle-resident and circulating progenitor populations. Satellite cells, closely associated with myofibers, are established as the canonical muscle stem cell, with self-renewal and myofiber-regenerating capacity. However, a heterogeneous group of mesenchymal progenitor cells residing within the muscle interstitium are also highly responsive to muscle injury and exhibit varying degrees of regenerative potential. These cells interact with satellite cells via direct and indirect mechanisms to regulate regeneration or repair. We describe the known phylogenetic and functional relationships of the multiple progenitor populations residing within skeletal muscle, their putative roles in the coordination of injury repair, and their possible contributions to health and disease.

Fat deposition and accumulation in the damaged and inflamed skeletal muscle: cellular and molecular players

The skeletal muscle has the capacity to repair damage by the activation and differentiation of fiber sub-laminar satellite cells. Regeneration impairment due to reduced satellite cells number and/or functional capacity leads to fiber substitution with ectopic tissues including fat and fibrous tissue and to the loss of muscle functions. Muscle mesenchymal cells that in physiological conditions sustain or directly contribute to regeneration differentiate in adipocytes in patients with persistent damage and inflammation of the skeletal muscle. These cells comprise the fibro-adipogenic precursors, the PW1-expressing cells and some interstitial cells associated with vessels (pericytes, mesoangioblasts and myoendothelial cells). Resident fibroblasts that are responsible for collagen deposition and extracellular matrix remodeling during regeneration yield fibrotic tissue and can differentiate into adipose cells. Some authors have also proposed that satellite cells themselves could transdifferentiate into adipocytes, although recent results by lineage tracing techniques seem to put this theory to discussion. This review summarizes findings about muscle resident mesenchymal cell differentiation in adipocytes and recapitulates the molecular mediators involved in intramuscular adipose tissue deposition.

Osteogenic cell fractions isolated from mouse tongue muscle

The use of stem cells represents a promising approach for the treatment of bone defects. However, successful treatments rely upon the availability of cells that are easily obtained and that appropriately differentiate into osteoblasts. The tongue potentially represents a source of autologous cells for such purposes. In the present study, the ability of stem cell antigen-1 (Sca-1) positive cells derived from tongue muscle to differentiate into osteoblasts was investigated. The tongue muscles were excised from Jcl-ICR mice and tongue muscle-derived Sca-1-positive cells (TDSCs) were isolated from the tongue muscle using a magnetic cell separation system with microbeads. TDSCs were cultured in plastic dishes or gelatin sponges of β-tricalcium phosphate (β-TCP) with bone differentiation-inducing medium. The expression of osteogenic markers (Runx2, osterix, alkaline phosphatase, fibronectin, osteocalcin, osteonectin and osteopontin) was investigated in cultured TDSCs by western blot analysis. The formation of mineralized matrices was examined using alizarin red S and Von Kossa staining. Bone formation was investigated in cultured TDSCs by hematoxylin-eosin staining and immunohistochemstry. In the present study, the expression of Sca-1 in mouse tongue muscle was demonstrated and TDSCs were isolated at high purity. TDSCs differentiated into cells of osteoblast lineage, as demonstrated by the upregulation of osteoblastic marker expression. The formation of mineralized matrices was confirmed by alizarin red S or Von Kossa staining in vitro. Bone formation was observed in the gelatin sponges of β-TCP, which were subsequently implanted under the skin of the backs of nude mice. These results suggested that TDSCs retain their osteogenic differentiation potential and therefore the tongue muscle may be used as a source of stem cells for bone regeneration.

Expression of Transthyretin during bovine myogenic satellite cell differentiation

Adult myogenesis responsible for the maintenance and repair of muscle tissue is mainly under the control of myogenic regulatory factors (MRFs) and a few other genes. Transthyretin gene (TTR), codes for a carrier protein for thyroxin (T4) and retinol binding protein bound with retinol in blood plasma, plays a critical role during the early stages of myogenesis. Herein, we investigated the relationship of TTR with other muscle-specific genes and report their expression in muscle satellite cells (MSCs), and increased messenger RNA (mRNA) and protein expression of TTR during MSCs differentiation. Silencing of TTR resulted in decreased myotube formation and decreased expression of myosin light chain (MYL2), myosin heavy chain 3 (MYH3), matrix gla protein (MGP), and voltage-dependent L type calcium channel (Cav1.1) genes. Increased mRNA expression observed in TTR and other myogenic genes with the addition of T4 decreased significantly following TTR knockdown, indicating the critical role of TTR in T4 transportation. Similarly, decreased expression of MGP and Cav1.1 following TTR knockdown signifies the dual role of TTR in controlling muscle myogenesis via regulation of T4 and calcium channel. Our computational and experimental evidences indicate that TTR has a relationship with MRFs and may act on calcium channel and related genes.

Isolation, culture, and transplantation of muscle satellite cells

Muscle satellite cells are a stem cell population required for postnatal skeletal muscle development and regeneration, accounting for 2-5% of sublaminal nuclei in muscle fibers. In adult muscle, satellite cells are normally mitotically quiescent. Following injury, however, satellite cells initiate cellular proliferation to produce myoblasts, their progenies, to mediate the regeneration of muscle. Transplantation of satellite cell-derived myoblasts has been widely studied as a possible therapy for several regenerative diseases including muscular dystrophy, heart failure, and urological dysfunction. Myoblast transplantation into dystrophic skeletal muscle, infarcted heart, and dysfunctioning urinary ducts has shown that engrafted myoblasts can differentiate into muscle fibers in the host tissues and display partial functional improvement in these diseases. Therefore, the development of efficient purification methods of quiescent satellite cells from skeletal muscle, as well as the establishment of satellite cell-derived myoblast cultures and transplantation methods for myoblasts, are essential for understanding the molecular mechanisms behind satellite cell self-renewal, activation, and differentiation. Additionally, the development of cell-based therapies for muscular dystrophy and other regenerative diseases are also dependent upon these factors. However, current prospective purification methods of quiescent satellite cells require the use of expensive fluorescence-activated cell sorting (FACS) machines. Here, we present a new method for the rapid, economical, and reliable purification of quiescent satellite cells from adult mouse skeletal muscle by enzymatic dissociation followed by magnetic-activated cell sorting (MACS). Following isolation of pure quiescent satellite cells, these cells can be cultured to obtain large numbers of myoblasts after several passages. These freshly isolated quiescent satellite cells or ex vivo expanded myoblasts can be transplanted into cardiotoxin (CTX)-induced regenerating mouse skeletal muscle to examine the contribution of donor-derived cells to regenerating muscle fibers, as well as to satellite cell compartments for the examination of self-renewal activities.

Looking for the elusive lung stem cell niche

This discourse contains three perspectives on various aspects of Stem Cell Biology and tools available to study and translate into Regenerative Medicine. The lung incessantly faces onslaught of the environment, constantly undergoes oxidative stress, and is an important organ of detoxification. In degenerative diseases and inflammation, the lung undergoes irreversible remodeling that is difficult to therapeutically address and/or transplant a dying tissue. The other difficulty is to study its development and regenerative aspects to best address the aforementioned problems. This perspective therefore addresses- firstly, review of types of stem cells, their pathway of action and models in invertebrate organisms vis-a-vis microenvironment and its dynamics; secondly, stem cells in higher organisms and niche; and lastly data and inference on a novel approach to study stem cell destruction patterns in an injury model and information on putative lung stem cell niche. Stem cells are cryptic cells known to retain certain primitive characteristics making them akin to ancient cells of invertebrates, developmental stages in invertebrates and vertebrates and pliant cells of complex creatures like mammals that demonstrate stimulus-specific behavious, whether to clonally propagate or to remain well protected and hidden within specialized niches, or mobilize and differentiate into mature functionally operative cells to house-keep, repair injury or make new tissues. In lung fibrosis, alveolar epithelium degenerates progressively. In keeping with the goal of regenerative medicine, various models and assays to evaluate long and short term identity of stem cells and their niches is the subject of this perspective. We also report identification and characterization of functional lung stem cells to clarify how stem cell niches counteract this degenerative process. Inferences drawn from this injury model of lung degeneration using a short term assay by tracking side population cells and a long term assay tracking label retaining cells have been presented.

3D reconstitution of nerve-blood vessel networks using skeletal muscle-derived multipotent stem cell sheet pellets

AIM

To cover the large tissue deficits associated with significant loss of function following surgery, a 3D gel-patch-like nerve-vascular reconstitution system was developed using the skeletal muscle-derived multipotent stem cell (Sk-MSC) sheet pellet.

MATERIALS & METHODS

The Sk-MSC sheet pellet was prepared from GFP transgenic mice by the collagenase extraction and 7 days expansion cell culture, and transplanted into a severe muscle damage model with large disruptions to muscle fibers, blood vessels and peripheral nerves.

RESULTS

At 4 weeks after transplantation, engrafted cells contributed to nerve-vascular regeneration associated with cellular differentiation into Schwann cells, perineurial/endoneurial cells, vascular endothelial cells and pericytes. However, skeletal myogenic differentiation was scarcely observed. Paracrine effects regarding donor cells/tissues could also be expected, because of the active expression of neurogenic and vasculogenic factor mRNAs in the sheet pellet.

CONCLUSION

These results indicate that the vigorous skeletal myogenic potential of Sk-MSCs was clearly reduced in the sheet pellet preparation and this method may be a useful adjuvant for nerve-vascular regeneration in various tissue engineering applications.

Isolation and osteogenic differentiation of skeletal muscle‑derived stem cells for bone tissue engineering

The purpose of this study was to investigate the isolation and culture of muscle‑derived stem cells (MDSCs) and their capability to differentiate into osteoblasts in vitro. Skeletal muscle tissue was obtained from double hind limbs of New Zealand white rabbits under sterile conditions and isolated by collagenase digestion. Following passages in basic medium, the primary cells were desmin (+), myosin (+) and CD105 (+). Differentiation of MDSCs was induced by osteogenic medium. Using a 3‑(4,5‑dimethylthiazol‑2‑yl)‑2,5‑diphenyl tetrazolium bromide assay, the differentiated cell population was found to proliferate faster than the undifferentiated. Alkaline phosphatase staining and alizarin red staining revealed that the differentiated cells were mineralized in vitro. Quantitative polymerase chain reaction assays also showed increased mRNA expression of osteogenic genes in differentiated cells. In conclusion, stem cells were successfully isolated and cultured from rabbit skeletal muscle tissue and were able to differentiate into osteoblasts following induction. These observations may indicate an ideal stem cell source for tissue engineering.

Effect of muscle preserved on tendon graft on intra-articular healing in anterior cruciate ligament reconstruction

PURPOSE

The aim of this study was to determine the impact on intra-articular healing of muscle tissue retained on tendon grafts used for anterior cruciate ligament (ACL) reconstruction.

METHODS

In an animal study on 40 New Zealand rabbits, a semi-tendon/semi-muscle graft (SSG) and a total tendon graft (TTG) were individually harvested from the Achilles tendons in each animal. After transecting the ACLs in both knees of each rabbit, SSG and TTG were randomly used on bilateral sides of the knee for ACL reconstruction. After 2, 4, and 8 weeks, functional scoring, gross observations, and histological evaluations of the repaired knees were performed (each time point; n = 10). Biomechanical testing was conducted on remaining animals at 8 weeks (n = 10).

RESULTS

At 2, 4, and 8 weeks after surgery, there were no statistically significant differences in functional scores between the SSG group and TTG group (n.s.). As healing progressed, skeletal muscle on the SSG was gradually absorbed with a corresponding decrease in graft diameter, compared to TTG, at each time point (P < 0.001). However, healing and incorporation of the intra-articular graft in the SSG were more apparent than those in the TTG, based on histology. The vascularity and cellularity in the center of the sample were significantly greater in the SSG group than the TTG group at all the time points (P < 0.01). At 8 weeks, the SSG group's ultimate failure load, yield load, and elongation at failure were significantly less than for the TTG group (P < 0.01). There were no significant differences in stiffness between the two groups with biomechanical testing (n.s.).

CONCLUSION

Results of this study indicate that muscle left on tendon grafts promotes intra-articular healing and remodeling of the graft in a rabbit model. However, excessive amounts of retained skeletal muscle weaken tendon graft's strength for ACL reconstruction. Preserving small amounts of muscle on tendon grafts is feasible for improving the biological success of ACL reconstruction in humans.

Notch1-mediated signaling regulates proliferation of porcine satellite cells (PSCs)

Notch signaling is an evolutionarily conserved cell-cell communication mechanism involved in the regulation of cell proliferation, differentiation and fate decisions of mammalian cells. In the present study, we investigated the possible requirement for Notch signaling in the proliferation and differentiation of porcine satellite cells. We show that Notch1, 2 and 3 are expressed in cultured porcine satellite cells. Knock-down of NOTCH1, but not NOTCH2 and NOTCH3, decreases the proliferation of porcine satellite cells. In contrast, enhancement of NOTCH1 expression via treatment of porcine satellite cells with recombinant NF-κB increases the proliferation of porcine satellite cells. The alteration of porcine satellite cell proliferation is associated with significant changes in the expression of cell cycle related genes (cyclin B1, D1, D2, E1 and p21), myogenic regulatory factors (MyoD and myogenin) and the Notch effector Hes5. In addition, alteration of Notch1 expression in porcine satellite cells causes changes in the expression of GSK3β-3. Taken together, these findings suggest that of the four notch-related genes, Notch1is likely to be required for regulating the proliferation and therefore the maintenance of porcine satellite cells in vivo, and do so through activation of the Notch effector gene Hes5.

Key signalling factors and pathways in the molecular determination of skeletal muscle phenotype

The molecular basis and control of the biochemical and biophysical properties of skeletal muscle, regarded as muscle phenotype, are examined in terms of fibre number, fibre size and fibre types. A host of external factors or stimuli, such as ligand binding and contractile activity, are transduced in muscle into signalling pathways that lead to protein modifications and changes in gene expression which ultimately result in the establishment of the specified phenotype. In skeletal muscle, the key signalling cascades include the Ras-extracellular signal regulated kinase-mitogen activated protein kinase (Erk-MAPK), the phosphatidylinositol 3'-kinase (PI3K)-Akt1, p38 MAPK, and calcineurin pathways. The molecular effects of external factors on these pathways revealed complex interactions and functional overlap. A major challenge in the manipulation of muscle of farm animals lies in the identification of regulatory and target genes that could effect defined and desirable changes in muscle quality and quantity. To this end, recent advances in functional genomics that involve the use of micro-array technology and proteomics are increasingly breaking new ground in furthering our understanding of the molecular determinants of muscle phenotype.

Characterization of lung stem cell niches in a mouse model of bleomycin-induced fibrosis

INTRODUCTION

In lung fibrosis, alveolar epithelium degenerates progressively. The goal of regenerative medicine is to aid repair and regeneration of the lost tissues in parenchyma and airways for which mobilization of tissue-resident endogenous or bone marrow-derived exogenous stem cells niches is a critical step. We used a lung injury model in mice to identify and characterize functional lung stem cells to clarify how stem cell niches counteract this degenerative process.

METHODS

Short term assay (STA) - Bleomycin-induced lung inflammation and fibrosis were assessed in a model of idiopathic pulmonary fibrosis in wild-type (WT), gp91phox-/- (NOX-/-), and gp91phoxMMP-12 double knockout (DKO) mice on C57Bl/6 background and Hoechst 33322 dye effluxing side population (SP) cells characterized. Long term assay (LTA) - In a bleomycin induced lung fibrosis model in C57Bl6 mice, the number of mature cells were quantified over 7, 14, and 21 days in bone marrow (BM), peripheral blood (PB), lung parenchyma (LP) and bronchoalveolar lavage (BAL) fluid by FACS. BrdU pulse chase experiment (10 weeks) was used to identify label retaining cells (LRC). BrdU+ and BrdU- cells were characterized by hematopoietic (CD45+), pluripotency (TTF1+, Oct3/4+, SSEA-3+, SSEA-4+, Sca1+, Lin-, CD34+, CD31+), and lung lineage-specific (SPC+, AQP-5+, CC-10+) markers. Clonogenic potential of LRCs were measured by CFU-c assays.

RESULTS

STA- In lung, cellularity increased by 5-fold in WT and 6-fold in NOX-/- by d7. Lung epithelial markers were very low in expression in all SP flow sorted from lung of all three genotypes cultured ex vivo. (p < 0.01). Post-bleomycin, the SP in NOX-/- lung increased by 3.6-fold over WT where it increased by 20-fold over controls. Type I and II alveolar epithelial cells progressively diminished in all three genotypes by d21 post-bleomycin. D7 post-bleomycin, CD45+ cells in BALf in NOX-/- was 1.7-fold > WT, 57% of which were Mf that decreased by 67% in WT and 83% in NOX-/- by d21.LTA- Cellularity as a factor of time remained unchanged in BM, PB, LP and BAL fluid. BrdU+ (LRC) were the putative stem cells. BrdU+CD45+ cells increased by 0.7-fold and SPC+CC10+ bronchoalveolar stem cells (BASC), decreased by ~40-fold post-bleomycin. BrdU+VEGF+ cells decreased by 1.8-fold while BrdU-VEGF+ cells increased 4.6-fold. Most BrdU- cells were CD45-. BrdU- BASCs remained unchanged post-bleomycin. CFU-c of the flow-sorted BrdU+ cells remained similar in control and bleomycin-treated lungs.

CONCLUSION

STA- Inflammation is a pre-requisite for fibrosis; SP cells, being the putative stem cells in the lungs, were increased (either by self renewal or by recruitment from the exogenous bone marrow pool) post-bleomycin in NOX-/- but not in DKO indicating the necessity of cross-talk between gp91phox and MMP-12 in this process; ex vivo cultured SP progressively lose pluripotent markers, notably BASC (SPC+CC10+) - significance is unknown. LTA- The increase in the hematopoietic progenitor pool in lung indicated that exogenous progenitors from circulation contribute to lung regeneration. Most non-stem cells were non-hematopoietic in origin indicating that despite tissue turnover, BASCs are drastically depleted possibly necessitating recruitment of progenitors from the hematopoietic pool. Loss of VEGF+ LRC may indicate a signal for progenitor mobilization from niches. BrdU- BASC population may be a small quiescent population that remains as a reserve for more severe lung injury. Increase in VEGF+ non-LRC may indicate a checkpoint to counterbalance the mobilization of VEGF+ cells from the stem cell niche.

Skeletal Muscle-derived Hematopoietic Stem Cells: Muscular Dystrophy Therapy by Bone Marrow Transplantation

For postnatal growth and regeneration of skeletal muscle, satellite cells, a self-renewing pool of muscle stem cells, give rise to daughter myogenic precursor cells that contribute to the formation of new muscle fibers. In addition to this key myogenic cell class, adult skeletal muscle also contains hematopoietic stem cell and progenitor cell populations which can be purified as a side population (SP) fraction or as a hematopoietic marker CD45-positive cell population. These muscle-derived hematopoietic stem/progenitor cell populations are surprisingly capable of differentiation into hematopoietic cells both after transplantation into irradiated mice and during in vitro colony formation assay. Therefore, these muscle-derived hematopoietic stem/progenitor cells appear to have characteristics similar to classical hematopoietic stem/progenitor cells found in bone marrow. This review outlines recent findings regarding hematopoietic stem/progenitor cell populations residing in adult skeletal muscle and discusses their myogenic potential along with their role in the stem cell niche and related cell therapies for approaching treatment of Duchenne muscular dystrophy.

Conditional TGF-β1 treatment increases stem cell-like cell population in myoblasts

The limitation in successfully acquiring large populations of stem cell has impeded their application. A new method based on the dedifferentiation of adult somatic cells to generate induced multipotent stem cells would allow us to obtain a large amount of autologous stem cells for regenerative medicine. The current work was proposed to induce a sub-population of cells with characteristics of muscle stem cells from myoblasts through conditional treatment of transforming growth factor (TGF)-β(1) . Our results show that a lower concentration of TGF-β(1) is able to promote C2C12 myoblasts to express stem cell markers as well as to repress myogenic proteins, which involves a mechanism of dedifferentiation. Moreover, TGF-β(1) treatment promoted the proliferation-arrested C2C12 myoblasts to re-enter the S-phase. We also investigated the multi-differentiation potentials of the dedifferentiated cells. TGF-β(1) pre-treated C2C12 myoblasts were implanted into mice to repair dystrophic skeletal muscle or injured bone. In addition to the C2C12 myoblasts, similar effects of TGF-β(1) were also observed in the primary myoblasts of mice. Our results suggest that TGF-β(1) is effective as a molecular trigger for the dedifferentiation of skeletal muscle myoblasts and could be used to generate a large pool of progenitor cells that collectively behave as multipotent stem cell-like cells for regenerative medicine applications.

Stem cells in the treatment of patients with coronary heart disease. Part I

Heart failure (HF) is one of the leading death causes in patients with myocardial infarction (MI). The modern methods of reperfusion MI therapy, such as thrombolysis, surgery and balloon revascularization, even when performed early, could fail to prevent the development of large myocardial damage zones, followed by HF. Therefore, the researches have been searching for the methods which improve functional status of damaged myocardium. This review is focused on stem cell therapy, a method aimed at cardiac function restoration. The results of experimental and clinical studies on stem cell therapy in coronary heart disease are presented. Various types of stem cells, used for cellular cardiomyoplasty, are characterised. The methods of cell transplantation into myocardium and potential adverse effects of stem cell therapy are discussed.

Regulation of skeletal muscle regeneration by CCR2-activating chemokines is directly related to macrophage recruitment

Muscle regeneration requires CC chemokine receptor 2 (CCR2) expression on bone marrow-derived cells; macrophages are a prominent CCR2-expressing cell in this process. CCR2-/- mice have severe impairments in angiogenesis, macrophage recruitment, and skeletal muscle regeneration following cardiotoxin (CTX)-induced injury. However, multiple chemokines activate CCR2, including monocyte chemotactic proteins (MCP)-1, -3, and -5. We hypothesized that MCP-1 is the chemokine ligand that mediates the impairments present in CCR2-/- mice. We examined muscle regeneration, capillary density, and cellular recruitment in MCP-1-/- and CCR2-/- mice following injury. Muscle regeneration and adipocyte accumulation, but not capillary density, were significantly impaired in MCP-1-/- compared with wild-type (WT) mice; however, muscle regeneration and adipocyte accumulation impairments were not as severe as observed in CCR2-/- mice. Although tissue levels of MCP-5 were elevated in MCP-1-/- mice compared with WT, the administration of MCP-5 neutralizing antibody did not alter muscle regeneration in MCP-1-/- mice. While neutrophil accumulation after injury was similar in all three mouse strains, macrophage recruitment was highest in WT mice, intermediate in MCP-1-/- mice, and severely impaired in CCR2-/- mice. In conclusion, while the absence of MCP-1 resulted in impaired macrophage recruitment and muscle regeneration, MCP-1-/- mice exhibit an intermediate phenotype compared with CCR2-/- mice. Intermediate macrophage recruitment in MCP-1-/- mice was associated with similar capillary density to WT, suggesting that fewer macrophages may be needed to restore angiogenesis vs. muscle regeneration. Finally, other chemokines, in addition to MCP-1 and MCP-5, may activate CCR2-dependent regenerative processes resulting in an intermediate phenotype in MCP-1-/- mice.

The effects of DNA methyltransferase inhibitors and histone deacetylase inhibitors on digit regeneration in mice

METHOD

We injected two drugs that modify the epigenome, the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine (5-aza-dC) and the histone deacetylase inhibitor trichostatin A (TSA), alone or in combination, into C57Bl/6 mice subjected to amputation through the mid-second phalanx of the third digit. Wound-site tissue was collected.

RESULTS

We observed increased staining of the stem cell markers Rex1 (Zfp42) and stem cell antigen-1 at digit amputation sites from drug-treated mice. Samples from 5-aza-dC plus TSA and TSA treated mice also showed increased proliferating cell nuclear antigen staining, a measure of cell proliferation. Drug treatments increased Msx1, but not Cyp26a1 or ALDH1a2 (RALDH2) mRNA.

CONCLUSION

5-aza-dC and TSA treatments stimulated cell proliferation at the amputation site, possibly via increased expression of genes involved in digit development and regeneration.

1,25(OH)2vitamin D3 inhibits cell proliferation by promoting cell cycle arrest without inducing apoptosis and modifies cell morphology of mesenchymal multipotent cells

The vitamin D receptor (VDR) and its ligand 1,25D play an important role in regulating cell growth and cell fate. We examined the effect of 1,25D on cell morphology, cell proliferation, cell cycle progression and apoptosis on mesenchymal multipotent cells. Multipotent cells were treated with and without 1,25D in a time- and dose-dependent manner. Changes in cell morphology were evaluated by a green fluorescence fluorocrome. Cell proliferation was determined by the Formazan assay and PCNA antigen expression. The expression of genes related to the cell cycle was analyzed by DNA microarrays, RT(2)PCR arrays and western blots. Apoptosis was evaluated by TUNEL assay, and the expression of pro- and anti-apoptotic related genes by RT(2)PCR arrays and western blots. 1,25D inhibited cell proliferation, induced cell cycle arrest, and promoted accumulation of cells in G0/G1 phase without inducing apoptosis. An increase in cell size was associated with a decrease in the GTPase Rho and the atypical Rho family GTPase Rhou/Wrch-1 expression without inducing Wnt-1 expression. Survivin expression was also increased and may represent a novel 1,25D-mediated pathway regulating tissue injury and fibrosis. The data provide a mechanistic explanation for the anti-proliferative and anti-apoptotic properties of 1,25D in mesenchymal multipotent cells.

Identification and characterization of a non-satellite cell muscle resident progenitor during postnatal development

Satellite cells are resident myogenic progenitors in postnatal skeletal muscle involved in muscle postnatal growth and adult regenerative capacity. Here, we identify and describe a population of muscle-resident stem cells, which are located in the interstitium, that express the cell stress mediator PW1 but do not express other markers of muscle stem cells such as Pax7. PW1(+)/Pax7(-) interstitial cells (PICs) are myogenic in vitro and efficiently contribute to skeletal muscle regeneration in vivo as well as generating satellite cells and PICs. Whereas Pax7 mutant satellite cells show robust myogenic potential, Pax7 mutant PICs are unable to participate in myogenesis and accumulate during postnatal growth. Furthermore, we found that PICs are not derived from a satellite cell lineage. Taken together, our findings uncover a new and anatomically identifiable population of muscle progenitors and define a key role for Pax7 in a non-satellite cell population during postnatal muscle growth.

Hyaluronan: is it a biomarker for adipose development within bovine muscle?

Based on an association with extracellular matrix remodelling, mitosis, proliferation and adipogenic differentiation, the glycosaminoglycan hyaluronan (HA) was assessed as a marker for intramuscular fat (IMF) development (marbling) in bovine loin muscle (longissimus dorsi, LD). Loin samples collected from the quartering site of feedlot-finished Wagyu–Angus and Jersey–Limousin steers were assayed for percentage IMF (IMF%) and HA after assignment of AUS-MEAT marbling scores. There was a moderate phenotypic correlation (r2 = 0.69) between IMF% and marbling score but little variance was explained by HA concentration. Breed was not a significant factor in marbling score or IMF% but did influence the HA concentration of the LD, with Wagyu–Angus steers having 2-fold more HA than Jersey–Limousin steers at the same marbling score. The non-linear decline in fat-adjusted HA levels as marbling score increased suggests that HA concentration was associated with lean growth potential of the muscle rather than adipogenesis. Using a different experimental approach, differences in distribution and amount of HA could not be discerned in histological sections of LD from age-matched Wagyu–Hereford heifers allocated to a low (score 1) or medium (score 3) marbling score group. These findings were consistent with the absence of differences between the two groups for other indicators of fatness (IMF% and P8 fat depth), maturity and myofibre characteristics despite an increase in oxidative capacity of the muscle with age. The data support the conclusion that the concentration of HA in the LD alone was not predictive of development of intramuscular fat.

OPLA scaffold, collagen I, and horse serum induce an higher degree of myogenic differentiation of adult rat cardiac stem cells

In the last few years, a major goal of cardiac research has been to drive stem cell differentiation to replace damaged myocardium. Several research groups have attempted to differentiate potential cardiac stem cells (CSCs) using bi- or three-dimensional systems supplemented with growth factors or molecules acting as differentiating substances. We hypothesize that these systems failed to induce a complete differentiation because they lacked an architectural space. In the present study, we isolated a pool of small proliferating and fibroblast-like cells from adult rat myocardium. The phenotype of these cells was assessed and the characterized cells were cultured in a collagen I/OPLA scaffold with horse serum to obtain fine myocardial differentiation. C-Kit(POS)/Sca-1(POS) CSCs fully differentiated in vitro when an environment more similar to the CSC niche was created. These experiments demonstrated an important model for the study of the biology of CSCs and the biochemical pathways that lead to myocardial differentiation. The results pave the way for a new surgical approach.

Identification, isolation and expansion of myoendothelial cells involved in leech muscle regeneration

Adult skeletal muscle in vertebrates contains myoendothelial cells that express both myogenic and endothelial markers, and which are able to differentiate into myogenic cells to contribute to muscle regeneration. In spite of intensive research efforts, numerous questions remain regarding the role of cytokine signalling on myoendothelial cell differentiation and muscle regeneration. Here we used Hirudo medicinalis (Annelid, leech) as an emerging new model to study myoendothelial cells and muscle regeneration. Although the leech has relative anatomical simplicity, it shows a striking similarity with vertebrate responses and is a reliable model for studying a variety of basic events, such as tissue repair. Double immunohistochemical analysis were used to characterize myoendothelial cells in leeches and, by injecting in vivo the matrigel biopolymer supplemented with the cytokine Vascular Endothelial Growth Factor (VEGF), we were able to isolate this specific cell population expressing myogenic and endothelial markers. We then evaluated the effect of VEGF on these cells in vitro. Our data indicate that, similar to that proposed for vertebrates, myoendothelial cells of the leech directly participate in myogenesis both in vivo and in vitro, and that VEGF secretion is involved in the recruitment and expansion of these muscle progenitor cells.

Ras activation contributes to the maintenance and expansion of Sca-1pos cells in a mouse model of breast cancer

The cancer stem cell (CSC) hypothesis proposes that CSCs are the root of cancer and cause cancer metastasis and recurrence. In this study, we examined whether Ras signaling is associated with stemness of the CSCs population characterized by the stem cell antigen (Sca-1) phenotype in a 4T1 syngeneic mouse model of breast cancer. The Sca-1(pos) putative CSCs had high levels of activated Ras and phosphorylated MEK (p-MEK), compared with counterparts. The Ras farnesylation inhibitor (FTI-277) suppressed the maintenance and expansion of CSCs. Therefore, selective inhibition of Ras activation may be useful for stem-specific cancer therapy.

Acute effect of bupivacaine and ricin mAb 35 on extraocular muscle in the rabbit

PURPOSE

To identify acute histologic change of extraocular muscles induced by bupivacaine or ricin mAb 35 injection.

METHODS

The superior rectus and inferior rectus of white rabbits were injected with bupivacaine (0.4 mg in 0.3 ml) or ricin mAb 35 (0.2 microg/kg in 0.3 ml). After 1, 2, and 4 weeks, the rectus muscles were harvested, and postinjection changes in the muscle layers were examined histopathologically.

RESULTS

Bupivacaine and ricin mAb 35 induced myotoxic changes in both the orbital and the global layers. However, the inflammation and the myofiber destruction produced by bupivacaine injection was localized to the injection site, which compared with the diffuse change induced by ricin mAb 35. Inflammation reduced rapidly over 2 weeks. Regenerating myofibers with a central nucleus were found at 1 week after injecting these myotoxins. Four weeks after injection, the acute changes induced by these two toxins respectively were much recovered with prominent myofiber regeneration.

CONCLUSIONS

We found that extraocular muscle has a superb ability to recover from the acute injury induced by bupivacaine or ricin mAb 35, and the two myotoxins induce unique damage including the predilection of muscle layers and duration of damage persisted. Further investigation about the functional change during recovery from the myotoxin-induced injury of extraocular muscles is needed.

Stem cell sources for regenerative medicine

Tissue-resident stem cells or primitive progenitors play an integral role in homeostasis of most organ systems. Recent developments in methodologies to isolate and culture embryonic and somatic stem cells have many new applications poised for clinical and preclinical trials, which will enable the potential of regenerative medicine to be realized. Here, we overview the current progress in therapeutic applications of various stem cells and discuss technical and social hurdles that must be overcome for their potential to be realized.

Inhibition of mammalian muscle differentiation by regeneration blastema extract of Sternopygus macrurus

Tissue regeneration through stem cell activation and/or cell dedifferentiation is widely distributed across the animal kingdom. By comparison, regeneration in mammals is poor and this may reflect a limited dedifferentiation potential of mature cells. Because mammalian myotubes can dedifferentiate in the presence of newt blastema extract, the present study tested the dedifferentiation induction capability of the blastema from the teleost Sternopygus macrurus (SmBE). Our in vitro data showed that SmBE did not induce cell cycle reentry of myonuclei in myotubes. Instead, SmBE caused myotubes to detach and time-lapse imaging analyses characterized the cellular events before their detachment. Furthermore, SmBE enhanced myoblast proliferation and reversibly inhibited their differentiation. These data suggest the presence of protein factors in SmBE that regulate mammalian muscle physiology and differentiation, but do not support the conservation of a dedifferentiation induction capability by the blastema of S. macrurus.

Insights into the transcriptional and chromatin regulation of mesenchymal stem cells in musculo-skeletal tissues

Utilizing adult stem cells for regenerative medicine of skeletal tissues requires the development of molecular and biochemical tools that will allow isolation of these cells and direction of their differentiation towards a desired lineage and tissue formation. Stem cell commitment and fate decision into specialized functional cells involve coordinated activation and silencing of lineage-specific genes. Transcription factors and chromatin-remodeling proteins are key players in the control process of lineage commitment and differentiation during embryogenesis and adulthood. Transcription factors act in cooperation with co-regulator proteins to generate tissue-specific responses that elicits the tissue specific gene expression. Consequently, one of the main challenges of today's research is to characterize molecular pathways that coordinate the lineage-specific differentiation. Epigenetic regulation includes chromatin remodeling that control structural changes of DNA required for the binding of transcription factors to promoter regions. Revealing the mechanisms of action of such factors will provide understanding of how transcription and chromatin regulatory factors function together to regulate stem cell lineage fate decision.

Characterization of adipose tissue-derived cells isolated with the Celution system

BACKGROUND

The therapeutic potential of using stem cells is tremendous. Mesenchymal stromal cells (MSC) have now been isolated in various tissues including bone marrow (BM), muscle, skin and adipose tissue. Among them, adipose tissue could be one of the most suitable cell sources for cell therapy, because of its easy accessibility, minimal morbidity and abundance of stem cells. The large numbers of stem cells in adipose tissue means that clinically relevant stem cell numbers could be extracted from the tissue, potentially eliminating the need for in vitro expansion. To utilize these characteristics of adipose tissue fully, Cytori Therapeutics Inc. has developed a closed system called Celution to isolate and concentrate stem cells and regenerative cells automatically from adipose tissue.

METHODS

Adipose tissue-derived cells were isolated using the Celution system. The output from the Celution was characterized using multicolor FACS analysis with CD31, CD34, CD45, CD90, CD105 and CD146. The multidifferentiation potential of the cells was analyzed using adipogenic and osteogenic media.

RESULTS

Our results showed that cells from the Celution are composed of heterogeneous cell populations including adipose-derived stem cells (ASC) (CD31- CD34+ CD45- CD90+ CD105- CD146-), endothelial (progenitor) cells (CD31+ CD34+ CD45- CD90+ CD105- CD146+) and vascular smooth muscle cells (CD31- CD34+ CD45- CD90+ CD105- CD146+). We also confirmed the output contains cells able to differentiate into adipogenic and osteogenic phenotypes. Our results show that cells isolated with the Celution and manually are equivalent.

DISCUSSION

Cells from adipose tissue can be processed by Celution within the time frame of a single surgical procedure. This system could provide a 'real-time' treatment setting that is cost-effective and safe.

IFATS collection: Stem cell antigen-1-positive ear mesenchymal stem cells display enhanced adipogenic potential

Hyperplasia is a major contributor to the increase in adipose tissue mass that is characteristic of obesity. However, the identity and characteristics of cells that can be committed into adipocyte lineage remain unclear. Stem cell antigen 1 (Sca-1) has been used recently as a candidate marker in the search for tissue-resident stem cells. In our quest for biomarkers of cells that can become adipocytes, we analyzed ear mesenchymal stem cells (EMSC), which can differentiate into adipocytes, osteocytes, chondrocytes, and myocytes. Our previous studies have demonstrated that EMSC abundantly expressed Sca-1. In the present study, we have analyzed the expression of adipogenic transcription factors and adipocyte-specific genes in Sca-1-enriched and Sca-1-depleted EMSC fractions. Sca-1-enriched EMSC accumulated more lipid droplets during adipogenic differentiation than Sca-1-depleted. Similarly, EMSC isolated from Sca-1(-/-) mice displayed reduced lipid accumulation relative to EMSC from wild-type controls (p < .01). Comparative analysis of the adipogenic differentiation process between Sca-1-enriched and Sca-1-depleted populations of EMSC revealed substantial differences in the gene expression. Preadipocyte factor 1, CCAAT enhancer-binding protein (C/EBP) beta, C/EBPalpha, peroxisome proliferator-activated receptor gamma2, lipoprotein lipase, and adipocyte fatty acid binding protein were expressed at significantly higher levels in the Sca-1-enriched EMSC fraction. However, the most striking observation was that leptin was detected only in the conditioned medium of Sca-1-enriched EMSC. In addition, we performed loss-of-function (Sca-1 morpholino oligonucleotide) experiments. The data presented here suggest that Sca-1 is a biomarker for EMSC with the potential to become functionally active adipocytes. Disclosure of potential conflicts of interest is found at the end of this article.

Tumor necrosis factor-alpha inhibition of skeletal muscle regeneration is mediated by a caspase-dependent stem cell response

Skeletal muscle is susceptible to injury following trauma, neurological dysfunction, and genetic diseases. Skeletal muscle homeostasis is maintained by a pronounced regenerative capacity, which includes the recruitment of stem cells. Chronic exposure to tumor necrosis factor-alpha (TNF) triggers a muscle wasting reminiscent of cachexia. To better understand the effects of TNF upon muscle homeostasis and stem cells, we exposed injured muscle to TNF at specific time points during regeneration. TNF exposure delayed the appearance of regenerating fibers, without exacerbating fiber death following the initial trauma. We observed modest cellular caspase activation during regeneration, which was markedly increased in response to TNF exposure concomitant with an inhibition in regeneration. Caspase activation did not lead to apoptosis and did not involve caspase-3. Inhibition of caspase activity improved muscle regeneration in either the absence or the presence of TNF, revealing a nonapoptotic role for this pathway in the myogenic program. Caspase activity was localized to the interstitial cells, which also express Sca-1, CD34, and PW1. Perturbation of PW1 activity blocked caspase activation and improved regeneration. The restricted localization of Sca-1+, CD34+, PW1+ cells to a subset of interstitial cells with caspase activity reveals a critical regulatory role for this population during myogenesis, which may directly contribute to resident muscle stem cells or indirectly regulate stem cells through cell-cell interactions.

Increased survival of muscle stem cells lacking the MyoD gene after transplantation into regenerating skeletal muscle

MyoD is a myogenic master transcription factor that plays an essential role in muscle satellite cell (muscle stem cell) differentiation. To further investigate the function of MyoD in satellite cells, we examined the transplantation of satellite cell-derived myoblasts lacking the MyoD gene into regenerating skeletal muscle. After injection into injured muscle, MyoD(-/-) myoblasts engrafted with significantly higher efficiency compared with wild-type myoblasts. In addition, MyoD(-/-) myoblast-derived satellite cells were detected underneath the basal lamina of muscle fibers, indicating the self-renewal property of MyoD(-/-) myoblasts. To gain insights into MyoD gene deficiency in muscle stem cells, we investigated the pathways regulated by MyoD by GeneChip microarray analysis of gene expression in wild-type and MyoD(-/-) myoblasts. MyoD deficiency led to down-regulation of many muscle-specific genes and up-regulation of some stem cell markers. Importantly, in MyoD(-/-) myoblasts, many antiapoptotic genes were up-regulated, whereas genes known to execute apoptosis were down-regulated. Consistent with these gene expression profiles, MyoD(-/-) myoblasts were revealed to possess remarkable resistance to apoptosis and increased survival compared with wild-type myoblasts. Forced expression of MyoD or the proapoptotic protein Puma increased cell death in MyoD(-/-) myoblasts. Therefore, MyoD(-/-) myoblasts may preserve stem cell characteristics, including their resistance to apoptosis, expression of stem cell markers, and efficient engraftment and contribution to satellite cells after transplantation. Furthermore, our data offer evidence for improved therapeutic stem cell transplantation for muscular dystrophy, in which suppression of MyoD in myogenic progenitors would be beneficial to therapy by providing a selective advantage for the expansion of stem cells.

Isolation and development of haematopoietic progenitor cells from peripheral blood of adult and newborn pigs

Pluripotent stem cells (PSCs), already described in human beings, are fibroblast-like cells that exhibit a CD34 marker specific for haematopoietic stem cells. In this work we have demonstrated the presence of PSCs in the peripheral blood of pigs, a species frequently used in transplantation studies as an animal model for human diseases. Differentiation into haematopoietic colonies (granulomacrophagic colonies, erythroid colonies and mixed colonies) has been carried out with the peripheral blood of adult and newborn pigs, using solely human commercial media. Peripheral blood mononuclear cells (PBMNCs) were cultured in semisolid methylcellulose based media enriched with recombinant human cytokines, achieving granulomacrophagic-colony forming unit (GM-CFU) and mixed-colony forming unit (Mix-CFU) growth with erythroblastic lineage proliferation in the presence of erythropoietin (Epo). In all the samples CFU growth was associated with the presence of recombinant human cytokine. No evidence of proliferation in control plates without cytokines was found. From liquid medium culture, a population of macrophages and CD34+ fibroblast like cells were retrieved 21 days after sowing. These findings allow us to think about the direct application of this simple and standardised method in several work fields such as the study of pharmacological effects of many drugs over the haematopoietic line and in the study of new strategies in cellular therapy for some human diseases.

Progenitor cells and retinal angiogenesis

Nothing more dramatically captures the imagination of the visually impaired patient or the ophthalmologist treating them than the possibility of rebuilding a damaged retina or vasculature with "stem cells." Stem cells (SC) have been isolated from adult tissues and represent a pool of cells that may serve to facilitate rescue/repair of damaged tissue following injury or stress. We propose a new paradigm to "mature" otherwise immature neovasculature or, better yet, stabilize existing vasculature to hypoxic damage. This may be possible through the use of autologous bone marrow (BM) or cord blood derived hematopoietic SC that selectively target sites of neovascularization and gliosis where they provide vasculo- and neurotrophic effects. We have demonstrated that adult BM contains a population of endothelial and myeloid progenitor cells that can target activated astrocytes, a hallmark of many ocular diseases, and participate in normal developmental, or injury-induced, angiogenesis in the adult. Intravitreal injection of these cells from mice and humans can prevent retinal vascular degeneration ordinarily observed in mouse models of retinal degeneration; this vascular rescue correlates with functional neuronal rescue as well. The use of autologous adult BM derived SC grafts for the treatment of retinal vascular and degenerative diseases represents a novel conceptual approach that may make it possible to "mature" otherwise immature neovasculature, stabilize existing vasculature to hypoxic damage and/or rescue and protect retinal neurons from undergoing apoptosis. Such a therapeutic approach would obviate the need to employ destructive treatment modalities and would facilitate vascularization of ischemic and otherwise damaged retinal tissue.

Growth mechanism of satellite cells in human urethral rhabdosphincter

AIMS

To examine the presence of satellite cells in human urethral rhabdosphincter (RS) and to clarify the growth mechanism of these cells.

METHODS

Human RS was obtained from patients undergoing radical prostatectomy for prostate cancer. Primary cells were selectively cultured by magnetic affinity cell sorting (MACS) using an anti-neural cell adhesion molecule (NCAM) antibody. Selectively cultured cells, transfected with simian virus-40 T antigen to extend their lifespan, were used for the following experiments: (1) determination of the effects of hepatocyte growth factor (HGF), insulin-like growth factor-1 (IGF-1), and basic fibroblast growth factor (b-FGF); (2) clarification of the signal transduction pathways used by these growth factors; and (3) examination of the autocrine actions in these cells.

RESULTS

Selectively cultured cells expressed striated muscle markers and could differentiate into myotubes. HGF and IGF-1 stimulated the growth of these cells in a dose-dependent fashion. Regarding signal transduction, HGF phosphorylated ERK1/2 for 120 min while only transiently modifying Akt. In contrast, IGF-1 phosphorylated Akt but not ERK1/2. Furthermore, these cells produced transcripts and proteins for both HGF and IGF-1, and anti-HGF and anti-IGF-1 antibodies suppressed cell proliferation.

CONCLUSIONS

Satellite cells are present in human RS. The proliferation of these cells is primarily enhanced through both the endogenous and exogenous actions of HGF and IGF-I via ERK1/2 and Akt. These findings may be useful in the development of a novel technique for the regeneration of human RS to treat urinary incontinence.

Muscling in on stem cells

Skeletal muscle is one of the few adult tissues that possesses the capacity for regeneration (restoration of lost functional tissue) as opposed to repair. This capacity is due to the presence of 'muscle stem cells' known as satellite cells. Detailed investigation of these cells over the past 50 years has revealed that both these and other cells within the skeletal muscle complex are capable of regenerating both muscle and other cell types as well. Here, we review this information, and suggest that skeletal muscle is an exciting reservoir of cells for regenerating skeletal muscle itself, as well as other cell types.

Side population (SP) cells isolated from fetal rat calvaria are enriched for bone, cartilage, adipose tissue and neural progenitors

In some tissues, stem cells are enriched within the side population (SP) cells characterized by the efficient efflux of Hoechst 33342, but few data are yet available to address whether such is the case in bone tissue. When we Hoechst-stained and FACS-analyzed freshly isolated 20- or 21-day fetal rat calvaria (RC) cells, a small fraction of cells (0.15 +/- 0.05%) comprised of a distinct SP. When SP, non-SP and total/unfractionated (Total) RC cells were plated at a density of 30 cells per microtiter well, the percentage of wells containing bone-forming progenitors (CFU-O) was significantly higher in the SP compared to the non-SP or Total populations (13 +/- 4% vs. 1.8 +/- 0.4% and 0.7 +/- 0.4% respectively). The SP was also highly enriched for CFU-alkaline phosphatase (CFU-ALP) and CFU-fibroblast (CFU-F). While Dex increased the recruitment of CFU-O and CFU-F in the SP, it did not increase the frequency of CFU-ALP. Limiting dilution analysis showed a non-linear relationship between cell densities (1, 5, 10, 20 and 30 cells/microtiter well) and the frequency of readout CFU-O, CFU-ALP and CFU-F in all populations, suggesting a cell non-autonomous component to proliferation-differentiation of these progenitor types. When the developmental potential of SP cells for chondrocyte, adipocyte and neural lineages was assessed, SP cells were also found to be enriched for progenitors of all three lineages. These data demonstrate that Hoechst staining and SP sorting by flow cytometry are a useful strategy for the enrichment of CFU-O and possibly other precursors present in RC cell populations.

Study and culture of haematopoietic progenitor cells from peripheral blood in rats, hamsters and mice

The aim of this work was to isolate and cultivate a subpopulation of pluripotent stem cells present in peripheral blood of different animal species, frequently used in laboratory studies (mice, rats and hamsters). Pluripotent stem cells (PSCs), already described in human beings, are fibroblast-like cells that exhibit a CD34 marker, specific for haematopoietic stem cells. Commonly used human commercial media were investigated for culturing animal PSCs. These findings suggest that this simple and standardized methodology may be applicable in several fields such as the study of the pharmacological effects of drugs on the haematopoietic line and the study of new strategies in cellular therapy for some human diseases.