Muscle-derived stem cells for musculoskeletal tissue regeneration and repair

Biological injection therapy with leukocyte-poor platelet-rich plasma induces cellular alterations, enhancement of lubricin, and inflammatory downregulation in vivo in human knees: A controlled, prospective human clinical trial based on mass spectrometry imaging analysis

Objective

To investigate the in vivo biological effects of leukocyte-poor platelet-rich plasma (LpPRP) treatment in human synovial layer to establish the cellular basis for a prolonged clinical improvement.

Methods

Synovial tissues (n = 367) were prospectively collected from patients undergoing arthroscopic surgery. Autologous-conditioned plasma, LpPRP, was injected into the knees of 163 patients 1-7 days before surgery to reduce operative trauma and inflammation, and to induce the onset of regeneration. A total of 204 patients did not receive any injection. All samples were analyzed by mass spectrometry imaging. Data analysis was evaluated by clustering, classification, and investigation of predictive peptides. Peptide identification was done by tandem mass spectrometry and database matching.

Results

Data analysis revealed two major clusters belonging to LpPRP-treated (LpPRP-1) and untreated (LpPRP-0) patients. Classification analysis showed a discrimination accuracy of 82%-90%. We identified discriminating peptides for CD45 and CD29 receptors (receptor-type tyrosine-protein phosphatase C and integrin beta 1), indicating an enhancement of musculoskeletal stem cells, as well as an enhancement of lubricin, collagen alpha-1-(I) chain, and interleukin-receptor-17-E, dampening the inflammatory reaction in the LpPRP-1 group following LpPRP injection.

Conclusions

We could demonstrate for the first time that injection therapy using "autologic-conditioned biologics" may lead to cellular changes in the synovial membrane that might explain the reported prolonged beneficial clinical effects. Here, we show in vivo cellular changes, possibly based on muscular skeletal stem cell alterations, in the synovial layer. The gliding capacities of joints might be improved by enhancing of lubricin, anti-inflammation by activation of interleukin-17 receptor E, and reduction of the inflammatory process by blocking interleukin-17.

Functionalized Electrospun Scaffold-Human-Muscle-Derived Stem Cell Construct Promotes In Vivo Neocartilage Formation

Polycaprolactone (PCL) is a non-cytotoxic, completely biodegradable biomaterial, ideal for cartilage tissue engineering. Despite drawbacks such as low hydrophilicity and lack of functional groups necessary for incorporating growth factors, it provides a proper environment for different cells, including stem cells. In our study, we aimed to improve properties of scaffolds for better cell adherence and cartilage regeneration. Thus, electrospun PCL–scaffolds were functionalized with ozone and loaded with TGF-β3. Together, human-muscle-derived stem cells (hMDSCs) were isolated and assessed for their phenotype and potential to differentiate into specific lineages. Then, hMDSCs were seeded on ozonated (O) and non-ozonated (“naïve” (NO)) scaffolds with or without protein and submitted for in vitro and in vivo experiments. In vitro studies showed that hMDSC and control cells (human chondrocyte) could be tracked for at least 14 days. We observed better proliferation of hMDSCs in O scaffolds compared to NO scaffolds from day 7 to day 28. Protein analysis revealed slightly higher expression of type II collagen (Coll2) on O scaffolds compared to NO on days 21 and 28. We detected more pronounced formation of glycosaminoglycans in the O scaffolds containing TGF-β3 and hMDSC compared to NO and scaffolds without TGF-β3 in in vivo animal experiments. Coll2-positive extracellular matrix was observed within O and NO scaffolds containing TGF-β3 and hMDSC for up to 8 weeks after implantation. These findings suggest that ozone-treated, TGF-β3-loaded scaffold with hMDSC is a promising tool in neocartilage formation.

Development of a histopathological index for skeletal muscle analysis in Rattus norvegicus (Rodentia: Muridae)

Skeletal muscle histopathological changes induced or caused by pathologies in animal models, can impair functionality, being the main focus of therapeutic studies. This study aimed to propose a histopathological index to assess, in a quantitative manner, skeletal muscle changes induced by experimental protocols for Rodentia's models. For the development, evaluation of fit and parsimony, replicability, and sensitivity index, Wistar rats from experiments with the same experimental design, but with different variation factors, were used to achieve different levels of damage. The anterior tibial muscle of these animals was collected, processed histologically, and stained with hematoxylin and eosin. The adjustment and parsimony of the index were availed through Confirmatory Factor Analysis, reproducibility for evaluation of three people trained through the Intra-Class Correlation, and the discrimination capacity through a one-way ANOVA Test. We pointed out the adjustment for the proposed index while the ICC showed high reproducibility (n = 56; k = 3; ICC = 0.9790) and differences in the extent of damage between groups, following the hierarchical association promoted by experimental model stresses. The results show that the proposed index has a good fit and parsimony (χ² = 426.34; p < 0.0001), in addition to being easily replicable by other researchers who know the morphology of muscle tissue and its morphological changes. It is worth mentioning that the development of tools that facilitate histopathological analysis, and that can quantitatively express the findings, are of great importance for the studies of regenerative science, reinforcing the relevance of this study.

Role of endocrine factors and stem cells in skeletal muscle regeneration

The process of reconstructing damaged skeletal muscles involves degeneration, inflammatory and immune responses, regeneration and reorganization, which are regulated by a number of immune-endocrine factors affecting muscle cells and satellite cells (SCs). One of these molecules is testosterone (T), which binds to the androgen receptor (AR) to initiate the expression of the muscle isoform of insulin-like growth factor 1 (IGF-1Ec). The interaction between T and IGF-1Ec stimulates the growth and regeneration of skeletal muscles by inhibiting apoptosis, enhancement of SCs proliferation and myoblasts differentiation. As a result of sarcopenia, muscle dystrophy or wasting diseases, the SCs population is significantly reduced. Regular physical exercise attenuates a decrease in SCs count, and thus elevates the regenerative potential of muscles in both young and elderly people. One of the challenges of modern medicine is the application of SCs and extracellular matrix scaffolds in regenerative and molecular medicine, especially in the treatment of degenerative diseases and post-traumatic muscle reconstruction. The aim of the study is to present current information on the molecular and cellular mechanisms of skeletal muscle regenera,tion, the role of testosterone and growth factors in the activation of SCs and the possibility of their therapeutic use in stimulating the reconstruction of damaged muscle fibers.

Novel cell sources for bone regeneration

A plethora of both acute and chronic conditions, including traumatic, degenerative, malignant, or congenital disorders, commonly induce bone disorders often associated with severe persisting pain and limited mobility. Over 1 million surgical procedures involving bone excision, bone grafting, and fracture repair are performed each year in the U.S. alone, resulting in immense levels of public health challenges and corresponding financial burdens. Unfortunately, the innate self-healing capacity of bone is often inadequate for larger defects over a critical size. Moreover, as direct transplantation of committed osteoblasts is hindered by deficient cell availability, limited cell spreading, and poor survivability, an urgent need for novel cell sources for bone regeneration is concurrent. Thanks to the development in stem cell biology and cell reprogramming technology, many multipotent and pluripotent cells that manifest promising osteogenic potential are considered the regenerative remedy for bone defects. Considering these cells' investigation is still in its relative infancy, each of them offers their own particular challenges that must be conquered before the large-scale clinical application.

One health in regenerative medicine: report on the second Havemeyer symposium on regenerative medicine in horses

Regenerative medicine is commonly used in human and equine athletes. Potential therapies include culture expanded stem cells, stromal vascular fraction of adipose tissue, platelet-rich plasma, bone marrow concentrate, or autologous conditioned serum. The purpose of this manuscript is to disseminate findings from a workshop on the development of translational regenerative medicine in the equine field. Five themes emerged: stem cell characterization and tenogenic differentiation; interactions between mesenchymal stem cells, other cells and the environment; scaffolds and cell packaging; blood- and bone marrow-based regenerative medicines; clinical use of regenerative therapies. Evidence gained through the use of regenerative medicine applications in the horse should continue to translate to the human patient, bringing novel regenerative therapies to both humans and horses.

Histology of skeletal muscle reconstructed by means of the implantation of autologous adipose tissue: an experimental study

The purpose of this study was to determine the histological characteristics of a skeletal muscle reconstructed by means of the implantation of autologous adipose tissue following an experimentally-induced volumetric muscle loss. A cylindrical piece in the belly of the rat anterior tibial muscle was removed. In the hole, inguinal subcutaneous adipose tissue of the same rat was grafted. Animals were sacrificed 7, 14, 21, 28 and 60 days posttransplantation. Histological, histochemical, immunohistochemical and morphometric techniques were used. At all times analyzed, the regenerative muscle fibers formed from the edges of the muscle tissue showed histological, histochemical and immunohistochemical differences in comparison with the control group. These differences are related to delays in the maturation process and are related to problems in reinnervation and disorientation of muscle fibers. The stains for MyoD and desmin showed that some myoblasts and myotubes seem to derive from the transplanted adipose tissue. After 60 days, the transplant area was 20% occupied by fibrosis and by 80% skeletal muscle. However, the neo-muscle was chaotically organized showing muscle fiber disorientation and centronucleated fibers with irregular shape and size. Our results support the hypothesis that, at least from a morphological point of view, autologous adipose tissue transplantation favors reconstruction following a volumetric loss of skeletal muscle by combining the inherent regenerative response of the organ itself and the myogenic differentiation of the stem cells present in the adipose tissue. However, in our study, the formed neo-muscle exhibited histological differences in comparison with the normal skeletal muscle.

Effects of SW033291 on the myogenesis of muscle-derived stem cells and muscle regeneration

Background

The unmet medical needs in repairing large muscle defects promote the development of tissue regeneration strategy. The use of bioactive molecules in combination with biomaterial scaffold has become an area of great interest. SW033291, a small-molecule inhibitor targeting 15-hydroxyprostaglandin dehydrogenase (15-PDGH) and subsequently elevating the production of prostaglandin E2 (PGE2), has been proved to accelerate the recovery and potentiate the regeneration of multiple tissues including the bone, liver, and colon. The limited understanding of the potential therapeutic effects on myogenesis motivated us to investigate the role of SW033291 in regulating muscle-derived stem cell (MDSC) myogenic differentiation and MDSC-mediated muscle regeneration.

Methods

The characteristics of rat MDSCs, including cell-specific markers and myogenic differentiation potential, were determined. MDSCs were incubated with SW033291 to evaluate PGE2 production and cytotoxicity. The effects of SW033291 on MDSC myogenic differentiation were assessed by quantitative real-time polymerase chain reaction (qPCR), western blot, and immunocytochemistry. The fibrin gel containing MDSCs and SW033291 was used for muscle regeneration in a tibialis anterior muscle defect model.

Results

Our data demonstrated that MDSCs were well-tolerated to SW033291 and treatment with SW033291 significantly promoted the production of PGE2 by MDSCs. In vitro analysis showed that SW033291 enhanced the myogenic differentiation and myotube formation by upregulating a series of myogenic markers. Additionally, the activation of PI3K/Akt pathway was involved in the mechanism underlying these promotive effects. Then, in situ casting of fibrin gel containing MDSCs and SW033291 was used to repair the tibialis anterior muscle defect; the addition of SW033291 significantly promoted myofiber formation within the defect region with mild immune response, less fibrosis, and sufficient vascularization.

Conclusion

SW033291 acted as a positive regulator of MDSC myogenic differentiation, and incorporating the compound with MDSCs in fibrin gel could serve as an effective method to repair large skeletal muscle defects.

Muscle stem cells: what's new in orthopedics?

BACKGROUND AND AIM OF THE WORK

Adult stem cells were studied as a source of potentially useful development for tissue engineering and repair techniques. The aim of this review is to clarify the actual and possible uses of muscle stem cells in orthopedics.

METHODS

A selection of studies was made to obtain a homogeneous and up to date overview on the muscle stem cells applications.

RESULTS

In recent years muscle was studied as a good source of adult stem cells that can differentiate into different cell lineages. Muscle stem cells are a heterogeneous population of cells, which demonstrated in vitro a great potential for the regeneration and repair of muscle, bone and cartilage tissue. Among muscle stem cells, satellite stem cells are the most known progenitor cells: they can differentiate in osteoblasts, adipocytes, chondrocytes and myocytes.

CONCLUSIONS

Although muscle stem cells are a promising field of research, more pre-clinical studies in animal models are still needed to determine the safety and efficiency of the transplant procedures in humans.

Denervated muscle extract promotes recovery of muscle atrophy through activation of satellite cells. An experimental study

PURPOSE

The objective of the present study was to determine whether a denervated muscle extract (DmEx) could stimulate satellite cell response in denervated muscle.

METHODS

Wistar rats were divided into 4 groups: normal rats, normal rats treated with DmEx, denervated rats, and denervated rats treated with DmEx. The soleus muscles were examined using immunohistochemical techniques for proliferating cell nuclear antigen, desmin, and myogenic differentiation antigen (MyoD), and electron microscopy was used for analysis of the satellite cells.

RESULTS

The results indicate that while denervation causes activation of satellite cells, DmEx also induces myogenic differentiation of cells localized in the interstitial space and the formation of new muscle fibers. Although DmEx had a similar effect in nature on innervated and denervated muscles, this response was of greater magnitude in denervated vs. intact muscles.

CONCLUSION

Our study shows that treatment of denervated rats with DmEx potentiates the myogenic response in atrophic denervated muscles.

Sources and Clinical Applications of Mesenchymal Stem Cells: State-of-the-art review

First discovered by Friedenstein in 1976, mesenchymal stem cells (MSCs) are adult stem cells found throughout the body that share a fixed set of characteristics. Discovered initially in the bone marrow, this cell source is considered the gold standard for clinical research, although various other sources-including adipose tissue, dental pulp, mobilised peripheral blood and birth-derived tissues-have since been identified. Although similar, MSCs derived from different sources possess distinct characteristics, advantages and disadvantages, including their differentiation potential and proliferation capacity, which influence their applicability. Hence, they may be used for specific clinical applications in the fields of regenerative medicine and tissue engineering. This review article summarises current knowledge regarding the various sources, characteristics and therapeutic applications of MSCs.

Localized SDF-1α Delivery Increases Pro-Healing Bone Marrow-Derived Cells in the Supraspinatus Muscle Following Severe Rotator Cuff Injury

To examine how the chemotactic agent stromal cell-derived factor-1alpha (SDF-1α) modulates the unique cellular milieu within rotator cuff muscle following tendon injury, we developed an injectable, heparin-based microparticle platform to locally present SDF-1α within the supraspinatus muscle following severe rotator cuff injury. SDF-1α loaded, degradable, N-desulfated heparin-based microparticles were fabricated, injected into a rat model of severe rotator cuff injury, and were retained for up to 7 days at the site. The resultant inflammatory cell and mesenchymal stem cell populations were analyzed compared to uninjured contralateral controls and, after 7 days, the fold-change in anti-inflammatory, M2-like macrophages (CD11b+CD68+CD163+, 4.3X fold-change) and mesenchymal stem cells (CD29+CD44+CD90+, 3.0X, respectively) was significantly greater in muscles treated with SDF-1α loaded microparticles than unloaded microparticles or injury alone. Our results indicate that SDF-1α loaded microparticles may be a novel approach to shift the cellular composition within the supraspinatus muscle and create a more pro-regenerative milieu, which may provide a platform to improve muscle repair following rotator cuff injury in the future.

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.

Proximal Neuropathy and Associated Skeletal Muscle Changes Resembling Denervation Atrophy in Hindlimbs of Chronic Hypoglycaemic Rats

Peripheral neuropathy is one of the most common complications of diabetic hyperglycaemia. Insulin-induced hypoglycaemia (IIH) might potentially exacerbate or contribute to neuropathy as hypoglycaemia also causes peripheral neuropathy. In rats, IIH induces neuropathy associated with skeletal muscle changes. Aims of this study were to investigate the progression and sequence of histopathologic changes caused by chronic IIH in rat peripheral nerves and skeletal muscle, and whether such changes were reversible. Chronic IIH was induced by infusion of human insulin, followed by an infusion-free recovery period in some of the animals. Sciatic, plantar nerves and thigh muscle were examined histopathologically after four or eight weeks of infusion and after the recovery period. IIH resulted in high incidence of axonal degeneration in sciatic nerves and low incidence in plantar nerves indicating proximo-distal progression of the neuropathy. The neuropathy progressed in severity (sciatic nerve) and incidence (sciatic and plantar nerve) with the duration of IIH. The myopathy consisted of groups of angular atrophic myofibres which resembled histopathologic changes classically seen after denervation of skeletal muscle, and severity of the myofibre atrophy correlated with severity of axonal degeneration in sciatic nerve. Both neuropathy and myopathy were still present after four weeks of recovery, although the neuropathy was less severe. In conclusion, the results suggest that peripheral neuropathy induced by IIH progresses proximo-distally, that severity and incidence increase with duration of the hypoglycaemia and that these changes are partially reversible within four weeks. Furthermore, IIH-induced myopathy is most likely secondary to the neuropathy.

Cell therapy for stress urinary incontinence: Present-day frontiers

Stress urinary incontinence (SUI) significantly diminishes the quality of patients' lives. Currently available surgical and nonsurgical therapies remain far from ideal. At present, advances in cellular technologies have stirred growing interest in the use of autologous cell treatments aimed to regain urinary control. The objective was to conduct a review of the literature and analyse preclinical and clinical studies dedicated to various cell therapies for SUI, assessing their effectiveness, safety, and future prospects. A systematic literature search in PubMed was conducted using the following key terms: "stem," "cell," "stress," "urinary," and "incontinence." A total of 32 preclinical studies and 15 clinical studies published between 1946 and December 2014 were included in the review. Most preclinical trials have used muscle-derived stem cells and adipose-derived stem cells. However, at present, the application of other types of cells, such as human amniotic fluid stem muscle-derived progenitor cells and bone marrow mesenchymal stromal cells, is becoming more extensive. While the evidence shows that these therapies are effective and safe, further work is required to standardize surgical techniques, as well as to identify indications for their use, doses and number of doses. Future research will have to focus on clinical applications of cell therapies; namely, it will have to determine indications for their use, doses of cells, optimal surgical techniques and methods, attractive cell sources, as well as to develop clinically relevant animal models and make inroads into understanding the mechanisms of SUI improvement by cell therapies.

New MSC: MSCs as pericytes are Sentinels and gatekeepers

Human Mesenchymal Stem Cells, hMSCs, were first named over 25 years ago with the "stem cell" nomenclature derived from the fact that we and others could cause these cells to differentiate into a number of different mesodermal phenotypes in cell culture. The capacity to form skeletal tissue in vitro encouraged the use of hMSCs for the fabrication of tissue engineered skeletal repair tissue with subsequent transplantation to in vivo sites. With the current realization that MSCs are derived from perivascular cells, pericytes, and the immunomodulatory and trophic capabilities of MSCs in both in vitro and in vivo test systems, a complete re-evaluation of the role and functions of MSCs in the body was required. Additionally, the skeleton is a preferred organ for cancer dissemination from various tumor malignancies. To date, most efforts to understand skeletal metastasis have focused on the invasive and digestive capability of disseminated tumor cells (DTCs). The contribution of the target organ-specific microvascular structure influencing extravasation is less well understood. Current targeted cancer therapies are designed to alter not only biological functions in DTCs, but also components of the tumor stroma/microenvironment such as blood vessels. We now have a comprehensive image of the critical role of the host vasculature as an instructive niche for DTCs. The focus of this manuscript is to present the current information about MSC function in situ and to emphasize how these new observations provide insight into understanding the role of the pericyte/MSC in skeletal activities including our new hypothesis for how these cells act as a gatekeeper for metastasis of melanoma into bone. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1151-1159, 2017.

Bezerra-Junior R, Câmara LM, Albuquerque-Pinto LC, Teixeira MF. Isolation, culture and characterization of multipotent mesenchymal stem cells from goat umbilical cord blood

ABSTRACT: Mesenchymal stem cells (MSC) reside in small numbers in many adult tissues and organs, and play an active role in the homeostasis of these sites. Goat derived multipotent MSC have been established from bone marrow, adipose tissues and amniotic fluid. Umbilical cord blood (UCB) is considered an important source of these cells. However, the MSC isolation from the goat UCB has not been demonstrated. Therefore, the aim of the present study was to isolate, culture and characterize goat umbilical cord blood derived mesenchymal stem cells. MSC were isolated from UCB by Ficoll-Paque density centrifugation and cultured in DMEM supplemented with 10% or 20% FBS. FACS analysis was performed and induction lineage differentiation was made to characterize these cells. They exhibited two different populations in flow cytometry, and revealed the positive expression of CD90, CD44 and CD105, but negative staining for CD34 in larger cells, and positive stained for CD90 and CD105, but negative for CD44 and CD34 in the smaller cells. MSC from goat UCB showed capability to differentiate into chondrocytes and osteoblasts when incubated with specific differentiation medium. Present study established that goat mesenchymal stem cells can be derived successfully from umbilical cord blood.

Goat umbilical cord cells are permissive to small ruminant lentivirus infection in vitro

Small ruminant lentiviruses isolated from peripheral blood leukocytes and target organs can be propagated in vitro in fibroblasts derived from goat synovial membrane cells. These cells are obtained from tissues collected from embryos or fetuses and are necessary for the establishment of the fibroblast primary culture. A new alternative type of host cells, derived from goat umbilical cord, was isolated and characterized phenotypically with its main purpose being to obtain cell monolayers that could be used for the diagnosis and isolation of small ruminant lentiviruses in cell culture. To accomplish this goal, cells were isolated from umbilical cords; characterized phenotypically by flow cytometry analysis; differentiate into osteogenic, chondrogenic and adipogenic lineage; and submitted to viral challenge. The proliferation of goat umbilical cord cells was fast and cell monolayers formed after 15 days. These cells exhibited morphology, immunophenotype, growth characteristics, and lineage differentiation potential similar to mesenchymal stem cells of other origins. The goat umbilical cord derived cells stained positive for vimentin and CD90, but negative for cytokeratin, CD34 and CD105 markers. Syncytia and cell lysis were observed in cell monolayers infected by CAEV-Cork and MVV-K1514, showing that the cells are permissive to small ruminant lentivirus infection in vitro. These data demonstrate the proliferative competence of cells derived from goat umbilical cords and provide a sound basis for future research to standardize this cell lineage.

Driving the Hypoxia-Inducible Pathway in Human Pericytes Promotes Vascular Density in an Exosome-Dependent Manner

OBJECTIVES

The mechanisms involved in activating pericytes, cells that ensheath capillaries, to engage in the formation of new capillaries, angiogenesis, remain unknown. In this study, the hypothesis was tested that pericytes could be stimulated to promote angiogenesis by driving the HIF pathway.

METHODS

Pericytes were stimulated with CoCl2 to activate the HIF pathway. Stimulated pericytes were cocultured with endothelial cells in a wound healing assay and in a 3D collagen matrix assay of angiogenesis. A culture system of spinal cord tissue was used to assess microvascular outcomes after treatment with stimulated pericytes. Pharmaceutical inhibition of exosome production was also performed.

RESULTS

Treatment with stimulated pericytes resulted in faster wound healing (1.92 ± 0.18 fold increase, p < 0.05), greater endothelial cord formation (2.9 ± 0.14 fold increase, p < 0.05) in cell culture assays, and greater vascular density (1.78 ± 0.23 fold increase, p < 0.05) in spinal cord tissue. Exosome secretion and the physical presence of stimulated pericytes were necessary in the promotion of angiogenic outcomes.

CONCLUSIONS

These results elucidate a mechanism that may be exploited to enhance features of angiogenesis in the CNS.

Role of Inflammation in Muscle Homeostasis and Myogenesis

Skeletal muscle mass is subject to rapid changes according to growth stimuli inducing both hypertrophy, through increased protein synthesis, and hyperplasia, activating the myogenic program. Muscle wasting, characteristic of several pathological states associated with local or systemic inflammation, has been for long considered to rely on the alteration of myofiber intracellular pathways regulated by both hormones and cytokines, eventually leading to impaired anabolism and increased protein breakdown. However, there are increasing evidences that even alterations of the myogenic/regenerative program play a role in the onset of muscle wasting, even though the precise mechanisms involved are far from being fully elucidated. The comprehension of the links potentially occurring between impaired myogenesis and increased catabolism would allow the definition of effective strategies aimed at counteracting muscle wasting. The first part of this review gives an overview of skeletal muscle intracellular pathways determining fiber size, while the second part considers the cells and the regulatory pathways involved in the myogenic program. In both parts are discussed the evidences supporting the role of inflammation in impairing muscle homeostasis and myogenesis, potentially determining muscle atrophy.

Proliferation of Multiple Cell Types in the Skeletal Muscle Tissue Elicited by Acute p21 Suppression

Although in the last decades the molecular underpinnings of the cell cycle have been unraveled, the acquired knowledge has been rarely translated into practical applications. Here, we investigate the feasibility and safety of triggering proliferation in vivo by temporary suppression of the cyclin-dependent kinase inhibitor, p21. Adeno-associated virus (AAV)-mediated, acute knockdown of p21 in intact skeletal muscles elicited proliferation of multiple, otherwise quiescent cell types, notably including satellite cells. Compared with controls, p21-suppressed muscles exhibited a striking two- to threefold expansion in cellularity and increased fiber numbers by 10 days post-transduction, with no detectable inflammation. These changes partially persisted for at least 60 days, indicating that the muscles had undergone lasting modifications. Furthermore, morphological hyperplasia was accompanied by 20% increases in maximum strength and resistance to fatigue. To assess the safety of transiently suppressing p21, cells subjected to p21 knockdown in vitro were analyzed for γ-H2AX accumulation, DNA fragmentation, cytogenetic abnormalities, ploidy, and mutations. Moreover, the differentiation competence of p21-suppressed myoblasts was investigated. These assays confirmed that transient suppression of p21 causes no genetic damage and does not impair differentiation. Our results establish the basis for further exploring the manipulation of the cell cycle as a strategy in regenerative medicine.

Electrical stimulation influences satellite cell differentiation after sciatic nerve crush injury in rats

INTRODUCTION

Electrical stimulation is often used to prevent muscle atrophy and preserve contractile function, but its effects on the satellite cell population after nerve injury are not well understood. In this study we aimed to determine whether satellite cell differentiation is affected by electrical stimulation after nerve crush.

METHODS

The sciatic nerves of Sprague-Dawley (SD) rats were crushed. Half of the injured rats received daily electrical stimulation of the gastrocnemius muscle, and the others did not. Tests for detecting paired box protein 7 (Pax7), myogenic differentiation antigen (MyoD), embryonic myosin heavy chain (eMyHC), and force production were performed 2, 4, and 6 weeks after injury.

RESULTS

More Pax7+/MyoD+ nuclei in stimulated muscles were observed than in non-stimulated muscles. eMyHC expression was elevated in stimulated muscles and correlated positively with enhanced force production.

CONCLUSIONS

Increased satellite cell differentiation is correlated with preserved muscle function in response to electrical stimulation after nerve injury.

Expression of insulin-like growth factor type 1 receptor and myosin heavy chain in rabbit's rotator cuff muscle after injection of adipose-derived stem cell

PURPOSE

This study was performed to evaluate the effects of adipose-derived mesenchymal stem cells (ADMSC) in a subacute rotator cuff tear model of a rabbit by way of comparing the expression of insulin-like growth factor 1 receptor (IGF-1R) and myosin heavy chain (MyHC) in the ADMSC injected muscle and control.

METHODS

Supraspinatus tears were created in both shoulders of 11 rabbits, and rotator cuff repair was performed after 3 weeks. At the time of repair, each side of the shoulders was randomly selected, and the injection of the ADMSCs at the muscle belly near musculotendinous junction (injection side) and saline to the contralateral side (control side) was performed. After 3 weeks, we randomly assigned 5 rabbits to the immunohistochemistric analysis and 6 to Western blot analysis.

RESULTS

Expression of both IGF-1R (95 kD) and MyHC (200 kD) at the injection side was significantly elevated compared to control side (both p = 0.028). Immunohistochemistry showed that staining areas of both IGF-1R and MyHC were overlapped with staining of ADMSCs.

CONCLUSION

The injection of ADMSCs resulted in high expression of IGF-1R and MyHC in subacute rotator cuff tear and repaired model in rabbit compared to control side. Therefore, the injected ADMSCs may assist in regeneration of the rotator cuff muscle by way of insulin-like growth factor 1 (IGF-1) signalling pathway. This result may suggest another solution to facilitate the recovery of rotator cuff muscle and to improve the result of rotator cuff repair by ADMSC injection via IGF-1 pathway, which is one of the potent anabolic pathways.

Adipose-derived stem cells extract has a proliferative effect on myogenic progenitors

Finding an effective method to regenerate muscle is a growing issue in the orthopedic field. Platelet-rich plasma (PRP) has recently been considered for therapeutic use due to its capacity to induce proliferation of myogenic progenitor cells (MPCs). Adipose-derived stem cells (ASCs) and its extract are regarded as a promising treatment for various disorders within the orthopedic field but their therapeutic relevance in the muscle regeneration is poorly investigated. In this study, rabbit MPCs were cultured from the supraspinatus of rabbit and characterized by myogenic markers. To investigate the paracrine effect of ASCs on MPCs, coculture experiments were performed. In order to see the anabolic effect of ASC-extracts (ASC-ex) in MPCs, cell proliferation assays were performed and compared with the PRP-added condition. Coculture experiment showed ASCs had an anabolic paracrine effect on proliferation of MPCs. PRP had a positive effect on proliferation of MPCs when compared to the control (100 ± 7.4% vs 195.2 ± 19.2%, p < 0.001); however, ASC-ex promoted greater proliferation than the PRP condition (467.3 ± 38.7%, p < 0.001 compared with PRP). Similarly, in C2C12 cells, PRP showed an increased rate when compared to the control (100 ± 5.9% vs 205.1 ± 45.4%, p < 0.001), and treatment of ASC-ex showed dramatic increase in proliferation (335.9 ± 37.8%, p < 0.001 compared with PRP). ASC-ex had positive effect on expanding MPCs of rabbit and myoblast cell line, and its capacity to induce proliferation was notably stronger than that of PRP. In conclusion, the study suggests that rabbit ASC-ex have stronger proliferative effect on MPCs than rabbit PRP. Thus, ASC-ex could be a therapeutic candidate for muscle regeneration by activation of endogenous MPCs.

Concise review: skeletal muscle stem cells and cardiac lineage: potential for heart repair

Valuable and ample resources have been spent over the last two decades in pursuit of interventional strategies to treat the unmet demand of heart failure patients to restore myocardial structure and function. At present, it is clear that full restoration of myocardial structure and function is outside our reach from both clinical and basic research studies, but it may be achievable with a combination of ongoing research, creativity, and perseverance. Since the 1990s, skeletal myoblasts have been extensively investigated for cardiac cell therapy of congestive heart failure. Whereas the Myoblast Autologous Grafting in Ischemic Cardiomyopathy (MAGIC) trial revealed that transplanted skeletal myoblasts did not integrate into the host myocardium and also did not transdifferentiate into cardiomyocytes despite some beneficial effects on recipient myocardial function, recent studies suggest that skeletal muscle-derived stem cells have the ability to adopt a cardiomyocyte phenotype in vitro and in vivo. This brief review endeavors to summarize the importance of skeletal muscle stem cells and how they can play a key role to surpass current results in the future and enhance the efficacious implementation of regenerative cell therapy for heart failure.

Bearing arms against osteoarthritis and sarcopenia: when cartilage and skeletal muscle find common interest in talking together

Osteoarthritis, a disease characterized by cartilage degradation, abnormal subchondral bone remodelling and some grade of inflammation, and sarcopenia, a condition of pathological muscle weakness associated with altered muscle mass, strength, and function, are prevalent disorders in elderly people. There is increasing evidence that decline in lower limb muscle strength is associated with knee or hip osteoarthritis in a context of pain, altered joint stability, maladapted postures and defective neuromuscular communication. At the cellular and molecular levels, chondrocytes and myoblasts share common pathological targets and pathways, and the close anatomical location of both cell types suggest a possibility of paracrine communication. In this review, we examine the relationship between osteoarthritis and sarcopenia in the musculoskeletal field, and discuss the potential advantage of concomitant therapies, or how each disorder may benefit from treatment of the other.

The Necessity of a Systematic Approach for the Use of MSCs in the Clinical Setting

Cell therapy has emerged as a potential therapeutic strategy in regenerative disease. Among different cell types, mesenchymal stem/stromal cells have been wildly studied in vitro, in vivo in animal models and even used in clinical trials. However, while clinical applications continue to increase markedly, the understanding of their physiological properties and interactions raises many questions and drives the necessity of more caution and supervised strategy in their use.

Satellite cells and the muscle stem cell niche

Adult skeletal muscle in mammals is a stable tissue under normal circumstances but has remarkable ability to repair after injury. Skeletal muscle regeneration is a highly orchestrated process involving the activation of various cellular and molecular responses. As skeletal muscle stem cells, satellite cells play an indispensible role in this process. The self-renewing proliferation of satellite cells not only maintains the stem cell population but also provides numerous myogenic cells, which proliferate, differentiate, fuse, and lead to new myofiber formation and reconstitution of a functional contractile apparatus. The complex behavior of satellite cells during skeletal muscle regeneration is tightly regulated through the dynamic interplay between intrinsic factors within satellite cells and extrinsic factors constituting the muscle stem cell niche/microenvironment. For the last half century, the advance of molecular biology, cell biology, and genetics has greatly improved our understanding of skeletal muscle biology. Here, we review some recent advances, with focuses on functions of satellite cells and their niche during the process of skeletal muscle regeneration.

Vitamin D increases cellular turnover and functionally restores the skeletal muscle after crush injury in rats

Insufficient skeletal muscle regeneration after injury often impedes the healing process and is accompanied by functional deficiencies or pain. The aim of our study was to provide evidence that vitamin D improves muscle healing after muscle injury. Therefore, we used male rats and induced an injury of the soleus muscle. After crush injury, animals received either 8.3 mg/kg (332,000 IU/kg) body weight vitamin D or vehicle solution, s.c. After assessment of muscle force at days 1, 4, 14, and 42 after injury, sampling of muscle tissue served for analysis of proliferation, apoptosis, satellite cells, and prolyl-4-hydroxylase-β expression. Vitamin D application caused a significant increase in cell proliferation and a significant inhibition of apoptosis at day 4 after injury compared to control animals. The numbers of satellite cells were not influenced by the vitamin D application, but there was an increase in prolyl-4-hydroxylase-β expression, indicative of increased extracellular matrix proteins. This cellular turnover resulted in a faster recovery of contraction forces at day 42 in the vitamin D group. Current data support the hypothesis that vitamin D promotes the regenerative process in injured muscle. Thus, vitamin D treatment may represent a promising therapy to optimize recovery after injury.

Human stem cells and articular cartilage regeneration

The regeneration of articular cartilage damaged due to trauma and posttraumatic osteoarthritis is an unmet medical need. Current approaches to regeneration and tissue engineering of articular cartilage include the use of chondrocytes, stem cells, scaffolds and signals, including morphogens and growth factors. Stem cells, as a source of cells for articular cartilage regeneration, are a critical factor for articular cartilage regeneration. This is because articular cartilage tissue has a low cell turnover and does not heal spontaneously. Adult stem cells have been isolated from various tissues, such as bone marrow, adipose, synovial tissue, muscle and periosteum. Signals of the transforming growth factor beta superfamily play critical roles in chondrogenesis. However, adult stem cells derived from various tissues tend to differ in their chondrogenic potential. Pluripotent stem cells have unlimited proliferative capacity compared to adult stem cells. Chondrogenesis from embryonic stem (ES) cells has been studied for more than a decade. However, establishment of ES cells requires embryos and leads to ethical issues for clinical applications. Induced pluripotent stem (iPS) cells are generated by cellular reprogramming of adult cells by transcription factors. Although iPS cells have chondrogenic potential, optimization, generation and differentiation toward articular chondrocytes are currently under intense investigation.

Skin-derived multipotent stromal cells--an archrival for mesenchymal stem cells

Progenitor stem cells have been identified, isolated and characterized in numerous tissues and organs. However, their therapeutic potential and the use of these stem cells remain elusive except for a few progenitor cells from bone marrow, umbilical cord blood, eyes and dental pulp. The use of bone marrow-derived hematopoietic stem cells (HSC) or mesenchymal stem cells (MSCs) is restricted due to their extreme invasive procedures, low differentiation potential with age and rejection. Thus, we need a clinical grade alternative to progenitor stem cells with a high potential to differentiate, naïve and is relatively easy in in vitro propagation. In this review, we summarize cell populations of adherent and floating spheres derived from different origins of skin, or correctly foreskin, by enzymatic digestion compared with established MSCs. The morphology, phenotype, differentiation capability and immunosuppressive property of the adherent cell populations are comparable with MSCs. Serum-free cultured floating spheres have limited mesodermal but higher neurogenic differentation potential, analogous to neural crest stem cells. Both the populations confirmed their plethora potential in in vitro. Together, it may be noted that the skin-derived adherent cell populations and floating cells can be good alternative sources of progenitor cells especially in cosmetic, plastic and sports regenerative medicine.

Regenerative medicine as applied to general surgery

The present review illustrates the state of the art of regenerative medicine (RM) as applied to surgical diseases and demonstrates that this field has the potential to address some of the unmet needs in surgery. RM is a multidisciplinary field whose purpose is to regenerate in vivo or ex vivo human cells, tissues, or organs to restore or establish normal function through exploitation of the potential to regenerate, which is intrinsic to human cells, tissues, and organs. RM uses cells and/or specially designed biomaterials to reach its goals and RM-based therapies are already in use in several clinical trials in most fields of surgery. The main challenges for investigators are threefold: Creation of an appropriate microenvironment ex vivo that is able to sustain cell physiology and function in order to generate the desired cells or body parts; identification and appropriate manipulation of cells that have the potential to generate parenchymal, stromal and vascular components on demand, both in vivo and ex vivo; and production of smart materials that are able to drive cell fate.

Directed growth and differentiation of stem cells towards neural cell fates using soluble and surface-mediated cues

Stem and progenitor cells are helping researchers understand the complex process of mammalian development and also show great promise in treating diseases that are unresponsive to standard therapies. The potential for embryonic stem cells to differentiate into any cell in the body is their great benefit but avoiding co-culture with animal cells and efficiently narrowing cell fate to a single cell type remains challenging. Adult progenitor cells have a more restricted cell fate, but have the potential for use in autologous cell therapies and avoid the ethical issues surrounding the derivation of embryonic stem cell lines. While progress is encouraging, there is much work to be done in directing cells to specific lineages before stem and progenitor cells can be commonly used in clinical settings. This review discusses current techniques used for investigation of the growth and differentiation of stem and progenitor cells, with a focus on neural cell fates.

Update on rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is a malignant childhood tumor of mesenchymal origin that currently has a greater than 70% overall 5-year survival. Multimodality treatment is determined by risk stratification according to pretreatment stage, postoperative group, histology, and site of the primary tumor. Pretreatment staging is dependent on primary tumor site, size, regional lymph node status, and presence of metastases. Unique to RMS is the concept of postoperative clinical grouping that assesses the completeness of disease resection and takes into account lymph node evaluation. At all tumor sites, the clinical grouping, and therefore completeness of resection, is an independent predictor of outcome. Overall, the prognosis for RMS is dependent on primary tumor site, patient age, completeness of resection, extent of disease, including the presence and number of metastatic sites and histology and biology of the tumor cells. Therefore, the surgeon plays a vital role in RMS by contributing to risk stratification for treatment, local control of the primary tumor, and outcome. The current state-of-the-art treatment is determined by treatment protocols developed by the Soft Tissue Sarcoma Committee of the children's Oncology Group.

Thin-layer hydroxyapatite deposition on a nanofiber surface stimulates mesenchymal stem cell proliferation and their differentiation into osteoblasts

Pulsed laser deposition was proved as a suitable method for hydroxyapatite (HA) coating of coaxial poly-ɛ-caprolactone/polyvinylalcohol (PCL/PVA) nanofibers. The fibrous morphology of PCL/PVA nanofibers was preserved, if the nanofiber scaffold was coated with thin layers of HA (200 nm and 400 nm). Increasing thickness of HA, however, resulted in a gradual loss of fibrous character. In addition, biomechanical properties were improved after HA deposition on PCL/PVA nanofibers as the value of Young's moduli of elasticity significantly increased. Clearly, thin-layer hydroxyapatite deposition on a nanofiber surface stimulated mesenchymal stem cell viability and their differentiation into osteoblasts. The optimal depth of HA was 800 nm.

Effect of serum replacement with plysate on cell growth and metabolismin primary cultures of human skeletal muscle

Cell- and tissue culture methodology form an important base for biological, biochemical and biomedical research. Most cell culture techniques require the use of animal sera for the successful propagation of cells. However, the varying composition between batches has fuelled the need for alternatives. In the case of serum derived from animal foetuses, ethical concerns have also been raised. Here we compare the use of a platelet derived lysate (Plysate), which is currently under development as a serum substitute, in the culturing of primary human muscle cells to foetal bovine serum (FBS). In cells cultured with Plysate, differentiation into myotubes, glucose-uptake, phosphatidylinositol 3-kinase (PI3K) activity and expression and phosphorylation of ERK1/2 MAPK and PKB/Akt was impaired. Thus for primary human skeletal muscle Plysate is a sub-optimal substitute for FBS.

Myoblast models of skeletal muscle hypertrophy and atrophy

PURPOSE OF REVIEW

To highlight recent breakthroughs and controversies in the use of myoblast models to uncover cellular and molecular mechanisms regulating skeletal muscle hypertrophy and atrophy.

RECENT FINDINGS

Myoblast cultures provide key mechanistic models of the signalling and molecular pathways potentially employed by skeletal muscle in-vivo to regulate hypertrophy and atrophy. Recently the controversy as to whether insulin-like growth factor (IGF)-I is important in hypertrophy following mechanical stimuli vs. alternative pathways has been hotly debated and is discussed. The role of myostatin in myoblast models of atrophy and interactions between protein synthetic pathways including Akt/mTOR and the 'atrogenes' are explored.

SUMMARY

Targeted in-vivo experimentation directed by skeletal muscle cell culture and bioengineering (three-dimensional skeletal muscle cell culture models) will provide key biomimetic and mechanistic data regarding hypertrophy and atrophy and thus enable the development of important strategies for tackling muscle wasting associated with ageing and disease processes.

Human skeletal muscle-derived stem cells retain stem cell properties after expansion in myosphere culture

Human skeletal muscle contains an accessible adult stem-cell compartment in which differentiated myofibers are maintained and replaced by a self-renewing stem cell pool. Previously, studies using mouse models have established a critical role for resident stem cells in skeletal muscle, but little is known about this paradigm in human muscle. Here, we report the reproducible isolation of a population of cells from human skeletal muscle that is able to proliferate for extended periods of time as floating clusters of rounded cells, termed "myospheres" or myosphere-derived progenitor cells (MDPCs). The phenotypic characteristics and functional properties of these cells were determined using reverse transcription-polymerase chain reaction (RT-PCR), flow cytometry and immunocytochemistry. Our results showed that these cells are clonogenic, express skeletal progenitor cell markers Pax7, ALDH1, Myod, and Desmin and the stem cell markers Nanog, Sox2, and Oct3/4 significantly elevated over controls. They could be maintained proliferatively active in vitro for more than 20 weeks and passaged at least 18 times, despite an average donor-age of 63 years. Individual clones (4.2%) derived from single cells were successfully expanded showing clonogenic potential and sustained proliferation of a subpopulation in the myospheres. Myosphere-derived cells were capable of spontaneous differentiation into myotubes in differentiation media and into other mesodermal cell lineages in induction media. We demonstrate here that direct culture and expansion of stem cells from human skeletal muscle is straightforward and reproducible with the appropriate technique. These cells may provide a viable resource of adult stem cells for future therapies of disease affecting skeletal muscle or mesenchymal lineage derived cell types.

Stem cells in bone tissue engineering

Bone tissue engineering has been one of the most promising areas of research, providing a potential clinical application to cure bone defects. Recently, various stem cells including embryonic stem cells (ESCs), bone marrow-derived mesenchymal stem cells (BM-MSCs), umbilical cord blood-derived mesenchymal stem cells (UCB-MSCs), adipose tissue-derived stem cells (ADSCs), muscle-derived stem cells (MDSCs) and dental pulp stem cells (DPSCs) have received extensive attention in the field of bone tissue engineering due to their distinct biological capability to differentiate into osteogenic lineages. The application of these stem cells to bone tissue engineering requires inducing in vitro differentiation of these cells into bone forming cells, osteoblasts. For this purpose, efficient in vitro differentiation towards osteogenic lineage requires the development of well-defined and proficient protocols. This would reduce the likelihood of spontaneous differentiation into divergent lineages and increase the available cell source for application to bone tissue engineering therapies. This review provides a critical examination of the various experimental strategies that could be used to direct the differentiation of ESC, BM-MSC, UCB-MSC, ADSC, MDSC and DPSC towards osteogenic lineages and their potential applications in tissue engineering, particularly in the regeneration of bone.

Chondrogenesis of synovium-derived mesenchymal stem cells in gene-transferred co-culture system

A co-culture strategy has been developed in this study wherein rabbit synovial mesenchymal stem cells (SMSCs) are co-cultured with growth factor (GF) transfected articular chondrocytes. Toward this end, both SMSCs and early passage rabbit articular chondrocytes that had been adenovirally transduced with transforming growth factor-beta 3 (TGF-beta3) gene were separately encapsulated in alginate beads and co-cultured in the same pool of chondrogenic medium. The chondrocytes act as transfected companion cells (TCCs) providing GF supply to induce chondrogenic differentiation of SMSCs that play the role of therapeutic progenitor cells (TPCs). Against the same TCC based TGF-beta3 release profile, the co-culture was started at different time points (Day 0, Day 10 and Day 20) but made to last for identical periods of exposure (30 days) so that the exposure conditions could be optimized in terms of initiation and duration. Transfection of TCCs prevents the stem cell based TPCs from undergoing the invasive procedure. It also prevents unpredictable complications in the TPCs caused by long-term constitutive over-expression of a GF. The adenovirally transfected TCCs exhibit a transient GF expression which results in a timely termination of GF supply to the TPCs. The TCC-sourced transgenic TGF-beta3 successfully induced chondrogenesis in the TPCs. Real-time PCR results show enhanced expression of cartilage markers and immuno/histochemical staining for Glycosaminoglycans (GAG) and Collagen II also shows abundant extracellular matrix (ECM) production and chondrogenic morphogenesis in the co-cultured TPCs. These results confirm the efficacy of directing stem cell differentiation towards chondrogenesis and cartilage tissue formation by co-culturing them with GF transfected chondrocytes.

A three-dimensional gel bioreactor for assessment of cardiomyocyte induction in skeletal muscle-derived stem cells

Skeletal muscle-derived stem cells (MDSCs) are able to differentiate into cardiomyocytes (CMs). However, it remains to be investigated whether differentiated CMs contract similar to native CMs. Here, we developed a three-dimensional collagen gel bioreactor (3DGB) that induces a working CM phenotype from MDSCs, and the contractile properties are directly measured as an engineered cardiac tissue. Neonate rat MDSCs were isolated from hind-leg muscles via the preplate technique. Isolated MDSCs were approximately 60% positive to Sca-1 and negative to CD34, CD45, or c-kit antigens. We sorted Sca-1(-) MDSCs and constructed MDSC-3DGBs by mixing MDSCs with acid soluble rat tail collagen type-I and matrix factors. MDSC-3DGB exhibited spontaneous cyclic contraction by culture day 7. MDSC-3DGB expressed cardiac-specific genes and proteins. Histological assessment revealed that cardiac-specific troponin-T and -I expressed in a typical striation pattern and connexin-43 was expressed similar to the native fetal ventricular papillary muscle. beta-Adrenergic stimulation increased MDSC-3DGB spontaneous beat frequency. MDSC-3DGB generated contractile force and intracellular calcium ion transients similar to engineered cardiac tissue from native cardiac cells. Results suggest that MDSC-3DGB induces a working CM phenotype in MDSCs and is a useful 3D culture system to directly assess the contractile properties of differentiated CMs in vitro.

Overexpression of sonic Hedgehog in the lung mimics the effect of lung injury and compensatory lung growth on pulmonary Sca-1 and CD34 positive cells

Cells localized in the bronchioalveolar duct junction of the murine lung have been identified as potential bronchioalveolar stem cells. Based on the surface marker expression, two main phenotypes have been proposed: Sca-1(+), CD34(+), CD45(-), Pecam(-) and Sca-1(low), CD34(-) CD45(-), Pecam(-) cells. An increase in the number of Sca-1(+), CD34(+) CD45(-), Pecam(-) cells and activation of the sonic hedgehog (Shh) pathway was observed following unilateral pneumonectomy and naphthalene-induced airway injury. Overexpression of Shh in the respiratory tract also resulted in an increase of this cell population. Syngeneic transplantation of beta-galactosidase-expressing bone marrow cells demonstrated that the increase of Sca-1(+), CD34(+), CD45(-), Pecam(-) cells in the lung was a result of local proliferation. Intratracheal administration of purified Shh-stimulated Sca-1(+), CD45(-), Pecam(-) cells coexpressing CD34 to syngeneic mice following pneumonectomy resulted in engraftment of these cells predominantly in the airways for up to 3 months, whereas Sca-1(-), CD45(-), Pecam(-) cells did not engraft. This study suggests that local Sca-1(+), CD34(+), CD45(-), Pecam(-) cells are stimulated during compensatory lung growth, following airway injury and overexpression of Shh and have some potential to engraft in the airways, without showing clonal properties in vivo.

New source of muscle-derived stem cells with potential for alveolar bone reconstruction in cleft lip and/or palate patients

Cleft lip and palate (CLP), one of the most frequent congenital malformations, affects the alveolar bone in the great majority of the cases, and the reconstruction of this defect still represents a challenge in the rehabilitation of these patients. One of the current most promising strategy to achieve this goal is the use of bone marrow stem cells (BMSC); however, isolation of BMSC or iliac bone, which is still the mostly used graft in the surgical repair of these patients, confers site morbidity to the donor. Therefore, in order to identify a new alternative source of stem cells with osteogenic potential without conferring morbidity to the donor, we have used orbicular oris muscle (OOM) fragments, which are regularly discarded during surgery repair (cheiloplasty) of CLP patients. We obtained cells from OOM fragments of four unrelated CLP patients (CLPMDSC) using previously described preplating technique. These cells, through flow cytometry analysis, were mainly positively marked for five mesenchymal stem cell antigens (CD29, CD90, CD105, SH3, and SH4), while negative for hematopoietic cell markers, CD14, CD34, CD45, and CD117, and for endothelial cell marker, CD31. After induction under appropriate cell culture conditions, these cells were capable to undergo chondrogenic, adipogenic, osteogenic, and skeletal muscle cell differentiation, as evidenced by immunohistochemistry. We also demonstrated that these cells together with a collagen membrane lead to bone tissue reconstruction in a critical-size cranial defects previously induced in nonimmunocompromised rats. The presence of human DNA in the new bone was confirmed by PCR with human-specific primers and immunohistochemistry with human nuclei antibodies. In conclusion, we showed that cells from OOM have phenotypic and behavior characteristics similar to other adult stem cells, both in vitro and in vivo. Our findings suggest that these cells represent a promising source of stem cells for alveolar bone grafting treatment, particularly in young CLP patients.

Progenitor and stem cells for bone and cartilage regeneration

Research in regenerative medicine is developing at a significantly quick pace. Cell-based bone and cartilage replacement is an evolving therapy aiming at the treatment of patients who suffer from limb amputation, damaged tissues and various bone and cartilage-related disorders. Stem cells are undifferentiated cells with the capability to regenerate into one or more committed cell lineages. Stem cells isolated from multiple sources have been finding widespread use to advance the field of tissue repair. The present review gives a comprehensive overview of the developments in stem cells originating from different tissues and suggests future prospects for functional bone and cartilage tissue regeneration.