Bone and cartilage formation in diffusion chambers by subcultured cells derived from the periosteum

Overview of Periosteal Reaction by Imaging

The periosteum is a membrane that covers almost all bones in the body. It is a living structure but attracts little attention unless it reacts excessively. We highlight the important points in the anatomy, histology, and physiology of the periosteum, the stimuli and various aspects of periosteal reaction, and the main conditions underlying periosteal reaction.

Application of Bone Marrow-Derived Macrophages Combined with Bone Mesenchymal Stem Cells in Dual-Channel Three-Dimensional Bioprinting Scaffolds for Early Immune Regulation and Osteogenic Induction in Rat Calvarial Defects

The host immune response to biomaterials is critical for determining scaffold fate and bone regeneration outcomes. Three-dimensional (3D) bioprinted scaffolds encapsulated with living cells can improve the inflammatory microenvironment and further accelerate bone repair. Here, we screened and adopted 8% methacrylamidated gelatin (GelMA)/1% methacrylamidated hyaluronic acid (HAMA) as the encapsulation system for rat bone marrow-derived macrophages (BMMs) and 3% Alginate/0.5 mg/mL graphene oxide (GO) as the encapsulation system for rat bone mesenchymal stem cells (BMSCs), thus forming a dual-channel bioprinting scaffold. The 8% GelMA/1% HAMA/3% Alginate/0.5 mg/mL GO (8/1/3/0.5) group could form a scaffold with a stable structure, good mechanical properties, and satisfied biocompatibility. When exploring the crosstalk between BMMs and BMSCs in vitro, we found that BMSCs could promote the polarization of BMMs to M2 type at the early stage, reduce the pro-inflammatory gene expression, and increase anti-inflammatory gene expression; conversely, BMMs can promote the osteogenic differentiation of BMSCs. In addition, in the model of rat calvarial defects, the dual-channel scaffold encapsulated with BMMs and BMSCs was more effective than the single-cell scaffold and the acellular scaffold. The paracrine of BMMs and BMSCs in the biodegradable dual-channel scaffold effectively promoted the M2-type polarization of macrophages in the microenvironment of early bone defects, avoided excessive inflammatory responses, and further promoted bone repair. In conclusion, our findings suggested that using 3D bioprinting to simultaneously encapsulate two primary cells of BMMs and BMSCs in a dual-channel system may be an effective way to promote bone repair from the perspective of early immune regulation and late induction of osteogenesis.

Isolation and Culture of Periosteum-Derived Progenitor Cells from Mice

This chapter describes the methods of isolation of mouse periosteal progenitor cells. There are three basic methods utilized. The bone grafting method was developed utilizing the fracture healing process to expand the progenitor populations. Bone capping methods requires enzymatic digestion and purification of cells from the native periosteum, while the Egression/Explant method requires the least manipulation with placement of cortical bone fragments with attached periosteum in a culture dish. Various cell surface antibodies have been employed over the years to characterize periosteum derived progenitor cells, but the most consistent minimal criteria was recommended by the International Society for Cellular Therapy. Confirmation of the multipotent status of these isolated cells can be achieved by differentiation into the three basic mesodermal lineages in vitro.

Monocyte/Macrophage Lineage Cells From Fetal Erythromyeloid Progenitors Orchestrate Bone Remodeling and Repair

A third of the population sustains a bone fracture, and the pace of fracture healing slows with age. The slower pace of repair is responsible for the increased morbidity in older individuals who sustain a fracture. Bone healing progresses through overlapping phases, initiated by cells of the monocyte/macrophage lineage. The repair process ends with remodeling. This last phase is controlled by osteoclasts, which are bone-specific multinucleated cells also of the monocyte/macrophage lineage. The slower rate of healing in aging can be rejuvenated by macrophages from young animals, and secreted proteins from macrophage regulate undifferentiated mesenchymal cells to become bone-forming osteoblasts. Macrophages can derive from fetal erythromyeloid progenitors or from adult hematopoietic progenitors. Recent studies show that fetal erythromyeloid progenitors are responsible for the osteoclasts that form the space in bone for hematopoiesis and the fetal osteoclast precursors reside in the spleen postnatally, traveling through the blood to participate in fracture repair. Differences in secreted proteins between macrophages from old and young animals regulate the efficiency of osteoblast differentiation from undifferentiated mesenchymal precursor cells. Interestingly, during the remodeling phase osteoclasts can form from the fusion between monocyte/macrophage lineage cells from the fetal and postnatal precursor populations. Data from single cell RNA sequencing identifies specific markers for populations derived from the different precursor populations, a finding that can be used in future studies. Here, we review the diversity of macrophages and osteoclasts, and discuss recent finding about their developmental origin and functions, which provides novel insights into their roles in bone homeostasis and repair.

Niches for Skeletal Stem Cells of Mesenchymal Origin

With very few exceptions, all adult tissues in mammals are maintained and can be renewed by stem cells that self-renew and generate the committed progeny required. These functions are regulated by a specific and in many ways unique microenvironment in stem cell niches. In most cases disruption of an adult stem cell niche leads to depletion of stem cells, followed by impairment of the ability of the tissue in question to maintain its functions. The presence of stem cells, often referred to as mesenchymal stem cells (MSCs) or multipotent bone marrow stromal cells (BMSCs), in the adult skeleton has long been realized. In recent years there has been exceptional progress in identifying and characterizing BMSCs in terms of their capacity to generate specific types of skeletal cells in vivo. Such BMSCs are often referred to as skeletal stem cells (SSCs) or skeletal stem and progenitor cells (SSPCs), with the latter term being used throughout this review. SSPCs have been detected in the bone marrow, periosteum, and growth plate and characterized in vivo on the basis of various genetic markers (i.e., Nestin, Leptin receptor, Gremlin1, Cathepsin-K, etc.). However, the niches in which these cells reside have received less attention. Here, we summarize the current scientific literature on stem cell niches for the SSPCs identified so far and discuss potential factors and environmental cues of importance in these niches in vivo. In this context we focus on (i) articular cartilage, (ii) growth plate cartilage, (iii) periosteum, (iv) the adult endosteal compartment, and (v) the developing endosteal compartment, in that order.

Jaw Periosteal Cells Seeded in Beta-Tricalcium Phosphate Inhibit Dendritic Cell Maturation

Mesenchymal stem cells (MSCs) have gained attraction not only in the field of regenerative medicine but also in the field of autoimmune disease therapies or organ transplantation due to their immunoregulatory and/or immunosuppressive features. Dendritic cells (DCs) play a crucial role in initiating and regulating immune reactions by promoting antigen-specific T cell activation. In this study, we investigated the effect of human jaw periosteal progenitor cells (JPCs) seeded in beta-tricalcium phosphate (β-TCP) scaffolds on monocyte-derived DC differentiation. Significantly lower numbers of differentiated DCs were observed in the presence of normal (Co) and osteogenically induced (Ob) JPCs-seeded β-TCP constructs. Gene expression analysis revealed significantly lower interleukin-12 subunit p35 (IL-12p35) and interleukin-12 receptor beta 2 (IL-12Rβ2) and pro-inflammatory cytokine interferon-gamma (IFN-γ) levels in DCs under Ob conditions, while interleukin-8 (IL-8) gene levels were significantly increased. Furthermore, in the presence of JPCs-seeded β-TCP constructs, interleukin-10 (IL-10) gene expression was significantly induced in DCs, particularly under Ob conditions. Analysis of DC protein levels shows that granulocyte-colony stimulating factor (G-CSF) was significantly upregulated in coculture groups. Our results indicate that undifferentiated and osteogenically induced JPCs-seeded β-TCP constructs have an overall inhibitory effect on monocyte-derived DC maturation.

Bone augmentation by octacalcium phosphate and collagen composite coated with poly-lactic acid cage

Objective

Although octacalcium phosphate and collagen composite (OCP/Col) has demonstrated excellent bone regeneration, it has never achieved bone augmentation. The present study investigated whether it could be enabled by OCP/Col disks treated with parathyroid hormone (PTH) and covered with a poly‐lactic acid (PLA) cage.

Materials and methods

The prepared OCP/Col disks with three different types of PLA cages (no hole, one large hole, several small holes) were implanted into subperiosteal pockets in rodent calvaria. Histological, and histomorphometric analyses were conducted at 12 weeks after implantation.

Results

Implants with all PLA cage variants achieved sufficient bone augmentation, and analyses showed that new bone was formed from the original bone and along the PLA cage. While the PLA cage variant with no holes sporadically evoked new bone formation even at the central area of the roof of the PLA cage, the PLA cage variants with holes had no new bone in the area of the hole or beneath the periosteum.

Conclusions

These results suggest that sufficient bone augmentation could be achieved by treating the OCP/Col disks with PTH and covering them with a PLA cage, and periosteum might not have been involved in the bone formation in this experiment.

Human adipose-derived stem cells support lymphangiogenesis in vitro by secretion of lymphangiogenic factors

Lymphedema is a chronic progressive disease ultimately resulting in severe, disfiguring swelling and permanent changes of the affected tissues. Presently, there is no causal treatment approach of lymphedema. Therefore, most therapies are purely symptomatic. However, the recent use of stem cell-based therapies has offered new prospects for alternative treatment options. The present study was performed to investigate the effects of human adipose-derived stem cells (ADSCs) on human dermal lymphatic endothelial cells (HDLECs) in terms of basic in vitro lymphangiogenic assays (WST-8 assay, scratch assay, transmigration assay, sprouting assay, tube formation assay). The influence of ADSC-conditioned medium (ADSC-CM) on HDLECs was compared to recombinant VEGF-C, bFGF and HGF. Further ADSC-CM was characterized by protein microarray and enzyme-linked immunosorbent assay (ELISA). Although key-lymphangiogenic growth factors - like VEGF-C - could only be detected in low concentrations within the conditioned medium (CM), HDLECs were potently stimulated to proliferate, migrate and to form tube like structures by ADSC-CM. Despite concentrations more than hundredfold higher than those found in the conditioned medium, stimulation with recombinant VEGF-C, bFGF and HGF was still weaker compared to ADSC-CM. These results highlight the effectiveness of growth factors secreted by ADSC to stimulate HDLEC, potentially providing a promising new therapeutic approach for the treatment of lymphedema.

Effect of let-7a overexpression on the differentiation of conjunctiva mesenchymal stem cells into photoreceptor-like cells

Objective(s):

MicroRNAs (miRNAs) could regulate many cellular processes such as proliferation and differentiation. let-7a miRNA is one of the key regulators in the developmental transition of retinal progenitor cells into differentiated cells. Current evidence suggests that mesenchymal stem cells (MSCs) can isolate from various tissues such as bone marrow and conjunctiva. In this study, we investigated the effect of let-7a overexpression on induced differentiation of conjunctiva mesenchymal stem cells (CJMSCs) into photoreceptor-like cells.

Materials and Methods:

After isolation and characterization, CJMSCs were transduced with lentiviruses containing let-7a or empty vector. The effect of let-7a overexpression on expression of photoreceptor-specific markers was evaluated by quantitative real-time PCR (RT-qPCR) after 28 and 42 days of transduction.

Results:

The relative expression of rhodopsin and recoverin genes was evaluated by RT-qPCR in let-7a overexpressing cells, control vector transduced cells and untransduced CJMSCs (control cells). Our results indicated that following overexpression of let-7a, after 28 and 42 days of transduction, significant up-regulation in the expression of recoverin (574.7 and 43.9 folds) and rhodopsin (3334.7 and 53.1 folds) were observed, respectively.

Conclusion:

Our findings indicate that overexpression of let-7a microRNA can increase the expression of photoreceptor-specific genes in CJMSCs. Moreover, it is prospective that let-7a overexpression can use as an alternative protocol for the differentiation of mesenchymal stem cells into photoreceptors. It seems that the effect of let-7a on the differentiation of CJMSCs into photoreceptors is also time-dependent.

Periosteal Osteogenic Capacity Depends on Tissue Source

Periosteal osteogenic capacity can be exploited to enhance bone formation in the fields of tissue engineering and regenerative medicine. Despite this importance, there have been no studies examining the composition, structure, and osteogenic capacity of periostea from different bone sources. In this study, structure and osteogenic factor content were compared among periostea from rib, calvarial, femoral, and tibial bones, in which the native bones of these four regions were harvested and subjected to histological analysis. The osteogenic capacity of grafted periosteum was evaluated using an in vivo vascularized pedicle model of bone tissue engineering. Poly(ethylene glycol)-poly(l-lactic acid) (PEG-PLLA) copolymer hydrogels were seeded with bone marrow mesenchymal stem cells and implanted with grafted periosteum harvested from either calvarial or tibial bone, which were representative of thin and thick native periostea, respectively. The cambium layer thickness of periostea from the femoral and tibial bones (36.9% ± 2.5% and 36.8% ± 2.6%) was greater than that from the calvarial and rib bones (26.8% ± 2.4% and 25.5% ± 1.9%). The osteocalcin and alkaline phosphatase levels were comparatively higher in the femoral and tibial periostea than those in periostea harvested from the calvarial and rib bones. The construct implanted with grafted tibial periosteum resulted in greater neo-bone regeneration and higher osteocalcin and alkaline phosphatase expression. This study is the first investigation of the osteogenic capacity of periostea from diverse sources. The results can be used to guide clinical strategies that exploit periostea for tissue engineering and clinical applications.

Primary cilia are necessary for Prx1-expressing cells to contribute to postnatal skeletogenesis

Although Prx1 (also known as PRRX1)-expressing cells and their primary cilia are critical for embryonic development, they have yet to be studied in the context of postnatal skeletogenesis owing to the lethality of mouse models. A tamoxifen-inducible Prx1 model has been developed, and we determined that expression directed by this promoter is highly restricted to the cambium layers in the periosteum and perichondrium after birth. To determine the postnatal role of these cambium layer osteochondroprogenitors (CLOPs) and their primary cilia, we developed models to track the fate of CLOPs (Prx1CreER-GFP;Rosa26tdTomato) and selectively disrupt their cilia (Prx1CreER-GFP;Ift88fl/fl). Our tracking studies revealed that CLOPs populate cortical and trabecular bone, the growth plate and secondary ossification centers during the normal program of postnatal skeletogenesis. Furthermore, animals lacking CLOP cilia exhibit stunted limb growth due to disruptions in endochondral and intramembranous ossification. Histological examination indicates that growth is stunted due to limited differentiation, proliferation and/or abnormal hypertrophic differentiation in the growth plate. Collectively, our results suggest that CLOPs are programmed to rapidly populate distant tissues and produce bone via a primary cilium-mediated mechanism in the postnatal skeleton.

Delivery of cellular factors to regulate bone healing

Bone tissue has a strong intrinsic regenerative capacity, thanks to a delicate and complex interplay of cellular and molecular processes, which tightly involve the immune system. Pathological settings of anatomical, biomechanical or inflammatory nature may lead to impaired bone healing. Innovative strategies to enhance bone repair, including the delivery of osteoprogenitor cells or of potent cytokines/morphogens, indicate the potential of 'orthobiologics', but are not fully satisfactory. Here, we review different approaches based on the delivery of regenerative cues produced by cells but in cell-free, possibly off-the-shelf configurations. Such strategies exploit the paracrine effect of the secretome of mesenchymal stem/stromal cells, presented in soluble form, shuttled through extracellular vesicles, or embedded within the network of extracellular matrix molecules. In addition to osteoinductive molecules, attention is given to factors targeting the resident immune cells, to reshape inflammatory and immunity processes from scarring to regenerative patterns.

Culture Expanded Canine Mesenchymal Stem Cells Possess Osteochondrogenic Potential in Vivo and in Vitro

Mesenchymal Stem Cells (MSCs) possessing the capacity to differentiate into various cell types such as osteoblasts, chondrocytes, myoblasts, and adipocytes have been previously isolated from the marrow and periosteum of human, murine, lapine, and avian species. This study documents the existence of similar multipotential stem cells in canine marrow. The cells were isolated from marrow aspirates using a modification of techniques previously established for human MSCs (hMSCs), and found to possess similar growth and morphological characteristics, as well as osteochondrogenic potential in vivo and in vitro. On the basis of these results, the multipotential cells that were isolated and culture expanded are considered to be canine MSCs (cMSCs). The occurrence of cMSCs in the marrow was determined to be one per 2.5 × 104 nucleated cells. After enrichment of the cMSCs by centrifugation on a Per-coll cushion, the cells were cultivated in selected lots of serum. Like the hMSCs, cMSCs grew as colonies in primary culture and on replating, grew as a monolayer culture with very uniform spindle morphology. The population doubling time for these cMSCs was approximately 2 days. The morphology and the growth kinetics of the cMSCs were retained following repeated passaging. The osteogenic phenotype could be induced in the cMSC cultures by the addition of a synthetic glucocorticoid, dexamethasone. In these osteogenic cultures, alkaline phosphatase activity was elevated up to 10-fold, and mineralized matrix production was evident. When cMSCs were loaded onto porous ceramics and implanted in autologous canine or athymic murine hosts, copious amounts of bone and cartilage were formed in the pores of the implants. The MSC-mediated osteogenesis obtained by the implantation of the various MSC-loaded matrix combinations is the first evidence of osteogenesis in a canine model by implantation of culture expanded autologous stem cells. The identification and isolation of cMSCs now makes it feasible to pursue preclinical models of bone and cartilage regeneration in canine hosts.

Conventional Versus Computer-Assisted Corrective Osteotomy of the Forearm: a Retrospective Analysis of 56 Consecutive Cases

PURPOSE

Accuracy and feasibility of corrective osteotomies using 3-dimensional planning tools and patient-specific instrumentation has been reported by multiple authors with promising results. However, studies describing clinical outcomes following these procedures are rare. Therefore, the purpose of this study was to compare the results of computer-assisted corrective osteotomies of the diaphyseal and distal radius with a conventional non-computer-assisted technique regarding duration of surgery, consolidation of the osteotomy, and complications. Also, subjective and objective clinical outcome parameters were assessed.

METHODS

We retrospectively compared the results of 31 patients who underwent a corrective osteotomy performed conventionally with 25 patients treated with a computer-assisted method (CA) using patient-specific instrumentation. Baseline data were similar among both groups. The duration of surgery, bony consolidation, complications, gain in range of motion, and subjective outcome were recorded.

RESULTS

The mean operating time was significantly shorter in the CA group compared with the conventional group. After 12 weeks, significantly more osteotomies were considered healed in the CA group compared with the conventional group. Two patients in the CA group required revision surgery to treat nonunion of the osteotomy. Otherwise clinical results were similar among both groups.

CONCLUSIONS

The results demonstrate that the computer-assisted method facilitates shorter operation times while providing similar clinical results.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Intra-articular Implantation of Mesenchymal Stem Cells, Part 1: A Review of the Literature for Prevention of Postmeniscectomy Osteoarthritis

Osteoarthritis (OA) after a partial or total meniscectomy procedure is a common pathology. Because of the high incidence of meniscectomy in the general population, as well as the significant burden of knee OA, there is increasing interest in determining methods for delaying postmeniscectomy OA. Biological therapies, including mesenchymal stem cells (MSCs), induced pluripotent stem cells (iPSCs), and platelet-rich plasma (PRP), have been proposed as possible therapies that could delay OA in this and other settings. Several studies in various animal models have evaluated the effect of injecting MSCs into the knee joints of animals with OA induced either by meniscal excision with or without anterior cruciate ligament transection. When compared with control groups receiving injections without progenitor cells, short-term benefits in the experimental groups have been reported. In human subjects, there are limited data to determine the effect of biological therapies for use in delaying or preventing the onset of OA after a meniscectomy procedure. The purpose of this review is to highlight the findings in the presently available literature on the use of intra-articular implantation of MSCs postmeniscectomy and to offer suggestions for future research with the goal of delaying or treating early OA postmeniscectomy with MSCs.

Strategies and First Advances in the Development of Prevascularized Bone Implants

Despite the great regenerative potential of human bone, large bone defects are a serious condition. Commonly, large defects are caused by trauma, bone disease, malignant tumor removal, and infection or medication-related osteonecrosis. Large defects necessitate clinical treatment in the form of autologous bone transplantation or implantation of biomaterials as well as the application of other available methods that enhance bone defect repair. The development and application of prevascularized bone implants are closely related to the development animal models and require dedicated methods in order to reliably predict possible clinical outcomes and the efficacy of implants. Cell sheet engineering, 3D-printing, arteriovenous loops, and naturally derived decellularized scaffolds and their respective testings in animal models are presented as alternative to the autologous bone graft in this article.

Amniotic Mesenchymal Stem Cells Can Enhance Angiogenic Capacity via MMPs In Vitro and In Vivo

The aim of this study was to evaluate the angiogenic capacity and proteolytic mechanism of coculture using human amniotic mesenchymal stem cells (hAMSCs) with human umbilical vein endothelial cells (HUVECs) in vivo and in vitro by comparing to those of coculture using bone marrow mesenchymal stem cells with HUVEC. For the in vivo experiment, cells (HUVEC-monoculture, HUVEC-hAMSC coculture, and HUVEC-BMMSC coculture) were seeded in fibrin gels and injected subcutaneously in nude mice. The samples were collected on days 7 and 14 and histologically analyzed by H&E and CD31 staining. CD31-positive staining percentage and vessel-like structure (VLS) density were evaluated as quantitative parameters for angiogenesis. The increases of CD31-positive staining area and VLS density in both HUVEC-hAMSC group and HUVEC-BMMSC group were found between two time points, while obvious decline of those was observed in HUVEC-only group. For the in vitro experiment, we utilized the same 3D culture model to investigate the proteolytic mechanism related to capillary formation. Intensive vascular networks formed by HUVECs were associated with hAMSCs or BMMSCs and related to MMP2 and MMP9. In conclusion, hAMSCs shared similar capacity and proteolytic mechanism with BMMSCs on neovascularization.

Current Perspectives in Mesenchymal Stromal Cell Therapies for Airway Tissue Defects

Lung cancer is the leading cause of cancer death and respiratory diseases are the third cause of death in industrialized countries; for this reason the airways and cardiopulmonary system have been the focus of extensive investigation, in particular of the new emerging branch of regenerative medicine. Mesenchymal stromal cells (MSCs) are a population of undifferentiated multipotent adult cells that naturally reside within the human body, which can differentiate into osteogenic, chondrogenic, and adipogenic lineages when cultured in specific inducing media. MSCs have the ability to migrate and engraft at sites of inflammation and injury in response to cytokines, chemokines, and growth factors at a wound site and they can exert local reparative effects through transdifferentiation and differentiation into specific cell types or via the paracrine secretion of soluble factors with anti-inflammatory and wound-healing activities. Experimental and clinical evidence exists regarding MSCs efficacy in airway defects restoration; although clinical MSCs use, in the daily practice, is not yet completely reached for airway diseases, we can argue that MSCs do not represent any more merely an experimental approach to airway tissue defects restoration but they can be considered as a “salvage” therapeutic tool in very selected patients and diseases.

Periosteum derived stem cells for regenerative medicine proposals: Boosting current knowledge

Periosteum is a thin fibrous layer that covers most bones. It resides in a dynamic mechanically loaded environment and provides a niche for pluripotent cells and a source for molecular factors that modulate cell behaviour. Elucidating periosteum regenerative potential has become a hot topic in orthopaedics. This review discusses the state of the art of osteochondral tissue engineering rested on periosteum derived progenitor cells (PDPCs) and suggests upcoming research directions. Periosteal cells isolation, characterization and migration in the site of injury, as well as their differentiation, are analysed. Moreover, the role of cell mechanosensing and its contribution to matrix organization, bone microarchitecture and bone stenght is examined. In this regard the role of periostin and its upregulation under mechanical stress in order to preserve PDPC survival and bone tissue integrity is contemplated. The review also summarized the role of the periosteum in the field of dentistry and maxillofacial reconstruction. The involvement of microRNAs in osteoblast differentiation and in endogenous tissue repair is explored as well. Finally the novel concept of a guided bone regeneration based on the use of periosteum itself as a smart material and the realization of constructs able to mimic the extracellular matrix features is talked out. Additionally, since periosteum can differentiate into insulin producing cells it could be a suitable source in allogenic transplantations. That innovative applications would take advantage from investigations aimed to assess PDPC immune privilege.

Isolation and characterization of mesenchymal stem cells

Mesenchymal stem cells (MSCs) have drawn great interest in the field of regenerative medicine, for cell replacement, immunomodulatory, and gene therapies. It has been shown that these multipotent stromal cells can be isolated from tissues such as bone marrow, adipose tissue, trimester amniotic tissue, umbilical cord blood, and deciduous teeth and can be expanded in adherent culture. They have the capacity to differentiate into cells of the connective tissue lineages in vitro and contribute to tissue parenchyma in vivo. However, proper in vitro manipulation of MSCs is a key issue to reveal a potential therapeutic benefit following transplantation into the patients. This chapter summarizes some of the essential protocols and assays used at our laboratory for the isolation, culture, differentiation, and characterization of mesenchymal stem cells from the bone marrow and adipose tissue.

Immunomodulatory nature and site specific affinity of mesenchymal stem cells: a hope in cell therapy

Immunosuppressive ability of mesenchymal stem cells (MSCs), their differentiation properties to various specialized tissue types, ease of in vitro and in vivo expansion and specific migration capacity, make them to be tested in different clinical trials for the treatment of various diseases. The immunomodulatory effects of MSCs are less identified which probably has high clinically significance. The clinical trials based on primary research will cause better understanding the ability of MSCs in immunomodulatory applications and site specific migration in the optimization of therapy. So, this review focus on MSCs functional role in modulating immune responses, their ability in homing to tumor, their potency as delivery vehicle and their medical importance.

The role of bone marrow-derived cells during the bone healing process in the GFP mouse bone marrow transplantation model

Bone healing is a complex and multistep process in which the origin of the cells participating in bone repair is still unknown. The involvement of bone marrow-derived cells in tissue repair has been the subject of recent studies. In the present study, bone marrow-derived cells in bone healing were traced using the GFP bone marrow transplantation model. Bone marrow cells from C57BL/6-Tg (CAG-EGFP) were transplanted into C57BL/6 J wild mice. After transplantation, bone injury was created using a 1.0-mm drill. Bone healing was histologically assessed at 3, 7, 14, and 28 postoperative days. Immunohistochemistry for GFP; double-fluorescent immunohistochemistry for GFP-F4/80, GFP-CD34, and GFP-osteocalcin; and double-staining for GFP and tartrate-resistant acid phosphatase were performed. Bone marrow transplantation successfully replaced the hematopoietic cells into GFP-positive donor cells. Immunohistochemical analyses revealed that osteoblasts or osteocytes in the repair stage were GFP-negative, whereas osteoclasts in the repair and remodeling stages and hematopoietic cells were GFP-positive. The results indicated that bone marrow-derived cells might not differentiate into osteoblasts. The role of bone marrow-derived cells might be limited to adjustment of the microenvironment by differentiating into inflammatory cells, osteoclasts, or endothelial cells in immature blood vessels.

Human periosteum-derived stem cells for tissue engineering applications: the role of VEGF

Mesenchymal stem cells (MSCs) are promising tools for studying the mechanisms of development and for the regeneration of injured tissues. Correct selection of the MSCs source is crucial in order to obtain a more efficient treatment and, in this respect Periosteum-Derived Cells (PDPCs) may represent an interesting alternative to bone marrow MSCs for osteochondral tissue regeneration. In the present study we have isolated and characterized a MSCs population from the periosteum of human adult donors. PDPCs were expanded under specific culture conditions that prevent fibroblast contamination and support the maintenance of their undifferentiated phenotype. We show, for the first time, that PDPCs expresses VEGF receptor (Flt1 and KDR/Flk1) proteins and that they were similar to bone marrow Multipotent Adult Progenitor Cells (MAPCs). Since the latter are able to differentiate into endothelial cells, we tested the possible PDPCs commitment toward an endothelial phenotype in view of bone tissue engineering approaches that takes into account not only bone formation but also vascularization. PDPCs were treated with two different VEGF concentrations for 7 and 15 days and, alternatively, with the supernatant of human primary osteoblasts. Differently from MAPCs our PDPCs were unable to differentiate into endothelial cells after their in vitro VEGF treatment. On the contrary, growth factor stimulation induces PDPCs differentiation toward osteoblasts. We concluded that in PDPCs the presence of VEGF receptors is related to different cross-talk between osteogenesis and angiogenesis that could involve in situ PDPCs recruitment.

Biological apatite (BAp) crystallographic orientation and texture as a new index for assessing the microstructure and function of bone regenerated by tissue engineering

Recently, there have been remarkable advances in medical techniques for regenerating bone defects. To determine the degree of bone regeneration, it is essential to develop a new method that can analyze microstructure and related mechanical function. Here, quantitative analysis of the orientation distribution of biological apatite (BAp) crystallites by a microbeam X-ray diffractometer system is proposed as a new index of bone quality for the evaluation of regenerated bone microstructure. Preferential alignment of the BAp c-axis in the rabbit ulna and skull bone, regenerated by controlled release of basic fibroblast growth factor (bFGF) was investigated. The BAp c-axis orientation was evaluated by the relative intensity between the (002) and (310) diffraction peaks, or the three-dimensional texture for the (002) peak. It was found that new bone in the defects was initially produced without preferential alignment of the BAp c-axis, and subsequently reproduced to recover towards the original alignment. In other words, the BAp density recovered prior to the BAp orientation. Perfect recovery of BAp alignment was not achieved in the ulna and skull defects after 4 weeks and 12 weeks, respectively. Apparent recovery of the macroscopic shape and bio-mineralization of BAp was almost complete in the ulna defect after 4 weeks. However, an additional 2 weeks was required for complete repair of BAp orientation. It is finally concluded that orientation distribution of BAp crystallites offers an effective means of evaluating the degree of microstructural regeneration, and also the related mechanical function, in regenerated hard tissues.

Fracture healing under healthy and inflammatory conditions

Optimal fracture treatment requires knowledge of the complex physiological process of bone healing. The course of bone healing is mainly influenced by fracture fixation stability (biomechanics) and the blood supply to the healing site (revascularization after trauma). The repair process proceeds via a characteristic sequence of events, described as the inflammatory, repair and remodeling phases. An inflammatory reaction involving immune cells and molecular factors is activated immediately in response to tissue damage and is thought to initiate the repair cascade. Immune cells also have a major role in the repair phase, exhibiting important crosstalk with bone cells. After bony bridging of the fragments, a slow remodeling process eventually leads to the reconstitution of the original bone structure. Systemic inflammation, as observed in patients with rheumatoid arthritis, diabetes mellitus, multiple trauma or sepsis, can increase fracture healing time and the rate of complications, including non-unions. In addition, evidence suggests that insufficient biomechanical conditions within the fracture zone can influence early local inflammation and impair bone healing. In this Review, we discuss the main factors that influence fracture healing, with particular emphasis on the role of inflammation.

ECM remodelling components regulated during jaw periosteal cell osteogenesis

Human JPCs (jaw periosteal cells) are a promising source for the engineering of cell-based osteoinductive grafts in oral surgery. For this purpose, cell characteristics of this stem cell source should be elucidated in detail. Analysis of gene expression profiles may help us to evaluate key factors and cellular targets of JPC osteogenesis. Because little is known about the interplay of osteogenic-related components, we analysed the expression of different collagen types reflecting important players for extracellular matrix assembly and of TIMPs (tissue inhibitors of metalloproteinases) responsible for the inhibition of matrix degradation. Gene expression analyses using microarrays and quantitative RT-PCR (reverse transcription-PCR) during JPC osteogenesis revealed the induction of several collagen types' expression (VII, VIII, XI and XII), and some of them (types I, VIII and XI) seemed to be susceptible to BMP-2 (bone morphogenetic protein-2) that is known to be a potent osteogenic inducer of periosteal cells. Among the TIMPs, only TIMP-4 and RECK (reversion-inducing cysteine-rich protein with Kazal motifs) expressions were strongly up-regulated during JPC osteogenesis. Proteome profiler analysis of supernatants from untreated and differentiated JPCs confirmed the gene expression data in terms of TIMP expression. In summary, we identified new collagen types and TIMPs that seem to play important roles during the osteogenesis of jaw periosteal progenitor cells.

Potential of mesenchymal stem cell applications in plastic and reconstructive surgery

: Novel therapy with mesenchymal stem cells from bone marrow, adipose tissue, or other sources has raised high hopes for treatment of a variety of diseases. For plastic and reconstructive surgery, first pilot studies and clinical trials using stem cells for treatment of chronic wounds, radiation injury, or soft tissue augmentation have furnished encouraging results compared with the limitations of standard therapy, for example autologous fat grafting. Further research must be conducted to reveal the complex physiological interactions between activated stem cells and the host environment. Long-term effects and safety aspects of these novel treatment options also require randomized controlled studies. For future clinical applications, guidelines and standardized procedures for stem cell isolation and preparation, and techniques for application must be established.

Periosteum: a highly underrated tool in dentistry

The ultimate goal of any dental treatment is the regeneration of lost tissues and alveolar bone. Under the appropriate culture conditions, periosteal cells secrete extracellular matrix and form a membranous structure. The periosteum can be easily harvested from the patient's own oral cavity, where the resulting donor site wound is invisible. Owing to the above reasons, the periosteum offers a rich cell source for bone tissue engineering; hence, the regenerative potential of periosteum is immense. Although the use of periosteum as a regenerative tool has been extensive in general medical field, the regenerative potential of periosteum is highly underestimated in dentistry; therefore, the present paper reviews the current literature related to the regenerative potential of periosteum and gives an insight to the future use of periosteum in dentistry.

Stem cell use in musculoskeletal disorders

Human stem cells derived from bone marrow are currently used in clinical medicine for bone and cartilage repair for injuries such as meniscal tears. New clinical stem cell studies underway include the treatment of patients with spinal cord injuries. Rapid advances in stem cell science are opening new avenues for drug discovery and may lead to new uses of stem cells for other musculoskeletal disorders.

Mesenchymal stem cells and bone regeneration: current status

The enhancement of bone regeneration with biological agents including osteogenic growth factors and mesenchymal stem cells (MSCs) is becoming a clinical reality. Many exciting findings have been obtained following MSC implantation in animal models, and the data demonstrating their clinical efficacy in humans are promising. The overwhelming majority of experimental work has been performed with MSCs "amplified"in vitro. The nature of native MSCs in skeletal tissues however, remains poorly understood. This review summarizes recent findings pertaining to the definition and characterisation of MSCs in skeletal tissues and discusses the mechanisms of their actions in regenerating of bone in vivo. In respect to traditional tissue engineering paradigm, we bring together literature showing that the ways MSCs are extracted, expanded and implanted can considerably affect bone formation outcomes. Additionally, we discuss current animal models used in MSC research and highlight recent experiments showing important contribution of the host, and not only donor MSCs, in bone tissue formation. This knowledge provides a platform for novel therapy development for bone regeneration based on pharmacologically manipulated endogenous MSCs.

Human amniotic membrane as an alternative source of stem cells for regenerative medicine

The human amniotic membrane (HAM) is a highly abundant and readily available tissue. This amniotic tissue has considerable advantageous characteristics to be considered as an attractive material in the field of regenerative medicine. It has low immunogenicity, anti-inflammatory properties and their cells can be isolated without the sacrifice of human embryos. Since it is discarded post-partum it may be useful for regenerative medicine and cell therapy. Amniotic membranes have already been used extensively as biologic dressings in ophthalmic, abdominal and plastic surgery. HAM contains two cell types, from different embryological origins, which display some characteristic properties of stem cells. Human amnion epithelial cells (hAECs) are derived from the embryonic ectoderm, while human amnion mesenchymal stromal cells (hAMSCs) are derived from the embryonic mesoderm. Both populations have similar immunophenotype and multipotential for in vitro differentiation into the major mesodermal lineages, however they differ in cell yield. Therefore, HAM has been proposed as a good candidate to be used in cell therapy or regenerative medicine to treat damaged or diseased tissues.

MSCA-1/TNAP selection of human jaw periosteal cells improves their mineralization capacity

Human jaw periosteum-derived cells (JPCs) represent an alternative cell source to bone marrow-derived mesenchymal stem cells for tissue engineering applications in the oral and maxillofacial surgery. In this study we investigated how far the presence or expression of human mesenchymal stem cell antigen-1/tissue non-specific alkaline phosphatase (MSCA-1/TNAP) and LNGFR (CD271) can be utilized to select and enrich the osteogenic progenitor cell fraction from the entire JPC population. Depending on their mineralization capacity, we classified the human isolated JPCs into mineralizing (mJPCs) and non-mineralizing JPCs (nmJPCs). Flow cytometric analyses revealed that undifferentiated mJPCs expressed MSCA-1/TNAP at significant higher levels than nmJPCs at day 5 and 10 of osteogenesis. Western blot analyses showed increased MSCA-1/TNAP expression levels in mJPCs during osteogenesis, whereas in nmJPCs MSCA-1/TNAP expression remained undetectable. Using the MSCA-1 and LNGFR specific antibodies, we separated the positive and negative fractions from the entire mJPC population. In order to analyse the mineralization capacity of the MSCA-1(+) and LNGFR(+) cell subsets, we quantified the calcium deposition in both subpopulations in comparison to the respective negative subpopulations. The MSCA-1(+)/TNAP(+) cell fraction showed a significant higher osteogenic capacity compared to the MSCA-1-/TNAP- cell fraction whereas the LNGFR(+/-) cell fractions did not differ in their osteogenic potential. Our findings suggest that MSCA-1 may represent a promising osteogenic marker for mJPC.

A multipotent neural crest-derived progenitor cell population is resident within the oral mucosa lamina propria

Wounds within the oral mucosa, similarly to fetal wounds, exhibit rapid healing with reduced scarring. We hypothesized that a progenitor population resident within the oral mucosal lamina propria (OMLP) contributes to this preferential healing. Progenitor cells (PC) were reliably isolated from the OMLP by differential adhesion to fibronectin. Isolated colonies originating from a single cell demonstrated a rapid initial phase of proliferation, completing in excess of 50 population doublings (PDs) before entering cellular senescence. These data were supported by the expression of active telomerase within both developing colonies and expanded clones as assessed by immunocytochemistry (ICC) and the quantitative telomeric repeat amplification protocol. FACS analysis confirmed expression of the stem cell markers CD44, CD90, CD105, and CD166, but negative expression of CD34 and CD45 ruling out a hematopoietic or fibrocyte origin for these progenitors. A neural crest origin was confirmed by increased colony-forming efficiency (CFE) in the presence of Jagged 1 and the expression of a number of neural crest markers within the developing colonies by ICC and serially passaged clones by Western blotting. The multipotency of this novel PC population was demonstrated by differentiation of the cells down both mesenchymal (chondrogenic, osteoblastic, and adipogenic) and neuronal (neuron and Schwann-like cells) cell lineages. This article reports for the first time, the isolation and characterization of a novel, clonally derived PC population resident within the OMLP. The attributes of this adult stem cell (ASC) population and its accessibility lends itself to future therapeutic applications.

Chemokines in mesenchymal stem cell therapy for bone repair: a novel concept of recruiting mesenchymal stem cells and the possible cell sources

Skeletal injury is one of the most prevalent clinical problems that jeopardize the activities of daily life, especially in our aging society. Mesenchymal stem cells (MSCs) play pivotal roles in regenerating bones after bone injury. MSCs come from the surrounding tissues and/or circulation. Cell sources may be the bone marrow, periosteum, vessel walls, muscle, circulation, and elsewhere, and the migration of MSCs is necessary for bone healing. The mechanism(s) of recruitment and crucial molecules for cell migration are still unclear, but chemokines and their receptors seem to play critical roles. The induction of MSC recruitment from surrounding tissues or from the circulation can be a helpful modality to induce or to support cell-based therapy for bone regeneration.

2010 Nicolas Andry Award: Multipotent adult stem cells from adipose tissue for musculoskeletal tissue engineering

BACKGROUND

Cell-based therapies such as tissue engineering provide promising therapeutic possibilities to enhance the repair or regeneration of damaged or diseased tissues but are dependent on the availability and controlled manipulation of appropriate cell sources.

QUESTIONS/PURPOSES

The goal of this study was to test the hypothesis that adult subcutaneous fat contains stem cells with multilineage potential and to determine the influence of specific soluble mediators and biomaterial scaffolds on their differentiation into musculoskeletal phenotypes.

METHODS

We reviewed recent studies showing the stem-like characteristics and multipotency of adipose-derived stem cells (ASCs), and their potential application in cell-based therapies in orthopaedics.

RESULTS

Under controlled conditions, ASCs show phenotypic characteristics of various cell types, including chondrocytes, osteoblasts, adipocytes, neuronal cells, or muscle cells. In particular, the chondrogenic differentiation of ASCs can be induced by low oxygen tension, growth factors such as bone morphogenetic protein-6 (BMP-6), or biomaterial scaffolds consisting of native tissue matrices derived from cartilage. Finally, focus is given to the development of a functional biomaterial scaffold that can provide ASC-based constructs with mechanical properties similar to native cartilage.

CONCLUSIONS

Adipose tissue contains an abundant source of multipotent progenitor cells. These cells show cell surface marker profiles and differentiation characteristics that are similar to but distinct from other adult stem cells, such as bone marrow mesenchymal stem cells (MSCs).

CLINICAL RELEVANCE

The availability of an easily accessible and reproducible cell source may greatly facilitate the development of new cell-based therapies for regenerative medicine applications in the musculoskeletal system.

Tissue engineering of cartilage using poly-epsilon-caprolactone nanofiber scaffolds seeded in vivo with periosteal cells

OBJECTIVE

To determine the potential of periosteal cells to infiltrate poly-epsilon-caprolactone (PCL) nanofiber scaffolds in vivo and subsequently produce cartilage in vitro.

DESIGN

PCL nanofiber scaffolds, with or without chitosan-coating were implanted under periosteum in 6-month-old rabbits. Transforming growth factor-beta1 (TGF-beta1) or vehicle was injected into each implant site. After 1, 3, 5 or 7 days, scaffolds were removed, separated from the periosteum, and the scaffolds and periosteum were cultured separately for 6 weeks under chondrogenic conditions. Sulfated glycosaminoglycan (GAG), type II collagen, DNA content, cartilage yield, and calcium deposition were then analyzed.

RESULTS

Cell infiltration was observed in all scaffolds. Cartilage formation in the uncoated scaffolds increased with duration of implantation (maximum at 7 days). Cells in the uncoated scaffolds implanted for 7 days produced significantly higher levels of both GAG [560 (95% confidence interval (CI), 107-1013) vs 228 (95% CI, 177-278) microg GAG/microg DNA] and cartilage yield [9% (95% CI, 3-14%) vs 0.02% (95% CI, 0-0.22%)] compared to chitosan-coated scaffolds (P=0.006 or less). There was no significant difference in GAG content or cartilage yield between the TGF-beta1-injected and vehicle-injected scaffolds. However, significantly more mineral deposition was detected in TGF-beta1-injected scaffolds compared to vehicle-injected scaffolds (P<0.0001). Cartilage yield from the periosteum, moreover, was significantly increased by subperiosteal TGF-beta1 injections (P<0.001). However, this response was reduced when chitosan-coated scaffolds were implanted.

CONCLUSIONS

This study demonstrates that it is possible to seed PCL nanofiber scaffolds with periosteal cells in vivo and subsequently produce engineered cartilage in vitro.

Effects of low-intensity pulsed ultrasound, dexamethasone/TGF-beta1 and/or BMP-2 on the transcriptional expression of genes in human mesenchymal stem cells: chondrogenic vs. osteogenic differentiation

The effects of low-intensity pulsed ultrasound (LIPUS) on the differentiation of human mesenchymal stem cells (hMSCs) were investigated in this study. hMSCs were subjected to LIPUS with or without dexamethasone/transforming growth factor-beta1 (TD) or bone morphogenetic protein-2 (BMP-2) and the effects of this treatment were assessed. TD-treated hMSCs exhibited characteristic chondrogenic morphology and increased messenger RNA (mRNA) expression of chondrogenic markers and LIPUS enhanced the chondrogenic differentiation of hMSCs treated with TD. The expression of Runx2, an osteogenic transcription factor was not altered in either TD treatment group; however, a significant increase was detected in the LIPUS only group. The osteogenic appearance exhibited 3 days after LIPUS and/or BMP-2 treatment. Increases in the mRNA expression levels of osteogenic markers, Runx2 and ALP were also detected. There was no additive or altered effect with combined LIPUS and BMP-2 treatment. LIPUS alone can increase osteogenic differentiation of hMSCs and LIPUS enhances TD-mediated chondrogenic differentiation of hMSCs. Clinically, LIPUS may differentially influence bone vs. cartilage repair.

Transforming growth factor-beta1 modulates insulin-like growth factor binding protein-4 expression and proteolysis in cultured periosteal explants

OBJECTIVE

Periosteum is involved in bone growth and fracture healing and has been used as a cell source and tissue graft for tissue engineering and orthopedic reconstruction including joint resurfacing. Periosteum can be induced by transforming growth factor beta (TGF-beta) or insulin-like growth factor-I (IGF-I) alone or in combination to form cartilage. However, little is known about the interaction between IGF and TGF-beta signaling during periosteal chondrogenesis. The purpose of this study was to determine the effect of TGF-beta1 on IGF binding protein-4 (IGFBP-4) and the IGFBP-4 protease pregnancy-associated plasma protein-A (PAPP-A) expression in cultured periosteal explants.

DESIGN

Periosteal explants from rabbits were cultured with or without TGF-beta1. IGFBP-4 and PAPP-A mRNA levels were determined by real-time quantitative PCR. Conditioned medium was analyzed for IGFBP-4 and PAPP-A protein levels and IGFBP-4 protease activity.

RESULTS

TGF-beta1-treated explants contained lower IGFBP-4 mRNA levels throughout the culture period with a maximum reduction of 70% on day 5 of culture. Lower levels of IGFBP-4 protein were also detected in the conditioned medium from TGF-beta1-treated explants. PAPP-A mRNA levels were increased 1.6-fold, PAPP-A protein levels were increased threefold, and IGFBP-4 protease activity was increased 8.5-fold between 7 and 10days of culture (the onset of cartilage formation in this model) in conditioned medium from TGF-beta1-treated explants.

CONCLUSIONS

This study demonstrates that TGF-beta1 modulates the expression of IGFBP-4 and PAPP-A in cultured periosteal explants.

Structural and cellular features in metaphyseal and diaphyseal periosteum of osteoporotic rats

Despite the important physiological role of periosteum in the pathogenesis and treatment of osteoporosis, little is known about the structural and cellular characteristics of periosteum in osteoporosis. To study the structural and cellular differences in both diaphyseal and metaphyseal periosteum of osteoporotic rats, samples from the right femur of osteoporotic and normal female Lewis rats were collected and tissue sections were stained with hematoxylin and eosin, antibodies or staining kit against tartrate resistant acid phosphatase (TRAP), alkaline phosphatase (ALP), vascular endothelial growth factor (VEGF), von Willebrand (vWF), tyrosine hydroxylase (TH) and calcitonin gene-related peptide (CGRP). The results showed that the osteoporotic rats had much thicker and more cellular cambial layer of metaphyseal periosteum compared with other periosteal areas and normal rats (P < 0.001). The number of TRAP⁺ osteoclasts in bone resorption pits, VEGF⁺ cells and the degree of vascularization were found to be greater in the cambial layer of metaphyseal periosteum of osteoporotic rats (P < 0.05), while no significant difference was detected in the number of ALP⁺ cells between the two groups. Sympathetic nerve fibers identified by TH staining were predominantly located in the cambial layer of metaphyseal periosteum of osteoporotic rats. No obvious difference in the expression of CGRP between the two groups was found. In conclusion, periosteum may play an important role in the cortical bone resorption in osteoporotic rats and this pathological process may be regulated by the sympathetic nervous system.