Peripheral Blood Mononuclear Cells Enhance Cartilage Repair in in vivo Osteochondral Defect Model

Identifying transcriptomic profiles of iron-quercetin complex treated peripheral blood mononuclear cells from healthy volunteers and diabetic patients

Peripheral blood is an alternative source of stem/progenitor cells for regenerative medicine owing to its ease of retrieval and blood bank storage. Previous in vitro studies indicated that the conditioned medium derived from peripheral blood mononuclear cells (PBMCs) treated with the iron-quercetin complex (IronQ) contains potent angiogenesis and wound-healing properties. This study aims to unveil the intricate regulatory mechanisms governing the effects of IronQ on the transcriptome profiles of human PBMCs from healthy volunteers and those with diabetes mellitus (DM) using RNA sequencing analysis. Our findings revealed 3741 and 2204 differentially expressed genes (DEGs) when treating healthy and DM PBMCs with IronQ, respectively. Functional enrichment analyses underscored the biological processes shared by the DEGs in both conditions, including inflammatory responses, cell migration, cellular stress responses, and angiogenesis. A comprehensive exploration of these molecular alterations exposed a network of 20 hub genes essential in response to stimuli, cell migration, immune processes, and the mitogen-activated protein kinase (MAPK) pathway. The activation of these pathways enabled PBMCs to potentiate angiogenesis and tissue repair. Corroborating this, quantitative real-time polymerase chain reaction (qRT-PCR) and cell phenotyping confirmed the upregulation of candidate genes associated with anti-inflammatory, pro-angiogenesis, and tissue repair processes in IronQ-treated PBMCs. In summary, combining IronQ and PBMCs brings about substantial shifts in gene expression profiles and activates pathways that are crucial for tissue repair and immune response, which is promising for the enhancement of the therapeutic potential of PBMCs, especially in diabetic wound healing.

Design and fabrication of dysprosium impregnated polyvinyl alcohol hydrogels. Physiochemical, mechanical, bioimaging and in vitro evaluation

Tissue engineering has gained prominence during the past decade since it offers a key solution to defects associated with the tissue regeneration. The limited healing potential of the cartilage tissue damage has significant clinical implications. Herein, dysprosium (Dy3+) impregnated polyvinyl alcohol (PVA) hydrogels have been developed to enhance the therapeutic efficacy, enabling simultaneous diagnostic imaging and antibacterial drug delivery for potential applications in articular cartilage. Based on the favorable imaging features, Dy3+ impregnated PVA hydrogels with enhanced stability were formed through successive steps of repeated cycles of freezing at - 30 °C for 21 h, thawing at 25 °C for 4 h and lyophilization. The tensile and compression tests of the hydrogels respectively determined a maximum of 3.88 and 1.58 MPa, which reflected better compatibility towards cartilage. The hydrogels fetched a sustained drug release for a period of 12 h with an associated swelling ratio of 80%. The potential of the resultant hydrogels in image diagnosis has been deliberated through their blue and yellow emissions in the visible region. Further, the computed tomography (CT) and magnetic resonance imaging characteristics of the hydrogels respectively accomplished a maximum of 343 Hounsfiled units (HU) and relaxivity of 7.25 mM-1s-1. The cytocompatibility of the hydrogels is also determined through in vitro tests performed in Murine pro B cell line (BA/F3) and human Megakaryocyte cell line (Mo7e) cell lines.

Chondrocyte Thrombomodulin Protects against Osteoarthritis

Osteoarthritis (OA) is a prevalent form of arthritis that affects over 32.5 million adults worldwide, causing significant cartilage damage and disability. Unfortunately, there are currently no effective treatments for OA, highlighting the need for novel therapeutic approaches. Thrombomodulin (TM), a glycoprotein expressed by chondrocytes and other cell types, has an unknown role in OA. Here, we investigated the function of TM in chondrocytes and OA using various methods, including recombinant TM (rTM), transgenic mice lacking the TM lectin-like domain (TM^LeD/LeD), and a microRNA (miRNA) antagomir that increased TM expression. Results showed that chondrocyte-expressed TM and soluble TM [sTM, like recombinant TM domain 1 to 3 (rTMD123)] enhanced cell growth and migration, blocked interleukin-1β (IL-1β)-mediated signaling and protected against knee function and bone integrity loss in an anterior cruciate ligament transection (ACLT)-induced mouse model of OA. Conversely, TM^LeD/LeD mice exhibited accelerated knee function loss, while treatment with rTMD123 protected against cartilage loss even one-week post-surgery. The administration of an miRNA antagomir (miR-up-TM) also increased TM expression and protected against cartilage damage in the OA model. These findings suggested that chondrocyte TM plays a crucial role in counteracting OA, and miR-up-TM may represent a promising therapeutic approach to protect against cartilage-related disorders.

Peripheral Blood-Derived Stem Cells for the Treatment of Cartilage Injuries: A Systematic Review

Background: The treatment of cartilage damage is a hot topic at present, and cell therapy is an emerging alternative therapy. Stem cells derived from peripheral blood have become the focus of current research due to the ease of obtaining materials and a wide range of sources.

Methods: We used a text search strategy using the [“mesenchymal stem cells” (MeSH term) OR “MSC” OR “BMMSC” OR “PBMSC” OR” PBMNC” OR “peripheral blood stem cells”] AND (cartilage injury [MeSH term] OR “cartilage” OR “chondral lesion”). After searching the literature, through the inclusion and exclusion criteria, the last included articles were systematically reviewed.

Result: We found that peripheral blood-derived stem cells have chondrogenic differentiation ability and can induce chondrogenic differentiation and repair in vivo and have statistical significance in clinical and imaging prognosis. It is an improvement of academic differences. Compared with the bone marrow, peripheral blood is easier to obtain, widely sourced, and simple to obtain. In the future, peripheral blood will be a more potential cell source for cell therapy in the treatment of cartilage damage.

Conclusion: Stem cells derived from peripheral blood can repair cartilage and are an important resource for the treatment of cartilage damage in the future. The specific mechanism and way of repairing cartilage need further study.

Autologous Immune Cell-Based Regenerative Therapies to Treat Vasculogenic Erectile Dysfunction: Is the Immuno-Centric Revolution Ready for the Prime Time?

About 35% of patients affected by erectile dysfunction (ED) do not respond to oral phosphodiesterase-5 inhibitors (PDE5i) and more severe vasculogenic refractory ED affects diabetic patients. Innovative approaches, such as regenerative therapies, including stem cell therapy (SCT) and platelet-rich plasma (PRP), are currently under investigation. Recent data point out that the regenerative capacity of stem cells is strongly influenced by local immune responses, with macrophages playing a pivotal role in the injury response and as a coordinator of tissue regeneration, suggesting that control of the immune response could be an appealing approach in regenerative medicine. A new generation of autologous cell therapy based on immune cells instead of stem cells, which could change regenerative medicine for good, is discussed. Increasing safety and efficacy data are coming from clinical trials using peripheral blood mononuclear cells to treat no-option critical limb ischemia and diabetic foot. In this review, ongoing phase 1/phase 2 stem cell clinical trials are discussed. In addition, we examine the mechanism of action and rationale, as well as propose a new generation of regenerative therapies, evolving from typical stem cell or growth factor to immune cell-based medicine, based on autologous peripheral blood mononuclear cells (PBMNC) concentrates for the treatment of ED.

Small Ruminant Models for Articular Cartilage Regeneration by Scaffold-Based Tissue Engineering

Animal models play an important role in preclinical studies, especially in tissue engineering scaffolds for cartilage repair, which require large animal models to verify the safety and effectiveness for clinical use. The small ruminant models are most widely used in this field than other large animals because they are cost-effective, easy to raise, not to mention the fact that the aforementioned animal presents similar anatomical features to that of humans. This review discusses the experimental study of tissue engineering scaffolds for knee articular cartilage regeneration in small ruminant models. Firstly, the selection of these scaffold materials and the preparation process in vitro that have been already used in vivo are briefly reviewed. Moreover, the major factors influencing the rational design and the implementation as well as advantages and limitations of small ruminants are also demonstrated. As regards methodology, this paper applies principles and methods followed by most researchers in the process of experimental design and operation of this kind. By summarizing and comparing different therapeutic concepts, this paper offers suggestions aiming to increase the effectiveness of preclinical research using small ruminant models and improve the process of developing corresponding therapies.

Skeletal regeneration for segmental bone loss: Vascularised grafts, analogues and surrogates

Massive segmental bone defects (SBD) are mostly treated by removing the fibula and transplanting it complete with blood supply. While revolutionary 50 years ago, this remains the standard treatment. This review considers different strategies to repair SBD and emerging potential replacements for this highly invasive procedure. Prior to the technical breakthrough of microsurgery, researchers in the 1960s and 1970s had begun to make considerable progress in developing non autologous routes to repairing SBD. While the breaktthrough of vascularised bone transplantation solved the immediate problem of a lack of reliable repair strategies, much of their prior work is still relevant today. We challenge the assumption that mimicry is necessary or likely to be successful and instead point to the utility of quite crude (from a materials technology perspective), approaches. Together there are quite compelling indications that the body can regenerate entire bone segments with few or no exogenous factors. This is important, as there is a limit to how expensive a bone repair can be and still be widely available to all patients since cost restraints within healthcare systems are not likely to diminish in the near future. STATEMENT OF SIGNIFICANCE: This review is significant because it is a multidisciplinary view of several surgeons and scientists as to what is driving improvement in segmental bone defect repair, why many approaches to date have not succeeded and why some quite basic approaches can be as effective as they are. While there are many reviews of the literature of grafting and bone repair the relative lack of substantial improvement and slow rate of progress in clinical translation is often overlooked and we seek to challenge the reader to consider the issue more broadly.

Articular cartilage and osteochondral tissue engineering techniques: Recent advances and challenges

In spite of the considerable achievements in the field of regenerative medicine in the past several decades, osteochondral defect regeneration remains a challenging issue among diseases in the musculoskeletal system because of the spatial complexity of osteochondral units in composition, structure and functions. In order to repair the hierarchical tissue involving different layers of articular cartilage, cartilage-bone interface and subchondral bone, traditional clinical treatments including palliative and reparative methods have showed certain improvement in pain relief and defect filling. It is the development of tissue engineering that has provided more promising results in regenerating neo-tissues with comparable compositional, structural and functional characteristics to the native osteochondral tissues. Here in this review, some basic knowledge of the osteochondral units including the anatomical structure and composition, the defect classification and clinical treatments will be first introduced. Then we will highlight the recent progress in osteochondral tissue engineering from perspectives of scaffold design, cell encapsulation and signaling factor incorporation including bioreactor application. Clinical products for osteochondral defect repair will be analyzed and summarized later. Moreover, we will discuss the current obstacles and future directions to regenerate the damaged osteochondral tissues.

Cell and Cell Free Therapies in Osteoarthritis

Osteoarthritis (OA) is the most common articular disease in adults and has a current prevalence of 12% in the population over 65 years old. This chronic disease causes damage to articular cartilage and synovial joints, causing pain and leading to a negative impact on patients' function, decreasing quality of life. There are many limitations regarding OA conventional therapies-pharmacological therapy can cause gastrointestinal, renal, and cardiac adverse effects, and some of them could even be a threat to life. On the other hand, surgical options, such as microfracture, have been used for the last 20 years, but hyaline cartilage has a limited regeneration capacity. In recent years, the interest in new therapies, such as cell-based and cell-free therapies, has been considerably increasing. The purpose of this review is to describe and compare bioregenerative therapies' efficacy for OA, with particular emphasis on the use of mesenchymal stem cells (MSCs) and platelet-rich plasma (PRP). In OA, these therapies might be an alternative and less invasive treatment than surgery, and a more effective option than conventional therapies.

Editorial Commentary: Cell-Based Therapies for Articular Cartilage Repair Require Precise Progenitor Cell Characterization and Determination of Mechanism of Action

Biologics and cell-based therapies, in particular, have come to the forefront of orthopaedic sports medicine as agents with therapeutic and regenerative potential. Autologous chondrocyte implantation has been used successfully for many years, but a recent focus on autologous progenitor cells derived from bone marrow aspirate, adipose tissue, and/or synovium has garnered significant interest. Mobilized peripheral blood mononuclear cells [PBMCs or connective tissue progenitors (CTPs)] represent a promising cell population for potential use in articular cartilage repair. The term "stem cell" has become widely popularized, but more specific language identifying the cell type by donor type, tissue of origin, cell surface marker profile, culture conditions, and other cell behavior/characteristics should be used. In 2019, Murray et al. proposed a five-item "DOSES" tool in an effort to encourage standardized reporting for cell-based therapies emphasizing donor, origin of tissue, separation from other cell types/preparation method, exhibited cell characteristics associated with behavior, and site of delivery. The advantages of the DOSES tool include both simplicity and ability to be applied to cell types not yet discovered. However, a universally accepted list of criteria for biologics does not yet exist. Additional research is necessary to better elucidate the precise mechanisms by which cell therapies have a clinical effect and define whether the therapies for the treatment of cartilage pathology merely help alleviate symptoms or actually provide structural improvements. There are few data to suggest exogenous cell therapies directly engraft, so identifying the paracrine mediators produced by these cells would be an area of further interest.

Mobilized Peripheral Blood Stem Cells are Pluripotent and Can Be Safely Harvested and Stored for Cartilage Repair

PURPOSE

The primary objective of this study was to reproduce and validate the harvest, processing and storage of peripheral blood stem cells for a subsequent cartilage repair trial, evaluating safety, reliability, and potential to produce viable, sterile stem cells.

METHODS

Ten healthy subjects (aged 19-44 years) received 3 consecutive daily doses of filgrastim followed by an apheresis harvest of mononuclear cells on a fourth day. In a clean room, the apheresis product was prepared for cryopreservation and processed into 4 mL aliquots. Sterility and qualification testing were performed pre-processing and post-processing at multiple time points out to 2 years. Eight samples were shipped internationally to validate cell transport potential. One sample from all participants was cultured to test proliferative potential with colony forming unit (CFU) assay. Five samples, from 5 participants were tested for differentiation potential, including chondrogenic, adipogenic, osteogenic, endoderm, and ectoderm assays.

RESULTS

Fresh aliquots contained an average of 532.9 ± 166. × 10⁶ total viable cells/4 mL vial and 2.1 ± 1.0 × 10⁶ CD34+ cells/4 mL vial. After processing for cryopreservation, the average cell count decreased to 331.3 ± 79. × 10⁶ total viable cells /4 mL vial and 1.5 ± 0.7 × 10⁶ CD34+ cells/4 mL vial CD34+ cells. Preprocessing viability averaged 99% and postprocessing 88%. Viability remained constant after cryopreservation at all subsequent time points. All sterility testing was negative. All samples showed proliferative potential, with average CFU count 301.4 ± 63.9. All samples were pluripotent.

CONCLUSIONS

Peripheral blood stem cells are pluripotent and can be safely harvested/stored with filgrastim, apheresis, clean-room processing, and cryopreservation. These cells can be stored for 2 years and shipped without loss of viability.

CLINICAL RELEVANCE

This method represents an accessible stem cell therapy in development to augment cartilage repair.

Arthroscopic Subchondral Drilling Followed by Injection of Peripheral Blood Stem Cells and Hyaluronic Acid Showed Improved Outcome Compared to Hyaluronic Acid and Physiotherapy for Massive Knee Chondral Defects: A Randomized Controlled Trial

PURPOSE

The purpose of this study was to evaluate the safety and efficacy of intra-articular injections of autologous peripheral blood stem cells (PBSCs) plus hyaluronic acid (HA) after arthroscopic subchondral drilling into massive chondral defects of the knee joint and to determine whether PBSC therapy can improve functional outcome and reduce pain of the knee joint better than HA plus physiotherapy.

METHODS

This is a dual-center randomized controlled trial (RCT). Sixty-nine patients aged 18 to 55 years with International Cartilage Repair Society grade 3 and 4 chondral lesions (size ≥3 cm²) of the knee joint were randomized equally into (1) a control group receiving intra-articular injections of HA plus physiotherapy and (2) an intervention group receiving arthroscopic subchondral drilling into chondral defects and postoperative intra-articular injections of PBSCs plus HA. The coprimary efficacy endpoints were subjective International Knee Documentation Committee (IKDC) and Knee Injury and Osteoarthritis Outcome Score (KOOS)-pain subdomain measured at month 24. The secondary efficacy endpoints included all other KOOS subdomains, Numeric Rating Scale (NRS), and Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART) scores.

RESULTS

At 24 months, the mean IKDC scores for the control and intervention groups were 48.1 and 65.6, respectively (P < .0001). The mean for KOOS-pain subdomain scores were 59.0 (control) and 86.0 (intervention) with P < .0001. All other KOOS subdomain, NRS, and MOCART scores were statistically significant (P < .0001) at month 24. Moreover, for the intervention group, 70.8% of patients had IKDC and KOOS-pain subdomain scores exceeding the minimal clinically important difference values, indicating clinical significance. There were no notable adverse events that were unexpected and related to the study drug or procedures.

CONCLUSIONS

Arthroscopic marrow stimulation with subchondral drilling into massive chondral defects of the knee joint followed by postoperative intra-articular injections of autologous PBSCs plus HA is safe and showed a significant improvement of clinical and radiologic scores compared with HA plus physiotherapy.

LEVEL OF EVIDENCE

Level I, RCT.

Using apheresis-derived cells to augment microdrilling in the treatment of chondral defects in an ovine model

The treatment of chondral defects using microdrilling often results in a mechanically weak fibrocartilagenous repair, rather than a more robust hyaline cartilage repair. Many different microfracture/microdrilling augmentation techniques have been described, including the use of cellular products to enhance healing. Autologous peripheral blood progenitor cells can be obtained via apheresis after administration of granulocyte colony-stimulating factor (G-CSF) and have been used successfully to augment microdrilling in clinical patients. The objective of this study was to use apheresis-derived mononuclear blood cells to augment microdrilling treatment of a cartilage defect in an ovine model to determine the effect on healing. Forty adult female sheep were used in this study and were divided into a control group (microdrilling alone) and a treatment group (microdrilling, hyaluronic acid, and apheretic product). Outcome measurements included weight-bearing on the operated limb, macroscopic scoring of the joint, histology, and immunohistochemistry. In addition, magnetic resonance imaging was used to attempt to identify SPION-labeled cells from the apheretic product in the operated limbs. The results showed a significant increase in healing as measured by the modified O'Driscoll sore in the treated group. No evidence of homing of SPION-labeled cells to the defect was found and no correlation was found between the response to G-CSF administration or concentration of CD34⁺  and outcome. A correlation was found between healing and the concentration of white blood cells and peripheral blood mononuclear cell numbers in the apheretic product.

Quantification and Qualification of Stem Cells From Blood After Mobilization With Filgrastim, and Concentration Using a Platelet-Rich Plasma System

PURPOSE

To determine the cellular composition of a product created with peripheral blood harvested after systemic mobilization with filgrastim and processed with one point-of-care blood concentrating system, i.e., a platelet-rich plasma (PRP) system. The second purpose was to compare mobilized platelet-rich plasma (M-PRP) with a concentrated bone marrow aspirate (cBMA) and a PRP created from the same subjects with the same PRP system.

METHODS

Ten healthy volunteer subjects were recruited for collection and analysis of 3 tissue sources: non-treated peripheral blood, bone marrow aspirate, and filgrastim-mobilized peripheral blood, involving 4 doses of weight-based filgrastim. One point-of-care blood and bone marrow concentrating system was used to create 3 products: PRP, cBMA, and M-PRP. Automated hematologic analysis was performed on all products to quantify total red blood cells, white blood cells (WBCs), monocyte, platelet, and hematopoietic progenitor cell (HPC) concentrations. Flow cytometry was used to determine hematopoietic and mesenchymal progenitor cell populations. Lastly, concentrates were cultured and fibroblast colony-forming units (CFU-F) and morphology of adherent cells were evaluated.

RESULTS

M-PRP contained a greater concentration of WBC (mean difference = 53.2 k/μL; P < .0001), monocytes (mean difference = 8.3 k/μL; P = .002), and a trend toward a greater concentration of HPC (mean difference = 200.5 /μL; P = .060) when compared with PRP. M-PRP contained a greater concentration of monocytes (mean difference = 5.5 k/μL; P = .017) and a trend toward a greater concentration of platelets (mean difference = 348 k/μL; P = .051) and HPC (mean difference = 193.4 /μL; P = .068) when compared with cBMA. M-PRP had a similar concentration of platelets to PRP (mean difference = 110 k/μL; P = .051) and PRP had a greater concentration than cBMA (mean difference = 458 k/μL; P = .003). cBMA remained the only product capable of producing CFU-Fs (446 ± 247 /mL) as neither the M-PRP nor PRP produced CFU-Fs. M-PRP produced colonies consistent with WBC.

CONCLUSIONS

M-PRP, produced with filgrastim mobilized blood and a proprietary PRP system, contained more total WBCs, monocytes, platelets, and HPCs than cBMA and more WBCs, monocytes, and HPCs than PRP.

CLINICAL RELEVANCE

Filgrastim mobilized PRP may be an alternative to cBMA for use as a point-of-care product for orthopaedic treatments.

Mesenchymal or Maintenance Stem Cell & Understanding Their Role in Osteoarthritis of the Knee Joint: A Review Article

Mesenchymal Stem Cell (MSC) therapy in osteoarthritis has been hailed as a promising treatment for osteoarthritis due to their unlimited potential of healing and regeneration. Existing literature regarding their proper name, optimal sources, mechanisms of action, dosage, and route of administration, efficacy, and safety is debatable. This index review article has tried to connect these puzzling pieces of available information and brought clarity on some of these crucial issues. The author believes that Maintenance Stem Cells (MSC) may be a more suitable term than mesenchymal stem cell or medicinal signaling cells as their origin might not be limited to mesodermal tissue. Also, they have been shown capable of self-renewal, differentiation, and maintaining a cascade of healing & possibly regeneration at the implanted site. Only a small percentage of implanted MSC survive and rest undergo apoptosis after releasing growth factors, cytokines, and extracellular vesicles. These surviving MSC become active due to conformational changes induced by anti-environment stimuli and undergo limited self-renewal, proliferation, and differentiation, but only a few of them might incorporate into the host tissues. These cells generate & maintain a momentum of series of regenerative activities to improve the function of joint, stabilize or possibly enhance the cartilage quality. More randomized studies with long term follow-up are required to bring clarity on their ideal source, expansion, culture technique, optimum dosage, and route of administration and long-term safety issues.

Corneal Recovery Following Rabbit Peripheral Blood Mononuclear Cell-Amniotic Membrane Transplantation with Antivascular Endothelial Growth Factor in Limbal Stem Cell Deficiency Rabbits

Background: Limbal stem cell deficiency (LSCD) is a refractory ocular surface disorder characterized by progressive corneal epithelial degeneration, conjunctivalization, and neovascularization, potentially leading to blindness. There are currently no effective therapeutic options for patients experiencing routine symptomatic treatment failure. Transplantation of amniotic membrane (AM) with adherent stem cells (but not bare AM transplantation alone) has shown promise in preclinical studies for ocular surface restoration. A major limitation, however, is finding a reliable stem cell source. Stem cells can be isolated from the peripheral blood mononuclear cell (PBMC) population, and these PBMC-derived stem cells have numerous advantages over allogeneic and other autologous stem cell types for therapeutic application, including relative ease of acquisition, nonimmunogenicity, and the absence of ethical issues associated with embryonic stem cells. Experiment: We examined the efficacy of autologous PBMC-AM sheet cultures combined with postoperative antiangiogenesis treatment for corneal restoration in LSCD model rabbits. Rabbit PBMCs (rPBMCs) were isolated, labeled with EdU for in vivo tracing, and then cultured on AMs in conditioned medium before transplantation. Rabbits were transplanted with bare AMs (group 1), rPBMC-AM sheets (group 2), or rPBMC-AM sheets plus postoperative treatment with the vascular endothelial growth factor antagonist bevacizumab (group 3). Corneal opacity and neovascularization were monitored by slit-lamp imaging for 8 weeks and corneas were examined histologically at 1 and 2 months. Results: Corneal opacity decreased in all three groups over 8 weeks, but was significantly lower in group 2 and even lower in group 3. Corneal neovascularization was significantly higher in group 1 throughout the observation period, and significantly lower in group 3 than group 1 and 2 by 8 weeks post-transplant. At 4 weeks, the corneal surface completed epithelialization (although thinner than normal) in group 3 but still patchy in groups 1 and 2. By 8 weeks, the epithelium in group 3 was complete and smooth, resembling a normal epithelium. Integrin β1 as a progenitor marker was also generally higher in groups 2 and 3. Conclusions: Autologous rPBMC-AM sheets with post-transplant topical bevacizumab can effectively facilitate corneal epithelium recovery in a LSCD model, suggesting clinical utility for LSCD-related ocular surface diseases. Impact statement Limbal stem cell deficiency (LSCD) increases corneal opacity and vascularization, resulting in severe visual impairment or even blindness. Traditional surgical limbal transplant is currently the main treatment option for LSCD, but carries the risks of rejection and immunosuppressant side effects. Autologous stem cell-based therapy is a promising alternative approach, but a reliable stem cell source is a major limitation. We report that transplantation of autologous rabbit peripheral blood mononuclear cell-amniotic membrane sheets plus antivascular endothelial growth factor restored avascular transparent cornea in a rabbit LSCD model. These results demonstrate a potentially effective approach for ocular surface reconstruction in bilateral LSCD.

Role of the CXCR4-SDF1-HMGB1 pathway in the directional migration of cells and regeneration of affected organs

In recent years, several studies have reported positive outcomes of cell-based therapies despite insufficient engraftment of transplanted cells. These findings have created a huge interest in the regenerative potential of paracrine factors released from transplanted stem or progenitor cells. Interestingly, this notion has also led scientists to question the role of proteins in the secretome produced by cells, tissues or organisms under certain conditions or at a particular time of regenerative therapy. Further studies have revealed that the secretomes derived from different cell types contain paracrine factors that could help to prevent apoptosis and induce proliferation of cells residing within the tissues of affected organs. This could also facilitate the migration of immune, progenitor and stem cells within the body to the site of inflammation. Of these different paracrine factors present within the secretome, researchers have given proper consideration to stromal cell-derived factor-1 (SDF1) that plays a vital role in tissue-specific migration of the cells needed for regeneration. Recently researchers recognized that SDF1 could facilitate site-specific migration of cells by regulating SDF1-CXCR4 and/or HMGB1-SDF1-CXCR4 pathways which is vital for tissue regeneration. Hence in this study, we have attempted to describe the role of different types of cells within the body in facilitating regeneration while emphasizing the HMGB1-SDF1-CXCR4 pathway that orchestrates the migration of cells to the site where regeneration is needed.

Large Animal Models in Regenerative Medicine and Tissue Engineering: To Do or Not to Do

Rapid developments in Regenerative Medicine and Tissue Engineering has witnessed an increasing drive toward clinical translation of breakthrough technologies. However, the progression of promising preclinical data to achieve successful clinical market authorisation remains a bottleneck. One hurdle for progress to the clinic is the transition from small animal research to advanced preclinical studies in large animals to test safety and efficacy of products. Notwithstanding this, to draw meaningful and reliable conclusions from animal experiments it is critical that the species and disease model of choice is relevant to answer the research question as well as the clinical problem. Selecting the most appropriate animal model requires in-depth knowledge of specific species and breeds to ascertain the adequacy of the model and outcome measures that closely mirror the clinical situation. Traditional reductionist approaches in animal experiments, which often do not sufficiently reflect the studied disease, are still the norm and can result in a disconnect in outcomes observed between animal studies and clinical trials. To address these concerns a reconsideration in approach will be required. This should include a stepwise approach using in vitro and ex vivo experiments as well as in silico modeling to minimize the need for in vivo studies for screening and early development studies, followed by large animal models which more closely resemble human disease. Naturally occurring, or spontaneous diseases in large animals remain a largely untapped resource, and given the similarities in pathophysiology to humans they not only allow for studying new treatment strategies but also disease etiology and prevention. Naturally occurring disease models, particularly for longer lived large animal species, allow for studying disorders at an age when the disease is most prevalent. As these diseases are usually also a concern in the chosen veterinary species they would be beneficiaries of newly developed therapies. Improved awareness of the progress in animal models is mutually beneficial for animals, researchers, human and veterinary patients. In this overview we describe advantages and disadvantages of various animal models including domesticated and companion animals used in regenerative medicine and tissue engineering to provide an informed choice of disease-relevant animal models.

Hydrogel Containing Anti-CD44-Labeled Microparticles, Guide Bone Tissue Formation in Osteochondral Defects in Rabbits

Hydrogels are suitable for osteochondral defect regeneration as they mimic the viscoelastic environment of cartilage. However, their biomechanical properties are not sufficient to withstand high mechanical forces. Therefore, we have prepared electrospun poly-ε-caprolactone-chitosan (PCL-chit) and poly(ethylene oxide)-chitosan (PEO-chit) nanofibers, and FTIR analysis confirmed successful blending of chitosan with other polymers. The biocompatibility of PCL-chit and PEO-chit scaffolds was tested; fibrochondrocytes and chondrocytes seeded on PCL-chit showed superior metabolic activity. The PCL-chit nanofibers were cryogenically grinded into microparticles (mean size of about 500 µm) and further modified by polyethylene glycol-biotin in order to bind the anti-CD44 antibody, a glycoprotein interacting with hyaluronic acid (PCL-chit-PEGb-antiCD44). The PCL-chit or PCL-chit-PEGb-antiCD44 microparticles were mixed with a composite gel (collagen/fibrin/platelet rich plasma) to improve its biomechanical properties. The storage modulus was higher in the composite gel with microparticles compared to fibrin. The Eloss of the composite gel and fibrin was higher than that of the composite gel with microparticles. The composite gel either with or without microparticles was further tested in vivo in a model of osteochondral defects in rabbits. PCL-chit-PEGb-antiCD44 significantly enhanced osteogenic regeneration, mainly by desmogenous ossification, but decreased chondrogenic differentiation in the defects. PCL-chit-PEGb showed a more homogeneous distribution of hyaline cartilage and enhanced hyaline cartilage differentiation.

Peripheral Blood As a Source of Stem Cells for Regenerative Medicine: Emphasis Towards Corneal Epithelial Reconstruction-An In Vitro Study

BACKGROUND

Mesenchymal stem cell-based treatments are now emerging as a therapy for corneal epithelial damage. Although bone marrow, adipose tissue and umbilical cord blood are the main sources of mesenchymal stem cells (MSCs), other tissues like the peripheral blood also harbor mesenchymal-like stem cells called peripheral blood-derived mononuclear cells (PBMNCs). These blood derived stem cells gained a lot of attention due to its minimally invasive collection and ease of isolation. In this study, the feasibility of using PBMNCs as an alternative cell source to corneal limbal stem cells envisaging corneal epithelial regeneration was evaluated.

METHODS

Rabbit PBMNCs were isolated using density gradient centrifugation and was evaluated for mesenchymal cell properties including stemness. PBMNCs were differentiated to corneal epithelial lineage using rabbit limbal explant conditioned media and was evaluated by immuno-cytochemistry and gene expression analysis. Further, the differentiated PBMNCs were engineered into a cell sheet using an in-house developed thermo-responsive polymer.

RESULTS

These blood derived cells were demonstrated to have similar properties to mesenchymal stem cells. Corneal epithelial lineage commitment of PBMNCs was confirmed by the positive expression of CK3/12 marker thereby demonstrating the aptness as an alternative to limbal stem cells. These differentiated cells effectively generated an in vitro cell sheet that was then demonstrated for cell sheet transfer on an ex vivo excised rabbit eye.

CONCLUSION

PBMNCs as an alternative autologous cell source for limbal stem cells is envisaged as an effective therapeutic strategy for corneal surface reconstruction especially for patients with bilateral limbal stem cell deficiency.

The Use of Peripheral Blood-Derived Stem Cells for Cartilage Repair and Regeneration In Vivo: A Review

Background

Peripheral blood (PB) is a potential source of chondrogenic progenitor cells that can be used for cartilage repair and regeneration. However, the cell types, isolation and implantation methods, seeding dosage, ultimate therapeutic effect, and in vivo safety remain unclear.

Methods

PubMed, Embase, and the Web of Science databases were systematically searched for relevant reports published from January 1990 to December 2019. Original articles that used PB as a source of stem cells to repair cartilage in vivo were selected for analysis.

Results

A total of 18 studies were included. Eight human studies used autologous nonculture-expanded PB-derived stem cells (PBSCs) as seed cells with the blood cell separation isolation method, and 10 animal studies used autologous, allogenic or xenogeneic culture-expanded PB-derived mesenchymal stem cells (PB-MSCs), or nonculture-expanded PBSCs as seed cells. Four human and three animal studies surgically implanted cells, while the remaining studies implanted cells by single or repeated intra-articular injections. 121 of 130 patients (in 8 human clinical studies), and 230 of 278 animals (in 6 veterinary clinical studies) using PBSCs for cartilage repair achieved significant clinical improvement. All reviewed articles indicated that using PB as a source of seed cells enhances cartilage repair in vivo without serious adverse events.

Conclusion

Autologous nonculture-expanded PBSCs are currently the most commonly used cells among all stem cell types derived from PB. Allogeneic, autologous, and xenogeneic PB-MSCs are more widely used in animal studies and are potential seed cell types for future applications. Improving the mobilization and purification technology, and shortening the culture cycle of culture-expanded PB-MSCs will obviously promote the researchers' interest. The use of PBSCs for cartilage repair and regeneration in vivo are safe. PBSCs considerably warrant further investigations due to their superiority and safety in clinical settings and positive effects despite limited evidence in humans.

Can Hypoxic Conditioning Improve Bone Metabolism? A Systematic Review

Among other functions, hypoxia-inducible factor plays a critical role in bone–vascular coupling and bone formation. Studies have suggested that hypoxic conditioning could be a potential nonpharmacological strategy for treating skeletal diseases. However, there is no clear consensus regarding the bone metabolism response to hypoxia. Therefore, this review aims to examine the impact of different modes of hypoxia conditioning on bone metabolism. The PubMed and Web of Science databases were searched for experimental studies written in English that investigated the effects of modification of ambient oxygen on bone remodelling parameters of healthy organisms. Thirty-nine studies analysed the effect of sustained or cyclic hypoxia exposure on genetic and protein expression and mineralisation capacity of different cell models; three studies carried out in animal models implemented sustained or cyclic hypoxia; ten studies examined the effect of sustained, intermittent or cyclic hypoxia on bone health and hormonal responses in humans. Different modes of hypoxic conditioning may have different impacts on bone metabolism both in vivo and in vitro. Additional research is necessary to establish the optimal cyclical dose of oxygen concentration and exposure time.

A Growth Factor-Free Co-Culture System of Osteoblasts and Peripheral Blood Mononuclear Cells for the Evaluation of the Osteogenesis Potential of Melt-Electrowritten Polycaprolactone Scaffolds

Scaffolds made of biodegradable biomaterials are widely used to guide bone regeneration. Commonly, in vitro assessment of scaffolds’ osteogenesis potential has been performed predominantly in monoculture settings. Hence, this study evaluated the potential of an unstimulated, growth factor-free co-culture system comprised of osteoblasts (OB) and peripheral blood mononuclear cells (PBMC) over monoculture of OB as an in vitro platform for screening of bone regeneration potential of scaffolds. Particularly, this study focuses on the osteogenic differentiation and mineralized matrix formation aspects of cells. The study was performed using scaffolds fabricated by means of a melt electrowriting (MEW) technique made of medical-grade polycaprolactone (PCL), with or without a surface coating of calcium phosphate (CaP). Qualitative results, i.e., cell morphology by fluorescence imaging and matrix mineralization by von Kossa staining, indicated the differences in cell behaviours in response to scaffolds’ biomaterial. However, no obvious differences were noted between OB and OB+PBMC groups. Hence, quantitative investigation, i.e., alkaline phosphatase (ALP), tartrate-resistant acid phosphatase (TRAP) activities, and gene expression were quantitatively evaluated by reverse transcription-polymerase chain reaction (RT-qPCR), were evaluated only of PCL/CaP scaffolds cultured with OB+PBMC, while PCL/CaP scaffolds cultured with OB or PBMC acted as a control. Although this study showed no differences in terms of osteogenic differentiation and ECM mineralization, preliminary qualitative results indicate an obvious difference in the cell/non-mineralized ECM density between scaffolds cultured with OB or OB+PBMC that could be worth further investigation. Collectively, the unstimulated, growth factor-free co-culture (OB+PBMC) system presented in this study could be beneficial for the pre-screening of scaffolds’ in vitro bone regeneration potential prior to validation in vivo.

Comparative efficacy of stem cells and secretome in articular cartilage regeneration: a systematic review and meta-analysis

Articular cartilage defect remains the most challenging joint disease due to limited intrinsic healing capacity of the cartilage that most often progresses to osteoarthritis. In recent years, stem cell therapy has evolved as therapeutic strategies for articular cartilage regeneration. However, a number of studies have shown that therapeutic efficacy of stem cell transplantation is attributed to multiple secreted factors that modulate the surrounding milieu to evoke reparative processes. This systematic review and meta-analysis aim to evaluate and compare the therapeutic efficacy of stem cell and secretome in articular cartilage regeneration in animal models. We systematically searched the PubMed, CINAHL, Cochrane Library, Ovid Medline and Scopus databases until August 2017 using search terms related to stem cells, cartilage regeneration and animals. A random effect meta-analysis of the included studies was performed to assess the treatment effects on new cartilage formation on an absolute score of 0-100% scale. Subgroup analyses were also performed by sorting studies independently based on similar characteristics. The pooled analysis of 59 studies that utilized stem cells significantly improved new cartilage formation by 25.99% as compared with control. Similarly, the secretome also significantly increased cartilage regeneration by 26.08% in comparison to the control. Subgroup analyses revealed no significant difference in the effect of stem cells in new cartilage formation. However, there was a significant decline in the effect of stem cells in articular cartilage regeneration during long-term follow-up, suggesting that the duration of follow-up is a predictor of new cartilage formation. Secretome has shown a similar effect to stem cells in new cartilage formation. The risk of bias assessment showed poor reporting for most studies thereby limiting the actual risk of bias assessment. The present study suggests that both stem cells and secretome interventions improve cartilage regeneration in animal trials. Graphical abstract ᅟ.

Stem Cell Therapy for Articular Cartilage Repair: Review of the Entity of Cell Populations Used and the Result of the Clinical Application of Each Entity

BACKGROUND

Following successful preclinical studies, stem cell therapy is emerging as a candidate for the treatment of articular cartilage lesions. Because stem cell therapy for cartilage repair in humans is at an early phase, confusion and errors are found in the literature regarding use of the term stem cell therapy in this field.

PURPOSE

To provide an overview of the outcomes of cartilage repair, elucidating the various cell populations used, and thus reduce confusion with regard to using the term stem cell therapy.

STUDY DESIGN

Systematic review.

METHODS

The authors systematically reviewed any studies on clinical application of mesenchymal stem cells (MSCs) in human subjects. A comprehensive search was performed in MEDLINE, EMBASE, the Cochrane Library, CINAHL, Web of Science, and Scopus for human studies that evaluated articular cartilage repair with cell populations containing MSCs. These studies were classified as using bone marrow-derived MSCs, adipose tissue-derived MSCs, peripheral blood-derived MSCs, synovium-derived MSCs, and umbilical cord blood-derived MSCs according to the entity of cell population used.

RESULTS

Forty-six clinical studies were identified to focus on cartilage repair with MSCs: 20 studies with bone marrow-derived MSCs, 21 studies with adipose tissue-derived MSCs, 3 studies with peripheral blood-derived MSCs, 1 study with synovium-derived MSCs, and 1 study with umbilical cord blood-derived MSCs. All clinical studies reported that cartilage treated with MSCs showed favorable clinical outcomes in terms of clinical scores or cartilage repair evaluated by MRI. However, most studies were limited to case reports and case series. Among these 46 clinical studies, 18 studies erroneously referred to adipose tissue-derived stromal vascular fractions as "adipose-derived MSCs," 2 studies referred to peripheral blood-derived progenitor cells as "peripheral blood-derived MSCs," and 1 study referred to bone marrow aspirate concentrate as "bone marrow-derived MSCs."

CONCLUSION

Limited evidence is available regarding clinical benefit of stem cell therapy for articular cartilage repair. Because the literature contains substantial errors in describing the therapeutic cells used, researchers need to be alert and observant of proper terms, especially regarding whether the cells used were stem cells or cell populations containing a small portion of stem cells, to prevent confusion in understanding the results of a given stem cell-based therapy.

Repair potential of nonsurgically delivered induced pluripotent stem cell-derived chondrocytes in a rat osteochondral defect model

Human induced pluripotent stem cells (hiPSCs) are thought to be an alternative cell source for future regenerative medicine. hiPSCs may allow unlimited production of cell types that have low turnover rates and are difficult to obtain such as autologous chondrocytes. In this study, we generated hiPSC-derived chondrogenic pellets, and chondrocytes were isolated. To confirm the curative effects, chondrogenic pellets and isolated chondrocytes were transplanted into rat joints with osteochondral defects. Isolated hiPSC-derived chondrocytes were delivered in the defect by a single intra-articular injection. The generated hiPSC-derived chondrogenic pellets had increased chondrogenic marker expression and accumulated extracellular matrix proteins. Chondrocytes were successfully isolated from the pellets. Alcian blue staining and collagen type II were detected in the cells. Chondrogenic marker expression was also increased in the isolated cells. Transplanted chondrogenic pellets and chondrocytes both had curative effects in the osteochondral defect rat model. Detection of human proteins in the joints proved that the cells were successfully delivered into the defect. Chondrogenic pellets or chondrocytes generated from hiPSCs have potential as regenerative medicine for cartilage recovery or regeneration. Chondrocytes isolated from hiPSC-derived chondrogenic pellets had curative effects in damaged cartilage. Injectable hiPSC-derived chondrocytes show the possibility of noninvasive delivery of regenerative medicine for cartilage recovery.

Osteoarthritis and stem cell therapy in humans: a systematic review

OBJECTIVE

Osteoarthritis (OA) is a leading cause of disability in the world. Mesenchymal stem cells (MSCs) have been studied to treat OA. This review was performed to systematically assess the quality of literature and compare the procedural specifics surrounding MSC therapy for osteoarthritis.

DESIGN

PubMed, CINAHL, EMBASE and Cochrane Central Register of Controlled Trials were searched for studies using MSCs for OA treatment (final search December 2017). Outcomes of interest included study evidence level, patient demographics, MSC protocol, treatment results and adverse events. Level I and II evidence articles were further analyzed.

RESULTS

Sixty-one of 3,172 articles were identified. These studies treated 2,390 patients with osteoarthritis. Most used adipose-derived stem cells (ADSCs) (n = 29) or bone marrow-derived stem cells (BMSCs) (n = 30) though the preparation varied within group. 57% of the sixty-one studies were level IV evidence, leaving five level I and nine level II studies containing 288 patients to be further analyzed. Eight studies used BMSCs, five ADSCs and one peripheral blood stem cells (PBSCs). The risk of bias in these studies showed five level I studies at low risk with seven level II at moderate and two at high risk.

CONCLUSION

While studies support the notion that MSC therapy has a positive effect on OA patients, there is limited high quality evidence and long-term follow-up. The present study summarizes the specifics of high level evidence studies and identifies a lack of consistency, including a diversity of MSC preparations, and thus a lack of reproducibility amongst these articles' methods.

Sheep as a model for evaluating mesenchymal stem/stromal cell (MSC)-based chondral defect repair

Osteoarthritis results from the degradation of articular cartilage and is one of the leading global causes of pain and immobility. Cartilage has a limited capacity for self-repair. While repair can be enhanced through surgical intervention, current methods often generate inferior fibrocartilage and repair is transient. The development of tissue engineering strategies to improve repair outcomes is an active area of research. While small animal models such as rodents and rabbits are often used in early pre-clinical work, larger animals that better recapitulate the anatomy and loading of the human joint are required for late-stage preclinical evaluation. Because of their physiological similarities to humans, and low cost relative to other large animals, sheep are routinely used in orthopedic research, including cartilage repair studies. In recent years, there has been considerable research investment into the development of cartilage repair strategies that utilize mesenchymal stem/stromal cells (MSC). In contrast to autologous chondrocytes derived from biopsies of articular cartilage, MSC offer some benefits including greater expansion capacity and elimination of the risk of morbidity at the cartilage biopsy site. The disadvantages of MSC are related to the challenges of inducing and maintaining a stable chondrocyte-like cell population capable of generating hyaline cartilage. Ovine MSC (oMSC) biology and their utility in sheep cartilage repair models have not been reviewed. Herein, we review the biological properties of MSC derived from sheep tissues, and the use of these cells to study articular cartilage repair in this large animal model.

"Patient reported outcomes" following experimental surgery-using telemetry to assess movement in experimental ovine models

Many potential treatments for orthopedic disease fail at the animal to human translational hurdle. One reason for this failure is that the majority of pre-clinical outcome measurements emphasize structural changes, such as gross morphology and histology, and do not address pain or its alleviation, which is a key component of treatment success in man. With increasing emphasis on "patient reported outcome measurements (PROM)" in clinical practice, in this study we have used two different telemetric methods (geolocation and Fitbark activity trackers, Kansas City, MO) to measure movement behavior, i.e., an indirect PROM, in an ovine osteoarthritis induction and an osteochondral defect model performed in adult female Welsh Mountain sheep. This study demonstrates that both systems can be used to track movement and activity of experimental sheep before and after surgery and that the Geolocator system recorded a decrease in distance moved and activity at the end of the experimental period in both models. The Fitbark activity tracker also recorded significant alterations in movement behavior at the end of these studies and this method of recording showed a correlation between Fitbark data and radiography, macroscopic and histological scoring (well recognized outcome measurements), particularly in animals with large (10 mm) defects, i.e., more severe pathology. These results suggest that telemetry is able to track movement behavior in experimental sheep and that the methodology should be considered for inclusion in outcome measures in preclinical orthopedic research. © 2017 The Authors. Journal of Orthopaedic Research® Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 36:1498-1507, 2018.

Peripheral mononuclear blood cell apheresis in a preclinical ovine model

Background

Recent research has demonstrated that circulating peripheral blood mononuclear fractions (PBMC) containing haematopoietic stem (HSC)/progenitor cells have the potential to play a crucial role in regenerative medicine strategies. Work in our laboratory has shown that a peripheral blood mononuclear cell fraction (PBMC) enhances cartilage repair in an osteochondral defect model in sheep and has a significant effect on cells in the joint niche. In order to obtain PBMC rich blood containing HSCs for further studies, we have performed, for the first time, apheresis on adult sheep.

Results

Subcutaneous granulocyte-colony stimulating factor (G-CSF) was used to mobilise white blood cells and continual flow apheresis was performed on 8 sheep under general anaesthetic. There were no observable side effects, although a marked tendency for blood clotting during the procedure was noted. The administration of G-CSF for 3 days increased the white blood cell (WBC) count in the peripheral blood from to 6.7 ± 2.1 × 10⁶/ml to 16.1 ± 5.0 × 10⁶/ml. Following apheresis, the WBC numbers in the apheretic product increased to 38.5 ± 27.6 × 10⁶/ml, comprised of a significant increase in neutrophils and PBMC (from 5.25 ± 1.8 × 10⁶/ml following G-CSF stimulation to 27.5 5 ± 27.6 × 10⁶/ml). There was a mean of 2.1% CD34 + ve cells and 95.5% CD45 + ve cells in the apheretic product.

Conclusions

This study describes the administration of G-CSF and subsequent apheresis in adult sheep. The technique is safe when performed as described with no observable side effects. The technique permits collection of an increased WBC fraction containing neutrophils and PBMC in adult sheep. This apheretic product contains CD34 + ve cells, representing an HSC/progenitor population for use in in vivo and in vitro experiments.

Stem Cells for Cartilage Repair: Preclinical Studies and Insights in Translational Animal Models and Outcome Measures

Due to the restricted intrinsic capacity of resident chondrocytes to regenerate the lost cartilage postinjury, stem cell-based therapies have been proposed as a novel therapeutic approach for cartilage repair. Moreover, stem cell-based therapies using mesenchymal stem cells (MSCs) or induced pluripotent stem cells (iPSCs) have been used successfully in preclinical and clinical settings. Despite these promising reports, the exact mechanisms underlying stem cell-mediated cartilage repair remain uncertain. Stem cells can contribute to cartilage repair via chondrogenic differentiation, via immunomodulation, or by the production of paracrine factors and extracellular vesicles. But before novel cell-based therapies for cartilage repair can be introduced into the clinic, rigorous testing in preclinical animal models is required. Preclinical models used in regenerative cartilage studies include murine, lapine, caprine, ovine, porcine, canine, and equine models, each associated with its specific advantages and limitations. This review presents a summary of recent in vitro data and from in vivo preclinical studies justifying the use of MSCs and iPSCs in cartilage tissue engineering. Moreover, the advantages and disadvantages of utilizing small and large animals will be discussed, while also describing suitable outcome measures for evaluating cartilage repair.

Large Animal Models for Osteochondral Regeneration

Namely, in the last two decades, large animal models - small ruminants (sheep and goats), pigs, dogs and horses - have been used to study the physiopathology and to develop new therapeutic procedures to treat human clinical osteoarthritis. For that purpose, cartilage and/or osteochondral defects are generally performed in the stifle joint of selected large animal models at the condylar and trochlear femoral areas where spontaneous regeneration should be excluded. Experimental animal care and protection legislation and guideline documents of the US Food and Drug Administration, the American Society for Testing and Materials and the International Cartilage Repair Society should be followed, and also the specificities of the animal species used for these studies must be taken into account, such as the cartilage thickness of the selected defect localization, the defined cartilage critical size defect and the joint anatomy in view of the post-operative techniques to be performed to evaluate the chondral/osteochondral repair. In particular, in the articular cartilage regeneration and repair studies with animal models, the subchondral bone plate should always be taken into consideration. Pilot studies for chondral and osteochondral bone tissue engineering could apply short observational periods for evaluation of the cartilage regeneration up to 12 weeks post-operatively, but generally a 6- to 12-month follow-up period is used for these types of studies.

The secreted protein WNT5A regulates condylar chondrocyte proliferation, hypertrophy and migration

OBJECTIVE

Our previous study showed that WNT5A, a member of the noncanonical WNT pathway, is involved in interleukin-1beta induced matrix metalloproteinase expression in temporomandibular joint (TMJ) condylar chondrocytes. The purpose of this study is to further explore the roles of WNT5A in cartilage biology of the TMJ.

METHODS

An early TMJ osteoarthritis-like rat model was constructed by a mechanical method (steady mouth-opening). The gene and protein levels of WNT5A during the condylar cartilage changes were measured. Effects of WNT5A on chondrocyte proliferation, hypertrophy and migration were analyzed after WNT5A gain or loss of function in vitro. A c-Jun N-terminal kinase (JNK) inhibitor SP600125 was used to evaluate the involvement of JNK pathway in these effects of WNT5A. The expression and transcription activity of cell cycle regulators c-MYC and Cyclin D1 were examined to determine the mechanism behind WNT5A regulation of chondrocyte proliferation.

RESULTS

WNT5A was significantly upregulated in the condylar cartilage of rats in the early TMJ osteoarthritis-like model. Activating WNT5A facilitated condylar chondrocyte proliferation, hypertrophy and migration. Conversely, inhibiting WNT5A activity in chondrocytes decreased their proliferation, hypertrophy and migration. Blockage of the JNK pathway by its inhibitor, SP600125, impaired these effects of WNT5A on chondrocytes. WNT5A regulated both the expression and transcriptional activity of c-MYC and Cyclin D1 in chondrocytes, both of which were upregulated in condylar cartilage of the rat early TMJ osteoarthritis.

CONCLUSION

WNT5A regulates condylar chondrocyte proliferation, hypertrophy and migration. These findings provide new insights into the role of WNT5A signaling in TMJ cartilage biology and its potential in future therapy for TMJ degenerative diseases.

Programmable cells of monocytic origin as a source of osteochondroprogenitors: Effect of growth factors on osteogenic differentiation

We have demonstrated previously that peripheral blood monocytes can be converted in vitro to a multipotent stem cell-like cell termed programmable cell of monocytic origin (PCMO) and subsequently into cells with chondrocyte-like phenotype. Here, we investigated whether PCMO could also be differentiated into osteoblast-like cells using growth factors with known osteoinductive potency. Following stimulation with BMP-2, BMP-7, IGF-1 or TGF-β1 for 7 and 14 days, PCMOs were analyzed for mRNA expression of collagen types I and V, alkaline phosphatase, osteocalcin, runt-related transcription factor-2 (Runx2) and Osterix (Osx) by quantitative RT-PCR (qPCR) and the levels of collagen I in culture supernatants by ELISA. The expression of osteoblastic markers was evident, albeit at a different extent in cultures of PCMOs after treatment with the above-mentioned growth factors. Culture supernatants from PCMOs stimulated for 6-10 days with BMP-2, BMP-7, IGF-1 or TGF-β1 contained high levels of collagen type I, together with earlier data indicating synthesis and proper secretion. The findings suggest that PCMOs can transform into cells that are phenotypically similar to osteoblasts and identify these cells as osteochondroprogenitors. The possibility of differentiating PCMOs from peripheral blood in sizable quantities could be a novel way to obtain autologous bone-like substitutes without donor-site morbidity.

Chondrogenic Potential of Peripheral Blood Derived Mesenchymal Stem Cells Seeded on Demineralized Cancellous Bone Scaffolds

As a cell source with large quantity and easy access, peripheral blood mesenchymal stem cells (PBMSCs) were isolated and seeded in porcine demineralized cancellous bone (DCB) scaffolds, cultured in chondrogenic medium and evaluated for in vitro chondrogenesis. Bone marrow MSCs (BMMSCs) and articular cartilage chondrocytes (ACCs) underwent the same process as controls. The morphology, viability and proliferation of PBMSCs in DCB scaffolds were similar to those of BMMSCs and ACCs. PBMSCs and BMMSCs showed similar chondrogenesis potential with consistent production of COL 2 and SOX 9 protein and increased COL 2 and AGC mRNA expressions at week 3 but the COL 2 protein production was still less than that of ACCs. Minimal increase of hypertrophic markers was found in all groups. Relatively higher ALP and lower COL 10 mRNA expressions were found in both MSCs groups at week 3 than that in ACCs, whereas no significant difference of COL 1 and SOX 9 mRNA and MMP 13 protein was found among all groups. To conclude, PBMSCs shared similar proliferation and chondrogenic potential with BMMSCs in DCB scaffolds and could be an alternative to BMMSCs for cartilage tissue engineering. Further optimization of chondrogenesis system is needed regardless of the promising results.

Combining a novel leucocyte-platelet-concentrated membrane and an injectable collagen scaffold in a single-step AMIC procedure to treat chondral lesions of the knee: a preliminary retrospective study

BACKGROUND

Different surgical approaches are currently available to treat knee chondral defects. Microfracture is the most commonly applied, but it often leads to a mechanically inferior fibrocartilaginous tissue. To overcome this shortcoming, the Autologous, Matrix-Induced Chondrogenesis (AMIC) technique has been proposed. To further enhance the outcome of AMIC, the addition of haemoderivatives containing growth factors that stimulate cartilage healing has emerged as a new treatment method. Recently, a novel leucocyte-platelet-concentrated membrane (CLP-MB), highly enriched in platelets, monocytes/macrophages, fibrinogen, CD34⁺ and CD34⁺VEGFR-2⁺CD133⁺ cells, has been developed. Additionally, an injectable collagen scaffold (Cartifill) has been proposed as a replacement of the AMIC standard collagen membrane.

AIMS

This preliminary study is aimed to evaluate the short-term safety and efficacy of the use of the CLP-MB membrane and injectable collagen scaffold when combined in single-step AMIC procedures for the treatment of knee chondral lesions.

METHODS

Medical records of patients who underwent an AMIC procedure with the CLP-MB membrane combined with Cartifill were reviewed retrospectively. Follow-up assessments were conducted at 6 and 12 months after surgery. Clinical function was assessed on the basis of the International Knee Documentation Committee (IKDC) score. Pain was evaluated using the visual analogue scale (VAS).

RESULTS

Twenty-five patients were identified as meeting the inclusion criteria. Mean IKDC and VAS scores significantly improved during the follow-up time. The postoperative course was uneventful.

CONCLUSIONS

AMIC combined with the CLP-MB membrane, and Cartifill seems to be a promising approach to treat knee chondral defects.

Genetic Modification of Human Peripheral Blood Aspirates Using Recombinant Adeno-Associated Viral Vectors for Articular Cartilage Repair with a Focus on Chondrogenic Transforming Growth Factor-β Gene Delivery

Transplantation of genetically modified peripheral blood aspirates that carry chondrogenically competent progenitor cells may offer new, convenient tools to treat articular cartilage lesions compared with the more complex and invasive application of bone marrow concentrates or of bone marrow‐derived mesenchymal stem cells. Here, we show that recombinant adeno‐associated viral (rAAV) vectors are powerful gene vehicles capable of successfully targeting primary human peripheral blood aspirates in a stable and safe manner, allowing for an efficient and long‐term transgene expression in such samples (up to 63 days with use of a lacZ reporter gene and for at least 21 days with application of the pleiotropic, chondrogenic factor transforming growth factor‐β [TGF‐β]). rAAV‐mediated overexpression of TGF‐β enhanced both the proliferative and metabolic properties of the peripheral blood aspirates, also increasing the chondrogenic differentiation processes in these samples. Hypertrophy and osteogenic differentiation events were also activated by production of TGF‐β via rAAV, suggesting that translation of the current approach in vivo will probably require close regulation of expression of this candidate gene. However, these results support the concept of directly modifying peripheral blood as a novel approach to conveniently treat articular cartilage lesions in patients. Stem Cells Translational Medicine2017;6:249–260

Adult Human Peripheral Blood Mononuclear Cells Are Capable of Producing Neurocyte or Photoreceptor-Like Cells That Survive in Mouse Eyes After Preinduction With Neonatal Retina

: Adult human peripheral blood mononuclear cells (hPBMCs) exhibit pluripotency in vitro and so may be a valuable cell source for regenerative therapies. The efficacy of such therapies depends on the survival, differentiation, migration, and integration capacity of hPBMCs in specific tissues. In this study, we examined these capacities of transplanted hPBMCs in mouse retina as well functional improvement after transplant. We isolated hPBMCs and preinduced them for 4 days in media preconditioned with postnatal day 1 rat retina explants. Preinduction increased the proportions of hPBMCs expressing neural stem cell, neural progenitor cell, or photoreceptor markers as revealed by immunofluorescent staining, flow cytometry, and quantitative real-time polymerase chain reaction. Preinduced hPBMCs were transplanted into the subretinal space of retinal degenerative slow (RDS) and retinal degeneration 1 (RD1) mice. At 1, 3, and 6 months after transplantation, treated eyes of RDS mice were collected and cell phenotype was studied by immunofluorescent staining. Preinduced hPBMCs survived in the subretinal space; migrated away from the injection site and into multiple retinal layers; and expressed neural stem cell, neuronal, and photoreceptor markers. Finally, we assessed RD1 retinal function after subretinal transplantation and found significant improvement at 3 months after transplantation. The ease of harvesting, viability in vivo, capacity to express neuronal and photoreceptor proteins, and capacity for functional enhancement suggest that hPBMCs are potential candidates for cell replacement therapy to treat retinal degenerative diseases.

SIGNIFICANCE

This study provides support for the use of peripheral blood mononuclear cells (PBMCs) as a potential source of pluripotent stem cells for treating retinal degeneration. First, this study demonstrated that PBMCs can differentiate into retinal neuron-like cells in vitro and in vivo. Second, some transplanted cells expressed markers for neural progenitors, mature neurons, or photoreceptors at 1, 3, and 6 months after subretinal injection. Finally, this study showed that PBMC transplantation can improve the function of a degenerated retina.

Cartilage defect repair in horses: Current strategies and recent developments in regenerative medicine of the equine joint with emphasis on the surgical approach

Chondral and osteochondral lesions due to injury or other pathology are highly prevalent conditions in horses (and humans) and commonly result in the development of osteoarthritis and progression of joint deterioration. Regenerative medicine of articular cartilage is an emerging clinical treatment option for patients with articular cartilage injury or disease. Functional articular cartilage restoration, however, remains a major challenge, but the field is progressing rapidly and there is an increasing body of supportive clinical and scientific evidence. This review gives an overview of the established and emerging surgical techniques employed for cartilage repair in horses. Through a growing insight in surgical cartilage repair possibilities, surgeons might be more stimulated to explore novel techniques in a clinical setting.

Cartilage repair techniques in the knee: stem cell therapies

Among the surgical options for large full-thickness chondral injuries, cell-based therapy has been practiced and its satisfactory outcomes have been reported. One area that appears promising is cell-based therapies utilizing stem cells. Various tissues within the human body contain mesenchymal stem cells (MSCs) from where these can be harvested. These include bone marrow, adipose, synovium, peripheral blood, and umbilical cord. In this article, both preclinical animal studies and clinical studies dealing with the use of MSCs for cartilage repair of the knee are reviewed. Majority of the clinical papers have shown promising results; however, there are a limited number of studies of high evidence level. Clinical significance of the stem cell therapy as compared to other surgical options as well as optimization of the procedure in terms of cell type and delivery method is still to be determined.