One-step surgical procedure for the treatment of osteochondral defects with adipose-derived stem cells in a caprine knee defect: a pilot study

Impact of Different Cell Types on the Osteogenic Differentiation Process of Mesenchymal Stem Cells

The skeleton is an important organ in the human body. Bone defects caused by trauma, inflammation, tumors, and other reasons can impact the quality of life of patients. Although the skeleton has a certain ability to repair itself, the current most effective method is still autologous bone transplantation due to factors such as blood supply and defect size. Modern medicine is attempting to overcome these limitations through cell therapy, with mesenchymal stem cells (MSCs) playing a crucial role. MSCs can be extracted from different tissues, and their differentiation potential varies depending on the source. Various cells and cell secretions can influence this process. This article, based on previous research, reviews the effects of macrophages, endothelial cells (ECs), nerve cells, periodontal cells, and even some bacteria on MSC osteogenic differentiation, aiming to provide a reference for multicell coculture strategies related to osteogenesis.

State of the Art in the Standardization of Stromal Vascular Fraction Processing

Stromal Vascular Fraction (SVF) has gained significant attention in clinical applications due to its regenerative and anti-inflammatory properties. Initially identified decades ago, SVF is derived from adipose tissue and has been increasingly utilized in a variety of therapeutic settings. The isolation and processing protocols for SVF have evolved substantially, particularly after its classification as an Advanced Therapy Medicinal Product (ATMP), which mandates adherence to Good Manufacturing Practices to ensure sterility and product quality. Despite the progress, few studies over the last decade have focused on the standardization of SVF processing. Recent advances, driven by the potential of SVF and its derived products such as Adipose-derived Stem Cells, have prompted the development of improved isolation strategies aimed at enhancing their therapeutic and regenerative efficacy. Notable progress includes the advent of automated processing systems, which reduce technical errors, minimize variability, and improve reproducibility across laboratories. These developments, along with the establishment of more precise protocols and guidelines, have enhanced the consistency and clinical applicability of SVF-based therapies. This review discusses the key aspects of SVF isolation and processing, highlighting the efforts to standardize the procedure and ensure the reliability of SVF products for clinical use.

Forty Years of the Use of Cells for Cartilage Regeneration: The Research Side

Background: The treatment of articular cartilage damage has always represented a problem of considerable practical interest for orthopedics. Over the years, many surgical techniques have been proposed to induce the growth of repairing tissue and limit degeneration. In 1994, the turning point occurred: implanted autologous cells paved the way for a new treatment option based more on regeneration than repair. Objectives: This review aims to outline biological and clinical advances, from the use of mature adult chondrocytes to cell-derived products, going through progenitor cells derived from bone marrow or adipose tissue and their concentrates for articular cartilage repair. Moreover, it highlights the relevance of gene therapy as a valuable tool for successfully implementing current regenerative treatments, and overcoming the limitations of the local delivery of growth factors. Conclusions: Finally, this review concludes with an outlook on the importance of understanding the role and mechanisms of action of the different cell compounds with a view to implementing personalized treatments.

A mathematical model of signalling molecule-mediated processes during regeneration of osteochondral defects after chondrocyte implantation

Treating bone-cartilage defects is a fundamental clinical problem. The ability of damaged cartilage to self-repair is limited due to its avascularity. Left untreated, these defects can lead to osteoarthritis. Details of osteochondral defect repair are elusive, but animal models indicate healing occurs via an endochondral ossification-like process, similar to that in the growth plate. In the growth plate, the signalling molecules parathyroid hormone-related protein (PTHrP) and Indian Hedgehog (Ihh) form a feedback loop regulating chondrocyte hypertrophy, with Ihh inducing and PTHrP suppressing hypertrophy. To better understand this repair process and to explore the regulatory role of signalling molecules on the regeneration process, we formulate a reaction-diffusion mathematical model of osteochondral defect regeneration after chondrocyte implantation. The drivers of healing are assumed to be chondrocytes and osteoblasts, and their interaction via signalling molecules. We model cell proliferation, migration and chondrocyte hypertrophy, and matrix production and conversion, spatially and temporally. We further model nutrient and signalling molecule diffusion and their interaction with the cells. We consider the PTHrP-Ihh feedback loop as the backbone mechanisms but the model is flexible to incorporate extra signalling mechanisms if needed. Our mathematical model is able to represent repair of osteochondral defects, starting with cartilage formation throughout the defect. This is followed by chondrocyte hypertrophy, matrix calcification and bone formation deep inside the defect, while cartilage at the surface is maintained and eventually separated from the deeper bone by a thin layer of calcified cartilage. The complete process requires around 48 months. A key highlight of the model demonstrates that the PTHrP-Ihh loop alone is insufficient and an extra mechanism is required to initiate chondrocyte hypertrophy, represented by a critical cartilage density. A parameter sensitivity study reveals that the timing of the repair process crucially depends on parameters, such as the critical cartilage density, and those describing the actions of PTHrP to suppress hypertrophy, such as its diffusion coefficient, threshold concentration and degradation rate.

Understanding and controlling the variables for stromal vascular fraction therapy

In regenerative medicine, the isolation of mesenchymal stromal cells (MSCs) from the adipose tissue's stromal vascular fraction (SVF) is a critical area of study. Our review meticulously examines the isolation process of MSCs, starting with the extraction of adipose tissue. The choice of liposuction technique, anatomical site, and immediate processing are essential to maintain cell functionality. We delve into the intricacies of enzymatic digestion, emphasizing the fine-tuning of enzyme concentrations to maximize cell yield while preventing harm. The review then outlines the filtration and centrifugation techniques necessary for isolating a purified SVF, alongside cell viability assessments like flow cytometry, which are vital for confirming the efficacy of the isolated MSCs. We discuss the advantages and drawbacks of using autologous vs allogeneic SVF sources, touching upon immunocompatibility and logistical considerations, as well as the variability inherent in donor-derived cells. Anesthesia choices, the selection between hypodermic needles vs liposuction cannulas, and the role of adipose tissue lysers in achieving cellular dissociation are evaluated for their impact on SVF isolation. Centrifugation protocols are also analyzed for their part in ensuring the integrity of the SVF. The necessity for standardized MSC isolation protocols is highlighted, promoting reproducibility and successful clinical application. We encourage ongoing research to deepen the understanding of MSC biology and therapeutic action, aiming to further the field of regenerative medicine. The review concludes with a call for rigorous research, interdisciplinary collaboration, and strict adherence to ethical and regulatory standards to safeguard patient safety and optimize treatment outcomes with MSCs.

Efficacy of the immediate adipose-derived stromal vascular fraction autograft on functional sensorimotor recovery after spinal cord contusion in rats

BACKGROUND

Spinal cord injuries (SCI) lead to functional alteration with important consequences such as motor and sensory disorders. The repair strategies developed to date remain ineffective. The adipose tissue-derived stromal vascular fraction (SVF) is composed of a cocktail of cells with trophic, pro-angiogenic and immunomodulatory effects. Numerous therapeutic benefits were shown for tissue reconstitution, peripheral neuropathy and for the improvement of neurodegenerative diseases. Here, the therapeutic efficacy of SVF on sensorimotor recovery after an acute thoracic spinal cord contusion in adult rats was determined.

METHOD

Male Sprague Dawley rats (n = 45) were divided into 3 groups: SHAM (without SCI and treatment), NaCl (animals with a spinal lesion and receiving a saline injection through the dura mater) and SVF (animals with a spinal lesion and receiving a fraction of fat removed from adipocytes through the dura mater). Some animals were sacrificed 14 days after the start of the experiment to determine the inflammatory reaction by measuring the interleukin-1β, interleukin-6 and Tumor Necrosis Factor-α in the lesion area. Other animals were followed once a week for 12 weeks to assess functional recovery (postural and locomotor activities, sensorimotor coordination). At the end of this period, spinal reflexivity (rate-dependent depression of the H-reflex) and physiological adjustments (ventilatory response to metabosensitive muscle activation following muscle fatigue) were measured with electrophysiological tools.

RESULTS

Compared to non-treated animals, results indicated that the SVF reduced the endogenous inflammation and increased the behavioral recovery in treated animals. Moreover, H-reflex depression and ventilatory adjustments to muscle fatigue were found to be comparable between SHAM and SVF groups.

CONCLUSION

Our results highlight the effectiveness of SVF and its high therapeutic potential to improve sensorimotor functions and to restore the segmental sensorimotor loop and the communication between supra- and sub-lesional spinal cord regions after traumatic contusion.

Efficacy of fractional CO2 laser in combination with stromal vascular fraction (SVF) compared with fractional CO2 laser alone in the treatment of burn scars: a randomized controlled clinical trial

BACKGROUND

The appearance of skin scars is known as one of the main side effects of skin burns. Stromal vascular fraction (SVF), as a rich source of cell populations with tissue regeneration properties, plays an important role in the healing of skin lesions. Fractional CO2 lasers have occupied a special place in treating skin lesions, particularly skin scars, since their introduction. Our study aimed to compare the combination of SVF and fractional CO2 laser with fractional CO2 laser alone in the treatment of burn scars.

METHOD

This double-blind clinical trial study was conducted on ten patients with burn scars that were treated three times with a fractional CO2 laser at site of burn lesions, and one of the two areas studied was randomly injected with SVF. Two months after completion of the procedure, patients' scars were assessed using the Vancouver scar scale (VSS), biometric criteria, and physician and patient satisfaction ratings.

RESULTS

The results confirmed a significant improvement in VSS, cutometry, R7 criteria, complete density sonography, and skin density sonography in the fractional CO2 laser-treated group. The VSS criteria, epidermal thickness sonography, complete density sonography, and skin density sonography in the group treated with the combination of fractional CO2 laser and SVF also showed significant improvement. The VSS criteria and melanin index of Mexameter in the group treated with SVF in combination with fractional CO2 laser were significantly better than the group treated with fractional CO2 laser alone. Also, physician and patient satisfaction in the group treated with SVF injection in combination with fractional CO2 laser was significantly higher than the other group.

CONCLUSION

The results confirm the efficacy of SVF injection in combination with fractional CO2 laser in the treatment of burn scars and can be considered as a treatment option for better management of these lesions.

TRIAL REGISTRATION

The study protocol was retrospectively registered at Iranian Registry of Clinical Trials with code: IRCT20210515051307N1, Registration date: 2021-11-14, URL: https://www.irct.ir/trial/56337 .

The Use of Stromal Vascular Fraction in Long Bone Defect Healing in Sheep

The objectives of the present study were to evaluate (a) the feasibility of using stromal vascular fraction (SVF) and nanocrystalline hydroxyapatite (nHA) paste in combination for the treatment of segmental bone defect, (b) the quality of the callus produced, (c) the potential improvement of the autograft technique, and (d) the direct comparison of the biomaterial to the use of autogenous cancellous bone. Unilateral, segmental mid-diaphyseal bone defect was created on the right metatarsus of skeletally mature sheep animals (n = 24) under anesthesia (D0). Residual segments were stabilized by stainless-steel plates and appropriate screws. Defects were managed as follows: group A: use of nHA paste to filling, group B: use of autogenous bone graft mixed with nHA bone paste, placed in defect, group C: use of SVF mixed with nHA bone paste injected into defect, group D: use of bone graft and SVF with nHA paste before apposition in bone defect. SVF had been previously isolated from adipose tissue of the animals intra-operatively after digestion with collagenase solution and neutralization. Animals were evaluated clinically and by X-raying and ultrasonographic examination of the defect, at regular intervals, until D90. Ultrasonographic assessment performed along the length of the defect included calculation of the length of the bone defect and assessment of vascularization. SVF was successfully isolated from group C and D animals, with the average yield being 1.77 × 106 cells. The comparison of clinical scores (based on the 'Kaler scale') on each post-operative day indicated significant differences between the four groups on D1 to D30 (p < 0.01); the median clinical score within group A was 2.5 for D1-D30 and 1 for the entire period; respective scores for other groups were 1.5 (p = 0.07) and 0 (p = 0.033). Differences in radiographic assessment scores were significant for scores obtained on D60 (p = 0.049) and D90 (p = 0.006). There was a significant difference between the four groups in the length of the bone defect, as assessed ultrasonographically, for the entire length of the study; median values were 8, 8.5, 6, and 8 mm for groups A, B, C, and D, respectively (p = 0.008). There was a significance in the differences between median scores obtained during the histopathological examination: 2, 11, 13.5, and 12 for group A, B, C, and D (p = 0.022). There was an inverse correlation between the overall scores of histopathological evaluations and the length of the bone defect (observed on D90) (p < 0.0001) and a correlation between the overall scores and the radiographic assessment scores (obtained on D90) (p < 0.0001). This is the first study in which the efficacy of fresh autologous Stromal Vascular Fraction (SVF) from adipose tissue in enhancing bone healing in a long, weight-bearing, diaphyseal bone was evaluated. It is concluded that the lumbosacral region was an attractive site for harvesting adipose tissue, the use of SVF contributed to faster rehabilitation post-operatively, and SVF significantly enhanced bone formation; in general, the results indicated an osteogenic potential of SVF comparable to the gold standard autologous bone graft.

Adipose-Derived Mesenchymal Stromal Cells: A Tool for Bone and Cartilage Repair

The osteogenic and chondrogenic differentiation ability of adipose-derived mesenchymal stromal cells (ASCs) and their potential therapeutic applications in bone and cartilage defects are reported in this review. This becomes particularly important when these disorders can only be poorly treated by conventional therapeutic approaches, and tissue engineering may represent a valuable alternative. Being of mesodermal origin, ASCs can be easily induced to differentiate into chondrocyte-like and osteocyte-like elements and used to repair damaged tissues. Moreover, they can be easily harvested and used for autologous implantation. A plethora of ASC-based strategies are being developed worldwide: they include the transplantation of freshly harvested cells, in vitro expanded cells or predifferentiated cells. Moreover, improving their positive effects, ASCs can be implanted in combination with several types of scaffolds that ensure the correct cell positioning; support cell viability, proliferation and migration; and may contribute to their osteogenic or chondrogenic differentiation. Examples of these strategies are described here, showing the enormous therapeutic potential of ASCs in this field. For safety and regulatory issues, most investigations are still at the experimental stage and carried out in vitro and in animal models. Clinical applications have, however, been reported with promising results and no serious adverse effects.

Evaluation of a co-culture of rapidly isolated chondrocytes and stem cells seeded on tri-layered collagen-based scaffolds in a caprine osteochondral defect model

Cartilage has poor regenerative capacity and thus damage to the joint surfaces presents a major clinical challenge. Recent research has focussed on the development of tissue-engineered and cell-based approaches for the treatment of cartilage and osteochondral injuries, with current clinically available cell-based approaches including autologous chondrocyte implantation and matrix-assisted autologous chondrocyte implantation. However, these approaches have significant disadvantages due to the requirement for a two-stage surgical procedure and an in vitro chondrocyte expansion phase which increases logistical challenges, hospital times and costs. In this study, we hypothesized that seeding biomimetic tri-layered scaffolds, with proven regenerative potential, with chondrocyte/infrapatellar fat pad stromal cell co-cultures would improve their regenerative capacity compared to scaffolds implanted cell-free. Rapid cell isolation techniques, without the requirement for long term in vitro culture, were utilised to achieve co-cultures of chondrocytes and stromal cells and thus overcome the limitations of existing cell-based techniques. Cell-free and cell-seeded scaffolds were implanted in osteochondral defects, created within the femoral condyle and trochlear ridge, in a translational large animal goat model. While analysis showed trends towards delayed subchondral bone healing in the cell-seeded scaffold group, by the 12 month timepoint the cell-free and cell-seeded groups yield cartilage and bone tissue with comparable quality and quantity. The results of the study reinforce the potential of the biomimetic tri-layered scaffold to repair joint defects but failed to demonstrate a clear benefit from the addition of the CC/FPMSC co-culture to this scaffold. Taking into consideration the additional cost and complexity associated with the cell-seeded scaffold approach, this study demonstrates that the treatment of osteochondral defects using cell-free tri-layered scaffolds may represent a more prudent clinical approach.

Suburethral implantation of autologous regenerative cells for female stress urinary incontinence management: Results of a pilot study

OBJECTIVES

To assess the feasibility and the safety of treating female stress urinary incontinence (SUI) with suburethral implantation of a mixture of the stromal vascular fraction from adipose tissue and leukocyte-and platelet-rich-fibrin.

METHODS

Patients with SUI were treated with a mixture of stromal vascular fraction and leukocyte-and platelet-rich fibrin. The stromal vascular fraction was obtained from enzymatic digestion of autologous adipose-tissue and added to an leukocyte-and platelet-rich-fibrin membrane. The mixture was transvaginally implanted into the suburethral area. A fraction of the Stromal vascular fraction sample was used for cellular characterization. Patients were followed for 9 months. Every 3 months, the patients were clinically evaluated with a cough- stress test and a validated-questionnaire. An MRI was performed preoperatively and 3 months after the procedure to assess tissue changes.

RESULTS

Ten patients received the surgical procedure. The validated-questionnaire revealed a subjective SUI improvement in nine patients 3 months after the operation and in seven patients 9 months after the operation. Eight, six, and four patients achieved a negative cough-stress test 3, 6 and 9 months post-injection, respectively. Flow cytometric analysis of stromal vascular fraction cell phenotypes revealed predominantly mesenchymal and endothelial cell heterogeneity. In total, we injected 0,18 × 10⁶ to 13,6 × 10⁶ cells. No adverse events were observed peri- or postoperatively.

CONCLUSION

These preliminary results suggest that the suburethral implantation of a combination of SVF and l-PRF is a feasible and safe modality for treating female SUI. However, evidence is lacking and further research are needed to clarify the respective roles of SVF and l-PRF in female SUI treatment.

Clinical Safety and Effectiveness of Adipose-Derived Stromal Cell vs Stromal Vascular Fraction Injection for Treatment of Knee Osteoarthritis: 2-Year Results of Parallel Single-Arm Trials

BACKGROUND

There are currently no disease-modifying treatments available for knee osteoarthritis (OA), although cultured adipose-derived stromal cells (ASCs) have shown promise in experimental models. However, given the regulatory limits on the use of cultured cells in humans, previous trials have focused primarily on the stromal vascular fraction (SVF) intra-articular injection. Therefore, the therapeutic value of ASCs for knee OA remains unknown.

PURPOSE

To study ASC versus SVF intra-articular injection in patients with Kellgren-Lawrence (KL) knee OA grades 2 to 4 in parallel single-arm trials.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

A total of 80 patients were enrolled, with 42 (72 knees) receiving ASC intra-articular injection and 38 (69 knees) receiving SVF. Patient-reported outcome measures were assessed at 1, 3, 6, 12, and 24 months using the Knee injury and Osteoarthritis Outcome Score 5 (KOOS5) and pain visual analog scale (VAS). The percentages of patients achieving the minimal clinically important difference (MCID) and Patient Acceptable Symptom State (PASS) were also calculated. Per protocol, a subset of the ASC group received an ASC booster injection after 6 months. A repeated-measures analysis of variance compared results between treatment arms and by KL grade over time.

RESULTS

Patient-reported outcome measures improved substantially after both treatments (P < .05 at all time points), with the ASC group more likely to achieve the MCID (50% vs 24%; P = .01) and PASS (45% vs 24%; P = .04) for the pain VAS and the MCID (43% vs 16%; P = .02) for the KOOS5 at 12 months, although not at 24 months. Knees treated with ASC for KL grade 2/3 OA had significantly superior outcomes compared with those with KL grade 4 OA for the KOOS5 (P = .01) and pain VAS (P = .03), but no such difference was observed in knees treated with SVF. Three patients receiving ASCs (7%; all KL grade 3) sought additional nonoperative treatment by 24 months versus 9 patients receiving SVF (24%; all KL grade 3) (P = .06). ASC booster injections conferred no additional benefit. Notably, patients in the ASC cohort reported more injection-site pain and swelling after the booster injection than after the initial injection (P < .01).

CONCLUSION

This represents the first head-to-head comparison of ASCs and SVF for the treatment of knee OA in humans. ASC and SVF injections both substantially improved knee pain and function at all follow-up time points, although ASC injections demonstrated significantly better improvements with regard to the MCID and PASS for the pain VAS and the MCID for the KOOS5 at 12 months. There appears to be no benefit to a booster ASC injection after initial treatment. Given less donor-site morbidity and equivalent superior outcomes at 2 years, the use of ASCs over SVF in the treatment of knee OA may be warranted.

Clinical applications of adipose-derived stromal vascular fraction in veterinary practice

Adipose tissue-derived stromal vascular fraction (AdSVF) comprises a heterogeneous cell population, including the multipotent mesenchymal stem cells, hematopoietic stem cells, immune cells, endothelial cells, fibroblasts, and pericytes. As such, multipotent adipose tissue-derived mesenchymal stem cells (AdMSCs), are one of the important components of AdSVF. Commonly used techniques to harvest AdSVF involve enzymatic or non-enzymatic methods. The enzymatic method is considered to be the gold standard technique due to its higher yield. The cellular components of AdSVF can be resuspended in normal saline, platelet-rich plasma, or phosphate-buffered saline to produce a ready-to-use solution. Freshly isolated AdSVF has exhibited promising osteogenic and vasculogenic capacity. AdSVF has already been proven to possess therapeutic potential for osteoarthritis management. It is also an attractive therapeutic option for enhancing wound healing. In addition, the combined use of AdSVF and platelet-rich plasma has an additive stimulatory effect in accelerating wound healing and can be considered an alternative to AdMSC treatment. It is also widely used for managing various orthopaedic conditions in clinical settings and has the potential for regenerating bone, cartilage, and tendons. Autologous AdSVF cells are used along with bone substitutes and other biological factors as an alternative to conventional bone grafting techniques owing to their promising osteogenic and vasculogenic capacity. It can also be used for treating osteonecrosis, meniscus tear, chondromalacia, and tendon injuries in veterinary practice. It has several advantages over in vitro expanded AdMSC, including precluding the need for culturing, reduced risk of cell contamination, and cost-effectiveness, making it ideal for clinical use.

Layer-specific stem cell differentiation in tri-layered tissue engineering biomaterials: Towards development of a single-stage cell-based approach for osteochondral defect repair

Successful repair of osteochondral defects is challenging, due in part to their complex gradient nature. Tissue engineering approaches have shown promise with the development of layered scaffolds that aim to promote cartilage and bone regeneration within the defect. The clinical potential of implanting these scaffolds cell-free has been demonstrated, whereby cells from the host bone marrow MSCs infiltrate the scaffolds and promote cartilage and bone regeneration within the required regions of the defect. However, seeding the cartilage layer of the scaffold with a chondrogenic cell population prior to implantation may enhance cartilage tissue regeneration, thus enabling the treatment of larger defects. Here the development of a cell seeding approach capable of enhancing articular cartilage repair without the requirement for in vitro expansion of the cell population is explored. The intrinsic ability of a tri-layered scaffold previously developed in our group to direct stem cell differentiation in each layer of the scaffold was first demonstrated. Following this, the optimal chondrogenic cell seeding approach capable of enhancing the regenerative capacity of the tri-layered scaffold was demonstrated with the highest levels of chondrogenesis achieved with a co-culture of rapidly isolated infrapatellar fat pad MSCs (FPMSCs) and chondrocytes (CCs). The addition of FPMSCs to a relatively small number of CCs led to a 7.8-fold increase in the sGAG production over chondrocytes in mono-culture. This cell seeding approach has the potential to be delivered within a single-stage approach, without the requirement for costly in vitro expansion of harvested cells, to achieve rapid repair of osteochondral defects.

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Tri-layered scaffold capable of directing layer specific stem cell differentiation.

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Potential of cell seeding regimes to enhance chondrogenic repair explored.

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Optimal cell seeding regime was an infrapatellar fat pad MSC:chondrocyte coculture.

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Adding infrapatellar fat pad MSCs to chondrocytes led to >7-fold increase in sGAG.

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This cell-seeded scaffold has potential for rapid repair of osteochondral defects.

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.

Translational products of adipose tissue-derived mesenchymal stem cells: Bench to bedside applications

With developments in the field of tissue engineering and regenerative medicine, the use of biological products for the treatment of various disorders has come into the limelight among researchers and clinicians. Among all the available biological tissues, research and exploration of adipose tissue have become more robust. Adipose tissue engineering aims to develop by-products and their substitutes for their regenerative and immunomodulatory potential. The use of biodegradable scaffolds along with adipose tissue products has a major role in cellular growth, proliferation, and differentiation. Adipose tissue, apart from being the powerhouse of energy storage, also functions as the largest endocrine organ, with the release of various adipokines. The progenitor cells among the heterogeneous population in the adipose tissue are of paramount importance as they determine the capacity of regeneration of these tissues. The results of adipose-derived stem-cell assisted fat grafting to provide numerous growth factors and adipokines that improve vasculogenesis, fat graft integration, and survival within the recipient tissue and promote the regeneration of tissue are promising. Adipose tissue gives rise to various by-products upon processing. This article highlights the significance and the usage of various adipose tissue by-products, their individual characteristics, and their clinical applications.

Cross-Talk Between Mesenchymal Stromal Cells (MSCs) and Endothelial Progenitor Cells (EPCs) in Bone Regeneration

Bone regeneration is a complex, well-orchestrated process based on the interactions between osteogenesis and angiogenesis, observed in both physiological and pathological situations. However, specific conditions (e.g., bone regeneration in large quantity, immunocompromised regenerative process) require additional support. Tissue engineering offers novel strategies. Bone regeneration requires a cell source, a matrix, growth factors and mechanical stimulation. Regenerative cells, endowed with proliferation and differentiation capacities, aim to recover, maintain, and improve bone functions. Vascularization is mandatory for bone formation, skeletal development, and different osseointegration processes. The latter delivers nutrients, growth factors, oxygen, minerals, etc. The development of mesenchymal stromal cells (MSCs) and endothelial progenitor cells (EPCs) cocultures has shown synergy between the two cell populations. The phenomena of osteogenesis and angiogenesis are intimately intertwined. Thus, cells of the endothelial line indirectly foster osteogenesis, and conversely, MSCs promote angiogenesis through different interaction mechanisms. In addition, various studies have highlighted the importance of the microenvironment via the release of extracellular vesicles (EVs). These EVs stimulate bone regeneration and angiogenesis. In this review, we describe (1) the phenomenon of bone regeneration by different sources of MSCs. We assess (2) the input of EPCs in coculture in bone regeneration and describe their contribution to the osteogenic potential of MSCs. We discuss (3) the interaction mechanisms between MSCs and EPCs in the context of osteogenesis: direct or indirect contact, production of growth factors, and the importance of the microenvironment via the release of EVs.

Orthobiologics in the treatment of hip disorders

Orthobiologics are biological materials that are intended for the regeneration or healing of bone, cartilage and soft tissues. In this review we discuss the use of orthobiologics for hip disorders providing an update. The orthobiologics included in this article are hyaluronic acid, platelet rich plasma, bone marrow, adipose tissue and expanded mesenchymal stem cells. We explain the concepts and definitions of each orthobiological product, and the literature regarding its use in the hip joint. The paucity of guidelines for the production and characterization of the biological products leads to uneven results across the literature. Each biologic therapy has indications and benefits; however, noteworthy are the characterization of the orthobiologics, the application method and outcome analysis for further improvement of each technique.

In Vivo Cartilage Regeneration with Cell-Seeded Natural Biomaterial Scaffold Implants: 15-Year Study

Articular cartilage can be easily damaged from human's daily activities, leading to inflammation and to osteoarthritis, a situation that can diminish the patients' quality of life. For larger cartilage defects, scaffolds are employed to provide cells the appropriate three-dimensional environment to proliferate and differentiate into healthy cartilage tissue. Natural biomaterials used as scaffolds, attract researchers' interest because of their relative nontoxic nature, their abundance as natural products, their easy combination with other materials, and the relative easiness to establish Marketing Authorization. The last 15 years were chosen to review, document, and elucidate the developments on cell-seeded natural biomaterials for articular cartilage treatment in vivo. The parameters of the experimental designs and their results were all documented and presented. Considerations about the newly formed cartilage and the treatment of cartilage defects were discussed, along with difficulties arising when applying natural materials, research limitations, and tissue engineering approaches for hyaline cartilage regeneration.

Stromal-vascular fraction of adipose tissue as an alternative source of cellular material for regenerative medicine

Adipose tissue is the most convenient source of cellular material for regenerative medicine as it can be obtained in significant quantities via cosmetic liposuction, lipoaspiration of subcutaneous fat or by excision of fat deposits. Adipose tissue consists of adipocytes and cells, which are the part of the stromal-vascular fraction (SVF). Different cell populations can be isolated from SVF, among which the population of adipose tissue stem cells (adipose-derived stem cells, ADSC) is especially important for regenerative medicine. SVF can be obtained relatively easily from adipose tissue (adipose tissue is an alternative to bone marrow in terms of being a source of stem cells) and used to treat various pathologies. Recent studies show that SVF not only has a therapeutic effect similar to that of ADSC, but in some cases is even more effective. The article provides the analysis of the main methods of SVF obtainment, characteristics of SVF cellular composition, its potential for use in clinical medicine and its main advantages over other sources of cellular material, including­ ADSC cultured in vitro, for regenerative medicine. Keywords: adipocytes, adipose-derived stem cells, regenerative medicine, stromal-vascular fraction

Stromal Vascular Fraction and Amniotic Epithelial Cells: Preclinical and Clinical Relevance in Musculoskeletal Regenerative Medicine

Musculoskeletal regenerative medicine is mainly based on the use of cell therapy to heal damaged tissues such as bone, cartilage, and tendons. Throughout the years, different cell types have been employed for the treatment of musculoskeletal diseases, in particular, mesenchymal stem cells (MSCs) derived from bone marrow (BMSCs) and adipose tissue (ADSCs). Though the results of these literature studies have been encouraging, there are some limitations, especially on long-term results. Recently, some interest has shifted towards new cell types such as the stromal vascular fraction (SVF) and amniotic endothelial cells (AECs). The aim of the present literature review is to evaluate preclinical and clinical studies that used SVF and AECs for musculoskeletal tissue regeneration. Forty-eight preclinical and clinical studies, performed in the last 10 years, were identified. Both SVF and AECs, injected or implanted with or without scaffolds, were shown to be valid alternatives, and in some ways superior, to ADSCs and BMSCs, being able to differentiate towards osteogenic, chondrogenic, and tenogenic lineages, and to promote cell and tissue regenerative potential. The use of SVF and AECs could represent a new regenerative treatment in several musculoskeletal pathologies, solving the problem of cell expansion in vitro.

The treatment of articular cartilage injuries with mesenchymal stem cells in different animal species

One of the major problems observed in veterinary practice is articular cartilage injuries in animals. In terms of agriculture, it leads to their culling from the herd, even if they are highly productive animals. With companion animals, owners usually have to decide between euthanasia or long-term sometimes lifelong treatment of the injury by a veterinarian. The use of mesenchymal stem cells (MSCs) for the treatment of cartilage injury in veterinary medicine is based on the good results observed in preclinical studies, where large animals have been used as experimental models to study the regenerative activity of MSCs. According to the literature, MSCs in veterinary medicine have been used to treat cartilage injury of dogs and horses, whereas sheep and goats are generally models for reproducing the disease in preclinical experimental studies.

Potential of Tissue-Engineered and Artificial Dermis Grafts for Fingertip Reconstruction

BACKGROUND

Management of skin and soft-tissue defects of the fingertips is functionally and aesthetically important, but controversial, especially when bones are exposed. Recent advances in wound healing technology allow the use of cells or biological dermis. The authors studied the clinical efficacy of tissue-engineered dermis grafts and artificial dermis grafts versus immediate reconstructive procedures, such as the reverse digital artery island flap, in treating bone-exposed fingertip defects.

METHODS

One hundred eighty-two patients with bone-exposed fingertip defects treated with tissue-engineered dermis grafts (n = 71), artificial dermis grafts (n = 23), or reverse digital artery island flaps (n = 88) were included in this retrospective cohort study. Surgical time, duration of hospitalization, total cost, success rate, healing time, sensory recovery, range of motion, scar quality, and patient satisfaction were compared.

RESULTS

No tissue-engineered or artificial dermis graft exhibited graft rejection or failure, whereas there was one partial loss and one total loss after reverse digital artery island flap surgery. Tissue-engineered dermis grafts were superior in scar quality, and artificial dermis grafts had shorter surgical times and lower surgical costs; both groups demonstrated superior results in postoperative range of motion and sensory recovery in two-point discrimination tests and shorter hospitalization, compared with the reverse digital artery island flap group. The reverse digital artery island flap had shorter complete closure time and less postoperative tingling sensation. There were no differences in overall patient satisfaction among the groups.

CONCLUSIONS

Tissue-engineered and artificial dermis grafts may be promising alternatives for fingertip reconstruction. In particular, tissue-engineered dermis grafts may deliver superior functional results, including recovery of sensory discomfort and aesthetic results in terms of scar quality over artificial dermis grafts.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

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.

Improved outcomes after mesenchymal stem cells injections for knee osteoarthritis: results at 12-months follow-up: a systematic review of the literature

PURPOSE

According to the World Health organization (WHO), more than 10% in people older than 60 years suffer from osteoarthritis (OA). Over the last years, there has been an increased interest around regenerative medicine, especially regarding stem cell treatments and related applications. We hypothesize that stem cell therapies can represent a feasible option for idiopathic knee OA, delaying or even avoiding the joint replacement. To emphasize the potential of percutaneous injections of mesenchymal stem cells for knee OA, a comprehensive systematic review of the literature was conducted.

MATERIAL AND METHODS

Two independent authors (FM, GC) performed the literature search. This study was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines (PRISMA). The main databases were accessed: Pubmed, Embase, Google Scholar, Cochrane Systematic Reviews, Scopus, AMED. For this systematic review, all articles treating percutaneous injections of mesenchymal stem cells for knee OA were considered. Because of the rapid advancements promoted by the scientific progress on stem cell expansion and processing, only articles published within the last five years were included. Solely articles reporting the outcomes of interest across 6- and 12-month follow-up were recruited for eligibility. We included only studies reporting quantitative data under the outcomes of interest. We referred for the quality assessment to the Coleman Methodology Score (CMS). The statistical analysis was performed with Review Manager Software 5.3 (The Nordic Cochrane Centre, Copenhagen).

RESULTS

A total of 18 studies were enrolled in the present study, comprising 1069 treated knees. The mean age of the samples was 57.39 ± 7.37 years. 72% of the included studies harvested the stem cells from the iliac crest (bone marrow-derived MSCs), the remaining 28% from the adipose tissue (adipose-derived MSCs). The mean visual analogic scale improved from 18.37 to 30.98 and 36.91 at 6- and 12-month follow-up, respectively. The mean WOMAC score improved from 25.66 to 25.23 and 15.60 at 6- and 12-month follow-up, respectively. The mean walking distance improved from 71.90 to 152.22 and 316.72 at 6- and 12-month follow-up, respectively. The mean Lequesne scale improved from 33.76 to 12.90 at 12-month follow-up. The KOOS score improved from 41.07 to 8.47% and 18.94 at 6- and 12-month follow-up. All the KOOS subscales improved significantly from the baseline. A total of 136 (12.7%) local complications were detected.

CONCLUSION

According to the current evidences and the main findings of this systematic review, we reported that MSC infiltrations for knee OA can represent a feasible option, leading to an overall remarkable improvement of all clinical and functional considered outcomes, regardless of the cell source. Patients treated at earlier-degeneration stages reported statistically significant greater outcomes. The pain and function scores were improved considerably, thus, leading to a significant improvement of patient participation in recreational activities and quality of life.

Case reports of medication-related osteonecrosis of the jaw (MRONJ) treated with uncultured stromal vascular fraction and L-PRF

Medication-related osteonecrosis of the jaw (MRONJ) is a challenging affection, considering the absence of a "Gold Standard" treatment. Cell therapy and tissue engineering, using adipose-tissue stromal vascular fraction (SVF) containing mesenchymal stromal cells (MSC) and endothelial progenitor cells (EPC); and a scaffold with healing properties, l-platelet-rich fibrin (L-PRF), could be a therapeutic option. Two cases of MRONJ were treated by tissue engineering. The patients presented respectively a stage-II and a stage-III MRONJ. The protocol consists of SVF injection in the L-PRF applied on the cleaned bone. Patients are followed clinically and by medical imaging (MI) for 18 months. The buccal mucosa was closed within a month. No recurrence was observed during the follow-up. The MI highlighted bone formation. MSC and EPC presence, in the SVF, were confirmed by immunophenotyping. We report the preliminary results of MRONJ patients successfully treated with the association of autologous fresh L-PRF-SVF.

Micro-fragmented stromal-vascular fraction plus microfractures provides better clinical results than microfractures alone in symptomatic focal chondral lesions of the knee

PURPOSE

To evaluate clinical outcomes over a 1-year period in patients affected by symptomatic focal chondral lesions of the knee treated with micro-fragmented stromal-vascular fraction plus microfractures compared to microfractures alone.

METHODS

Two groups of 20 patients were arthroscopically treated with microfractures for a symptomatic focal chondral defect of the knee. At the end of surgery, in the experimental group, micro-fragmented stromal-vascular fraction was injected into the joint. Primary end point was WOMAC score at 12 months. Secondary end points were any adverse events, Oxford Knee Score, EQ-5D score, VAS for pain, analgesic and anti-inflammatory consumption.

RESULTS

All the patients were evaluated at 12-month follow-up. No adverse reactions were noted. Analgesic and anti-inflammatory consumption was similar in both groups. At 1-month follow-up, no differences were noted between groups when compared to pre-operative scores. At 3-month follow-up, patients in both groups improved from the baseline in all variables. Significantly lower VAS scores were found in the experimental group (4.2 ± 3.2 vs. 5.9 ± 1.7, p = 0.04). At 6- and 12-month follow-ups, patients in the experimental group scored better in all outcomes with a moderate effect size; in particular, better WOMAC scores were obtained at 12 months, achieving the primary end-point of the study (17.7 ± 11.1 vs. 25.5 ± 12.7; p = 0.03).

CONCLUSIONS

Injection of micro-fragmented stromal-vascular fraction is safe and, when associated with microfractures, is more effective in clinical terms than microfractures alone in patients affected by symptomatic focal chondral lesions of the knee. Results of the current study provide information that could help physicians to improve their counseling for patients concerning ADMSCs.

LEVEL OF EVIDENCE

Level 1-therapeutic study.

Osteochondral Regeneration Using Adipose Tissue-Derived Mesenchymal Stem Cells

Osteoarthritis (OA) is a major joint disease that promotes locomotor deficiency during the middle- to old-age, with the associated disability potentially decreasing quality of life. Recently, surgical strategies to reconstruct both articular cartilage and subchondral bone for OA have been diligently investigated for restoring joint structure and function. Adipose tissue-derived mesenchymal stem cells (AT-MSCs), which maintain pluripotency and self-proliferation ability, have recently received attention as a useful tool to regenerate osteocartilage for OA. In this review, several studies were described related to AT-MSC spheroids, with scaffold and scaffold-free three-dimensional (3D) constructs produced using “mold” or “Kenzan” methods for osteochondral regeneration. First, several examples of articular cartilage regeneration using AT-MSCs were introduced. Second, studies of osteochondral regeneration (not only cartilage but also subchondral bone) using AT-MSCs were described. Third, examples were presented wherein spheroids were produced using AT-MSCs for cartilage regeneration. Fourth, osteochondral regeneration following autologous implantation of AT-MSC scaffold-free 3D constructs, fabricated using the “mold” or “Kenzan” method, was considered. Finally, prospects of osteochondral regeneration by scaffold-free 3D constructs using AT-MSC spheroids were discussed.

Combined Use of Autologous Stromal Vascular Fraction Cells and Platelet-Rich Plasma for Chronic Ulceration of the Diabetic Lower Limb Improves Wound Healing

The discovery of stromal vascular fraction cells and platelet-rich plasma in promoting tissue regeneration has prompted a new idea for the treatment of chronic diabetic ulcer of the lower limb. The study aim was to evaluate the clinical efficacy of a new method that applied stromal vascular fraction cells and platelet-rich plasma together in the treatment of recalcitrant chronic diabetic ulcer. We conducted a single-center, prospective, open, noncontrolled study. Four patients (5 ulcers in total) who had received standard treatment for diabetic ulcer for at least 3 months that failed to heal was enrolled. All patients were treated with surgical debridement, cell suspension (stromal vascular fraction cells suspended by platelet-rich plasma) injection into the wound, and platelet-rich plasma gel coverage. Wounds were measured every week after treatment using a 2-dimensional digital camera and a 3-dimensional wound measurement device. All patients were followed-up for 4 months after the treatment. Four of the 5 ulcers healed completely within a mean of 71.75 ± 29.57 days. The average proportion of granulation tissue achieved 100% within 4 weeks for all cases. The wound size decreased to less than half of the original size for all cases 4 weeks after the treatment. Findings revealed that the new treatment is efficient to achieve wound healing in patients with recalcitrant chronic diabetic ulcer of lower limb.

Animal mesenchymal stem cell research in cartilage regenerative medicine - a review

Healing of articular cartilage is a major clinical challenge as it also lacks a direct vasculature and nerves, and carries a limited number of resident chondrocytes that do not proliferate easily. Damaged articular cartilages are usually replaced by fibrocartilages, which are mechanically and structurally weaker and less resilient. Regenerative medicine involving stem cells is considered to have a definitive potential to overcome the limitations associated with the currently available surgical methods of cartilage repair. Among various stem cell types, mesenchymal stem cells (MSCs) are preferred for clinical applications. These cells can be readily derived from various sources and have the ability to trans-differentiate into various tissue-specific cells, including those of the cartilage by the process of chondrogenesis. Compared to embryonic or induced pluripotent stem cells (iPSCs), no ethical or teratogenic issues are associated with MSCs. These stem cells are being extensively evaluated for the treatment of joint affections and the results appear promising. Unlike human medicine, in veterinary medicine, the literature on stem cell research for cartilage regeneration is limited. This review, therefore, aims to comprehensively discuss the available literature and pinpoint the achievements and limitations associated with the use of MSCs for articular cartilage repair in animal species.

Concise Review: The Regulatory Mechanism of Lysine Acetylation in Mesenchymal Stem Cell Differentiation

Nowadays, the use of MSCs has attracted considerable attention in the global science and technology field, with the self-renewal and multidirectional differentiation potential for diabetes, obesity treatment, bone repair, nerve repair, myocardial repair, and so on. Epigenetics plays an important role in the regulation of mesenchymal stem cell differentiation, which has become a research hotspot in the medical field. This review focuses on the role of lysine acetylation modification on the determination of MSC differentiation direction. During this progress, the recruitment of lysine acetyltransferases (KATs) and lysine deacetylases (KDACs) is the crux of transcriptional mechanisms in the dynamic regulation of key genes controlling MSC multidirectional differentiation.

Current Trends in the Evaluation of Osteochondral Lesion Treatments: Histology, Histomorphometry, and Biomechanics in Preclinical Models

Osteochondral lesions (OCs) are typically of traumatic origins but are also caused by degenerative conditions, in primis osteoarthritis (OA). On the other side, OC lesions themselves, getting worse over time, can lead to OA, indicating that chondral and OC defects represent a risk factor for the onset of the pathology. Many animal models have been set up for years for the study of OC regeneration, being successfully employed to test different treatment strategies, from biomaterials and cells to physical and biological adjuvant therapies. These studies rely on a plethora of post-explant investigations ranging from histological and histomorphometric analyses to biomechanical ones. The present review aims to analyze the methods employed for the evaluation of OC treatments in each animal model by screening literature data within the last 10 years. According to the selected research criteria performed in two databases, 60 works were included. Data revealed that lapine (50% of studies) and ovine (23% of studies) models are predominant, and knee joints are the most used anatomical locations for creating OC defects. Analyses are mostly conducted on paraffin-embedded samples in order to perform histological/histomorphometric analyses by applying semiquantitative scoring systems and on fresh samples in order to perform biomechanical investigations by indentation tests on articular cartilage. Instead, a great heterogeneity is pointed out in terms of OC defect dimensions and animal's age. The choice of experimental times is generally adequate for the animal models adopted, although few studies adopt very long experimental times. Improvements in data reporting and in standardization of protocols would be desirable for a better comparison of results and for ethical reasons related to appropriate and successful animal experimentation.

Comparative Clinical Outcomes After Intra-articular Injection With Adipose-Derived Cultured Stem Cells or Noncultured Stromal Vascular Fraction for the Treatment of Knee Osteoarthritis

BACKGROUND

Intra-articular injection of adipose-derived stem cells (ASCs) has shown promise for improving symptoms and cartilage quality in the treatment of osteoarthritis (OA). However, while most preclinical studies have been performed with plastic-adherent ASCs, most clinical trials are being conducted with the stromal vascular fraction (SVF), prepared from adipose tissue without prior culture.

PURPOSE

To directly compare clinical outcomes of intra-articular injection with ASCs or SVF in patients with knee OA.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

The authors retrospectively compared 6-month outcomes in 42 patients (59 knees) receiving intra-articular injection with 12.75 million ASCs and 38 patients (69 knees) receiving a 5-mL preparation of SVF. All patients had Kellgren-Lawrence grade 2, 3, or 4 knee OA and had failed standard medical therapy. The visual analog scale (VAS) pain score and Knee injury and Osteoarthritis Outcome Score (KOOS) at baseline and 1, 3, and 6 months after injection were considered as outcomes. Outcome Measures in Rheumatology-Osteoarthritis Research Society International (OMERACT-OARSI) criteria were also used to assess positive response. A repeated measures analysis of variance was used for comparison between the treatment groups.

RESULTS

No major complications occurred in either group. The SVF group had a higher frequency of knee effusion (SVF 8%, ASC 2%) and minor complications related to the fat harvest site (SVF 34%, ASC 5%). Both groups reported improvements in pain VAS and KOOS domains. Specifically, in the ASC group, symptoms improved earlier (by 3 months; P < .05) and pain VAS decreased to a greater degree (55%; P < .05) compared with the SVF group (44%). The proportion of OMERACT-OARSI responders in the ASC group was slightly higher (ASCs, 61%; SVF, 55%; P = .25).

CONCLUSION

It was observed that both ASCs and SVF resulted in clinical improvement in patients with knee OA, but that ASCs outperform SVF in the early reduction of symptoms and pain with less comorbidity.

Hypoxia Rapidly Induces the Expression of Cardiomyogenic Factors in Human Adipose-Derived Adherent Stromal Cells

BACKGROUND

The efficacy of interstitial vascular fraction (SVF) transplantation in the treatment of heart disease has been proven in a variety of in vivo studies. In a previous study, we found that bone marrow-derived mesenchymal stem cells (BM-MSCs) altered their expression of several cardiomyogenic factors under hypoxic conditions.

METHODS

We hypothesized that hypoxia may also induce obtained adipose-derived adherent stromal cells (ADASs) from SVFs and adipose-derived stem cells (ASCs) to differentiate into cardiomyocytes and/or cells with comparable phenotypes. We examined the differentiation markers of cell lineages in ADASs and ASCs according to time by hypoxic stress and found that only ADASs expressed cardiomyogenic markers within 24 h under hypoxic conditions in association with the expression of hypoxia-inducible factor 1-α (HIF-1α).

RESULTS

Differentially secreted proteins in a conditioned medium (CM) from ASCs and ADASs under normoxic or hypoxic conditions were detected using an antibody assay and may be associated with a dramatic increase in the expression of cardiomyogenic markers in only ADASs. Furthermore, the cardiomyogenic factors were expressed more rapidly in ADASs than in ASCs under hypoxic conditions in association with the expression of HIF-1α, and angiogenin, fibroblast growth factor-19 (FGF-19) and/or macrophage inhibitory factor (MIF) are related.

CONCLUSIONS

These results provide new insights into the applicability of ADASs preconditioned by hypoxic stress in cardiac diseases.

Adipose-Derived Mesenchymal Stem Cells: A Promising Tool in the Treatment of Musculoskeletal Diseases

Chronic musculoskeletal (MSK) pain is one of the most common medical complaints worldwide and musculoskeletal injuries have an enormous social and economical impact. Current pharmacological and surgical treatments aim to relief pain and restore function; however, unsatiscactory outcomes are commonly reported. In order to find an accurate treatment to such pathologies, over the last years, there has been a significantly increasing interest in cellular therapies, such as adipose-derived mesenchymal stem cells (AMSCs). These cells represent a relatively new strategy in regenerative medicine, with many potential applications, especially regarding MSK disorders, and preclinical and clinical studies have demonstrated their efficacy in muscle, tendon, bone and cartilage regeneration. Nevertheless, several worries about their safety and side effects at long-term remain unsolved. This article aims to review the current state of AMSCs therapy in the treatment of several MSK diseases and their clinical applications in veterinary and human medicine.

A Scaffold-Free Allogeneic Construct From Adipose-Derived Stem Cells Regenerates an Osteochondral Defect in a Rabbit Model

PURPOSE

To determine whether an osteochondral defect could be healed histologically by implanting allogeneic 3-dimensionally formed adipose-derived stem cells (ADSCs) in a rabbit model.

METHODS

Thirty Japanese white rabbits (aged 15-17 weeks) were assigned to 1 of 2 groups. An osteochondral defect (diameter, 4.8 mm; depth, 3 mm) was created in the trochlear groove of the knee using a drill. The defects were left empty in the control group and were filled with cylindrical plugs of allogeneic ADSCs extracted from adipose tissue in the experimental group. Macroscopic scoring, histologic scoring, and immunohistologic stainability of type II collagen were evaluated at 4, 8, and 12 weeks postoperatively.

RESULTS

The macroscopic scores of the healing tissue in the experimental group were significantly greater than those in the control group at 12 weeks (P = .031). Histologically, safranin O staining was noted at 4 weeks and increased gradually over time in the experimental group. The modified International Cartilage Repair Society histologic score in the experimental group was significantly higher than that in the controls at 8 and 12 weeks (14 vs 9 at 8 weeks [P = .008], 18 vs 10 at 12 weeks [P = .007]). The implanted tissue was positive for type II collagen, and stainability increased gradually over time.

CONCLUSIONS

The 3-dimensional scaffold-free allogeneic ADSCs implanted into the osteochondral defect survived, adhered to the defect, increased the stainability of type II collagen gradually over time, and promoted histologic healing in a rabbit model.

CLINICAL RELEVANCE

ADSC implantation designed to promote osteochondral healing may play an important role in osteochondral healing.

Tissue Engineering for the Temporomandibular Joint

Tissue engineering potentially offers new treatments for disorders of the temporomandibular joint which frequently afflict patients. Damage or disease in this area adversely affects masticatory function and speaking, reducing patients' quality of life. Effective treatment options for patients suffering from severe temporomandibular joint disorders are in high demand because surgical options are restricted to removal of damaged tissue or complete replacement of the joint with prosthetics. Tissue engineering approaches for the temporomandibular joint are a promising alternative to the limited clinical treatment options. However, tissue engineering is still a developing field and only in its formative years for the temporomandibular joint. This review outlines the anatomical and physiological characteristics of the temporomandibular joint, clinical management of temporomandibular joint disorder, and current perspectives in the tissue engineering approach for the temporomandibular joint disorder. The tissue engineering perspectives have been categorized according to the primary structures of the temporomandibular joint: the disc, the mandibular condyle, and the glenoid fossa. In each section, contemporary approaches in cellularization, growth factor selection, and scaffold fabrication strategies are reviewed in detail along with their achievements and challenges.

THE EFFECT OF MESENCHYMAL STEM CELL DERIVED MICROVESICLES IN REPAIR OF FEMORAL CHONDRAL DEFECTS IN DOGS

Mesenchymal stem cells (MSCs) releases in culture extracellular vesicles called microvesicles (MVs). MVs have beneficial cytokines that prevent progression of the disease and help in the regeneration process. This study is aimed to evaluate the effect of MSCs derived MVs in repair of induced chondral defect in a dog model. Methods: Chondral defects were created surgically ([Formula: see text][Formula: see text]mm) in both femoral condyles of nine dogs, autologous MSCs were isolated and MVs were prepared and injected intraarticularly in the right joint. The left joint was injected with normal saline as control negative. Evaluation of the treatment after first injection was carried out by physical examination and histopathology at different time periods ([Formula: see text]½, 3 and 6 months). Results: Treated joints showed marked degree of cartilage regeneration and restoration of chondral histomorphological picture on the contrary of the control joints that showed deterioration over time and defect filling with only fibrous tissue forming a fibrocartilage at the end of six months period. Conclusion: We demonstrated in this study that administration of MVs was effective on the functional and morphological recovery of the injured cartilage and could be exploited as a cell free therapeutic approach in regenerative medicine.

The adipose tissue stromal vascular fraction secretome enhances the proliferation but inhibits the differentiation of myoblasts

Background

Adipose tissue is an excellent source for isolation of stem cells for treating various clinical conditions including injuries to the neuromuscular system. Many previous studies have focused on differentiating these adipose stem cells (ASCs) towards a Schwann cell-like phenotype (dASCs), which can enhance axon regeneration and reduce muscle atrophy. However, the stromal vascular fraction (SVF), from which the ASCs are derived, also exerts broad regenerative potential and might provide a faster route to clinical translation of the cell therapies for treatment of neuromuscular disorders.

Methods

The aim of this study was to establish the effects of SVF cells on the proliferation and differentiation of myoblasts using indirect co-culture experiments. A Growth Factor PCR Array was used to compare the secretomes of SVF and dASCs, and the downstream signaling pathways were investigated.

Results

SVF cells, unlike culture-expanded dASCs, expressed and secreted hepatocyte growth factor (HGF) at concentrations sufficient to enhance the proliferation of myoblasts. Pharmacological inhibitor studies revealed that the signal is mediated via ERK1/2 phosphorylation and that the effect is significantly reduced by the addition of 100 pM Norleual, a specific HGF inhibitor. When myoblasts were differentiated into multinucleated myotubes, the SVF cells reduced the expression levels of fast-type myosin heavy chain (MyHC2) suggesting an inhibition of the differentiation process.

Conclusions

In summary, this study shows the importance of HGF as a mediator of the SVF effects on myoblasts and provides further evidence for the importance of the secretome in cell therapy and regenerative medicine applications.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-1096-6) contains supplementary material, which is available to authorized users.

Adipose-Derived Stem Cell Treatments and Formulations

This article analyzes the current literature on the use of adipose-derived stem cells (ASCs) to evaluate the available evidence regarding their therapeutic potential in the treatment of cartilage pathology. Seventeen articles were included and analyzed, showing that there is overall a lack of high-quality evidence concerning the use of ASCs. Most trials are case series with short-term evaluation. The most adopted approach consists of an intra-articular injection of the stromal vascular fraction (SVF) rather than the expanded cells. Based on the available data, no specific preparation method or formulation could be considered as the preferred choice in clinical practice.

Chasing Chimeras - The elusive stable chondrogenic phenotype

The choice of the best-suited cell population for the regeneration of damaged or diseased cartilage depends on the effectiveness of culture conditions (e.g. media supplements, three-dimensional scaffolds, mechanical stimulation, oxygen tension, co-culture systems) to induce stable chondrogenic phenotype. Herein, advances and shortfalls in in vitro, preclinical and clinical setting of various in vitro microenvironment modulators on maintaining chondrocyte phenotype or directing stem cells towards chondrogenic lineage are critically discussed. Chondrocytes possess low isolation efficiency, limited proliferative potential and rapid phenotypic drift in culture. Mesenchymal stem cells are relatively readily available, possess high proliferation potential, exhibit great chondrogenic differentiation capacity, but they tend to acquire a hypertrophic phenotype when exposed to chondrogenic stimuli. Embryonic and induced pluripotent stem cells, despite their promising in vitro and preclinical data, are still under-investigated. Although a stable chondrogenic phenotype remains elusive, recent advances in in vitro microenvironment modulators are likely to develop clinically- and commercially-relevant therapies in the years to come.

Platelet-rich Plasma and Mesenchymal Stem Cells: Exciting, But … are we there Yet?

Joint conditions incapacitate free movement driving to a sedentary lifestyle, a major risk factor for chronic diseases. Regenerative procedures, involving the use of mesenchymal stem/stromal cells along with platelet-rich plasma (PRP), can help patients with these conditions. We describe the main characteristics of cellular products (bone marrow concentrate, stromal vascular fraction of adipose tissue, and mesenchymal stem/stromal cells derived from these tissues), and the potential benefits of combination with PRP in 3 scenarios: PRP lysates used during laboratory cell expansion; PRP to prime cellular products or the host tissue before cell implantation; PRP used as a vehicle for cell transplantation and to provide trophic signals. Clinical studies exploring the benefits of combination products are limited to case series and few controlled studies, involving either arthroscopy or percutaneous injections. Combination products are making their way to clinics but further experimental and clinical research is needed to establish protocols and indications.

The CD45+ fraction in murine adipose tissue derived stromal cells harbors immune-inhibitory inflammatory cells

Stromal cells in adipose tissue are useful for repair/regenerative therapy as they harbor a substantial number of mesenchymal stem cells; therefore, freshly isolated autologous uncultured adipose tissue derived stromal cells (u-ADSCs) are useful for regenerative therapy, and obviate the need for mesenchymal stem cells. We evaluated the therapeutic effect of murine u-ADSCs and sorted subsets of u-ADSCs in a concanavalin A (ConA) induced murine model of hepatitis, as well as their characteristics. We found that 10-20% of u-ADSCs expressed the CD45 leukocyte-related antigen. CD68, which is a marker of macrophages (MΦs), was expressed by 50% of CD45⁺ u-ADSCs. About 90% of CD68⁺ CD45⁺ cells expressed CD206 antigen, which is a marker of inhibitory M2-type MΦs. Genes related to M2-type MUs were especially more highly expressed by CD45⁺ CD206⁺ u-ADSCs than by CD45^- u-ADSCs. CD45⁺ u-ADSCs inhibited the expression of cytokines/chemokines and suppressed the proliferation of splenocytes stimulated with ConA. We observed that not only whole u-ADSCs, but also the CD45⁺ subset of u-ADSCs ameliorated the ConA-induced hepatitis in mice. In conclusion, we show that freshly isolated murine u-ADSCs were effective against acute hepatitis, and CD45⁺ u-ADSCs acting phenotypically and functionally like M2-type MΦs, contributed to the repair of liver tissue undergoing inflammation.

BMP-2 gene activated muscle tissue fragments for osteochondral defect regeneration in the rabbit knee

BACKGROUND

Previously published data indicate that BMP-2 gene activated muscle tissue grafts can repair large bone defects in rats. This innovative abbreviated ex vivo gene therapy is appealing because it does not require elaborative and time-consuming extraction and expansion of cells. Hence, in the present study, we evaluated the potential of this expedited tissue engineering approach for regenerating osteochondral defects in rabbits.

METHODS

Autologous muscle tissue grafts from female White New Zealand rabbits were directly transduced with an adenoviral BMP-2 vector or remained unmodified. Osteochondral defects in the medial condyle of rabbit knees were treated with either BMP-2 activated muscle tissue implants or unmodified muscle tissue or remained empty. After 13 weeks, repair of osteochondral defects was examined by biomechanical indentation testing and by histology/imunohistochemistry applying an extended O'Driscoll scoring system and histomorphometry.

RESULTS

Biomechanical investigations revealed a trend towards slightly improved mechanical properties of the group receiving BMP-2 activated muscle tissue compared to unmodified muscle treatment and empty defect controls. However, a statistically significant difference was noted only between BMP-2 muscle and unmodified muscle treatment. Also, histological evaluation resulted in slightly higher histological scores and improved collagen I/II ratio without statistical significance in the BMP-2 treatment group. Histomorphometry indicated enhanced repair of subchondral bone after treatment with BMP-2 muscle, with a significantly larger bone area compared to untreated defects.

CONCLUSIONS

Gene activated muscle tissue grafts showed potential for osteochondral defect repair. There is room for improvement via the use of appropriate growth factor combinations.

In vivo evaluation of stem cell aggregates on osteochondral regeneration

To date, many osteochondral regenerative approaches have utilized varied combinations of biocompatible materials and cells to engineer cartilage. Even in cell-based approaches, to date, no study has utilized stem cell aggregates alone for regenerating articular cartilage. Thus, the purpose of this study was to evaluate the performance of a novel stem cell-based aggregate approach in a fibrin carrier to regenerate osteochondral defects in the Sprague-Dawley rat trochlear groove model. Two different densities of rat bone marrow mesenchymal stem cell (rBMSC) aggregates were fabricated by the hanging drop technique. At 8 weeks, the cell aggregates supported the defects and served as a catalyst for neo-cartilage synthesis, and the experimental groups may have been beneficial for bone and cartilage regeneration compared to the fibrin-only control and sham groups, as evidenced by histological assessment. The cell density of rBMSC aggregates may thus directly impact chondrogenesis. The usage of cell aggregates with fibrin as a cell-based technology is a promising and translational new treatment strategy for repair of cartilage defects. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1606-1616, 2017.

Use of Freshly Isolated Human Adipose Stromal Cells for Clinical Applications

The clinical use of adipose-derived cells is being explored very actively around the world for various human diseases. Adipose tissue is an abundant tissue source that can be easily harvested using liposuction. Human lipoaspirates contain a significant amount of mesenchymal stromal cells, as well as other progenitors and terminally differentiated cell types. This review covers the isolation of adipose stromal vascular fraction (SVF), the quality control and safety analysis of freshly isolated cell suspensions. The comparison between freshly isolated stromal cells and culture expanded cells from adipose tissue samples is also highlighted. This article provides a brief but comprehensive review about SVF isolation in the clinical setting, cell characterization, and biological potency of freshly obtained adipose stromal cells.

Potential Therapeutic Applications of Adipose-Derived Mesenchymal Stem Cells

Stem cells are subdivided into two main categories: embryonic and adult stem cells. In principle, pluripotent embryonic stem cells might differentiate in any cell types of the organism, whereas the potential of adult stem cells would be more restricted. Although adult stem cells from bone marrow have been initially the most extensively studied, those derived from human adipose tissue have been lately more widely investigated, because of several advantages. First, they can be easily obtained in large amounts from subcutaneous adipose tissue, with minimal pain and morbidity for the patients during harvesting. In addition, they feature low immunogenicity and can differentiate not only in cells of mesodermal lineage (adipocytes, osteoblasts, chondrocytes and muscle cells), but also in cells of other germ layers, such as neural or epithelial cells. As their multilineage differentiation capabilities are increasingly highlighted, their possible use in cell-based regenerative medicine is now broadly explored. In fact, starting from in vitro observations, many studies have already entered the preclinical and clinical phases. In this review, because of our main scientific interest, adipogenic, osteogenic, chondrogenic, and neurogenic differentiation abilities of adipose-derived mesenchymal stem cells, as well as their possible therapeutic applications, are chiefly focused. In addition, their ability to differentiate toward muscle, epithelial, pancreatic, and hepatic cells is briefly reported.