Adipose stem cells can secrete angiogenic factors that inhibit hyaline cartilage regeneration

Cartilage responses to inflammatory stimuli and adipose stem/stromal cell-derived conditioned medium: Results from an ex vivo model

Introduction

Osteoarthritis (OA), a chronic inflammatory joint disorder, still lacks effective therapeutic interventions. Consequently, the development of convenient experimental models is crucial. Recently, research has focused on the plasticity of Mesenchymal Stem/stromal Cells, particularly adipose-derived ones (ASCs), in halting OA progression. This study investigates the therapeutic potential of a cell-free approach, ASC-derived conditioned medium (CM), in reversing cytokine-induced OA markers in an ex vivo model of human cartilage explants.

Methods

4 mm cartilage punches, derived from the femoral heads of patients undergoing total hip replacement, were treated with 10 ng/ml TNFα, 1 ng/ml IL-1β, or a combination of both, over a 3-day period. Analysis of OA-related markers, such as MMP activity, the release of NO and GAGs, and the expression of PTGS2, allowed for the selection of the most effective inflammatory stimulus. Subsequently, explants challenged with TNFα+IL-1β were exposed to CM, consisting of a pool of concentrated supernatants from 72-h cultured ASCs, in order to evaluate its effect on cartilage catabolism and inflammation.

Results

The 3-day treatment with both 10ng/ml TNFα and 1ng/ml IL-1β significantly increased MMP activity and NO release, without affecting GAG release. The addition of CM significantly downregulated the abnormal MMP activity induced by the inflammatory stimuli, while also mildly reducing MMP3, MMP13, and PTGS2 gene expression. Finally, SOX9 and COL2A1 were downregulated by the cytokines, and further decreased by CM.

Conclusion

The proposed cartilage explant model offers encouraging evidence of the therapeutic potential of ASC-derived CM against OA, and it could serve as a convenient ex vivo platform for drug screening.

Chondroprotective Effects of Chondrogenic Differentiated Adipose-Derived Mesenchymal Stem Cells Sheet on Degenerated Articular Cartilage in an Experimental Rabbit Model

Adipose-derived stem cells (ADSCs) have been studied for many years as a therapeutic option for osteoarthritis (OA); however, their efficacy remains insufficient. Since platelet-rich plasma (PRP) induces chondrogenic differentiation in ADSCs and the formation of a sheet structure by ascorbic acid can increase the number of viable cells, we hypothesized that the injection of chondrogenic cell sheets combined with the effects of PRP and ascorbic acid may hinder the progression of OA. The effects of induction of differentiation by PRP and formation of sheet structure by ascorbic acid on changes in chondrocyte markers (collagen II, aggrecan, Sox9) in ADSCs were evaluated. Changes in mucopolysaccharide and VEGF-A secretion from cells injected intra-articularly in a rabbit OA model were also evaluated. ADSCs treated by PRP strongly chondrocyte markers, including type II collagen, Sox9, and aggrecan, and their gene expression was maintained even after sheet-like structure formation induced by ascorbic acid. In this rabbit OA model study, the inhibition of OA progression by intra-articular injection was improved by inducing chondrocyte differentiation with PRP and sheet structure formation with ascorbic acid in ADSCs.

The intra-articular injection of adipose-derived stem cells decreases pain and reduces inflammation in knee osteoarthritis, with or without the addition of platelet-rich plasma also improves functionality

The increase of individuals with Osteoarthritis (OA) has generated an increase in public spending in the treatments, which are still not that effective. So, the purpose of this study was to analyze and compare four types of interventions: platelet-rich plasma (PRP), adipose-derived stem cells (ADSCs), ADSCs + PRP and the standard surgical video arthroscopy (All groups passed through standard arthroscopy before intervention). The evaluation was performed by applying the questionnaires Western Ontario McMaster Universities, Short Form Health Survey 36 and Visual Analog Pain Scale, also by analyzing the synovial fluid (inflammatory cytokines, enzymatic, colorimetric and viscosity analysis), this evaluation happened in two moments: before the surgical procedures and after 6 months of the interventions and also was made a comparison to standard arthroscopy. The questionnaires results showed a greater improvement in the scores of the domains analyzed in the ADSCs + PRP group, followed by the ADSCs and PRP group. In the evaluation of inflammatory cytokines, there was a significant reduction in the cytokine IL-1b only in the ADSCs + PRP group (46%) and ADSCs (31%), of IL-6 in the ADSCs + PRP group (72%), of IL-8 in the ADSCs + PRP group (50%) and ADSCs (31%), and TNF in the ADSCs + PRP group (46%). There was also a significant increase in the amount of total proteins (79%) in the control group and polymorphonuclear cells (47%) in the ADSCs + PRP group. Taking all the results into account, we infer that therapies with ADSCs + PRP and only ADSCs are safe and effective over 6 months for the improvement of pain, functional capacity and joint inflammation in volunteers with OA. It is also considered that the use of ADSCs + PRP, particularly, is a promising alternative to help manage this disease, due to the better results presented among the four propose interventions.

OUP accepted manuscript

Cells of the stromal vascular fraction (SVF) of human adipose tissue have the capacity to generate osteogenic grafts with intrinsic vasculogenic properties. However, cultured adipose-derived stromal cells (ASCs), even after minimal monolayer expansion, lose osteogenic capacity in vivo. Communication between endothelial and stromal/mesenchymal cell lineages has been suggested to improve bone formation and vascularization by engineered tissues. Here, we investigated the specific role of a subpopulation of SVF cells positive for T-cadherin (T-cad), a putative endothelial marker. We found that maintenance during monolayer expansion of a T-cad-positive cell population, composed of endothelial lineage cells (ECs), is mandatory to preserve the osteogenic capacity of SVF cells in vivo and strongly supports their vasculogenic properties. Depletion of T-cad-positive cells from the SVF totally impaired bone formation in vivo and strongly reduced vascularization by SVF cells in association with decreased VEGF and Adiponectin expression. The osteogenic potential of T-cad-depleted SVF cells was fully rescued by co-culture with ECs from a human umbilical vein (HUVECs), constitutively expressing T-cad. Ectopic expression of T-cad in ASCs stimulated mineralization in vitro but failed to rescue osteogenic potential in vivo, indicating that the endothelial nature of the T-cad-positive cells is the key factor for induction of osteogenesis in engineered grafts based on SVF cells. This study demonstrates that crosstalk between stromal and T-cad expressing endothelial cells within adipose tissue critically regulates osteogenesis, with VEGF and adiponectin as associated molecular mediators.

Infrapatellar Fat Pads-Derived Stem Cell Is a Favorable Cell Source for Articular Cartilage Tissue Engineering: An In Vitro and Ex Vivo Study Based on 3D Organized Self-Assembled Biomimetic Scaffold

OBJECTIVE

Adipose tissue-derived stem cells (ASCs) are a promising source of cells for articular cartilage regeneration. However, ASCs isolated from different adipose tissue depots have heterogeneous cell characterizations and differentiation potential when cultured in 3-dimensional (3D) niches.

DESIGN

We compared the chondrogenicity of ASCs isolated from infrapatellar fat pads (IPFPs) and subcutaneous fat pads (SCFPs) in 3D gelatin-based biomimetic matrix.

RESULTS

The IPFP-ASC-differentiated chondrocytes had higher ACAN, COL2A1, COL10, SOX6, SOX9, ChM-1, and MIA-3 mRNA levels and lower COL1A1 and VEGF levels than the SCFP-ASCs in 3D matrix. The difference in mRNA profile may have contributed to activation of the Akt, p38, RhoA, and JNK signaling pathways in the IPFP-ASCs. The chondrocytes differentiated from IPFP-ASCs had pronounced glycosaminoglycan and collagen type II production and a high chondroitin-6-sulfate/chondroitin-4-sulfate ratio with less polymerization of β-actin filaments. In an ex vivo mice model, magnetic resonance imaging revealed a shorter T2 relaxation time, indicating that more abundant extracellular matrix was secreted in the IPFP-ASC-matrix group. Histological examinations revealed that the IPFP-ASC matrix had higher chondrogenic efficacy of new cartilaginous tissue generation as evident in collagen type II and S-100 staining. Conclusion. ASCs isolated from IPFPs may be better candidates for cartilage regeneration, highlighting the translational potential of cartilage tissue engineering using the IPFP-ASC matrix technique.

Alginate microgels as delivery vehicles for cell-based therapies in tissue engineering and regenerative medicine

Conventional stem cell delivery typically utilize administration of directly injection of allogenic cells or domesticated autogenic cells. It may lead to immune clearance of these cells by the host immune systems. Alginate microgels have been demonstrated to improve the survival of encapsulated cells and overcome rapid immune clearance after transplantation. Moreover, alginate microgels can serve as three-dimensional extracellular matrix to support cell growth and protect allogenic cells from rapid immune clearance, with functions as delivery vehicles to achieve sustained release of therapeutic proteins and growth factors from the encapsulated cells. Besides, cell-loaded alginate microgels can potentially be applied in regenerative medicine by serving as injectable engineered scaffolds to support tissue regrowth. In this review, the properties of alginate and different methods to produce alginate microgels are introduced firstly. Then, we focus on diverse applications of alginate microgels for cell delivery in tissue engineering and regenerative medicine.

Hyperosmolarity benefits cartilage regeneration by enhancing expression of chondrogenic markers and reducing inflammatory markers

Application of hyperosmolarity can be a promising strategy to promote chondrogenic differentiation in adipose-derived mesenchymal stem cells (ADSCs). Growth factors may promote different signaling pathways in parallel that is why in this study we monitor undesired pathologic or unwanted side effects as well as chondroinductive impacts of hyperosmolarity in differentiating ADSCs. Quantified gene expression, immunocytochemistry, glycosaminoglycan deposition and angiogenic secretion assays performed along with immunoassay. We observed that hyperosmolarity pressure of 480 mOsm over-expressed cartilage specific markers at gene expression level in the extra cellular matrix. Meanwhile, hyperosmolarity of 480 mOsm diminished the expression of cartilage associated pathologic markers, i.e., inflammatory and angiogenic attributes. Certain dose of hyperosmolarity could benefit chondrogenesis in a dual way, first by increasing chondrogenic markers and second by lowering tissue mineralization and angiogenic potential. The chondroprotective potential of hyperosmolarity could have a promising benefit in cartilage cell therapy and tissue engineering.

Assessment of safety and efficacy of intra-articular injection of stromal vascular fraction for the treatment of knee osteoarthritis-a systematic review

PURPOSE

Stromal vascular fraction (SVF) as an injectable regenerative therapy for knee osteoarthritis (OA) has gained recent popularity. However, there is no clear consensus on the outcomes of such treatment. We systematically reviewed available evidence on the use of SVF injection in the treatment of knee OA.

METHODS

The study was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, with keyword search in PubMed, Scopus, and the Cochrane Library Database and related article search in Google Scholar. Clinical studies demonstrating effects of SVF in knee OA and published in English literature were included. Risk of bias assessment was done with modified Coleman Methodology Scoring (CMS).

RESULTS

Eleven studies (9 prospective, 2 retrospective) that contributed to 290 knees in 200 patients were included. Two studies that contributed to 3718 knee injections were excluded from pooled analysis and were scrutinized separately. Majority of patients reported improvement in pain, range of motion (ROM), functional rating, six metre walking distance, and functional outcome scores. There was no major donor-site morbidity. There was only one reported case of knee joint infection and no case of tumour formation in relation to SVF injection.

DISCUSSION

Intra-articular injection of SVF can be a simple, affordable, and minimally invasive treatment that could serve as an interim option for patients who failed other conservative and arthroscopic options.

CONCLUSION

Intra-articular injection of SVF is a safe and effective technique for the management of knee OA. However, comparative Level I studies are needed to support the use of adjuvants with SVF and also to compare the use of SVF (with or without adjuvants) with ADMSCs, PRP, and bone marrow concentrate.

Mesenchymal Stem Cell Secretome as an Emerging Cell-Free Alternative for Improving Wound Repair

The use of mesenchymal stem cells (MSC) for the treatment of cutaneous wounds is currently of enormous interest. However, the broad translation of cell therapies into clinical use is hampered by their efficacy, safety, manufacturing and cost. MSCs release a broad repertoire of trophic factors and immunomodulatory cytokines, referred to as the MSC secretome, that has considerable potential for the treatment of cutaneous wounds as a cell-free therapy. In this review, we outline the current status of MSCs as a treatment for cutaneous wounds and introduce the potential of the MSC secretome as a cell-free alternative for wound repair. We discuss the challenges and provide insights and perspectives for the future development of the MSC secretome as well as identify its potential clinical translation into a therapeutic treatment.

Nasal Chondrocyte-Derived Soluble Factors Affect Chondrogenesis of Cocultured Mesenchymal Stem Cells

To investigate the effect of soluble factors released from human nasal chondrocytes (NCs) on cocultured human bone marrow mesenchymal stem cells (MSCs) and NC tissue-engineered constructs. Cartilage engineered from pure NCs on a three-dimensional (3D) porous collagen scaffold was cultured indirectly in a Transwell system with cartilage engineered from a direct coculture of human bone marrow-derived MSCs and NCs on a 3D porous collagen scaffold. The soluble factors were measured in the conditioned media from the different chambers of the Transwell system. Engineered cartilage from cocultures exposed to the pure NC construct exhibited reduced chondrogenic potential relative to control constructs, shown by reduced extracellular matrix deposition and increased expression of hypertrophic markers. Analysis of the soluble factors within the conditioned media showed an increase in inflammatory cytokines in the coculture chamber exposed to the pure NC construct. Principal component analysis revealed that the majority of the data variance could be explained by proinflammatory factors and hypertrophic chondrogenesis. In conclusion, our data suggest that inflammatory cytokines derived from NCs reduce the chondrogenic potential of coculture engineered cartilage through the induction of hypertrophic chondrogenesis. Impact statement The use of engineered cartilage from cocultured nasal chondrocytes (NCs) and mesenchymal stem cells for nasal cartilage reconstruction may be problematic. Our data suggest that the soluble factors from surrounding native NCs in the cartilage to be fixed can compromise the quality of the engineered cartilage if used in reconstructive surgery.

In vivo evaluation of an electrospun and 3D printed cellular delivery device for dermal wound healing

Burns and chronic wounds are especially challenging wounds to heal. In efforts to heal these wounds, physicians often use autologous skin grafts to help restore mechanical and barrier functionality to the wound area. These grafts are, by nature, limited in availability. In an effort to provide an alternative, we have developed an electrospun wound dressing designed to incorporate into the wound with the option to deliver a cellular payload. Here, a blend of poly(glycolic acid) and poly(ethylene glycol) was electrospun as part of a custom fabrication method that incorporated 3D printed poly(vinyl alcohol) sacrificial elements. This preparation is unique compared to traditional electrospinning as sacrificial elements provide an internal void space for an injectable payload to be delivered to the wound site. When the construct was tested in vivo (full thickness excisional skin wounds), wound closure was slightly delayed by the presence of the scaffold in both normal and challenged wounds. Quality of healing was improved in normal wounds as measured by histomorphometrics when treated with the construct and exhibited increased neovascularization. Our results demonstrate that the extracellular matrix-like scaffold developed in this study is beneficial to healing of full thickness skin defects and may benefit challenged wounds.

Production of osteogenic and angiogenic factors by microencapsulated adipose stem cells varies with culture conditions

Growth factors produced by stem cells aid in the bone repair process. We investigated the ability of encapsulated rat adipose-derived stem cells (rASCs) treated with osteogenic media (OM) to produce growth factors, and determined the optimal combination of OM components that will lead to the production of both osteogenic and angiogenic factors. Our results demonstrate that microencapsulated stem cells were able to produce vascular endothelial growth factor (VEGF), fibroblast growth factor-2, and bone morphogenetic protein-2 (BMP2) necessary for bone regeneration. OM led to the reduction of angiogenic factors; however, the removal of dexamethasone restored angiogenic factor production. Additionally, we determined whether the effect of dexamethasone on VEGF and BMP2 varied among rat, rabbit, mouse, and humans. Dexamethasone led to a reduction in VEGF levels in ASCs derived from rats, mice, and humans, while this reduction was absent in rabbit ASCs (rbASCs). Human ASCs (hASCs) from donors of different race and sex showed a similar response to dexamethasone with secreted VEGF levels. BMP2 levels secreted by rbASCs, mouse ASCs (mASCs), and hASCs were independent of the media treatments, while rASCs responded differently in the surrounding media and within the microbeads. In conclusion, microencapsulated ASCs can be treated to produce osteogenic and angiogenic factors for tissue regeneration applications, but outcomes may vary with culture conditions.

Adipose tissue-derived stromal cells' conditioned medium modulates endothelial-mesenchymal transition induced by IL-1β/TGF-β2 but does not restore endothelial function

Objectives

Endothelial cells undergo TGF‐β–driven endothelial‐mesenchymal transition (EndMT), representing up to 25% of cardiac myofibroblasts in ischaemic hearts. Previous research showed that conditioned medium of adipose tissue–derived stromal cells (ASC‐CMed) blocks the activation of fibroblasts into fibrotic myofibroblasts. We tested the hypothesis that ASC‐CMed abrogates EndMT and prevents the formation of adverse myofibroblasts.

Materials and methods

Human umbilical vein endothelial cells (HUVEC) were treated with IL‐1β and TGF‐β2 to induce EndMT, and the influence of ASC‐CMed was assessed. As controls, non‐treated HUVEC or HUVEC treated only with IL‐1β in the absence or presence of ASC‐CMed were used. Gene expression of inflammatory, endothelial, mesenchymal and extracellular matrix markers, transcription factors and cell receptors was analysed by RT‐qPCR. The protein expression of endothelial and mesenchymal markers was evaluated by immunofluorescence microscopy and immunoblotting. Endothelial cell function was measured by sprouting assay.

Results

IL‐1β/TGF‐β2 treatment induced EndMT, as evidenced by the change in HUVEC morphology and an increase in mesenchymal markers. ASC‐CMed blocked the EndMT‐related fibrotic processes, as observed by reduced expression of mesenchymal markers TAGLN (P = 0.0008) and CNN1 (P = 0.0573), as well as SM22α (P = 0.0501). The angiogenesis potential was impaired in HUVEC undergoing EndMT and could not be restored by ASC‐CMed.

Conclusions

We demonstrated that ASC‐CMed reduces IL‐1β/TGF‐β2‐induced EndMT as observed by the loss of mesenchymal markers. The present study supports the anti‐fibrotic effects of ASC‐CMed through the modulation of the EndMT process.

Dual functional nanoparticles containing SOX duo and ANGPT4 shRNA for osteoarthritis treatment

In our previous studies, we found that adult stem cells transfected with sex-determining region Y-box (SOX)-9, -6 and -5 genes (SOX trio) enhanced chondrogenesis and suppressed the progression of osteoarthritis (OA). The inhibition of angiopoietin-like 4 (ANGPT4) is known to reduce levels of cartilage damaging enzymes, such as, matrix metalloproteinases (MMPs). In this study, we designed nanoparticles comprising dexamethasone-conjugated polyethylenimine (_DEX PEI) complexed with minicircle plasmid (MC) harboring SOX duo (SOX-9, -6) and ANGPTL4 small hairpin RNA (shANG) [_MC SOX9/6/shANG] in the expectation that transfection of these nanoparticles would enhance chondrogenesis of stem cells and suppress inflammation in OA. Adipose-derived stem cells (ADSCs) transfected with _MC SOX9/6/shANG (_MC SOX9/6/shANG-tADSCs) showed significantly higher expressions of COL2 gene and protein than _MC SOX9/6-transfected ADSCs (_MC SOX9/6-tADSCs) during in vitro chondrogenesis while both enhanced chondrogenesis in the absence of growth factor addition as compared with negative controls. Furthermore, the expressions of MMP13 and MMP3 genes were significantly more diminished in _MC SOX9/6/shANG-tADSCs than in _MC SOX9/6-tADSCs. In vivo experiments using surgically-induced OA rats showed _MC SOX9/6/shANG-tADSC-treated rats had significantly lower levels of cyclooxygenase (COX-2) and MMP13 in synovial fluids than _MC SOX9/6-tADSC-treated rats, but no significant difference was observed between them in histological appearances. Both groups showed significantly less joint destruction than control groups did. These results demonstrate that dual functional nanoparticles containing SOX duo and ANGPT4 shRNA enhance chondrogenesis of ADSCs and suppress inflammation in OA. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 108B:234-242, 2020.

CD271-selected mesenchymal stem cells from adipose tissue enhance cartilage repair and are less angiogenic than plastic adherent mesenchymal stem cells

CD271 is a marker of bone marrow MSCs with enhanced differentiation capacity for bone or cartilage repair. However, the nature of CD271+ MSCs from adipose tissue (AT) is less well understood. Here, we investigated the differentiation, wound healing and angiogenic capacity of plastic adherent MSCs (PA MSCs) versus CD271+ MSCs from AT. There was no difference in the extent to which PA MSCs and CD271+ MSCs formed osteoblasts, adipocytes or chondrocytes in vitro. In contrast, CD271+ MSCs transplanted into athymic rats significantly enhanced osteochondral wound healing with reduced vascularisation in the repair tissue compared to PA MSCs and control animals; there was little histological evidence of mature articular cartilage formation in all animals. Conditioned medium from CD271+ MSC cultures was less angiogenic than PA MSC conditioned medium, and had little effect on endothelial cell migration or endothelial tubule formation in vitro. The low angiogenic activity of CD271+ MSCs and improved early stage tissue repair of osteochondral lesions when transplanted, along with a comparable differentiation capacity along mesenchymal lineages when induced, suggests that these selected cells are a better candidate than PA MSCs for the repair of cartilaginous tissue.

Bone regeneration strategies: Engineered scaffolds, bioactive molecules and stem cells current stage and future perspectives

Bone fractures are the most common traumatic injuries in humans. The repair of bone fractures is a regenerative process that recapitulates many of the biological events of embryonic skeletal development. Most of the time it leads to successful healing and the recovery of the damaged bone. Unfortunately, about 5-10% of fractures will lead to delayed healing or non-union, more so in the case of co-morbidities such as diabetes. In this article, we review the different strategies to heal bone defects using synthetic bone graft substitutes, biologically active substances and stem cells. The majority of currently available reviews focus on strategies that are still at the early stages of development and use mostly in vitro experiments with cell lines or stem cells. Here, we focus on what is already implemented in the clinics, what is currently in clinical trials, and what has been tested in animal models. Treatment approaches can be classified in three major categories: i) synthetic bone graft substitutes (BGS) whose architecture and surface can be optimized; ii) BGS combined with bioactive molecules such as growth factors, peptides or small molecules targeting bone precursor cells, bone formation and metabolism; iii) cell-based strategies with progenitor cells combined or not with active molecules that can be injected or seeded on BGS for improved delivery. We review the major types of adult stromal cells (bone marrow, adipose and periosteum derived) that have been used and compare their properties. Finally, we discuss the remaining challenges that need to be addressed to significantly improve the healing of bone defects.

Microencapsulated rabbit adipose stem cells initiate tissue regeneration in a rabbit ear defect model

Cell-based tissue engineering can promote cartilage tissue regeneration, but cell retention in the implant site post-delivery is problematic. Alginate microbeads containing adipose stem cells (ASCs) pretreated with chondrogenic media have been used successfully to regenerate hyaline cartilage in critical size defects in rat xiphoid suggesting that they may be used to treat defects in elastic cartilages such as the ear. To test this, we used microbeads made with low viscosity, high mannuronate medical grade alginate using a high electrostatic potential, and a calcium cross linking solution containing glucose. Microbeads containing rabbit ASCs (rbASCs) were implanted bilaterally in 3 mm critical size midcartilage ear defects of six skeletally mature male New Zealand White rabbits (empty defect; microbeads without cells; microbeads with cells; degradable microbeads with cells; and autograft). Twelve weeks post-implantation, regeneration was assessed by microCT and histology. Microencapsulated rbASCs cultured in chondrogenic media expressed mRNAs for aggrecan, Type II collagen, and Type X collagen. Histologically, empty defects contained fibrous tissue; microbeads without cells were still present in defects and were surrounded by fibrous tissue; nondegradable beads with rbASCs initiated cartilage regeneration; degradable microbeads with cells produced immature bone-like tissue, also demonstrated by microCT; and autografts appeared as normal auricular cartilage but were not fully integrated with the tissue surrounding the defect. Elastin, the hallmark of auricular cartilage, was not evident in the neocartilage. This delivery system offers the potential for regeneration of auricular cartilage, but vascularity of the treatment site and use of factors that induce elastin must be considered.

Trophic effects of adipose-tissue-derived and bone-marrow-derived mesenchymal stem cells enhance cartilage generation by chondrocytes in co-culture

AIMS

Combining mesenchymal stem cells (MSCs) and chondrocytes has great potential for cell-based cartilage repair. However, there is much debate regarding the mechanisms behind this concept. We aimed to clarify the mechanisms that lead to chondrogenesis (chondrocyte driven MSC-differentiation versus MSC driven chondroinduction) and whether their effect was dependent on MSC-origin. Therefore, chondrogenesis of human adipose-tissue-derived MSCs (hAMSCs) and bone-marrow-derived MSCs (hBMSCs) combined with bovine articular chondrocytes (bACs) was compared.

METHODS

hAMSCs or hBMSCs were combined with bACs in alginate and cultured in vitro or implanted subcutaneously in mice. Cartilage formation was evaluated with biochemical, histological and biomechanical analyses. To further investigate the interactions between bACs and hMSCs, (1) co-culture, (2) pellet, (3) Transwell® and (4) conditioned media studies were conducted.

RESULTS

The presence of hMSCs-either hAMSCs or hBMSCs-increased chondrogenesis in culture; deposition of GAG was most evidently enhanced in hBMSC/bACs. This effect was similar when hMSCs and bAC were combined in pellet culture, in alginate culture or when conditioned media of hMSCs were used on bAC. Species-specific gene-expression analyses demonstrated that aggrecan was expressed by bACs only, indicating a predominantly trophic role for hMSCs. Collagen-10-gene expression of bACs was not affected by hBMSCs, but slightly enhanced by hAMSCs. After in-vivo implantation, hAMSC/bACs and hBMSC/bACs had similar cartilage matrix production, both appeared stable and did not calcify.

CONCLUSIONS

This study demonstrates that replacing 80% of bACs by either hAMSCs or hBMSCs does not influence cartilage matrix production or stability. The remaining chondrocytes produce more matrix due to trophic factors produced by hMSCs.

Non-contact Coculture Reveals a Comprehensive Response of Chondrocytes Induced by Mesenchymal Stem Cells Through Trophic Secretion

Coculture between mesenchymal stem cells (MSCs) and chondrocytes has significant implications in cartilage regeneration. However, a conclusive understanding remains elusive. Previously, we reported that rabbit bone marrow-derived MSCs (rbBMSCs) could downregulate the differentiated phenotype of rabbit articular chondrocytes (rbACs) in a non-contact coculture system for the first time. In the present study, a systemic investigation was performed to understand the biological characteristics of chondrocytes in coculture with MSCs. Firstly, cells (MSCs and chondrocytes) from different origins were cocultured in transwell system. Different chondrocytes, when cocultured with different MSCs respectively, consistently demonstrated stimulated proliferation, transformed morphology and declined glycosaminoglycan secretion of chondrocytes. Next, cell surface molecules and the global gene expression of rbACs were characterized. It was found that cocultured rbACs showed a distinct surface molecule profile and global gene expression compared to both dedifferentiated rbACs and rbBMSCs. In the end, cocultured rbACs were passaged and induced to undergo the chondrogenic redifferentiation. Better growth and chondrogenesis ability were confirmed compared with control cells without coculture. Together, chondrocytes display comprehensive changes in coculture with MSCs and the cocultured rbACs are beneficial for cartilage repair.

Microencapsulation of Stem Cells for Therapy

An increasing demand to regenerate tissues from patient-derived sources has led to the development of cell-based therapies using autologous stem cells, thereby decreasing immune rejection of scaffolds coupled with allogeneic stem cells or allografts. Adult stem cells are multipotent and are readily available in tissues such as fat and bone marrow. They possess the ability to repair and regenerate tissue through the production of therapeutic factors, particularly vasculogenic proteins. A major challenge in cell-based therapies is localizing the delivered stem cells to the target site. Microencapsulation of cells provides a porous polymeric matrix that can provide a protected environment, localize the cells to one area, and maintain their viability by enabling the exchange of nutrients and waste products between the encapsulated cells and the surrounding tissue. In this chapter, we describe a method to produce injectable microbeads containing a tunable number of stem cells using the biopolymer alginate. The microencapsulation process involves extrusion of the alginate suspension containing cells from a microencapsulator, a syringe pump to control its flow rate, an electrostatic potential to overcome capillary forces and a reduced Ca⁺⁺ cross-linking solution containing a nutrient osmolyte, to form microbeads. This method allows the encapsulated cells to remain viable up to three weeks in culture and up to three months in vivo and secrete growth factors capable of supporting tissue regeneration.

Hydrogels derived from cartilage matrices promote induction of human mesenchymal stem cell chondrogenic differentiation

Limited supplies of healthy autologous or allogeneic cartilage sources have inspired a growing interest in xenogeneic cartilage matrices as biological scaffolds for cartilage tissue engineering. The objectives of this study were to determine if shark and pig cartilage extracellular matrix (ECM) hydrogels can stimulate chondrocytic differentiation of mesenchymal stem cells (MSCs) without exogenous growth factors and to determine if the soluble factors retained by these ECM hydrogels are responsible. Human MSCs cultured on hydrogels from shark skull cartilage, pig articular cartilage, and pig auricular cartilage ECM had increased expression of chondrocyte markers and decreased secretion of angiogenic factors VEGF-A and FGF2 in comparison to MSCs cultured on tissue culture polystyrene (TCPS) at one week. MSCs grown on shark ECM gels had decreased type-1 collagen mRNA as compared to all other groups. Degradation products of the cartilage ECM gels and soluble factors released by the matrices increased chondrogenic and decreased angiogenic mRNA levels, indicating that the processed ECM retains biochemically active proteins that can stimulate chondrogenic differentiation. In conclusion, this work supports the use of cartilage matrix-derived hydrogels for chondrogenic differentiation of MSCs and cartilage tissue engineering. Longer-term studies and positive controls will be needed to support these results to definitively demonstrate stimulation of chondrocyte differentiation, and particularly to verify that calcification without endochondral ossification does not occur as it does in shark cartilage.

STATEMENT OF SIGNIFICANCE

The objectives of this study were to determine if shark and pig cartilage extracellular matrix (ECM) hydrogels can stimulate chondrocytic differentiation of mesenchymal stem cells (MSCs) without exogenous growth factors and to determine if the soluble factors retained by these ECM hydrogels are responsible for this induction. Sharks are an especially interesting model for cartilage regeneration because their entire skeleton is composed of cartilage and they do not undergo endochondral ossification. Culturing human MSCs on porcine and shark cartilage ECM gels directly, with ECM gel conditioned media, or degradation products increased mRNA levels of chondrogenic factors while decreasing angiogenic factors. These studies indicate that xenogeneic cartilage ECMs have potential as biodegradable scaffolds capable of stimulating chondrogenesis while preventing angiogenesis for regenerative medicine applications and that ECM species selection can yield differential effects.

Mesenchymal Stem Cells Reshape and Provoke Proliferation of Articular Chondrocytes by Paracrine Secretion

Coculture between mesenchymal stem cells (MSCs) and articular chondrocytes (ACs) represents a promising strategy for cartilage regeneration. This study aimed at elaborating how ACs were regulated by MSCs. Rabbit ACs (rACs) and rabbit MSCs (rMSCs) were seeded separately in a Transwell system to initiate non-contact coculture in growth medium without chondrogenic factors. Cell morphology, cell proliferation, production of extracellular matrix (ECM), and gene expression of rACs were characterized. Upon coculture, rACs underwent a morphological transition from a rounded or polygonal shape into a fibroblast-like one and proliferation was provoked simultaneously. Such effects were dependent on the amount of rMSCs. Along with these changes, ECM production and gene expression of rACs were also perturbed. Importantly, when a ROCK inhibitor (Y27632) was supplemented to coculture, the effects except that on cell proliferation were inhibited, suggesting the involvement of RhoA/ROCK signaling. By applying an inhibitor (BIBF1120) of VEGFR1/2/3, FGFR1/2/3 and PDGFRα/β in coculture, or supplementing FGF-1, VEGF-A and PDGFbb in monoculture, it was confirmed that the paracrine factors by rMSCs mediated the compounding effects on rACs. These findings shed light on MSCs-ACs interactions and might confer an insight view on cell-based cartilage regeneration.

Effects of low oxygen tension on gene profile of soluble growth factors in co-cultured adipose-derived stromal cells and chondrocytes

OBJECTIVES

Moving towards development of optimized cartilage regeneration with adipose-derived stromal cells (ASCs), the focus of this study was on investigating the influence of hypoxia on soluble factors secreted by ASCs and chondrocytes after crosstalk.

METHODS

We established direct contact co-culture and non-contact co-culture systems by using red or green fluorescent protein (R/GFP)-labelled mice and SD rats respectively. Gene variation of growth factors of the two cell types, in both hypoxic and normoxic conditions, were screened using semi-quantitative polymerase chain reaction (PCR).

RESULTS

Co-culture with ASCs and chondrocytes under hypoxia was shown to successfully induce or enhance ASC to chondrogenic differentiation. To be specific, chondrogenic maker genes: AGC, COL II and SOX9 were remarkably enhanced in both ASCs and chondrocytes after crosstalk under low oxygen tension. Subsequently, screening growth factors in ASCs and chondrocytes under hypoxia showed that HIF-1α, VEGF-A/B, BMP-2/-4/-6, FGF-2 and IGF-1 were significantly increased, but not TGF-β1.

CONCLUSIONS

These results revealed that both hypoxia and co-culture systems can notably enhance chondrogenesis of ASCs as well as increase proliferation of ASCs and chondrocytes.

Multipotent Mesenchymal Stem Cell Treatment for Discogenic Low Back Pain and Disc Degeneration

Low back pain with resultant loss of function, decreased productivity, and high economic costs is burdensome for both the individual and the society. Evidence suggests that intervertebral disc pathology is a major contributor to spine-related pain and degeneration. When commonly used conservative therapies fail, traditional percutaneous or surgical options may be beneficial for pain relief but are suboptimal because of their inability to alter disc microenvironment catabolism, restore disc tissue, and/or preserve native spine biomechanics. Percutaneously injected Multipotent Mesenchymal Stem Cell (MSC) therapy has recently gained clinical interest for its potential to revolutionarily treat disc-generated (discogenic) pain and associated disc degeneration. Unlike previous therapies to date, MSCs may uniquely offer the ability to improve discogenic pain and provide more sustained improvement by reducing disc microenvironment catabolism and regenerating disc tissue. Consistent treatment success has the potential to create a paradigm shift with regards to the treatment of discogenic pain and disc degeneration.

Modulating stem cell–chondrocyte interactions for cartilage repair using combinatorial extracellular matrix-containing hydrogels

Combinatorial ECM-containing hydrogels with decoupled mechanical and biochemical cues modulate cartilage formation by a stem cell and chondrocyte co-culture in 3D.

An In Vitro Comparison of the Incorporation, Growth, and Chondrogenic Potential of Human Bone Marrow versus Adipose Tissue Mesenchymal Stem Cells in Clinically Relevant Cell Scaffolds Used for Cartilage Repair

AIM

To compare the incorporation, growth, and chondrogenic potential of bone marrow (BM) and adipose tissue (AT) mesenchymal stem cells (MSCs) in scaffolds used for cartilage repair.

METHODS

Human BM and AT MSCs were isolated, culture expanded, and characterised using standard protocols, then seeded into 2 different scaffolds, Chondro-Gide or Alpha Chondro Shield. Cell adhesion, incorporation, and viable cell growth were assessed microscopically and following calcein AM/ethidium homodimer (Live/Dead) staining. Cell-seeded scaffolds were treated with chondrogenic inducers for 28 days. Extracellular matrix deposition and soluble glycosaminoglycan (GAG) release into the culture medium was measured at day 28 by histology/immunohistochemistry and dimethylmethylene blue assay, respectively.

RESULTS

A greater number of viable MSCs from either source adhered and incorporated into Chondro-Gide than into Alpha Chondro Shield. In both cell scaffolds, this incorporation represented less than 2% of the cells that were seeded. There was a marked proliferation of BM MSCs, but not AT MSCs, in Chondro-Gide. MSCs from both sources underwent chondrogenic differentiation following induction. However, cartilaginous extracellular matrix deposition was most marked in Chondro-Gide seeded with BM MSCs. Soluble GAG secretion increased in chondrogenic versus control conditions. There was no marked difference in GAG secretion by MSCs from either cell source.

CONCLUSION

Chondro-Gide and Alpha Chondro Shield were permissive to the incorporation and chondrogenic differentiation of human BM and AT MSCs. Chondro-Gide seeded with BM MSCs demonstrated the greatest increase in MSC number and deposition of a cartilaginous tissue.

Therapeutic application of mesenchymal stem cells in osteoarthritis

INTRODUCTION

Osteoarthritis (OA) is a degenerative disease characterized by cartilage degradation and subchondral bone alterations. This disease represents a global public health problem whose prevalence is rapidly growing with the increasing aging of the population. With the discovery of mesenchymal stem cells (MSC) as possible therapeutic agents, their potential for repairing cartilage damage in OA is under investigation.

AREAS COVERED

Characterization of MSCs and their functional properties are mentioned with an insight into their trophic function and secretory profile. We present a special focus on the types of extracellular vesicles (EVs) that are produced by MSCs and their role in the paracrine activity of MSCs. We then discuss the therapeutic approaches that have been evaluated in pre-clinical models of OA and the results coming out from the clinical trials in patients with OA.

EXPERT OPINION

MSC-based therapy seems a promising approach for the treatment of patients with OA. Further research is still needed to demonstrate their efficacy in clinical trials using controlled, prospective studies. However, the emergence of MSC-derived EVs as possible therapeutic agents could be an alternative to cell-based therapy.

Gene profile of soluble growth factors involved in angiogenesis, in an adipose-derived stromal cell/endothelial cell co-culture, 3D gel model

OBJECTIVES

The aim of this study was to investigate gene expressions of growth factors for angiogenesis, in a three-dimensional (3D) gel populated with adipose-derived stromal cells (ASCs) and endothelial cells (ECs) in co-culture.

MATERIALS AND METHODS

The 3D gel, mixed with green fluorescent protein (GFP)-positive ASCs and DsRed-Express-positive ECs, 1:1 ratio, was established in vitro. The phenomenon of angiogenesis was observed using confocal microscopy. To detect gene expressions for growth factor proteins in both ASCs and ECs, transwell co-culture was used, and cell lysate samples were collected at 1, 3, 5 and 7 days. Semi-quantitative polymerase chain reaction (PCR) was conducted to quantify mRNA expressions of the growth factors.

RESULTS

Angiogenesis was first observed in the gels by 7 days post-implantation. Over this time in ECs, genes coding for VEGFA/B, IGF-1, HIF-1α, FGF-1/-2 and BMP-5/-7 significantly increased. Meanwhile in ASCs, genes coding for VEGFA/B, IGF-1, HIF-1α, FGF-1/-2 and BMP-6 also were significantly enhanced. In particular, increased amounts of IGF-1 and HIF-1α in both ECs and ASCs were prominent relative to other factors.

CONCLUSIONS

Contact co-culture with ASCs and ECs at 1:1 ratio, in the 3D gel promoted angiogenesis; non-contact co-culture further confirmed gene expressions for growth factors, VEGFA/B, IGF-1, HIF-1α and FGF-1/-2 in both ASCs and ECs; BMP-5/-7 in ECs and BMP-6 in ASCs were also confirmed. This establishment of growth factor expression seemed to be responsible for enhancement of angiogenesis. This indicates that these factors could be utilized as targets for engineered angiogenesis.

Interaction between osteoarthritic chondrocytes and adipose-derived stem cells is dependent on cell distribution in three-dimension and transforming growth factor-β3 induction

Stem cells hold great promise for treating cartilage degenerative diseases such as osteoarthritis (OA). The efficacy of stem cell-based therapy for cartilage repair is highly dependent on their interactions with local cells in the joint. This study aims at evaluating the interactions between osteoarthritic chondrocytes (OACs) and adipose-derived stem cells (ADSCs) using three dimensional (3D) biomimetic hydrogels. To examine the effects of cell distribution on such interactions, ADSCs and OACs were co-cultured in 3D using three co-culture models: conditioned medium (CM), bi-layered, and mixed co-culture with varying cell ratios. Furthermore, the effect of transforming growth factor (TGF)-β3 supplementation on ADSC-OAC interactions and the resulting cartilage formation was examined. Outcomes were analyzed using quantitative gene expression, cell proliferation, cartilage matrix production, and histology. TGF-β3 supplementation led to a substantial increase in cartilage matrix depositions in all groups, but had differential effects on OAC-ADSC interactions in different co-culture models. In the absence of TGF-β3, CM or bi-layered co-culture had negligible effects on gene expression or cartilage formation. With TGF-β3 supplementation, CM and bi-layered co-culture inhibited cartilage formation by both ADSCs and OACs. In contrast, a mixed co-culture with moderate OAC ratios (25% and 50%) resulted in synergistic interactions with enhanced cartilage matrix deposition and reduced catabolic marker expression. Our results suggested that the interaction between OACs and ADSCs is highly dependent on cell distribution in 3D and soluble factors, which should be taken into consideration when designing stem cell-based therapy for treating OA patients.

Adipose stem cell microbeads as production sources for chondrogenic growth factors

Microencapsulating stem cells in injectable microbeads can enhance delivery and localization, but their ability to act as growth factor production sources is still unknown. To address this concern, growth factor mRNA levels and production from alginate microbeads with encapsulated human adipose stem cells (ASC microbeads) cultured in both growth and chondrogenic media (GM and CM) were measured over a two week period. Human ASCs in microbeads were either commercially purchased (Lonza) or isolated from six human donors and compared to human ASCs on tissue culture polystyrene (TCPS). The effects of crosslinking and alginate compositions on growth factor mRNA levels and production were also determined. Secretion profiles of IGF-I, TGF-β3 and VEGF-A from commercial human ASC microbeads were linear and at a significantly higher rate than TCPS cultures over two weeks. For human ASCs derived from different donors, microencapsulation increased pthlh and both IGF-I and TGF-β3 secretion. CM decreased fgf2 and VEGF-A secretion from ASC microbeads derived from the same donor population. Crosslinking microbeads in BaCl₂ instead of CaCl₂ did not eliminate microencapsulation’s beneficial effects, but did decrease IGF-I production. Increasing the guluronate content of the alginate microbead increased IGF-I retention. Decreasing alginate molecular weight eliminated the effects microencapsulation had on increasing IGF-I secretion. This study demonstrated that microencapsulation can enhance chondrogenic growth factor production and that chondrogenic medium treatment can decrease angiogenic growth factor production from ASCs, making these cells a potential source for paracrine factors that can stimulate cartilage regeneration.

Formation of blood clot on biomaterial implants influences bone healing

The first step in bone healing is forming a blood clot at injured bones. During bone implantation, biomaterials unavoidably come into direct contact with blood, leading to a blood clot formation on its surface prior to bone regeneration. Despite both situations being similar in forming a blood clot at the defect site, most research in bone tissue engineering virtually ignores the important role of a blood clot in supporting healing. Dental implantology has long demonstrated that the fibrin structure and cellular content of a peri-implant clot can greatly affect osteoconduction and de novo bone formation on implant surfaces. This article reviews the formation of a blood clot during bone healing in relation to the use of platelet-rich plasma (PRP) gels. It is implicated that PRP gels are dramatically altered from a normal clot in healing, resulting in conflicting effect on bone regeneration. These results indicate that the effect of clots on bone regeneration depends on how the clots are formed. Factors that influence blood clot structure and properties in relation to bone healing are also highlighted. Such knowledge is essential for developing strategies to optimally control blood clot formation, which ultimately alter the healing microenvironment of bone. Of particular interest are modification of surface chemistry of biomaterials, which displays functional groups at varied composition for the purpose of tailoring blood coagulation activation, resultant clot fibrin architecture, rigidity, susceptibility to lysis, and growth factor release. This opens new scope of in situ blood clot modification as a promising approach in accelerating and controlling bone regeneration.

Adipose-derived stromal cells for osteoarticular repair: trophic function versus stem cell activity

The identification of multipotent adipose-derived stromal cells (ASC) has raised hope that tissue regeneration approaches established with bone-marrow-derived stromal cells (BMSC) can be reproduced with a cell-type that is far more accessible in large quantities. Recent detailed comparisons, however, revealed subtle functional differences between ASC and BMSC, stressing the concept of a common mesenchymal progenitor existing in a perivascular niche across all tissues. Focussing on bone and cartilage repair, this review summarises recent in vitro and in vivo studies aiming towards tissue regeneration with ASC. Advantages of good accessibility, high yield and superior growth properties are counterbalanced by an inferiority of ASC to form ectopic bone and stimulate long-bone healing along with their less pronounced osteogenic and angiogenic gene expression signature. Hence, particular emphasis is placed on establishing whether stem cell activity of ASC is so far proven and relevant for successful osteochondral regeneration, or whether trophic activity may largely determine therapeutic outcome.

Concise review: unraveling stem cell cocultures in regenerative medicine: which cell interactions steer cartilage regeneration and how?

Cartilage damage and osteoarthritis (OA) impose an important burden on society, leaving both young, active patients and older patients disabled and affecting quality of life. In particular, cartilage injury not only imparts acute loss of function but also predisposes to OA. The increase in knowledge of the consequences of these diseases and the exponential growth in research of regenerative medicine have given rise to different treatment types. Of these, cell-based treatments are increasingly applied because they have the potential to regenerate cartilage, treat symptoms, and ultimately prevent or delay OA. Although these approaches give promising results, they require a costly in vitro cell culture procedure. The answer may lie in single-stage procedures that, by using cell combinations, render in vitro expansion redundant. In the last two decades, cocultures of cartilage cells and a variety of (mesenchymal) stem cells have shown promising results as different studies report cartilage regeneration in vitro and in vivo. However, there is considerable debate regarding the mechanisms and cellular interactions that lead to chondrogenesis in these models. This review, which included 52 papers, provides a systematic overview of the data presented in the literature and tries to elucidate the mechanisms that lead to chondrogenesis in stem cell cocultures with cartilage cells. It could serve as a basis for research groups and clinicians aiming at designing and implementing combined cellular technologies for single-stage cartilage repair and treatment or prevention of OA.

Concise review: unraveling stem cell cocultures in regenerative medicine: which cell interactions steer cartilage regeneration and how?

Cartilage damage and osteoarthritis (OA) impose an important burden on society, leaving both young, active patients and older patients disabled and affecting quality of life. In particular, cartilage injury not only imparts acute loss of function but also predisposes to OA. The increase in knowledge of the consequences of these diseases and the exponential growth in research of regenerative medicine have given rise to different treatment types. Of these, cell-based treatments are increasingly applied because they have the potential to regenerate cartilage, treat symptoms, and ultimately prevent or delay OA. Although these approaches give promising results, they require a costly in vitro cell culture procedure. The answer may lie in single-stage procedures that, by using cell combinations, render in vitro expansion redundant. In the last two decades, cocultures of cartilage cells and a variety of (mesenchymal) stem cells have shown promising results as different studies report cartilage regeneration in vitro and in vivo. However, there is considerable debate regarding the mechanisms and cellular interactions that lead to chondrogenesis in these models. This review, which included 52 papers, provides a systematic overview of the data presented in the literature and tries to elucidate the mechanisms that lead to chondrogenesis in stem cell cocultures with cartilage cells. It could serve as a basis for research groups and clinicians aiming at designing and implementing combined cellular technologies for single-stage cartilage repair and treatment or prevention of OA.

Injectable alginate hydrogels for cell delivery in tissue engineering

Alginate hydrogels are extremely versatile and adaptable biomaterials, with great potential for use in biomedical applications. Their extracellular matrix-like features have been key factors for their choice as vehicles for cell delivery strategies aimed at tissue regeneration. A variety of strategies to decorate them with biofunctional moieties and to modulate their biophysical properties have been developed recently, which further allow their tailoring to the desired application. Additionally, their potential use as injectable materials offers several advantages over preformed scaffold-based approaches, namely: easy incorporation of therapeutic agents, such as cells, under mild conditions; minimally invasive local delivery; and high contourability, which is essential for filling in irregular defects. Alginate hydrogels have already been explored as cell delivery systems to enhance regeneration in different tissues and organs. Here, the in vitro and in vivo potential of injectable alginate hydrogels to deliver cells in a targeted fashion is reviewed. In each example, the selected crosslinking approach, the cell type, the target tissue and the main findings of the study are highlighted.

Stem cells catalyze cartilage formation by neonatal articular chondrocytes in 3D biomimetic hydrogels

Cartilage loss is a leading cause of disability among adults and effective therapy remains elusive. Neonatal chondrocytes (NChons) are an attractive allogeneic cell source for cartilage repair, but their clinical translation has been hindered by scarce donor availability. Here we examine the potential for catalyzing cartilage tissue formation using a minimal number of NChons by co-culturing them with adipose-derived stem cells (ADSCs) in 3D hydrogels. Using three different co-culture models, we demonstrated that the effects of co-culture on cartilage tissue formation are dependent on the intercellular distance and cell distribution in 3D. Unexpectedly, increasing ADSC ratio in mixed co-culture led to increased synergy between NChons and ADSCs, and resulted in the formation of large neocartilage nodules. This work raises the potential of utilizing stem cells to catalyze tissue formation by neonatal chondrocytes via paracrine signaling, and highlights the importance of controlling cell distribution in 3D matrices to achieve optimal synergy.

Activated platelet-rich plasma improves adipose-derived stem cell transplantation efficiency in injured articular cartilage

INTRODUCTION

Adipose-derived stem cells (ADSCs) have been isolated, expanded, and applied in the treatment of many diseases. ADSCs have also been used to treat injured articular cartilage. However, there is controversy regarding the treatment efficiency. We considered that ADSC transplantation with activated platelet-rich plasma (PRP) may improve injured articular cartilage compared with that of ADSC transplantation alone. In this study, we determined the role of PRP in ADSC transplantation to improve the treatment efficiency.

METHODS

ADSCs were isolated and expanded from human adipose tissue. PRP was collected and activated from human peripheral blood. The effects of PRP were evaluated in vitro and in ADSC transplantation in vivo. In vitro, the effects of PRP on ADSC proliferation, differentiation into chondrogenic cells, and inhibition of angiogenic factors were investigated at three concentrations of PRP (10%, 15% and 20%). In vivo, ADSCs pretreated with or without PRP were transplanted into murine models of injured articular cartilage.

RESULTS

PRP promoted ADSC proliferation and differentiation into chondrogenic cells that strongly expressed collagen II, Sox9 and aggrecan. Moreover, PRP inhibited expression of the angiogenic factor vascular endothelial growth factor. As a result, PRP-pretreated ADSCs improved healing of injured articular cartilage in murine models compared with that of untreated ADSCs.

CONCLUSION

Pretreatment of ADSCs with PRP is a simple method to efficiently apply ADSCs in cartilage regeneration. This study provides an important step toward the use of autologous ADSCs in the treatment of injured articular cartilage.

Controlled release of rat adipose-derived stem cells from alginate microbeads

Cell-based therapies have potential for tissue regeneration but poor delivery methods lead to low viability or dispersal of cells from target sites, limiting clinical utility. Here, we developed a degradable and injectable hydrogel to deliver stem cells for bone regeneration. Alginate microbeads <200 μm are injectable, persist at implantation sites and contain viable cells, but do not readily degrade in-vivo. We hypothesized that controlled release of rat adipose-derived stem cells (ASCs) from alginate microbeads can be achieved by incorporating alginate-lyase in the hydrogel. Microbeads were formed using high electrostatic potential. Controlled degradation was achieved through direct combination of alginate-lyase and alginate at 4 °C. Results showed that microbead degradation and cell release depended on the alginate-lyase to alginate ratio. Viability of released cells ranged from 87% on day 2 to 71% on day 12. Monolayer cultures of released ASCs grown in osteogenic medium produced higher levels of osteocalcin and similar levels of other soluble factors as ASCs that were neither previously encapsulated nor exposed to alginate-lyase. Bmp2, Fgf2, and Vegfa mRNA in released cells were also increased. Thus, this delivery system allows for controlled release of viable cells and can modulate their downstream osteogenic factor production.

Adipose-derived stem cells for cartilage regeneration--moving towards clinical applicability

Despite multiple methods of treatment and a wealth of research in the field of regenerative medicine focusing on cartilage defects, the management of cartilage injuries remains a challenge. A recent study by Van Pham and colleagues proposes a method for preconditioning autologous adipose-derived stem cells. Their study offers evidence about the increased proliferative and chondrogenetic capabilities of platelet-rich plasma-treated adipose-derived stem cells and the increased efficiency of these in treating articular cartilage defects in mice. Even though the method needs further elaboration and the composition of the repair tissue requires investigation, the results are promising for the design of clinically acceptable cell therapies aimed at cartilage regeneration.