Articular cartilage-derived cells hold a strong osteogenic differentiation potential in comparison to mesenchymal stem cells in vitro

Harnessing knee joint resident mesenchymal stem cells in cartilage tissue engineering

Osteoarthritis (OA) is a widespread clinical disease characterized by cartilage degeneration in middle-aged and elderly people. Currently, there is no effective treatment for OA apart from total joint replacement in advanced stages. Mesenchymal stem cells (MSCs) are a type of adult stem cell with diverse differentiation capabilities and immunomodulatory potentials. MSCs are known to effectively regulate the cartilage microenvironment, promote cartilage regeneration, and alleviate OA symptoms. As a result, they are promising sources of cells for OA therapy. Recent studies have revealed the presence of resident MSCs in synovial fluid, synovial membrane, and articular cartilage, which can be collected as knee joint-derived MSCs (KJD-MSC). Several preclinical and clinical studies have demonstrated that KJD-MSCs have great potential for OA treatment, whether applied alone, in combination with biomaterials, or as exocrine MSCs. In this article, we will review the characteristics of MSCs in the joints, including their cytological characteristics, such as proliferation, cartilage differentiation, and immunomodulatory abilities, as well as the biological function of MSC exosomes. We will also discuss the use of tissue engineering in OA treatment and introduce the concept of a new generation of stem cell-based tissue engineering therapy, including the use of engineering, gene therapy, and gene editing techniques to create KJD-MSCs or KJD-MSC derivative exosomes with improved functionality and targeted delivery. These advances aim to maximize the efficiency of cartilage tissue engineering and provide new strategies to overcome the bottleneck of OA therapy. STATEMENT OF SIGNIFICANCE: This research will provide new insights into the medicinal benefit of Joint resident Mesenchymal Stem Cells (MSCs), specifically on its cartilage tissue engineering ability. Through this review, the community will further realize promoting joint resident mesenchymal stem cells, especially cartilage progenitor/MSC-like progenitor cells (CPSC), as a preventive measure against osteoarthritis and cartilage injury. People and medical institutions may also consider cartilage derived MSC as an alternative approach against cartilage degeneration. Moreover, the discussion presented in this study will convey valuable information for future research that will explore the medicinal benefits of cartilage derived MSC.

Senescent chondrogenic progenitor cells derived from articular cartilage of knee osteoarthritis patients contributes to senescence-associated secretory phenotype via release of IL-6 and IL-8

OBJECTIVES

Despite the presence of chondrogenic progenitor cells (CPCs) in knee osteoarthritis patients they are unable to repair the damaged cartilage. This study aimed to evaluate the oxidative stress, cellular senescence, and senescence-associated secretory phenotype (SASP) in the CPCs derived from osteoarthritic cartilage and compare with the CPCs of healthy articular cartilage.

METHODS

Isolated CPCs were characterized based on phenotypic expression of stem cell markers, clonogenicity, and tri-lineage differentiation assay. Production of ROS was measured using DCFDA assay. Cellular senescence in CPCs was assessed by senescence-associated beta-galactosidase assay and expression of senescence markers at the gene level using real-time PCR. Morphological features associated with senescent OA-CPCs were studied using scanning electron microscopy. To study SASP, the production of inflammatory cytokines was assessed in the culture supernatant using a flow-cytometer based cytometric bead array.

RESULTS

OA-CPCs exhibited elevated ROS levels along with a relatively high percentage of senescent cells compared to non-OA CPCs, and a positive correlation exists between ROS production and senescence. The morphological assessment of senescent CPCs revealed increased cell size and multiple nuclei in senescent OA-CPCs. These results were further validated by elevated expression of senescence genes p16, p21, and p53. Additionally, culture supernatant of senescent OA-CPCs expressed IL-6 and IL-8 cytokines indicative of SASP.

CONCLUSIONS

Despite exhibiting similar expression of stem cell markers and clonogenicity, CPCs undergo oxidative stress in diseased knee joint leading to increased production of intracellular ROS in chondrogenic progenitor cells that support cellular senescence. Further, senescence in OA-CPCs is mediated via the release of pro-inflammatory cytokines, IL-6 and IL-8.

The clinical potential of articular cartilage-derived progenitor cells: a systematic review

Over the past two decades, evidence has emerged for the existence of a distinct population of endogenous progenitor cells in adult articular cartilage, predominantly referred to as articular cartilage-derived progenitor cells (ACPCs). This progenitor population can be isolated from articular cartilage of a broad range of species, including human, equine, and bovine cartilage. In vitro, ACPCs possess mesenchymal stromal cell (MSC)-like characteristics, such as colony forming potential, extensive proliferation, and multilineage potential. Contrary to bone marrow-derived MSCs, ACPCs exhibit no signs of hypertrophic differentiation and therefore hold potential for cartilage repair. As no unique cell marker or marker set has been established to specifically identify ACPCs, isolation and characterization protocols vary greatly. This systematic review summarizes the state-of-the-art research on this promising cell type for use in cartilage repair therapies. It provides an overview of the available literature on endogenous progenitor cells in adult articular cartilage and specifically compares identification of these cell populations in healthy and osteoarthritic (OA) cartilage, isolation procedures, in vitro characterization, and advantages over other cell types used for cartilage repair. The methods for the systematic review were prospectively registered in PROSPERO (CRD42020184775).

Dose-Dependent Effects of Platelet-Rich Plasma Powder on Chondrocytes In Vitro

BACKGROUND

Platelet-rich plasma (PRP) is widely used in sports medicine. However, neither preparation nor parameters for clinical application, such as concentration, timing, and number of applications, are standardized, making research and clinical utilization challenging.

PURPOSE

To investigate the effect of varying doses of PRP powder in terms of different concentrations, timing, and number of applications on human chondrocytes in a reproducible cell culture model.

STUDY DESIGN

Controlled laboratory study.

METHODS

A standardized lyophilized platelet growth factor preparation (PRP powder) was used to stimulate human chondrocytes. Chondrocytes were cultivated for 2 weeks with different stimulation frequencies (2×, 3×, 6×) and different concentrations of PRP powders (0.5%, 1%, 5%). Cell proliferation and metabolic cell activity were analyzed on days 7 and 14. Phenotypic changes were visualized through live-dead staining. Chondrogenic differentiation was quantified with enzyme-linked immunosorbent assay to assess the synthesis of procollagen types 1 and 2. Furthermore, sulfated proteoglycans and glycosaminoglycans were analyzed.

RESULTS

Human chondrocytes exhibited a significant dose- and time-dependent increase after 14 days in cell number (1% and 5% PRP powder vs unstimulated control: 7.95- and 15.45-fold increase, respectively; 2× vs 6× stimulation with 5% PRP powder: 4.00-fold increase) and metabolic cell activity (1% and 5% PRP powder vs unstimulated control: 3.27-fold and 3.58-fold change, respectively). Furthermore, cells revealed a significant increase in the amount of bone-specific procollagen type 1 (14 days, 1.94-fold) and sulfated glycosaminoglycans (14 days, 2.69-fold); however, no significant change was observed in the amount of cartilage-specific collagen type 2.

CONCLUSION

We showed that chondrocytes exhibit a significant dose- and time-dependent increase in cell number and metabolic cell activity. The standardized use of growth factor concentrates in cell culture models can contribute to clinical knowledge in terms of dosage and timing of PRP applications.

CLINICAL RELEVANCE

Problems with PRP, such as the absence of standardization, lack of consistency among studies, and unknown dosage, could be solved by using characterized PRP powder made by pooling and lyophilizing multiple platelet concentrates. The innovative PRP powder generates new possibilities for PRP research, as well as for the treatment of patients.

TGF-ß1 Induces Changes in the Energy Metabolism of White Adipose Tissue-Derived Human Adult Mesenchymal Stem/Stromal Cells In Vitro

Adipose tissue plays an active role in the regulation of the body’s energy balance. Mesenchymal stem/stromal cells from adipose tissue (adMSC) are the precursor cells for repair and adipogenesis. Since the balance of the differentiation state of adipose tissue-resident cells is associated with the development of various diseases, the examination of the regulation of proliferation and differentiation of adMSC might provide new therapeutic targets. Transforming growth factor-β1 (TGF-ß1) is synthetized by many cell types and is involved in various biological processes. Here, we investigated the effects of different concentrations of TGF-ß1 (1–10 ng/mL) on adMSC proliferation, metabolic activity, and analyzed the gene expression data obtained from DNA microarrays by bioinformatics. TGF-ß1 induced the concentration- and time-dependent increase in the cell number of adMSC with simultaneously unchanged cell cycle distributions. The basal oxygen consumption rates did not change significantly after TGF-ß1 exposure. However, glycolytic activity was significantly increased. The gene expression analysis identified 3275 differentially expressed genes upon exposure to TGF-ß1. According to the pathway enrichment analyses, they also included genes associated with energy metabolism. Thus, it was shown that TGF-ß1 induces changes in the energy metabolism of adMSC. Whether these effects are of relevance in vivo and whether they contribute to pathogenesis should be addressed in further examinations.

Genome-wide microRNA screening reveals miR-582-5p as a mesenchymal stem cell-specific microRNA in subchondral bone of the human knee joint

Emerging evidence suggests that microRNAs (miRNAs) may be pathologically involved in osteoarthritis (OA). Subchondral bone (SCB) sclerosis is accounted for the knee osteoarthritis (KOA) development and progression. In this study, we aimed to screen the miRNA biomarkers of KOA and investigated whether these miRNAs regulate the differentiation potential of mesenchymal stem cells (MSCs) and thus contributing to SCB. We identified 48 miRNAs in the blood samples in KOA patients (n = 5) through microarray expression profiling detection. After validation with larger sample number, we confirmed hsa-miR-582-5p and hsa-miR-424-5p were associated with the pathology of SCB sclerosis. Target genes prediction and pathway analysis were implemented with online databases, indicating these two candidate miRNAs were closely related to the pathways of pluripotency of stem cells and pathology of OA. Surprisingly, mmu-miR-582-5p (homology of hsa-miR-582-5p) was downregulated in osteogenic differentiation and upregulated in adipogenic differentiation of mesenchymal progenitor C3H10T1/2 cells, whereas mmu-mir-322-5p (homology of hsa-miR-424-5p) showed no change through the in vitro study. Supplementing mmu-miR-582-5p mimics blocked osteogenic and induced adipogenic differentiation of C3H10T1/2 cells, whereas silencing of the endogenous mmu-miR-582-5p enhanced osteogenic and repressed adipogenic differentiation. Further mechanism studies showed that mmu-miR-582-5p was directly targeted to Runx2. Mutation of putative mmu-miR-582-5p binding sites in Runx2 3' untranslated region (3'UTR) could abolish the response of the 3'UTR-luciferase construct to mmu-miR-582-5p supplementation. Generally speaking, our data suggest that miR-582-5p is an important biomarker of KOA and is able to regulate osteogenic and adipogenic differentiation of MSCs via targeting Runx2. The study also suggests that miR-582-5p may play a crucial role in SCB sclerosis of human KOA.

In Vitro Analysis of the Differentiation Capacity of Postmortally Isolated Human Chondrocytes Influenced by Different Growth Factors and Oxygen Levels

OBJECTIVE

In the present in vitro study, we analyzed the chondrogenic differentiation capacity of human chondrocytes postmortally isolated from unaffected knee cartilage by the addition of transforming growth factor-β1 (TGF-β1) and/or insulin-like growth factor-1 (IGF-1) and different oxygen levels.

DESIGN

After 14 and 35 days, DNA concentrations and protein contents of Col1, Col2, aggrecan as well as glycosaminoglycans (GAGs) of chondrocytes cultivated as pellet cultures were analyzed. Additionally, expression rates of mesenchymal stem cell (MSC)-associated differentiation markers were assessed in monolayer cultures.

RESULTS

All cultivated chondrocytes were found to be CD29⁺/CD44⁺/CD105⁺/CD166⁺. Chondrocytic pellets stimulated with TGF-β1 showed enhanced synthesis rates of hyaline cartilage markers and reduced expression of the non-hyaline cartilage marker Col1 under hypoxic culture conditions.

CONCLUSIONS

Our results underline the substantial chondrogenic potential of human chondrocytes postmortally isolated from unaffected articular knee cartilage especially in case of TGF-β1 administration.

Energy metabolic capacities of human adipose-derived mesenchymal stromal cells in vitro and their adaptations in osteogenic and adipogenic differentiation

Mesenchymal stromal/stem cells (MSC) are important in tissue homeostasis and regeneration due to their ability for self-renewal and multipotent differentiation. Differentiation, as well as proliferation, requires adaptations in the cell metabolism. However, only few data exist concerning the energy metabolism of non-differentiating and differentiating MSC. In this study we compared capacities of major energy metabolic pathways of MSC from human adipose tissue (adMSC) in vitro in the non-differentiated state with those of osteogenically or adipogenically differentiating adMSC. To this end we quantified the proliferation and differentiation status of adMSC and analyzed maximum enzyme capacities and several enzyme isoforms of major energy metabolic pathways regarding their activity and gene expression. We could show that non-differentiating and osteogenic cultivation conditions induced proliferation and showed increasing capacities of the glycolytic marker enzyme phosphofructokinase as well as the marker enzyme of the pentose phosphate pathway glucose-6-phosphate dehydrogenase. Adipogenic stimulation, which was accompanied by the absence of proliferation, reduced the glycolytic capacity (e.g. decreased glyceraldehyde 3-phosphate dehydrogenase capacity) and induced an increase in mitochondrial enzyme capacities. These changes in energy metabolism might represent an adaptation of adMSC to the high energy demand during proliferation and to the specific cellular functions during osteogenic or adipogenic differentiation respectively.

Mesenchymal Stem/Progenitor Cells Derived from Articular Cartilage, Synovial Membrane and Synovial Fluid for Cartilage Regeneration: Current Status and Future Perspectives

Large articular cartilage defects remain an immense challenge in the field of regenerative medicine because of their poor intrinsic repair capacity. Currently, the available medical interventions can relieve clinical symptoms to some extent, but fail to repair the cartilaginous injuries with authentic hyaline cartilage. There has been a surge of interest in developing cell-based therapies, focused particularly on the use of mesenchymal stem/progenitor cells with or without scaffolds. Mesenchymal stem/progenitor cells are promising graft cells for tissue regeneration, but the most suitable source of cells for cartilage repair remains controversial. The tissue origin of mesenchymal stem/progenitor cells notably influences the biological properties and therapeutic potential. It is well known that mesenchymal stem/progenitor cells derived from synovial joint tissues exhibit superior chondrogenic ability compared with those derived from non-joint tissues; thus, these cell populations are considered ideal sources for cartilage regeneration. In addition to the progress in research and promising preclinical results, many important research questions must be answered before widespread success in cartilage regeneration is achieved. This review outlines the biology of stem/progenitor cells derived from the articular cartilage, the synovial membrane, and the synovial fluid, including their tissue distribution, function and biological characteristics. Furthermore, preclinical and clinical trials focusing on their applications for cartilage regeneration are summarized, and future research perspectives are discussed.

Decisive role of P42/44 mitogen-activated protein kinase in Δ9-tetrahydrocannabinol-induced migration of human mesenchymal stem cells

In past years, medical interest in Δ⁹-tetrahydrocannabinol (THC), the major psychoactive ingredient of the Cannabis plant, has been renewed due to the elucidation of the endocannabinoid system and diverse other receptor targets involved in biological cannabinoid effects. The present study therefore investigates the impact of THC on the migration of mesenchymal stem cells (MSCs) which are known to be involved in various regenerative processes such as bone healing. Using Boyden chamber assays, THC was found to increase the migration of adipose-derived MSCs. Migration by THC was almost completely suppressed by the CB₁ receptor antagonist AM-251 and to a lesser extent by the CB₂ receptor antagonist AM-630. By contrast, the TRPV1 antagonist capsazepine as well as the G protein-coupled receptor 55 (GRP55) agonist O-1602 did not significantly interfere with the promigratory effect of THC. Furthermore, increased migration by THC was fully suppressed by PD98059, an inhibitor of p42/44 mitogen-activated protein kinase (MAPK) activation, and was accompanied by a time-dependent activation of this pathway accordingly. In line with the migration data, additional inhibitor experiments pointed towards a decisive role of the CB₁ receptor in conferring THC-induced activation of p42/44 MAPK. Collectively, this study demonstrates THC to exert a promigratory effect on MSCs via a CB₁ receptor-dependent activation of p42/44 MAPK phosphorylation. This pathway may be involved in regenerative effects of THC and could be a target of pharmacological intervention.

CD146+ skeletal stem cells from growth plate exhibit specific chondrogenic differentiation capacity in vitro

Skeletal stem cells (SSCs) are a population of progenitor cells which give rise to postnatal skeletal tissues including bone, cartilage and bone marrow stroma, however not to adipose, haematopoietic or muscle tissue. Growth plate chondrocytes exhibit the ability of continuous proliferation and differentiation, which contributes to the continuous physiological growth. The growth plate has been hypothesized to contain SSCs which exhibit a desirable differentiation capacity to generate bone and cartilage. Due to the heterogeneity of the growth plate chondrocytes, SSCs in the growth plate are not well studied. The present study used cluster of differentiation (CD)146 and CD105 as markers to isolate purified SSCs. CD105+ SSCs and CD146+ SSCs were isolated using a magnetic activated cell sorting method. To quantitatively investigate the proliferation and differentiation ability, the colony-forming efficiency (CFE) and multi‑lineage differentiation capacity of CD105+ SSCs and CD146+ SSCs were compared with unsorted cells and adipose-derived stem cells (ASCs). It was revealed that CD105+ and CD146+ subpopulations represented subsets of SSCs which generated chondrocytes and osteocytes, however not adipocytes. Compared with CD105+ subpopulations and ASCs, the CD146+ subpopulation exhibited a greater CFE and continuous high chondrogenic differentiation capacity in vitro. Therefore, the present study suggested that the CD146+ subpopulation represented a chondrolineage‑restricted subpopulation of SSCs and may therefore act as a valuable cell source for cartilage regeneration.

CD105+-mesenchymal stem cells migrate into osteoarthritis joint: An animal model

Mesenchymal stem cells are being the focus of connective tissue technology and regenerative medicine, presenting a good choice cell source for improving old and well recognized techniques of cartilage defect repair. For instance, the autologous chondrocyte transplantation using new concepts of regenerative medicine. The present study investigated the risk of xenogenicity of human synovial membrane-derived MSCs, injected into the monkeys using intravenous and intra-articular administration. The animal models used were adult monkeys Rhesus which had been injured into the left knee to create an Osteoarthritis (OA) animal model. CD105+-MSCs were injected twice into the OA monkeys with an interval of one week between them. The animals were euthanized one month after treatment. Immunohistochemistry analysis of different organs: spleen, heart, fat, liver, gut, pancreas, lung, skeletal muscle and kidney from the animals revealed that CD105+-MSCs migrated towards the injured knee joint. MSCs naive were found statistically significant increased in the injured knee in front of healthy one. CD105+-MSCs were negatives for CD68 and the area where CD105+-MSCs were found presented SDF-1 increased levels in front of healthy knee. We concluded that a characterized MSCs subset could be a safe alternative for cell therapy in clearly localized pathologies.

Analysis of migration rate and chemotaxis of human adipose-derived mesenchymal stem cells in response to LPS and LTA in vitro

Mesenchymal stem cells (MSC) are able to stimulate the regeneration of injured tissue. Since bacterial infections are common complications in wound healing, bacterial pathogens and their components come into direct contact with MSC. The interaction with bacterial structures influences the proliferation, differentiation and migratory activity of the MSC, which might be of relevance during regeneration. Studies on MSC migration in response to bacterial components have shown different results depending on the cell type. Here, we analyzed the migration rate and chemotaxis of human adipose-derived MSC (adMSC) in response to the basic cell-wall components lipopolysaccharide (LPS) of Gram-negative bacteria and lipoteichoic acid (LTA) of Gram-positive bacteria in vitro. To this end, we used transwell and scratch assays, as well as a specific chemotaxis assay combined with live-cell imaging. We found no significant influence of LPS or LTA on the migration rate of adMSC in transwell or scratch assays. Furthermore, in the µ-slide chemotaxis assay, the stimulation with LPS did not exert any chemotactic effect on adMSC.

Isolation and differentiation potential of human mesenchymal stem cells from adipose tissue harvested by water jet-assisted liposuction

BACKGROUND

In recent years the therapeutic application of extracted adipose tissue for autologous fat grafting and the application of adipose tissue-derived mesenchymal stem cells (adMSC) isolated thereof has progressed. Water-jet assisted liposuction (WAL) is 1 procedure for harvesting adipose tissue and provides a favorable aesthetic outcome combined with high tissue protection. Tissue aspirated by WAL has been successfully applied in grafting procedures.

OBJECTIVES

The aims of this study were to confirm the tissue viability and to understand the abundance and mesenchymal differentiation capacity of stem cells within the tissue.

METHODS

We analyzed tissue integrity of WAL tissue particles via fluorescence microscopy. The adMSC content was determined by isolating the cells from the tissue. The mesenchymal differentiation capacity was confirmed with cytochemical staining methods.

RESULTS

The stromal vascular fraction of WAL tissue showed high viability and contained an average of 2.6 × 105 CD34-positive cells per milliliter of tissue. Thus WAL tissue contains a high number of stem cells. Furthermore adMSC isolated from WAL tissue showed typical mesenchymal differentiation potential.

CONCLUSIONS

WAL of adipose tissue is well suited for autologous fat grafting because it retains tissue viability. Furthermore it is a valid source for the subsequent isolation of adMSC with multipotent differentiation potential.

LEVEL OF EVIDENCE

3 Therapeutic.

Endochondral ossification model system: designed cell fate of human epiphyseal chondrocytes during long-term implantation

The aim of this study is to establish a recapitulation system of human endochondral ossification as a paradigm of developmental engineering. Chondrocytes were isolated from the epiphyseal cartilage of the supernumerary digits of infants with polydactyly. In vivo studies showed that implanted chondrocytes exhibited cartilaginous regeneration over a short period of time and subsequent endochondral ossification with a marrow cavity. Tracing studies revealed that cells of donor origin at the periphery of the cartilage migrated into the center of the cartilage and transformed into osteoblasts, adipocytes, and endothelial cells. Bone marrow was formed through anastomosis with the recipient endothelial system at 13 weeks, and from the migration of recipient hematopoietic cells at 50 weeks. This study provides a human endochondral ossification model system with transdifferentiation of the donor cells at the periphery of the cartilage. J. Cell. Physiol. 230: 1376-1388, 2015. © 2015 Wiley Periodicals, Inc., A Wiley Company.

Isolation, identification and differentiation of human embryonic cartilage stem cells

We isolated human embryonic cartilage stem cells (hECSCs), a novel stem cell population, from the articular cartilage of eight-week-old human embryos. These stem cells demonstrated a marker expression pattern and differentiation potential intermediate to those of human embryonic stem cells (hESCs) and human adult stem cells (hASCs). hECSCs expressed markers associated with both hESCs (OCT4, NANOG, SOX2, SSEA-3 and SSEA-4) and human adult stem cells (hASCs) (CD29, CD44, CD90, CD73 and CD10). These cells also differentiated into adipocytes, osteoblasts, chondrocytes, neurons and islet-like cells under specific inducing conditions. We identified N(6), 2'-O-dibutyryl cyclic adenosine 3':5'-monophosphate (Bt2cAMP) as an inducer of chondrogenic differentiation in hECSCs. Similar results using N(6), 2'-O-dibutyryl cyclic adenosine 3':5'-monophosphate (Bt2cAMP) were obtained for two other types of human embryonic tissue-derived stem cells, human embryonic hepatic stem cells (hEHSCs) and human embryonic amniotic fluid stem cells (hEASCs), both of which exhibited a marker expression pattern similar to that of hECSCs. The isolation of hECSCs and the discovery that N(6), 2'-O-dibutyryl cyclic adenosine 3':5'-monophosphate (Bt2cAMP) induces chondrogenic differentiation in different stem cell populations might aid the development of strategies in tissue engineering and cartilage repair.

Long-term tumor necrosis factor treatment induces NFκB activation and proliferation, but not osteoblastic differentiation of adipose tissue-derived mesenchymal stem cells in vitro

The pro-inflammatory cytokine tumor necrosis factor (TNF) is well known to induce differentiation of bone matrix-resorbing osteoclasts from hematopoietic stem cells. However, the impact of TNF on differentiation of bone matrix-forming osteoblasts from mesenchymal stem cells (MSC) was only fragmentarily studied so far. Therefore, we investigated what impact long-term TNF treatment has on osteoblastic differentiation of MSC isolated from the adipose tissue (ASC) in vitro. In summary, we found continuous TNF exposure to induce the nuclear factor of kappa B pathway in ASC as well as secretion of the pro-inflammatory chemokine interleukin 8, but not the mitogen-activated protein kinase and the apoptosis pathway in ASC. Moreover, TNF neither induced nor inhibited osteoblastic differentiation of ASC, but strongly increased their proliferation rate. In that manner, pro-inflammatory conditions in vivo may generate significantly increased numbers of progenitor cells, and ASC especially, in conjunction with external stimuli, may contribute to the events of ectopic ossification observed in chronic inflammatory diseases. The substantiation of the translation of our in vitro findings to the disease context encourages further in vivo studies.

Gelatin-Based Hydrogels Promote Chondrogenic Differentiation of Human Adipose Tissue-Derived Mesenchymal Stem Cells In Vitro

Due to the weak regeneration potential of cartilage, there is a high clinical incidence of articular joint disease, leading to a strong demand for cartilaginous tissue surrogates. The aim of this study was to evaluate a gelatin-based hydrogel for its suitability to support chondrogenic differentiation of human mesenchymal stem cells. Gelatin-based hydrogels are biodegradable, show high biocompatibility, and offer possibilities to introduce functional groups and/or ligands. In order to prove their chondrogenesis-supporting potential, a hydrogel film was developed and compared with standard cell culture polystyrene regarding the differentiation behavior of human mesenchymal stem cells. Cellular basis for this study were human adipose tissue-derived mesenchymal stem cells, which exhibit differentiation potential along the adipogenic, osteogenic and chondrogenic lineage. The results obtained show a promotive effect of gelatin-based hydrogels on chondrogenic differentiation of mesenchymal stem cells in vitro and therefore encourage subsequent in vivo studies.