PTH stimulated growth and decreased Col-X deposition are phosphotidylinositol-3,4,5 triphosphate kinase and mitogen activating protein kinase dependent in avian sterna

Suramin enhances chondrogenic properties by regulating the p67phox/PI3K/AKT/SOX9 signalling pathway

Aims

Autologous chondrocyte implantation (ACI) is a promising treatment for articular cartilage degeneration and injury; however, it requires a large number of human hyaline chondrocytes, which often undergo dedifferentiation during in vitro expansion. This study aimed to investigate the effect of suramin on chondrocyte differentiation and its underlying mechanism.

Methods

Porcine chondrocytes were treated with vehicle or various doses of suramin. The expression of collagen, type II, alpha 1 (COL2A1), aggrecan (ACAN); COL1A1; COL10A1; SRY-box transcription factor 9 (SOX9); nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX); interleukin (IL)-1β; tumour necrosis factor alpha (TNFα); IL-8; and matrix metallopeptidase 13 (MMP-13) in chondrocytes at both messenger RNA (mRNA) and protein levels was determined by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) and western blot. In addition, the supplementation of suramin to redifferentiation medium for the culture of expanded chondrocytes in 3D pellets was evaluated. Glycosaminoglycan (GAG) and collagen production were evaluated by biochemical analyses and immunofluorescence, as well as by immunohistochemistry. The expression of reactive oxygen species (ROS) and NOX activity were assessed by luciferase reporter gene assay, immunofluorescence analysis, and flow cytometry. Mutagenesis analysis, Alcian blue staining, reverse transcriptase polymerase chain reaction (RT-PCR), and western blot assay were used to determine whether p67^phox was involved in suramin-enhanced chondrocyte phenotype maintenance.

Results

Suramin enhanced the COL2A1 and ACAN expression and lowered COL1A1 synthesis. Also, in 3D pellet culture GAG and COL2A1 production was significantly higher in pellets consisting of chondrocytes expanded with suramin compared to controls. Surprisingly, suramin also increased ROS generation, which is largely caused by enhanced NOX (p67^phox) activity and membrane translocation. Overexpression of p67^phox but not p67^phoxAD (deleting amino acid (a.a) 199 to 212) mutant, which does not support ROS production in chondrocytes, significantly enhanced chondrocyte phenotype maintenance, SOX9 expression, and AKT (S473) phosphorylation. Knockdown of p67^phox with its specific short hairpin (sh) RNA (shRNA) abolished the suramin-induced effects. Moreover, when these cells were treated with the phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) inhibitor LY294002 or shRNA of AKT1, p67^phox-induced COL2A1 and ACAN expression was significantly inhibited.

Conclusion

Suramin could redifferentiate dedifferentiated chondrocytes dependent on p67^phox activation, which is mediated by the PI3K/AKT/SOX9 signalling pathway.

Cite this article: Bone Joint Res 2022;11(10):723–738.

Supplementation of articular cartilage-derived chondroprogenitors with bone morphogenic protein-9 enhances chondrogenesis without affecting hypertrophy

INTRODUCTION

Chondroprogenitors (CPCs) have emerged as a promising cellular therapy for cartilage-related pathologies due to their inherent primed chondrogenic potential. Studies report that the addition of growth factors such as parathyroid hormone (PTH) and Bone Morphogenic Protein (BMP) enhance the chondroinducive potential in chondrocytes and mesenchymal stem cells. This study evaluated if supplementation of the standard culture medium for cell expansion with 1-34 PTH and BMP-9 would enhance the chondrogenic potential of CPCs and reduce their hypertrophic tendency.

METHODS

Human chondrocytes were isolated from patients undergoing total knee replacement for osteoarthritis (n = 3). Following fibronectin adhesion assay, passage 1 CPCs were divided and further expanded under three culture conditions (a) control, i.e., cells continued under standard culture conditions, (b) 1-34 PTH group, additional intermittent 6 h exposure with 1-34 PTH and (c) BMP-9 group, additional BMP-9 during culture expansion. All the groups were evaluated for population-doubling, cell cycle analysis, surface marker and gene expression for chondrogenesis, hypertrophy, multilineage differentiation and GAG (glycosaminoglycan)/DNA following chondrogenic differentiation.

RESULTS

Concerning growth kinetics, the BMP-9 group exhibited a significantly lower S-phase and population-doubling when compared to the other two groups. Qualitative analysis for chondrogenic potential (Alcian blue, Safranin O staining and Toluidine blue for GAG) revealed that the BMP-9 group exhibited the highest uptake. The BMP-9 group also showed significantly higher COL2A1 expression than the control group, with no change in the hypertrophy marker expression.

CONCLUSION

BMP-9 can potentially be used as an additive for CPCs expansion, to enhance their chondrogenic potential without affecting their low hypertrophic tendency. The mitigating effects of 1-34PTH on hypertrophy would benefit further investigation when used in combination with BMP-9 to enhance chondrogenesis whilst reducing hypertrophy.

The Protective Effects of Parathyroid Hormone (1-34) on Cartilage and Subchondral Bone Through Down-Regulating JAK2/STAT3 and WNT5A/ROR2 in a Collagenase-Induced Osteoarthritis Mouse Model

OBJECTIVE

To assess the effects of PTH (1-34) on bone and cartilage metabolism in a collagenase-induced mouse model of osteoarthritis (OA) and examine whether PTH (1-34) affects the expression of JAK2/STAT3 and WNT5A/ROR2 in this process.

METHODS

Eighteen 12-week-old male C57Bl/6 mice were randomly assigned into three groups as follows: sham group (Group A), the collagenase + saline injection group (Group B), and the collagenase + PTH (1-34) treatment group (Group C). Collagenase was injected (intra-articular) into the knee joint of Group B and C. The PTH (1-34)-treatment was started at 6 weeks after the operation and lasted for 6 weeks. Cartilage pathology was evaluated by gross visual, histological, and immunohistochemical assessments. Subchondral bone was evaluated by microcomputed tomography (micro-CT) and immunohistochemical analyses.

RESULTS

The OARSI macroscopic and microscopic scores of Group B were higher than those of Group A (P = 0.026; P = 0.002, respectively). Group C showed statistically significant differences in macroscopic and microscopic scores from Group B (P = 0.041; P = 0.008, respectively). The results showed that the Col-II and AGG expression levels in the cartilage tissue were significantly lower in Group B than Group A (P < 0.001; P = 0.008, respectively). The Col-II and AGG expression levels were significantly higher in Group C than Group B (P = 0.009; P = 0.014, respectively). MMP-13, ADAMTS-4, Caspase-3, P53, and Bax expression levels were significantly higher in Group B than the Group A (P < 0.001; P < 0.001; P = 0.04; P < 0.001; P = 0.005, respectively); however, the cartilage tissue in Group C showed significantly less ADAMTS-4, MMP-13, Caspase-3, P53, and Bax expression than Group B (P < 0.001, P < 0.001, P = 0.044; P = 0.002; P = 0.005, respectively). Over-expressed JAK2/STAT3 and WNT5A/ROR2 were observed in both cartilage and subchondral bone in this model; however, these changes were prevented by PTH (1-34) treatment. These parameters (bone mineral density, bone volume ratio, trabecular bone pattern factor, and structure model index) of micro-CT indicated subchondral bone loss and architecture changes in Group B, but improvements in these parameters in Group C.

CONCLUSIONS

PTH (1-34) exhibits protective effects on both cartilage and subchondral bone in a collagenase-induced OA mouse model, and it may be involved in down-regulating the expression of JAK2/STAT3 and WNT5A/ROR2.

Parathyroid hormone (1-34) ameliorates cartilage degeneration and subchondral bone deterioration in collagenase-induced osteoarthritis model in mice

Aims

Parathyroid hormone (PTH) (1-34) exhibits potential in preventing degeneration in both cartilage and subchondral bone in osteoarthritis (OA) development. We assessed the effects of PTH (1-34) at different concentrations on bone and cartilage metabolism in a collagenase-induced mouse model of OA and examined whether PTH (1-34) affects the JAK2/STAT3 signalling pathway in this process.

Methods

Collagenase-induced OA was established in C57Bl/6 mice. Therapy with PTH (1-34) (10 μg/kg/day or 40 μg/kg/day) was initiated immediately after surgery and continued for six weeks. Cartilage pathology was evaluated by gross visual, histology, and immunohistochemical assessments. Cell apoptosis was analyzed by TUNEL staining. Microcomputed tomography (micro-CT) was used to evaluate the bone mass and the microarchitecture in subchondral bone.

Results

Enhanced matrix catabolism, increased apoptosis of chondrocytes in cartilage, and overexpressed JAK2/STAT3 and p-JAK2/p-STAT3 were observed in cartilage in this model. All of these changes were prevented by PTH (1-34) treatment, with no significant difference between the low-dose and high-dose groups. Micro-CT analysis indicated that bone mineral density (BMD), bone volume/trabecular volume (BV/TV), and trabecular thickness (Tb.Th) levels were significantly lower in the OA group than those in the Sham, PTH 10 μg, and PTH 40 μg groups, but these parameters were significantly higher in the PTH 40 μg group than in the PTH 10 μg group.

Conclusion

Intermittent administration of PTH (1-34) exhibits protective effects on both cartilage and subchondral bone in a dose-dependent manner on the latter in a collagenase-induced OA mouse model, which may be involved in regulating the JAK2/STAT3 signalling pathway.

Cite this article: Bone Joint Res 2020;9(10):675–688.

Intermittent parathyroid hormone (1-34) supplementation of bone marrow stromal cell cultures may inhibit hypertrophy, but at the expense of chondrogenesis

Background

Bone marrow stromal cells (BMSC) have promise in cartilage tissue engineering, but for their potential to be fully realised, the propensity to undergo hypertrophy must be mitigated. The literature contains diverging reports on the effect of parathyroid hormone (PTH) on BMSC differentiation. Cartilage tissue models can be heterogeneous, confounding efforts to improve media formulations.

Methods

Herein, we use a novel microwell platform (the Microwell-mesh) to manufacture hundreds of small-diameter homogeneous micro-pellets and use this high-resolution assay to quantify the influence of constant or intermittent PTH(1–34) medium supplementation on BMSC chondrogenesis and hypertrophy. Micro-pellets were manufactured from 5000 BMSC each and cultured in standard chondrogenic media supplemented with (1) no PTH, (2) intermittent PTH, or (3) constant PTH.

Results

Relative to control chondrogenic cultures, BMSC micro-pellets exposed to intermittent PTH had reduced hypertrophic gene expression following 1 week of culture, but this was accompanied by a loss in chondrogenesis by the second week of culture. Constant PTH treatment was detrimental to chondrogenic culture.

Conclusions

This study provides further clarity on the role of PTH on chondrogenic differentiation in vitro and suggests that while PTH may mitigate BMSC hypertrophy, it does so at the expense of chondrogenesis.

PTH decreases in vitro human cartilage regeneration without affecting hypertrophic differentiation

Regenerated cartilage formed after Autologous Chondrocyte Implantation may be of suboptimal quality due to postulated hypertrophic changes. Parathyroid hormone-related peptide, containing the parathyroid hormone sequence (PTHrP 1–34), enhances cartilage growth during development and inhibits hypertrophic differentiation of mesenchymal stromal cells (MSCs) and growth plate chondrocytes. This study aims to determine the possible anabolic and/or hypertrophic effect of PTH on human articular chondrocytes. Healthy human articular cartilage-derived chondrocytes (n = 6 donors) were cultured on type II collagen-coated transwells with/without 0.1 or 1.0 μM PTH from day 0, 9, or 21 until the end of culture (day 28). Extracellular matrix production, (pre)hypertrophy and PTH signaling were assessed by RT-qPCR and/or immunohistochemistry for collagen type I, II, X, RUNX2, MMP13, PTHR1 and IHH and by determining glycosaminoglycan production and DNA content. The Bern score assessed cartilage quality by histology. Regardless of the concentration and initiation of supplementation, PTH treatment significantly decreased DNA and glycosaminoglycan content and reduced the Bern score compared with controls. Type I collagen deposition was increased, whereas PTHR1 expression and type II collagen deposition were decreased by PTH supplementation. Expression of the (pre)hypertrophic markers MMP13, RUNX2, IHH and type X collagen were not affected by PTH. In conclusion, PTH supplementation to healthy human articular chondrocytes did not affect hypertrophic differentiation, but negatively influenced cartilage quality, the tissues’ extracellular matrix and cell content. Although PTH may be an effective inhibitor of hypertrophic differentiation in MSC-based cartilage repair, care may be warranted in applying accessory PTH treatment due to its effects on articular chondrocytes.

A Tunable, Three-Dimensional In Vitro Culture Model of Growth Plate Cartilage Using Alginate Hydrogel Scaffolds

Defining the final size and geometry of engineered tissues through precise control of the scalar and vector components of tissue growth is a necessary benchmark for regenerative medicine, but it has proved to be a significant challenge for tissue engineers. The growth plate cartilage that promotes elongation of the long bones is a good model system for studying morphogenetic mechanisms because cartilage is composed of a single cell type, the chondrocyte; chondrocytes are readily maintained in culture; and growth trajectory is predominately in a single vector. In this cartilage, growth is generated via a differentiation program that is spatially and temporally regulated by an interconnected network composed of long- and short-range signaling mechanisms that together result in the formation of functionally distinct cellular zones. To facilitate investigation of the mechanisms underlying anisotropic growth, we developed an in vitro model of the growth plate cartilage by using neonatal mouse growth plate chondrocytes encapsulated in alginate hydrogel beads. In bead cultures, encapsulated chondrocytes showed high viability, cartilage matrix deposition, low levels of chondrocyte hypertrophy, and a progressive increase in cell proliferation over 7 days in culture. Exogenous factors were used to test functionality of the parathyroid-related protein-Indian hedgehog (PTHrP-IHH) signaling interaction, which is a crucial feedback loop for regulation of growth. Consistent with in vivo observations, exogenous PTHrP stimulated cell proliferation and inhibited hypertrophy, whereas IHH signaling stimulated chondrocyte hypertrophy. Importantly, the treatment of alginate bead cultures with IHH or thyroxine resulted in formation of a discrete domain of hypertrophic cells that mimics tissue architecture of native growth plate cartilage. Together, these studies are the first demonstration of a tunable in vitro system to model the signaling network interactions that are required to induce zonal architecture in growth plate chondrocytes, which could also potentially be used to grow cartilage cultures of specific geometries to meet personalized patient needs.

Parathyroid hormone(1-34) exhibits more comprehensive effects than celecoxib in cartilage metabolism and maintaining subchondral bone micro-architecture in meniscectomized guinea pigs

OBJECTIVE

To evaluate the effects of PTH(1-34) on cartilage, subchondral bone mass and structure in medial meniscectomized guinea pigs and compare them to those of celecoxib (CLX).

METHOD

Forty-eight 3-month-old male Hartley albino guinea pigs received either sham or medial meniscectomy (MNX) operations. One week after the procedure, meniscectomized animals began 12 weeks of treatment by oral administration of CLX (20 mg/kg, daily), subcutaneous injection of PTH (1-34) (24 μg/kg, 5 days/week), or normal saline for MNX group. All animals were euthanized 12 weeks later, cartilage degeneration and subchondral bone micro-architecture was analyzed.

RESULTS

OARSI scores indicated cartilage degeneration was partially inhibited by either CLX or PTH(1-34). Cartilage was significantly thicker in PTH(1-34)-treated animals than in CLX-treated animals. Both CLX and PTH(1-34) treatment were associated with lower ADAMTS-4 and periostin expression than MNX. MMP-13 expression in PTH(1-34) group was significantly lower than that in CLX group. However, AGG expression and the ratio of Col-II/MMP-13 expression in PTH(1-34) group were significantly higher than in the CLX group. Micro-CT analysis showed BMD, BV/TV, and Tb.Th levels to be significantly lower in the MNX group and CLX groups than in the sham group, but these parameters were significantly higher in the PTH(1-34) group than in either the MNX group or CLX group.

CONCLUSIONS

Both CLX and PTH(1-34) exhibits protective effects on cartilage degeneration in meniscectomized guinea pigs. However, PTH(1-34) exhibited superior performance to CLX not only in metabolism of cartilage tissue but also in maintenance of subchondral bone micro-architecture.

Suppression of Nkx3.2 by phosphatidylinositol-3-kinase signaling regulates cartilage development by modulating chondrocyte hypertrophy

Phosphatidylinositol-3-kinase (PI3K) is a key regulator of diverse biological processes including cell proliferation, migration, survival, and differentiation. While a role of PI3K in chondrocyte differentiation has been suggested, its precise mechanisms of action are poorly understood. Here we show that PI3K signaling can down-regulate Nkx3.2 at both mRNA and protein levels in various chondrocyte cultures in vitro. In addition, we have intriguingly found that p85β, not p85α, is specifically employed as a regulatory subunit for PI3K-mediated Nkx3.2 suppression. Furthermore, we found that regulation of Nkx3.2 by PI3K requires Rac1-PAK1, but not Akt, signaling downstream of PI3K. Finally, using embryonic limb bud cultures, ex vivo long bone cultures, and p85β knockout mice, we demonstrated that PI3K-mediated suppression of Nkx3.2 in chondrocytes plays a role in the control of cartilage hypertrophy during skeletal development in vertebrates.

Effect of parathyroid hormone on early chondrogenic differentiation from mesenchymal stem cells

Background

Treatment of articular cartilage injuries remains a difficult challenge due to the limited capacity for intrinsic repair. Mesenchymal stem cells (MSCs) can differentiate into chondrocytes under certain culture conditions. This study focused on the modulatory effects of parathyroid hormone (PTH) on chondrogenic differentiation from MSCs.

Methods

MSCs were treated with various concentrations of PTH under chondrogenic pellet culture condition. RNA was isolated for real-time polymerase chain reaction (PCR) and gene expressions of collagen type II α1 chain (Col2a1), collagen type X α1 chain, collagen type I α1 chain, SRY-box9 (Sox9), and type 1 PTH/PTHrP receptor (PTH1R) were examined. Chondrogenic differentiation was also evaluated by histological findings.

Results

PTH had opposite effects on chondrogenesis, depending on the concentration. A low to moderate concentration of PTH promoted chondrogenic differentiation of MSCs with increased expression of Sox9, Col2a1, and PTH1R, whereas chondrogenesis of MSCs was inhibited rather than stimulated with a higher concentration of PTH.

Conclusion

This study provides insights into the modulatory effect of PTH on chondrogenic differentiation from MSCs and the therapeutic potential for cartilage regeneration. Based on clinical experience regarding the efficacy and safety of PTH for bone metabolism, PTH may also be useful clinically for cartilage repair.

Multiple roles of the SO4(2-)/Cl-/OH- exchanger protein Slc26a2 in chondrocyte functions

Mutations in the SO4(2-)/Cl(-)/OH(-) exchanger Slc26a2 cause the disease diastrophic dysplasia (DTD), resulting in aberrant bone development and, therefore, skeletal deformities. DTD is commonly attributed to a lack of chondrocyte SO4(2-) uptake and proteoglycan sulfation. However, the skeletal phenotype of patients with DTD is typified by reduction in cartilage and osteoporosis of the long bones. Chondrocytes of patients with DTD are irregular in size and have a reduced capacity for proliferation and terminal differentiation. This raises the possibility of additional roles for Slc26a2 in chondrocyte function. Here, we examined the roles of Slc26a2 in chondrocyte biology using two distinct systems: mouse progenitor mesenchymal cells differentiated to chondrocytes and freshly isolated mouse articular chondrocytes differentiated into hypertrophic chondrocytes. Slc26a2 expression was manipulated acutely by delivery of Slc26a2 or shSlc26a2 with lentiviral vectors. We demonstrate that slc26a2 is essential for chondrocyte proliferation and differentiation and for proteoglycan synthesis. Slc26a2 also regulates the terminal stage of chondrocyte cell size expansion. These findings reveal multiple roles for Slc26a2 in chondrocyte biology and emphasize the importance of Slc26a2-mediated protein sulfation in cell signaling, which may account for the complex phenotype of DTD.

Biology and pathology of Rho GTPase, PI-3 kinase-Akt, and MAP kinase signaling pathways in chondrocytes

Chondrocytes provide the framework for the developing skeleton and regulate long-bone growth through the activity of the growth plate. Chondrocytes in the articular cartilage, found at the ends of bones in diarthroidial joints, are responsible for maintenance of the tissue through synthesis and degradation of the extracellular matrix. The processes of growth, differentiation, cell death and matrix remodeling are regulated by a network of cell signaling pathways in response to a variety of extracellular stimuli. These stimuli consist of soluble ligands, including growth factors and cytokines, extracellular matrix proteins, and mechanical factors that act in concert to regulate chondrocyte function through a variety of canonical and non-canonical signaling pathways. Key chondrocyte signaling pathways include, but are not limited to, the p38, JNK and ERK MAP kinases, the PI-3 kinase-Akt pathway, the Jak-STAT pathway, Rho GTPases and Wnt-beta-catenin and Smad pathways. Modulation of the activity of any of these pathways has been associated with various pathological states in cartilage. This review focuses on the Rho GTPases, the PI-3 kinase-Akt pathway, and some selected aspects of MAP kinase signaling. Most studies to date have examined these pathways in isolation but it is becoming clear that there is significant cross-talk among the pathways and that the overall effects on chondrocyte function depend on the balance in activity of multiple signaling proteins.