Effect of dynamic compressive loading and its combination with a growth factor on the chondrocytic phenotype of 3-dimensional scaffold-embedded chondrocytes

Background and purpose Three-dimensionally (3D-) embedded chondrocytes have been suggested to maintain the chondrocytic phenotype. Furthermore, mechanical stress and growth factors have been found to be capable of enhancing cell proliferation and ECM synthesis. We investigated the effect of mechanical loading and growth factors on reactivation of the 3D-embedded chondrocytes.

Methods Freshly isolated chondrocytes from rat articular cartilage were grown in monolayer cultures and then in collagen gel. Real-time RT-PCR and histological analysis for aggrecan and type II and type I collagen was performed to evaluate their chondrocytic activity. Then, the 3D-embedded chondrocytes were cultured under either mechanical loading alone or in combination with growth factor. The dynamic compression (5% compression, 0.33 Hz) was loaded for 4 durations: 0, 10, 60, and 120 min/day. The growth factor administered was either basic fibroblast growth factor (bFGF) or bone morphogenetic protein-2 (BMP-2).

Results Mechanical loading statistically significantly reactivated the aggrecan and type II collagen expression with loading of 60 min/day as compared to the other durations. The presence of BMP-2 and bFGF clearly enhanced the aggrecan and type II collagen expression of 3D-embedded chondrocytes. Unlike previous reports using monolayer chondrocytes, however, BMP-2 or bFGF did not augment the chondrocytic phenotype when applied together with mechanical loading.

Interpretation Dynamic compression effectively reactivated the dedifferentiated chondrocytes in 3D culture. However, the growth factors did not play any synergistic role when applied with dynamic compressive loading, suggesting that growth factors should be administered at different time points during regeneration of the transplantation-ready cartilage.     

氧环境影响关节软骨细胞表型的相关研究

[目的]观察检测低氧和常氧条件下原代和传代后软骨细胞各特异性基因及蛋白表达的改变.[方法]采用3～5日龄C57BL/6小鼠,取四肢关节软骨,经机械分离和酶消化法获得关节软骨细胞,将原代细胞P0和传代后细胞P_1、P_2分别在普通和低氧培养箱中培养2 d,用RT-PCR检测II型胶原、可聚蛋白聚糖和sox9特异性基因及Ihh、PTHrP、bmp4、wnt5a分化相关基因的表达差异,原代软骨细胞用免疫组化和阿利新蓝染色检测II型胶原、可聚蛋白聚糖的蛋白表达.[结果]低氧条件下,免疫组化显示II型胶原和可聚蛋白聚糖的表达较普通培养增强,II型胶原、wnt5a的基因表达增强,Ihh的表达降低;传代后软骨细胞的蛋白、特异性基因和分化相关基因表达未见明显差异.[结论]低氧条件下,原代软骨细胞的II型胶原表达增强,且可能主要是受Ihh、wnt5a等分化相关基因的调控.短期单层培养方式不能明显改善、恢复特异性基因表达降低的传代后软骨细胞表型.     

Effect of transfection strategy on growth factor overexpression by articular chondrocytes

Articular cartilage damage remains an unsolved problem in orthopaedics. Insulin‐like growth factor I (IGF‐I) and fibroblast growth factor‐2 (FGF‐2) are anabolic and mitogenic for articular chondrocytes, and are candidates for the application of gene therapy to articular cartilage repair. We tested the hypothesis that the production of IGF‐I and FGF‐2 can be augmented by modulating vector designs and delivery methods used for gene transfer to articular chondrocytes. We developed a novel adeno‐associated virus (AAV)‐based plasmid (pAAV) to overexpress IGF‐I and FGF‐2 cDNAs in adult bovine articular chondrocytes. We found that the pAAV‐based vectors generated significantly more growth factor than pcDNA vectors carrying the same cDNAs. Chondrocytes cotransfected with both IGF‐I and FGF‐2 cDNAs in two separate pAAV plasmids produced significantly more IGF‐I and FGF‐2 than cells transfected by a single pAAV plasmid carrying both cDNAs in a dicistronic cassette. These data indicate that pAAV vectors are more effective than pcDNA vectors for transfer of IGF‐I and FGF‐2 genes to articular chondrocytes. They further suggest that cotransfection may be an effective strategy for multiple gene transfer to these cells. These findings may be important in applying growth factor gene transfer to cell‐based articular cartilage gene therapy. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:103–109, 2010     

Leptin acts as a growth factor on the chondrocytes of skeletal growth centers.

Childhood obesity frequently is associated with an increase in height velocity and acceleration of epiphyseal growth plate maturation despite low levels of serum growth hormone (GH). In addition, obesity is associated with higher circulating levels of leptin, a 16-kDa protein that is secreted from the adipocytes. In this study, we evaluated the direct effect of leptin on the chondrocyte population of the skeletal growth centers in the mouse mandibular condyle, a model of endochondral ossification. We found that chondrocytes in the growth centers contain specific binding sites for leptin. Leptin, at a concentration of 0.5-1.0 microg/ml, stimulated in a dose-dependent manner the width of the chondroprogenitor zone (up to 64%), whereas higher concentrations had an inhibitory effect. Leptin induction of both proliferation and differentiation activities in the mandibular condyle was confirmed by our findings of an increase in bromodeoxyuridine (BrdU) incorporation into DNA and in (acidic) Alcian blue (AB) staining of the cartilaginous matrix. Leptin also increased the abundance of the insulin-like growth factor (IGF) I receptor and IGF-I receptor messenger RNA (mRNA) within the chondrocytes and the progenitor cell population. Our results indicate that leptin acts as a skeletal growth factor with a direct peripheral effect on skeletal growth centers. Some of its effects on the growing bone may be mediated by the IGF system via regulation of IGF-I receptor expression. We speculate that the high circulating levels of leptin in obese children might contribute to their growth.     

Autologous chondrocyte implantation. Culture in a TGF-beta-containing medium enhances the re-expression of a chondrocytic phenotype in passaged human chondrocytes in pellet culture

An increasing number of patients are treated by autologous chondrocyte implantation (ACI). This study tests the hypothesis that culture within a defined chondrogenic medium containing TGF-beta enhances the re-expression of a chondrocytic phenotype and the subsequent production of cartilaginous extracellular matrix by human chondrocytes used in ACI. Chondrocytes surplus to clinical requirements for ACI from 24 patients were pelleted and cultured in either DMEM (Dulbecco's modified eagles medium)/ITS+Premix/TGF-beta1 or DMEM/10%FCS (fetal calf serum) and were subsequently analysed biochemically and morphologically. Pellets cultured in DMEM/ITS+/TGF-beta1 stained positively for type-II collagen, while those maintained in DMEM/10%FCS expressed type-I collagen. The pellets cultured in DMEM/ITS+/TGF-beta1 were larger and contained significantly greater amounts of DNA and glycosaminoglycans. This study suggests that the use of a defined medium containing TGF-beta is necessary to induce the re-expression of a differentiated chondrocytic phenotype and the subsequent stimulation of glycosaminoglycan and type-II collagen production by human monolayer expanded chondrocytes.     

血管内皮生长因子对关节软骨细胞基质金属蛋白酶-13表达的影响

目的 观察血管内皮生长因子(VEGF)对体外培养的关节软骨细胞基质金属蛋白酶-13(MMP-13)表达的影响.方法 体外培养SD乳鼠关节软骨细胞,分为4组,每组加入不同处理因素进行干预,A组:(对照组)不加任何处理因素;B组:10 μg/L VEGF;C组:10 μg/L白细胞介素(IL)-1β;D组:10 μg/L VEGF+ 10 μg/L IL-1β.采用实时荧光定量聚合酶链反应(PCR)检测MMP-13 mRNA的表达,蛋白免疫印迹法检测MMP-13蛋白的表达.结果 B组(0.88±0.47)、C组(3.69 ±0.45)及D组(3.85 ±0.48)的MMP-13 mRNA表达水平均显著高于A组(0.73±0.56),D组软骨细胞MMP-13的mRNA表达水平明显高于B组(P＜0.01)及C组(P＜0.05).与A组(0.36 ±0.17)比较,B组(0.63±0.21)、C组(0.76±0.24)及D组(0.99±0.26)的MMP-13蛋白表达水平显著升高,D组MMP-13的蛋白表达水平明显高于B组(P＜0.05)及C组(P＜0.05).结论 在骨关节炎的发病过程中VEGF可能通过上调软骨细胞MMP-13的表达发挥重要作用.     

Synergistic effect of transforming growth factor beta and fibroblast growth factor on DNA synthesis in chick growth plate chondrocytes

Transforming growth factor beta and fibroblast growth factor are mitogens for chick growth plate chondrocytes. TGF-beta stimulated a 3.5-fold increase, and FGF a 13.5-fold increase in the rate of thymidine incorporation after a 24 h exposure. TGF-beta and FGF were synergistic in chondrocytes, causing a 73-fold stimulation in thymidine incorporation compared with control. This synergistic response was not dependent upon the simultaneous presence of both mitogens. Sequential exposure of chondrocytes to TGF-beta and FGF in either order reproduced in large part the synergistic interaction observed when both growth factors were present simultaneously. The time required for induction of the subsequent synergistic response was brief and, in the case of TGF-beta, corresponded to the time required for [125I]TGF-beta receptor binding. EGF and PDGF were not mitogenic for chondrocytes, and neither of these factors enhanced the response of the cells to either TGF-beta or FGF. Finally, TGF-beta and FGF did not, either alone or in combination, elevate intracellular cAMP levels. These results emphasize the importance of examining growth factor effects in the context of other growth regulators. Furthermore, this specific and dramatic synergistic stimulation of thymidine incorporation may provide a useful tool in elucidating the mitogenic mechanism of the individual growth factors.     

In vitro response of human chondrocytes to a combination of growth factors and a proteinase inhibitor

Degenerative disk disease is an accelerating cascade of tissue degeneration in the intervertebral disk. A harsh catabolic environment perpetuates the degeneration of the intervertebral disk. Tissue engineering-based techniques offer effective treatment to slow the progression of degenerative disk disease and regenerate intervertebral disk tissue. The purpose of this study was to assess the efficacy of a regenerative therapy for degenerative disk disease by treating human chondrocytes with anabolic growth factors and a proteinase inhibitor. The use of both proved effective in upregulating important extracellular matrix markers of human chondrocytes. These successful in vitro results have implications for the regeneration of the intervertebral disk.     

The beneficial effect of delayed compressive loading on tissue-engineered cartilage constructs cultured with TGF-beta3

OBJECTIVE: To determine whether the functional properties of tissue-engineered constructs cultured in a chemically-defined medium supplemented briefly with TGF-beta3 can be enhanced with the application of dynamic deformational loading. METHODS: Primary immature bovine cells (2-3 months old) were encapsulated in agarose hydrogel (2%, 30 x 10(6)cells/ml) and cultured in chemically-defined medium supplemented for the first 2 weeks with transforming growth factor beta 3 (TGF-beta3) (10 microg/ml). Physiologic deformational loading (1 Hz, 3 h/day, 10% unconfined deformation initially and tapering to 2% peak-to-peak deformation by day 42) was applied either concurrent with or after the period of TGF-beta3 supplementation. Mechanical and biochemical properties were evaluated up to day 56. RESULTS: Dynamic deformational loading applied concurrently with TGF-beta3 supplementation yielded significantly lower (-90%) overall mechanical properties when compared to free-swelling controls. In contrast, the same loading protocol applied after the discontinuation of the growth factor resulted in significantly increased (+10%) overall mechanical properties relative to free-swelling controls. Equilibrium modulus values reach 1306+/-79 kPa and glycosaminoglycan levels reach 8.7+/-1.6% w.w. during this 8-week period and are similar to host cartilage properties (994+/-280 kPa, 6.3+/-0.9% w.w.). CONCLUSIONS: An optimal strategy for the functional tissue engineering of articular cartilage, particularly to accelerate construct development, may incorporate sequential application of different growth factors and applied deformational loading.     

The effects of transforming growth factor β1, insulin-like growth factor 1 and leptin on the proliferation of fetal chondrocytes

One method to exogenously enhance the repair of articular cartilage is the local application of growth factors. This method is based on the chondrogenic effects of some agents and their potential ability to enhance cell migration. Human fetal chondrocytes were isolated and cultured. Their proliferation under the influence of different agents was microscopically evaluated. Fetal calf serum at 5% and 10% concentrations induced microscopically visible cell proliferation. Transforming growth factor beta one (5 and 10 ng/ml), insulin-like growth factor 1 (5 and 10 nmol/l) and leptin (1 and 2 ng/ml) accelerated proliferation of the cells towards the increasing gradient of the agents. Fibroblast growth factor beta (5 and 10 ng/ml), bone morphogenic protein two (10 ng/ml) and laminin (1 mg/ml) did not affect cell proliferation. This study suggests that different agents can play a role in the proliferation of fetal chondrocytes.     

The effects of dynamic axial loading on the rat growth plate.

Longitudinal bone growth can be suppressed by compressive loading. In this study, we applied three different magnitudes (17, 8.5, and 4N) of compressive force to growing rat ulnas 10 minutes/day for 8 days and investigated the effects on the distal growth plate biology. Further, to investigate growth rate recovery after cessation of loading, we examined rats 7 days after the loading period. Longitudinal growth of the ulna was suppressed in a dose-dependent manner by applied compressive force. In the 17N group, the longitudinal mineralization rate (LMR) at the distal growth plate was suppressed completely by loading and did not recover. However, in the 8.5N and 4N groups, LMR suppression recovered in 1 week. In the 17N group, growth plate height and hypertrophic zone height were significantly greater than control; the number of hypertrophic chondrocytes was increased; and some traumatic changes such as cracks in the growth plate were found. In addition, 17N loading suppressed cartilage mineralization and capillary invasion beneath the growth plate, although the number of chondrocytes synthesizing vascular endothelial growth factor (VEGF) was increased. Our study shows longitudinal growth suppression caused by axial loading of the ulna, which is proportional to the magnitude of load. Only the largest load (17N) caused morphological changes in the distal growth plate cartilage. There was no association found between mineralization and type X collagen localization or capillary invasion and VEGF expression.     

PcDNA3-hBMP3基因转染关节软骨细胞及其稳定表达

目的 探讨外源性基因ｈＢＭＰ３在软骨细胞获得稳定表达的可能性。方法 将和ＢＭＰ３的ｃＤＮＡ构建于真核表达载体ＰｃＤＮＡ３,形成重组真核表达载体ＰｃＤＮＡ３－ｈＢＭＰ３,转染培养状态下兔关节软骨细胞。利用重组ＤＮＡ和基因克隆技术构建重组真核表达载体ＰｃＤＮＡ３－ｈＢＭＰ３;利用细胞２和细胞基因转染技术体外转染ｈＢＭＰ３基因至关节软骨细胞;     

Differential expression of phenotype by resting zone and growth region costochondral chondrocytes in vitro

This study establishes an in vitro model for examining endochondral cartilage cell metabolism. Chondrocytes derived from the resting cell zone and adjacent growth zone of rat costochondral cartilage were compared for retention of phenotype in culture. At third passage confluence, two cell populations differ morphologically and biochemically. Resting zone cells are fibroblast-like, with smooth cell membranes and little rough endoplasmic reticulum. Growth zone cells are more polygonal, smaller in diameter, with numerous cytoplasmic extensions of the plasma membranes and abundant rough endoplasmic reticulum. Both cell populations produce matrix vesicles that are comparable morphologically to matrix vesicles isolated enzymatically from epiphyseal cartilage. While membrane vesicles are released into the media by cells derived from the resting zone as well as from the growth cartilage, alkaline phosphatase activity is enriched in media vesicles produced by growth cartilage cells. Alkaline phosphatase enriched vesicles appear to be preferentially incorporated into the extracellular matrix. Both the plasma membrane marker enzyme activity and the membrane phospholipid composition are differentially expressed in matrix vesicles and plasma membranes and are cell specific. Matrix vesicles produced by resting zone cells are enriched in alkaline phosphatase, 5'-nucleotidase, ouabain sensitive Na+/K+ ATPase and cardiolipin when compared to the cell membrane. In addition, the plasma membranes of these cells contain more phosphatidylcholine plus sphingomyelin than do growth cartilage plasma membranes. Resting zone cell matrix vesicles have less phosphatidylethanolamine than do vesicles from growth cartilage cultures. Matrix vesicles produced by growth cartilage cells contain one proteolipid at 43,000 Mr which comigrates with plasma membrane proteolipid and an additional proteolipid at approximately 3,000 Mr. These data indicate that both cells retain differential expression of phenotype in culture and that one expression of this phenotype is production of specific extracellular matrix vesicles.     

Expression of the cadherin-11 gene is a discriminative factor between articular and growth plate chondrocytes

OBJECTIVE: Calcification of hypertrophic chondrocytes is the final step in the differentiation of growth plates, although the precise mechanism is not known. We have established two growth plate-derived chondrocyte cell lines, MMR14 and MMR17, from p53-/- mice (Nakamata T, Aoyama T, Okamoto T, Hosaka T, Nishijo K, Nakayama T, et al. In vitro demonstration of cell-to-cell interaction in growth plate cartilage using chondrocytes established from p53-/- mice. J Bone Miner Res 2003;18:97-107). Prolonged in vitro culture produced calcified nodules in MMR14, but not in MMR17. Factors responsible for the difference in calcification between the two cell lines may also be involved in the physiological calcification in growth plate. DESIGN: Gene expression profiles of MMR14 and MMR17 were compared using a cDNA microarray to identify candidate genes involved in the calcification process. RESULTS: Forty-five genes were identified as upregulated in MMR14, including the cadherin-11 (Cdh-11) gene. The expression of Cdh-11 in MMR14 was detected in cell-cell junctions, while no expression was observed in MMR17. Primary cultured chondrocytes from growth plate (GC) also expressed the Cdh-11, and the staining of Cdh-11 was observed in the late hypertrophic zone of growth plate. Cell aggregation assays showed that chondrocytes required Ca2+ to form nodules, and knockdown of the Cdh-11 gene expression using short interfering RNA inhibited the formation of calcified nodules in MMR14. The introduction of Cdh-11 into MMR17 failed to produce calcified nodules indicating that Cdh-11 is one, but not the sole, factor responsible for the production of calcified nodules. CONCLUSION: Although the physiological role is still unclear, Cdh-11 is a discriminative factor between articular and growth plate chondrocytes.     

Mechanical behavior of the human lumbar spine. II. Fatigue strength during dynamic compressive loading

Seventeen cadaveric human lumbar motion segments from eight spines were cyclically loaded in vitro under axial compression. Loading frequency and magnitude were chosen to simulate rigorous activity within an in vivo physiological level. The load magnitude was determined as a percentage of the ultimate compressive load, the latter estimated from the bone mineral content (BMC) of lumbar vertebrae determined by dual-photon absorptiometry. Following testing, the degree of macroscopic disc degeneration was assessed and the type of fracture in each specimen was determined from serial sagittal sections. Fractures were found in all but one specimen. Three types of fractures were formed: the node of Schmorl and Junghanns (type I), central endplate fracture (type II), and a crush or burst fracture (type III). The results suggested that type I fractures were predominantly associated with segments with normal discs, type II fractures were found primarily in segments with moderately degenerated discs, and type III fractures were associated with segments that failed on the first cycle. Segment stiffness and fatigue strength (cycles to failure) were correlated with disc degeneration, age, and segment BMC, the latter an in vivo measure of bone density. Fatigue strength also decreased in proportion to a power coefficient with increasing relative stress (cyclic stress range/ultimate stress).     

Fibroblast growth factor-18 is a trophic factor for mature chondrocytes and their progenitors

OBJECTIVE: The aim of this study was to examine the effects of recombinant human Fgf18 on chondrocyte proliferation and matrix production in vivo and in vitro. In addition, the expressions of Fgf18 and Fgf receptors (Fgfr) in adult human articular cartilage were examined. METHODS: Adenovirus-mediated transfer of Fgf18 into murine pinnae and addition of FGF18 to primary cultures of adult articular chondrocytes were used to assess the effects of FGF18 on chondrocytes. In situ hybridization was used to examine the expression of Fgf18 and Fgfr s in adult human articular cartilage. RESULTS: Expression of Fgf18 by adenovirus-mediated gene transfer in murine pinnae resulted in a significant increase in chondrocyte number. Chondrocytes were identified by staining with toluidine blue and a monoclonal antibody directed against type II collagen. Fgf18, Fgfr 2-(IIIc), Fgfr 3-(IIIc), and Fgfr 4 mRNAs were detected within these cells by in situ hybridization. The nuclei of the chondrocytes stained with antibodies to PCNA and FGF receptor (FGFR) 2. Addition of FGF18 to the culture media of primary articular chondrocytes increased the proliferation of these cells and increased their production of extracellular matrix. To assess the receptor selectivity of FGF18, BaF3 cells stably expressing the genes for the major splice variants of Fgfr1-3 were used. Proliferation of cells expressing Fgfr 3-(IIIc) or Fgfr 2-(IIIc) was increased by incubation with FGF18. Using FGFR-Fc fusion proteins and BaF3 cells expressing Fgfr 3-(IIIc), only FGFR 3-(IIIc)-Fc, FGFR 2-(IIIc)-Fc or FGFR 4-Fc reduced FGF18-mediated cell proliferation. Expression of Fgf18, Fgfr 3-(IIIc) and Fgfr 2-(IIIc) mRNAs was localized to chondrocytes of human articular cartilage by in situ hybridization. CONCLUSION: These data demonstrate that Fgf18 can act as a trophic factor for elastic chondrocytes and their progenitors in vivo and articular chondrocytes cultured in vitro. Expression of Fgf18 and the genes for two of its receptors in chondrocytes suggests that Fgf18 may play an autocrine role in the biology of normal articular cartilage.     

Insulin-like growth factor I in combination with insulin-like growth factor binding protein 3 affects the hepatic acute phase response and hepatic morphology in thermally injured rats

OBJECTIVE: To modulate the hepatic acute phase response after a thermal injury by the administration of insulin-like growth factor I (IGF-I) in combination with its principal binding protein 3 (IGFBP-3). SUMMARY BACKGROUND DATA: The hepatic acute phase response is a cascade of events initiated to restore homeostasis after trauma; however, a prolonged response contributes to multiorgan failure, hypermetabolism, complications, and death. Although IGF-1 has been shown to improve cell recovery and play a major role in liver regeneration, its effect on the hepatic acute phase response is not known. METHODS: Sprague-Dawley rats (56 males) received a 60% total body surface area third-degree scald burn and were randomly divided to receive either rhIGF-I/BP-3 (10 mg/kg/day given subcutaneously) or saline (control). Rats were killed on postburn days 1, 2, 5, and 7 and serum glucose, electrolytes, acute phase reactant proteins, tumor necrosis factor alpha, interleukin 1 beta, interleukin 6, and rat and human serum IGF-I and IGFBP-3 were measured. Hepatic protein concentrations, hepatocyte proliferation, and hepatocyte apoptosis were determined. RESULTS: No hypoglycemia or electrolyte imbalance could be shown in rats receiving the growth factor complex compared with saline. rhIGF-I/BP-3 increased serum protein on postburn days 2 and 7, albumin on days 5 and 7, and transferrin on days 1, 5, and 7, and decreased haptoglobin and alpha1-acid glycoprotein on postburn days 5 and 7 compared with controls. IGF-I/ BP-3 had no effect on type II acute phase proteins. Rats receiving IGF-I/BP-3 had lower serum levels of interleukin 1 beta and tumor necrosis factor alpha on the first day after burn compared with controls, whereas serum levels of interleukin 6 did not change. rhIGF-I/BP-3 significantly increased total liver protein content on postburn days 1, 2, 5, and 7 compared with controls. IGF-I/BP-3 increased hepatocyte proliferation and decreased hepatocyte apoptosis versus controls. CONCLUSION: In combination with its principal binding protein, rhIGF-I decreases the proinflammatory cytokines interleukin 1 beta and tumor necrosis factor alpha, followed by a decrease in type I acute phase proteins. IGF-I/BP-3 had no effect on interleukin 6 and type II acute phase proteins. Decreases in acute phase protein and proinflammatory cytokine synthesis were associated with increases in constitutive hepatic proteins, total liver protein content, and hepatocyte proliferation. IGF-I/BP-3 attenuates the hypermetabolic response after thermal injury and may improve the clinical outcome.