Effect of Growth Hormone and Insulin-Like Growth Factor I (IGF-I) on the Expression of IGF-I Messenger Ribonucleic Acid and Peptide in Rat Tibial Growth Plate and Articular Chondrocytes in Vivo 1 (original) (raw)
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Calcified Tissue International, 1987
We have studied the effect of local arterial infusion of bacterially produced human growth hormone (hGH), insulinlike growth factor I (IGF-I), or pituitary-derived ovine prolactin (oPRL) on longitudinal bone growth of hypophysectomized rats. The substances were infused during a 14-day period by osmotic mini-pumps through a catheter which was implanted into the femoral artery of one hindlimb. Longitudinal bone growth was measured by the intravital marker tetracycline. Infusion of 1 fxg hGH per day stimulated bone growth only of the treated limb and not of the uninfused contralateral limb. Infusion of 10 Ixg hGH per day also stimulated unilateral longitudinal bone growth, but the uninfused contralateral limb also showed a significant growth response, probably because local administration of GH at this dose caused a significant elevation of GH in the systemic circulation. As a result, the differential growth response between the GH-treated and untreated limbs decreased compared to rats that were infused with 1 ixg hGH per day. Unilateral arterial infusion of 5 fxg human IGF-I or 10 txg oPRL per day did not produce a significant growth response. The results of the present study confirm the observation by Schlechter and co-workers , who demonstrated that unilateral arterial infusion of GH maintained tibial cartilage width following hypophysectomy in the rat. The results of Schlechter and coworkers and the results of the present study show that GH in vivo stimulates epiphyseal cartilage growth directly. However, an increased local production of insulinlike growth factors is probably of importance for the expression of the direct effect of GH on longitudinal bone growth. The present results do not completely rule out the possibility that Send reprint requests to Dr. Olle lsaksson, Department of Physiology, University of G6teborg, RO. Box 33031, S-400 33 G6teborg, Sweden. insulinlike growth factors in the circulation might have the growth plate as a target organ.
Spatial and temporal regulation of GH–IGF-related gene expression in growth plate cartilage
Journal of Endocrinology, 2007
Previous studies of the GH–IGF system gene expression in growth plate using immunohistochemistry and in situ hybridization have yielded conflicting results. We therefore studied the spatial and temporal patterns of mRNA expression of the GH–IGF system in the rat proximal tibial growth plate quantitatively. Growth plates were microdissected into individual zones. RNA was extracted, reverse transcribed and analyzed by real-time PCR. In 1-week-old animals, IGF-I mRNA expression was minimal in growth plate compared with perichondrium, metaphyseal bone, muscle, and liver (70-, 130-, 215-, and 400-fold less). In contrast, IGF-II mRNA was expressed at higher levels than in bone and liver (65- and 2-fold). IGF-II expression was higher in the proliferative and resting zones compared with the hypertrophic zone (P < 0.001). GH receptor and type 1 and 2 IGF receptors were expressed throughout the growth plate. Expression of IGF-binding proteins (IGFBPs)-1 through -6 mRNA was low throughout t...
Growth Hormone & IGF Research, 2012
Introduction: Catch-up growth following the cessation of a growth inhibiting cause occurs in humans and animals. Although its underlying regulatory mechanisms are not well understood, current hypothesis confer an increasing importance to local factors intrinsic to the long bones' growth plate (GP). Aim: The present study was designed to analyze the growth-hormone (GH)-insulin-like growth factor I (IGF-I) axis in the epiphyseal cartilage of young rats exhibiting catch-up growth as well as to evaluate the effect of GH treatment on this process. Material and methods: Female Sprague-Dawley rats were randomly grouped: controls (group C), 50% diet restriction for 3 days + refeeding (group CR); 50% diet restriction for 3 days + refeeding & GH treatment (group CRGH). Analysis of GH receptor (GHR), IGF-I, IGF-I receptor (IGF-IR) and IGF binding protein 5 (IGFBP5) expressions by real-time PCR was performed in tibial growth plates extracted at the time of catch-up growth, identified by osseous front advance greater than that of C animals. Results: In the absence of GH treatment, catch-up growth was associated with increased IGF-I and IGFBP5 mRNA levels, without changes in GHR or IGF-IR. GH treatment maintained the overexpression of IGF-I mRNA and induced an important increase in IGF-IR expression. Conclusions: Catch-up growth that happens after diet restriction might be related with a dual stimulating local effect of IGF-I in growth plate resulting from overexpression and increased bioavailability of IGF-I. GH treatment further enhanced expression of IGF-IR which likely resulted in a potentiation of local IGF-I actions. These findings point out to an important role of growth cartilage GH/IGF-I axis regulation in a rat model of catch-up growth.
Effects of GH/IGF axis on bone and cartilage
Molecular and Cellular Endocrinology, 2021
Growth hormone (GH) and its mediator, the insulin-like growth factor-1 (IGF-1) regulate somatic growth, metabolism and many aspects of aging. As such, actions of GH/IGF have been studied in many tissues and organs over decades. GH and IGF-1 are part of the hypothalamic/pituitary somatotrophic axis that consists of many other regulatory hormones, receptors, binding proteins, and proteases. In humans, GH/IGF actions peak during pubertal growth and regulate skeletal acquisition through stimulation of extracellular matrix production and increases in bone mineral density. During aging the activity of these hormones declines, a state called somatopause, which associates with deleterious effects on the musculoskeletal system. In this review, we will focus on GH/IGF-1 action in bone and cartilage. We will cover many studies that have utilized congenital ablation or overexpression of members of this axis, as well as cell-specific gene-targeting approaches used to unravel the nature of the GH/IGF-1 actions in the skeleton in vivo.
Longitudinal bone growth in vitro: effects of insulin-like growth factor I and growth hormone
European Journal of Endocrinology, 1991
Longitudinal growth was studied using an in vitro model system of intact rat long bones. Metatarsal bones from 18-and 19-day-old rat fetuses, entirely (18 days) or mainly (19 days) composed of chondrocytes, showed a steady rate of growth and radiolabelled thymidine incorporation for at least 7 days in serum-free media. Addition of recombinant human insulin-like growth factor-I to the culture media resulted in a direct stimulation of the longitudinal growth. Recombinant human growth hormone was also able to stimulate bone growth, although this was generally accomplished after a time lag of more than 2 days. A monoclonal antibody to IGF-I abolished both the IGF-I and GH-stimulated growth. However, the antibody had no effect on the growth of the bone explants in control, serum-free medium. Unlike the fetal long bones, bones from 2-day\ x=req-\ old neonatal rats were arrested in their growth after 1-2 days in vitro. The neonatal bones responded to IGF-I and GH in a similar fashion as the fetal bones. Thus in this study in vitro evidence of a direct effect of GH on long bone growth via stimulating local production of IGF by the growth plate chondrocytes is presented. Furthermore, endogenous growth factors, others than IGFs, appear to play a crucial role in the regulation of fetal long bone growth.
Experimental Cell Research, 1997
Subsequent transfer to an in vitro suspension culture Reexpression of aggrecan and type II collagen genes system, such as agarose or alginate, leads to redifferenin dedifferentiated adult human articular chondro-tiation characterized in part by the synthesis of carticytes (AHAC) in suspension culture varied widely delage specific proteoglycan and type II collagen [1] and pending on the specific lot of bovine serum used to the reappearance of their respective mRNAs in human supplement the culture medium. Some lots of serum articular chondrocytes of fetal [2] and adult [3] origin. provided strong induction of aggrecan and type II col-Evidence for redifferentiation of articular chondrocytes lagen expression by AHAC while others did not stimuin vivo is provided by the generation of hyaline-like late significant production of these hyaline cartilage cartilage and its markers within articular cartilage deextracellular matrix molecules even following several fects following implantation of dedifferentiated chonweeks in culture. Addition of 50 ng/ml insulin-like drocytes [4, 5]. growth factor-I (IGF-I) to a deficient serum lot signifi-In the above examples, the serum present in the in cantly enhanced its ability to induce aggrecan and vitro culture system and the synovial fluid proximal to type II collagen mRNA. Given this observation, IGF-I the in vivo implant are composed of complex undefined and other growth factors were tested in defined semixtures of bioactive factors [6], the individual comporum-free media for their effects on the expression of nents of which may or may not be involved in normal these genes. Neither IGF-I nor insulin nor transchondrogenesis. Although several growth factors have forming growth factor b (TGF-b) alone stimulated inbeen identified that modulate expression of cartilage duction of aggrecan or type II collagen production by matrix proteins by chondrocytes, the minimal growth dedifferentiated AHAC. However, TGF-b1 or TGF-b2 factor requirement for induction of dedifferentiated arcombined with IGF-I or insulin provided a strong inticular chondrocytes to their original phenotype has duction as demonstrated by RNase protection and imnot been established. Further investigation on specific munohistochemical assays. Interestingly, type I collacombinations of chondrogenic factors using defined megen, previously shown to be downregulated in serum supplemented suspension cultures of articular chon-dium in a suspension culture system is necessary to drocytes, persisted for up to 12 weeks in AHAC cul-establish this requirement. tured in defined medium supplemented with TGF-b Transforming growth factor-b (TGF-b) and insulinand IGF-I.
Kidney International, 1998
Interaction of IGF-I and 1␣,25(OH) 2 D 3 on receptor expression and growth stimulation in rat growth plate chondrocytes. Growth plate cartilage cells express receptors for, and are affected by both IGF-I and 1␣,25(OH) 2 D 3. The studies were undertaken to investigate interaction between these two hormone systems, that is, (i) to study effects of 1␣,25(OH) 2 D 3 on IGF-type 1 receptors (IGFIR), on IGF-I stimulated cell replication, colony formation, and on alkaline phosphatase activity (AP), and conversely, (ii) to study the effect of IGF-I on vitamin D receptor (VDR) expression on 1␣,25(OH) 2 D 3 stimulated growth parameters and on AP activity. Freshly isolated rat tibial chondrocytes were grown in monolayer cultures, (serum-free) or in agarose stabilized suspension cultures (0.1% FCS). Vitamin D receptor and IGFIR were visualized by immunostaining with the monoclonal antibody (mAb) 9A7␥ and mAb ␣IR3, respectively, and quantitated by RT-PCR for mRNA and by Scatchard analysis using [ 3 H]-1,25(OH) 2 D 3 and [ 125 I]-␣IR3. Cell proliferation was measured by [ 3 H]-thymidine incorporation, growth curves in monolayer cultures, and by colony formation in agarose-stabilized suspension cultures. IGF-I dose-dependently increased [ 3 H]-thymidine incorporation. 1␣,25(OH) 2 D 3 , but not 1,25(OH) 2 D 3 was stimulatory at low (10 Ϫ12 M) and slightly inhibitory at high (10 Ϫ8 M) concentrations. The effect of IGF-I was additive to that of 1␣,25(OH) 2 D 3 [IGF-I 60 ng/ml, 181 Ϯ 12.7; 1␣,25(OH) 2 D 3 10 Ϫ12 M, 181 Ϯ 9.8%, IGF-I ϩ 1␣,25(OH) 2 D 3 , 247 Ϯ 16.7%; P Ͻ 0.05 by ANOVA] and specifically obliterated by polyclonal IGF-I antibody (AB-1). Interaction could also be confirmed in suspension cultures. IGFIR mRNA and [ 125 I]-␣IR3 binding was increased by low (10 Ϫ12 M) but not by high (10 Ϫ8 M) concentrations of 1␣,25(OH) 2 D 3. Homologous up-upregulation by IGF-I (60 ng/ml) was specifically inhibited by AB-1 and markedly amplified by coincubation with 1␣,25(OH) 2 D 3 (10 Ϫ12 M). Immunostaining with ␣IR3 showed specific IGFIR expression in rat growth cartilage, but not liver tissue. Stimulation of chondrocytes with 1␣,25(OH) 2 D 3 or IGF-I suggested some increase of receptor expression in single cells, but the predominant effect was increased recruitment of receptor positive cells. Vitamin D receptor expression was markedly stimulated (fourfold) by IGF-I (60 ng/ml), but not IGF-II and inhibited by actinomycin D. This study shows that IGF-I and 1␣,25(OH) 2 D 3 mutually up-regulate their respective receptors in growth plate chondrocytes. In parallel, they have additive effects on cell proliferation and colony formation suggesting independent effector pathways. METHODS Materials 1␣,25(OH) 2-[26,27-methyl-3 H]cholecalciferol (158 Ci/mmol) was obtained from Amersham Buchler (Braunschweig, Germany); unlabeled 1␣,25(OH) 2 D 3 and 1,25(OH) 2 D 3 , were gifts from
Kidney International, 1998
Interaction of IGF-I and 1␣,25(OH) 2 D 3 on receptor expression and growth stimulation in rat growth plate chondrocytes. Growth plate cartilage cells express receptors for, and are affected by both IGF-I and 1␣,25(OH) 2 D 3. The studies were undertaken to investigate interaction between these two hormone systems, that is, (i) to study effects of 1␣,25(OH) 2 D 3 on IGF-type 1 receptors (IGFIR), on IGF-I stimulated cell replication, colony formation, and on alkaline phosphatase activity (AP), and conversely, (ii) to study the effect of IGF-I on vitamin D receptor (VDR) expression on 1␣,25(OH) 2 D 3 stimulated growth parameters and on AP activity. Freshly isolated rat tibial chondrocytes were grown in monolayer cultures, (serum-free) or in agarose stabilized suspension cultures (0.1% FCS). Vitamin D receptor and IGFIR were visualized by immunostaining with the monoclonal antibody (mAb) 9A7␥ and mAb ␣IR3, respectively, and quantitated by RT-PCR for mRNA and by Scatchard analysis using [ 3 H]-1,25(OH) 2 D 3 and [ 125 I]-␣IR3. Cell proliferation was measured by [ 3 H]-thymidine incorporation, growth curves in monolayer cultures, and by colony formation in agarose-stabilized suspension cultures. IGF-I dose-dependently increased [ 3 H]-thymidine incorporation. 1␣,25(OH) 2 D 3 , but not 1,25(OH) 2 D 3 was stimulatory at low (10 Ϫ12 M) and slightly inhibitory at high (10 Ϫ8 M) concentrations. The effect of IGF-I was additive to that of 1␣,25(OH) 2 D 3 [IGF-I 60 ng/ml, 181 Ϯ 12.7; 1␣,25(OH) 2 D 3 10 Ϫ12 M, 181 Ϯ 9.8%, IGF-I ϩ 1␣,25(OH) 2 D 3 , 247 Ϯ 16.7%; P Ͻ 0.05 by ANOVA] and specifically obliterated by polyclonal IGF-I antibody (AB-1). Interaction could also be confirmed in suspension cultures. IGFIR mRNA and [ 125 I]-␣IR3 binding was increased by low (10 Ϫ12 M) but not by high (10 Ϫ8 M) concentrations of 1␣,25(OH) 2 D 3. Homologous up-upregulation by IGF-I (60 ng/ml) was specifically inhibited by AB-1 and markedly amplified by coincubation with 1␣,25(OH) 2 D 3 (10 Ϫ12 M). Immunostaining with ␣IR3 showed specific IGFIR expression in rat growth cartilage, but not liver tissue. Stimulation of chondrocytes with 1␣,25(OH) 2 D 3 or IGF-I suggested some increase of receptor expression in single cells, but the predominant effect was increased recruitment of receptor positive cells. Vitamin D receptor expression was markedly stimulated (fourfold) by IGF-I (60 ng/ml), but not IGF-II and inhibited by actinomycin D. This study shows that IGF-I and 1␣,25(OH) 2 D 3 mutually up-regulate their respective receptors in growth plate chondrocytes. In parallel, they have additive effects on cell proliferation and colony formation suggesting independent effector pathways. METHODS Materials 1␣,25(OH) 2-[26,27-methyl-3 H]cholecalciferol (158 Ci/mmol) was obtained from Amersham Buchler (Braunschweig, Germany); unlabeled 1␣,25(OH) 2 D 3 and 1,25(OH) 2 D 3 , were gifts from