The Actions of IGF-1 in the Growth Plate and Its Role in Postnatal Bone Elongation

Solute delivery to avascular cartilaginous plates is critical to bone elongation, and impaired transport of nutrients and growth factors in cartilage matrix could underlie many skeletal abnormalities. Advances in imaging technology have revolutionized our ability to visualize growth plates in vivo, but quantitative methods are still needed. We developed analytical standards for measuring solute delivery, defined by amount and rate of intravenous tracer entry, in murine growth plates using multiphoton microscopy. We employed an acute temperature model because of its well-established impact on bone circulation and tested the hypothesis that solute delivery changes positively with limb temperature when body core and respiration are held constant (36°C, 120 breaths/min). Tibial growth plates were surgically exposed in anesthetized 5-wk-old mice, and their hindlimbs were immersed in warm (36°C) or cool (23°C) saline ( n = 6/group). After 30 min of thermal equilibration, we administered an intracardiac injection of fluorescein (50 μl, 0.5%) and captured sequentially timed growth plate images spanning 10 min at standardized depth. Absolute growth plate fluorescence was normalized to vascular concentrations for interanimal comparisons. As predicted, more fluorescein infiltrated growth plates at 36°C, with standardized values nearly double those at 23°C. Changing initial limb temperature did not alter baseline values, suggesting a sustained response period. These data validate the sensitivity of our system and have relevance to strategies for enhancing localized delivery of therapeutic agents to growth plates of children. Applications of this technique include assessment of solute transport in models of growth plate dysfunction, particularly chondrodysplasias with matrix irregularities.

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Exercise mitigates the stunting effect of cold temperature on limb elongation in mice by increasing solute delivery to the growth plate

Journal of Applied Physiology ◽

10.1152/japplphysiol.01022.2010 ◽

2010 ◽

Vol 109 (6) ◽

pp. 1869-1879 ◽

Cited By ~ 14

Author(s):

Maria A. Serrat ◽

Rebecca M. Williams ◽

Cornelia E. Farnum

Keyword(s):

Growth Plate ◽

Bone Growth ◽

Wheel Running ◽

Multiphoton Microscopy ◽

Tail Length ◽

Limb Lengthening ◽

Cold Temperature ◽

Bone Lengthening ◽

Bone Elongation

Ambient temperature and physical activity modulate bone elongation in mammals, but mechanisms underlying this plasticity are a century-old enigma. Longitudinal bone growth occurs in cartilaginous plates, which receive nutritional support via delivery of solutes from the vasculature. We tested the hypothesis that chronic exercise and warm temperature promote bone lengthening by increasing solute delivery to the growth plate, measured in real time using in vivo multiphoton microscopy. We housed 68 weanling female mice at cold (16°C) or warm (25°C) temperatures and allowed some groups voluntary access to a running wheel. We show that exercise mitigates the stunting effect of cold temperature on limb elongation after 11 days of wheel running. All runners had significantly lengthened limbs, regardless of temperature, while nonrunning mice had shorter limbs that correlated with housing temperature. Tail length was impacted only by temperature, indicating that the exercise effect was localized to limb bones and was not a systemic endocrine reaction. In vivo multiphoton imaging of fluoresceinated tracers revealed enhanced solute delivery to tibial growth plates in wheel-running mice, measured under anesthesia at rest. There was a minimal effect of rearing temperature on solute delivery when measured at an intermediate room temperature (20°C), suggesting that a lasting increase in solute delivery is an important factor in exercise-mediated limb lengthening but may not play a role in temperature-mediated limb lengthening. These results are relevant to the study of skeletal evolution in mammals from varying environments and have the potential to fundamentally advance our understanding of bone elongation processes.

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Altered IGF-I activity and accelerated bone elongation in growth plates precedes excess weight gain in a mouse model of juvenile obesity

Journal of Applied Physiology ◽

10.1152/japplphysiol.00431.2021 ◽

2022 ◽

Author(s):

Allison L. Machnicki ◽

Cassaundra A. White ◽

Chad A. Meadows ◽

Darby McCloud ◽

Sarah Evans ◽

...

Keyword(s):

Mouse Model ◽

Growth Plate ◽

High Fat Diet ◽

The United States ◽

Growth Patterns ◽

High Fat ◽

Multiphoton Imaging ◽

Growth Plates ◽

Igf I ◽

Bone Elongation

Nearly one-third of children in the United States are overweight or obese by their pre-teens. Tall stature and accelerated bone elongation are characteristic features of childhood obesity, which co-occur with conditions such as limb bowing, slipped epiphyses, and fractures. Obese children paradoxically have normal circulating IGF-I, the major growth-stimulating hormone. Here we describe and validate a mouse model of excess dietary fat to examine mechanisms of growth acceleration in obesity. We used in vivo multiphoton imaging and immunostaining to test the hypothesis that high-fat diet increases IGF-I activity and alters growth plate structure before the onset of obesity. We tracked bone and body growth in male and female C57BL/6 mice (N = 114) on high-fat (60% kcal fat) or control (10% kcal fat) diets from weaning (3-weeks) to skeletal maturity (12-weeks). Tibial and tail elongation rates increased after brief (1-2 week) high-fat diet exposure without altering serum IGF-I. Femoral bone density and growth plate size were increased, but growth plates were disorganized in not-yet-obese high-fat diet mice. Multiphoton imaging revealed more IGF-I in the vasculature surrounding growth plates of high-fat diet mice, and increased uptake when vascular levels peaked. High-fat diet growth plates had more activated IGF-I receptors and fewer inhibitory binding proteins, suggesting increased IGF-I bioavailability in growth plates. These results, which parallel pediatric growth patterns, highlight the fundamental role of diet in the earliest stages of developing obesity-related skeletal complications and validate the utility of the model for future studies aimed at determining mechanisms of diet-enhanced bone lengthening.

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Dephosphorylation of the NPR2 guanylyl cyclase contributes to inhibition of bone growth by fibroblast growth factor

10.1101/193847 ◽

2017 ◽

Author(s):

Leia C. Shuhaibar ◽

Jerid W. Robinson ◽

Ninna P. Shuhaibar ◽

Jeremy R. Egbert ◽

Giulia Vigone ◽

...

Keyword(s):

Growth Factor ◽

Fibroblast Growth Factor ◽

Growth Plate ◽

Cyclic Gmp ◽

Guanylyl Cyclase ◽

Bone Growth ◽

Fibroblast Growth ◽

Fgf Receptor ◽

Activating Mutations ◽

Bone Elongation

AbstractActivating mutations in fibroblast growth factor (FGF) receptor 3 and inactivating mutations in the NPR2 guanylyl cyclase cause similar forms of dwarfism, but how these two signaling systems interact to regulate bone growth is poorly understood. Here, by use of a mouse model in which NPR2 cannot be dephosphorylated, we show that bone elongation is opposed when NPR2 is dephosphorylated and thus produces less cyclic GMP. By developing an in vivo imaging system to measure cyclic GMP levels in intact tibia, we show that FGF-induced dephosphorylation of NPR2 decreases its guanylyl cyclase activity in growth plate chondrocytes in living bone. Thus FGF signaling lowers cyclic GMP in the growth plate, which counteracts bone elongation. These results define a new component of the signaling network by which activating mutations in the FGF receptor inhibit bone growth.

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Enhanced IGF‐I Delivery to the Growth Plate and Accelerated Bone Elongation in a Mouse Model of Juvenile Obesity

The FASEB Journal ◽

10.1096/fasebj.2019.33.1_supplement.774.23 ◽

2019 ◽

Vol 33 (S1) ◽

Author(s):

Maria A Serrat ◽

Allison L Machnicki ◽

Chad A Meadows ◽

Darby McCloud ◽

Dominic Thomas ◽

...

Keyword(s):

Mouse Model ◽

Growth Plate ◽

Igf I ◽

Juvenile Obesity ◽

Bone Elongation

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Effects of Hypophysectomy on the Occurrence and Calcifiability of Matrix Vesicles in the Epiphyseal Growth Plate of Immature Rats

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s1431927600002579 ◽

1980 ◽

Vol 38 ◽

pp. 578-579

Author(s):

S. I. Coleman ◽

W. J. Dougherty

Keyword(s):

Growth Plate ◽

Matrix Vesicles ◽

Epiphyseal Growth Plate ◽

Hard Tissue ◽

Hormonal Factors ◽

Post Surgery ◽

Mineral Deposition ◽

Thin Sectioning ◽

Integral Role ◽

Cellular Secretion

In the cellular secretion theory of mineral deposition, extracellular matrix vesicles are believed to play an integral role in hard tissue mineralization (1). Membrane limited matrix vesicles arise from the plasma membrane of epiphyseal chondrocytes and tooth odontoblasts by a budding process (2, 3). Nutritional and hormonal factors have been postulated to play essential roles in mineral deposition and apparently have a direct effect on matrix vesicles of calcifying cartilage as concluded by Anderson and Sajdera (4). Immature (75-85 gm) Long-Evans hooded rats were hypophysectomized by the parapharyngeal approach and maintained fourteen (14) days post-surgery. At this time, the animals were anesthetized and perfusion fixed in cacodylate buffered 2.5% glutaraldehyde. The proximal tibias were quickly dissected out and split sagittally. One half was used for light microscopy (LM) and the other for electron microscopy (EM). The halves used for EM were cut into blocks approximately 1×3 mm. The tissue blocks were prepared for ultra-thin sectioning and transmission EM. The tissue was oriented so as to section through the epiphyseal growth plate from the zone of proliferating cartilage on down through the hypertrophic zone and into the initial trabecular bone. Sections were studied stained (double heavy metal) and unstained.

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MICROCHEMICAL ANALYSIS OF HUMAN TIBIAL GROWTH CARTILAGE IN VARIOUS FORMS OF DWARFISM

Acta Endocrinologica ◽

10.1530/acta.0.0690659 ◽

1972 ◽

Vol 69 (4) ◽

pp. 659-688 ◽

Cited By ~ 16

Author(s):

V. Stanescu ◽

R. Stanescu ◽

J. A. Szirmai

Keyword(s):

Growth Plate ◽

Chondroitin Sulphate ◽

Epiphyseal Plate ◽

Molecular Characteristics ◽

Growth Disorders ◽

Normal Children ◽

Collagen Concentration ◽

Vitamin D Resistant Rickets ◽

Pooled Samples ◽

Tibial Epiphyseal

ABSTRACT Microchemical determinations of glycosaminoglycans and collagen were preformed in isolated histological zones from sections of tibial epiphyseal plate biopsies obtained from children with growth disorders (pituitary dwarfism, congenital myxoedema, Turner's syndrome, Noonan's syndrome, mucopolysaccharidosis type VI, vitamin D resistant rickets and achondroplasia). Alternate sections were used for histochemical localization of glycosaminoglycans and proteins. The values were compared with those found in comparable zones of the growth plate from normal children of the same age. The chondroitin sulphate concentration (% of defatted dry wt.) in the normal epiphyseal plate increased from the resting zone towards the proliferating/hypertrophic zone; collagen exhibited a reverse trend. In some of the pathological biopsies the concentration of chondroitin sulphate was slightly decreased whereas that of collagen was slightly increased. A marked increase in the collagen concentration was found in achondroplasia. The solubility profiles of the cetylpyridinium complexes of the chondroitin sulphate fraction showed three main peaks with slight but characteristic differences in the various zones of the normal cartilage plate. Significant shifts in the proportion of these peaks were observed in several pathological biopsies, indicating possible deviations from the normal molecular characteristics of the chondroitin sulphate. Analysis of the main chondroitin sulphate fraction, obtained from pooled samples of normal tibial growth plate after fractionation on the macroscale, indicated that all three peaks contained both chondroitin-4 sulphate and chondroitin-6 sulphate and that they probably differed in their molecular weight.

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