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Biomedical subjects

M Pines

Publications and source records attributed to M Pines.

At least 55 records · Page 3Linked to original sources
PubMed1997

Adenylyl cyclase inhibitory pathway is differentially modified in rat white and brown fat by high-energy diets.

Incubation of white adipose tissue (WAT) adipocytes from rats fed a high-energy diet (Exp group) with antilipolytic Gi-coupled adenylyl cyclase inhibitory agonists, nicotinic acid (Nic) and N8-(L-2-phenylisopropyl)adenosine (PIA), resulted in lower cellular adenosine 3',5'-cyclic monophosphate (cAMP) levels than in stimulated adipocytes from rats fed a nutritionally balanced diet (Con group). In contrast to WAT, incubation of brown adipose tissue (BAT) adipocytes with Nic yielded higher cAMP levels in the Exp vs. Con rats. In both WAT and BAT adipocytes, pertussis toxin treatment abolished the differences in Nic- and PIA-inhibited cAMP formation between Exp and Con animals. Immunoblotting of adipocyte membranes indicated a lower content of Gi alpha but not Gs alpha in BAT membranes of Exp vs. Con animals after 6 and 10 wk of feeding. No such differences were found in the Gs alpha or Gi alpha contents of WAT membranes. Thus the inhibitory pathway of adenylyl cyclase is proposed to be sensitized in WAT and desensitized in BAT of rats fed high-energy diets. These modifications in sensitivity are in line with reduced cAMP and lipolysis in WAT and increased cAMP and thermogenesis in BAT during obesity.

Adenylyl Cyclase Inhibitors↗
PubMed1997

Cloning, expression, and tissue localization of the calcium-sensing receptor in chicken (Gallus domesticus).

In previous studies, we characterized an extracellular Ca2+ (Cao(2+))-sensing receptor (CaR) that plays a central role in regulating parathyroid hormone secretion in mammals by sensing Cao2+. In the present study, we have cloned and characterized the chicken (Gallus domesticus) homolog of the CaR. The chicken parathyroid CaR shares a high degree of homology (84% amino acid identity) with the human CaR and displays a similar topology. Moreover, amino acid residues where mutations cause disorders of Cao(2+)-sensing in the human CaR share the wild-type human sequence in the chicken CaR. However, a single region in the extracellular domain of the chicken CaR differs substantially from its mammalian homologs. Xenopus laevis oocytes injected with chicken CaR cRNA respond to elevated ambient levels of Cao2+, extracellular Mg2+, or extracellular Gd3+ with the characteristic activation of inositol trisphosphate-dependent, intracellular Ca(2+)-induced Cl- currents elicited by mammalian CaRs as well as by G protein-linked receptors coupled to activation of phospholipase C. By in situ hybridization, clusters of cells in chicken parathyroid glands were shown to express CaR messenger RNA. Northern analysis and immunohistochemistry demonstrated expression of receptor transcripts and/or protein in kidney tubules and intestine as well as in brain. The close conservation of the amino acid sequence of the chicken CaR with its mammalian homologs as well as its similar tissue distribution suggest that the receptor may also play an important role in avian calcium homeostasis.

Amino Acid Sequence↗
PubMed1997

Inhibition of collagen synthesis, smooth muscle cell proliferation, and injury-induced intimal hyperplasia by halofuginone.

Proliferation of vascular smooth muscle cells (SMCs) and accumulation of extracellular matrix (ECM) components within the arterial wall in response to local injury are important etiologic factors in vascular proliferative disorders such as arteriosclerosis and restenosis after angioplasty. Fibrillar and nonfibrillar collagens are major constituents of the ECM that modulate cell shape and proliferative responses and thereby contribute to the pathogenesis of intimal hyperplasia. Halofuginone, an anticoccidial quinoazolinone derivative, inhibits collagen type I gene expression. We investigated the effect of halofuginone on (1) proliferation of bovine aortic endothelial cells and SMCs derived from the same specimen and maintained in vitro, (2) ECM deposition and collagen type I synthesis and gene expression, and (3) injury-induced intimal hyperplasia in vivo. DNA synthesis and proliferation of vascular SMCs in response to serum or basic fibroblast growth factor were abrogated in the presence of as little as 0.1 microgram/mL halofuginone; this inhibition was reversible upon removal of the compound. Under the same conditions, halofuginone exerted a relatively small antiproliferative effect on the respective vascular endothelial cells. Halofuginone also inhibited the synthesis and deposition of ECM components by vascular SMCs as indicated both by a substantial reduction in the amount of sulfated proteoglycans and collagen type I synthesis and gene expression. Local administration of halofuginone in the rabbit ear model of crush injury-induced arterial intimal hyperplasia resulted in a 50% reduction in intimal thickening as measured by a morphometric analysis of the neointima/media ratio. The differential inhibitory effect of halofuginone on vascular SMCs versus endothelial cells, its inhibition of ECM deposition and collagen type I synthesis, and its ability to attenuate injury-induced intimal hyperplasia may place halofuginone alone or in combination with other antiproliferative compounds as a potential candidate for prevention of arterial stenosis and accelerated atherosclerosis.

Animals↗
PubMed1996

Inhibition of collagen type I synthesis by skin fibroblasts of graft versus host disease and scleroderma patients: effect of halofuginone.

The effect of halofuginone (a plant alkaloid) on collagen alpha 1(I) gene expression and collagen synthesis was evaluated in human skin fibroblasts from patients with chronic graft-versus-host disease (cGvHD) or scleroderma and from a normal individual. Halofuginone caused a dose-dependent inhibition in collagen alpha 1(I) gene expression and collagen synthesis in all cultures tested, the cGvHD fibroblasts being the least sensitive. In normal and scleroderma fibroblasts, concentrations of halofuginone as low as 10(-10) M and 10(-9) M were sufficient to cause a significant reduction in collagen alpha 1(I) gene expression and collagen synthesis, respectively. In addition, halofuginone also inhibited the transforming growth factor beta-induced collagen synthesis. Three days after halofuginone removal, collagen gene expression returned to control levels. The reduction of collagen mRNA transcript levels by halofuginone appeared to be dependent on new protein synthesis because simultaneous treatment of fibroblasts with protein synthesis inhibitors prevents the suppressive effect of halofuginone on collagen alpha 1(I) mRNA gene expression. The ability of extremely low concentrations of halofuginone to inhibit collagen alpha 1(I) synthesis specifically and transiently at the transcriptional level suggests that this material may be an important tool for studying collagen alpha 1(I) gene regulation and may be used as a novel and promising antifibrotic therapy.

Adult↗
PubMed1996

Immunolocalization of osteonectin in avian tibial dyschondroplastic cartilage.

Osteonectin is an acidic calcium-binding protein found in cartilage, bone matrix, vascular endothelium, and areas of tissue repair. Using immunocytochemistry, osteonectin has been localized in all zones of the normal avian epiphyseal growth plate with notably high amounts in the hypertrophic zone. In the proximal portion of this zone the staining was intracellular, while in the distal calcifying portion of the hypertrophic zone staining was both intracellular and extracellular. Osteonectin was also detected in the growth plate associated with lesions of chickens with tibial dyschondroplasia (TD). Intense intracellular staining was observed in hypertrophic chondrocytes proximal to the lesion; staining was markedly diminished in the TD lesion; extracellular matrix was devoid of staining. Staining intensity was high along the peripheral edges of the lesion that were undergoing vascularization and resorption. This was the only area in the dysplastic cartilage where staining was observed in the extracellular matrix as well as intracellularly. Similar patterns were viewed in all TD lesions examined, whether they were spontaneous or induced by dietary treatments or genetic selection.

Animals↗
PubMed1996

Inositol 1-,4-,5-trisphosphate-dependent Ca2+ signaling by the recombinant human PTH/PTHrP receptor stably expressed in a human kidney cell line.

We previously reported the preparation and partial characterization of a series of human embryonic kidney cell lines (HEK-293) stably expressing various numbers of the recombinant human (h) parathyroid hormone (PTH)/PTH-related protein (PTHrP) receptor (Rc). Using this expression system we examined ligand (PTH or PTHrP) binding characteristics and cyclic AMP responsiveness. We have now extended these studies to investigate the calcium signal transduction pathways activated by the hPTH/PTHrP Rc. In parental HEK-293 cells, which lack endogenous PTH/PTHrP Rc, incubation with hPTH(1-34) had no effect on cytosolic free Ca2+ concentration [Ca2+]i. In HEK-293 clone C-21, stably expressing approximately 400,000 Rc/cell, PTH stimulated an increase in [Ca2+]i by Ca2+ release from intracellular stores; PTH released Ca2+ exclusively from the IP3 sensitive Ca2+ pool. Unlike previous studies, the ability of PTH to elicit both cAMP responses and [Ca2+]i transients occurred over a wide range of Rc numbers (between 400,000 and 3000 Rc/cell); both responses were always observed at PTH concentrations in the same dose range although the magnitude of the responses decrease with Rc number. Pretreatment of C-21 cells with pertussis toxin for 24 h, which significantly enhanced PTH-stimulated cAMP accumulation, did not modulate PTH-stimulated [Ca2+]i transients. At each PTH concentration tested which resulted in increased cAMP levels, there was also an increase in [Ca2+]i transients. Treatment of C-21 cells with a battery of midregion and C-terminal PTH or PTHrP peptides showed no effect on either [Ca2+]i transients or cAMP accumulation, indicating a lack of functional interactions between these peptides and the form of the hPTH/PTHrP Rc stably expressed in these cells. Immunological analysis of G-protein expression demonstrated the presence of Gs, Gi, and Gq in all parental and transfected cells lines examined. Taken together, these data demonstrate that the hPTH/PTHrP Rc, stably expressed in HEK-293 cells, elicits responses in both the cAMP and IP3-dependent [Ca2+]i pathways and is responsive only to N-terminal PTH/PTHrP peptides.

Blotting, Western↗
PubMed1996

Comparison of fatigue for three prefabricated threaded post systems.

Post designs may have a direct effect on fracture resistance of endodontically treated teeth. This in vitro study compared the resistance of three prefabricated threaded post systems with lateral shearing forces. After endodontics were completed, prefabricated posts were inserted according to the manufacturer's instructions. A silver amalgam core was placed, and extracted human teeth were prepared to a standard size with a 1 mm gingival chamfer finished on sound dentino A cast was fabricated and cemented, and the specimens were thermocycled. The test samples were secured to an Instron testing machine and loaded until failure. Fracture patterns were recorded, fractured surface areas were measured, and compressive stresses were calculated. However, there were no statistically significant differences among threaded posts in each test group.

Cementation↗
PubMed1996

Inhibition of collagen synthesis and changes in skin morphology in murine graft-versus-host disease and tight skin mice: effect of halofuginone.

The effect of halofuginone, a plant alkaloid known to inhibit collagen type I synthesis, on skin collagen content and skin morphology was evaluated in two in vivo models of scleroderma: the murine chronic graft-versus-host disease (cGvHD) and the tight skin mouse. Skin collagen was assessed by hydroxyproline levels in skin biopsies and by immunohistochemistry using anti-collagen type I antibodies. Daily intraperitoneal injections of halofuginone (1 microgram/mouse) for 52 d starting 3 d before spleen cell transplantation, abrogated the increase in skin collagen and prevented the thickening of the dermis and the loss of the subdermal fat, all of which are characteristic of the cGvHD mice. Halofuginone had a minimal effect on collagen content of the control mice. The halofuginone-dependent decrease in skin collagen content was concentration-dependent and was not accompanied by changes in body weight in either the cGvHD or the control mice. Injections of halofuginone (1 microgram/mouse) for 45 d caused a decrease in the collagen content and dermis width in tight skin mice, but did not affect the dermis width of control mice. Collagen content determination from skin biopsies confirmed the immunohistochemical results in the same mice. The low concentration of halofuginone needed to prevent collagen deposition in fibrotic skin without affecting body weight suggests that halofuginone may serve as a novel and promising anti-fibrotic therapy.

Animals↗
PubMed1996

Control of cell proliferation by embryonal-origin factors.

Embryogenesis can be paralleled and contrasted with cancerous cell proliferation; both embryogenesis and cancer are associated with extremely rapid cell proliferation. However, unlike cancer, embryogenesis is characterized by a delicate balance of proliferative and anti-proliferative processes. We have found two chromatographically separated fractions derived from human embryonal neural tissue extracts that significantly suppress the proliferation of human breast cancer cells. The reduction in cell number was time dependent, with maximal inhibition (70%) observed after 4 days of incubation while maintaining cell viability. The anti-proliferative effect was also evidenced by decreased [3H]-thymidine incorporation. Significant inhibition of proliferation of osteosarcoma, fibrosarcoma, and Balb/c 3T3 cell lines was also obtained with a low concentration of the active fractions. Embryonal factors inhibited mouse and rat cell lines, indicating cross-species effectiveness. The SDS-PAGE of the biologically active approximately 10.7 kDa region revealed several protein bands, while the biologically active approximately 4.5 kDa fraction contained only weakly stainable bands. Thus, the embryo contains factors that control the proliferation of malignant cells. These potent and possibly novel compounds should be investigated for their potential therapeutic role in cancer and other proliferative disorders.

3T3 Cells↗
PubMed1996

Reduction in pulmonary fibrosis in vivo by halofuginone.

Pulmonary fibrosis is a disorder causing a high mortality rate for which therapeutic options are limited. Therefore, the effect of halofuginone, a novel inhibitor of collagen type I synthesis, on bleomycin-induced pulmonary fibrosis was studied in rats. Pulmonary fibrosis was induced by intraperitoneal injections of bleomycin for seven consecutive days, and halofuginone was administered intraperitoneally every second day during the entire experimental period of 42 d. Collagen determination in the lungs and the examination of histologic sections showed that halofuginone significantly reduced fibrosis relative to the untreated control rats. We conclude that halofuginone is a potent in vivo inhibitor of bleomycin-induced pulmonary fibrosis, and that it may potentially be used as a novel therapeutic agent for the treatment of this dysfunction.

Animals↗
PubMed1996

The human PTH2 receptor: binding and signal transduction properties of the stably expressed recombinant receptor.

We have generated a series of stably transfected HEK-293 cell lines expressing the newly identified alternate human PTH receptor (hPTH2 receptor). This receptor subtype is selectively activated by N-terminal PTH-(1-34) and not the corresponding N-terminal (1-34) region of the functionally and structurally related hormone, PTH-related protein (PTHrP). A total of 20 distinct clones displaying different levels of PTH-responsive cAMP production were analyzed. None responded to PTHrP-(1-34). One of these clones (BP-16), displaying maximal PTH responsiveness, was chosen for more detailed evaluation. The BP-16 clone (and the parental HEK-293 cell line lacking both the hPTH/PTHrP receptor and the hPTH2 receptor) were examined for PTH binding, PTH-stimulated cAMP accumulation, PTH-stimulated changes in intracellular calcium ([Ca2+]i) levels, and hPTH2 receptor messenger RNA expression. In addition, we studied the photomediated cross-linking of a potent PTH agonist, namely [Nle8,18,Lys13 (epsilon-pBz2), 2-L-Nal23,Tyr34]bPTH(1-34)NH2 (K13), to the hPTH2 receptor on BP-16 cells. Photoaffinity cross-linking identified an approximately 90-kDa cell membrane component that was specifically competed by PTH-(1-34) and other receptor-interacting ligands. PTH-(1-34) and K13 are potent stimulators of both cAMP accumulation and increases in (Ca2+]i levels, and both bind to the hPTH2 receptor with high affinity (apparent Kd, 2.8 +/- 0.9 x 10(-8) and 8.5 +/- 1.7 x 10(-8) M, respectively). There was no apparent binding, cAMP-stimulating activity, or [Ca 2+]i signaling observed, nor was specific competition vs. binding of a PTH-(1-34) radioligand ([125I]PTH) with PTHrP-(1-34)NH2 found. PTHrP-(1-34) failed to inhibit cross-linking of the hPTH2 receptor by radiolabeled K13 ([125I]K13). However, effective competition vs. [125I]PTH and [125I]K13 binding and [125I]K13 cross-linking were observed with the potent PTH/PTHrP receptor antagonists, PTHrP-(7-34)NH2 and PTH-(7-34)NH2. PTHrP-(7-34)NH2 was shown to be a partial agonist that weakly stimulates both cAMP accumulation and increases in [Ca 2+]i levels in BP-16 cells. These data suggest that the hPTH2 receptor is distinct from the hPTH/PTHrP receptor in the structural features it requires for ligand binding in the family of PTH and PTHrP peptides.

Calcium↗
PubMed1996

Topically applied halofuginone, an inhibitor of collagen type I transcription, reduces peritendinous fibrous adhesions following surgery.

To test in vivo the effect of previously observed inhibition of collagen type I transcription by the plant alkaloid Halofuginone, deep flexor tendons of 12 chickens were severed and sutured, and Halofuginone was applied topically at the site of surgery. Intact tendons, and severed but untreated tendons served as controls. The effect of the treatment was assessed by histological, biochemical, and biomechanical examinations of the operated and intact tendons three weeks after surgery. The results indicated an almost complete absence of fibrous peritendinous adhesions in the histologic sections of the Halofuginone treated tendons. There was a statistically significant decrease in collagen contents of and in both force and energy required to pull out the Halofuginone treated tendons from their sheath, relative to the untreated controls. Halofuginone had no effect on the cellularity of the healing tissue. We conclude that Halofuginone is a potent inhibitor of fibrous peritendinous adhesions with potentially important clinical applications.

Animals↗
PubMed1996

Developmental changes in skin collagen biosynthesis pathway in posthatch male and female chickens.

The developmental changes in skin collagen biosynthesis pathway in male and female chickens were evaluated. Concentration of collagen, levels of mRNA for collagen type I subunits and for lysyl hydroxylase, and the level of three lysyl oxidase-derived cross-links: dehydro-dihydroxylysinonorleucine (DHLNL), dehydro-hydroxylysinonorleucine (HLNL), and dehydro-histidinohydroxymerodesmosine (HHMD) were determined during 4 wk posthatching. Skin collagen content increased with age and was higher in males than in females. In both sexes, the expression of the genes coding for alpha 1 and alpha 2 of collagen type I decreased with age: alpha 1(I) gene expression decreased from Day 3 onwards, whereas the reduction in alpha 2(I) gene expression started 1 wk later. At all ages examined, the expression of both genes was higher in male than in female skin. Males and females lysyl hydroxylase gene expression remained low until Day 16, after which an increase in the enzyme gene expression was observed. An increase in skin HLNL content was observed from Day 3 in both sexes reaching a peak in males at Day 9 and in females 1 wk later. The DHLNL content, which was higher in males than in females at all ages tested, dramatically decreased in both male and female skin from 3 d of age, reaching its lowest level at Day 16, and remained at that low level thereafter. The skin content of HHMD in males and females followed an oscillatory behavior with higher peaks in the male skin. The results suggest that the higher tensile strength of male skin than female skin may be due to the elevated skin collagen content that resulted from increased expression in collagen type I genes on the one hand, and from the higher amounts of various collagen cross-links on the other.

Aging↗
PubMed1995

Growth hormone inhibits differentiation of avian epiphyseal growth-plate chondrocytes.

The effect of chicken growth hormone (cGH) on the proliferation and differentiation of avian growth-plate chondrocyte was evaluated in culture. In culture, addition of ascorbic acid to the culture media caused cell differentiation. Treatment of proliferating chondrocytes with cGH caused a time-dependent increase in collagen type II gene expression together with a decrease in the appearance of osteopontin (OPN) in the medium. In addition, the ascorbic acid-dependent increase in alkaline phosphatase (AP) activity was inhibited by cGH. IGF-I, on the other hand, caused an increase in AP activity in the ascorbic acid-treated chondrocytes. In the presence of ascorbic acid, cGH did not affect collagen type II gene expression or the appearance of OPN in the medium. Proliferation of avian growth-plate chondrocytes, in contrast to mammalian chondrocytes, was not stimulated by GH alone, although the presence of cGH was essential for chondrocyte survival in long-term culture. cGH in combination with epidermal growth factor (EGF) stimulated cell proliferation. These results suggest that GH inhibits differentiation in avian growth-plate chondrocytes, thereby sustaining their proliferative state and maintaining their sensitivity to growth factors such as EGF.

Alkaline Phosphatase↗
PubMed1995

Probing the bimolecular interactions of parathyroid hormone and the human parathyroid hormone/parathyroid hormone-related protein receptor. 2. Cloning, characterization, and photoaffinity labeling of the recombinant human receptor.

Parathyroid hormone (PTH) acts to regulate calcium homeostasis by interacting with a G-protein-coupled receptor that also binds PTH-related protein (PTHrP). In this report we describe the cloning, characterization, and biological activity of the cloned human (h) PTH/PTHrP receptor (Rc) and cross-linking of a benzophenone-substituted PTH analog, [Nle8,18,Lys13(epsilon-pBZ2),L-2-Nal23,Tyr34]bPTH(1-34 )NH2(K13), to cells endogenously expressing the Rc and cells transiently or stably transfected with the human Rc. A full-length cDNA clone was isolated and fully sequenced from a human kidney cDNA library. Northern blot analysis of normal human tissues revealed a limited tissue distribution: a single transcript of approximately 2.3 kb was detected in kidney, lung, placenta, and liver. In human embryonic kidney cells (HEK-293, clone C-21) stably transfected with hPTH/PTHrP Rc, a single 85-90 kDa Rc-hormone complex was formed after photolysis in the presence of K13. This covalent cross-linking reaction was specifically inhibited by excess quantities of biologically active 1-34 analogs of bovine (b) PTH or hPTHrP but not by C-terminal and midregion PTH peptides. Photoincorporation of 125I-labeled K13 into the Rc occurred with high efficiency (60-70%), approximately an order of magnitude greater than that achieved with conventional aryl azide cross-linking reagents. These results support the feasibility of our approach for specifically cross-linking a tagged PTH analog to the Rc, as a first step in the effort to identify directly the amino acid residues that constitute the Rc binding site.

Affinity Labels↗
PubMed1995

Synthesis and phosphorylation of osteopontin by avian epiphyseal growth-plate chondrocytes as affected by differentiation.

The regulation of synthesis and phosphorylation of osteopontin in relation to avian epiphyseal growth-plate chondrocyte differentiation was studied in situ and in culture. Osteopontin gene expression was evaluated in the tibia growth-plate of 3-week-old chickens by in situ hybridization. The gene was expressed mainly at the lower hypertrophic zone where cartilage matrix is calcified and endochondral bone formation is initiated. Within the hypertrophic region, a poorly labeled area separated the layer of osteopontin-positive hypertrophic chondrocytes from those associated with endochondral bone formation. In culture, proliferative chondrocytes show no alkaline phosphatase activity in contrast to ascorbic acid-treated chondrocytes which display the enzyme activity. Chondrocytes not treated with ascorbic acid, exhibited lower levels of osteopontin mRNA than the treated cells. The phorbol ester TPA--an activator of protein kinase C--and to a lesser extent FGF but not EGF, stimulated osteopontin gene expression. Chondrocytes secreted low levels of phosphorylated osteopontin to the medium. EGF treatment resulted in the appearance of phosphorylated osteopontin in the medium, without affecting the synthesis of other proteins. FGF and TGF beta, but not IGF-I or IGF-II, also caused phosphorylation of osteopontin. Ascorbic acid-treated chondrocytes secreted higher levels of phosphorylated osteopontin than the non-treated cells, but addition of FGF or TPA did not stimulate osteopontin phosphorylation any further. Parathyroid hormone caused a dose-dependent attenuation of osteopontin phosphorylation and inhibited the EGF-dependent osteopontin phosphorylation. The results suggest that osteopontin gene expression and phosphorylation in chondrocytes are regulated by separate mechanisms. The response to the various controlling agents varies with the state of differentiation. Both processes--the synthesis and phosphorylation of osteopontin--are under the control of local growth factors which are involved in bone growth and calcification.

Alkaline Phosphatase↗
PubMed1995

Osteopontin gene expression and alkaline phosphatase activity in avian tibial dyschondroplasia.

Osteopontin (OPN) gene expression and alkaline phosphatase activity were evaluated in the epiphyseal growth plates of normal chickens and in diet-induced tibial dyschdroplasia (TD)-afflicted chickens. In the normal growth plate, OPN gene was expressed by a) cells of the subperichondrial zone surrounding the articular cartilage, b) a narrow layer of hypertrophic chondrocytes at the hypertrophic zone, and c) lower hypertrophic chondrocytes at the zone of matrix calcification and endochondral bone formation. The latter two layers were separated by OPN-negative chondrocytes. Osteopontin gene was not expressed throughout the zone of articular cartilage in the nonhypertrophic or upper hypertrophic portions of the growth plate cartilage. Only at sites of calcification of the lower hypertrophic zone was the expression of the OPN gene associated with alkaline phosphatase activity. In all TD lesions, regardless of the induction procedure, the layer of chondrocytes of the lower hypertrophic zone expressing the OPN gene and the layer of OPN-negative cells separating the two areas of OPN-expressing cells were grossly enlarged. This resulted in a wide discontinuity between the chondrocytes of the lower hypertrophic zone expressing the OPN gene and the cells expressing the OPN gene that are associated with mineralization. In TD, no alkaline phosphatase activity was detected within the growth plate cartilage, but normal OPN gene expression was observed at the subperichondrium zone and at the zone of endochondral bone formation. The results of this study suggest that in the epiphyseal growth plate, OPN expression is not restricted to sites of bone calcification.

Alkaline Phosphatase↗