The first intron of the human alpha 1(I) collagen gene contains a negatively acting element that inhibits transcription of the chloramphenicol acetyltransferase gene driven by either a collagen or an SV40 basal promoter (Bornstein, P., McKay, J., Morishima, J., Devarayalu, S., and Gelinas, R. E. (1987) Proc. Natl. Acad. Sci. U. S. A. 84, in press). We now find that this element is flanked by sequences that both neutralize the inhibitory effect and impart a net positive effect on transcription. A collagen-human <em>growth</em> hormone minigene was constructed in which varying lengths of the collagen intron were retained. Plasmids were transfected into chick tendon <em>fibroblasts</em>, and transcriptional activity was measured by solution hybridization with an antisense RNA probe. The presence of the intact intronic sequence stimulated transcription by a <em>factor</em> of 2-3-fold in comparison with intron-deleted plasmids. However, the isolated negatively acting element inhibited transcription by a <em>factor</em> of 15-<em>20</em>-fold. Surprisingly, this effect was markedly orientation-dependent. Intronic segments flanking the negatively acting element stimulated transcription both when cloned 5' to the collagen promoter in chloramphenicol acetyltransferase-based plasmids and 3' in collagen-human <em>growth</em> hormone constructions. We conclude that expression of the alpha 1(I) collagen gene is controlled by several intronic elements that function coordinately with 5'-flanking and promoter elements.

Keratinocyte <em>growth</em> <em>factor</em> (KGF) is a member of the <em>fibroblast</em> <em>growth</em> <em>factor</em> (FGF) family. KGF exhibits potent mitogenic activity for a variety of epithelial cell types but is distinct from other known FGFs in that it is not mitogenic for <em>fibroblasts</em> or endothelial cells. We report saturable specific binding of 125I-KGF to surface receptors on intact Balb/MK mouse epidermal keratinocytes. 125I-KGF binding was completed efficiently by acidic FGF (aFGF) but with <em>20</em>-fold lower efficiency by basic FGF (bFGF). The pattern of 125I-acidic FGF binding and competition on Balb/MK keratinocytes and NIH/3T3 <em>fibroblasts</em> suggests that these cell types possess related but distinct FGF receptors. Scatchard analysis of 125I-KGF binding suggested major and minor high affinity receptor components (KD = 400 and 25 pM, respectively) as well as a third high capacity/low affinity heparin-like component. Covalent affinity cross-linking of 125I-KGF to its receptor on Balb/MK cells revealed two species of 115 and 140 kDa. KGF also stimulated the rapid tyrosine phosphorylation of a 90-kDa protein in Balb/MK cells but not in NIH/3T3 <em>fibroblasts</em>. Together these results indicate that Balb/MK keratinocytes possess high affinity KGF receptors to which the FGFs may also bind. However, these receptors are distinct from the receptor(s) for aFGF and bFGF on NIH/3T3 <em>fibroblasts</em>, which fail to interact with KGF.

BACKGROUND

There is no effective treatment for systemic sclerosis and related fibrosing diseases. Recently the action of CYP11A1 on vitamin D(3) was shown to produce biologically active <em>20S</em>-hydroxyvitamin D [<em>20</em>(OH)D(3)] and <em>20</em>,23(OH)(2)D(3), <em>20</em>,22(OH)(2)D(3), and 17,<em>20</em>,23(OH)(3)D(3).

OBJECTIVE

Because <em>20</em>(OH)D(3) is noncalcemic (nontoxic) in vivo at very high doses, we evaluated its antifibrogenic activities both in vitro and in vivo. Because it is further metabolized by CYP11A1, we also tested preclinical utilities of its hydroxyderivatives, especially <em>20</em>,23(OH)(2)D(3).

METHODS

Human dermal fibroblasts from scleroderma and normal donors were used to test the efficiency of hydroxyvitamin D derivatives in inhibiting TGF-β1-induced collagen and hyaluronan synthesis and inhibiting cell proliferation. The in vivo activity of <em>20</em>(OH)D(3) was tested using bleomycin-induced sclerosis in C57BL/6 mice.

RESULTS

<em>20</em>(OH)D(3) and <em>20</em>,23(OH)(2)D(3) inhibited TGF-β1-induced collagen and hyaluronan synthesis similarly to 1,25(OH)(2)D(3) in cultured human fibroblasts. Also, <em>20</em>(OH)D(3), <em>20</em>,23(OH)(2)D(3), and 1,25(OH)(2)D(3) suppressed TGF-β1-induced expression of COL1A2, COL3A1, and hyaluronan synthase-2 mRNA, indicating that they regulate these matrix components at the transcriptional level. <em>20</em>(OH)D(3), <em>20</em>,23(OH)(2)D(3), <em>20</em>,22(OH)(2)D(3), and 17,<em>20</em>,23(OH)(3)D(3) inhibited proliferation of dermal fibroblasts with comparable potency with 1,25(OH)(2)D(3), with <em>20</em>(OH)D(2) being less active and 1α(OH)D(3) being almost inactive. <em>20</em>,23(OH)(2)D(3) at 3 μg/kg had no effect on serum Ca(++) or fibroblast growth factor-23 levels and did not cause any noticeable signs of morbidity. <em>20</em>(OH)D(3) markedly suppressed fibrogenesis in mice given sc bleomycin as demonstrated by total collagen content and hematoxylin and eosin staining of skin biopsies.

CONCLUSIONS

<em>20</em>(OH)D(3) is an excellent candidate for preclinical studies on scleroderma, with other CYP11A1-derived products of its metabolism deserving further testing for antibrogenic activity.

Pulmonary fibrosis is a progressive scarring disease with no effective treatment. Transforming <em>growth</em> <em>factor</em> (TGF)-beta is up-regulated in fibrotic diseases, where it stimulates differentiation of <em>fibroblasts</em> to myo<em>fibroblasts</em> and production of excess extracellular matrix. Peroxisome proliferator-activated receptor (PPAR) gamma is a transcription <em>factor</em> that regulates adipogenesis, insulin sensitization, and inflammation. We report here that a novel PPARgamma ligand, 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid (CDDO), is a potent inhibitor of TGF-beta-stimulated differentiation of human lung <em>fibroblasts</em> to myo<em>fibroblasts</em>, and suppresses up-regulation of alpha-smooth muscle actin, fibronectin, collagen, and the novel myofibroblast marker, calponin. The inhibitory concentration causing a 50% decrease in aSMA for CDDO was <em>20</em>-fold lower than the endogenous PPARgamma ligand, 15-deoxy-Delta(12,14)-prostaglandin J(2) (15 d-PGJ(2)), and 400-fold lower than the synthetic ligand, rosiglitazone. Pharmacologic and genetic approaches were used to demonstrate that CDDO mediates its activity via a PPARgamma-independent pathway. CDDO and 15 d-PGJ(2) contain an alpha/beta unsaturated ketone, which acts as an electrophilic center that can form covalent bonds with cellular proteins. Prostaglandin A(1) and diphenyl diselenide, both strong electrophiles, also inhibit myofibroblast differentiation, but a structural analog of 15 d-PGJ(2) lacking the electrophilic center is much less potent. CDDO does not alter TGF-beta-induced Smad or AP-1 signaling, but does inhibit acetylation of CREB binding protein/p300, a critical coactivator in the transcriptional regulation of TGF-beta-responsive genes. Overall, these data indicate that certain PPARgamma ligands, and other small molecules with electrophilic centers, are potent inhibitors of critical TGF-beta-mediated profibrogenic activities through pathways independent of PPARgamma. As the inhibitory concentration causing a 50% decrease in aSMA for CDDO is 400-fold lower than that in rosiglitazone, the translational potential of CDDO for treatment of fibrotic diseases is high.

Latent transforming <em>growth</em> <em>factor</em>-beta (TGF-beta)-binding protein (LTBP) is a component of the latent TGF-beta complex in human platelets. LTBP is composed of two different cysteine-rich repeat sequences, i.e. epidermal <em>growth</em> <em>factor</em> (EGF)-like repeats and a repeat containing 8 cysteine residues. The overall structure of LTBP is similar to those of the microfibrillar proteins fibrillin-1 and fibrillin-2. Here we report the identification of a novel protein termed LTBP-2, which is structurally related to LTBP. cDNA for LTBP-2 was obtained from human foreskin <em>fibroblast</em> cDNA libraries using a fragment of the LTBP cDNA as a probe. LTBP-2 is composed of <em>20</em> EGF-like repeats and four copies of the 8-cysteine repeat. The amino acid sequence of LTBP-2 is 41% identical to that of LTBP and 25% identical to that of fibrillin-1. LTBP-2 is synthesized as a 240-kDa protein by human foreskin <em>fibroblasts</em> and also by COS cells transfected with the isolated LTBP-2 cDNA. Similar to LTBP, a considerable part of LTBP-2 was found to be associated with extracellular matrix. Co-transfection of cDNAs for LTBP-2 and TGF-beta 1 revealed that LTBP-2 forms a high molecular weight complex with the TGF-beta 1 precursor. The LTBP-2 gene was assigned to chromosome 14q24. These results indicate that different forms of latent TGF-beta complexes occur and suggest that the different associated proteins may function to target the complexes to specific sites.

BACKGROUND

Following various types of plastic surgery, such as adipose grafting and flap elevation, adipose tissue undergoes ischemia, leading to hypoxia and nutrient depletion. However, few studies have examined ischemic and/or hypoxic changes in adipose tissue.

METHODS

The authors established surgically induced ischemia models by severing blood vessels supplying the inguinal fat pads in mice. The partial pressure of oxygen in adipose tissue was measured with an oxygen monitor, and ischemic changes were analyzed by whole-mount staining, immunohistochemistry, flow cytometry, and Western blotting. The authors also examined cell survival under a hypoxic condition in vitro.

RESULTS

Models for three degrees (mild, intermediate, and severe) of ischemia showed approximately 75, 55, and <em>20</em> percent of the partial pressure of oxygen level in normal adipose tissue (50.5±1.3 mm Hg), respectively. Adipose tissue atrophy with substantial fibrosis on day 28 was seen, depending on the severity of ischemia. Intermediate and severe ischemia induced elevated expression of hypoxia-inducible <em>factor</em> 1α and <em>fibroblast</em> <em>growth</em> <em>factor</em> 2 on day 1 and degenerative changes (i.e., apoptosis, necrosis, and macrophage infiltration and phagocytosis) in adipose tissue. Dead cells included adipocytes, vascular endothelial cells, and blood-derived cells, but not adipose-derived stem/progenitor cells. Subsequent to degenerative changes, regenerative changes were seen, including angiogenesis, adipogenesis, and proliferation of cells (adipose-derived stem/progenitor cells, vascular endothelial cells, and blood cells). The authors found that, in vitro, the experimentally differentiated adipocytes underwent apoptosis and/or necrosis under severe hypoxia, but adipose-derived stem/progenitor cells remained viable.

CONCLUSIONS

Severe ischemia/hypoxia induces degenerative changes in adipose tissue and subsequent adaptive tissue remodeling. Adipocytes die easily under ischemic conditions, whereas adipose-derived stem/progenitor cells are activated and contribute to adipose tissue repair.

The purpose of this study was to promote <em>fibroblast</em> proliferation and collagen remodeling in flexor tendon repair through sustained delivery of platelet derived <em>growth</em> <em>factor</em> (PDGF-BB). The release kinetics of PDGF-BB from a novel fibrin matrix delivery system was initially evaluated in vitro. After the in vivo degradation rate of the fibrin matrix was determined using fluorescently tagged fibrin, PDGF-BB was delivered to the site of flexor tendon repair in vivo in a canine model. The effect of PDGF-BB on intrasynovial tendon healing was studied using histology-based assays (cell density, proliferation, and type I collagen expression) and by measuring total DNA levels and reducible collagen crosslink levels. The fibrin matrix delivery system provided sustained release of PDGF-BB in vitro at a rate modulated by the ratio of heparin to <em>growth</em> <em>factor</em>. In vivo, the fibrin matrix remained at the repair site for more than 10 days. Delivery of PDGF-BB led to a qualitative increase in cell density, cell proliferation, and type I collagen mRNA expression. PDGF-BB also led to statistically significant increases in total DNA (<em>20</em>% increase at 7 days, 18% increase at 14 days) and reducible collagen crosslinks (30% increase at 7 days). Sustained delivery of <em>growth</em> <em>factors</em> may be achieved using a novel fibrin-based delivery system. PDGF-BB delivery increased cell proliferation and matrix remodeling and thus may accelerate flexor tendon healing.

We have examined the ability of different neurotrophic and <em>growth</em> <em>factors</em> to prevent axotomy-induced motoneuron cell death in the developing mouse spinal cord. After postnatal unilateral section of the mouse sciatic nerve, most motoneuron (MN) loss occurs in the lateral motor column of the fourth lumbar segment (L4). Significant axotomy-induced cell death occurred after surgery performed on or before postnatal day (PN) 5. In contrast, no significant cell loss was found when axotomy was performed after PN10. Axotomy on PN2 or PN5 resulted in a 44% loss of L4 motoneurons by 7 days, and a 66% loss of motoneurons by 10 days postsurgery. Implantation of gelfoam presoaked in various neurotrophic <em>factors</em> at the lesion site rescued axotomized motoneurons. Nerve <em>growth</em> <em>factor</em> (NGF), neurotrophin-4/5 (NT-4/5) and ciliary neurotrophic <em>factor</em> (CNTF) rescued <em>20</em>%-30% of motoneurons, whereas brain-derived neurotrophic <em>factor</em> (BDNF), neurotrophin-3 (NT-3), and insulin-like <em>growth</em> <em>factor</em> 1 (IGF-1) rescued virtually all motoneurons from axotomy-induced death. By contrast, platelet-derived <em>growth</em> <em>factor</em> (PDGF)-AA, PDGF-AB, basic <em>fibroblast</em> <em>growth</em> <em>factor</em> (bFGF), and interleukin (IL-6) were ineffective on motoneuron survival following axotomy. NGF, BDNF, NT-3, IGF-1, and CNTF also prevented axotomy-induced atrophy of surviving motoneurons. These data show that mouse lumbar motoneurons continue to be vulnerable to axotomy up to about 1 week after birth and that a number of trophic agents, including the neurotrophins, CNTF, and IGF-1, can prevent the death of these neurons following axotomy.(ABSTRACT TRUNCATED AT 250 WORDS)

Uncertainty exists regarding the physiologically relevant <em>fibroblast</em> <em>growth</em> <em>factor</em> (FGF) receptor (FGFR) for FGF23 in the kidney and the precise tubular segments that are targeted by FGF23. Current data suggest that FGF23 targets the FGFR1c-Klotho complex to coordinately regulate phosphate transport and 1,25-dihydroxyvitamin D [1,25(OH)(2)D] production in the proximal tubule. In studies using the Hyp mouse model, which displays FGF23-mediated hypophosphatemia and aberrant vitamin D, deletion of Fgfr3 or Fgfr4 alone failed to correct the Hyp phenotype. To determine whether FGFR1 is sufficient to mediate the renal effects of FGF23, we deleted Fgfr3 and Fgfr4 in Hyp mice, leaving intact the FGFR1 pathway by transferring compound Fgfr3/Fgfr4-null mice on the Hyp background to create wild-type (WT), Hyp, Fgfr3(-/-)/Fgfr4(-/-), and Hyp/Fgfr3(-/-)/Fgfr4(-/-) mice. We found that deletion of Fgfr3 and Fgfr4 in Fgfr3(-/-)/Fgfr4(-/-) and Hyp/Fgfr3(-/-)/Fgfr4(-/-) mice induced an increase in 1,25(OH)(2)D. In Hyp/Fgfr3(-/-)/Fgfr4(-/-) mice, it partially corrected the hypophosphatemia (P(i) = 9.4 ± 0.9, 6.1 ± 0.2, 9.1 ± 0.4, and 8.0 ± 0.5 mg/dl in WT, Hyp, Fgfr3(-/-)/Fgfr4(-/-), and Hyp/Fgfr3(-/-)/Fgfr4(-/-) mice, respectively), increased Na-phosphate cotransporter Napi2a and Napi2c and Klotho mRNA expression in the kidney, and markedly increased serum FGF23 levels (107 ± <em>20</em>, 3,680 ± 284, 167 ± 22, and 18,492 ± 1,547 pg/ml in WT, Hyp, Fgfr3(-/-)/Fgfr4(-/-), and Hyp/Fgfr3(-/-)/Fgfr4(-/-) mice, respectively), consistent with a compensatory response to the induction of end-organ resistance. Fgfr1 expression was unchanged in Hyp/Fgfr3(-/-)/Fgfr4(-/-) mice and was not sufficient to transduce the full effects of FGF23 in Hyp/Fgfr3(-/-)/Fgfr4(-/-) mice. These studies suggest that FGFR1, FGFR3, and FGFR4 act in concert to mediate FGF23 effects on the kidney and that loss of FGFR function leads to feedback stimulation of Fgf23 expression in bone.

Recent studies indicate that insulin-like <em>growth</em> <em>factor</em>-II (IGF-II) acts as an autocrine differentiation <em>factor</em> for skeletal myoblasts in culture. IGF-II mRNA and protein are induced as early events in muscle differentiation, and the rate and extent of IGF-II secretion correlate with both biochemical and morphological differentiation. Here we show that IGF-II also functions as an essential survival <em>factor</em> during the transition from proliferating to differentiating myoblasts. Stably transfected C2 muscle cell lines were established in which a mouse IGF-II cDNA was expressed in the antisense orientation relative to the constitutively active Moloney sarcoma virus promoter. IGF-II antisense cells proliferated normally in <em>growth</em> medium containing <em>20</em>% serum but underwent rapid death when placed in low serum differentiation medium. Death was accompanied by characteristic markers of apoptosis with more than 90% of cells showing DNA fragmentation within 12-16 h. Myoblast death was prevented by IGF-I, des [1-3] IGF-I, IGF-II, and insulin with a dose potency consistent with activation of the IGF-I receptor; death also could be blocked by the protein synthesis inhibitor, cycloheximide. Exogenous IGFs additionally stimulated passage through a single cell cycle and subsequently induced terminal differentiation. Cell survival and cell cycle progression also were enhanced by <em>fibroblast</em> <em>growth</em> <em>factor</em>-2 and platelet-derived <em>growth</em> <em>factor</em>-bb, but these peptides did not promote differentiation. Our results define a novel system for studying apoptotic cell death and its prevention by <em>growth</em> <em>factors</em>, underscore the importance of IGF action in minimizing inappropriate cell death, and indicate that shared signal transduction pathways may mediate myoblast survival in vitro.

Epidermal <em>growth</em> <em>factor</em>, isolated from mouse submaxillary glands (mEGF) and human urine (hEGF; urogastrone), and <em>fibroblast</em> <em>growth</em> (FGF) have been tested for their effect on bone resorption by measuring the release of previously incorporated 45Ca from cultured fetal rat long bone shafts. mEGF produced significant but slow stimulation of bone resorption which was maximal at 30 ng/ml and was not blocked by indomethacin, flufenamic acid, or R0 <em>20</em>-57<em>20</em>, structurally unrelated inhibitors of prostaglandins synthesis. mEGF increased thymidine incorporation in long bones at 1 ng/ml, a concentration which did not stimulate resorption. hEGF at 3-30 ng/ml produced a more rapid stimulation of resorption, which was also unaffected by inhibition of prostaglandin cyclooxygenase. Neither mEGF nor hEGF increased the concentration of prostaglandin E in the medium after 5 days of culture. FGF failed to stimulate resorption at concentrations of up to 1000 ng/ml. We conclude the EGF, but not FGF, is a direct stimulator of bone resorption. In contrast to the previously reported findings in mouse calvaria, this stimulation is not dependent on prostaglandin synthesis. Since there is abundant hEGF in human urine, this <em>factor</em> could be responsible for the calcium-mobilizing activity recently found in human urine concentrates.

Receptor tyrosine kinases (RTKs) have been implicated as therapeutic targets for the treatment of human diseases including cancers, inflammatory diseases, cardiovascular diseases including arterial restenosis, and fibrotic diseases of the lung, liver, and kidney. Three classes of 3-substituted indolin-2-ones containing propionic acid functionality attached to the pyrrole ring at the C-3 position of the core have been identified as catalytic inhibitors of the vascular endothelial <em>growth</em> <em>factor</em> (VEGF), <em>fibroblast</em> <em>growth</em> <em>factor</em> (FGF), and platelet-derived <em>growth</em> <em>factor</em> (PDGF) RTKs. Some of the compounds were found to inhibit the tyrosine kinase activity associated with isolated vascular endothelial <em>growth</em> <em>factor</em> receptor 2 (VEGF-R2) [fetal liver tyrosine kinase 1 (Flk-1)/kinase insert domain-containing receptor (KDR)], <em>fibroblast</em> <em>growth</em> <em>factor</em> receptor (FGF-R), and platelet-derived <em>growth</em> <em>factor</em> receptor (PDGF-R) tyrosine kinase with IC(50) values at nanomolar level. Thus, compound 1 showed inhibition against VEGF-R2 (Flk-1/KDR) and FGF-R1 tyrosine kinase activity with IC(50) values of <em>20</em> and 30 nM, respectively, while compound 16f inhibited the PDGF-R tyrosine kinase activity with IC(50) value of 10 nM. Structural models and structure-activity relationship analysis of these compounds for the target receptors are discussed. The cellular activities of these compounds were profiled using cellular proliferation assays as measured by bromodeoxyuridine (BrdU) incorporation. Specific and potent inhibition of cell <em>growth</em> was observed for some of these compounds. These data provide evidence that these compounds can be used to inhibit the function of these target receptors.

Cultured porcine aortic smooth muscle cells and human <em>fibroblasts</em> produce somatomedinlike peptides and secrete them into the surrounding microenvironment. This production has been linked to their ability to replicate. The objective of this study was to determine if a specific anti-somatomedin-C (Sm-C) monoclonal antibody that binds the somatomedinlike peptides could inhibit replication by porcine aortic smooth muscle cells and human <em>fibroblasts</em>. To determine if the antibody could inhibit the effect of endogenously produced somatomedinlike peptide, increasing concentrations of antibody were co-incubated with platelet-derived <em>growth</em> <em>factor</em>, a known stimulant of somatomedinlike peptide secretion, and Sm-C-deficient platelet-poor plasma. Addition of the antibody reduced <em>fibroblast</em> [3H]thymidine incorporation from 35,100 +/- 500 to 10,600 +/- 700 cpm (P less than 0.001), and in smooth muscle cells from 29,600 +/- 1,800 to 10,800 +/- 1,100 cpm (P less than 0.001). Co-incubation of exogenously added Sm-C (<em>20</em> ng/ml) with maximally inhibitory dilutions of antibody increased [3H]thymidine incorporation in <em>fibroblasts</em> from 7,800 +/- 1,000 to 18,900 +/- 800 cpm (P less than 0.01), and in smooth muscle cells from 9,800 +/- 1,<em>20</em>0 to 17,<em>20</em>0 +/- 1,100 cpm (P less than 0.01). Insulin, which can substitute for Sm-C as a mitogen and does not bind to the antibody, stimulated DNA synthesis when co-incubated with the antibody, thereby excluding the possibility of nonspecific cytotoxicity. These results strengthen the hypothesis that the rate of DNA synthesis of these two cell types in vitro is directly linked to their capacity to produce somatomedinlike peptides. They further support the cellular production of somatomedinlike peptides as examples of the autocrine model of <em>growth</em> regulation.

Site-specific GalNAc-type O-glycosylation is emerging as an important co-regulator of proprotein convertase (PC) processing of proteins. PC processing is crucial in regulating many fundamental biological pathways and O-glycans in or immediately adjacent to processing sites may affect recognition and function of PCs. Thus, we previously demonstrated that deficiency in site-specific O-glycosylation in a PC site of the <em>fibroblast</em> <em>growth</em> <em>factor</em>, FGF23, resulted in marked reduction in secretion of active unprocessed FGF23, which cause familial tumoral calcinosis and hyperostosis hyperphosphatemia. GalNAc-type O-glycosylation is found on serine and threonine amino acids and up to <em>20</em> distinct polypeptide GalNAc transferases catalyze the first addition of GalNAc to proteins making this step the most complex and differentially regulated steps in protein glycosylation. There is no reliable prediction model for O-glycosylation especially of isolated sites, but serine and to a lesser extent threonine residues are frequently found adjacent to PC processing sites. In the present study we used in vitro enzyme assays and ex vivo cell models to systematically address the boundaries of the region within site-specific O-glycosylation affect PC processing. The results demonstrate that O-glycans within at least ±3 residues of the RXXR furin cleavage site may affect PC processing suggesting that site-specific O-glycosylation is a major co-regulator of PC processing.

Here we determine the <em>Fibroblast</em> <em>Growth</em> <em>Factor</em>-2 (FGF2) dependency of the time course of changes in bone mass in female mice. This study extends our earlier reports that knockout of the FGF2 gene (Fgf2) caused low turnover bone loss in Fgf2(-/-) male mice by examining bone loss with age in Fgf2(-/-) female mice, and by assessing whether reduced bone formation is associated with differentiation of bone marrow stromal cells (BMSCs) towards the adipocyte lineage. Bone mineral density (BMD) was similar in 3-month-old female Fgf2(+/+) and Fgf2(-/-) mice but was significantly reduced as early as 5 months of age in Fgf2(-/-) mice. In vivo studies showed that there was a greater accumulation of marrow fat in long bones of 14 and <em>20</em> month old Fgf2(-/-) mice compared with Fgf2(+/+) littermates. To study the effect of disruption of FGF2 on osteoblastogenesis and adipogenesis, BMSCs from both genotypes were cultured in osteogenic or adipogenic media. Reduced alkaline phosphatase positive (ALP), mineralized colonies and a marked increase in adipocytes were observed in Fgf2(-/-) BMSC cultures. These cultures also showed an increase in the mRNA of the adipogenic transcription <em>factor</em> PPARgamma2 as well as the downstream target genes aP2 and adiponectin. Treatment with exogenous FGF2 blocked adipocyte formation and increased ALP colony formation and ALP activity in BMSC cultures of both genotypes. These results support an important role for endogenous FGF2 in osteoblast (OB) lineage determination. Alteration in FGF2 signaling may contribute to impaired OB bone formation capacity and to increased bone marrow fat accumulation both of which are characteristics of aged bone.

Fluid shear stress has been shown to be an important regulator of vascular structure and function through its effect on the endothelial cell. We have explored the effect of shear stress on the expression of the heparin-binding <em>growth</em> <em>factors</em> platelet-derived <em>growth</em> <em>factor</em> B chain (PDGF-B) and basic <em>fibroblast</em> <em>growth</em> <em>factor</em> (bFGF) in bovine aortic endothelial cells using a purpose-built cone-plate viscometer. Using morphometric analysis, we have mimicked the endothelial cell shape changes encountered in vivo in response to shear stress and correlated these with changes in gene expression. Steady laminar shear stress of 15 and 36 dyn/cm2 both resulted in endothelial cell shape change, but the higher shear stress induced greater and more uniform alignment in the direction of flow and nuclear protrusion after 24 h. Steady laminar shear stress of both 15 and 36 dyn/cm2 induced a significant 3.9- and 4.2-fold decrease, respectively, in PDGF-B mRNA at 9 h. In contrast, steady laminar shear of 15 dyn/cm2 induced a mild and transient 1.5-fold increase in bFGF mRNA while shear of 36 dyn/cm2 induced a significant 4.8-fold increase at 6 h of shear which remained at 2.9-fold at 9 h. Pulsatile and turbulent shear stress showed the same effect as steady laminar shear stress (all at 15 dyn/cm2 time-average magnitude) on PDGF-B and bFGF mRNA content. Cyclic stretch (<em>20</em>% strain, <em>20</em>/min) of cells grown on silicone substrate did not significantly affect either PDGF-B or bFGF mRNA levels. These results suggest that expression of each peptide <em>growth</em> <em>factor</em> gene is differentially regulated by fluid shear stress in the vascular endothelial cell. These results may have implications on vascular structure and function in response to hemodynamic forces and present a model for the study of transduction of mechanical stimuli into altered gene expression.

OBJECTIVE

To evaluate the efficacy of low-level laser therapy (LLLT) on collateral circulation and microcirculation if a blood vessel is occluded.

BACKGROUND

Investigators have attempted prostaglandin and ultrasound therapy to promote improvements in the vascular bed of deprived tissue after an injury, which may lead to occlusion of the blood vessels.

METHODS

Thirty-four adult rabbits were used in this study, two of them considered 0-h reading group, while the rest were divided into two equal groups, with 16 rabbits each: control and those treated with LLLT. Each rabbit underwent two surgical operations; the medial aspect of each thigh was slit, the skin incised and the femoral artery exposed and ligated. The site of the operation in the treated group was irradiated directly following the operation and for 3 d after, one session daily for 10 min/session. The laser system used was a gallium-aluminum-arsenide (Ga-Al-As) diode laser with a wavelength of 904 nm and power of 10 mW. Blood samples collected from the femoral artery above the site of the ligation were sent for examination with high-performance liquid chromatography (HPLC) to determine the levels of adenosine, <em>growth</em> hormone (GH) and <em>fibroblast</em> <em>growth</em> <em>factor</em> (FGF). Tissue specimens collected from the site of the operation, consisting of the artery and its surrounding muscle fibers, were sent for histopathological examination to determine the fiber/capillary (F/C) ratio and capillary diameter. Blood samples and tissue specimens were collected at 4, 8, 12, 16, <em>20</em>, 24, 48 and 72 h postoperatively from the animals of both groups, control and treated.

RESULTS

Rapid increases in the level of adenosine, GH, and FGF occurred. The F/C ratio and capillary diameter peaked at 12-16 h; their levels declined gradually, reaching normal values 72 h after irradiation in the treated group. Numerous collateral blood vessels proliferated the area, with marked increases in the diameters of the original blood vessels.

CONCLUSIONS

The results indicated that LLLT accelerated collateral circulation and enhanced microcirculation and seemed to be unique in the normalization of the functional features of the injured area, which could lead to occlusion of the regional blood vessels.

BACKGROUND

It has been reported that interleukin (IL)-1 is associated with pathological cardiac remodeling and LV dilatation, whereas IL-1beta has also been shown to induce cardiomyocyte hypertrophy. Thus, the role of IL-1 in the heart remains to be determined.

OBJECTIVE

We studied the role of hypertrophy signal-mediated IL-1beta/insulin-like growth factor (IGF)-1 production in regulating the progression from compensative pressure-mediated hypertrophy to heart failure.

RESULTS

Pressure overload was performed by aortic banding in IL-1beta-deficient mice. Primarily cultured cardiac fibroblasts (CFs) and cardiac myocytes (CMs) were exposed to cyclic stretch. Heart weight, myocyte size, and left ventricular ejection fraction were significantly lower in IL-1beta-deficient mice (20%, 23% and 27%, respectively) than in the wild type 30 days after aortic banding, whereas interstitial fibrosis was markedly augmented. DNA microarray analysis revealed that IGF-1 mRNA level was markedly (approximately 50%) decreased in the IL-1beta-deficient hypertrophied heart. Stretch of CFs, rather than CMs, abundantly induced the generation of IL-1beta and IGF-1, whereas such IGF-1 induction was markedly decreased in IL-1beta-deficient CFs. IL-1beta released by stretch is at a low level unable to induce IL-6 but sufficient to stimulate IGF-1 production. Promoter analysis showed that stretch-mediated IL-1beta activates JAK/STAT to transcriptionally regulate the IGF-1 gene. IL-1beta deficiency markedly increased c-Jun N-terminal kinase (JNK) and caspase-3 activities and enhanced myocyte apoptosis and fibrosis, whereas replacement of IGF-1 or JNK inhibitor restored them.

CONCLUSIONS

We demonstrate for the first time that pressure-mediated hypertrophy and mechanical stretch generates a subinflammatory low level of IL-1beta, which constitutively causes IGF-1 production to maintain adaptable compensation hypertrophy and inhibit interstitial fibrosis.

In the present study we have analyzed and compared, by immunohistochemistry and in situ hybridization, the expression pattern of the R4/ALK5 transforming <em>growth</em> <em>factor</em> (TGF)-beta type I receptor (RI) and the TGF-beta type II receptor (RII) in normal human skin, in wounded skin at various stages during the transition of wound granulation tissue to scar, and in long-persisting post-burn hypertrophic scars. In normal human skin, expression of RI and RII was clearly visible in the epidermis, in epidermal appendages, and in vascular cells, although only a small number of dermal <em>fibroblasts</em> revealed detectable levels of TGF-beta receptor expression. In contrast, granulation tissue <em>fibroblasts</em> showed strong expression of both TGF-beta receptor types, although in normal-healing excisional wounds their density decreased during granulation tissue remodeling. However, in post-burn hypertrophic scars, RI- and RII-overexpressing <em>fibroblasts</em> were found in high densities up to <em>20</em> months after injury. From these findings we suggest that the repair process of deep wounds involves the transformation of a subset of fibroblastic cells toward an increased TGF-beta responsiveness and a transient accumulation of these cells at the wound site. In addition, our study provides evidence that excessive scarring is associated with a failure to eliminate TGF-beta receptor-overexpressing <em>fibroblasts</em> during granulation tissue remodeling, which leads to a persistent autocrine, positive feedback loop that results in over-production of matrix proteins and subsequent fibrosis.

Human diploid <em>fibroblasts</em> (IMR-90) regulate their overall rates of proteolysis in response to the composition of the culture medium and the ambient temperature. The magnitude and, in some cases, the direction of the response depend on the half-lives of the cellular proteins that are radioactively labeled and the time chosen for measurements of protein degradation. Fetal calf serum, insulin, <em>fibroblast</em> <em>growth</em> <em>factor</em>, epidermal <em>growth</em> <em>factor</em>, and amino acids selectively regulate catabolism of long-lived proteins without affecting degradation of short-lived proteins. Fetal calf serum reduces degradative rates of long-lived proteins and is maximally effective at a concentration of <em>20</em>%, but the effect of serum on proteolysis is evident only for the first 24 hr. Insulin inhibits degradation of long-lived proteins in the presence or absence of glucose and amino acids in the medium, but is maximally effective only at high concentrations (10(-5) M). Amino acid deprivation increases degradative rates of long-lived proteins for the first 6 hr, but then decreases their catabolism for the subsequent <em>20</em> hr. Lowered temperature is the only condition tested that significantly alters degradative rates of short-lived proteins. Although cells incubated at 27 degrees C have reduced rates of degradation for both short-lived and long-lived proteins compared to cells at 37 degrees C, lowered temperature reduces catabolism of long-lived proteins to a greater extent.

Epidermal <em>growth</em> <em>factor</em> (EGF) is a potent mitogen in vitro, but its biological role is less clear. The vulnerary effects of EGF were evaluated in a model of wound repair, the polyvinyl alcohol sponge implanted subcutaneously in rats. EGF was purified to homogeneity by reverse-phase HPLC and quantified by receptor binding assay and amino acid analysis. Preliminary data showed moderate promotion of granulation tissue formation by daily injections of 10 micrograms of EGF. To test the hypothesis that long-term exposure to EGF is required for complete cellular response, the <em>factor</em> was incorporated into pellets releasing 10 or <em>20</em> micrograms of biologically active EGF per day, and the pellets were embedded within the sponges. Slow release of EGF caused a dramatic increase in the extent and organization of the granulation tissue at day 7, a doubling in the DNA content, and 33% increases in protein content and wet weight, as compared with placebo controls. Although collagen content was also increased by almost 50%, the relative rate of collagen synthesis remained the same, suggesting that the morphological and biochemical increase in collagen resulted from increased numbers of <em>fibroblasts</em> rather than a specific stimulation of collagen synthesis. These results indicate that the local sustained presence of EGF accelerates the process of wound repair, specifically neovascularization, organization by <em>fibroblasts</em>, and accumulation of collagen.

Human bone marrow contains a distinct cell population that expresses bone proteins and responds to transforming <em>growth</em> <em>factor</em> beta 1 (TGF-beta), but not to hematopoietic <em>growth</em> <em>factors</em> (Long, M. W., J. L. Williams, and K. G. Mann. 1990. J. Clin. Invest. 86:1387-1395). We now report the isolation, characterization, and <em>growth</em> <em>factor</em> responsiveness of these precursors to human osteoblasts and the identification of a human osteoprogenitor cell. Immunological separation of human bone marrow nonadherent low-density (NALD) cells results in a marked enrichment of cells that express osteocalcin, osteonectin, and bone alkaline phosphatase. Flow cytometric analyses show that distinct cell subpopulations exist among these isolated cells. The majority of the bone antigen-positive cells are approximately the size of a lymphocyte, whereas other, less frequent antibody-separated subpopulations consist of osteoblast-like cells and osteoprogenitor cells. In serum-free cultures, TGF-beta stimulates the small, antigen-positive cells to become osteoblast-like, as these cells both increase in size, and express increased levels of osteocalcin and alkaline phosphatase. Antibody-separated cells also contain a separate population of clonal progenitor cells that form colonies of osteoblast-like cells when cultured in serum-free, semi-solid media. Two types of human osteoprogenitor cells are observed: a colony-forming cell (CFC) that generates several hundred bone antigen-positive cells, and a more mature cluster-forming cell that has a lesser proliferative potential and thus generates clusters of <em>20</em>-50 antigen-positive cells. Osteopoietic colony-forming cells and cluster-forming cells have an obligate but differential requirement for osteogenic <em>growth</em> <em>factors</em>. The CFCs respond to TGF-beta, basic <em>fibroblast</em> <em>growth</em> <em>factor</em> (bFGF), bone morphogenic protein-2 (BMP-2), and 1, 25-dihydroxy vitamin D3 (1,25-OH D3). In contrast to the colony-forming cells, cluster-forming cells are regulated predominantly by 1,25-OH D3 and TGF-beta, but fail to respond to bFGF. We conclude that human bone marrow contains a nonhematogenous, heterogeneous population of bone precursor cells among which exists a population of proliferating osteoprogenitor cells. Further characterization of these bone precursor cell populations should yield important information on their role in osteogenesis in both health and disease.

<em>Fibroblast</em> <em>growth</em> <em>factors</em> (FGFs) are mitogenic and chemotactic agents for a wide variety of cell types and play a primary role in the regulation of angiogenesis. Angiogenesis is involved in a variety of critical physiological events including organogenesis, wound healing, ischemic collateral circulation, and solid tumor <em>growth</em>. High-resolution structural information is key to understanding the mechanism of action of these <em>growth</em> <em>factors</em>. We report here the X-ray crystal structure of human acidic FGF (aFGF), with data extending to 2.0 angstroms resolution. The crystal contains four independent molecules in the asymmetric unit. Each molecule contains a single bound sulfate ion, in similar juxtapositions. The bound sulfate is stabilized through hydrogen-bond interactions with residues Asn 18, Lys 113, and Lys 118 and defines a potential heparin binding site. The hydrogen bond with the N delta 2 moiety of Asn 18 appears to be the most conserved interaction, being similar to those observed for sulfate ion bound to human basic FGF (bFGF) and similar but not identical to interactions observed for bovine aFGF with heparin analogs. Of the added solvent groups, five ordered water molecules are conserved in each of the four independent structures of human aFGF. These water molecules, located at buried positions, provide hydrogen bonding partnerships with several buried polar groups in the core of the protein. A central interior cavity exists in each of the four structures, with sizes ranging from approximately <em>20</em> to 50 angstroms3. The cavity sizes appear to be significantly smaller than that observed in the related protein interleukin-1 beta. The region comprising the high affinity FGF receptor binding site is structurally very similar to the corresponding region from human bFGF, whereas the low affinity site is structurally quite different. The results provide a structural basis for the role of the low affinity binding site in FGF receptor discrimination.

Fibrosis of lung tissue is a frequent and serious consequence of radiotherapy of mammary carcinoma. The pathogenesis of radiation-induced pulmonary fibrosis remains unclear. Cytokines such as transforming <em>growth</em> <em>factor</em> beta (TGFbeta) and interleukin-4 (IL-4) have been reported to stimulate collagen synthesis in <em>fibroblasts</em> in vitro. The aim of this study was to document the presence of IL-4 during the development of post-irradiation lung fibrosis. Right lungs of male Fischer rats were irradiated with a single dose of <em>20</em> Gy and IL-4 expression in the irradiated lungs was monitored for a period of three months. IL-4 gene transcription as determined by ribonuclease protection assay (RPA) as well as IL-4 synthesis as shown by Western blotting increased in the irradiated lungs reaching a plateau concentration within 3 weeks after irradiation. Enhanced IL-4 production was still detected at day 84 after irradiation. The cellular origin of IL-4 was analyzed by in situ hybridization and two-color immunofluorescence on lung tissue sections and on cytospin preparations of leukocytes obtained from bronchoalveolar lavages. These experiments revealed a substantial IL-4 production by macrophages during development of post-irradiation lung fibrosis.