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1.
Two experimental models that separated demineralized bone matrix (DBM) implants from the host bone were utilized to identify
the origins of bone-forming cells in the repair of calvarial defects in rats. Rat DBM, Guanadine-HCl (Gdn-HCl) extracted insoluble
residue of DBM, and Gdn-HCl extracted insoluble DBM to which the dialyzed Gdn-HCl extract was added back, were implanted in
the two models which prevented cells of the adjacent host bone from participating in the repair. In addition, cells in the
dura and in the subcutaneous tissue overlying the calvarial defect were locally labeled with 3H-thymidine to identify the origins of those cells that were stimulated to divide and differentiate to osteoblasts. Histological
studies of the temporal events that occurred during the healing process in these defect models, combined with 3H-thymidine labeling demonstrated that the osteoblasts induced by DBM were initially derived from undifferentiated mesenchymal
stem cells of the dura and later augmented by cells in the overlying connective tissue covering the defect, and not from cells
in the cranial bone surrounding the circular defect. The cells of both dura and subcutaneous tissue were stimulated to proliferate
and differentiate principally to osteoblasts and to a very much lesser extent to chondroblasts by DBM and by reconstituted
components of DBM after Gdn-HCl extraction. Gdn-HCl-extracted insoluble DBM failed to induce bone or cartilage. These results
indicate that the cytokines or other factors present in DBM are required to induce bone-forming cells derived from the dura
and the overlying connective tissue for the repair of the calvarial defect.
Received: 1 January 1999 / Accepted: 13 August 1999 相似文献
2.
The cellular and biochemical sequences of osteogenesis induced by implanting demineralized bone matrix (DBM) in rat cranial
defects and in subcutaneous sites have been studied by histological, histochemical, and biochemical techniques from days 2
to 28 after implantation. In subcutaneous sites, allogenic DBM induced cartilage cells and matrix for approximately the first
10 days which were subsequently resorbed and replaced by bone with little evidence for the classical endochondral sequence
of ossification. In sharp contrast, the first cells that differentiated from the mesenchymal stem cells in the cranial defects
were alkaline phosphatase (ALP) positively stained osteoblasts that appeared 3 days after implantation followed by synthesis
of bone matrix which calcified shortly thereafter. A few clusters of cartilage cells were observed beginning at days 6–7 which
were spatially distinct from the new bone and later resorbed. By day 28 the tissue induced in both the subcutaneous and cranial
sites consisted almost solely of bone; however, the total amount of new bone in the subcutaneous implants was significantly
less than the mass of bone formed in the calvarial defects. Bovine DBM induced bone formation in rat cranial defects to a
very much lesser extent than allogenic DBM. A few cartilage cells were induced by bovine DBM in subcutaneous sites and rapidly
resorbed and not replaced with bone. These results clearly indicate that the cellular sequence induced by allogenic and xenogenic
DBM and the repair tissues synthesized are distinctly different in the cranial defects from those induced in the subcutaneous
sites.
Received: 1 September 1998 / Accepted: 15 January 1999 相似文献
3.
Endochondral bone formation occurs through a series of developmentally regulated cellular stages, from initial formation
of cartilage tissue to calcified cartilage, resorption, and replacement by bone tissue. Nasal cartilage cells isolated by
enzymatic digestion from rat fetuses were seeded at a final density of 105 cell/cm2 and cultured in Dulbecco's modified Eagle medium (DMEM) supplemented with 10% fetal calf serum in the presence of ascorbic
acid and β-glycerophosphate. First, cells lost their phenotype but in this condition they rapidly reexpressed the chondrocyte
phenotype and were able to form calcified cartilaginous nodules with the morphological appearance of cartilage mineralization
that occurs in vivo during endochondral ossification. In this mineralizing chondrocyte culture system, we investigated, between day 3 and day
15, the pattern expression of types II and X collagen, proteoglycan core protein, characteristic markers of chondrocyte differentiation,
as well as alkaline phosphatase and osteocalcin associated with the mineralization process. Analysis of labeled collagen and
immunoblotting revealed type I collagen synthesis associated with the loss of chondrocyte phenotype at the beginning of the
culture. However, our culture conditions promoted extracellular matrix mineralization and cell differentiation towards the
hypertrophic phenotype. This differentiation process was characterized by the induction of type X collagen mRNA, alkaline
phosphatase, and diminished expression of type II collagen and core protein of large proteoglycan after an increase in their
mRNA levels before the mineralizing process. These results revealed distinct switches of the specific molecular markers and
indicated a similar temporal expression to that observed in vivo recapitulating all stages of the differentiation program in vitro.
Received: 12 December 1996 / Accepted: 26 June 1997 相似文献
4.
We have used a rabbit leg-lengthening model for detailed studies of the histology of distraction osteogenesis. Some unusual
features of the endochondral ossification that occurs during the rapid transition of cartilage to bone in the regenerate were
observed. Histological staining techniques together with immunohistochemistry and nonradioactive in situ mRNA hybridization for cartilage and bone-related molecules have been used to document the presence of an overlapping cartilage-bone
phenotype in cells of the cartilage-bone transitional region. In those particular areas, some chondrocytes appeared to be
directly transformed into newly formed bone trabeculae which are surrounded by bone matrix. Acid phosphatases were found within
the cartilage matrix in some of the cartilage/bone transitional regions and type I collagen mRNA and type II collagen protein
were found together in some of the marginal hypertrophic chondrocytes. This study indicates an unusual role of chondrocytes
in the process of ossification at a distraction rate of 1.3 mm/day in the rabbit. Further direct evidence is required to prove
the hypothesis that the hypertrophic chondrocytes may transdifferentiate into bone cells in this model.
Received: 13 March 1997 / Accepted: 22 September 1998 相似文献
5.
D. Chen M. A. Harris G. Rossini C. R. Dunstan S. L. Dallas J. Q. Feng G. R. Mundy S. E. Harris 《Calcified tissue international》1997,60(3):283-290
Normal bone formation is a prolonged process that is carefully regulated and involves sequential expression of growth regulatory
factors by osteoblasts as they proliferate and ultimately differentiate. Since this orderly sequence of gene expression by
osteoblasts suggests a cascade effect, and BMP-2 is capable of initiating and maintaining this effect, we examined the effects
of BMP-2 on expression of other BMPs and compared these effects with the expression pattern of bone cell differentiation marker
genes in primary cultures of fetal rat calvarial (FRC) osteoblasts. To examine the gene expression profile during bone cell
differentiation and bone formation, we also examined the effects of rBMP-2 on bone formation in vivo and in vitro. rBMP-2 stimulated bone formation on the periosteal surface of mice when 500 ng/day rBMP-2 was injected subcutaneously. When
rBMP-2 was added to primary cultures of FRC osteoblasts, it accelerated mineralized nodule formation in a time and concentration-dependent
manner (10–40 ng/ml). rBMP-2 (40 ng/ml) enhanced BMP-3 and -4 mRNA expression during the mineralization phase of primary cultures
of FRC osteoblasts. Enhancement of BMP-3 and -4 mRNA expression by rBMP-2 was associated with increased expression of bone
cell differentiation marker genes, alkaline phosphatase (ALP), type I collagen, osteocalcin (OC), osteopontin (OP), and bone
sialoprotein (BSP). These results suggest that BMP-2 enhances expression of other BMP genes during bone cell differentiation.
BMP-2 may act in a paracrine fashion in concert with other BMPs it induces to stimulate bone cell differentiation and bone
formation during remodeling.
Received: 27 November 1995 / Accepted: 19 July 1996 相似文献
6.
The effects of mechanical loading on the osteoblast phenotype remain unclear because of many variables inherent to the current
experimental models. This study reports on utilization of a mouse tooth movement model and a semiquantitative video image
analysis of in situ hybridization to determine the effect of mechanical loading on cell-specific expression of type I collagen (collagen I) and
alkaline phosphatase (ALP) genes in periodontal osteoblasts, using nonosseous cells as an internal standard. The histomorphometric
analysis showed intense osteoid deposition after 3 days of treatment, confirming the osteoinductive nature of the mechanical
signal. The results of in situ hybridization showed that in control periodontal sites both collagen I and ALP mRNAs were expressed uniformly across the
periodontium. Treatment for 24 hours enhanced the ALP mRNA level about twofold over controls and maintained that level of
stimulation after 6 days. In contrast, collagen I mRNA level was not affected after 24 hours of treatment, but it was stimulated
2.8-fold at day 6. This increase reflected enhanced gene expression in individual osteoblasts, since the increase in osteoblast
number was small. These results indicate that (1) the mouse model and a semiquantitative video image analysis are suitable
for detecting osteoblast-specific gene regulation by mechanical loading; (2) osteogenic mechanical stress induces deposition
of bone matrix primarily by stimulating differentiation of osteoblasts, and, to a lesser extent, by an increase in number
of these cells; (3) ALP is an early marker of mechanically-induced differentiation of osteoblasts. (4) osteogenic mechanical
stimulation in vivo produces a cell-specific 2.8-fold increase in collagen gene expression in mature, matrix-depositing osteoblasts located on
the bone surface and within the osteoid layer.
Received: 9 August 1999 / Accepted: 4 February 2000 相似文献
7.
Chondrocyte Differentiation in Human Osteoarthritis: Expression of Osteocalcin in Normal and Osteoarthritic Cartilage and Bone 总被引:5,自引:0,他引:5
Pullig O Weseloh G Ronneberger D Käkönen S Swoboda B 《Calcified tissue international》2000,67(3):230-240
Osteocalcin (OC), which is a marker of the mature osteoblasts, can also be found in posthypertrophic chondrocytes of the
epiphyseal growth plate, but not in chondrocytes of the resting zone or in adult cartilage. In human osteoarthritis (OA),
chondrocytes can differentiate to a hypertrophic phenotype characterized by type X collagen. The protein- and mRNA-expression
pattern of OC was systematically analyzed in decalcified cartilage and bone sections and nondecalcified cartilage sections
of human osteoarthritic knee joints with different stages of OA to investigate the differentiation of chondrocytes in OA.
In severe OA, we found an enhanced expression of the OC mRNA in the subchondral bone plate, demonstrating an increased osteoblast
activity. Interestingly, the OC protein and OC mRNA were also detected in osteoarthritic chondrocytes, whereas in chondrocytes
of normal adult cartilage, both the protein staining and the specific mRNA signal were negative. The OC mRNA signal increased
with the severity of OA and chondrocytes from the deep cartilage layer, and proliferating chondrocytes from clusters showed
the strongest signal for OC mRNA. In this late stage of OA, chondrocytes also stained for alkaline phosphatase and type X
collagen. Our results clearly show that the expression of OC in chondrocytes correlates with chondrocyte hypertrophy in OA.
Although the factors including this phenotypic shift in OA are still unknown, it can be assumed that the altered microenvironment
around osteoarthritic chondrocytes and systemic mediators could be potential inducers of this differentiation.
Received: 20 May 1999 / Accepted: 10 February 2000 相似文献
8.
Osteoblast cells, recruited from mesenchymal precursors, initiate the final phase of bone remodeling by secreting the protein
components of the bone matrix. Upon completion of remodeling, some of these osteoblasts may further differentiate, giving
rise to matrix-embedded osteocytes and bone lining cells. The fate of the remaining osteoblasts is unknown, although by analogy
with other cell systems, apoptotic cell death may be involved. We induced and characterized the apoptotic process in ROS 17/2.8
osteosarcoma cells by growing and maintaining confluent cultures in low serum medium. At confluence, but prior to apoptosis,
the levels of collagen type I, alkaline phosphatase, and osteocalcin mRNAs declined abruptly. Expression of two housekeeping
genes (ribosomal protein RPS6 and GAPDH) remained unchanged. Some 72 hours later cells began to show morphological and biochemical
features of apoptosis, namely, chromatin condensation, membrane budding, and internucleosomal degradation of genomic DNA.
We conclude that serum starvation-induced apoptosis of ROS 17/2.8 cells can serve as a model for investigating the mechanisms
of osteoblastic apoptosis.
Received: 20 November 1996 / Accepted: 8 January 1998 相似文献
9.
Mineralization and alkaline phosphatase activity in collagen lattices populated by human osteoblasts 总被引:4,自引:0,他引:4
Rattner A Sabido O Le J Vico L Massoubre C Frey J Chamson A 《Calcified tissue international》2000,66(1):35-42
Adult human osteoblastic cells were grown in a native type I collagen gel. Proliferation and viability analyses showed that
cells rapidly stopped dividing and became blocked in the G0G1 phase (91% on day 13). Carboxyfluorescein diacetate cell staining
and flow cytometry showed that osteoblasts were viable for the first 16 days and then viability decreased (58% viable cells
on day 22). Osteoblasts were able to retract the matrix. Betaglycerophosphate (βGP) stimulated the deposition of mineral particles
in the collagen network, and electron probe microanalysis showed that they were principally calcium and phosphorus, with a
Ca/P ratio of about 1.7. Various times of βGP supply were tested. We compared 10 mM βGP added only once at day 0, or continuously
from day 0, day 8, or day 21. Mineralization was observed in conditions where βGP was added at day 0. Furthermore, 10 mM βGP
added once during gel preparation was sufficient to induce mineralization with mineral accumulation up to day 15 whereas the
speed of the gel contraction decreased. In every condition, cultures expressed high alkaline phosphatase (ALP) levels as early
as day 3, which decreased afterwards. These kinetics might explain why the other conditions did not prove favorable to the
mineralization process. The model was used to study the influence of blocking gel retraction. Blocking retraction delayed
the ALP activity decrease, but had no effect on mineralization. In conclusion, human adult osteoblasts cultured in native
collagen gel stopped proliferation and underwent mineralization very early. This model should be used to investigate the influence
of effectors on the early stages of culture.
Received: 15 October 1997 / Accepted: 1 July 1999 相似文献
10.
目的为验证三维打印研究中动物模型的可靠性,采用骨髓基质干细胞(Bone marrow mesenchymal stem cells,BMSCs)修复裸鼠颅骨缺损。方法共10只裸鼠,其中实验组(n=5只):颅骨缺损区植入BMSCs/脱钙骨;材料对照组:颅骨缺损区植入单纯脱钙骨,采用实验组自身对照(n=5只);空白对照组(n=5只):双侧颅骨区造成缺损后旷置。术后3个月取材进行大体观察、组织学和免疫组化(骨钙蛋白)检查。结果术后3个月,实验侧组织质地较硬,组织学表现为骨结构,骨钙蛋白免疫组化阳性;对照侧质地较软,组织学表现为结缔组织,骨钙蛋白免疫组化阴性;空白对照组仍表现为颅骨缺损。结论采用BMSCs可修复裸鼠颅骨缺损,验证了三维打印研究中动物模型的可靠性。 相似文献
11.
C. Cepollaro S. Gonnelli C. Pondrelli A. Montagnani S. Martini D. Bruni C. Gennari 《Calcified tissue international》1999,65(2):129-132
We studied 21 patients (11 men and 10 women) with osteogenesis imperfecta (OI) and 21 age- and sex-matched controls. In all
patients we measured serum levels of total alkaline phosphatase (ALP), type I procollagen carboxy-terminal propeptide (PICP),
osteocalcin (BGP), urinary excretion of hydroxyproline (HOP/Cr), and pyridinoline crosslinks (Pyr/Cr). Bone mineral density
was measured at the distal radius (BMD-R) and at the lumbar spine (BMD-LS) by dual X-ray absorptiometry (DXA). Ultrasound
parameters were also performed at the calcaneous with the Achilles device and at the phalanxes with DBM Sonic 1200. A significant
reduction (P < 0.001) in BMD and in ultrasound parameters was found in OI patients compared with normals. PICP was significantly reduced
in the OI patients compared with controls (P < 0.001); other markers of bone turnover were higher in OI than in controls, but the difference did not reach the statistical
significance. A significant correlation (P < 0.05) was found between PICP and BMD at the lumbar spine and between PICP and ultrasound parameters at the calcaneous.
On the basis of our data, we conclude that patients with OI show low values of BMD and ultrasound parameters; therefore in
these patients, not only is bone mass disturbed but also bone quality. The reduced levels of PICP in OI patients confirm that
most OI patients have defects in collagen I biosynthesis. These defects may contribute to the fragility of OI bone by interfering
with complete mineralization and/or normal tissue structure. PICP may be considered a useful marker in the clinical management
of OI.
Received: 26 March 1998 / Accepted: 15 January 1999 相似文献
12.
The cellular localization and roles of bone morphogenetic protein (BMP)-2 and apoptosis-associating factors in human orofacial
development remain unclear. In this study, BMP-2, osteocalcin, and TGF-β, which are bone-differentiating markers, apoptosis-associating
factors (i.e., Bcl-2, Bax, Fas, and Fas ligand), apoptotic cells detected by the in situ 3′-end labeling method (TUNEL), and proliferating cell nuclear antigen (PCNA) were immunohistochemically examined in the
heads (in particular, the jaw bone and tooth germs) of human fetuses of 11-week pregnancy. BMP-2 was positive in osteoblasts
and newly formed osteoid of the incisive and palatal bone of the maxilla and the mandible, which indicated that BMP-2 was
exclusively involved in intramembranous ossification in the human fetal head. Fas was positive in the cytoplasm of osteocytes
and a few osteoblasts. In contrast, Fas ligand was positive in the cytoplasm of osteoblasts and abundant in the stroma of
the osteoblastic layer, periosteum, and perichondrium. The Fas ligand in the stroma was recognized as the soluble form, which
was possibly produced by osteoblasts. TUNEL-positive apoptotic cells were found in a few osteocytes and a few osteoblastic
cells in new bone, and in monocytes of degenerate Meckel's cartilage. The induction of apoptosis observed in monocytes seems
to be caused via a Fas-Fas ligand cell death system, because some of these monocytes were Fas-positive, and most of them were
Fas ligand-positive. Interestingly, the abundant soluble Fas ligand observed in the periosteum probably protects the bone-formative
zone from the invasion of the activated lymphocytes by binding to Fas expressing in these lymphocytes and killing these cells.
Fas and Fas ligand were focally positive in the dental lamina and inner enamel epithelium and cusps of the enamel organ, nevertheless,
the presence of TUNEL-positive cells was very rare. Bcl-2 was clearly and Bax was weakly positive in the cells throughout
the dental lamina and enamel organ. These findings indicated that Fas-mediated apoptosis was inhibited by the Bcl-2 family
in the development of teeth.
Received: 22 January 1998 / Accepted: 2 December 1999 相似文献
13.
U. Prabhakar I. E. James R. A. Dodds E. Lee-Rykaczewski D. J. Rieman D. Lipshutz S. Trulli Z. Jonak K. B. Tan F. H. Drake M. Gowen 《Calcified tissue international》1998,63(3):214-220
A novel, immortalized, human bone marrow stroma-derived cell line TF274 is described which has the ability to form bone both
in vitro and in vivo. Under basal conditions these cells expressed alkaline phosphatase (ALP) and type I collagen genes which are characteristic
of the osteoblast phenotype. ALP levels were upregulated in the presence of osteotropic agents such as parathyroid hormone
(PTH), transforming growth factor beta (TGF-β), and BMP-2. In addition, PTH also increased cAMP levels in these cells. The
capacity of these cells to form bone in vitro was evaluated by culturing them in the presence of L-ascorbic acid and β-glycerophosphate. Matrix mineralization in these
cultures was assessed by Alizarin Red staining and increased 45Ca uptake. Under these conditions mineralized nodule formation was observed in less than 2 weeks. Northern analysis of TF274
cells at various times during the mineralization process indicated a temporal expression of the osteocalcin gene that is typically
associated with differentiating osteoblasts. The osteogenic nature of TF274 cells was confirmed in vivo using the severe combined immunodeficient (SCID) mouse model. Antibodies to human leukocyte antigens (HLA), class I antigens,
and human OKa blood group antigen were used to demonstrate that the lesions formed were of human origin. By 21 days, the lesion consisted
of a homogeneous focus of ALP-positive cells containing areas of mineralized bone lined with tartarate-resistant acid phosphatase
(TRAP) positive osteoclasts. Thus, the TF274 cells exhibit osteogenic potential both in vitro and in vivo. This immortalized cell line represents a consistent source of cells that can be used to study human osteoblast differentiation
both in vitro and in vivo.
Received: 30 July 1997 / Accepted: 23 January 1998 相似文献
14.
In this study, we demonstrated that type I collagen matrix induced the expression of osteoblastic phenotypes of bone marrow
cells, and that antibone sialoprotein (BSP) monoclonal antibody suppressed the expression of these phenotypes. On the other
hand, BSP accelerated the expression of osteoblastic phenotypes of bone marrow cells. The adherent bone marrow cells were
harvested from rat femur and cultured on type I collagen matrix gels in medium containing 15% fetal calf serum, neither β-glycerophosphate
nor glucocorticoid. Cells showed osteoblastic phenotypes (high alkaline phosphatase activity, osteocalcin synthesis, and responsiveness
against parathyroid hormone) on collagen matrix gels at week 3 after the inoculation, and simultaneously, BSP was detected
in the conditioned medium by Western blotting using an anti-BSP monoclonal antibody. However, cells in the conventional culture
dishes did not show osteoblastic phenotypes during the experimental period. To investigate the physiological function of BSP
in osteoblastic differentiation, bone marrow cells were cultured on collagen matrix with an anti-BSP monoclonal antibody for
3 weeks. This treatment suppressed the expression of the osteoblastic phenotypes, and the effect of the antibody was abolished
by the addition of bovine bone BSP. Furthermore, bovine bone BSP stimulated the expression of osteoblastic phenotypes of bone
marrow cells. Our results indicate that BSP plays a crucial role in the expression of osteoblastic phenotypes of bone marrow
cells.
Received: 17 February 1999 / Accepted: 14 December 1999 相似文献
15.
The steroid sex hormones exert major effects on bone formation although the molecular events associated with their activity
remain unclear. We have investigated the effects of ovariectomy and dihydrotestosterone (DHT) administration to both sham-operated
and ovariectomized (ovx) rats on the bone mRNA levels of osteoblast genes. Rats were randomly allocated to either sham or
ovariectomy operations and were administered either vehicle or 40 mg/kg body weight DHT by silastic tube implants at the time
of operation for 8 weeks, at which time they were killed and total RNA was extracted from the long bones. Northern blot analysis
indicated that the mRNA levels of the bone cell genes α1(I) collagen, alkaline phosphatase, osteocalcin, and osteopontin were
markedly increased in ovx rats between 6- and 30-fold. DHT administration to ovary-intact, estrogen-sufficient rats increased
the mRNA levels of α1(I) collagen, alkaline phosphatase, osteopontin, and osteocalcin between 3- and 9-fold. In contrast,
DHT did not alter levels of these mRNA species in ovx rats. The data demonstrate that estrogen deficiency increased mRNA levels
of genes expressed during osteoblast development and suggest an interplay between estrogen and androgen action in regulating
the expression of a number of bone cell genes.
Received: 20 May 1999 / Accepted: 21 January 2000 相似文献
16.
Gene Expression of Noncollagenous Bone Matrix Proteins in the Limb Joints and Intervertebral Disks of the twy Mouse 总被引:3,自引:0,他引:3
T. Ohtsuki S. Furuya T. Yamada S. Nomura J.-i. Hata Y. Yabe Y. Hosoda 《Calcified tissue international》1998,63(2):167-172
The twy (tiptoe walking Yoshimura) mouse is an autosomal recessive mutant manifesting multiple osteochondral lesions characterized
by pathologic calcium deposition. To elucidate the pathophysiology of the limb joint lesions and the intervertebral disk lesions
of the twy mouse, we assessed the mRNA expression of noncollagenous bone matrix proteins such as osteocalcin, osteonectin,
osteopontin, and matrix Gla protein (MGP) by in situ hybridization, but only expression of MGP was observed in association with the pathologic calcium deposits in twy mice. Mild
degeneration and abnormal growth of the cartilage in contact with the joint capsule was observed at 5 weeks in the articular
cartilage of the ankle joint of the twy mouse, and MGP gene expression was observed at the same time. Simultaneous growth
of synovial membrane cells and relatively undifferentiated articular cartilage cells in the knee joint, and of cartilage-like
cells near the insertion of the cruciate ligament was observed in the twy mouse, and MGP gene expression was found to be present
at the same time. Hypertrophy of abnormally proliferated chondrocyte-like cells, which are different from fibrocartilaginous
cells of the annulus fibrosus, was observed in the intervertebral disks of the twy mouse at 3 weeks of age, and MGP gene expression
was noted at the same time. These findings suggest that abnormal expression of MGP plays a major role in the pathologic calcification
of the twy mouse.
Received: 14 May 1997 / Accepted: 24 December 1997 相似文献
17.
In situ localization of collagen production by chondrocytes and osteoblasts in fracture callus 总被引:9,自引:0,他引:9
M Sandberg H Aro P Multim?ki H Aho E Vuorio 《The Journal of bone and joint surgery. American volume》1989,71(1):69-77
An experimental model of fracture-healing was used to study the production of types-I and II collagen by in situ hybridization. The distribution of cartilage matrix in callus was determined by histochemical staining. Messenger RNA (mRNA) for cartilage-specific type-II collagen was detectable as early as the fifth day in a small number of cells that had acquired a chondrocyte phenotype but that also contained type-I collagen mRNA, suggesting an ongoing change in the expression of collagen genes. The location of the first chondrocytes, which were adjacent to cortical bone, suggested that they originated from cells that had derived from the periosteum by differentiation. On the seventh day of callus formation, the presence of both type-I and type-II collagen mRNA in chondrocytes of expanding cartilage suggested that most growth occurred by differentiation of mesenchymal cells and less by proliferation of differentiated chondrocytes. Expansion continued until the tenth to fourteenth day, after which the cartilage was replaced by woven bone. This was characterized by the presence of osteoblasts that were active in the synthesis of type-I collagen. 相似文献
18.
19.
Mesenchymal stem cells (MSCs) provide an important source of pluripotent cells for musculoskeletal tissue repair. This study examined the impact of MSC implantation on cartilage healing characteristics in a large animal model. Twelve full-thickness 15-mm cartilage lesions in the femoropatellar articulations of six young mature horses were repaired by injection of a self-polymerizing autogenous fibrin vehicle containing mesenchymal stem cells, or autogenous fibrin alone in control joints. Arthroscopic second look and defect biopsy was obtained at 30 days, and all animals were euthanized 8 months after repair. Cartilage repair tissue and surrounding cartilage were assessed by histology, histochemistry, collagen type I and type II immunohistochemistry, collagen type II in situ hybridization, and matrix biochemical assays. Arthroscopic scores for MSC-implanted defects were significantly improved at the 30-day arthroscopic assessment. Biopsy showed MSC-implanted defects contained increased fibrous tissue with several defects containing predominantly type II collagen. Long-term assessment revealed repair tissue filled grafted and control lesions at 8 months, with no significant difference between stem cell-treated and control defects. Collagen type II and proteoglycan content in MSC-implanted and control defects were similar. Mesenchymal stem cell grafts improved the early healing response, but did not significantly enhance the long-term histologic appearance or biochemical composition of full-thickness cartilage lesions. 相似文献
20.
E. A. Cowles M. E. DeRome G. Pastizzo L. L. Brailey G. A. Gronowicz 《Calcified tissue international》1998,62(1):74-82
The in vivo expression of fibronectin, type I collagen, and several non-collagenous proteins was correlated with the development of bone
in fetal and early neonatal rat calvariae. Fibronectin was the earliest matrix protein expressed in calvariae, with a peak
expression in fetal 16- and 17-day (d) bones. Fibronectin expression coincided with the condensation of preosteoblasts prior
to calcification and decreased once bone mineralization commenced. The expression of type I collagen, osteonectin, bone sialoprotein,
and alkaline phosphatase mRNAs was found at 17 d. The increase in type I collagen mRNA levels was correlated with a 3.5-fold
increase in calcium deposition at 19–20 d. Bone sialoprotein and alkaline phosphatase peaked on fetal 21 d while osteonectin
remained at a low level and was localized to the osteoblast layer and the osteocyte lacunae. Osteopontin mRNA levels increased
rapidly in neonatal calvariae. After birth, osteonectin and fibronectin were mainly associated with blood vessels. Thus, fibronectin
is one of the earliest matrix proteins expressed in calvariae and is rapidly followed by type I collagen, bone sialoprotein,
and alkaline phosphatase. Osteocalcin, osteonectin, and osteopontin mRNAs have similar patterns of expression in the developing
fetal calvaria, and their synthesis coincided with mineralization.
Received: 31 December 1996 / Accepted: 5 June 1997 相似文献