Emperipolesis of marrow cells within megakaryocytes in the bone marrow of sublethally irradiated mice

The incidence of megakaryocytic emperipolesis was studied in the bone marrow of normal and X-irradiated mice. Two groups of mice received total body irradiation with a single dose of 5 Gy and one of the two groups had been treated with a radioprotective drug, ethiofos (WR-2721), before irradiation. Mice from a third group remained unexposed to irradiation and served as controls. The Wright-Giemsa stained bone marrow smears were analyzed every 5 days during a 30-day period, starting 1 day after irradiation. The number of megakaryocytes exhibiting the phenomenon was determined and expressed as an average value for every experimental group. The frequency of megakaryocytic emperipolesis was less than 15% of megakaryocytes from control smears but increased to 34% in mice that had only been irradiated and to 43% when mice were treated with WR-2721 before irradiation. In the last case, i.e., irradiation and treatment with a radioprotective drug, a positive correlation between the macrocytic megakaryocytes and elevated emperipolesis was noted. Under light microscopy, there were no signs of phagocytosis; engulfed cells remained unaltered with their normal structure intact. Granulocytic, erythroid, and lymphoid cells appeared to be the most frequent marrow cells engulfed by mature megakaryocytes. The number of incorporated cells in one megakaryocyte ranged from 1 to 3, though occasionally more than 6 were seen in macrocytic megakaryocytes. Based on our findings and on a review of the associated literature, we believe emperipolesis is an interesting cellular phenomenon related to the fast passage of marrow cells across the marrow-blood barrier, especially through the cytoplasm of megakaryocytes in response to an increased demand for cell delivery. The high demand for cell delivery which occurs after irradiation may cause certain mature bone marrow cells to take a transmegakaryocyte path to enter the circulation of the blood. Irradiation seems to have an immediate effect (observed after 24 h) on emperipolesis, suggesting that a humoral factor is involved in the pathogenesis.     

Oxidative study of patients with total body irradiation: effects of amifostine treatment

In patients undergoing bone marrow transplant (BMT), reactive oxygen species (ROS) are released as a consequence of the events related to the preparative regimen. Total body irradiation (TBI), which is known to generate ROS, is a routine preconditioning procedure prior to BMT. Several studies have demonstrated that amifostine protects normal tissues. In the present report, we investigated the oxidative state of plasma and erythrocytes in 21 patients with hematological malignancies undergoing TBI. The dose fraction was 160 cGy, twice daily (eight sessions). For ROS detection, we used electron spin resonance spectroscopy and spin-trapping technique. In all, 15 patients received amifostine prior to the irradiation and six did not. No free radical signal was detected in the plasma samples spectrum of 15 amifostine-treated patients, and five of six samples of nontreated patients showed ROS signal. Only two of 15 treated patients had mucositis degree higher than 2, whereas five of six nontreated patients suffered this complication. The average hospitalization days in treated and nontreated patients were 23.5 and 29.7, respectively. This work represents an original observation; we found by direct measurements of free radicals that ROS are released during TBI, and confirmed the amifostine radical scavenger activity.     

Variation of PDGF,TGFbeta, and bFGF levels in essential thrombocythemia patients treated with anagrelide

We studied 15 patients with essential thrombocythemia (ET) before treatment and after normalization of platelet count by anagrelide. Significantly increased plasma levels of PDGF, TGFbeta, and bFGF were found. Patients with mild reticulin fibrosis in bone marrow had higher PDGF levels. During treatment, plasma TGFbeta and bFGF levels remained elevated in most patients (P < 0.0001 and P < 0.01, respectively). Intraplatelet PDGF levels were low before treatment (P < 0.006) and normal on hematological remission, without relation with the presence or absence of reticulin fibrosis in bone marrow. Intraplatelet TGFbeta levels were normal regardless of the platelet count. Intraplatelet bFGF levels were raised before (P < 0.001) and during treatment (P < 0.01). By immunostaining, TGFbeta and bFGF were seen in megakaryocytes and lymphocytes with a similar pattern of intensity in patients and controls, suggesting that other cells might also contribute to the raised plasma values. We believe that the plasma increment of these cytokines suggests that they play a role in the pathogenesis of ET. The normal PDGF plasma level found during treatment may be in relation with the platelet count. However, the persistent increase of TGF-beta in plasma and bFGF both in plasma and platelets may indicate dysregulation of cytokine synthesis in TE.     

反义Smad3阻断TGF-β1信号转导对大鼠BMSC分化成平滑肌样细胞的影响

目的研究信号蛋白Smad3在TGF-β1促大鼠骨髓间充质干细胞分化成平滑肌样细胞中的作用。方法运用免疫细胞化学、RT—PCR证实BMSC中存在TGF-β1／smad3信号传导通路的基础上,运用反义Smad3进行干预。实验分三组：反义Smad3组（反义Smad3腺病毒转染大鼠BMSC）,空载对照组（空载腺病毒转染大鼠BMSC）及未转染组;一组均予10ng／mL浓度的TGF-β1诱导1W。通过免疫细胞化学和实时定量PCR比较反义Smad3干预后各组SMut=actin的表达变化。结果经免疫细胞化学法、RT-PCR检测证明BMSC中存在TGF-β1／smad3表达。运用针对靶基因Smad3的反义技术干预后,经10ng／mLTGF-β1诱导,相比未转染组及空载组,反义smad3腺病毒转染组SMα-actin阳性细胞表达数明显减少。实时定量PCR也显示反义smad3组SMα-actinmRNA的相对含量明显低于未转染组（O．460±0．259VS2．932±0．375,P〈0．01）,而空载组与未转染组相比无明显统计学差异。结论TGF-β1促BMSC成平滑肌样细胞分化的过程中受Smad3选择性调节,Smad3可能是TGF-β1促BMSC分化成平滑肌样细胞的细胞内信号途径。     

Increases in circulating megakaryocyte growth-promoting activity in the plasma of rats following whole body irradiation

To gain insight into the regulation of megakaryocyte precursors in vivo, we assayed (in vitro) megakaryocyte growth-promoting activity (Meg-GPA) in plasma of rats in which both marrow hypoplasia and thrombocytopenia had been induced by irradiation. Rats received whole body irradiation of 834 rad from a 137Cs source. Plasma was collected at intervals of hours to days, up through day 21 postirradiation, and was tested, at a concentration of 30%, for Meg-GPA on bone marrow cells cultured in 1.1% methylcellulose with 5 X 10(-5) M 2-mercaptoethanol. With normal rat plasma, no megakaryocyte colonies (defined as greater than or equal to 4 megakaryocytes) were seen and only a few single megakaryocytes and clusters (defined as 2 or 3 megakaryocytes) were formed. Two peaks of plasma Meg-GPA were observed after irradiation. The first appeared at 12 hr, before any decrease in marrow megakaryocyte concentration or platelet count. The second occurred on days 10-14 after irradiation, after the nadir in megakaryocyte concentration and while platelet counts were at their lowest levels. A dose-response study of plasma concentration and megakaryocyte growth, using plasma collected 11 days postirradiation, demonstrated that patterns of megakaryocyte growth were related to plasma concentration; formation of single megakaryocytes was optimal over a range of 20%-30% plasma concentration, while cluster and colony formation were optimal at a plasma concentration of 30%. All forms of megakaryocyte growth were decreased with 40% plasma. There was a linear relationship between the number of bone marrow cells plated and growth of single cells, clusters, and colonies using a concentration of 30% plasma collected 11 days after irradiation. We conclude that irradiation causes time- related increases in circulating megakaryocyte growth-promoting activity. We suggest that the irradiated rat is a good model for studying the relationships between Meg-GPA and megakaryocyte and platelet concentration in vivo.     

Regulation of megakaryocyte colony forming cell numbers and ploidy by dideoxynucleosides in immunodeficient mice

We have recently demonstrated that azidothymidine (AZT) elevates the levels of circulating platelets in mice made immune deficient by infection with LP-BM5 murine leukemia virus (MAIDS mice). In an attempt to elucidate the mechanisms of the AZT platelet elevating effect, we examined the number of splenic and bone marrow megakaryocyte colony-forming cells (CFU-mk) and the ploidy of megakaryocytes derived from CFU-mk using fluorescence cytophotometric methods. Two other dideoxynucleosides (ddN) 2′3′-dideoxyinosine (ddL) and 2′3′-dideoxycytidine (ddC) were assessed to determine the specificity of the effect of AZT. MAIDS mice were given ddN in drinking water for 15 days. AZT was the only ddN that significantly increased circulating platelet levels in MAIDS mice. AZT significantly increased splenic CFU-mk in MAIDS mice, but bone marrow CFU-mk were not affected. ddL and ddC failed to change either platelet levels or the numbers of splenic or bone marrow CFU-mk. The ploidy of megakaryocytes derived from splenic and bone marrow CFU-mk were examined by first identifying CFU-mk by staining for acetylcholinesterase, followed by nuclear staining with propidium iodide. The fluorescence of individual cells was then measured using a Perceptics image analysis system. Modal ploidy of CFU-mk megakaryocytes derived from spleen cells of AZT-treated immunodeficient mice was shifted upwards from 16N to 32N. Similarly, AZT treatment changed the modal ploidy number of colony megakaryocytes derived from bone marrows of immunodeficient mice from 16N to 32N. The ploidy distribution was also significantly shifted. ddL and ddC failed to significantly alter either modal ploidy number or distribution of megakaryocytes derived from splenic or bone marrow CFU-mk. These findings suggest that AZT may affect physiological processes that lead to platelet formation. © 1993 Wiley-Liss, Inc.     

Involvement of alphavbeta5 integrin-mediated activation of latent transforming growth factor beta1 in autocrine transforming growth factor beta signaling in systemic sclerosis fibroblasts

OBJECTIVE: To confirm the involvement of alphavbeta5 in the self-activation system in systemic sclerosis (SSc) fibroblasts. METHODS: Levels of alphavbeta5 expression were analyzed by immunoprecipitation. The promoter activity of the human alpha2(I) collagen gene was determined by transient transfection assay. Phosphorylation levels and DNA binding ability of Smad3 were investigated by immunoprecipitation and DNA affinity precipitation, respectively. The localization of active transforming growth factor beta (TGFbeta) was determined by coculture assay using TMLC cells (mink lung epithelial reporter cells that stably express a portion of the plasminogen activator inhibitor 1 promoter). The morphologic features of cells were determined by immunofluorescence analysis. RESULTS: Levels of alphavbeta5 expression were significantly elevated in SSc fibroblasts compared with normal fibroblasts. Treatment with anti-alphavbeta5 antibody or beta5 antisense oligonucleotide significantly reduced human alpha2(I) collagen gene promoter activity in SSc fibroblasts. In SSc fibroblasts pretreated with TGFbeta1 antisense oligonucleotide, the exogenous latent TGFbeta1 stimulation significantly increased human alpha2(I) collagen gene promoter activity; this effect was significantly reduced in the presence of anti-alphavbeta5 antibody. Phosphorylation levels and DNA binding ability of Smad3 in SSc fibroblasts were significantly reduced by treatment with beta5 antisense oligonucleotide. The luciferase activity of TMLC cells cocultured with SSc fibroblasts was significantly elevated compared with that of TMLC cells cocultured with normal fibroblasts and was significantly reduced in the presence of anti-alphavbeta5 antibody. Anti-alphavbeta5 antibody reversed the myofibroblastic features of SSc fibroblasts. CONCLUSION: Up-regulated expression of alphavbeta5 contributes to the establishment of autocrine TGFbeta signaling in SSc fibroblasts through activation of endogenous latent TGFbeta1.     

马洛替酯对肝纤维化大鼠肝组织Smads蛋白表达的影响*

目的 观察马洛替酯对二甲基亚硝胺（DMN）诱导的肝纤维化大鼠肝组织Smads信号通路中关键信号传导分子Smad3、smad4和Smad7蛋白表达的影响,探讨其抗肝纤维化的作用机制。方法 将60只SD大鼠随机分成对照组、模型组、秋水仙碱组和马洛替酯组各15只。在造模的同时给药灌胃。6 w后,取肝组织,进行病理学观察;采用实时荧光定量PCR法和Western Blot 法检测 Smad3、smad4、Smad7 mRNA和蛋白表达。结果 对照组大鼠肝组织Smad3、smad4 mRNA和蛋白表达分别为（0.38±0.09）、（0.29±0.08）和（0.16±0.05）、（0.16±0.07）,显著低于模型组[分别为（0.84±0.08）、（0.76±0.11）和（1.01±0.12）、（0.94±0.11）,P＜0.05];对照组肝组织Smad7 mRNA和蛋白分别为（0.73±0.14）和（0.44±0.15）,模型组Smad7 mRNA和蛋白[（0.22±0.08）和（0.17±0.08）,P＜0.05]表达明显减弱;与模型组比较,马洛替酯组肝组织smad3、smad4 mRNA和蛋白表达分别为[（0.52±0.10）、（0.40±0.10）和（0.51±0.08）、（0.41±0.09）,P＜0.05）],马洛替酯组肝组织Smad7 mRNA和蛋白分别为（0.48±0.09）和（0.39±0.10）,表达有所升高 （P＜0.05）。结论 马洛替酯可明显抑制DMN诱导的大鼠肝脏损伤,改善肝纤维化程度,其作用机制可能与下调Smad3和smad4表达,上调Smad7表达有关。     

培哚普利和缬沙坦对肝纤维化大鼠TGF β1及其Ⅱ型受体mRNA与Smad3、7表达的影响

目的观察培哚普利和缬沙坦抗大鼠肝纤维化的疗效和对转化生长因子β1(TGFβ1)及其Ⅱ型受体(TGFβ1RⅡ)mRNA与Smad3、smad17的影响。方法大鼠随机分为止常对照组，模型组、培哚普利治疗组和缬沙坦治疗组。四氯化碳皮下注射诱导大鼠肝纤维化模型，治疗组于造模第4周开始分别予以培哚普利和缬沙坦灌胃。采用RT-PCR检测肝组织TGFβ1与TGFβ1RⅡ mRNA；免疫组织化学技术检测TGFβ1、Smad3及smad7在肝内的表达及定位，检测肝组织病理改变，检测肝组织羟脯氢酸和血清透明质酸。结果与模型组大鼠比较，经培哚普利或缬沙坦治疗大鼠肝内TGFβ1与TGFβ1RⅡ mRNA表达明显下降、以及smad3蛋白表达明显降低，而Smad7的表达增加。TGFβ1与Smad3的免疫阳性反应信号主要位于纤维间隔中的细胞浆，Smad7主要在肝细胞浆表达，上述物质在两种药物组之间表达差异无显著性。培哚普利或缬沙坦治疗后肝组织羟脯氨酸及血清透明质酸含量较模型组显著降低；肝小叶结构均趋于正常，纤维间隔明显变溥。结论培哚普利或缬沙坦均能有效地减轻肝纤维化大鼠的肝脏损伤及纤维化程度，其机制可能与直接或间接抑制肝内TGFβ1与TGFβ1RⅡ mRNA及Smad3表达，并促进Smad7表达有关。     

Changes in Megakaryocyte Development Following Thrombocytopenia

S ummary . Rats were made thrombocytopenic by total-body X-irradiation and changes in megakaryocyte development studied in shielded tibial bone marrow. The platelet count fell from the fourth day after irradiation to reach a minimum value of 19.5% of the initial count 7 days after irradiation. No changes in megakaryocyte development were observed 5 days after irradiation. Megakaryocyte size was increased at day 7, and the increment maintained until day 12. Megakaryocyte numbers were only significantly increased 12 days after irradiation, but differential counts and electron-microscope autoradiographs suggested increased influx at day 9. Changes in the labelling index of megakaryocytes suggested that some cells already present were undergoing one or more extra endoreduplications. No evidence was obtained for an accelerated megakaryocyte maturation rate or for a sudden release of platelets from mature megakaryocytes. Morphological changes, signifying increased synthesis of protein and demarcation membranes were apparent only in young cells 7 days after irradiation but were present in mature cells by day 12, demonstrating that the response to thrombocytopenia is confined to immature cells.     

Hematopoietic reconstitution after lethal irradiation and bone marrow transplantation: effects of different hematopoietic cytokines on the recovery of thymus, spleen and blood cells

Lethally irradiated mice were grafted with syngeneic bone marrow cells or left ungrafted. Mice of each group were injected with different hematopoietic cytokines for 5 consecutive days starting immediately after irradiation or left uninjected. The recovery of lymphoid tissues induced by hematopoietic cytokines 7 days after irradiation and bone marrow cell transplantation was comparable to that observed at days 21-28 in irradiated, bone marrow-grafted, but cytokine-uninjected mice. IL-11 or IL-6, in combination with IL-3, was able to hasten thymus, spleen and blood cell numbers and functions. SCF also displayed a detectable effect when used with IL-3. Conversely, the IL-6 superagonist K-7/D-6 was able, when injected alone, to induce significant recovery of thymus, spleen and blood cells. Thus, K-7/D-6 appears to be a most efficient cytokine for fast reconstitution of lymphoid tissues after irradiation and bone marrow transplantation.     

Diagnostic significance of the number of bone marrow megakaryocytes in cases with decreased platelet production evidenced by platelet kinetic study

In 18 patients with decreased platelet production proved by reduced platelet turnover, the numbers of megakaryocytes in clot section of marrow aspirate were counted. Platelet counts ranged from 19,000 to 128,000/microliters. The sternal marrow showed decrease of megakaryocytes only in 3 out of 18 cases while megakaryocytes in the iliac marrow were reduced in 6 out of 11 cases. Only one of 11 cases showed decrease of megakaryocyte in both marrows examined. On the contrary, four cases showed normal number of megakaryocytes at both sites. Of 9 cases with normal or increased number of megakaryocytes in sternal and/or iliac marrow, no case showed morphologically abnormal megakaryocytes and only one case had the reduced number of platelet-forming megakaryocytes. Results suggested that the number of megakaryocytes in bone marrow especially in the sternum was not reliable for establishing the diagnosis of decreased platelet production, and that about 50% of patients with thrombocytopenia due to hypoproduction of platelets could be diagnosed pertinently only after the study of platelet kinetics.     

Proliferating normal bone marrow cells do stain for Ki-67 antigen

Summary The normal human bone marrow has been investigated in the past for the presence of the proliferation associated antigen detected by the Ki-67 antibody and aberrantly low scores for this antigen have been reported. We used a new Ki-67 equivalent antibody (MIU 1) and a formalin fixation of smears and trephine biopsies, and we report 52.8%±9.2 SD of the normal BM cells to stain for MIB 1.Late forms of the maturing blood cells compartment such as metamyelocytes and megakaryocytes were stained in cytokine-treated marrows.     

Immunohistochemical localization of membrane and alpha-granule proteins in plastic-embedded mouse bone marrow megakaryocytes and murine megakaryocyte colonies

Using an immunoperoxidase technique that permits optimal antigen localization at the light microscope level, we have detected two platelet alpha-granule constituents and three platelet membrane glycoproteins in mouse bone marrow megakaryocytes and in murine megakaryocyte colonies grown in soft agar culture for three to seven days. Using polyclonal antibodies prepared against human platelet proteins, we have demonstrated labeling for von Willebrand factor, fibrinogen, and the membrane glycoproteins IIIa and GMP-140 in both bone marrow megakaryocytes and megakaryocyte colonies after seven days of culture. Using monoclonal antibodies to membrane glycoproteins IIb and GMP-140, we have demonstrated label in mouse bone marrow megakaryocytes. Granulocyte and macrophage colonies were negative for each of these markers. Murine bone marrow megakaryocytes and megakaryocyte colonies demonstrated a similar enzyme histochemical pattern: weakly positive for alpha-naphthyl acetate esterase and negative for chloroacetate esterase. These data indicate that megakaryocytes grown in soft agar culture express many of the same glycoproteins as bone marrow megakaryocytes. Furthermore, the ability of antibodies directed against human platelet membrane glycoproteins to identify murine megakaryocyte glycoproteins indicates that these constituents have been highly conserved during evolution.     

Effects of Local Irradiation (Co60 Teletherapy) on the Peripheral Blood and Bone Marrow

1. Local Co⁶⁰ teletherapy caused a reduction in leukocytes and lymphocytesin the peripheral blood.

2. The bone marrow demonstrated no morphologic change in nonirradiatedcontrol sites.

3. Local irradiation produced a pronounced and persistent hypoplasia inthe treated sites during and after irradiation, with a great reduction in thenumbers of megakaryocytes and precursors of red and white cells. Duringthe period of greatest radiation effect the persistent cells were chiefly plasmacells, "mononuclear cells," and lymphocytes.

4. Even after "cancerocidal" radiotherapy, irradiated bone marrow showssome capacity to regenerate as evidenced by appearance of precursors ofvarious cell series and their ability to incorporate tritium-labeled thymidine.

5. Hemosiderin increased in varying degrees in irradiated sites but showedno change in the control sites.

6. Satisfactory marrow samples can be aspirated from the pubic bone.

Submitted on November 1, 1962 Accepted on December 27, 1962     

Amifostine stimulates the formation of hematopoietic bone marrow progenitors from B-cell chronic lymphocytic leukemia

Amifostine is a phosphorylated aminothiol that not only protects hematopoietic progenitor cells from chemotherapy and radiotherapy, but also stimulates normal hematopoiesis. The effect of amifostine on the in vitro growth of hematopoietic progenitors derived from B-cell chronic lymphocytic leukemia(B-CLL) was investigated. The colony-forming units (CFU)-granulocyte macrophage (CFU-GM), the burst-forming units-erythroid (BFU-E) and the CFU-granulocyte erythroid macrophage megakaryocytes (CFU-GEMM) increased 38, 20 and 100%, respectively, after the incubation with amifostine. There was no statistical difference in the in vitro progenitor growth of patients grouped according to their disease stage, bone marrow lymphocytic infiltration or therapy. Our data indicate that apart from cytoprotection the parallel use of amifostine and chemotherapy in patients with B-CLL could enhance bone marrow recovery.     

Junin virus infection of guinea pigs: immunohistochemical and ultrastructural studies of hemopoietic tissue

An association between viral antigens, cytopathic effect (CPE) and viral titers in blood and lymphoid tissues suggests a direct CPE of Junin virus on the lymphopoietic organs of guinea pigs infected with 10(3) 50% lethal doses of the XJ prototype strain. After seven days of infection, all lymphoreticular organs had infectivity titers higher than those for blood. Virus was recovered from bone marrow and lymph nodes at day 5 after infection; peak titers were obtained from bone marrow, spleen, and lymph nodes after day 10. Granular specific fluorescence was detected in the cytoplasm of reticular monocytes after day 7; megakaryocytes showed positive fluorescence, but specific staining of other lymphoid cells was not observed. Necrosis of bone marrow, lymph nodes, and spleen was observed after day 9. CPE consisted of overdevelopment of reticuloendoplasmic cisterne of reticulomonocytes and myeloblasts. Typical Junin virus particles were observed. Reticular cells were gradually destroyed, and simultaneous necrosis of surrounding lymphoid cells was observed.     

Engraftment of T-cell-depleted rabbit bone marrow

T cell depletion of donor bone marrow prevents graft-versus-host disease (GvHD) but increases the risk of rejection. Rabbit bone marrow was T-cell-depleted using the properties of rabbit T cells to form spontaneous rosettes in the cold and by incubation in methylprednisolone (1 mg/ml, 10(6) cells/ml). New Zealand white rabbits were transplanted with Red Burgundy rabbit bone marrow from the opposite sex after conditioning with 12 Gy total body irradiation. Untreated animals die of GvHD at day 23. Three groups were studied: T cell depletion plus ciclosporin (A), T-cell-depleted bone marrow plus irradiated autologous bone marrow plus irradiated donor buffy coat (B), and T-cell-depleted bone marrow plus irradiated autologous bone marrow plus irradiated donor buffy coat plus ciclosporin (C). Buffy coat cells irradiated with 15 Gy were given for 5 days. Such cells do not form colonies in culture; however, they are able to release interleukin-2. In group A, 9 of 15 animals rejected, 6 survived for 45 days (median, range 16-249 days). In group B, all 5 of 5 animals died of rejection (median survival time 14 days, range 13-20 days). In group C, 8 of 10 animals did engraft, 4 died of GvHD (median survival 48 days, range 26-58 days), and 4 are long-term survivors (greater than 6 months to greater than 1 year), 3 as complete chimeras. We conclude that the combination of irradiated donor buffy coat cells, irradiated autologous bone marrow and ciclosporin restores engraftment of T-cell-depleted mismatched bone marrow without losing the benefit of reduced GvHD.     

Modulation of collagenase 3 in human osteoarthritic cartilage by activation of extracellular transforming growth factor beta: role of furin convertase

OBJECTIVE: Treatment of normal cartilage with transforming growth factor beta (TGFbeta) can increase the synthesis of collagenase 3 by chondrocytes and mimic the in situ distribution of this enzyme in osteoarthritic (OA) cartilage, which occurs predominantly in the deep zone. In this study, we examined the elements of the TGFbeta system that are potentially relevant to this effect. METHODS: TGFbeta1 and TGFbeta2 levels in cultured cartilage explants were determined by enzyme-linked immunosorbent assay (ELISA). OA cartilage explants were treated with small latent TGFbeta1 complex in the presence of various inhibitors, and collagenase 3 levels were determined by ELISA. The inhibitors were against serine proteases, plasmin, cathepsins, furin, and a neutralizing antibody against the mannose-6 phosphate/ insulin-like growth factor 2 receptor (M6P/IGF-2R). Small latent TGFbeta1, TGFbeta receptor types I, II, and III (TGFbetaRI, RII, and RIII), M6P/IGF-2R, and furin were immunolocalized in cartilage. RESULTS: Our data showed that latent TGFbeta1 is the major isoform that is synthesized; levels of 17.2 +/-1.7 pg/mg and 1.1 +/- 0.3 pg/mg tissue wet weight (mean +/- SEM) were found for total TGFbeta1 and TGFbeta2, respectively, in OA cartilage. A general serine protease inhibitor abrogated activation of both endogenous and exogenous small latent TGFbeta1. Plasmin and furin inhibitors and anti-M6P/IGF-2R reduced the levels of exogenous small latent TGFbeta1 complex-induced collagenase 3 by 33%, 95%, and 76%, respectively, but the cathepsin inhibitor had no effect. Immunolocalization of the small latent TGFbeta1 complex as well as of TGFbetaRI and RII revealed a statistically significant increase in the chondrocyte score in only the deep zone of OA cartilage. The M6P/IGF-2R level was significantly higher in OA cartilage in both the superficial and deep zones. Furin was found in normal cartilage exclusively in the superficial zone, whereas in OA cartilage, a level similar to that in normal cartilage was found in the superficial zone, but a significantly higher cell score (mean +/- SEM 23.6 +/- 4.7%) was registered in the deep zone. CONCLUSION: The mechanisms of TGFbeta activation/ activity with regard to collagenase 3 modulation in cartilage appear to be controlled by furin convertase with or without M6P/IGF-2R. These factors and the small latent TGFbeta complex are increased in the deep zone of OA cartilage, corresponding to the preferential site of collagenase 3 production.