Thrombopoietin, but not erythropoietin, directly stimulates multilineage growth of primitive murine bone marrow progenitor cells in synergy with early acting cytokines: distinct interactions with the ligands for c-kit and FLT3

Thrombopoietin (Tpo), the ligand for c-mpl, has been shown to be the principal regulator of megakaryocytopoiesis and platelet production. The ability of Tpo to potently stimulate the growth of committed megakaryocyte (Mk) progenitor cells has been studied in detail. Murine fetal liver cells, highly enriched in primitive progenitors, have been shown to express c-mpl, but little is known about the ability of Tpo to stimulate the growth and differentiation of primitive multipotent bone marrow (BM) progenitor cells. Here, we show that Tpo alone and in combination with early acting cytokines can stimulate the growth and multilineage differentiation of Lin- Sca-1+ BM progenitor cells. In particular, Tpo potently synergized with the ligands for c-kit (stem cell factor [SCF]) and flt3 (FL) to stimulate an increase in the number and size of clones formed from Lin- Sca-1+ progenitors. When cells were plated at 1 cell per well, the synergistic effect of Tpo was observed both in fetal calf serum-supplemented and serum-depleted medium and was decreased if the addition of Tpo to cultures was delayed for as little as 24 hours, suggesting that Tpo is acting directly on the primitive progenitors. Tpo added to SCF + erythropoietin (Epo)-supplemented methylcellulose cultures potently enhanced the formation of multilineage colonies containing granulocytes, macrophages, erythrocytes, and Mks. SCF potently enhanced Tpo-stimulated production of high-ploidy Mks from Lin- Sca-1+ progenitors, whereas the increased growth response obtained when combining Tpo with FL did not translate into increased Mk production. The ability of Tpo and SCF to synergistically enhance the growth of Lin- Sca-1+ progenitors was predominantly observed in the more primitive rhodamine 123(lo) fraction. Tpo also enhanced growth of Lin- Sca-1+ progenitors when combined with interleukin-3 (IL-3) and IL-11 but not with IL-12, granulocyte colony-stimulating factor, granulocyte-macrophage colony- stimulating factor, or Epo. Epo, which has high homology to Tpo, was unable to stimulate the growth of Lin- Sca-1+ progenitors alone or in combination with SCF or FL, suggesting that c-mpl is expressed on more primitive stages of progenitors than the Epo receptor. Thus, the present studies show the potent ability of Tpo to enhance the growth of primitive multipotent murine BM progenitors in combination with multiple early acting cytokines and documents its unique ability to synergize with SCF to enhance Mk production from such progenitors.     

Percutaneous cannulated screw fixation in the treatment of distal radius fractures

Purpose

The aim of this study was to determine the results of closed reduction and percutaneous fixation of distal radial fractures with standard 4.0-mm cannulated screw.

Methods

We collected prospective outcomes data for 20 patients between 18 and 60?years of age (mean 39) with acute, displaced, extraarticular and unstable fractures of the distal radius treated with closed reduction, percutaneous cannulated screw fixation and early mobilization. The visits at months 2, 6 and 12 were specified as index follow-up visits and assessments of motion, grip strength and standard radiographs were performed. The Gartland Werley functional scores and the Disabilities of the Arm, Shoulder and Hand (QuickDASH) scores were recorded.

Results

Mean values of flexion, extension, pronation and supination on the injured side were up to 70?% of those on the uninjured side at 2?months postoperatively. By 12?months, range of motion values on the injured side showed continuous and significant improvement and flexion, extension, pronation, supination and ulnar deviation reached up to 90?% of those on the uninjured side. A large and significant improvement was seen from 2 to 6?months in the QuickDASH score. A smaller improvement was seen from 6 to 12?months, which was judged not to be significant. Radiographic values were close to anatomic parameters, and the alignment was maintained at 12?months follow-up. No complications occurred.

Conclusions

Cannulated screw fixation appears to be an effective means of allowing immediate range of motion of the wrist, resulting in a rapid and comfortable functional recovery while maintaining alignment to bone healing.     

Thrombopoietin, but not erythropoietin promotes viability and inhibits apoptosis of multipotent murine hematopoietic progenitor cells in vitro

The recently cloned c-mpl ligand, thrombopoietin (Tpo), has been extensively characterized with regard to its ability to stimulate the growth, development, and ploidy of megakaryocyte progenitor cells and platelet production in vitro and in vivo. Primitive hematopoietic progenitors have been shown to express c-mpl, the receptor for Tpo. In the present study, we show that Tpo efficiently promotes the viability of a subpopulation of Lin-Sca-1+ bone marrow progenitor cells. The ability of Tpo to maintain viable Lin-Sca-1+ progenitors was comparable to that of granulocyte colony-stimulating factor and interleukin-1, whereas stem cell factor (SCF) promoted the viability of a higher number of Lin-Sca-1+ progenitor cells when incubated for 40 hours. However, after prolonged (> 40 hours) preincubation, the viability- promoting effect of Tpo was similar to that of SCF. An increased number of progenitors surviving in response to Tpo had megakaryocyte potential (37%), although almost all of the progenitors produced other myeloid cell lineages as well, suggesting that Tpo acts to promote the viability of multipotent progenitors. The ability of Tpo to promote viability of Lin-Sca-1+ progenitor cells was observed when cells were plated at a concentration of 1 cell per well in fetal calf serum- supplemented and serum-depleted medium. Finally, the DNA strand breakage elongation assay showed that Tpo inhibits apoptosis of Lin-Sca- 1+ bone marrow cells. Thus, Tpo has a potent ability to promote the viability and suppress apoptosis of primitive multipotent progenitor cells.     

The influence of vertebral instability on peridural circulation and concomitant peridural fibrosis formation

An animal model of vertebral instability was used to analyze the effect of chronic lumbar instability on the peridural vasculature and fibrosis formation. Fifty mature male domestic rabbits were divided into five equal groups. The vertebral instability was performed by excision of supra and interspinous ligaments between L2-L3 and L3-L4, excision of transverse and spinous processes and making bilateral laminectomies and facetectomies in groups I, II, III and IV. In group V only para vertebral muscle dissection was performed without vertebral instability. The simulation of the long term effects of overuse model on unstable spines (chronic instability) were performed with the use of Electrical Neuromuscular Stimulator to simulate cyclic flexion–extension movement in groups I, II. The rabbits in group I and III were sacrified for the histological evaluation at postoperative fifth day. The rabbits in groups I II, IV and V were sacrified at postoperative 21st day. There was no peridural venous endothelial injury or stasis but there was an increased amount of polymorph nuclear leukocytes in both group I (unstable-overuse) and group III (unstable-no overuse) after sacrification at postoperative fifth day. Peridural fibrosis and also vascular changes with different grades were seen in group II, VI and V after sacrification at postoperative 21th day. The grade of the venous changes and the mean amount of peridural scar formation were prominently higher in group II (unstable-overuse) than in group IV (unstable-no overuse) and V (control group). There was no difference between group IV and V for peridural scar formation and vascular changes. In conclusion, the instability of the lumbar spine with overuse could be a cause of peridural venous circulatory impairment, resulting in fibrosis formation.     

Pelvic hydatid disease: CT and MRI findings causing sciatica.

Pelvic masses, especially hydatid disease, rarely present with sciatica (1, 2). We present the computed tomography (CT) and the magnetic resonance imaging (MRI) findings of a 49-year-old female patient with presacral hydatid disease, who was evaluated for her sciatica. We also want to emphasize the importance of assessing the pelvis of patients with symptoms and clinical findings that are inconsistent and that cannot be satisfactorily explained by the spinal imaging findings.     

Adenosine deaminase activity in protein-energy malnutrition

Cell-mediated immunity (CMI) was evaluated in 69 children with protein-energy malnutrition (PEM) and 20 healthy controls. Significantly decreased responses to purified protein derivative (PPD) ( p < 0.02) and absolute lymphocyte count (ALC) ( p < 0.01) and increased serum adenosine deaminase (ADA) activity ( p < 0.001) were observed in PEM cases compared with the controls. The mean values of ALC and ADA activity in PEM patients were 85.9% and 158.7% of the normal mean, respectively. A significant negative correlation was observed between the two parameters ( r = −0.2765, p < 0.01). The CMI tests were abnormal in all three grades of PEM, except for the response to PPD in grade I, when compared with the controls. No significant differences were found between infected and uninfected PEM cases. Thus, impaired CMI was observed not only in grades II and III but also in grade I PEM patients and the concomitant infection did not affect its status. However, ADA activity demonstrated a more pronounced change than the other tests     

Congenital lobar emphysema

Congenital lobar emphysema, a life-threatening respiratory disorder presenting in infancy is best diagnosed by chest x-ray. Abnormality of bronchial cartilage is one of the suspected aetiological factors. Prompt lobectomy is the treatment of choice as conservative treatment carries an unacceptably high mortality and morbidity. One such patient, a 3-month-old child who underwent successful emergency left upper lobectomy is presented.     

An alternative method for the treatment of nonunion of the tibia with bone loss

In this retrospective study we evaluated the method of acute shortening and distraction osteogenesis for the treatment of tibial nonunion with bone loss in 17 patients with a mean age of 36 years (10 to 58). The mean bone loss was 5.6 cm (3 to 10). In infected cases, we performed the treatment in two stages. The mean follow-up time was 43.5 months (24 to 96). The mean time in external fixation was 8.0 months (4 to 13) and the mean external fixator index was 1.4 months/cm (1.1 to 1.8). There was no recurrence of infection. The bone evaluation results were excellent in 16 patients and good in one, while functional results were excellent in 15 and good in two. The complication rate was 1.2 per patient. We conclude that acute shortening and distraction osteogenesis is a safe, reliable and successful method for the treatment of tibial nonunion with bone loss, with a shorter period of treatment and lower rate of complication.