GM-CSF Inhibits c-Kit and SCF Expression by Bone Marrow-Derived Dendritic Cells

Stem cell factor (SCF), the ligand of c-kit, is a key cytokine for hematopoiesis. Hematopoietic precursors express c-kit, whereas differentiated cells of hematopoietic lineage are negative for this receptor, with the exception of NK cells, mast cells, and a few others. While it has long been recognized that dendritic cells (DCs) can express c-kit, several questions remain concerning the SCF/c-kit axis in DCs. This is particularly relevant for DCs found in those organs wherein SCF is highly expressed, including the bone marrow (BM). We characterized c-kit expression by conventional DCs (cDCs) from BM and demonstrated a higher proportion of c-kit⁺ cells among type 1 cDC subsets (cDC1s) than type 2 cDC subsets (cDC2s) in both humans and mice, whereas similar levels of c-kit expression were observed in cDC1s and cDC2s from mouse spleen. To further study c-kit regulation, DCs were generated with granulocyte-macrophage colony-stimulating factor (GM-CSF) from mouse BM, a widely used protocol. CD11c⁺ cells were purified from pooled non-adherent and slightly adherent cells collected after 7 days of culture, thus obtaining highly purified BM-derived DCs (BMdDCs). BMdDCs contained a small fraction of c-kit⁺ cells, and by replating them for 2 days with GM-CSF, we obtained a homogeneous population of c-kit⁺ CD40^hi MHCII^hi cells. Not only did BMdDCs express c-kit but they also produced SCF, and both were striking upregulated if GM-CSF was omitted after replating. Furthermore, a small but significant reduction in BMdDC survival was observed upon SCF silencing. Incubation of BMdDCs with SCF did not modulate antigen presentation ability of these cells, nor it did regulate their membrane expression of the chemokine receptor CXCR4. We conclude that the SCF/c-kit-mediated prosurvival circuit may have been overlooked because of the prominent use of GM-CSF in DC cultures in vitro, including those human DC cultures destined for the clinics. We speculate that DCs more prominently rely on SCF in vivo in some microenvironments, with potential implications for graft-versus-host disease and antitumor immunity.

PATHOLOGIC AND IMPENDING FRACTURES: BIOLOGICAL AND CLINICAL ASPECTS

Bone metastases from carcinomas are epidemiologically rising because of the increased survival rate of oncologic patients, related to several factors such as improvement of primary and secondary screening, advancement of medical research and technology and the better understanding of mechanisms underlying bone metastases origination from primary tumor. Skeletal Related Events (SREs) can seriously affect quality of life in patients with metastatic disease. These events include the necessity of radiotherapy or bone surgery, malignant hypercalcemia, pathologic fractures and spinal cord compression. Among the SREs, pathologic fractures are the most disabling events and represent an emergency in these delicate patients. A pathologic fracture is defined as a fracture that occurs at the level of a pre-existing bone lesion (that is often a tumor), spontaneously or as the result of low-energy trauma (1). The pre-existence of the metastatic lesion in the bone, its evaluation and the assessment of progression can make these complications predictable and preventable. Pathologic fractures imply several severe consequences, including patient immobilization (in the case of fractures involving the lower limbs), loss of autonomy, anaemia, need of blood transfusion, discontinuation of medical therapies or radiotherapy and protracted hospitalization. Secondary effects of prolonged immobilization and loss of autonomy further lengthen this list of complications in patients who are already significantly limited in their activities. In the present paper, the authors present a review on the main aspects involved in bone metastastic disease: biology, quality of life, economic impact and survival.

Fractures in bone tumour prosthesis

PURPOSE

The aim of the present narrative review is to report the different aspects related to the fractures around tumour prosthetic implants in terms of technical and medical issues.

METHODS

A non systematic literature review on the topic was performed.

RESULTS

Given the increased rate of limb salvage procedures and megaprostheses implanted for bone tumours, the increased number of osteoporotic periprosthetic fractures, and the burden of revision arthroplasty, the number of surgeries using endoprosthetic implants is likely to increase in the near future. Surgeons will face more frequently the complications related to tumour endoprosthetic implant. Endoprosthetic reconstruction has a higher risk of intra-operative and post-operative complications compared to conventional prosthetic replacement.

CONCLUSIONS

Very rare reports and recommendations are available in literature regarding the treatment of periprosthetic fractures after megaprosthesis, and there is currently no consensus about which should be the standard management for periprosthetic fractures in this population of patients.

The impact of aging on rotator cuff tear size

INTRODUCTION

The aim of our study was to establish if aging influences rotator cuff tear size.

PATIENTS AND METHODS

We studied 586 consecutive patients (280 M, 306 F) mean age 59 years old (range 46-73) who underwent arthroscopic rotator cuff repair. Tear size was determined during surgery. For the purpose of our study, patients were divided into two groups based on age older than 60 years. A multinomial logistic regression model was applied to explore the association between age older than 60 years and tear size. We used the ANCOVA method to determine whether the aging influences the severity of the tear. All analyses were adjusted for gender.

RESULTS

Age older than 60 years was associated with a twofold higher overall risk of tear occurrence (OR = 2.12, 95 % CI 1.44-3.01). While no association was detected between age older than 60 years and the probability of a small tear (OR = 0.58, 95 % CI 0.27-1.07), subjects older than 60 years were twice more likely to experience a large tear (OR = 2.29, 95 %CI 1.51-3.27) and three times more likely to experience a massive tear (OR = 3.09, 95 % CI 2.07-5.38) as opposed to younger subjects. Mean age significantly increased from small tear (53.8 years) to large tear (66.8 years) to massive tear (69.4 years) patients (ANCOVA: F(2, 437) = 16.487, p = 1.51 × 10(-7)).

DISCUSSION

We found a significantly older mean age in patients with a more severe tear. Our data provide and confirm evidence that aging is a significant risk factor for the occurrence and severity of rotator cuff tears.

Complex fracture-dislocations of the proximal ulna and radius in adults: a comprehensive classification

BACKGROUND

Complex fracture-dislocations of the proximal ulna and radius include multiple anatomic lesions, the management of which is known to be demanding. Although several classifications have been proposed, none appear to be exhaustive, and most of them have neither therapeutic nor prognostic value. The purpose of this study was to design a comprehensive classification that may provide a guide for the operative management of these injuries.

MATERIALS AND METHODS

The classification is aimed at identifying definite anatomic lesions, called the "main lesions," the presence of which can affect the prognosis and require peculiar treatments. The main lesions include (1) ulnar fracture (including its location with respect to the insertion of collateral ligaments and coronoid fracture), (2) radiohumeral dislocation, (3) proximal radioulnar dislocation, (4) radial fracture, (5) distal radioulnar joint and interosseous membrane lesion, and (6) humeral-ulnar dislocation. Intraobserver and interobserver reliability was assessed in 25 complex fracture-dislocations. Standard radiographs and computed tomography scans were analyzed by 3 independent observers.

RESULTS

The main lesions were labeled by an alphanumeric system. Numbers 1 through 6 identified the type of ulnar fracture, and letters A through E indicated the dislocated joint or presence of a radial fracture. The direction of dislocation and the type of radial fracture were identified by Roman numerals, from I to III, placed after the letter. A κ value of 0.873 or greater resulted from intraobserver and interobserver evaluation.

CONCLUSION

We created a comprehensive classification of complex fracture-dislocations of the elbow. The classification appeared to be reproducible and may represent a useful tool for the management of such difficult injuries.

Management of complex elbow instability

Complex elbow instability is a challenging injury even for expert elbow surgeons. The preoperative radiographs should be carefully evaluated to recognize all lesions that may occur in complex elbow instabilities. Recognizing all the possible lesions is critical to achieve an optimal outcome. The most common types of injuries are as follows: (1) radial head fractures associated with lateral and medial collateral ligaments lesions (with or without elbow dislocation); (2) Coronoid fractures and lateral collateral ligament lesion (with or without elbow dislocation); (3) Terrible Triad; (4) Transolecranon fracture-dislocation; (5) Monteggia-like-lesions; and (6) Humeral Shear fractures associated with lateral and medial collateral ligaments lesions (with or without elbow dislocation). A correct evaluation includes X-rays, CT scan with 2D and 3D reconstruction and stability test under fluoroscopy. The treatment is always surgical and is challenging, and outcomes are not predictable. The goals of treatment are (1) to perform a stable osteosynthesis of all fractures, (2) to obtain concentric and stable reduction of the elbow and (3) to allow early motion. The proximal ulna must be anatomically reduced and fixed; the radial head must be repaired or replaced, and the coronoid fractures must be repaired or reconstructed. With respect of soft tissue lesions, the LUCL must be reattached with suture anchors or trans-osseous suture. The next critical step is the intra-operative assessment of elbow stability. If the elbow remains unstable, MCL repair and/or application of hinged external fixator must be considered. The most recent clinical and experimental studies have significantly expanded our knowledge of elbow instability and its management. Definite treatment protocols may improve the clinical results of such complex injuries.