Controlled delivery of mesenchymal stem cells and growth factors using a nanofiber scaffold for tendon repair.

Outcomes after tendon repair are often unsatisfactory, despite improvements in surgical techniques and rehabilitation methods. Recent studies aimed at enhancing repair have targeted the paucicellular nature of tendon for enhancing repair; however, most approaches for delivering growth factors and cells have not been designed for dense connective tissues such as tendon. Therefore, we developed a scaffold capable of delivering growth factors and cells in a surgically manageable form for tendon repair. Platelet-derived growth factor BB (PDGF-BB), along with adipose-derived mesenchymal stem cells (ASCs), were incorporated into a heparin/fibrin-based delivery system (HBDS). This hydrogel was then layered with an electrospun nanofiber poly(lactic-co-glycolic acid) (PLGA) backbone. The HBDS allowed for the concurrent delivery of PDGF-BB and ASCs in a controlled manner, while the PLGA backbone provided structural integrity for surgical handling and tendon implantation. In vitro studies verified that the cells remained viable, and that sustained growth factor release was achieved. In vivo studies in a large animal tendon model verified that the approach was clinically relevant, and that the cells remained viable in the tendon repair environment. Only a mild immunoresponse was seen at dissection, histologically, and at the mRNA level; fluorescently labeled ASCs and the scaffold were found at the repair site 9days post-operatively; and increased total DNA was observed in ASC-treated tendons. The novel layered scaffold has the potential for improving tendon healing due to its ability to deliver both cells and growth factors simultaneously in a surgically convenient manner.

Nicotine delays tendon-to-bone healing in a rat shoulder model.

BACKGROUND: Many studies have shown that nicotine negatively impacts fracture healing and bone fusion processes. However, very little is known about its effect on tendon and ligament healing. The goal of the present study was to evaluate the effect of nicotine on tendon-to-bone healing. METHODS: Supraspinatus tendons in both shoulders of seventy-two rats were transected and repaired to the humeral head. Osmotic pumps were implanted subcutaneously, and nicotine or saline solution was delivered for ten, twenty-eight, or fifty-six days. Cell morphology was evaluated with use of histologic sections. Cells were counted, and proliferating cell nuclear antigen (PCNA) immunohistochemistry was performed to assess cellular proliferation. In situ hybridization was performed to measure type-I collagen mRNA expression. Biomechanical and geometric properties were assessed. RESULTS: Inflammation persisted longer in the nicotine group than in the saline solution group. Cellular proliferation was higher in the saline solution group than in the nicotine group at the early time-points. Type-I collagen expression was higher in the saline solution group at twenty-eight days. Mechanical properties increased over time in both groups. Maximum stress was significantly lower in the nicotine group than in the saline solution group at ten days. Maximum force was significantly lower in the nicotine group than in the saline solution group at twenty-eight days. Maximum force was significantly higher in the nicotine group than in the saline solution group at fifty-six days. Stiffness was not different between the groups at any time-point. CONCLUSIONS: Nicotine caused a delay in tendon-to-bone healing in a rat rotator cuff animal model. Mechanical properties increased over time in both groups, but the properties in the nicotine group lagged behind those in the saline solution group. Chronic inflammation and decreased cell proliferation may partly explain the inferior biomechanical properties in the nicotine group as compared with the saline solution group. CLINICAL RELEVANCE: Failure of rotator cuff repair is a major clinical problem. The adverse effect of nicotine on rotator cuff healing noted in this clinically appropriate animal model may be an important clinical consideration.

Delayed repair of tendon to bone injuries leads to decreased biomechanical properties and bone loss.

INTRODUCTION: Repair of the torn rotator cuff tendon is a common procedure performed in the shoulder. In the clinical setting, a significant delay between rotator cuff tear and subsequent repair often exists. The purpose of this study was to investigate the biomechanical properties and bone density of the tendon to bone repair site after acute and delayed repair. METHODS: The supraspinatus tendons in bilateral shoulders of 60 rats were transected from the bone. In the acute group, the tendons were immediately repaired with suture. In the delayed group, the tendons were allowed to retract and repaired in a second procedure after a 3-week delay. Cross sectional area and biomechanical properties were evaluated. Bone density of the humeral head was assessed using peripheral quantitative computed tomography. Histologic sections were obtained and examined. RESULTS: At 10 days the repair tissue displayed vascular and fibroblast proliferation accompanied by predominantly mononuclear infiltrate. At 28 days the inflammatory process gradually decreased. No significant histologic differences were noted between the acute and delayed repair specimens. Cross-sectional area was higher in the delayed group at the early time points (44% at 10 days and 31% at 28 days). Viscoelastic properties were greater in the acute group at the early time points and significantly less at the latest time point, compared to the delayed group. Bone density was markedly decreased (8% and 12%, 28 and 56 days respectively) in the delay group. DISCUSSION: Inferior rotator cuff healing was demonstrated when there was a delay between injury and repair. Viscoelastic properties of the acute repairs were increased compared to the delayed group at 10 days, indicating tendon stiffening during the 3-week delay before repair. Viscoelastic properties of the acute repairs were decreased compared to the delayed group at 56 days indicating deterioration of properties over time in the delayed group. The deterioration in properties in the delayed group coincide with bone density decreases in the greater tuberosity. These results indicate that bone loss may a significant factor in poor healing.

Familial dementia with Lewy bodies: clinicopathologic analysis of two kindreds.

Familial cases of dementia with Lewy bodies (DLB) are rare. The authors describe two small kindreds with familial DLB: one with pure DLB meeting consensus criteria for DLB and one with coexistent AD pathology that did not fulfill DLB criteria. The authors call attention to the diverse features of DLB and suggest that current clinical criteria may not detect all cases. Familial DLB is clinically heterogeneous and occurs with or without coexistent AD, suggesting the relevance of LB pathology for the developing dementia.

The neuronal repellent Slit inhibits leukocyte chemotaxis induced by chemotactic factors.

Migration is a basic feature of many cell types in a wide range of species. Since the 1800s, cell migration has been proposed to occur in the nervous and immune systems, and distinct molecular cues for mammalian neurons and leukocytes have been identified. Here we report that Slit, a secreted protein previously known for its role of repulsion in axon guidance and neuronal migration, can also inhibit leukocyte chemotaxis induced by chemotactic factors. Slit inhibition of the chemokine-induced chemotaxis can be reconstituted by the co-expression of a chemokine receptor containing seven transmembrane domains and Roundabout (Robo), a Slit receptor containing a single transmembrane domain. Thus, there is a functional interaction between single and seven transmembrane receptors. Our results reveal the activity of a neuronal guidance cue in regulating leukocyte migration and indicate that there may be a general conservation of guidance mechanisms underlying metazoan cell migration. In addition, we have uncovered an inhibitor of leukocyte chemotaxis, and propose a new therapeutic approach to treat diseases involving leukocyte migration and chemotactic factors.

Is t(6;14) a non-random translocation in childhood acute mixed lineage leukemia?

We report a case of childhood acute mixed lineage leukemia (AMLL) with a translocation t(6;14)(q25;q32) as the main clonal abnormality. A comparison of this case with another one with similar cytogenetics and clinical findings may suggest that t(6;14)(q25;q32) is a non-random occurrence in childhood AMLL.

Cytologic findings in a case of T-cell rich B-cell lymphoma: potential diagnostic pitfall in FNA of lymph nodes.

Fine-needle aspiration biopsy (FNAB) is a reliable diagnostic technique for most palpable masses. This technique is utilized routinely to diagnose metastatic carcinoma and melanomas in lymph nodes. However, the role of FNAB in the investigation of lymphoproliferative lesions is still controversial. Recent publications have supported the use of FNAB cytology, in conjunction with immunophenotyping, as an accurate, reliable diagnostic modality for the classification of most lymphomas (Sneige et al., Acta Cytol 1990; 34:311-322; Skoog and Tani, Diagn Oncol 1991; 1:12-18; Robins et al., Am J Clin Pathol 1994; 101:569-576; Katz, Clin Lab Med 1991; 11:469-499). We present a case of a T-cell rich, large B-cell lymphoma. Material obtained by FNAB mimicked a reactive process by both cytomorphological and immunophenotypical analysis. This case demonstrates a potential pitfall in the use of FNAB to evaluate lymphoproliferative disorders even when used in conjunction with immunophenotypic studies. The case also emphasizes the need for detailed clinical and prior pathologic information when a cytologic sample is being evaluated for a lymphoproliferative disorder. To our knowledge, the cytomorphologic findings of this particular type of lymphoma have not been previously described as seen on an FNAB.

Primary Ki-1 (anaplastic large cell) lymphoma of the brain and spinal cord.

The authors report a case of primary Ki-1 lymphoma of the brain. The patient was a 4 1/2-year-old black girl who presented with a 4- and 5-day history of headaches, nausea, vomiting, neck stiffness, and difficulty in walking. Computed tomography (CT) scan of the brain showed two discrete densities in the left occipital lobe and in the brain stem. Magnetic resonance imaging (MRI) showed multiple densities scattered over the brain surface and brain stem. Microscopically, the tumor was an anaplastic neoplasm that diffusely infiltrated brain parenchyma. The neoplastic cells were large with amphophilic cytoplasm, large nuclei with irregular nuclear contours and prominent nucleoli. A high mitotic rate including atypical mitotic figures was noted. Immunohistochemical stains showed diffuse strong positivity for CD30 and moderate focal staining for epithelial membrane antigen. Leukocyte common antigen, cytokeratin, neuron specific enolase, monocyte/macrophage and B- and T-marker stains were negative. The histology was characteristic for Ki-1 large cell lymphoma. Cytologic examination of cerebrospinal fluid (CSF) demonstrated similar neoplastic cells. This is one of the first reports of this variant in the pediatric population.