Introduction: Chlorhexidine gluconate (CHX) is widely used as a preoperative surgical skin-preparation solution and intra-wound irrigation agent, with excellent efficacy against wide variety of bacteria. The cytotoxic effect of CHX on local proliferating cells following orthopaedic procedures is largely undescribed. Our aim was to investigate the in vitro effects of CHX on primary fibroblasts, myoblasts, and osteoblasts.

Establishment of skeletal metastasis involves bidirectional interactions between the tumor cell and the cellular elements in the bone microenvironment. A better understanding of the pathophysiology of bone metastasis will be critical in developing the means to prevent bone metastasis or inhibit its progression. The receptor activator of nuclear factor-κB (RANK)/RANK ligand pathway has emerged as the key pathway regulating osteolysis in skeletal metastasis. A number of candidate factors, including the Wnt (wingless int) proteins, endothelin-1, and bone morphogenetic proteins, have been implicated in the establishment of osteoblastic metastasis. The complex nature of tumor-bone microenvironment interactions and the presence of multiple pathways that lead to bone metastasis suggests that simultaneous targeting of these pathways in the metastatic cascade are required for effective treatment. This review discusses current understanding of the pathophysiologic mechanisms that underlie the establishment of bone metastasis and potential molecular therapeutic strategies for prevention and treatment of bone metastasis.

Background: Mesenchymal stem cells are multipotent and have the ability to differentiate into bone. We conducted a preclinical trial comparing the osteogenic potential of human bone marrow aspirate with that of mesenchymal stem cell-enriched bone marrow aspirate (both mixed with demineralized bone matrix) in a critical-sized rat femoral defect model. Methods: The buffy coat was extracted from human bone marrow aspirate to obtain mesenchymal stem cell-enriched bone marrow aspirate. Fifty-nine athymic rats, each with a 6-mm femoral defect, were divided into six treatment groups: defect only (Group I), demineralized bone matrix and saline solution (Group II), demineralized bone matrix and bone marrow aspirate (Group III), demineralized bone matrix and mesenchymal stem cell-enriched bone marrow aspirate (Group IV), demineralized bone matrix and recombinant human bone morphogenetic protein-2 (rhBMP-2) (Group V [positive control]), and absorbable collagen sponge and rhBMP-2 (Group VI [positive control]). All animals were killed at twelve weeks for radiographic, micro-computed tomography, histomorphometric, and histologic analysis. Results: There was wide variability in the mesenchymal stem cell concentrations obtained from the human donors. All ten defects healed in the positive control groups (Groups V and VI). Only one defect healed in each experimental group (Groups II, III, and IV) (i.e., three of forty-four defects healed). There was no significant difference among the radiographic scores of Groups II, III, and IV (p = 0.59), and the score for each of those groups was significantly higher than that for Group I (p ≤ 0.005) and significantly lower than those for Groups V and VI (p ≤ 0.001). The bone volume and mineral density did not differ among Groups III, IV, and V (p = 0.53). The percent total bone volume and percent normal bone volume in Group VI were significantly higher than those values in Groups I, III, and IV (p < 0.0001) and those in Group II (p = 0.048). In Groups II through V, the cortical bone was more dense than the lace-like bone in Group VI. Conclusions: Neither bone marrow aspirate nor mesenchymal stem cell-enriched bone marrow aspirate mixed with demineralized bone matrix resulted in reliable healing of critical-sized bone defects. It is possible that a greater number of mesenchymal stem cells or an enhanced osteoinductive signal is required for adequate bone-healing. Mesenchymal stem cell and/or carrier variability may also contribute to differences in bone formation. Clinical Relevance: This study identified potential problems when adapting the use of mesenchymal stem cells for consistent bone repair in a clinical setting.

Ex-vivo regional gene therapy with bone marrow cells (BMCs) overexpressing bone morphogenetic protein-2 (BMP-2) has demonstrated efficacy in healing critical sized bone defects in preclinical studies. The purpose of this preclinical study was to compare the osteoinductive potential of a novel “same day” ex-vivo regional gene therapy versus a traditional two-step approach, which involves culture expansion of the donor cells before implantation. In the “same day” strategy buffy coat cells were harvested from the rat bone marrow, transduced with a lentiviral vector-expressing BMP-2 for 1 hour and implanted into a rat femoral defect in the same sitting. There was no significant difference (P = 0.22) with respect to the radiographic healing rates between the femoral defects treated with the “same day” strategy (13/13; 100%) versus the traditional two-step approach (11/14; 78%). However, the femoral defects treated with the “same day” strategy induced earlier radiographic bone healing (P = 0.004) and higher bone volume (BV) [micro-computed tomography (micro-CT); P < 0.001]. The “same day” strategy represents a significant advance in the field of ex-vivo regional gene therapy because it offers a solution to limitations associated with the culture expansion process required in the traditional ex vivo approach. This strategy should be cost-effective when adapted for human use.