Microencapsulation of Stem Cells for Therapy.

An increasing demand to regenerate tissues from patient-derived sources has led to the development of cell-based therapies using autologous stem cells, thereby decreasing immune rejection of scaffolds coupled with allogeneic stem cells or allografts. Adult stem cells are multipotent and are readily available in tissues such as fat and bone marrow. They possess the ability to repair and regenerate tissue through the production of therapeutic factors, particularly vasculogenic proteins. A major challenge in cell-based therapies is localizing the delivered stem cells to the target site. Microencapsulation of cells provides a porous polymeric matrix that can provide a protected environment, localize the cells to one area, and maintain their viability by enabling the exchange of nutrients and waste products between the encapsulated cells and the surrounding tissue. In this chapter, we describe a method to produce injectable microbeads containing a tunable number of stem cells using the biopolymer alginate. The microencapsulation process involves extrusion of the alginate suspension containing cells from a microencapsulator, a syringe pump to control its flow rate, an electrostatic potential to overcome capillary forces and a reduced Ca++ cross-linking solution containing a nutrient osmolyte, to form microbeads. This method allows the encapsulated cells to remain viable up to three weeks in culture and up to three months in vivo and secrete growth factors capable of supporting tissue regeneration.

The use of a T-plate as "spring plates" for small comminuted posterior wall fragments.

In the treatment of posterior wall fractures of the acetabulum, a modified distal radius T-plate can be substituted for one third tubular spring plates for fixation of thin, small, or comminuted posterior wall fragments. This technique is described as well as a case series of 33 patients with various posterior wall acetabular fractures.

Alginate microencapsulation technology for the percutaneous delivery of adipose-derived stem cells.

BACKGROUND: Autologous fat is the ideal soft-tissue filler; however, its widespread application is limited because of variable clinical results and poor survival. Engineered fillers have the potential to maximize survival. Alginate is a hydrogel copolymer that can be engineered into spheres of <200 µm, thus facilitating mass transfer, allowing for subcutaneous injection, and protecting cells from shearing forces. METHODS: Alginate powder was dissolved in saline, and adipose-derived stem cells (ADSCs) were encapsulated (1 million cells/mL) in alginate using an electrostatic bead generator. To assess effects of injection on cell viability, microspheres containing ADSCs were separated into 2 groups: the control group was decanted into culture wells and the injection group was mixed with basal media and injected through a 21-gauge needle into culture wells. Microbeads were cultured for 3 weeks, and cell number and viability were measured weekly using electron and confocal microscopy. To assess effects of percutaneous injection in vivo, twenty-four male nude mice were randomly separated into 2 groups and injected with either empty microcapsules or ADSC-laden microcapsules. Mice were harvested at 1 and 3 months, and the implants were examined microscopically to assess bead and cell viability. RESULTS: A flow rate of 5 mL/h and an electrostatic potential of 7 kV produced viable ADSC-laden microbeads of <200 µm. There were no differences in bead morphology and ADSC viability between microcapsules placed versus injected into tissue culture plates for up to 3 weeks. Microspheres implanted in a nude mouse model show durability up to 3 months with a host response around each individual sphere. ADSCs remained viable and showed signs of mitosis. CONCLUSIONS: ADSCs can be readily cultured, encapsulated, and injected in alginate microspheres. Stem cells suspended in alginate microspheres survive in vivo and are seen to replicate in vitro.

Sub-muscular plating of the humerus: an emerging technique.

OBJECTIVE: The purpose of the present study was to evaluate percutaneous sub-muscular internal fixation using a locked screw methodology for treatment of diaphyseal humeral fractures. METHODS: Inclusion criteria were multiple extremity fractures, open fractures, neurovascular injuries,additional ipsilateral upper extremity fractures, the inability to obtain a satisfactory closed reduction and isolated fractures with circumstances that prevented effective bracing. Exclusion criteria were immaturity, neoplasm, infection and intra-articular extensions in the same bone. Outcome measures included clinical and radiographic healing, complications, elbow and shoulder symptoms, range of motion (ROM) and Constant­Murley (CM) scores. RESULTS: Thirty-one patients with 32 fractures were evaluated with a mean follow-up of 16 months (3­38 months). There was radiographic healing in 31 out of the 32 fractures; the non-union was revised to open plating at 6 months and healed uneventfully. Hardware complications included two construct disengagements; one patient was revised and healed, and the other achieved union with bracing.Neurovascular complications included one preoperative nerve palsy that recovered by 3 months, two partial to complete postoperative nerve palsies that recovered by 6 months, and one intact-to-complete nerve palsy due to a bone fragment that required decompression with full recovery by 3 weeks. All patients had functional ROM with a mean CM score of 88. There were no elbow complaints and minor shoulder dysfunction occurred in two patients with ipsilateral shoulder injuries. The rate of neurovascular complications was comparable to open plating techniques and all patients had full recovery. CONCLUSION: We feel sub-muscular anterior plating of the humerus using locking screw technology is a viable and useful method for diaphyseal humeral fractures.

Demineralized bone matrix for fracture healing: fact or fiction?

Demineralized bone matrix (DBM) has been touted as an excellent grafting material; however, there are no Level I studies that use DBM alone in humans to back up this claim. DBM functions best in a healthy tissue bed but should be expected to have little impact in an anoxic or avascular tissue bed, a situation often encountered in traumatic orthopaedic pathologies. Moreover, there is some evidence of differential potencies of DBM preparations based on donor variability and the manufacturing process. DBM efficacy may also be related to its formulation and the various carriers used. The fact that DBM is an allogeneic material opens up the potential for disease transmission. In addition, DBM activity may be altered by the hormonal status or nicotine use of a patient. In summary, although DBM has proven effective for bone induction in lower form animals, the translation to human clinical use for fracture healing, and the burden of proof, remains.

Biocompatibility of lipid-protein-sugar particles containing bupivacaine in the epineurium.

Novel lipid-protein-sugar particles (LPSPs) are potentially biocompatible because they are composed of naturally occurring ingredients and their expected tissue dwell times are relatively short. In this research, we used histological sections to study tissue reaction to LPSPs (4.4-microm median diameter) when used for sciatic nerve block in the rat. As a reference, we compared LPSPs to 60-microm median diameter poly(lactic-co-glycolic) acid (PLGA) microspheres (110,000 MW PLGA, glycolic/lactic ratio 65:35). Four days after injection, both particle types produced acute inflammation within the confines of the injectate, inflammation in adjacent tissues, and myotoxicity. Bupivacaine-free particles did not display myotoxicity, and inflammation in adjacent tissues was reduced. At 2 weeks, inflammation from LPSPs had almost disappeared, whereas PLGA microspheres had a foreign-body giant cell reaction until at least 8 weeks after injection. In contrast, 3.6-microm median diameter, 20,000-MW PLGA microspheres produced a primarily histiocytic reaction 2 weeks after injection. In summary, the LPSPs and PLGA microspheres studied herein have excellent biocompatibility, but tissue reaction to the former is of much shorter duration. Myotoxicity and inflammation of surrounding tissue is largely attributed to bupivacaine. Foreign-body giant cells may be attributed to particle size rather than a specific reaction to PLGA.