Critical aspects of tissue-engineered therapy for bone regeneration.

Recent advances in bone tissue engineering are established on the understanding of an engineered scaffold, the molecular milieu within the osteogenic site, and the cell(s) predisposed to an osteogenic lineage. Advances in the incorporation of a generative vehicle into a skeletal defect require temporal and spatial distribution of the scaffold, growth factor, and cell compatible with enhanced bone healing. Monitoring events culminating in osteogenesis has focused on phenotypic and intracellular indicators. Phenotypic and intracellular indicators include the presence of receptors and intracellular signals that enable cell proliferation and differentiation. Progress in the areas of scaffold design, growth factor utilization, bone cell lineage, and intracellular signaling are reviewed.

Establishing an immortalized human osteoprecursor cell line: OPC1.

The present studies evaluated the feasibility of establishing a conditionally immortalized osteoprecursor cell line derived from human fetal bone tissue. Primary cultures were transfected with a plasmid in which the Mx-1 promoter drives the expression of SV40 T-antigen when activated by human A/D interferon. Several neomycin (G418)-resistant colonies were characterized for cell growth and alkaline phosphatase (ALP) enzyme activity. The clone, designated OPC1 (osteoblastic precursor cell line 1), which exhibited the highest ALP enzyme activity at passage 10 (P10), was selected for additional osteogenic phenotypic characterization. Reverse transcription-polymerase chain reaction (RT-PCR) phenotyping revealed abundant mRNA for osteocalcin (OC), osteonectin (ON), osteopontin (OP), parathyroid hormone receptor (PTHr), ALP, and procollagen type I (ProI). In addition, the levels of quantitative RT-PCR product of ON, OP, PTHr, and ProI mRNAs exhibited a marked up-regulation when maintained in medium containing an osteogenic supplement (OS). The ability to stimulate osteogenic differentiation was characterized in postconfluent OPC1 cells maintained in tissue culture medium supplemented with recombinant human bone morphogenetic protein-2 (rhBMP-2) either with or without an OS. All treatment groups exhibited a striking up-regulation of ALP enzyme activity that coincided with ALP histochemical observations. Postconfluent cells also exhibited the ability to form mineralized nodules under all treatments (confirmed by von Kossa histochemical staining and calcium deposition). An enzyme immunosorbent assay (EIA) was utilized to measure intact human OC from the OPC1 line under the various treatments. Abundant OC was evident in the tissue culture medium indicating de novo sythesis and release from the OPC1 line under appropriate conditions. The clonal human-derived OPC1 line represents a homogeneous osteogenic cell line that not only has maintained a consistent bone phenotype from P10 to at least P30, but has also exhibited the capacity to generate programmed differentiation in the presence of low dose rhBMP-2 (10 ng/ml). Thus, the OPC1 line is a human-derived osteoprecursor that provides a sensitive in vitro cell culture system to evaluate bone development, cell/biomaterial interactions, and may be a useful screen for putative bone differentiating factors.

Maxillary alveolar cleft repair in dogs using recombinant human bone morphogenetic protein-2 and a polymer carrier.

Recombinant human bone morphogenetic protein-2 was evaluated in maxillary alveolar clefts in 24 adult, skeletally mature Foxhound dogs. Bilateral clefts were prepared, 1 cm in bony width, lined with healthy epithelium with functional teeth on each side, and were expected not to heal spontaneously with new bone. Preparation of bilateral clefts in 24 dogs permitted 48 recipient sites divided evenly among four treatment and two time periods (2 and 4 months), yielding six replicates per treatment per time. The overall goal for the study was to regenerate bone in the cleft using one of three treatments: (2) 200 microgram recombinant human bone morphogenetic protein-2 combined with the copolymer poly(lactide-co-glycolide) and autogenous blood, (2) poly(lactide-co-glycolide) and autogenous blood, or (3) an autograft from the posterior iliac crest. A fourth group consisted of untreated alveolar cleft defects. At designated times, dogs were euthanized, and the recipient beds with contiguous bone were recovered, processed, and assessed radiographically and histologically. Autograft-treated defects had more bone than other treatments at 2 months; however, by 4 months, there were no differences among treatments, except for the poly(lactide-co-glycolide) group, which had the least amount of bone. Response to the recombinant human bone morphogenetic protein-2 may have been suboptimal either because the dose was too low or because the poly(lactide-co-glycolide)-autogenous blood delivery system did not temporally maintain and spatially position recombinant human bone morphogenetic protein-2 at the recipient bed. In addition, the development of a nonhealing, critical-sized defect in the maxilla of the dog appears to require a more aggressive resection of bone to preclude spontaneous osseous regeneration.

Transcutaneous electrical nerve stimulation after cesarean birth.

The purpose of this study was to determine if women who had Cesarean birth experiences and used transcutaneous electrical nerve stimulation as a means of pain control requested less pain medication and had shorter hospital stays than those who did not use TENS. I reviewed the medical charts of 72 women (46 using TENS, 26 not using TENS) retrospectively. Significantly less (F = 5.77; df = 1,65; p less than .02) meperidine hydrochloride was administered to the women who used TENS. The length of hospital stay of women using TENS was not significantly different than those who did not use TENS. My findings suggest that the use of TENS after Cesarean birth may result in decreased usage of medication and, therefore, a reduction of the side effects of the medication both to the mother and the infant.