Meniscal allograft arthroplasty for the treatment of trapeziometacarpal arthritis of the thumb.

BACKGROUND: Arthritis at the trapeziometacarpal joint of the thumb is common. Several surgical options exist showing favorable results. We report the outcomes after interposition of allograft knee meniscus for thumb trapeziometacarpal arthritis. METHODS: Twenty-three patients (25 thumbs) had surgery for thumb trapeziometacarpal arthritis using knee meniscal allograft tissue. Eleven thumbs had a minimum follow-up of 24 months, 2 thumbs had a minimum of 12 months, and 12 thumbs had less than 6 months. Disabilities of arm, shoulder, and hand (DASH) questionnaire scores, pain levels, grip strength, pinch strength, range of motion, and radiographic measurements were performed. RESULTS: Between the preoperative and 24-month follow-up measurements, patient pain levels were reduced. There was a significant improvement in DASH scores. Comparisons between preoperative and postoperative strength measurements showed increase in grip strength and key pinch strength. Trapeziometacarpal subsidence was 5.5 %, and subluxation index measurements decreased 3.9 %. There was no clinical or radiographic evidence of foreign body reaction and no other complications occurred. CONCLUSIONS: The results of meniscal allograft arthroplasty are comparable to other surgical techniques for trapeziometacarpal arthritis with respect to pain, outcomes, strength, oppositional motion, complications, surgical time, cost, and return to work. The results suggest that meniscal allograft arthroplasty is a viable option in the surgical management of stages II and III arthritis of the TM joint. Further follow-up and clinical studies are warranted.

Phospholipid-induced in vivo particle migration to enhance pulmonary deposition.

Amount of drug actually reaching the target region in the lung following pulmonary inhalation is often estimated at less than 10% for older devices. Current particle and device engineering technologies have improved on this but still fail to recover the "wasted" fraction of the drug and deliver it deeper into the lungs, which is generally desirable. FDA has approved several exogenous surfactants for prophylaxis and rescue treatment of respiratory distress syndrome (RDS). Their approved mode of administration (intratracheal instillation) and site of action (alveolar spaces) suggest that the phospholipids in the exogenous surfactants can spread from the trachea to alveolar air spaces and exert advantageous effects. We investigated whether in vivo lung migration of particles based on this phenomenon was possible and could be quantified based on changes in total and regional deposition of fluorescently labeled latex beads, utilized as an insoluble drug model. Following intranasal administration of beads, migration to rodent lungs was monitored upon intranasal instillation of Survanta (exogenous surfactant) or saline (control). After intranasal instillation approximately 12% of beads were found to migrate to the lung, and total lung deposition increased by approximately 10% on administration of Survanta or saline (control). After intranasal administration approximately 1% of beads in the lung were found to migrate to peripheral regions of the lungs, and a four- to six-fold increase in peripheral lung deposition was observed after Survanta instillation, compared to the saline control, which was determined to be independent of dose and volume of Survanta instillate in the range we studied. The in vivo rodent studies provided support for the idea that intranasally administered particles deposited in non-target lung locations may be translocated to peripheral sites in the lung therapeutically after surfactant application.

Inhibition of protein-protein interactions with low molecular weight compounds.

An overview of issues associated with the design and development of low molecular weight inhibitors of protein-protein interactions is presented. Areas discussed include information on the nature of protein-protein interfaces, methods to characterize those interfaces and methods by which that information is applied towards ligand identification and design. Specific examples of the strategy for the identification of inhibitors of protein-protein interactions involving the proteins p56lck kinase, ERK2 and the calcium-binding protein S100B are presented. Physical characterization of the inhibitors identified in those studies shows them to have drug-like and lead-like properties, indicating their potential to be developed into therapeutic agents.

The effect of local corticosteroid or ketorolac exposure on histologic and biomechanical properties of rabbit tendon and cartilage.

Tendonitis, tenosynovitis, and the arthritides are clinical problems commonly encountered in daily orthopaedic practice. Systemic anti-inflammatories, physical therapy, and local corticosteroid injections all are used as nonoperative treatments of these conditions. Systemic anti-inflammatory agents and local corticosteroid agents, however, can be associated with adverse effects that render them intolerable to some patients. As a preliminary study assessing the feasibility of local injection of nonsteroidal anti-inflammatory medication, the histological and biomechanical effects of local exposure of rabbit cartilage and tendon to injectable steroidal (corticosteroid) and injectable nonsteroidal anti-inflammatory agents (ketorolac tromethamine, KT) were determined. Thirty rabbits underwent bilateral knee joint, patellar tendon, and Achilles tendon injections with either normal saline, corticosteroid, or KT. Mechanical and histologic evaluation of the tissues was performed at 6 and 15 weeks after injection. Gross tendon adhesions were observed in more corticosteroid-treated specimens than those exposed to normal saline or KT. Microscopic evaluation of tendons revealed no significant differences among the three groups. Mild cartilage degenerative changes were noted across all groups. Evidence of cartilage necrosis was noted for the corticosteroid-treated group only. Tendons exposed to corticosteroid or KT demonstrated increased load and energy to failure, but exhibited no difference in material stiffness or strain. The use of an injectable nonsteroidal anti-inflammatory agent may be safe and even pose less threat to local tissues after intra-articular and peri-tendinous administration.

cAMP-Coupled riboflavin trafficking in placental trophoblasts: a dynamic and ordered process.

Riboflavin (RF, vitamin B(2)), an essential micronutrient central to cellular metabolism through formation of flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) cofactors, is internalized, at least in part, via a proposed receptor-mediated endocytic (RME) process. The purpose of this study was to delineate the cellular RF distribution using human placental trophoblasts and evaluate the regulatory role of cAMP in this process. Subcellular fractionation and three-dimensional confocal microscopy analyses were carried out to define the RF accumulation profile. Biochemical assays evaluating the cAMP dependence of this pathway were also performed. This study records an intracellular RF distribution pattern that shows dynamic accumulation of the ligand predominantly in the endosomal and lysosomal compartments and to a lesser extent in the Golgi and mitochondria. In contrast, transferrin (TF) colocalizes rapidly within endosomes with minimal accumulation in the other organelles. The temporal and spatial distribution of RF and TF colocalized with unique markers of the endocytic machinery provides added morphological evidence in support of the RME process with ultimate translocation to the mitochondrial domain. Colocalized staining with the Golgi also suggests a possible recycling or exocytic mechanism for this ligand. Furthermore, this study demonstrates cAMP regulation of the putative ligand-bound RF receptor and its association into endocytic vesicles. Delineating the dynamics of the process governing cellular RF homeostasis presents an untapped resource that can be further exploited in improving our current understanding of nutritional biology and fetal growth and development, and perhaps in targeting the endogenous system for developing novel therapeutic approaches.

Activation of TRAP/mediator subunit TRAP220/Med1 is regulated by mitogen-activated protein kinase-dependent phosphorylation.

The TRAP/Mediator coactivator complex serves as a molecular bridge between gene-specific activators and RNA polymerase II. TRAP220/Med1 is a key component of TRAP/Mediator that targets the complex to nuclear hormone receptors and other types of activators. We show here that human TRAP220/Med1 is a specific substrate for extracellular signal-regulated kinase (ERK) of the mitogen-activated protein kinase (MAPK) family. We demonstrate that ERK phosphorylates TRAP220/Med1 in vivo at two specific sites: threonine 1032 and threonine 1457. Importantly, we found that ERK phosphorylation significantly increases the stability and half-life of TRAP220/Med1 in vivo and correlates with increased thyroid hormone receptor-dependent transcription. Furthermore, ERK phosphorylates TRAP220/Med1 in a cell cycle-dependent manner, resulting in peak levels of expression during the G(2)/M phase of the cell cycle. ERK phosphorylation of ectopic TRAP220/Med1 also triggered shuttling into the nucleolus, thus suggesting that ERK may regulate TRAP220/Med1 subnuclear localization. Finally, we observed that ERK phosphorylation of TRAP220/Med1 stimulates its intrinsic transcriptional coactivation activity. We propose that ERK-mediated phosphorylation is a regulatory mechanism that controls TRAP220/Med1 expression levels and modulates its functional activity.

A role for mixed lineage kinases in regulating transcription factor CCAAT/enhancer-binding protein-{beta}-dependent gene expression in response to interferon-{gamma}.

Transcription factor CCAAT/enhancer-binding protein-beta (C/EBP-beta) regulates a variety of cellular functions in response to exogenous stimuli. We have reported earlier that C/EBP-beta induces gene transcription through a novel interferon (IFN)-response element called gamma-IFN-activated transcriptional element. We show here that IFN-gamma-induced, C/EBP-beta/gamma-IFN-activated transcriptional element-dependent gene expression is regulated by mixed lineage kinases (MLKs), members of the mitogen-activated protein kinase kinase kinase family. MLK3 appears to activate C/EBP-beta in response to IFN-gamma by a mechanism involving decreased phosphorylation of a specific phosphoacceptor residue, Ser(64), within the transactivation domain. Decreased phosphorylation of Ser(64) was independent of IFN-gamma-stimulated ERK1/2 activation and did not require the ERK phosphorylation site Thr(189) located in regulatory domain 2 of C/EBP-beta. Together these studies provide the first evidence that MLK3 is involved in IFN-gamma signaling and identify a novel mechanism of transcriptional activation by IFN-gamma.

Distinct cell cycle timing requirements for extracellular signal-regulated kinase and phosphoinositide 3-kinase signaling pathways in somatic cell mitosis.

Mitogen-activated protein (MAP) kinase and phosphoinositide 3-kinase (PI3K) pathways are necessary for cell cycle progression into S phase; however the importance of these pathways after the restriction point is poorly understood. In this study, we examined the regulation and function of extracellular signal-regulated kinase (ERK) and PI3K during G(2)/M in synchronized HeLa and NIH 3T3 cells. Phosphorylation and activation of both the MAP kinase kinase/ERK and PI3K/Akt pathways occur in late S and persist until the end of mitosis. Signaling was rapidly reversed by cell-permeable inhibitors, indicating that both pathways are continuously activated and rapidly cycle between active and inactive states during G(2)/M. The serum-dependent behavior of PI3K/Akt versus ERK pathway activation indicates that their mechanisms of regulation differ during G(2)/M. Effects of cell-permeable inhibitors and dominant-negative mutants show that both pathways are needed for mitotic progression. However, inhibiting the PI3K pathway interferes with cdc2 activation, cyclin B1 expression, and mitotic entry, whereas inhibiting the ERK pathway interferes with mitotic entry but has little effect on cdc2 activation and cyclin B1 and retards progression from metaphase to anaphase. Thus, our study provides novel evidence that ERK and PI3K pathways both promote cell cycle progression during G(2)/M but have different regulatory mechanisms and function at distinct times.

MEKK1 plays a critical role in activating the transcription factor C/EBP-beta-dependent gene expression in response to IFN-gamma.

IFN-gamma induces a number of genes to up-regulate cellular responses by using specific transcription factors and the cognate elements. We recently discovered that CCAAT/enhancer-binding protein-beta (C/EBP-beta) induces gene transcription through an IFN-response element called gamma-IFN-activated transcriptional element (GATE). Using mutant cells, chemical inhibitors, and specific dominant negative inhibitors, we show that induction of GATE-driven gene expression depends on MEK1 (mitogen-activated protein kinase kinase/extracellular signal-regulated protein kinase kinase) and ERKs (extracellular signal-regulated protein kinases) but is independent of Raf-1. Interestingly in cells lacking the MEKK1 gene or expressing the dominant negative MEKK1, ERK activation, and GATE dependent gene expression is inhibited. A dominant negative MEKK1 blocks C/EBP-beta-driven gene expression stimulated by IFN-gamma. These studies describe an IFN-gamma-stimulated pathway that involves MEKK1-MEK1-ERK1/2 kinases to regulate C/EBP-beta-dependent gene expression.