Bench to Bedside – Using research approaches to impact healthcare

The 2011 Wilbert C. Jordan research award recipients are pioneering new, and working with existing, clinical science methodologies to positively impact current and future therapeutic strategies. Review their outstanding work below.

Authors: Ermias Ebebe1 Kim, J P; 1Utturkar, G M; 2Spritzer, C E; 1Moorman, C T; 1Taylor, D C; 1Garrett, W E; +1DeFrate, L E

Title: In Vivo Kinematics in Transtibial and Tibial Tunnel Independent ACL reconstructions

Introduction: The purpose of this study was to compare the abilities of two popular Anterior Cruciate Ligament (ACL) reconstruction techniques to restore native knee motion during weight-bearing flexion in 21 patients with unilateral reconstruction; 12 with transtibial and 10 with independent. We hypothesized that grafts placed using an independent approach previously shown to place the graft anatomically on the femur, will more closely restore the native knee motion throughout the weight-bearing activity.

Methods: All subjects had a healthy contralateral knee. Each underwent MR imaging of both their injured knee and intact knee at 3T. MR images were acquired using a double-echo steady state sequence. The bony contours of each subject’s knee, ACL on the healthy knee, and tunnel on the reconstructed knee were outlined within each MR image. These outlines were then used to make 3D models. Next, the subjects were imaged using two orthogonally placed fluoroscopes while they performed a single leg lunge from 0° to 90° of flexion. These images used to reproduce the in vivo motion of the each subject’s operative and non-op knee. From these models, the knee motions (tibio-femoral knee kinemactis) were recorded. The Anterior-posterior and medial-lateral translations, and internal-external rotations the non-operative knees were measured and compared to the operative knees in all patients between 0° and 90° of flexion. All data were reported as a difference relative to native knee, and compared using the Mann-Whitney U test.

Results: The results demonstrate those with transtibial reconstructions on average had up to 3.97 mm maximal anterior translation, 1.2 mm medial translation and 3 internal rotation of operative tibia relative to their own native knee.

Conclusion: Those with independent reconstruction had less than 0.33 mm anterior, and 0.53 mm medial translation as well near native rotation compared their controls. Overall, knees reconstructed using an independent technique more closely reproduce native knee kinematics.

Senyene Hunter

Title: DNA Double Strand Break Repair in Human Mitochondrial Extracts

Introduction: Double strand break (DSB) repair is essential for the maintenance of mitochondrial DNA (mtDNA) integrity in yeast and is expected to play a similar role in animal mtDNA. We are investigating human mitochondrial DSB repair. MtDNA is prone to DSBs; however the nature of its repair in human cells is not well understood.

Methods: To analyze the presence and potential repair of DSBs in mtDNA we developed a highly sensitive, quantitative PCR-based assay.

Results: Using this assay, we demonstrated that highly purified mitoplast protein extracts execute DSB repair. DNA containing 5’ or 3’ overhangs is repaired more efficiently than blunt-ended DNA (13%, 8% and 3% repaired, respectively). Further investigation of the rejoining of PstI-generated DSBs showed appreciable DNA processing, resulting in the loss of ~50 bases surrounding the PstI site. Sequence analysis of over 100 ligation products revealed several patterns of repaired DNA, most with deletions spanning 4-7 bp direct repeats.

Conclusions: These DNA deletions are strikingly similar to those observed in patients with mitochondrial disorders and certain cancers; suggesting that these clinical syndromes may be associated with DSB repair. We have created a model of DSB repair in which broken DNA is resected to reveal regions of microhomology, allowing annealing and ligation. We show that the 3’ to 5’ exonuclease activity of DNA polymerase gamma is necessary for the efficient repair of DSBs. Additionally, we propose that hSNM1B is the exonuclease responsible for the 5’ to 3’ resection. hSNM1B has a predicted mitochondrial targeting sequence (MTS) with a putative cleavage site of 70 amino acids. Using immunofluorescence, we have shown that hSNM1B-GFP is targeted to mitochondria. Furthermore, the hSNM1B MTS is both necessary and sufficient for mitochondrial localization. Investigating mammalian mitochondrial DSBs and their potential repair may help to develop an understanding of diseases involving mtDNA damage and their possible treatments.

Pachida Lo, MD(c)

Department of General Surgery, Stanford University, 490 S. California Avenue, Palo Alto, CA 94306

Title: Involvement of traditional healers to increase hepatitis B and liver cancer prevention among the Hmong

Introduction: The Hmong population is disproportionately affected by chronic hepatitis B (HBV) infection, the major risk factor for liver cancer. Hmong are also culturally and linguistically isolated from the rest of the country with most preferring healthcare from a Hmong traditional healer, who have not always endorsed Western medicine.

Purpose: To determine the hepatitis B and liver cancer knowledge, attitude and practices among Hmong traditional healers; and, specifically to determine the possibility of engaging traditional healers in increasing HBV and liver cancer prevention awareness in this population.

Methods: In this study, semi-structured in-depth interviews and surveys were conducted to explore the current HBV knowledge, attitude and practices among Hmong traditional healers.

Results: The sample consisted of 30 Hmong traditionalhealers with a mean age of 46 years, and low baseline knowledge of HBV & liver cancer. Most believed western medicine would be the most effective way to treat HBV and liver cancer because these were physical ailments not treatable by Hmong traditional medicine.

Majority had not been screened (63%) or vaccinated for HBV (71%), citing factors

including poor knowledge of HBV and low access to HBV vaccination and screening sites. Traditional healers trained in culturally tailored HBV and liver cancer education exhibited increased knowledge post-training versus pre-training knowledge scores (86% vs. 43%; P<.001). Majority (93%) expressed eagerness to educate clients after receiving training.

Conclusion: This study suggests that Hmong traditional healers are receptive to western medicine preventative practices concerning hepatitis B and liver cancer. These findings have led to the development of a culturally appropriate lay-health-worker program of Hmong traditional healers to increase hepatitis B and liver cancer prevention, and may provide the basis of integrating Hmong traditional healers into other Western diseases prevention efforts.

Filed Under: Scientific Focus

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About the Author: publications@snma.org

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