Monica Wiig

Hyaluronan in flexor tendon repair.

This study assesses the effect of a preparation of hyaluronan (hyaluronic acid) applied topically at the time of flexor tendon repair in a well-established model. The hypothesis is that hyaluronic acid applied topically at the time of flexor tendon repair will decrease adhesions, and will improve clinically the gliding function of the repaired flexor tendon. After transection and repair of the second and fifth flexor tendons of the left forepaw of four mongrel dogs, the second flexor tendon was treated with hyaluronic acid of molecular weight 3.6 x 10(6) daltons applied topically between the synovial sheath and the repair site. The left forepaws were completely immobilized for 5 weeks to optimize the formation of adhesion ingrowth. After death, the repaired tendons and sheaths were removed en bloc, fixed, and dissected. Gross inspection and histologic evaluation of all tendons showed that the quality and quantity of adhesions from the wound repair to the synovial sheath appeared to have been consistently affected by hyaluronan. Hyaluronic acid had a beneficial effect on both the repair site and synovial sheath by decreasing the peripheral inflammatory response and promoting a contact healing process via epitenon and endotenon cell involvement in the repair process.

Tendon repair-cellular activities in rabbit deep flexor tendons and surrounding synovial sheaths and the effects of hyaluronan : An experimental study in vivo and in vitro

One deep flexor tendon and its surrounding sheath of each hindpaw of 48 rabbits were transected and repaired in order to investigate the abilities of rabbit flexor tendons and synovial sheaths to synthesize DNA and matrix components during healing and to study the effects of hyaluronan (HA). After repair, HA or saline was injected between the tendon and the sheath. Short-term culture and labeling in vitro were used up to 6 weeks after surgery to determine synthesis of DNA, proteoglycan, collagen, and noncollagen protein. Within tendon repair sites, the rate of cell proliferation increased and reached a maximum 5 days after surgery; within repaired synovial sheaths, the rate immediately decreased. In the healing tendons, the rate of collagen synthesis decreased and the rate of noncollagen protein synthesis remained unchanged. The opposite results were found within the healing synovial sheaths. HA did not affect the rate of cell proliferation or matrix synthesis in healing tendons or surrounding sheaths. These results show that cellular activities differ between tendons and synovial sheaths during healing and that those activities may not be affected by HA.

Effects of hyaluronan on cell proliferation and collagen synthesis: A study of rabbit flexor tendons In vitro

Hyaluronan (HA), a high-molecular-weight polysaccharide, has been suggested to play a possible role during the early stages of healing of a variety of connective tissues and when topically applied to decrease the formation of adhesions following tendon surgery. As the mechanisms of HA actions are still being discussed, this study was designed to assess the effects of HA on cell proliferation and synthesis of matrix components of deep flexor tendons in a well-defined culture system. Cell proliferation, measured as the radioactive 3H-thymidine uptake by cultured segments of rabbit flexor tendons, was inhibited by the addition of HA to the culture medium. HA of molecular weight 0.5 x 10(6) inhibited the uptake significantly at concentrations within the range of 0.1-2.0 mg/mL, HA of molecular weight 1.6 x 10(6) at 0.5-2.0 mg/mL, and HA of molecular weight 3.6 x 10(6) at 1.0-2.0 mg/mL, as compared to matched control groups. At the concentration of 2 mg/mL, HA of the molecular weights of 0.5, 0.8, 1.6, and 3.6 x 10(6) equally inhibited cell proliferation. No effect on synthesis of matrix components, measured as the radioactive incorporation of 35S-sulfate, 3H-hydroxyproline, and 3H-proline by cultured segments of rabbit flexor tendons, was observed. These findings show that exogenously applied HA may act as a modulator of flexor tendon fibroblast proliferation, indicating a possible mechanism for antiadhesive effects following administration after flexor tendon surgery.

Neuropeptide, mast cell and myofibroblast expression after rabbit deep flexor tendon repair

PURPOSEnIncreased numbers of myofibroblasts, mast cells, and neuropeptide-containing nerve fibers have been found in a number of fibrotic processes in connective tissues. The purpose of the present study was to investigate the occurrence of factors implicated in a hypothesized profibrotic neuropeptide-mast cell-myofibroblast pathway in deep flexor tendon healing.nnnMETHODSnIn a rabbit model of flexor tendon injury, with repair of the sharply transected deep flexor tendon using a modified Kessler and a running circumferential peripheral suture, segments of flexor tendons and sheaths were analyzed. The time points chosen-3, 6, 21, and 42 days after tendon repair-represent different stages in tendon healing. The messenger RNA levels of transforming growth factor-β1 and α-smooth muscle actin were measured with conventional reverse transcription-polymerase chain reaction, and the numbers of myofibroblasts, mast cells, and neuropeptide-containing nerve fibers were determined with immunohistochemistry.nnnRESULTSnThe messenger RNA levels for transforming growth factor-β1 and the myofibroblast marker α-smooth muscle actin were significantly increased in deep flexor tendons after injury and repair, at all studied time points, but remained unchanged or even down-regulated in the sheaths. Myofibroblasts, mast cells, and neuropeptide-containing nerve fibers all increased significantly in the healing tendons, exhibiting similar patterns of change in percentages of total cell number over time, reaching levels resembling that of the tendon sheaths with 33% to 50% of the total cell population.nnnCONCLUSIONSnAfter injury to the deep flexor tendon in a rabbit model, the proportion of myofibroblasts, mast cells, and neuropeptide-containing nerve fibers increases significantly. These findings support the hypothesis that the profibrotic neuropeptide-mast cell-myofibroblast pathway is activated in deep flexor tendon healing.

Effect of lactoferrin peptide (PXL01) on rabbit digit mobility after flexor tendon repair.

PURPOSEnRestoration of digital function after flexor tendon injuries remains a clinical challenge. Complications such as adhesion formation and tendon rupture can lead to limited hand function. The aim of this study was to compare the effects of the lactoferrin-derived peptide, PXL01, formulated in sodium hyaluronate (SH), with SH alone on joint mobility as an indirect measure of postsurgical adhesion prevention and healing strength of the tendon and to elucidate the most optimal concentration of PXL01.nnnMETHODSnUsing a rabbit flexor tendon repair model, in which the deep flexor tendon was fully transected and repaired, PXL01 in SH or SH alone was administered between the repaired tendon and the tendon sheath before closure of the surgical wound. Three concentrations of PXL01 in SH (5, 20, or 40 mg/mL) were compared to determine the lowest effective concentration. The repaired tendons were evaluated 7 weeks after surgery by measuring the proximal interphalangeal joint mobility by full range of flexion assessment and the tendon repair strength.nnnRESULTSnTreatment with PXL01 formulated in SH resulted in improved mobility of the proximal interphalangeal joint with an average of 10°, corresponding to improvement of approximately 25% to 60% of the flexion of nonoperated toes at the different measuring points compared with SH alone. The difference was statistically significant in 5 out of 6 measuring points (0.5, 1, 2, 3, and 4 N; P < .05). The dose-response study indicated that the lowest effective concentration of PXL01 was 20 mg/mL. There was no difference in healing strength of the tendon between the groups as assessed by load-to-failure breaking strength.nnnCONCLUSIONSnPXL01 in SH significantly improved the mobility compared with the carrier SH alone, without any negative effect on healing strength, and PXL01 at 20 mg/mL was the lowest effective concentration.nnnCLINICAL RELEVANCEnThe result provides a valuable basis for a clinical trial to assess efficacy and safety of PXL01 in clinical hand surgery.

Division of flexor tendons causes progressive degradation of tendon matrix in rabbits

Deep flexor tendons of 30 rabbits were divided at the ankle level. The effects of unloading on the synthesis and content of matrix components, the synthesis of DNA, and dry weight were investigated. The ability of the tendons to synthesize collagen during short-term culture and the contents of matrix components decreased inversely to the time of unloading. 12 weeks following division, the fibrocartilagnious segments had lost 2/5 of their dry weight, 2/3 of proteoglycan and 1/3 of collagen and non-collagen protein content. Less pronounced losses were observed in the non-fibrocartilaginous segments. A transient increase in cell proliferation in both types of segments was found. These findings indicate that divided flexor tendons undergo a progressive degradation, degradation, which may have implications for delayed suture of deep flexor tendon injuries.

PXL01 in Sodium Hyaluronate for Improvement of Hand Recovery After Flexor Tendon Repair Surgery: Randomized Controlled Trial : Level 1 Evidence

Background: Postoperative adhesions constitute a substantial clinical problem in hand surgery. Fexor tendon injury and repair result in adhesion formation around the tendon, which restricts the gliding function of the tendon, leading to decreased digit mobility and impaired hand recovery. This study evaluated the efficacy and safety of the peptide PXL01 in preventing adhesions, and correspondingly improving hand function, in flexor tendon repair surgery. Methods: This prospective, randomised, double-blind trial included 138 patients admitted for flexor tendon repair surgery. PXL01 in carrier sodium hyaluronate or placebo was administered around the repaired tendon. Efficacy was assessed by total active motion of the injured finger, tip-to-crease distance, sensory function, tenolysis rate and grip strength, and safety parameters were followed, for 12 months post-surgery. Results: The most pronounced difference between the treatment groups was observed at 6 months post-surgery. At this timepoint, the total active motion of the distal finger joint was improved in the PXL01 group (60 vs. 41 degrees for PXL01 vs. placebo group, p = 0.016 in PPAS). The proportion of patients with excellent/good digit mobility was higher in the PXL01 group (61% vs. 38%, p = 0.0499 in PPAS). Consistently, the PXL01 group presented improved tip-to-crease distance (5.0 vs. 15.5 mm for PXL01 vs. placebo group, p = 0.048 in PPAS). Sensory evaluation showed that more patients in the PXL01 group felt the thinnest monofilaments (FAS: 74% vs. 35%, p = 0.021; PPAS: 76% vs. 35%, p = 0.016). At 12 months post-surgery, more patients in the placebo group were considered to benefit from tenolysis (30% vs. 12%, p = 0.086 in PPAS). The treatment was safe, well tolerated, and did not increase the rate of tendon rupture. Conclusions: Treatment with PXL01 in sodium hyaluronate improves hand recovery after flexor tendon repair surgery. Further clinical trials are warranted to determine the most efficient dose and health economic benefits. Trial Registration: ClinicalTrials.gov NCT01022242; EU Clinical Trials 2009-012703-25. Citation: Wiig ME, Dahlin LB, Fridén J, Hagberg L, Larsen SE, et al. (2014) PXL01 in Sodium Hyaluronate for Improvement of Hand Recovery after Flexor Tendon Repair Surgery: Randomized Controlled Trial. PLoS ONE 9(10): e110735. doi:10.1371/journal.pone.0110735 Editor: Alberto G. Passi, University of Insubria, Italy Received April 13, 2014; Accepted September 15, 2014; Published October 23, 2014 Copyright: 2014 Wiig et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability: The authors confirm that all data underlying the findings are fully available without restriction. The data is presented in the body of the paper and in the Supporting Information files, and deposited to public databases (EudraCT: 2009-012703-25, ClinicalTrials.gov: NCT01022242). Funding: The study was financed by Pergamum AB. M. Mahlapuu is CSO of Pergamum, PhD. The funder provided support in the form of salary for author MM, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific role of this author is articulated in the ’author contributions’ section. Dr. K. Wiklund is employed by Pharma Consulting Group Solutions AB. Pharma Consulting Group Solutions AB provided support in the form of salary for author KW, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific role of this author is articulated in the ’author contributions’ section. Competing Interests: The authors have read the journal’s policy and the following conflicts have been identified: Dr. M. Mahlapuu was employed by Pergamum AB, Dr. M. Wiig has received honorariums and held advisory board positions for Pergamum AB. The study was financed by Pergamum AB. Dr. K. Wiklund is employed by Pharma Consulting Group Solutions AB. There are no patents, products in development or marketed products to declare. This does not alter the authors’ adherence to all the PLoS ONE policies on sharing data and materials. * Email: monica.wiig@akademiska.se