Zhao, Chunfeng

ABSTRACTFibrosis of the subsynovial connective tissue (SSCT) is a predominant feature of carpal tunnel syndrome (CTS). While the nature of CTS has been extensively studied, little is known about the etiology of this disease. We investigated SSCT tissue from patients with CTS and control subjects using fibrosis arrays and cell culture analysis. Twofold changes in fibrotic gene expression were found in multiple genes from patient SSCT using fibrosis arrays. This data was confirmed via qRT‐PCR on a subset of genes; collagen I (Col1), collagen III (Col3), connective tissue growth factor (CTGF), transforming growth factor β (TGF‐β), and SMAD3 (P < 0.05) which significantly corroborate the fold changes found in the fibrosis arrays. To further explore the nature of SSCT fibrosis, cells were isolated from patient and control tissue. Col1, Col3, TGF‐β, and SMAD3 were highly expressed in patient SSCT fibroblasts as compared to control (P < 0.05). Further, fibrotic genes expression was decreased by inhibiting TGF‐β receptor I (TβRI) activity (P < 0.05). TGF‐β second messenger SMAD activity was significantly activated in SSCT fibroblasts from patients and this activation was abrogated by inhibiting TβRI signaling (P < 0.05). These findings suggest that blocking TGF‐β signaling may be an important therapeutic approach to treating the underlying fibrosis of SSCT in CTS patients. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:1444–1450, 2014.

AbstractNoninflammatory subsynovial connective tissue (SSCT) fibrosis with nerve compression is a prominent feature of carpal tunnel syndrome (CTS). Studies have shown that SSCT matrix synthesis and material property changes in CTS are associated with increased activity of transforming growth factor (TGF)‐β1. The aim of this study were to (1) investigate the ability of SSCT fibroblasts from CTS patients and unaffected individuals to contract a collagen gel ring and (2) determine how the addition of TGF‐β1 affects this ability. SSCT fibroblasts from three normal cadavers and three age‐matched female patients who had undergone surgery for CTS were used. Results showed patient cell‐seeded gels had a significantly higher contraction rate (p < 0.001) than control cells, and fully contracted gel rings possessed a significantly higher tensile strength (p = 0.003) and stiffness (p < 0.001). Furthermore, TGF‐β1 significantly intensified contraction rate (p < 0.001), tensile strength (p < 0.001), and stiffness (p < 0.001). In conclusion, SSCT cells from normal donors and CTS patients contract collagen gel rings differently, and this ability is affected by TGF‐β1 treatment. This cell‐seeded collagen gel model may be useful for developing new methods of stopping or eliminating the effect of TGF‐β1 on the SSCT fibroblasts and surrounding matrix, which might aid in the identification of medical treatment for CTS. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103A: 574–580, 2015.

Background This study investigated the effects of a series of four hypertonic dextrose injections on the subsynovial connective tissue (SSCT) and median nerve within the carpal tunnel of a rabbit model. Methods Twenty New Zealand white rabbits were used. One forepaw carpal tunnel was randomly injected with 0.1 ml of 10 % dextrose solution. The contralateral forepaw was injected with a similar amount of saline. This injection was made once per week for 4 weeks. The animals were killed at 16 weeks after the initial injection and were evaluated by electrophysiology (EP), SSCT mechanical testing, and histology. Results Mechanical testing revealed significantly greater ultimate load and energy absorption in the dextrose injection group compared to the saline injection group ( P<0.05). Histological evaluation revealed SSCT fibrosis and thickening and edema in the median nerve bundles in the dextrose injection group. There was a prolongation in the latency of the EP test in the dextrose injection group ( P=0.08). Conclusions Previous studies had shown that one or two injections of 10 % dextrose could induce moderate SSCT fibrosis and mild EP changes without nerve histology changes. In this study, we have shown that higher doses create more severe fibrosis and, most importantly, more severe neuropathy, suggesting a dose–response effect, and confirming this as a potentially useful animal model for researching the etiology and treatment of carpal tunnel syndrome.

SUMMARYFibrosis of the subsynovial connective tissue (SSCT) in the carpal tunnel is the most common histological finding in carpal tunnel syndrome (CTS). Fibrosis may result from damaged SSCT. Previous studies found that with low‐velocity (2 mm/s), tendon excursions can irreversibly damage the SSCT. We investigated the effect of tendon excursion velocity in the generation of SSCT damage. Nine human cadaver wrists were used. Three repeated cycles of ramp‐stretch testing were performed simulating 40%, 60%, 90%, and 120% of the middle finger flexor tendon superficialis physiological excursion with an excursion velocity of 60 mm/s. Energy and force were calculated and normalized by values obtained in the first cycle for each excursion level. Data were compared with low‐velocity excursion data. For high‐velocity excursions, a significant drop in the excursion energy ratio was first observed at an excursion level of 60% physiological excursion (p < 0.024) and that for low‐velocity excursions was first observed at 90% physiological excursion (p < 0.038). Furthermore, the energy ratio was lower at 60% for high velocities (p ≤ 0.039). Increasing velocity lowers the SSCT damage threshold. This finding may be relevant for understanding the pathogenesis of SSCT fibrosis, such as that accompanying CTS, and a relationship with occupational factors. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:123–128, 2014.

ABSTRACTNon‐inflammatory fibrosis of the subsynovial connective tissue (SSCT) is a hallmark of carpal tunnel syndrome (CTS). The etiology of this finding and its relationship to the development of CTS remain poorly understood. Recent studies have found that transforming growth factor‐β (TGF‐β) plays a central role in fibrosis. The purpose of this study was to investigate the expression of TGF‐β and connective tissue growth factor (CTGF), a downstream mediator of TGF‐β, in the pathogenesis of CTS. We compared SSCT specimens from 26 idiopathic CTS patients with specimens from 10 human cadaver controls with no previous diagnosis of CTS. Immunohistochemistry was performed to determine levels TGF‐β1, CTGF, collagen 1(Col1) and collagen 3 (Col3) expression. TGF‐β1 (p < 0.01), CTGF (p < 0.01), and Col3 (p < 0.01) were increased in SSCT of CTS patients compared with control tissue. In addition, a strong positive correlation was found between TGF‐β1 and CTGF, (R2 = 0.80, p < 0.01) and a moderate positive correlation between Col3 and TGF‐β1 (R2 = 0.49, p < 0.01). These finding suggest that there is an increased expression of TGF‐β and CTGF, a TGF‐β regulated protein, and that this TGF‐β activation may be responsible for SSCT fibrosis in CTS patients. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:116–122, 2014.

AbstractTendon‐to‐bone integration is a great challenge for tendon or ligament reconstruction regardless of use of autograft or allograft tendons. We mineralized the tendon, thus transforming the tendon‐to‐bone into a “bone‐to‐bone” interface for healing. Sixty dog flexor digitorum profundus (FDP) tendons were divided randomly into five groups: (1) normal FDP tendon, (2) CaP (non‐extraction and mineralization without fetuin), (3) CaPEXT (Extraction by Na2HPO4 and mineralization without fetuin), (4) CaPFetuin (non‐extraction and mineralization with fetuin), and (5) CaPEXTFetuin (extraction and mineralization with fetuin). The calcium and phosphate content significantly increased in tendons treated with combination of extraction and fetuin compared to the other treatments. Histology also revealed a dense mineral deposition throughout the tendon outer layers and penetrated into the tendon to a depth of 200 µm in a graded manner. Compressive moduli were significantly lower in the four mineralized groups compared with normal control group. No significant differences in maximum failure strength or stiffness were found in the suture pull‐out test among all groups. Mineralization of tendon alters the interface from tendon to bone into mineralized tendon to bone, which may facilitate tendon‐to‐bone junction healing following tendon or ligament reconstruction. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31:1713–1719, 2013

ABSTRACTWe compared the mechanical force of tendon‐to‐bone repair techniques for flexor tendon reconstruction. Thirty‐six flexor digitorum profundus (FDP) tendons were divided into three groups based upon the repair technique: (1) suture/button repair using FDP tendon (Pullout button group), (2) suture bony anchor using FDP tendon (Suture anchor group), and (3) suture/button repair using FDP tendon with its bony attachment preserved (Bony attachment group). The repair failure force and stiffness were measured. The mean load to failure and stiffness in the bony attachment group were significantly higher than that in the pullout button and suture anchor groups. No significant difference was found in failure force and stiffness between the pullout button and suture anchor groups. An intrasynovial flexor tendon graft with its bony attachment has significantly improved tensile properties at the distal repair site when compared with a typical tendon‐to‐bone attachment with a button or suture anchor. The improvement in the tensile properties at the repair site may facilitate postoperative rehabilitation and reduce the risk of graft rupture. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31:1720–1724, 2013

Background We have recently reported that interpositional synovium grafts from tendon sheath have a potential to accelerate tendon healing when implanted at the repair site. The purpose of this study was to investigate the effect of orientation of the synovium after synovium graft transplantation, by comparing the ability of cells from the visceral and parietal surfaces to migrate into the tendon in a canine tissue culture model. Methods The synovium graft was placed within a complete tendon laceration, with either the visceral or parietal surface facing the proximal end of the lacerated tendon. The number of migrating cells was quantified by a cell migration assay. Qualitative immunohistochemistry and confocal laser microscopy were also used at day 10. Results Many labeled synovial cells were observed within the tendon to which the visceral surface of the synovium graft was facing. Migrated cells were also observed on the parietal side, but there were fewer cells compared to visceral surface cells. Migrating cells all expressed α-smooth muscle actin. Conclusion We found that graft orientation affected cell migration. Whether this finding has clinical significance awaits in vivo study.

The purpose of this study was to compare two different methods of joining tendons of similar and dissimilar sizes between recipient and donor tendons for flexor tendon grafts. Flexor digitorum profundus (FDP) and peroneus longus (PL) canine tendons were harvested and divided into four groups. The repair technique we compared was a step-cut (SC) suture and a Pulvertaft weave (PW). FDP tendons were significantly larger in diameter than PL tendons ( p < 0.05). The volume of the SC repairs using either FDP or PL tendon as a graft was significantly smaller than PW repairs ( p < 0.05). The ultimate load to failure and repair stiffness in FDP graft tendons significantly increased compared with the PL graft tendons ( p < 0.05). The SC suture can be used as an alternative to the PW, with similar strength and less bulk for repairs using graft tendons of similar diameter. Surgeons should be aware of the effect of graft tendon size and repair method on strength and bulk when performing flexor tendon grafts.