Healing and Normal Fibroblasts Exhibit Differential Proliferation, Collagen Production, α-SMA Expression, and Contraction

Smad4 Loss in the Mouse Intestinal Epithelium Alleviates the Pathological Fibrotic Response to Injury in the Colon

Mucosal healing is associated with better clinical outcomes in patients with inflammatory bowel diseases (IBDs). Unresolved injury and inflammation, on the other hand, increases pathological fibrosis and the predisposition to cancer. Loss of Smad4, a tumor suppressor, is known to increase colitis-associated cancer in mouse models of chronic IBD. Since common biological processes are involved in both injury repair and tumor growth, we sought to investigate the effect of Smad4 loss on the response to epithelial injury. To this end, Smad4 was knocked out specifically in the intestinal epithelium and transcriptomic and morphological changes compared between wild type mice and Smad4 knock out mice after DSS-induced injury. We find that Smad4 loss alleviates pathological fibrosis and enhances mucosal repair. The transcriptomic changes specific to epithelium indicate molecular changes that affect epithelial extracellular matrix (ECM) and promote enhanced mucosal repair. These findings suggest that the biological processes that promote wound healing alleviate the pathological fibrotic response to DSS. Therefore, these mucosal repair processes could be exploited to develop therapies that promote normal wound healing and prevent fibrosis.

NEW AND NOTEWORTHY

We show that transcriptomic changes due to Smad4 loss in the colonic epithelium alleviates the pathological fibrotic response to DSS in an IBD mouse model of acute inflammation. Most notably, we find that collagen deposition in the epithelial ECM, as opposed to that in the lamina propria, correlates with epithelial changes that enhance wound healing. This is the first report on a mouse model providing alleviated fibrotic response in a DSS-IBD mouse model in vivo .

A tetramethylpyrazine-loaded hyaluronic acid-based hydrogel modulates macrophage polarization for promoting wound recovery in diabetic mice

The failure of wound healing often causes lower limb disability and amputation of diabetic patients. Current strategies for diabetic wound management often fail to achieve the expected outcomes, and emerging alternatives are urgently needed. Recent advances in the identification of active compounds from traditional herbal medicines provide promising therapeutics for tissue repair and regeneration. In this study, the pro-healing effects of tetramethylpyrazine (TMP, a natural alkaloid found in Ligusticum chuanxiong Hort) for diabetic wounds were for the first time demonstrated. The cutaneous healing was mainly achieved by TMP-mediated macrophage polarization from pro-inflammatory to pro-healing phenotype. In addition, the topical administration of TMP was facilitated by the hyaluronic acid (HA) hydrogel for promoting the full-thickness wounds in the experimental diabetic mice. Consequently, TMP-loaded HA hydrogel (TMP-HA) profoundly accelerated the wound closure in comparison with TMP-loaded INTRASITE Gel (it is a commercial hydrogel), which was evident with the inflammation mitigation, the angiogenesis enhancement, and the collagen deposition. Our work reveals the macrophage-modulatory function of TMP for diabetic wound healing and demonstrates great potential of TMP-HA for clinical application.

Jia-Wei-Si-Miao-Yong-An Fang stimulates the healing of acute radiation-induced cutaneous wounds through MAPK/ERK pathway

ETHNOPHARMACOLOGICAL RELEVANCE

A famous traditional oral Chinese medicine formula, Si-Miao-Yong-An decoction, has been used to treat thromboangiitis obliterans from the Qing Dynasty. Because its therapeutic principles including clearing away heat, detoxification, accelerating blood circulation and relieving pains are consistent with acute radiation-induced cutaneous wounds in traditional Chinese medicine, we tried to add herbs and improve them into an external dosage form, called Jia-Wei-Si-Miao-Yong-An Fang (JWSMYA). However, its mechanism on radiation-induced cutaneous wounds is still unknown.

AIM OF THE STUDY

This study evaluated the therapeutic effect of JWSMYA and investigated the mechanism of repair and anti-fibrosis on acute radiation-induced cutaneous wounds with JWSMYA.

MATERIALS AND METHODS

Firstly, we prepared JWSMYA, and determined the composition through UHPLC LC-MS/MS. Then we used ionizing radiation to make a cutaneous wound model of rats, and observed wound healing through their skin injury score, wound contraction percentage and histological staining. In addition, immunohistochemical staining, Western blot analysis, qRT-PCR and Elisa were used to explore wound rehabilitation and anti-fibrosis mechanisms.

RESULTS

An in vivo assay revealed that JWSMYA promoted the repairment of acute radiation-induced cutaneous wounds, facilitated MAPK/ERK phosphorylation, inhibited PI3K/AKT activation, reduced the level of alpha-smooth muscle actin (a-sma), collagen type-I alpha 2 (Col1a2) and transforming growth factor-beta 1 (TGF-β1) in cutaneous tissues. However, no statistical difference was found in vascular endothelial growth factor (VEGF).

CONCLUSION

JWSMYA accelerated the repair of acute radiation-induced cutaneous wounds, which might be associated with the MAPK/ERK pathway. In addition, PI3K/AKT might be associated with the inhibition of fibrosis and the promotion of high-quality wound healing.

Polyisocyanides as a substrate to trigger vaginal fibroblast functioning in an in vitro model for prolapse repair

Pelvic organ prolapse (POP) is the descent of the bladder, uterus, and/or rectum into the vagina. POP is associated with altered vaginal fibroblast functionality and connective tissue composition in the vaginal wall. The results of surgical intervention are poor, which may be related to the lack of true restoration of the connective tissue. An innovative treatment addresses tissue repair after surgery by the introduction of a bioactive supplement that enhances the healing process through collagen and elastin deposition. As a novel strategy, we first studied the effects in an in vitro model. Here, we investigate how the presence of cell binding GRGDS (RGD) peptides on the highly biomimetic polyisocyanide (PIC) gel facilitates and promotes the function of primary vaginal fibroblasts isolated from a POP patient. Fibroblast function was analyzed in terms of morphology, proliferation, and extracellular matrix (ECM) deposition and remodeling. RGD modification of the gel facilitated cell spread and proliferation. Quantitative outcomes of the ECM content indicated increased production of collagen and elastin by fibroblasts on gels with the highest RGD density. The in vitro results suggest that PIC-RGD hydrogel application may translate into improved connective tissue healing in the pelvic floor, which is essential for its use as a regeneration promoting additive in surgery.

Combination of SDF-1 and bFGF promotes bone marrow stem cell-mediated periodontal ligament regeneration

Stromal cell derived factor-1 (SDF-1) and basic fibroblast growth factor (bFGF) were reported to induce the differentiation of bone marrow stem cells (BMSCs) into cells with characteristics of periodontal ligament fibroblasts. Thus SDF-1 and bFGF may play a positive role in BMSCs-mediated periodontal ligament regeneration. Here, the methylthiazolyldiphenyl tetrazolium bromide (MTT) assay was used to investigate the effect of scaffolds, SDF-1 and bFGF on BMSCs proliferation. RT-PCR and Western blot were used to evaluate gene and protein expression. Beagle dogs were used to establish an animal model of tooth reimplantation and to investigate the effects of scaffolds, BMSCs, SDF-1 and bFGF on periodontal ligament regeneration. X-ray images and micro computed tomography (micro CT) were used to assess morphological changes in replanted teeth and surrounding alveolar bone. H&E staining and Masson's staining were also performed. BMSCs from Beagle dogs growth on scaffolds consisted of dense structured collagens. SDF-1 and bFGF effectively promoted the differentiation of BMSCs into fibroblasts, periodontal membrane reconstruction, and cell proliferation in vitro. SDF-1 and bFGF also stimulated the expression of type I collagen (Col I), type III collagen (Col III), CXC family chemokine receptor 4 (CXCR4), and S100 calcium binding protein A4 (S100A4), and decreased the expression of alkaline phosphatase (ALP). In our experimental Beagle dog model of tooth extraction and replantation, application of SDF-1 and bFGF significantly elevated periodontal membrane reconstruction and thus supported the survival of replanted teeth. In conclusion, the findings from the present study demonstrated that SDF-1 and bFGF enhance the process of periodontal ligament reconstruction, and provide a basis and reference for the use of stem cell tissue engineering in promoting periodontal membrane regeneration.

BMP‑7 suppresses excessive scar formation by activating the BMP‑7/Smad1/5/8 signaling pathway

Scarring is the inevitable consequence of wound repair, which may cause significant physical and mental pain to patients when excessive. Bone morphogenetic protein-7 (BMP-7) has been proved to inhibit TGF-β-induced fibrosis in various tissues including dermal papilla cells. However, the effect of BMP-7 on hypertrophic scarring, a common proliferative disorder of dermal fibroblasts, has not been determined. To overcome this problem, the present study established a mouse model of thermal injury to investigate the inhibitory effects of BMP-7 on scar formation. The histological analysis of scar tissues was performed by H&E and Masson's trichrome staining. Western blot assay was used to determine the level changes of related proteins and TUNEL assay was performed to assess the apoptosis of scar tissues. The results demonstrated that BMP-7 promoted wound healing and inhibited scar formation when compared with untreated mice. Collagen deposition and the expression of fibrotic proteins were suppressed in the scar tissues of mice treated with BMP-7. In addition, BMP-7 induced fibroblast apoptosis in scar tissues. Furthermore, activation of the BMP-7/Smad1/5/8 signaling pathway may have been involved in the inhibitory effects of BMP-7 on scar formation. In conclusion, the results of the present study indicate that BMP-7 may inhibit excessive scar formation via activation of the BMP-7/Smad1/5/8 signaling pathway. The results present a potential alternative therapeutic strategy for the treatment of hypertrophic scarring.

Effect of Botulinum Toxin Type A on TGF-β/Smad Pathway Signaling: Implications for Silicone-Induced Capsule Formation

BACKGROUND

One of the most serious complications of breast surgery using implants is capsular contracture. Several preventive treatments have been introduced; however, the mechanism of capsule formation has not been resolved completely. The authors previously identified negative effects of botulinum toxin type A on capsule formation, expression of transforming growth factor (TGF)-β1, and differentiation of fibroblasts into myofibroblasts. Thus, the authors investigated how to prevent capsule formation by using botulinum toxin type A, particularly by means of TGF-β1 signaling, in human fibroblasts.

METHODS

In vitro, cultured human fibroblasts were treated with TGF-β1 and/or botulinum toxin type A. Expression of collagen, matrix metalloproteinase, and Smad was examined by Western blotting. The activation of matrix metalloproteinase was observed by gelatin zymography. In vivo, the effect of botulinum toxin type A on the phosphorylation of Smad2 in silicone-induced capsule formation was evaluated by immunocytochemistry.

RESULTS

In vitro, the phosphorylation of Smad2 was inhibited by botulinum toxin type A treatment. The expression levels of collagen types 1 and 3 were inhibited by botulinum toxin type A treatment, whereas those of matrix metalloproteinase-2 and matrix metalloproteinase-9 were enhanced. Gelatin zymography experiments confirmed enhanced matrix metalloproteinase-2 activity in collagen degradation. In vivo, botulinum toxin type A treatment reduced capsule thickness and Smad2 phosphorylation in silicone-induced capsules.

CONCLUSION

This study suggests that botulinum toxin type A plays an important role in the inhibition of capsule formation through the TGF-β/Smad signaling pathway.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, V.

Suppressive effects of induced pluripotent stem cell-conditioned medium on in vitro hypertrophic scarring fibroblast activation

Hypertrophic scarring (HS) is a type of fibrosis that occurs in the skin, and is characterized by fibroblast activation and excessive collagen production. However, at present, therapeutic strategies for this condition are ineffective. Previous studies have identified that the mutual regulation of chronic inflammation, mechanical force and fibroblast activation leads to the formation of HS. Induced pluripotent stem cells (iPSCs) are novel bioengineered embryonic-like stem cells, initially created from mouse adult fibroblasts. The current study demonstrated that iPSC-conditioned medium (iPSC-CM) may significantly suppress hypertrophic scar fibroblast activation. It was observed that in the presence of iPSC-CM, the level of collagen I was markedly reduced and α-smooth muscle actin, a marker for myofibroblasts (activated fibroblasts that mediate mechanical force-induced HS formation), exhibited a significantly lower level of expression in human dermal fibroblasts (HDFs) activated with transforming growth factor-β1. Additionally, iPSC-CM attenuated the local inflammatory cell response by blocking the adhesion of human acute monocytic leukemia cell monocytes and fibroblasts in vitro. In addition, the contractile ability of HDFs may be reduced by iPSC-CM. These observations suggest that iPSC-CM may protect against processes leading to hypertrophic scarring by attenuating fibroblast activation, blocking inflammatory cell recruitment and adhesion and reducing the contractile ability of fibroblasts.

Mediatory role of interleukin-6 in α smooth muscle actin induction and myofibroblast formation around silicone tissue expander

Materials used for medical devices are usually tested for their biocompatibility, before use. However, it is known that long-term implantation in the body may lead to degradation of the material leading to an adverse tissue response. The failure of silicone breast implants due to excessive fibrosis and contracture has led to studies to delineate the cause of fibrosis around this material. To detect the biological moieties involved, conditioned media from RAW 264.7 macrophages seeded over commercially available silicone tissue expander material was added to L929 fibroblasts. Ultrahigh-molecular-weight polyethylene and tissue culture grade polystyrene served as the control materials. The gene expression of fibrogenic cytokines, interleukin-6 (IL-6), and transforming growth factor beta (TGFβ) in the RAW macrophages and myofibroblast marker alpha smooth muscle actin (αSMA) in L929 cells were quantitated by real time polymerase chain reaction. Protein expression analysis of αSMA was carried out by immunocytochemical staining and confocal microscopy. An in vitro degradation study of silicone expander material in pseudoextracellular fluid (PECF) and the αSMA expression in fibroblasts incubated with the silicone extract containing PECF has revealed the role of silicone leachants in induction of myofibroblasts. This in vitro expression study revealed the additional profibrotic role of IL-6 in fibroblast to myofibroblast transition and the synergy between material aspects and biomolecules in regulating fibrosis around Silicone implants. These findings may help in targeting newer biological moieties in the profibrotic pathway and in devising better manufacturing processes aiding the life of millions of patients.

Thymosin β4 enhances the healing of medial collateral ligament injury in rat

The role played by thymosin β4 (Tβ4) in the process of wound healing was reported in several organs. However, there have been no reports that investigated the role of Tβ4 in the repair process after ligament injury. The purpose of this study was to determine whether administration of Tβ4 would improve ligament repair following injury. The medial collateral ligament (MCL) was sharply transected on the day of surgery. Then, the treatment group received 100 μL of fibrin sealant containing 1 μg of Tβ4 placed in the ligament gap. Healing tissues were evaluated by hematoxylin and eosin stain, transmission electron microscopy, and biomechanical test at 4 weeks after surgery. Histologically, healing tissues in Tβ4-treated group exhibited uniform and evenly spaced fiber bundles. However, the collagen fibers were not evenly spaced in control rats. Moreover, diameters of collagen fibrils within granulation tissue from the Tβ4-treated rats were significantly increased. In Tβ4-treated MCLs, the mechanical properties of these healing tissues were significantly higher at 4 weeks after surgery. In terms of the mechanical properties of the healing femur-medial collateral ligament-tibia complexes, the Tβ4-treated group had significantly better biomechanical properties than the control group at 4 weeks after surgery. Local administration of Tβ4 promotes the healing process of MCL, both histologically and mechanically, in a rat model. These findings provide a basis for potential clinical use of Tβ4 in repairing ligaments.

Cellular senescence occurring in the rabbit medial collateral ligament during healing

Medial collateral ligament (MCL) healing proceeds in a temporally ordered fashion after injury. Despite the critical roles of fibroblasts during ligament repair, the phenotypic features of these healing fibroblasts have not been well characterized. Here, we show that healing MCL fibroblasts obtained from rabbits at 3-week postinjury exhibited higher rates of senescent phenotypes and produced higher levels of TGF-β1, collagens, α-SMA, and matrix metalloproteinases (MMPs), than the corresponding fibroblasts from sham-operated MCLs. Mechanical stretch further enhanced the cellular senescence and the expression of TGF-β1, collagens, α-SMA, and MMPs in both sham and healing MCL fibroblasts. In addition to MCL fibroblasts at 3-week postinjury, the increased cellular senescence was also detected in healing MCL fibroblasts obtained at 4- and 6-week postinjury. Most importantly, the association between the cellular senescence and ligament healing was confirmed in tissue sections by the senescence-associated β-galactosidase (SA-β-gal) staining. Using a recombinant TGF-β1 and a neutralizing antibody, we found that those phenotypic changes, such as cellular senescence and the expression of collagens and MMPs, in MCL fibroblasts under mechanical loading conditions were regulated through TGF-β1. Taken together, our results propose that cellular senescence and turnover of extracellular matrixes regulated by TGF-β1 in MCL fibroblasts are critical for ligament healing.

Carnosine enhances diabetic wound healing in the db/db mouse model of type 2 diabetes

Diabetes mellitus (DM) is a progressive disorder with severe late complications. Normal wound healing involves a series of complex and well-orchestrated molecular events dictated by multiple factors. In diabetes, wound healing is grossly impaired due to defective, and dysregulated cellular and molecular events at all phases of wound healing resulting in chronic wounds that fail to heal. Carnosine, a dipeptide of alanine and histidine and an endogenous antioxidant is documented to accelerate healing of wounds and ulcers. However, not much is known about its role in wound healing in diabetes. Therefore, we studied the effect of carnosine in wound healing in db/db mice, a mice model of Type 2 DM. Six millimeter circular wounds were made in db/db mice and analyzed for wound healing every other day. Carnosine (100 mg/kg) was injected (I.P.) every day and also applied locally. Treatment with carnosine enhanced wound healing significantly, and wound tissue analysis showed increased expression of growth factors and cytokines genes involved in wound healing. In vitro studies with human dermal fibroblasts and microvascular-endothelial cells showed that carnosine increases cell viability in presence of high glucose. These effects, in addition to its known role as an antioxidant and a precursor for histamine synthesis, provide evidence for a possible therapeutic use of carnosine in diabetic wound healing.

Allogenous tendon stem/progenitor cells in silk scaffold for functional shoulder repair

Tendon stem/progenitor cells (TSPCs) were recently identified within tendon tissues. The aim of this study was to investigate TSPC-seeded knitted silk-collagen sponge scaffold for functional shoulder repair. The multidifferentiation potential, proliferation, and immune properties of TSPCs were investigated in vitro, while the efficacy of TSPC-seeded knitted silk-collagen sponge scaffolds in promoting rotator cuff regeneration was evaluated in vivo within a rabbit model. TSPCs, which exhibited universal stem cell characteristics (i.e., clonogenicity, high proliferative capacity, and multidifferentiation potential), nonimmunogenicity, and immunosuppression, proliferated well on our scaffold in vitro. Implantation of allogenous TSPC-seeded scaffolds within a rabbit rotator cuff injury model did not elicit an immunological reaction, but instead increased fibroblastic cell ingrowth and reduced infiltration of lymphocytes within the implantation sites at 4 and 8 weeks postsurgery. After 12 weeks, the allogenous TSPC-treated group exhibited increased collagen deposition and had better structural and biomechanical properties compared to the control group. This study thus demonstrated that the allogenous TSPC-seeded knitted silk-collagen sponge scaffold enhanced the efficacy of rotator cuff tendon regeneration by differentiating into tenocytes, and by secreting anti-inflammatory cytokines that prevent immunological rejection. Hence, allogenous TSPC-seeded knitted silk-collagen sponge scaffolds can be a clinically useful application for tendon tissue engineering.

MicroRNA-146a modulates TGF-β1-induced phenotypic differentiation in human dermal fibroblasts by targeting SMAD4

During wound healing and tissue repair the dermal fibroblast-to-myofibroblast transdifferentiation plays an important role, transforming growth factor-β1 (TGF-β1) is considered to be the main stimuli factor of transdifferentiation. MicroRNAs (miRNAs) have recently emerged as key post-transcriptional regulators of gene expression. The involvement of miRNAs and their roles in TGF-β1-induced myofibroblast transdifferentiation remains to be determined in detail. The current study found that the expression of miR-146a was upregulated in human dermal fibroblasts cells in response to TGF-β1 stimulation in dose-dependent manner by quantitative RT-PCR. Bioinformatic analyses predict that signaling effectors mothers against decapentaplegic protein 4 (SMAD4) is a miR-146a target gene. Luciferase assay demonstrated that miR-146a mimics suppressed SMAD4 3'-UTR reporter construct activity. Furthermore, miR-146a overexpression in dermal fibroblast did not decrease target mRNA levels, but significantly reduced target protein expression. In addition, dermal fibroblasts transfected with miR-146a mimics exhibited attenuated TGF-β1 -induced α-smooth muscle actin (α-SMA) expression compared with the control. This study demonstrated that miR-146a may function as a novel negative regulator to modulate myofibroblast transdifferentiation during TGF-β1 induction by targeting SMAD4.

Mouse treadmill running enhances tendons by expanding the pool of tendon stem cells (TSCs) and TSC-related cellular production of collagen

Exercise is known to enhance tendon size and strength, but the stem cell-based mechanisms for such exercise-induced effects are largely unknown. This study aims to explore these mechanisms by using a mouse treadmill running model to examine the effects of exercise on newly discovered tendon stem cells (TSCs). After treadmill running, patellar TSCs (PTSCs) and Achilles TSCs (ATSCs) were isolated from the mice, and their proliferation was measured in vitro. We found that treadmill running nearly doubled proliferation rates of both PTSCs and ATSCs compared to cage control mice. Moreover, using a mixed tendon cell culture consisting of TSCs and tenocytes, cellular production of collagen was found to increase by 70% and 200% in PTSCs and ATSCs, respectively, from the treadmill running group over cells from the cage control group. These findings suggest that exercise exerts its anabolic effects on tendons at least in part by increasing proliferation to expand the pool of TSCs and also by increasing TSC-related cellular production of collagen, the predominant component of tendons.

Modulation of wound contracture alpha-smooth muscle actin and multispecific vitronectin receptor integrin alphavbeta3 in the rabbit's experimental model

The myofibroblast, a major component of granulation tissue, is a key cell during wound healing, tissue repair and connective tissue remodelling. Persistence of myofibroblasts within a fibrotic lesion leads to excessive scarring impairing function and aesthetics. Various wound-healing cytokines can be modulated by topical application of active agents to promote optimal wound healing and improve scar quality. Thus, the myofibroblast may represent an important target for wound-healing modulation to improve the evolution of conditions such as hypertrophic scars. The purpose of this work is to study the modulation of myofibroblasts and integrin alphavbeta3 in a full thickness wound performed on rabbits treated with different topical agents using: (1) saline, (2) Tegaderm occlusive dressing (3) silver sulfadiazine and (4) moist exposed burn ointment (MEBO). The reepithelialisation was 4 days faster in the MEBO group compared with the other therapies with less oedema formation, delayed contraction, less inflammatory cells and the lowest transepidermal water loss (TEWL) resulting in a soft scar. Although alpha-smooth muscle actin (alpha-SMA) was the highest around day 12 in the MEBO group, wound contraction and myofibroblast's activity were the least for the same period probably because of a downregulation of the integrin alphavbeta3. It seems that the effect of MEBO could be more pronounced on force transmission rather then on force generation. Greater insight into the pathology of scars may translate into non surgical treatments in the future and further work in myofibroblast biology will eventually result in efficient pharmacological tools, improving the evolution of healing and scar formation.

Patterns of gene expression in a rabbit partial anterior cruciate ligament transection model: the potential role of mechanical forces

BACKGROUND

The inconsistency in healing after anterior cruciate ligament (ACL) repair has been attributed to ACL fibroblast cellular metabolism, lack of a sufficient vascular supply, and the inability to form a scar or scaffold after ligament rupture because of the uniqueness of the intra-articular environment. Hypotheses (1) Stress deprivation in the surgically transected ACL will increase matrix metalloproteinase (MMP) and alpha smooth muscle actin (alpha-SMA) expression. (2) Stress deprivation will decrease collagen expression. (3) The transected anteromedial bundle of the ACL will demonstrate a pattern of gene expression similar to the completely transected ACL, while gene expression profiles in the intact posterolateral bundle will be similar to the sham-operated controls.

STUDY DESIGN

Controlled laboratory study.

METHODS

Thirty-six New Zealand White rabbits underwent a partial ACL surgical transection separating the anteromedial (AM) and posterolateral (PL) bundles and transecting the AM bundle. Contralateral ACLs were either sham operated or completely transected. Ligament tissue was harvested at 1, 2, or 6 weeks after surgery, and real-time PCR was performed using primers for collagen I, collagen III, alpha-SMA, MMP-1, and MMP-13.

RESULTS

At 1 week, a 28- and 29-fold increase in MMP-13 expression was seen in the complete transection and the transected AM bundle specimens when compared with sham-operated controls (P = .049, P = .018), respectively. There was no significant difference in MMP-13 between the sham controls and the intact PL bundle specimens. A 22- and 23-fold increase in alpha-SMA was seen (P = .03, P = .009) in the complete transection and transected AM bundle specimens, respectively, while no difference was seen between the intact PL bundle and controls. No significant differences were seen in collagen I (Col I) or collagen III (Col III) gene expression at 1 week. At 6 weeks, Col I expression increased 5-fold in complete transection samples (P = 3.9 x 10(-6)), 3-fold in transected AM samples (P = 3.3 x 10(-6)), and 2-fold in the intact PL bundle samples as compared with controls. alpha-SMA was increased 7.5-fold and 5-fold in complete transection and transected AM samples, respectively (P = .004, P = 2.2 x 10(-6)), while no significant change was seen in the intact PL bundle samples compared with controls. Complete transection specimens showed a 3-fold increase in MMP-1 expression. Col III increased 5.4-, 2.6-, and 2.4-fold in the complete transection, transected AM, and intact PL groups, respectively (P = .003, P = .004, P = .04).

CONCLUSION

Partial or complete surgical transection of the rabbit ACL with resultant loss of mechanical stimuli results in an increase in MMP-13 and alpha-SMA expression at the early time point (1 week) and an increase in alpha-SMA, Col I, and Col III expression at the later time point (6 weeks). These data provide support for the hypothesis that there is a time-dependent alteration of anabolic and catabolic matrix gene expression after injury/loss of ligament integrity. Clinical Relevance Identification of pathways that respond to mechanical stress in the intact ACL and after surgical transection may permit development of novel therapies to alter healing of the partial ACL injury or to assist in the development of biomechanical active ''smart'' scaffolds for tissue-engineered ligament replacements.

Treadmill running exercise results in the presence of numerous myofibroblasts in mouse patellar tendons

Mechanical loading is known to alter tendon structure, but its cellular mechanisms are unclear. This study aimed to determine the effect of mechanical loading on tendon cells in vivo. C57BL/6J female mice were used in a treadmill running study. The treadmill running protocol consisted of treadmill training for 1 week, followed by sustained moderate running at 13 m/min for 50 min/day, 5 days/week, for 3 weeks. Immunohistochemical staining of tendon sections of mice after treadmill running revealed that numerous cells in the tendon section expressed alpha-SMA, whereas in the tendon sections of control mice, only a few cells exhibited weak alpha-SMA signals. Furthermore, mouse patellar tendon cells (MPTCs) derived from treadmill running mice were generally larger in culture, proliferated faster, expressed a higher level of alpha-SMA, and formed more abundant stress fibers compared to MPTCs from control mice. In addition, MPTCs from treadmill running mice generated larger traction forces (169 +/- 66.1 Pa) than those from control mice (102 +/- 34.2 Pa). Finally, cells from treadmill running mice produced higher levels of total collagen (516.4 +/- 92.7 microg/10,000 cells) than their counterparts (303.9 +/- 34.8 microg/10,000 cells). Thus, mechanical loading via treadmill running increased the presence of myofibroblasts in mouse patellar tendons. As myofibroblasts are activated fibroblasts, their presence in the tendon following treadmill running indicates that they actively repair and remodel tendon tissue under strenuous mechanical loading, leading to known changes in tendon structure.

Cell shape regulates collagen type I expression in human tendon fibroblasts

Understanding the relationship between cell shape and cellular function is important for study of cell biology in general and for regulation of cell phenotype in tissue engineering in particular. In this study, microcontact printing technique was used to create cell-adhesive rectangular and circular islands. The rectangular islands had three aspect ratios: 19.6, 4.9, and 2.2, respectively, whereas circular islands had a diameter of 50 microm. Both rectangular and circular islands had the same area of 1960 microm(2). In culture, we found that human tendon fibroblasts (HTFs) assumed the shapes of these islands. Quantitative immunofluorescence measurement showed that more elongated cells expressed higher collagen type I than did less stretched cells even though cell spreading area was the same. This suggests that HTFs, which assume an elongated shape in vivo, have optimal morphology in terms of expression of collagen type I, which is a major component of normal tendons. Using immunohistochemistry along with cell traction force microscopy (CTFM), we further found that these HTFs with different shapes exhibited variations in actin cytoskeletal structure, spatial arrangement of focal adhesions, and spatial distribution and magnitude of cell traction forces. The changes in the actin cytoskeletal structure, focal adhesion distributions, and traction forces in cells with different shapes may be responsible for altered collagen expression, as they are known to be involved in cellular mechanotransduction.

HGF suppresses the production of collagen type III and alpha-SMA induced by TGF-beta1 in healing fibroblasts

The aim of this study was to examine the effectiveness of HGF in blocking TGF-beta1-induced collagen III and alpha-smooth muscle actin (alpha-SMA) production in rat healing fibroblasts, fibroblasts were obtained from healing medial collateral ligament (MCL) injury. Cell culture was supplemented with 5 ng/ml of TGF-beta1 along with increasing doses of HGF (10-40 ng/ml). The productions of collagen III in supernatants culture were assayed by enzyme-linked immunosorbent assay. Expression of alpha-SMA was assessed by Western blot. Treatment with TGF-beta1 significantly stimulated collagen III and alpha-SMA production in healing fibroblasts. Remarkably, the addition of HGF reduced productions of all components induced by TGF-beta1 in a dose-dependent manner. This study shows that HGF antagonizes the action of TGF-beta1 effectively in cultured healing MCL injury fibroblasts. The results provide a cellular and molecular basis for HGF's acting as a therapeutic agent for MCL scar formation and poor healing.

Is cultured tendon fibroblast a good model to study tendon healing?

Cultured tendon fibroblasts (CTFs) from intact explants are widely used to study tendon healing in vitro. The significance of these findings may rely on similarities between CTFs and healing tendon fibroblasts in situ. Our purpose was to compare CTFs with fibroblasts cultured from healing tendons. We cultured CTFs from intact and healing tendons at day 7 and day 14 postinjury in a rat model of patellar donor site injury. The mRNA expression of COL1A1, COL3A1, decorin, and biglycan, with or without supplementation of 1 ng/mL TGF-beta1, was compared by quantitative real-time RT-PCR. The expression of proliferation cell nuclear antigen (PCNA) and alpha-smooth muscle actin (alpha-SMA) was determined by immunostain. COL3A1 and decorin mRNA in CTFs was lower as compared to day 7 healing fibroblasts, but its biglycan mRNA level was higher than day 14 healing fibroblasts. TGF-beta1 increased COL1A1 and decorin mRNA in CTFs, but decreased the mRNA of all four genes in day 7 healing tendon fibroblasts. CTFs exhibited lower PCNA immunopositivity as compared to day 7 and day 14 healing fibroblasts, but a higher alpha-SMA immunopositivity than cultured day 14 healing fibroblasts. These findings showed that CTFs did not resemble healing tendon cells with respect to major cellular activities related to tendon healing. Thus, fibroblasts from healing tendon may be a more appropriate model for studying cellular activities in tendon healing.

Systemic vanadate ingestion improves early medial collateral ligament repair

The medial collateral ligament (MCL) of the knee is frequently injured in sport. Repair is slow and often complicated by scar formation which may result in impairment of function. Vanadate is a promising efficacious treatment for tissue injuries and this study aimed to examine its effect in rats on the histological and biomechanical features of MCL healing. Rats received either 0.025 g/kg per day vanadate or equivalent amounts of drinking water (control) by intragastric gavage for 1 week before and 2 weeks after wounding. Repaired sites were dissected out for histological and biomechanical tests 28 days after wounding. Fibre bundles in the vanadate-treated group were uniform and evenly spaced. Furthermore, vanadate significantly increased the diameter of collagen fibrils in the healing tissue. Stiffness and ultimate force of the femur-medial collateral ligament-tibia complex for the vanadate-treated group were significantly higher than for the controls. The results suggest that vanadate significantly improves the histological and biomechanical properties of healing MCL.

Mechanobiology of adult and stem cells

Mechanical forces, including gravity, tension, compression, hydrostatic pressure, and fluid shear stress, play a vital role in human physiology and pathology. They particularly influence extracellular matrix (ECM) gene expression, ECM protein synthesis, and production of inflammatory mediators of many load-sensitive adult cells such as fibroblasts, chondrocytes, smooth muscle cells, and endothelial cells. Furthermore, the mechanical forces generated by cells themselves, known as cell traction forces (CTFs), also influence many biological processes such as wound healing, angiogenesis, and metastasis. Thus, the quantitative characterization of CTFs by qualities such as magnitude and distribution is useful for understanding physiological and pathological events at the tissue and organ levels. Recently, the effects of mechanical loads on embryonic and adult stem cells in terms of self-renewal, differentiation, and matrix protein expression have been investigated. While it seems certain that mechanical loads applied to stem cells regulate their self-renewal and induce controlled cell lineage differentiation, the detailed molecular signaling mechanisms responsible for these mechano-effects remain to be elucidated. Challenges in the fields of both adult- and stem-cell mechanobiology include devising novel experimental and theoretical methodologies to examine mechano-responses more closely to various forms of mechanical forces and mechanotransduction mechanisms of these cells in a more physiologically accurate setting. Such novel methodologies will lead to better understanding of various pathological diseases, their management, and translational applications in the ever expanding field of tissue engineering.

A comparison of rabbit mesenchymal stem cells and anterior cruciate ligament fibroblasts responses on combined silk scaffolds

The aim of this study was to compare the cellular responses of bone marrow-derived mesenchymal stem cells (BMSCs) and anterior cruciate ligament fibroblasts (ACLFs) on combined silk scaffolds for ligament tissue engineering application. Rabbit BMSCs and ACLFs were isolated and cultured in vitro for two weeks after seeding on the silk scaffolds. Samples were evaluated and compared for their cellular morphology, proliferation, gene and protein expression of tenascin-C, type I and type III collagen. In addition, the two cell types were transfected with green fluorescent protein (GFP) to trace their fate in the knee joints. Preliminary results comparing cell proliferation indicated that BMSCs proliferated faster than ACLFs. Gene expression of the phenotypic markers measured using real-time reverse transcription polymerase chain reaction (RT-PCR) indicated the transcript levels of BMSCs were significantly increased after two weeks of culture, whereas those of ACLFs had no significant difference. The protein levels and localization were determined by western blotting and immunohistochemical staining, the results showed more production of ligament-related extracellular matrix (ECM) by BMSCs as compared to ACLFs. Moreover, 4 weeks postoperatively, more fluorescent cells were presented in BMSC-loaded constructs than in ACLF-loaded constructs. Therefore, based on the cellular response in vitro and in vivo, BMSCs were found to be a better cell source than ACLFs for the further study of ACL tissue engineering.