The use of connective tissue growth factor mimics for flexor tendon repair

Intrasynovial flexor tendon lacerations of the hand are clinically problematic, typically requiring operative repair and extensive rehabilitation. The small-molecule connective tissue growth factor (CTGF) mimics, oxotremorine M (Oxo-M) and 4-PPBP maleate (4-PPBP), have been shown to improve tendon healing in small animal models by stimulating the expansion and differentiation of perivascular CD146+ cells. To enhance intrasynovial flexor tendon healing, small-molecule CTGF mimics were delivered to repaired canine flexor tendons via porous sutures. In vitro studies demonstrated that Oxo-M and 4-PPBP retained their bioactivity and could be released from porous sutures in a sustained manner. However, in vivo delivery of the CTGF mimics did not improve intrasynovial tendon healing. Histologic analyses and expression of tenogenic, extracellular matrix, inflammation, and remodeling genes showed similar outcomes in treated and untreated repairs across two time points. Although in vitro experiments revealed that CTGF mimics stimulated robust responses in extrasynovial tendon cells, there was no response in intrasynovial tendon cells, explaining the lack of in vivo effects. The results of the current study indicate that therapeutic strategies for tendon repair must carefully consider the environment and cellular makeup of the particular tendon for improving the healing response.

Enhancement of Anterior cruciate ligament injury repairing using connective tissue growth factor in a rabbit model

The study was to evaluate the contribution of connective tissue growth factor (CTGF) to the regeneration of the torn anterior cruciate ligament (ACL) in a rabbit. ACL transection surgeries were performed on both knees of male New Zealand rabbits. Then injury reparation was done as follows: 0.5ml fibrin glue (FG) alone (FG-treated group, n=24 knees) and 0.5ml FG dissolve with 15ng CTGF (CTGF/FG-treated group, n=24 knees). At 2 or 6 weeks after surgery, the ACLs were characterized histologically (n=6 knees) and biomechanically (n=6 knees). The healing effect of the CTGF/FG-treated group was obviously better than that of the FG-treated group, with an increased amount of collagen fibers and fibroblasts in the ligament tissue. After 2 or 6 weeks of healing, CTGF/FG-treated group exhibited significantly higher maximum loads of 8.50±0.58N and 16.35±1.16N, compared with the control group (7.52±0.80N and 13.60±1.35N). And the stiffness of CTGF/FG-treated group at 2 or 6 weeks post-intervention (5.59±1.24N/mm and 11.64±2.21N/mm) was remarkably higher than that the control group (3.74±0.89N/mm and 6.83±2.51N/mm). CTGF could serve as a potentially attractive tool for improving ACL injury treatment by promoting the regeneration of related cells.

CTGF/CCN2 Postconditioning Increases Tolerance of Murine Hearts towards Ischemia-Reperfusion Injury

Background and Purpose

Previous studies of ischemia-reperfusion injury (IRI) in hearts from mice with cardiac-restricted overexpression of CCN2 have shown that CCN2 increases tolerance towards IRI. The objectives of this study were to investigate to what extent post-ischemic administration of recombinant human CCN2 (rhCCN2) would limit infarct size and improve functional recovery and what signaling pathways are involved.

Experimental Approach

Isolated mice hearts were perfused ad modum Langendorff, subjected to no-flow, global ischemia, and subsequently, exposed to mammalian cell derived, full-length (38-40kDa) rhCCN2 (250 nM) or vehicle during the first 15 min of a 60 min reperfusion period.

Key Results

Post-ischemic administration of rhCCN2 resulted in attenuation of infarct size from 58 ± 4% to 34 ± 2% (p < 0.001) which was abrogated by concomitant administration of the PI3 kinase inhibitor LY294002 (45 ± 3% vs. 50 ± 3%, ns). In congruence with reduction of infarct size rhCCN2 also improved recovery of left ventricular developed pressure (p < 0.05). Western blot analyses of extracts of ex vivo-perfused murine hearts also revealed that rhCCN2 evoked concentration-dependent increase of cardiac phospho-GSK3β (serine-9) contents.

Conclusions and Implications

We demonstrate that post-ischemic administration of rhCCN2 increases the tolerance of ex vivo-perfused murine hearts to IRI. Mechanistically, this postconditioning effect of rhCCN2 appeared to be mediated by activation of the reperfusion injury salvage kinase pathway as demonstrated by sensitivity to PI3 kinase inhibition and increased CCN2-induced phosphorylation of GSK3β (Ser-9). Thus, the rationale for testing rhCCN2-mediated post-ischemic conditioning of the heart in more complex models is established.

Comment on "Topically Applied Connective Tissue Growth Factor/CCN2 Improves Diabetic Preclinical Cutaneous Wound Healing: Potential Role for CTGF in Human Diabetic Foot Ulcer Healing"

A recent paper in this journal, presented a novel method by topical application of growth factors in stimulating diabetic cutaneous wound healing that caught our attention. We believe that the experimental method in the article is efficient and creative, but it also has some controversies and shortcomings to be discussed. We noted that the authors used "Tegaderm" as a semiocclusive dressing film and stated that it exerted a "splinting effect" on the wound margins and controlled contraction. Indeed, the "Tegaderm" itself can serve as a dressing film to isolate the wound bed with outside environments while the "splinting effect" is mainly achieved by adding silicone splints around the wound. Considering the unique properties of silicone splints and "Tegaderm," our experimental group propose an alternative method named "combined-suturing" technique that is not only suturing the silicone splints but also securing the "Tegaderm" around the wound. The specific reasons and operative procedures are explained in detail in this letter.

Topically applied connective tissue growth factor/CCN2 improves diabetic preclinical cutaneous wound healing: potential role for CTGF in human diabetic foot ulcer healing

AIMS/HYPOTHESIS

Topical application of CTGF/CCN2 to rodent diabetic and control wounds was examined. In parallel research, correlation of CTGF wound fluid levels with healing rate in human diabetic foot ulcers was undertaken.

METHODS

Full thickness cutaneous wounds in diabetic and nondiabetic control rats were treated topically with 1 μg rhCTGF or vehicle alone, on 2 consecutive days. Wound healing rate was observed on day 14 and wound sites were examined for breaking strength and granulation tissue. In the human study across 32 subjects, serial CTGF regulation was analyzed longitudinally in postdebridement diabetic wound fluid.

RESULTS

CTGF treated diabetic wounds had an accelerated closure rate compared with vehicle treated diabetic wounds. Healed skin withstood more strain before breaking in CTGF treated rat wounds. Granulation tissue from CTGF treatment in diabetic wounds showed collagen IV accumulation compared with nondiabetic animals. Wound α-smooth muscle actin was increased in CTGF treated diabetic wounds compared with untreated diabetic wounds, as was macrophage infiltration. Endogenous wound fluid CTGF protein rate of increase in human diabetic foot ulcers correlated positively with foot ulcer healing rate (r = 0.406; P < 0.001).

CONCLUSIONS/INTERPRETATION

These data collectively increasingly substantiate a functional role for CTGF in human diabetic foot ulcers.

[Enhancement of meniscal tearing damage repairing in the avascular zone using connective tissue growth factor (CTGF) in the rabbit model]

OBJECTIVE

To investigate effect of connective tissue growth factors (CTGF) on secretion of extracellular matrix synthesis of meniscal fibrochondrocytes, expression of vascular endothelial growth factors (VEGF), and angiogenesis during the repair of meniscal tearing damage.

METHODS

Meniscal fibrochondrocytes were isolated from the inner--1/2 of rabbits' meniscus by collagenase enzymatic digestion, centrifugal separation, and treated with 100 ng/ml CTGF in vitro. Characterization of fibrochondrocytes was identified by flow cytometry analysising CD31, CD44, CD45 and CD105, and was further tested by type II collagen immunocytochemistry. Changes in gene expression of meniscal fibrochondrocytes were monitored by quantitative real-time polymerase chain reaction. In vitro, the sections of the 3 mm of the longitudinal teared in the middle of the rabbit's meniscus, and then the defects were dealed with simple suture, suture and implanting with PBS-fibrin glue, sutured and implanting with 1.5 microg CTGF respectively. Expression and distribution of type I and II collagen and VEGF, the tearing healing were observed by fluorescence-immunohistochemisty analysis on the 1st week, the 4th week and the 10th week.

RESULTS

Quantitative RT-PCR assays showed that type I and type II collagen,and VEGF mRNA expression in the 100 ng/ml CTGF group had been remarkably enhanced than in the PBS group on the 14th day. Consistent with these effects in vitro, fluorescence-immunohistochemical analysis revealed that in the group implanted with CTGF-fibrin glue, type I collagen, type I collagen and capillaries completely filled the defect on the 10th week postoperatively. In contrast, only soft tissue repair occurred after the PBS-fibrin glue was implanted.

CONCLUSION

CTGF can significantly promote extracellular matrix (I collagen, II collagen) of the meniscal avascular zone synthesis, and CTGF can greatly heighten the expression of VEGF activity at the same time in vitro, so that it can further enhance the repair of meniscal tearing damage in the avascular zone.

Potential applications for cell regulatory factors in liver progenitor cell therapy

Orthotopic liver transplant represent the state of the art treatment for terminal liver pathologies such as cirrhosis in adults and hemochromatosis in neonates. A limited supply of transplantable organs in relationship to the demand means that many patients will succumb to disease before an organ becomes available. One promising alternative to liver transplant is therapy based on the transplant of liver progenitor cells. These cells may be derived from the patient, expanded in vitro, and transplanted back to the diseased liver. Inborn metabolic disorders represent the most attractive target for liver progenitor cell therapy, as many of these disorders may be corrected by repopulation of only a portion of the liver by healthy cells. Another potential application for liver progenitor cell therapy is the seeding of bio-artificial liver matrix. These ex vivo bioreactors may someday be used to bridge critically ill patients to other treatments. Conferring a selective growth advantage to the progenitor cell population remains an obstacle to therapy development. Understanding the molecular signaling mechanisms and micro-environmental cues that govern liver progenitor cell phenotype may someday lead to strategies for providing this selective growth advantage. The discovery of a population of cells within the bone marrow possessing the ability to differentiate into hepatocytes may provide an easily accessible source of cells for liver therapies.