Tissue origin and extracellular matrix control neutral proteinase activity in human fibroblast three-dimensional cultures

Revisited and innovative perspectives of oral ulcer: from biological specificity to local treatment

Mouth ulcers, a highly prevalent ailment affecting the oral mucosa, leading to pain and discomfort, significantly impacting the patient's daily life. The development of innovative approaches for oral ulcer treatment is of great importance. Moreover, a deeper and more comprehensive understanding of mouth ulcers will facilitate the development of innovative therapeutic strategies. The oral environment possesses distinct traits as it serves as the gateway to the digestive and respiratory systems. The permeability of various epithelial layers can influence drug absorption. Moreover, oral mucosal injuries exhibit distinct healing patterns compared to cutaneous lesions, influenced by various inherent and extrinsic factors. Furthermore, the moist and dynamic oral environment, influenced by saliva and daily physiological functions like chewing and speaking, presents additional challenges in local therapy. Also, suitable mucosal adhesion materials are crucial to alleviate pain and promote healing process. To this end, the review comprehensively examines the anatomical and structural aspects of the oral cavity, elucidates the healing mechanisms of oral ulcers, explores the factors contributing to scar-free healing in the oral mucosa, and investigates the application of mucosal adhesive materials as drug delivery systems. This endeavor seeks to offer novel insights and perspectives for the treatment of oral ulcers.

Multiple functions of gingival and mucoperiosteal fibroblasts in oral wound healing and repair

Fibroblasts are cells of mesenchymal origin. They are responsible for the production of most extracellular matrix in connective tissues and are essential for wound healing and repair. In recent years, it has become clear that fibroblasts from different tissues have various distinct traits. Moreover, wounds in the oral cavity heal under very special environmental conditions compared with skin wounds. Here, we reviewed the current literature on the various interconnected functions of gingival and mucoperiosteal fibroblasts during the repair of oral wounds. The MEDLINE database was searched with the following terms: (gingival OR mucoperiosteal) AND fibroblast AND (wound healing OR repair). The data gathered were used to compare oral fibroblasts with fibroblasts from other tissues in terms of their regulation and function during wound healing. Specifically, we sought answers to the following questions: (i) what is the role of oral fibroblasts in the inflammatory response in acute wounds; (ii) how do growth factors control the function of oral fibroblasts during wound healing; (iii) how do oral fibroblasts produce, remodel and interact with extracellular matrix in healing wounds; (iv) how do oral fibroblasts respond to mechanical stress; and (v) how does aging affect the fetal-like responses and functions of oral fibroblasts? The current state of research indicates that oral fibroblasts possess unique characteristics and tightly controlled specific functions in wound healing and repair. This information is essential for developing new strategies to control the intraoral wound-healing processes of the individual patient.

Effects of minimal persistent inflammation on nasal mucosa of experimental allergic rhinitis

BACKGROUND

Minimal persistent inflammation (MPI) is considered another piece of the complex puzzle of allergic inflammation. Although some studies regarding MPI have been reported, no study has evaluated the effects of MPI on the structure changes at the site of allergic reaction. This study investigates whether long-time MPI during allergic rhinitis (AR) results in some features of tissue remodeling in the nasal mucosa.

METHODS

An animal model of MPI was developed by repeated nasal challenge with low concentration of ovalbumin (OVA) in sensitized guinea pigs. The models were assessed by allergic symptom after antigen challenge, eosinophil infiltration in the nasal mucosa, and intercellular adhesion molecule (ICAM) 1 expression on nasal epithelial cells. The histopathological changes in nasal mucosa were determined by Alcian blue-periodic acid-Schiff and Masson's trichrome staining. The expression of transforming growth factor (TGF) beta(1) and matrix metalloproteinase (MMP) 9 was examined by immunofluorescence under a confocal laser scan microscope.

RESULTS

When sensitized animals were challenged with the low concentration of 0.01% OVA, the symptom of sneezing disappeared, but there were still mild eosinophils infiltration and weak ICAM-1 expression, which indicated the success of MPI models. Moreover, the number of goblet cells and the percentage area of collagen deposition were both mildly increased. The expression of MMP-9 and TGF-beta(1) was also weakly elevated.

CONCLUSION

We have successfully established MPI models and proved long-time MPI may result in mild features of remodeling in the nasal mucosa, which provide new insights into the unexpected potential effects of MPI on the structural changes.

Recombinant protein-co-PEG networks as cell-adhesive and proteolytically degradable hydrogel matrixes. Part II: biofunctional characteristics

We present here the biological performance in supporting tissue regeneration of hybrid hydrogels consisting of genetically engineered protein polymers that carry specific features of the natural extracellular matrix, cross-linked with reactive poly(ethylene glycol) (PEG). Specifically, the protein polymers contain the cell adhesion motif RGD, which mediates integrin receptor binding, and degradation sites for plasmin and matrix-metalloproteinases, both being proteases implicated in natural matrix remodeling. Biochemical assays as well as in vitro cell culture experiments confirmed the ability of these protein-PEG hydrogels to promote specific cellular adhesion and to exhibit degradability by the target enzymes. Cell culture experiments demonstrated that proteolytic sensitivity and suitable mechanical properties were critical for three-dimensional cell migration inside these synthetic matrixes. In vivo, protein-PEG matrixes were tested as a carrier of bone morphogenetic protein (rhBMP-2) to heal critical-sized defects in a rat calvarial defect model. The results underscore the importance of fine-tuning material properties of provisional therapeutic matrixes to induce cellular responses conducive to tissue repair. In particular, a lack of rhBMP or insufficient degradability of the protein-PEG matrix prevented healing of bone defects or remodeling and replacement of the artificial matrix. This work confirms the feasibility of attaining desired biological responses in vivo by engineering material properties through the design of single components at the molecular level. The combination of polymer science and recombinant DNA technology emerges as a powerful tool for the development of novel biomaterials.

Elastolysis induces collagenolysis in a gingival lamina propria model

Elastin peptides were previously reported to increase MMP expression in several cell types. We found binding of these peptides to their receptors led to enhanced MMP-3 and MMP-1 expression, but not activation, in human gingival fibroblasts cultured on plastic dishes. We hypothesized that these peptides, in a more physiological environment, might additionally trigger an MMP-3/MMP-1 activation cascade, leading to matrix lysis, as occurs in periodontitis. To test this hypothesis, we used contracted and attached lattices as gingival lamina propria equivalents. In such 3D models, supplementation of elastin peptides and plasminogen triggered an MMP-3/MMP-1 activation cascade and significant down-regulation of TIMPs production, further leading to intense collagen degradation. We propose that elastolysis, as occurs in periodontitis, potentiates collagenolysis, thus promoting disease progression.

Treating asthma as an inflammatory disease

Asthma is a chronic inflammatory disease involving many different cell types and cellular elements. Evidence suggests that, in the long term, this inflammation leads to remodeling of the airways, airflow obstruction, and the bronchial hyperreactivity symptoms of asthma, and is present even in patients with intermittent disease. Patients with allergic asthma and those with seasonal allergic rhinitis are believed to have minimal persistent inflammation, and the two diseases often occur together. Early intervention with inhaled corticosteroids (ICS) is believed to modify the disease process and may limit long-term remodeling. ICS remain the cornerstone and "gold standard" of treatment for asthma.

Collagen degradation by interleukin-1beta-stimulated gingival fibroblasts is accompanied by release and activation of multiple matrix metalloproteinases and cysteine proteinases

OBJECTIVE

Several collagenolytic matrix metalloproteinases (MMPs) have recently been identified in gingival fibroblasts, while secreted cysteine proteinases could also participate in connective tissue destruction in periodontitis. To clarify their involvement, we examined enzyme release during collagen breakdown by cultured cytokine-stimulated fibroblasts.

MATERIALS AND METHODS

Gingival fibroblasts were derived from four chronic periodontitis patients and cultured on collagen gels in serum-free medium for 1-4 days. Collagenolysis was measured by hydroxyproline release into the medium. Proteinases were assessed by electrophoresis and immunoblotting.

RESULTS

Adding interleukin-1beta resulted in progressive gel breakdown. This was associated particularly with a shift in MMP-1 band position from proenzyme to active enzyme and the appearance of active as well as proenzyme forms of cathepsin B. There was also partial processing of pro-MMP-13 and increased immunoreactivity for active cathepsin L. In addition, both pro-forms and active forms of MMP-8, membrane-type-1-MMP and MMP-2 were present in control and treated cultures.

CONCLUSIONS

Fibroblast MMP-1 was most likely responsible for collagen dissolution in the culture model, while cathepsin B may have been part of an activation pathway. All studied proteinases contribute to extracellular matrix destruction in inflamed gingival tissue, where they probably activate each other in proteolytic cascades.

Local expression of indoleamine 2,3-dioxygenase protects engraftment of xenogeneic skin substitute

The expression of indoleamine 2,3-dioxygenase (IDO), which metabolizes tryptophan, an essential amino acid, into kynurenine, has been identified as having a key role in the prevention of the immune rejection of the semi-allogeneic fetus during pregnancy. We have previously demonstrated that IDO expressed in fibroblasts causes bystander CD4(+) T cell damage as well as THP-1 cell damage by apoptosis. As T cells are primarily responsible for graft rejection, here, we asked the question of whether engraftment of IDO-expressing xenogeneic fibroblasts populated in a collagen matrix can be immuno-protected in an animal model. The results show a significant reduction in the number of infiltrated CD3(+) T lymphocytes on days 14 and 28 post-transplantation in the wounds receiving IDO-expressing fibroblasts relative to controls. IDO-expressing human fibroblasts embedded in bovine collagen on wounds in a rat model accelerates wound healing by promoting neovascularization during the early stages and providing protection of the xenograft fibroblasts. Using a co-culture system, we further confirm that IDO can induce angiogenesis through the depletion of tryptophan. These findings suggest that IDO may have an application in promoting the engraftment of skin substitutes and other transplanted organs.

Inhibition of plasmin-mediated prostromelysin-1 activation by interaction of long chain unsaturated fatty acids with kringle 5

C18 unsaturated fatty acids were here found to inhibit proMMP (matrix metalloproteinase)-3 activation by plasmin. This effect was suppressed by lysine ligand competitors, indicating that it was mediated by binding to kringle domains. Surface plasmon resonance analysis demonstrated that oleic acid interacted to a similar extent with plasmin and kringle 5 (KD values of 3.4 x 10(-8) and 5.9 x 10(-8)M) while interaction with kringles 1-2-3 was 10-fold lower. Furthermore, oleic acid stimulated the amidolytic activity of plasmin and mini-plasmin, but not micro-plasmin. Oleic acid also enhanced u-PA (urokinase-type plasminogen activator)-mediated plasminogen activation over 50-fold. Taken together, these data indicate that inhibition of plasmin-induced proMMP-3 activation by unsaturated fatty acids was mediated through their preferential binding to kringle 5. The influence of elaidic acid on the plasmin/MMP-3/MMP-1 proteolytic cascade was assessed ex vivo. Exogenous addition of plasmin to dermal fibroblasts or supplementation of gingival fibroblast culture medium with plasminogen triggered this cascade. In both instances, elaidic acid totally abolished proMMP-3 and proMMP-1 activation. Additionally, a significant decrease in lattice retraction and collagen degradation in a range similar to that obtained with Batimastat was observed when human gingival fibroblasts were cultured in plasminogen-containing type I collagen gels, indicative of the dual influence of unsaturated fatty acids on MMP activation and activity. In conclusion, unsaturated fatty acids or molecules with similar structures could be attractive target for the development of natural pharmacological inhibitors directed against plasmin and/or MMPs in different pathological contexts such, skin UV irradiation, vascular diseases and tumour growth and invasion.

Effects of a vegetable extract from Lupinus albus (LU105) on the production of matrix metalloproteinases (MMP1, MMP2, MMP9) and tissue inhibitor of metalloproteinases (TIMP1, TIMP2) by human gingival fibroblasts in culture

This study examined the effects of a vegetable extract from Lupinus albus (LU105) on MMPs and TIMPs secreted by human gingival fibroblasts in culture. LU105 was extracted from seeds of L. albus and is freely soluble in water. Gelatin zymography showed that control human gingival fibroblasts maintained in culture for 48 h express pro-MMP2 (progelatinase A) in the culture medium while the active form of MMP2 (gelatinase A), the active form of MMP9 (gelatinase B), and pro-MMP9 (progelatinase B) are not detected. Fibroblasts derived from inflamed gingiva expressed in the culture medium increased amounts of pro-MMP2 (progelatinase A) compared with controls and significant amounts of pro-MMP9 (progelatinase B). LU105 diminished the expression by gingival fibroblasts derived from inflamed tissue of both pro-MMP2 and pro-MMP9. Furthermore LU105 did not modify the amount of TIMP2 expressed in culture by controls or by gingival fibroblasts derived from inflamed tissue. TIMP1 and MMP1 significantly decreased when LU105 was added in the culture media of gingival fibroblasts derived from inflamed tissue compared with control fibroblasts. Thus LU105 seems to offer an opportunity to restore a correct balance between MMP2, MMP9, MMP1, and their natural inhibitors, i.e., TIMP1 and TIMP2 in human inflamed gingiva.

Effects of mechanical tension on matrix degradation by human periodontal ligament cells cultured in collagen gels

BACKGROUND

Periodontal ligament (PDL) cells are thought to play a crucial role in the remodelling of periodontal tissues during orthodontic tooth movement.

OBJECTIVE

The objective of this study was to analyse the effects of mechanical tension on matrix degradation by PDL cells cultured in collagen gels.

METHODS

The gels were prepared free-floating or attached to the culture wells and cultured for up to 22 d. In free-floating gels very little mechanical tension is generated within the matrix, whereas in attached gels tension is highly increased.

RESULTS

At d 8, free-floating gels had contracted to 2% of their original wet weight. Attached gels had contracted to only 40%, but by d 15 all gels had spontaneously detached from the wells and had contracted rapidly. The collagen content of free-floating gels had decreased to 30% of the initial value at d 22. Collagenase activity was detected in the culture media of the free-floating gels and the presence of matrix metalloproteinases (MMPs) 2 and 9 was shown by zymography. In addition, histological sections showed matrix degradation around the cells. This shows that ligament cells in free-floating gels are actively resorbing the collagen matrix. The collagen content of attached gels did not change during the first 8 d but, after detachment, it rapidly decreased to 2%. Therefore, mechanical tension seems to prevent degradation of the matrix. In contrast, relaxation of the tension enhances the resorptive activity.

CONCLUSIONS

The sensitivity of PDL cells to mechanical tension may be essential for the remodelling of periodontal tissues and their adaptation to physiological and orthodontic forces.

Healing is delayed in oral compared to dermal excisional wounds

BACKGROUND

Oral wound healing is reported to occur more rapidly than dermal healing due, in part, to factors in saliva that facilitate the repair process. However, the oral environment also presents challenges to healing that include a large commensal flora and trauma from mastication.

METHODS

Excisional punch biopsies (1.5 mm) were placed in the scalp and hard palate of mice to create similar wounds with an osseous floor and relatively thick connective tissue walls. Histomorphometric analysis of hematoxylin and eosin-stained sections was performed at the widest part of each lesion.

RESULTS

The rate of epithelial and connective tissue coverage and the amount of new connective tissue formed were delayed in the oral compared to dermal wounds. In addition, the number of polymorphonuclear leukocytes (PMNs) was significantly higher and more persistent in the oral wounds.

CONCLUSIONS

Under conditions where a considerable amount of new connective tissue synthesis is required, oral healing is slower than dermal repair. This may be due to a higher degree of inflammatory stimulation induced by conditions present in the oral environment.

Collagen type I, III and V differently modulate synthesis and activation of matrix metalloproteinases by cultured rabbit periosteal fibroblasts

In the present study we investigated whether the collagen types I, III and V affect the activity of fibroblasts obtained from rabbit periosteum. The cells were cultured on plates either or not coated with different amounts of collagen type I, III or V and analyzed for their attachment, DNA synthesis and the expression and activity of matrix metalloproteinases (MMPs). Our data show that the three collagen types promoted attachment and spreading of the cells and stimulated DNA synthesis when used in relatively low concentrations. High concentrations of type V-but not of type I or III-proved to inhibit thymidine incorporation. The expression and activity of matrix metalloproteinase 1 (MMP-1; interstitial collagenase) decreased under the influence of relatively low amounts of collagen (<40 microg/well), whereas higher levels increased its release. Matrix metalloproteinase 2 (MMP-2; gelatinase A) was up-regulated by the different types of collagen; the active fraction of stromelysin-1 (MMP-3) decreased. Accordingly, the mRNA expression of MMP-1 and -3 were reduced. The expression of MMP-2 mRNA, however, proved to be unaffected. Blocking antibodies to beta(1)-integrin or echistatin increased the level of MMP-1 but had no effect on MMP-2. All parameters tested were similarly affected by type I and III collagen, whereas the effect of type V was always less. We conclude that the collagen types I, III and V provide different sets of signals for fibroblasts that differently modulate their proliferation and MMP expression.

Effect of avocado and soybean unsaponifiables on gelatinase A (MMP-2), stromelysin 1 (MMP-3), and tissue inhibitors of matrix metalloproteinase (TIMP- 1 and TIMP-2) secretion by human fibroblasts in culture

BACKGROUND

In inflamed periodontal tissues, gingival fibroblasts are able to express matrix metalloproteinases (MMPs) and their natural inhibitors, tissue inhibitors of matrix metalloproteinases (TIMPs). They can also respond to growth factors and cytokines. In this study, the in vitro effects of avocado and soybean unsaponifiable residues (ASU), their fractions (avocado unsaponifiable [ASF] or soy unsaponifiable [SSF]) on MMP-2 and MMP-3, and the activity and secretion of their inhibitors TIMP-1 and TIMP-2 were investigated using cultured human gingival fibroblasts.

METHODS

Gingival fibroblasts were cultured for 72 hours with ASU, ASF, and SSF at concentrations of 0. 1, 0.5, 2.5, 5, and 10 microgram/ml of culture medium, after pretreatment or no pretreatment for 1 hour with interleukin-1beta (IL-1beta). MMP-2 and MMP-3 were detected and quantified in the culture media after zymography and image analysis. TIMP-1, TIMP-2, MMP-2, and MMP-3 were also evidenced by dot blotting and quantified by image analysis.

RESULTS

In the absence of IL-1beta, a slight decrease in the secretion of MMP-2 was observed with lower doses of ASU, ASF, and SSF. The decrease of MMP-3 secretion was clearly marked with all fractions especially at low concentrations (0.1 and 2.5 microgram/ml). A slight decrease in TIMP-2 secretion was seen for low doses of ASU, ASF, and SSF, while a small increase was seen at higher concentrations. Concerning TIMP-1, no significant variation was observed in culture medium for low concentrations, and a decrease was noted for 5 and 10 microgram/ml of ASU, ASF, and SSF. As anticipated, IL-1beta induced a marked release of MMP-2, MMP-3, and TIMP-1, but no variation for TIMP-2 was seen. ASU, ASF, and SSF reversed the IL-1beta effect on gingival fibroblasts for MMP-2 and MMP-3, particularly with doses varying from 0.1 to 2.5 microgram/ml and for TIMP-1, particularly with doses varying from 2.5 to 10 microgram/ml.

CONCLUSIONS

These findings suggest a potential role for avocado and soy unsaponifiable extracts to prevent the deleterious effects of IL-1beta that occur during periodontal diseases.

Contribution of the plasmin/matrix metalloproteinase cascade to the retraction of human fibroblast populated collagen lattices

To assess the contribution of the plasmin/matrix metalloproteinase cascade in lattices retraction, human gingival fibroblast-populated collagen lattices were supplemented with plasminogen. The rate of lattice retraction was enhanced by addition of plasminogen. This effect was concomitant to plasmin generation, prostromelysin-1 and procollagenase activation. Plasminogen-mediated initiation of that proteolytic cascade was accompanied by conspicuous changes in cell morphology and collagen fibers organization. At day 1 of culture fibroblasts shifted from a rounded (control) to an elongated (in presence of plgn) shape. At the latest stage of retraction, intense vacuolization around fibroblasts was noticed in plgn-supplemented lattices which paralleled the increased collagen degradation. Plgn-enhancing influence on the initial phase of lattice retraction could be totally annihilated by either aprotinin or Batimastat. Those data emphasize the crucial importance of the plasmin-MMP proteolytic cascade in granulation tissue retraction in a healing wound.

Influence of heparin(s) on the interleukin-1-beta-induced expression of collagenase, stromelysin-1, and tissue inhibitor of metalloproteinase-1 in human gingival fibroblasts

Here, we describe the influence of heparin(s) on the interleukin-1-beta (IL-1beta)-induced expression of collagenase (matrix metalloproteinase-1, MMP-1), stromelysin-1 (matrix metalloproteinase-3, MMP-3) and tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) in human gingival fibroblasts (HGF). Amounts of secreted enzymes and inhibitors as well as their mRNA steady-state levels increased significantly following supplementation of HGF culture medium with 2 ng/mL of IL-1 beta1. Addition of heparin to cell culture medium 1 hour following IL-1beta decreased MMP and TIMP-1 expression in a dose-dependent manner. The inhibitory effect of heparin was significant at a concentration as low as 1 microg/mL. These findings could be reproduced with a low Mr heparin fragment devoid of anticoagulant activity. Heparin and fragments might therefore reduce the excessive proteolytic capacity of the gingival fibroblast during inflammation and could be useful as pharmacological agent(s) in gingivitis and periodontitis.

Morphometric studies of collagen and fibrin lattices contracted by human gingival fibroblasts; comparison with dermal fibroblasts

Cell shape variations and substratum re-organization during contraction of floating collagen and fibrin lattices seeded with human gingival fibroblasts were determined by computerized image analysis of light and scanning electron microscopic images. Data were compared with those obtained with lattices populated with human dermal fibroblasts. The extent of collagen lattice contraction was similar with both cell types, resulting in a two-fold decrease in the area fractions occupied by collagen fibers. Fibroblasts exhibited a rounded shape (form factors equal to 0.8 and 0.7 for gingival and dermal cells, respectively) at day 1 of culture; they possessed a more elongated appearance (with form factors equal to 0.3 and 0.15 for gingival and dermal cells, respectively) at day 7. Continuous (gingival) and discontinuous (dermal) layers of cells were evidenced at the cortex of lattices. Contractions were associated with a significant reduction of the diameters of collagen fibers. Re-organization of substratum, as analyzed by the "Rose of Directions" technique, was evidenced only at the vicinity of filopodia where fibers ran parallel to these protrusions. Several lysed matrix cavities were observed when fibrin lattices were populated with gingival but not dermal fibroblasts at day 5 of culture. Although cells in fibrin lattices exhibited morphometric parameters comparable with those in collagen lattices, no fibroblast layers could be demonstrated at gel peripheries. Fibrin matrices consisted of an isotropic network of entangled fibrin filaments from the start of culture, and only a slight reduction of the diameters of fibrin fibers could be evidenced in dermal fibroblast-populated lattices. Fibrinolysis at the vicinity of gingival fibroblasts led to an entire re-organization of substratum toward the formation of larger fibers. The differential behavior of gingival vs. dermal fibroblasts inside fibrin but not collagen matrices could therefore partly explain the increased rate of remodeling of gingiva as compared with dermis.

The rate of fibrinolysis is increased by free retraction of human gingival fibroblast populated fibrin lattices

We previously demonstrated that human gingival fibroblasts (HGF), but not their dermal counterparts, when seeded in retracting fibrin lattices induced intense fibrinolysis that was observed at the earliest stages of contraction and led to complete matrix degradation by day 7 of culture. Our aim was to examine the influence of mechanical forces in such fibrinolytic processes. HGF were seeded in retracting (R) e.g. free floating or non retracting (NR) e.g. anchored fibrin lattices (FL). Cultures were analysed from day 1-12 by phase contrast microscopy and scanning electron microscopy (s.e.m.). Levels of fibrin degradation products (FDP) and tissue plasminogen activator (tPA) accumulating in culture media were quantified by ELISA. Urokinase (uPA) and gelatinase A (MMP2) were identified by zymographic techniques. At the s.e.m. level, vacuolization around some HGF was noticed at the earliest stages of culture for RFL and complete degradation of lattices occurred at day 7. Formation of lysed matrix cavity was far less intense in NRFL even after 12 days of culture. FDP amounts at day 4 of culture were equal to 79 +/- 14 and 8.5 +/- 0.6 micrograms/10(5) cells for RFL and NRFL, respectively; tPA levels were equal to 5.8 +/- 0.6 (RFL) and 2.1 +/- 0.3 ng/10(5) cells (NRFL) and differences were still evident at day 7. The kinetics of tPA production were identical in either retracting fibrin or collagen lattices. On the contrary, uPA and proMMP2 productions were similar in RFL and NRFL. Isometric forces, but not the matrix support, were responsible for accelerated tPA production and fibrinolysis in HGF populated lattices.