Growth and type-ll collagen expression in the glenoid fossa of the temporomandibular joint during altered loading: a study in the rat

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1 European Journal of Orthodontics 18 (1996) 3-9 O 1996 European Orthodontic Society Growth and type-ll collagen expression in the glenoid fossa of the temporomandibular joint during altered loading: a study in the rat M. Tuominen, T. Kantomaa, P. Pirttiniemi, and A. Poikela Department of Oral Development and Orthodontics, Institute of Dentistry, University of Oulu, Finland SUMMARY The aim of this study was to measure changes in growth of the glenoid fossa and its articular eminence after decreased loading. A further aim was to evaluate the role of mechanical forces in relation to the existence of a cartilage layer, by determining type-ll collagen secretion. A total of 99 Wistar rats were used: 48 animals were fed whole pellets and 51 were fed ground pellets. At age 21 days, after weaning, the upper and lower incisors of the soft-diet group were shortened by cutting them, twice a week. Ten animals fed whole pellets and fed ground pellets were injected i.p. with Alizarin red (200 mg/kg) at ages 22, 30 and 40 days, and killed at ages 30, 40 and 50 days respectively. The heads were freed from the soft tissue and the zygomatic process cut sagittally at the deepest point of the greatest transversal concavity of the eminence. Bone apposition was measured. The other animals were used for studies involving collagen II immunostaining. Bone growth decreased in the group fed ground pellets except in the anterior-most part of the glenoid fossa at 50 days. Immunohistochemical analysis revealed larger areas of anti-collagen II staining in the group fed whole pellets, most markedly in the posterior part of the glenoid fossa. Growth of the articulating surface of the temporal component of the temporomandibular joint appears to depend on mechanical factors, such as.the condyle. The underlying mechanics seem likely to be different. The presence of type-ll collagen is obviously not regulated only by compressive forces but probably also by tension loading. Introduction Bone formation in the area of the fossa has been stated to be intramembranous (Wright and Moffett, 1974). Formation, growth and shaping of the articulating surface of the temporal bone has been explained on the basis of the effect of articular function (Scott, 1955; Moffett, 1968; Hall, 1984). Osteogenesis in the area of the articular eminence is promoted by a secondary cartilage (Wright and Moffett, 1974). The histological structure of the articulating surface of the temporal bone is similar to that seen in the mandibular condyle. However, the thickness of the layers is different (Folke and Stallard, 1967; Oberg et al, 1967). Development and growth of the secondary cartilage of the condyle has been shown to depend on mechanical factors (Copray et al, 1985a,b; Kantomaa and Hall, 1988; Takano-Yamamoto et al, 1991). Compressive forces can inhibit or activate the growth of the condylar cartilage and process, depending on the degree of force (Barber et al, 1963; Buchner, 1982; Bouvier and Hylander, 1984; Copray et al., 1985b; Tuominen et al, 1994). Type-II collagen if present indicates differentiated chondrocytes(luder etal, 1988; Solursh, 1989). An altered relationship between the condyle and the glenoid fossa has been shown to change type-ii collagen secretion in both the condyle (Salo and Kantomaa, 1993) and the fossa. Increased loading has been shown to decrease amounts of type-ii collagen in the fossa (Pirttiniemi et al, 1994). The aim of this investigation was to measure changes in growth of the glenoid fossa and its articular eminence after decreased loading. Another aim was to evaluate the role of mechanical forces in relation to the existence of a

2 cartilage layer, by determining type-ii collagen secretion. Materials and methods A total of 99 Wistar rats were used. After weaning, 48 animals were fed whole pellets (Hankkija Oy, Finland) and 51 animals were fed ground pellets. Water was freely available. At age 21 days, after weaning, the upper and lower incisors of the group fed ground pellets were shortened by cutting with a wire cutter twice a week. Ten male animals fed whole pellets and males fed ground pellets were injected i.p. with Alizarin red (200mg/kg) at age 22 days and were killed at age 30 days. Eleven female animals fed whole pellets and female animals fed ground pellets were injected at age 30 days. Ten male animals fed whole pellets and male fed ground pellets were injected at age 40 days. All of these animals were killed days after injection. Heads were freed from soft tissue. Zygomatic processes of the squamous temporal bone were cut sagittally at the deepest point of the greatest transversal concavity of the eminence. The glenoid fossae were embedded in plastic (Teknovit 7200; VLC Heraeus Kulzer GmbH). Sagittal sections 0 /an thick were cut. New bone was measured under UV light, microscopically, at 0.5 mm intervals, posteriorly from the extreme anterior point of the articulating surface of the glenoid fossa (Fig. 1). Nine animals fed whole pellets and 11 fed ground pellets were killed at age 23 days and eight animals fed whole pellets and fed ground pellets at age 33 days. The histological sections were used for immunohistochemical studies using collagen II immunostaining. Sections for immunohistochemistry were treated with 0.4% pepsin (Sigma P-7000, 1780 U/mg; Sigma, St Louis, MO) for 1 h at 37 C and stained for type-ii collagen with monoclonal M. TUOMINEN ET AL. antibody (CHD3) made available by Holmdahl (Holmdahl el al, 1986). The antibody was used at x 0 dilution and allowed to react overnight at 4 C. The reaction product was visualized using a Vectastain Elite kit (Vector Laboratories, Burlingame, CA, USA), employing peroxidase and diaminobenzidine substrate. Negative controls were prepared without primary antibody. Sections were counterstained with haematoxylin. The glenoid fossa was divided sagittally into segments of equal sizes. Thicknesses of collagen II layers were measured (Fig. 2). Multivariate analysis of variance was used to determine significances of differences between groups. Student's r-test was used to determine the significances of differences at each point of measurement. Results The weight of the 30- and 40-day-old groups fed ground pellets was same as that of the controls. The weight of the 50-day-old group fed ground pellets was non-significantly less than that of the control. Bone growth decreased in the glenoid fossae of the group fed ground pellets. The effect was most marked in the 30-day-old group (P< in segments III and V, P<0.01 in segment II) (Figs 3 and 6). It was less marked in the 40-dayold group (P< 0.01) (Fig. 4). A similar tendency was evident in the 50-day-old group except in the most anterior part, where the bone growth was increased (Figs 5 and 6). When total bone growth was compared, there was a significant difference (multivariate analysis of variance P< 0.001) between the animals fed ground pellets and animals fed whole pellets. Bone growth was greatest in animals fed whole pellets. Immunohistochemical analysis revealed significantly more anti-collagen II staining in the glenoid fossae of the animals fed whole pellets i n in IV Figure 1 Sagittal segmentation of the glenoid fossa used to allow anteroposterior comparisons in growth examinations. Anterior at left. I II III IV VI Figure 2 Sagittal segmentation of the glenoid fossa used to allow anteroposterior comparisons in immunohistochemical examinations. Anterior at left.

3 EFFECT OF LOADING ON GLENOID FOSSA GROWTH _ 8 o 6 n c 4 ^ *** p < * p > 0.01 III IV V * Control Segments ol the eminence Experimental Figure 3 Growth of articulating surface of the glenoid fossa in the animals fed ground pellets (experimental) and whole pellets (control) after injection of Alizarin red (30-day-old rats) '1 r ** p > 0.01 IV V Figure 4 Growth of articulating surface of the glenoid fossa in the animals fed ground pellets (experimental) and whole pellets (control) after injection of Alizarin red (40-day-old rats).. o 6 III IV V Control Experimental Figure 5 Growth of articulating surface of the glenoid fossa in the animals fed ground pellets (experimental) and whole pellets (control) after injection of Alizarin red (50-day-old rate). (P<0.001). The increase was greatest in the anterior (P<0.001) and posterior (/><0.001) parts of the fossa in the 23-day-old group, and in the posterior part of the fossae (P< 0.001) in the 33-day-old group (Figs 7-9). Discussion To investigate the roles played by mechanical factors in growth of the glenoid fossa, loading on the fossa was increased and decreased (Hinton, 1985; Pirttiniemi et al., 1987). In the study reported, feeding ground pellets reduced forces exerted on the fossa during mastication. Mastication is of shorter duration when rats are fed a soft diet (Hiiemae and Ardran, 1968) and the masticatory muscles are smaller. Forces produced by contraction of smaller masticatory muscles are presumably less than those produced by larger masticatory muscles (Moore 1965). The positions of the condyle in the fossa are different during mastication and during incision in rodents. The lower jaw protrudes during incision and the condyle occupies a more posterior position on the flat articular surface during mastication (Weijs, 1975). Cutting of the incisors lessens protrusion of the mandible and loading on the anterior part of the articulating surface decreases (Hinton and Carlson, 1986). According to Simon (1977) and Hinton and Carlson (1986), decreasing incision reduces compressive forces at the mandibular joints, because there are greater compressive forces on the joint during incising than during mastication (Brehnan et al., 1981). In this study, growth of the glenoid fossa was observed by means of vital staining to allow specific evaluation of changes. The dose of Alizarin red injected has no inhibitory effect on growth of bone in animals (Cleall et al, 1964). Growth of the glenoid fossa was less in animals fed ground pellets than in animals fed whole pellets. The condylar process exhibited a different response to decreased loading in a previous experiment, in which lessening of load increased condylar growth (Tuominen et al., 1994). The differences observed cannot be explained convincingly on the basis of existing knowledge and we can only speculate in the light of earlier observations as to the reactions of secondary cartilage to mechanical manipulation. Secondary cartilage grows differently when subjected to different pressures (Copray et al.,

4 M. TUOMINEN ET AL. ««o f Control 6 Control Experimental Exporlrnentsi I II * * «p < III IV V III VI * * p < p > 0.01 IV V VI Figure 7 Thickness of type-ii collagen layer in 23-day-old rats fed ground pellets (experimental) and 23-day-old rats fed whole pellets (control). Figure 8 Thickness of the type-ii collagen layer in 33-dayold rats fed ground pellets (experimental) and 33-day-old rats fed whole pellets (control). 1985a,b). If the amount of the secondary cartilage is a determinant in these reactions it is possible that optimal pressures for growth in the condyle and the fossa are different since there is less secondary cartilage in the fossa than in the condylar process. Epker and Frost (1965) found that mechan- Figure 6 Sagittal sections of glenoid fossa of 30-day-old rats (A, B) and 50-day-old rats (C, D); Anterior at left. The new bone is seen as green beneath the yellow older bone. At age 30 days growth of the articulating surface after injection of Alizarin Red in an animal fed whole pellets (A) is greater than that in an animal fed ground pellets (B). At age 50 days growth of the articulating surface after injection of Alizarin Red in an animal fed whole pellets (C) is less in the most anterior part of the glenoid fossa than that in an animal fed ground pellets (D).

5 EFFECT OF LOADING ON GLENOID FOSSA GROWTH 0.6mm Figure 9 Type-II collagen immunostaining of glenoid fossa in 33-day-old rats. Anterior at left (A) Animal fed whole pellets. (B) Animal fed ground pellets. Immunohistochemical analysis revealed more anti-collagen II staining in the glenoid fossa of the animals fed whole pelkts. 0.6mm

6 8 M. TUOMINEN ET AL. ical force causes cortical surfaces to deform. The change in curvature results in deposition. According to this concept, in the experiment described here, when loading was decreased by feeding the animals ground pellets, decreased formation of bone should have followed. In this study the articular eminence grew more anteriorly at 50 days in the group fed ground pellets. We have previously found that the articular eminence is located more inferiorly in rabbits fed ground pellets than in rabbits fed whole pellets (Tuominen et al., 1993). Cartilage cells are most often evident on the crest of the articular eminence (Mahan, 1980; Pirttiniemi et al, 1994). The most anterior part of the articulating surface of the glenoid fossa could resemble the posterior region of the condyle, which is subject to intermittent mechanical force. Oberg et al. (1967, 1969) studied cell proliferation and matrix formation and found similarities between the condyle and the anterior border of the fossa. They could therefore react to decreased loading similarly. Amounts of type-ii collagen decreased in the group fed ground pellets. In in vitro studies, chondrogenesis has been shown to depend on cell shape and density (Umansky, 1966; Solursh, 1989). When loading was decreased in this study, it could have reduced cell density and affected cell shape. Chondrogenesis might therefore have been decreased. The amount of type-ii collagen increased most markedly in the posterior part of the glenoid fossa, the area that had less contact during jaw movements than the other parts. Type-II collagen has a cross-linked fibrillar structure. It can resist shearing forces that tend to tear the cartilage apart (Horton et al., 1992). During biting, the condyle moves anteriorly with the disc. The posterior band of the disc attached to the posterior wall of the glenoid fossa stretches and contracts (McDevitt, 1989). The related forces could have increased the amounts of type-ii collagen posteriorly at age 33 days in animals fed whole pellets compared with animals fed ground pellets and whose incisors were cut to lessen mandibular protrusion. Growth of the articulating surface of the temporal component of the temporomandibular joint therefore seems to depend on mechanical factors, such as the condyle. The underlying mechanics seem likely to be different. The presence of type-ii collagen is obviously not regulated only by compressive forces but probably also by tension loading. Address for correspondence Tuomo Kantomaa Institute of Dentistry University of Oulu Aapistie 3 SF Oulu Finland References Barber C G, Green L J, Cox G J 1963 Effects of the physical consistency of the diet on the condylar growth of the rat mandible. Journal of Dental Research 42: Bouvier M, Hylander W L 1984 The effect of dietary consistency on gross and histologic morphology in the craniofacial region of young rats. American Journal of Anatomy 170: Brehnan K, Boyd R L, Laskin J, Gibbs C H, Mahan P 1981 Direct measurement of loads at the temporomandibular joint in Macaca arctoides. Journal of Dental Research 60: Buchner R 1982 Induced growth of the mandibular condyle in the rat. Journal of Oral Rehabilitation 9: 7-22 Cleall J F, Perkins R E, Gilda J E 1964 Bone marking agents for the longitudinal study of growth in animals. Archives of Oral Biology 9: Copray J C, Jansen H W, Duterloo H S 1985a Effects of compressive forces on proliferation and matrix synthesis in mandibular condylar cartilage of the rat in vitro. Archives of Oral Biology 30: Copray J C, Jansen H W, Duterloo H S 1985b An in vitro system for studying the effect of variable compressive forces on the mandibular condylar cartilage of the rat. Archives of Oral Biology 30: Epker B N, Frost H M 1965 Correlation of bone resorption and formation with the physical behavior of loaded bone. Journal of Dental Research 44: Folke L, Stallard R 1967 Cellular kinetics within the mandibular joint. Acta Odontologies Scandinavica 25: Hall B K Genetic and epigenetic control of connective tissues in the craniofacial structures. Birth Defects 20: 1-17 Hiiemae K. H, Ardran G M 1968 A cinefluorographic study of mandibular movement during feeding in the rat (Rallus norvegicus). Journal of Zoology 154: Hinton R J 1985 Adaptive response of the articular eminence and mandibular fossa to altered function of the lower jaw: an overview. In: Carlson D S, McNamara J A, Ribbens K A (eds) Developmental aspects of temporomandibular joint disorders. Monograph No. 16, Craniofacial Growth Series, Center for Human Growth and Development, University of Michigan, Ann Arbor, MI, pp

7 EFFECT OF LOADING ON GLENOID FOSSA GROWTH Hinton R J, Carlson D S 1986 Response of the mandibular joint to loss of incisal function in the rat. Acta Anatomica 125: Holmdahl R, Rubin K, Klareskog L, Larsson E, Wigzell H 1986 Characterization of the antibody response in mice with type II collagen-induced arthritis, using monoclonal anti-type II collagen antibodies. Arthritis and Rheumatism 29: Horton W E, Wang L, Bradham D, Precht P, Balarik R 1992 The control of expression of type II collagen: relevance to cartilage disease. DNA and Cell Biology 11: Kantomaa T, Hall B K 1988 Mechanism of adaptation in the mandibular condyle of the mouse. Acta Anatomica 132: Luder H U, Leblond C P, von der Mark 1988 Cellular stages in cartilage formation as revealed by morphometry, radioautography and type II collagen immunostaining of the mandibular condyle from weaning rats. American Journal of Anatomy 182: Mahan P E 1980 Temporomandibular joint in function and pathofunction. In: Solberg W K, Clark T (eds) Temporomandibular joint problems: biologic diagnosis and treatment. Quintessence, Chicago, pp McDevitt W E 1989 Functional anatomy of the masticatory system. Wright, London Moffett B 1968 The temporomandibular joint. In: Sharry J (ed.) Complete denture prosthodontics. McGraw-Hill, New York, pp Moore W J 1965 Masticatory function and skull growth. Journal of Zoology 146: Oberg T, Fajers C-M, Lohmander S, Friberg U 1967 Autoradiographic studies with 3 H-thymine on cell proliferation and differentation in the mandibular joint of guinea pigs. Odontologisk Revy 4: Oberg T, Fajers C-M, Friberg U, Lohmander S 1969 Collagen formation and growth in the mandibular joint of the guinea pig as revealed by autoradiography with 3 H-proline. Acta Odontologica Scandinavica 27: Pirttiniemi P, Kantomaa T, Tuominen M 1987 Associations between the location of the glenoid fossa and its remodeling: an experimental study in the rabbit. Acta Odontologica Scandinavica 49: Pirttiniemi P, Kantomaa T, Tuominen M, Salo T 1994 Articular disc and eminence modeling after experimental relocation of the glenoid fossa in growing rabbits. Journal of Dental Research 73: Salo L, Kantomaa T 1993 Type II collagen expression in the mandibular condyle during growth adaptation: an experimental study in the rabbit. Calcified Tissue International 52: Scott J H 1955 Growth changes in the glenoid fossa. Dental Practitioner 6: Simon M R 1977 The role of compressive forces in the normal maturation of the condylar cartilage in the rat. Acta Anatomica 97: Solursh M 1989 Extracellular matrix and cell surface as determinants of connective tissue differentiation. American Journal of Medical Genetics 34: Takano-Yamamoto T, Soma S, Nakagawa K, Kobayashi Y, Kawakami M, Sakuda M 1991 Comparison of the effects of hydrostatic compressive force on glycosaminoglycan synthesis and proliferation in rabbit chondrocytes from mandibular condylar cartilage, nasal septum, and sphenooccipital syncondrosis in vitro. American Journal of Orthodontics and Dentofacial Orthopedics 99: Tuominen M, Kantomaa T, Pirttiniemi P 1993 Effect of food consistency on the shape of the articular eminence and the mandible. Acta Odontologica Scandinavica 51: Tuominen M, Kantomaa T, Pirttinemi P 1994 Effect of altered loading on the condylar growth in the rat. Acta Odontologica Scandinavica 52: Umansky R 1966 The effect of cell population density on the developmental fate of reaggregating mouse limb bud mesenchyme. Developmental Biology 13: Weijs W A 1975 Mandibular movements of the albino rat during feeding. Journal of Morphology 145: Wright D M, Moffett B C 1974 The postnatal development of the human temporomandibular joint. American Journal of Anatomy 141: