Induced connective tissue metabolism in vivo: reutilization of pre-existing collagen

Wound healing in the tissues of the periodontium following periradicular surgery. 2. The dissectional wound

Wound healing responses of the tissues of the periodontium following periradicular surgery in rhesus monkeys were evaluated by light microscopy. Part II of this investigation reports the responses of mucoperiosteal and osseous tissues to blunt dissectional wounding resulting from the reflection of triangular or submarginal rectangular flaps. Healing of the dissectional wound is rapid, although slower than the incisional wound. Granulation tissues replaces the fibrin clot in the wound site as early as 4 days after surgery, and is replaced by fibrous connective tissue by 14 days. Minimal differences were found in the temporal and qualitative dissectional wound-healing responses to the two types of flap designs. The periosteum does not survive the flap reflection procedure. The cells of the cambium layer are destroyed and the collagen of the fibrous layer undergoes depolymerization. It is postulated that the depolymerized periosteal collagen plays a role in rapid reattachment of flapped tissues to cortical bone.

Healing of surgical wounds in oral mucoperiosteal tissues

This report provides a review of the major biological events that occur in the oral mucoperiosteal tissues following simple surgical wounding. The chronological sequence and interrelationships of mucoperiosteal tissue wound healing responses are described. The objectives of this review are to provide clarification of wound healing terminology and a basic reference source for further investigative research into the wound healing responses to endodontic surgery.

Collagen alteration in medial collateral ligament healing in a rabbit model

The purpose of this study was to evaluate changes over time in surgically ruptured medial collateral ligament (MCL) with respect to collagen synthesis, collagen degradation and collagen type. Our method involved prelabeling collagen in growing rabbits using 3H-proline followed by surgical injury to the MCL. Animals were sacrificed at intervals up to 40 weeks post-injury. At each time point total hydroxyproline, changes in collagen mass, and collagen synthesis and degradation were determined and related to the unruptured control MCL. A separate semiquantitative determination of collagen type was also performed on the midsubstance of each healing and control ligament. Results showed an increase in total collagen mass and a decrease in collagen concentration in all healing ligaments. Concommitantly, an increase in the collagen turnover rate was observed. Relative turnover was greatest at 3 to 6 weeks after injury and returned toward the normal rate by 40 weeks. Type I collagen was partially replaced by type III, probably as a result of increased synthesis during scar formation. The mechanism for collagen remodeling (replacement of mass and concentration in an organized fashion) in untreated rabbit MCL scar appears functional by virtue of its chronicity but, due to a shift in collagen type, it may also be qualitatively inadequate.

Collagen formation during the healing of colonic anastomoses

To study new collagen formation in the healing of anastomoses in the right colon, five male Sprague-Dawley rats had single-layer colonic anastomosis performed. Five additional rats had suture of the colon with interrupted sutures without transection of the colon. Ten animals served as controls. One week after surgery, animals were given 3H-proline repeatedly to label new collagen formation during the second and third weeks. Animals were sacrificed three weeks after suturing or anastomosis. Two- or 10-mm segments were precisely excised on either side of the suturing or anastomoses. Total collagen and its total radioactivity were measured per segment. Collagen hydroxyproline and its radioactivity increased (100 per cent) only within 1 cm of the anastomosis or suture alone. No local or distant decrease in collagen was observed. Collagen formation in colonic wounds appears to be a local process.

Root surface--soft tissue interface. Part I: A review

A review of the literature is presented with regards to the soft tissue-root surface interface. The basic biological aspects are discussed followed by reports on healing after periodontal surgery. The effect of citric acid, to enhance new attachment, is reviewed in detail. Articles reporting on clinical findings, ultrastructural observation (TEM and SEM), and light microscopic studies have been selected to present the reader with a logical overview of what has been reported in the literature.

Collagen degradation in rat skin but not in intestine during rapid growth: effect on collagen types I and III from skin

Metabolic degradation of prelabeled collagen in whole body skin and whole intestine was compared to that of types I and III collagens from skin in young, rapidly growing rats. Pregnant rats were given [3H]proline during the last week of gestation; and after birth, littermates were compared. Between the second and sixth weeks of age, there was a 43% loss of radioactivity from dermal collagen but no significant loss of radioactivity from intestinal collagen. Pepsin treatment solubilized 90% of the dermal collagen but only 12% of intestinal collagen. Skin from 2- and 6-week-old rats yielded the same proportions of type I and type III collagens (type I, 82%; type III, 18%). The relative losses of total radioactivity from types I and III were similar to each other (50 and 44%, respectively) and to the loss from whole skin. Because types I and III collagens are known to be present in both skin and intestine, the marked degradation of both collagen types in skin but not in the intestine may be related to the amount and kind of intermolecular crosslinks present.

Comparison of whole calvarial bones and long bones during early growth in rats. II. Turnover of calcified and uncalcified collagen masses

The increase of total collagen and its destruction were compared for whole calvaria and long bones from young growing rats prelabeled in utero with 3H-L-proline. Rats were compared from birth to 16 weeks of age. Long bones and calvaria were isolated as intact anatomical units for autoradiography or separated by collagenase into calified and uncalcified collagens. Autoradiography using 14C-L-proline demonstrated eccentric modeling of bone collagen. With growth the mass of calcified collagen (bone) increased rapidly in calvaria and long bones. A similar increase in the mass of uncalcified collagen (mainly cartilage) occured in the long bones; a very small increase occurred in the fibrous tissue of calvaria. Total and specific radioactivities of collagens at each age were compared to that present at birth. With growth remodeling an almost complete loss of pre-existing radioactive collagen occurred from uncalcified fibrous tissue of calvaria as compared to a smaller but substantial loss from the uncalcified cartilage of long bones. A marked loss of calcifed collagen occurred in long bones as compared to a smaller loss from calvarial bones. The istopic data indicate a large turnover of fibrous tissue (type I collagen) with growth remodeling as compared to a smaller turnover of bone (calcified, type I collagen) and cartilage (typc I collagen). The turnover rate of skeletal collagens depends upon whether the collagen is calcified or not, and not upon the type of collagen.

Effect of a dorsal dermal surgical wound on the chemical response of rat abdominal skin to chronic administration of sodium diphenylhydantoin

A dorsal dermal surgical wound inflicted five days before excision of abdominal skin from young rats that were under treatment with daily injections of sodium diphenylhydantoin (100 or 50 mg/ kg) greatly modified the dermal chemical response to this drug that was observed in unwounded animals. Sodium diphenylhydantoin failed to increase wound rupture strength.

Reversible transformation of fibrous collagen to a soluble state in vivo

Metabolic pathways of pre-existing and newly synthesized collagen fractions from skin and induced connective tissue were studied in rats that had been labeled with (3)H-L-proline 6 and 20 weeks previously. The distribution of specific radioactivity was determined for soluble and insoluble collagens. Multiple extractions of neutral salt-soluble and citrate-soluble collagen demonstrated constant specific radioactivities which indicated the achievement of an isotopic steady state. Citrate-soluble collagen was four times more radioactive than neutral salt-soluble collagen, which indicated a large difference in biological age (months) between fractions. Different levels of specific radioactivity in collagen fractions from implanted sponge indicated that both pre-existing (citrate-soluble) and newly synthesized collagen (salt-soluble) contributed to the insoluble collagen of induced connective tissue in normal and hypophysectomized rats. The isotopic data indicated that pre-existing fibrous collagen could be solubilized in vivo and translocated from skin to sponge via citrate-soluble collagen.

The quantitative relationship of urinary peptide hydroxyproline excretion to collagen degradation

To determine the quantitative relationship of urinary hydroxyproline peptide excretion to collagen breakdown, known quantities of radioactive hydroxyproline peptides were administered to unlabeled animals and excertion of radioactivity in respiratory carbon dioxide, urine, and feces was measured. The major routes of excretion of collagen peptide metabolites were respiratory carbon dioxide (75%) and urine, as hydroxyproline-containing peptides (25%). Since the predominant urine hydroxyproline peptide linkage is proly-hydroxyproline, L-prolyl-L-hydroxyproline-(3)H was administered to unlabeled animals. Greater than 80% of the administered dipeptide was excreted in urine, suggesting that this peptide linkage is not hydrolyzed to a significant extent in vivo. These data suggest that urinary hydroxyproline excretion is a "fairly" sensitive indicator of collagen breakdown and can be used at the clinical level to quantitate changes in collagen breakdown.