Regeneration healing (repair)-General Pathology Lecture note

Objectives of this Post

• Review the normal physiology and concepts of cell proliferation, cell growth, cell “cycle”, and cell differentiation
• Understand the basic factors of tissue regeneration
• Understand the relationships between cells and their extracellular matrix (eECM)
• Understand the roles of the major players of healing---angiogenesis, growth factors (GFS), and fibrosis
• Differentiate 1st & 2nd intention healing

Definitions:

Regeneration: growth of cells to replace lost tissues

Healing: a reparative tissue response to a wound, inflammation or necrosis, often leads to fibrosis 

Granulation tissue 

“Organizing” inflamation

Regeneration

• Replacement of lost structures
• Is dependent on the type of normal turnover the original tissue has
• Can be differentiated from “compensatory” growth

Healing (repair)

• Needs a wound, inflammatory process, or necrosis
• Many disease appearances anatomically are the result of “healing” such as atherosclerosis
• Often ends with a scar
• Fibrosis, as one of the 3 possible outcomes of inflammation, follows “healing”
• Requires a connective tissue “scaffold”
• Fibrosis occurs in proportion to the damage of the ECM

 

Cell population fates

Proliferation

• Hormonal, especially steroid hormones
• Eg., EPO, CSF

Differentiation*

• Unidirectional, gain and loss

Apoptosis

*One of the most key concepts in neoplasia

• Ectoderm
• Mesoderm
• Entoderm

Cell cycle

G0

Quiescent (not a very long or dominent phase)

G1

Pre-synthetic, but cell growth taking place

S

• Cells which have continuous “turnover” have longer, or larger s-phases, i.e., dna synthesis
• S-phase of tumor cells can be prognostic

G2

Pre-mitotic

M (mitotic:, P,M,A,T cytokinesis)

Cell types

Labile: eg. marrow, GI

Quiescent: liver, kidney

Non-mitotic: neuron, striated muscle

Stem cells (totipotential*)

1. Embryonic
2. Adult

Embryonic stem cells

• Differentiation
• Knockout mice (mice raised with specific gene defects)
• Repopulation of damaged tissues, in research

Adult Stem cells

Marrow (hemocytoblast)

(hematopoetic stem cells)

Non-marrow (reserve)

Marrow stromal cell

Adult tissue differentiation and regeneration parallels embryonic development

Growth factors (GFS)

Polypeptides

Cytokines

• Locomotion
• Contractility
• Differentiation
• Angiogenesis

Growth factors (GFS)

Epidermal

Transforming (alpha, beta)

Hepatocyte

Vascular endothelial

Platelet derived

Fibroblast

Keratinocyte

Cytokines (TNF, IL-1, interferons)

Cell players (source and targets)

• Lymphocytes, especially t-cells
• Macrophages
• Platelets
• Endothelial cells
• Fibroblasts
• Keratinocytes
• “mesenchymal” cells
• Smooth muscle cells

E(epidermal) GF

• Made in platelets, macrophages
• Present in saliva, milk, urine, plasma
• Acts on keratinocytes to migrate, divide
• Acts on fibroblasts to produce “granulation” tissue

T(transforming) GF-alpha

• Made in macrophages, t-cells, keratinocytes
• Similar to egf, also effect on hepatocytes

H(hepatocyte) GF

• Made in “mesenchymal” cells
• Proliferation of epithelium, endothelium, hepatocytes
• Effect on cell “motility”

Ve(vascular endothelial) GF

• Made in mesenchymal cells
• Triggered by hypoxia
• Increases vascular permeability
• Mitogenic for endothelial cells
• Key substance in promoting “granulation” tissue

Pd(platelet derived) GF

• Made in platelets, but also many other cell types
• Chemotactic for many cells
• Mitogen for fibroblasts
• Angiogenesis
• Another key player in granulation tissue

F(fibroblast) GF

• Made in many cells
• Chemotactic and mitogenic, for fibroblasts and keratinocytes
• Re-epithelialization
• Angiogenesis, wound contraction
• Hematopoesis
• Cardiac/skeletal (striated) muscle

T(transforming) GF-beta

• Made in many cells
• Chemotactic for PMNS and many other types of cells
• Inhibits epithelial cells
• Fibrogenic
• Anti-inflammatory

K(keratinocyte) GF

• Made in fibroblasts
• Stimulates keratinocytes:
• Migration
• Proliferation
• Differentiation

I (insulin-like) GF-1

• Made in macrophages, fibroblasts
• Stimulates:
• Sulfated proteoglycans
• Collagen
• Keratinocyte migration
• Fibroblast proliferation
• Action similar to gh (pituitary growth hormone)

TNF (tumor necrosis factor)

• Made in macrophages, mast cells, t-cells
• Activates macrophages
• Key influence on other cytokines

Interleukins

• Made in macrophages, mast cells, t-cells, but also many other cells
• Many functions:
• Chemotaxis
• Angiogenesis
• Regulation of other cytokines

Interferons

• Made by lymphocytes, fibroblasts
• Activates macrophages
• Inhibits fibroblasts
• Regulates other cytokines

Signaling

• Autocrine (same cell)
• Paracrine (next door neighbor) (many gfs)
• Endocrine (far away, delivered by blood, steroid hormones)

Transcription factors

Hepatic

Regeneration

• TNF
• IL-6
• HGF

Extracellular matrix (ECM)

• Collagen(s) I-xviii
• Elastin
• Fibrillin
• Cams (cell adhesion molecules)
• Immunoglobulins, cadherins, integrins, selectins
• Proteoglycans
• Hyaluronic acid

ECM

• Maintain cell differentiation
• “scaffolding”
• Establish microenvironment
• Storage of GF’s

1. Collagen one - bone (main component of bone)
2. Collagen two - cartwolage (main component of cartilage)
3. Collagen three - rethreeculate (main component of reticular fibers)
4. Collagen four - floor - forms the basement membrane

Genetic collagen disorders

• I                               osteogenesis imperfecta, e-d
• Ii                              achondrogenesis type ii               
• Iii                             vascular ehlers-danlos
• V                             classical  e-d
• Ix                            stickler syndrome
• Iv                            alport syndrome
• Vi                            bethlem myopathy
• Vii                           dystrophic epidermolysis bullos.
• Ix                            epiphyseal dysplasias
• Xvii         gen. Epidermolysys bullosa
• Xv, xviii knobloch syndrome

Definitions:

Regeneration: growth of cells to replace lost tissues

Healing: a reparative tissue response to a wound, inflammation or necrosis

Healing

• Follows inflammation
• Proliferation and migration of connective tissue cells
• Angiogenesis (neovascularization)
• Collagen, other ecm protein synthesis
• Tissue remodeling
• Wound contraction
• Increase in wound strength (scar = fibrosis)

Angiogenesis (neovascularization)

• From endothelial precursor cells
• From pre-existing vessels
• Stimulated/regulated by gf’s, especially VEGF
• Also regulated by ECM proteins
• AKA, “granulation”, “granulation tissue”, “organization”, “organizing inflammation”

Wound healing

1 intention

Edges lined up

 

2 intention

Edges not lined up

Ergo….

More granulation

More epithelialization

More fibrosis

“Healthy” granulation tissue

Fibrosis/scarring

• Deposition of collagen by fibroblasts
• With time (weeks, months, years?) The collagen becomes more dense, ergo, the tissue becomes “stronger”

Wound retarding factors (local)

• Decreased blood supply
• Denervation
• Local infection
• FB
• Hematoma
• Mechanical stress
• Necrotic tissue

Wound retarding factors (systemic)

• Decreased blood supply
• Age
• Anemia
• Malignancy
• Malnutrition
• Obesity
• Infection
• Organ failure

Maxillary Sinus in Health and Disease-Oral Surgery Lecture

Anatomical facts and location:

√ The largest para-nasal sinuses.

√ Situated in the maxilla.

√ Has pyramidal shape.

√ Lateral nasal bone forms its base.

√ Apex headed towards the zygomatic bone.
√ Canine fossa, orbital floor and hard palate form the pyramidal walls.
√ Communicates with nasal cavity through maxillary ostium, in the posterior end of hitus simlunaris of middle meatus.

Anatomical morphology:

√  Size varies from one person to another.

√  Asymmetry existed in the same individual.

√  Small in children and grows up with aging.

√  Average height is about 3.5 cm, depth 3.2 cm and width 2.5 cm.

√  Capacity of about 15 cc.

√  Divided into several compartments by bony septa (underwood’s septa).

√  Lined with pseduo-stratified columnar ciliary epithelium (schneiderian membrane).

Relation with other structures:

√ Alveolar bone and dentition.

√ Nasal cavity and nasopharynex.

√ Orbital cavity and its contents.

√ Hard palate and oral cavity proper.

√ Pterygomaxillary fissure and its contents.

√ Neurovascular structures including infraorbital and superior alveolar nerve.

Development:

√  Develops from invagination of the mucous membrane of middle meatus of the nasal cavity at about the 3^rd month of intrauterine life.

√  Fully development reaches with the age of 16 years.

√  Loss of permanent teeth and alveolar bone may make the sinus to appear huge in size.

Blood supply:

Blood supply from facial, maxillary, infraorbital, greater and lesser palatine arteries and lateral and posterior nasal branches of sphenopalatine artery.

Venous drainage to the anterior facial vein, sphenopalatine vein and pterygopaltine plexus.

Nerve supply:

√  Infraorbital nerve.

√  Posterior, middle and anterior superior alveolar nerves.

√  Greater and lesser palatine nerves.

Lymphatic drain:

The lymphatic drain of the sinus is through the nose or the submandibular lymph nodes.

Physiology:

Unknown but the following functions have been proposed:

√  Speech and voice resonance.

√  Reduce weight of skull.

√  Warmth inspired air.

√  Filtration of inspired air.

√  Immunologic barrier ( body defense).

Pathology:

1. Congenital anomalies.
2. Inflammatory diseases.
3. Cysts and odontogenic infection.
4. Bone metaplasia and benign tumors.
5. Neoplasia.
6. Trauma.

 

 

Congenital anomalies:

√  Cleft palate.

√  Facial fistula and cleft.

 √ Cystic formation.

√  Atresia.

Inflammatory diseases:

√  Bacterial infection.

√  Bacterial infection secondary to viral infection.

√  Fungal infection.

Sinusitis

Acute sinusitis:

Suppurative or non suppurative inflammation of the mucosal lining of the sinus. It involves one or both sinuses.

Causes:

√  Secondary to hay fever and allergic rhinitis.

√  Secondary to acute rhinitis (common cold) and URT infection.

√  Bacterial infection due to: dental sepsis, swimming and diving, trauma and foreign body dislodgment.

Sings and symptoms:

√  Headache.

√  Pain and tenderness.

√  Nasal obstruction.

√  Nasal discharge.

√  Toxic manifestations.

√  Heavy filling with bending.

√  Nasal congestion.

√  X-ray and transillumination findings.

Treatment:

√  Rest and fluid and mouth hygiene.

√  Antibiotics (C&S); pneumococci and streptococci are the most causative organisms.

√  Analgesics and antihistamines.

√  Local treatment (decongestant and steam inhalation).

 
Chronic sinusitis:

It is a chronic type of infection affected the mucosal lining of one  or both sinuses, resulted in mucopus or pus collection. A polypoidal type of inflammation can lead to formation of multiple or single mucosal polyps. 

Causes:

√  As a consequence of non resolved acute sinusitis.

√  Dental abscesses.

√  Virulent organism with low resistance.

√  Foreign body dislodgement or trauma

Signs and symptoms:

√  Headache.

√  Nasal obstruction

√  Nasal discharge.

√  Fatigue.

√  Hyposmia/ cacosmia.

√  Transllumination findings.

√  Proof puncture.

Treatment:

√  Antibiotics.

√  Systemic decongestants.

√  Sinus wash-out.

Mycotic infection:

Aspergillosis:

Opportunistic infection caused by maxillary sinus flora fungi environment in susceptible individual, leads to obliteration of the sinus space and erosion of its bony components.

Complications of sinusitis:

• Orbital abscess and orbital cellulites.
• Intracranial abscesses.
• Meningitis.
• Cavernous sinus thrombosis.
• Spread of infection to neighboring sinuses, structures and organs.
• Osteomyelitis.
• Gastrointestinal disturbances.

Cysts and odontogenic tumors:

Odontogenic cysts:

√ radicular cysts.

√ residual cysts.

√ dentigerous cysts.

√ premordial cysts.

Non-odontogenic cysts.

Mucocele and retention cysts.

Odontogenic tumors:

√ ameloblastoma.

√  Myxoma.

Bone metaplasia and benign tumors:

√  Fibrous dysplasia.

√  Ossifying fibroma.

√  Transitional papilloma.

√  Osteoma.

√  Giant cell lesions.

Neoplasia:

√  Squamous cell carcinoma.

√  Adenocarcinoma.

√  Sarcoma (osteosarcoma).

√  Ewing’s sarcoma.

Trauma:

√  Tuberosity fracture.

√  Dentoalveolar fracture.

√  LeFort’s fractures.

√  Zygomatic complex fracture.

√  Pure and impure orbital floor fractures.

√  Establishment of oro-antral fistula.

Clinical examination:

Inspection

√ Assess asymmetry.

√ Color of overlaying skin.

Palpation

√  Tenderness.

√  Swelling and expansion.

√  Depression.

Examination of nasal passage

√ Nasal patency.

√ Pus discharge.

√ Nasal polyps.

√ Erythema, redness, change in the color of nasal mucosa.

Transillumination 

Diagnostic sinus lavage

√ sinus rinsing through the canine fosaa.

√ Nasal antrostomy.

Radiographical examination:

Routine radiographical examination

√ Orthopantomogram (OPG)

√ Occipitomental (water’s view), with lateral tilt.

 

Special investigation and radiographical examination

• Sinuscopy
• Sinogram
• CT scan
• MRI
• Microbiology and histological examination:
• Culture and sensitivity and biopsy.

Diagnosis and Management of Hemorrhage in Oral Surgery

What is meant by Hemorrhage ?

Prolonged or uncontrolled bleeding is often referred to as hemorrhage.

The amount of blood lost as a result of hemorrhage can range from minimal to significant quantities.

Hemorrhage in Surgery

Hemorrhage  can occur to a greater or lesser degree during all surgical procedures and it’s management depends upon whether the patient is hematologically normal or suffers from some disturbance in the normal clotting mechanism.

The overwhelming majority of patients who undergo oral surgical procedures are those who have normal haemostatic mechanism.

Therefore, significant or major hemorrhages are not that common in oral surgery except in patients who have a bleeding / clotting disorder or those who are on anticoagulants.

However, uncontrolled and persistent bleeding can occur in some healthy patients after dental extraction.

Therefore, it is still important to achieve proper hemostasis in all patients during oral surgical procedures, so as to prevent excessive post-operative blood loss.

Normal Mechanism of Hemostasis

Hemostasis is a complicated process.

It involves a number of events

Hemostasis - Normal Mechanism

1.  Vascular phase

2.  Platelet phase

3.  Coagulation phase

Vascular phase

When a blood vessel is damaged, vasoconstriction results.

Platelet phase

Platelets adhere to the damaged surface an form a temporary plug.

Through two separate pathways, the Intrinsic and Extrinsic, the conversion of fibrinogen to fibrin is complete. Fibrin tightly binds the platelets to form a clot

Coagulation phase

The clotting mechanism

Hemostasis

Dependent upon:

• Vessel Wall Integrity 
• Adequate Numbers of Platelets 
• Proper Functioning Platelets 
• Adequate Levels of Clotting Factors 
• Proper Function of Fibrinolytic Pathway

Hemorrhage in Oral Surgery

Hemorrhage following Oral Surgical procedures can occur due to local or systemic causes.

In healthy patients the postoperative bleeding is mainly due to local causes.

Local causes of hemorrhage in oral surgery

Local causes of hemorrhage originate in either soft tissue or bone.

Local causes of hemorrhage in oral surgery –Soft tissue bleeding

Soft tissue bleeding is either arterial, venous, or capillary in nature.

Arterial bleeding is bright red and spurting in nature.

Arteries in the soft tissues at risk during oral surgical procedures are the lies posterior portion of hard palate) greater palatine artery and the buccal artery (lies lateral to the retromolar pad)

Venous blood is dark red in color and flows steadily and heavily especially if the vein is large.

Capillary bleeding is bright red in color and is more of a minimal ooze.

Local causes – Osseous (Bony) bleeding in oral surgery

Troublesome bone bleeding originates either from nutrient canals in the alveolar region, central vessels, such as the inferior alveolar artery, or from central vascular lesions (Hemangioma or Vascular malformation)

Systemic causes of hemorrhage in oral surgery

Some patients with heriditary conditions such as hemophilia, Von Willebrand’s disease are susceptible for hemorrhage following oral surgical procedures.

Patients with thrombocytopenia (decreased platelet count) , Leukemia e.t.c., are also at risk of prolonged bleeding after surgery.

Patients with uncontrolled hypertension.

Patients with H/O prosthetic heart valve replacement, Stroke (Cerebrovascular accident) e.t.c., take oral anticoagulants like Aspirin or Warfarin to prevent the occurrence of a thromboembolic episode.

These patients are also at risk of prolonged severe bleeding during and after an oral surgical procedure.

Types of Hemorrhage - Primary Hemorrhage

This occurs during the surgery, as a result of injury like cutting or laceration of the  artery or bleeding from bone.

This also occurs when surgery is done in an infected area with a lot of granulation tissue.

It can also occur after a very short period of time  immediately after surgery.

This type of bleeding is really normal and can be controlled easily.

Types of Hemorrhage - Intermediate / Reactionary Hemorrhage

This type of bleeding occurs within a few hours after surgery.

This type of bleeding occurs as a result of failure of coagulation to occur (as in patients with systemic bleeding problems or those on anticoagulants)

Patients who have unknowingly disturbed / dislodged the clot are also prone for this type of bleeding.

Types of Hemorrhage - Secondary Hemorrhage

This occurs after 7 to 10 days after surgery. This is mainly due to partial division of blood vessel in combination with infection of the wound (Like patient’s who undergo radical neck dissection e.t.c.,).

This type of bleeding is not very frequently encountered after oral surgery procedures.

Management of Primary Hemorrhage in Normal patients

The management of bleeding during surgery (Primary bleeding) can be achieved by the following means,

• Securing / ligation of blood vessels with silk sutures. 
• Use of pressure swab to achieve hemostasis. 
• Use of electrocautery to achieve hemostasis. 
• Use of hemostatic agents like bone wax, surgicel,e.t.c., 
• Hypotensive anaesthesia (G.A) and use of vasoconstrictors in L.A.

Local Measures  ( Synthetic Materials)

There are several materials that are commercially available that are used  locally for achieving adequate hemostasis.

Local Measures: Surgicel (Oxidised Regenerated Cellulose)

Local measures: Gelfoam with activated thrombin

Local Measures: Avitene (Microfibrillar Collagen)

Local Measures: Etik Collagen (Packed collagen)

Local Measures: Tranexamic acid 5%

Local Measures: Tranexamic acid 5% in Syringe

Local Measures: Irrigation of wound with Tranexamic acid

Local Measures: Suturing the wound

Local Measures: Pressure with oral packs

Management of Intermediate Hemorrhage in  Normal patients

The management of bleeding that occurs immediately after surgery (Reactionary bleeding) involves proper examination of the surgical wound to identify the site of bleeding (i.e ) from bone or soft tissue.

If bleeding is from bone then the hemostatic agents like bone wax or gelfoam is usually used.

If bleeding is from soft tissues then, ligation / cauterization of blood vessels along with the use of hemostatic agents like surgicel and suturing of the wound is carried out.

Management of Secondary Hemorrhage in  Normal patients

The management of this type of bleeding that occurs a few days after surgery involves the removal of any debris from the wound surface that promotes the infection of the wound.

Identify the source of bleeding and treat as would be done in a  patient with secondary bleeding.

Surgical stents can be placed over extraction sockets for stabilization of clot and prevention of  wound contamination.

Management of Hemorrhage in patients with  bleeding disorders / and those on anticoagulant therapy

The usual protocol involved in the treatment of this group of patients consists of pre-operative blood investigations and preoperative correction of the underlying deficiency (Replacement of Clotting factors / platelets) if any in these patients.

Subsequently, after this appropriate local measures are used to decrease the chances of post-operative bleeding.

 

Laboratory evaluation

• Platelet count 
• Bleeding time (bt) 
• Prothrombin time (pt) 
• Partial thromboplastin time (ptt) 
• Thrombin time (tt)

Platelet count

Normal  100,000 - 400,000 cells/mm³ 

< 100,000            Thrombocytopenia

50,000 - 100,000 Mild Thrombocytopenia

< 50,000              Severe Thrombocytopenia

                       

Bleeding time

Provides assessment of platelet count and function

Normal value

2-8 MINUTES

Prothrombin time

Measures Effectiveness of the Extrinsic Pathway

Normal value

10-15 SECS

Partial thromboplastin time

Measures Effectiveness of the Intrinsic Pathway

Normal value

25-40 SECS

Thrombin time

Time for Thrombin To Convert  Fibrinogen to Fibrin

A Measure of Fibrinolytic Pathway

Normal value

9-13 SECS

Management of Hemorrhage in patients with uncontrolled hypertension.

This group of patients need appropriate medical consultation for initiation of medical treatment to decrease their Blood Pressure.

Thus once their B.P is controlled, then the bleeding decreases and with local measures the hemorrhage is controlled.