English translation : granulation tissue

Inflammatory reaction and granulation tissue
Dr Maxime Battistella,
Hosp St-Louis and University Paris Diderot
october 2011

A 40-year-old man, with no past medical history, hurts his finger with a screwdriver while fixing a shelf in his kitchen.

The screwdriver creates a cutaneous wound (an ulceration). This wound is equivalent to an "injury" of the tissue.

This physical stimulus will activate successive reactive phenomenon in the tissue. This succession of tissue reactions is known as the inflammatory reaction.  Other types of injurious trigger can engender an inflammatory reaction : chemical, infectious, thermal ...
Inflammation has been known clinically since Antiquity. In 30 BC, Celse described it as the association of 4 signs :

Redness (Rubor)      -     Local warmth (Calor)       -     Swelling   (Tumor)      -      Pain (Dolor)

Question 1:

What are the tissular and/or molecular mechanisms underlying the occurence of each of these 4 clinical signs ?

The 4 signs of inflammation correspond to the first phase of the acute  inflammatory reaction :
-The vascular exudative phase:
- vasodilation
- vascular leakage: increased permeability of the microvasculature and exudation
- leukocyte extravasation: margination, rolling and adhesion to the endothelium. Transmigration across the endothelium. Migration in interstitial tissue by chemotaxis.

Question 2 :
In which order are recruited the different types of leukocytes from the circulating blood to the inflammatory infiltrate ?

We theoretically divide the continuation of the inflammatory reaction in 3 phases (after the vascular exudative phase) :

- the cellular phase : infiltration with diverse types of cells coming from
- the blood : neutrophils, monocytes, lymphocytes
- the local connective tissue : fibroblasts, endothelial cells, resident histiocytes.
- the detersion phase : Phagocytosis by macrophages and neutrophils tends to eliminate all injurious particles
           - exogenous particles : bacterias, foreign bodies
           - endogenous particles : cellular debris (pus, necrosis), exudate

- the healing phase :
reconstitution of the connective tissue that has been destroyed by the injurious stimulus and during acute inflammation

These 3 phases are not mutually exclusive in time and space. They can coexist in different areas of one lesion.

Under the microscope,  the different phases of inflammation and healing are organized spatially in the granulation tissue.

Let's come back to our patient. He did not take care of his wound, and continued to work. He did not protect the wound and exposed it to repeated trauma.

Clinically : During the first 48 hours, the wound filled with a red tissue protruding above the level of the surrounding skin.  (see Image below).

There is an excessive amount of granulation tissue that blocks re-epithelialization. This has been called exuberant granulation (or proud flesh). It is favored by repeated trauma, especially on the fingers.

Histopathology :

Let's see the slide of an example of exuberant granulation :  virtual slide 1

(On this slide, epidermis is downwards and deep dermis upwards)

- The lateral epidermis is thinned

- there is a central ulceration : the epidermis is replaced by a fibrino-leukocytic exudate.

- Under the ulceration, there is extensive granulation tissue. Capillaries are numerous, lying in a loose edematous connective tissue, infiltrated by neutrophils, lymphocytes and histiocytes.

- deeper, one can see fibrosis with rare inflammatory cells.

Question 3 :

Virtual slide 1 has 6 annotated areas. What do they contain ? (one or more answers)

Area A :                                                                            Area B :
    a- dilated capillaries                                                       a- lymphocytes
    b- fibrin deposits  
                                                          b- neutrophils
    c- neutrophils                                                                 c- histiocytes
    d- normal epidermis                                                       d- giant cells

Area C :                                                                             Area D :
    a- dilated capillaries                                                       a- necrosis
    b- edematous connective tissue                                       b- fibrin deposits
    c- dense fibrosis                                                            c- protein-rich exudate
    d- necrosis                                                                    d- red blood cells

Area E :                                                                            Zone F :
    a- hyperplastic epidermis                                                a- inflammatory infiltrate
    b- ulcerated epidermis                                                    b- fibrosis
    c- dermis                                                                       c- capillaries
    d- thinned epidermis                                                      d- fat tissue

Later, exuberant granulation can evolve more chronically as seen on virtual slide 2.

Question 4 :

What are the main differences between virtual slide 1 and virtual slide 2 ?

Last modified: Tuesday, 7 August 2012, 10:32 AM