WELCOME TO MINOR CREDIT SEMINAR
Molecular Mechanism Of Cervical Ripening in Ruminants
Dr Rouf RashidROLL NO: M-5606
MVSC scholar Animal Reproducion
division
Introduction Stages of cervical remodelling Factors involved in cervical remodelling Role of MMPs Conclusion
Overview
predominantly of
connective tissue
small amounts of smooth muscle tissue presents
cervix is a fibrous organ
thick wall and
constricted lumen
(Leppert 1995).
Introduction
Cervix also having same 3 layers stromal layer more predominant
Mucosal layer:
consisting of
epithelium and
underlying stroma
Serosal layer:
outer most
Muscular layer:
consist of inner
circular & outer
longitudinal
HISTOLOGY OF FEMALE GENITAL TRACT
Cross sectional view of the bovinecervix
3: Cervical lumen with protruding annular rings
4: Epithelial and superficial stromal layer
5: Deep stromal layer 6:Outer muscular layer 7: Serosa
Connective tissue
Ground substance Proteoglycan• Hyalurunic acid,• Chondroitin-4,6
sulfate,• Dermatan sulfate,• Heparan sulfate,&• Keratan sulfate Glycosaminoglycans Fibrillar collagen Matricellular
proteins
Fibrous constituents-
Collagen
Elastin
Reticulin
Cellular elements-
Mast cells
Fibroblasts
Wandering cells
Cervical stroma
I. Gradual ripening- last months ( cervical softening )
II. Final ripening- parturition ( cervical ripening and cervical dilatation)
Gradual cervical ripening-
Clinically - palpable softening
Biochemically – water imbibition, separation of collagen bundles collagen denaturation
Collagen denaturation - cervical MMPs (van Engelen2008)
Cervical Remodelling- 2 stages
Final cervical ripening
Just before and during cervical dilatation.
Collagen fibrils are denatured and digested by matrix metallo proteinases as a part of inflammatory cascade
Cervical softening
Cervical ripening
First measurable increase in tissue distensibility when compared with non pregnant cervix ( Read et al . 2007 )
High P4/E2 ratio
Changes in the ratio of type 1 to type 3 collagen , alteration in post transcriptional processing of collagen monomers and assembly of collagen monomers into collagen fibrils can affect collagen structure and its mechanical strength (Lieu et al. 1997 )
Increase in collagen solubility with no change in total collagen content
Cervical softening
Evidence of downregulation of specific steps in the collagen processing pathway icclude folowing
(a) Decline in cervical expression and activity of lysyl hydroxylase(LH) and lysyl oxidase (LOX) respectively in early pregnancy ( Akins et al . 2011 )
(b) subsequent decline in collagen containing the stronger pyridinoline cross links in second half of gestation
(c) Collagen turnover appears upregulated during the pregnancy but the total collagen content remains constant throughout pregnancy
(d) MMP activity not reported in this phase
(e) Constant breakdown of collagen to maintain steady collagen levels and facilitate replacement of mature by poorly cross linked collagen fibre
Matricellular Proteins
Thrombospondin 2 (thbs2) and tenascin 2 (Tns) proteins are down regulated in early gestation and remain low untill just before birth ( Akins et al . 2011 )
They have a role in cervical softening , through the formation of appropriately assembled collagen fibril and regulate the activity of MMPs , and is a inhibitor of angiogenesis in various tissues ( Kokenyesi et al . 2004 )
Tenascin is upregulated during tissue injury ( postpartum) through proinflammatory and fibrotic responses
Thus replacement of mature cross linked collagen with collagen harbouring reduced cross links with decline in the THBS2 and TNC in the cervix is a key in modulating collagen architecture within ECM during softening
Cervical epithelial
provide immunoprotection and maintenance of a barrier which protect stromal compartment
Trefoil factor 1 (TFF1) is a gastric secreted peptide , protection and restitution of cervical mocosal epithelia ( Read et al . 2007 )
Serine protease inhibitor Kazal type 5 (SPINK5) functions to prevent degredation of desmoglein involved in barrier formation
They are of short duration and very rapid , overlapping each other
Low P4/E2 ratio present
Maximum loss of tissue compliance and structural integrity
Decline in collagen content ( Rajabi et al. 1991 )
Cervical ripening and dilatation
Progressive increase in collagen fibril diametre in the cervix from early to late gestation along with increased spacing between the fibrils ( Akins et al.2011 )
Increased synthesis of glycosaminoglycan and hyaluronan ( HA; Straach et al .2005 )
Proliferation of mucosal epithelia which is dependent on actions of Relaxin and Estrogen ( Lee et al . 2005 )
Epithelium become laden with mucus secreting vacuoles important in immune surveillance and lubrication
Epithelium also expresses steroid 5 α reductase type 1 (SRD5A1) important in local progesterone metabolism ( Mahendroo et al . 1999 )
Loss of p4 function along with increased metabolosim facilitate transition to ripening phase
During ripening the barrier properties of mucosal epithelia , hydration , cell to cell communications are regulated by increased expresion of tight junction proteins (claudin 1 and 2) , aquaporins , gap junction proteins ( connexin 26 and 43 ) , and desmogleins ( Gonzalez et al . 2009 )
Immune cells play a role in ECM remodelling via activation of proinflammatory signals and the release of MMPs that breakdown collagen ( Liggins 2006 )
During ripening there is an influx of monocytes into the cervix
Physiological ripening is not mediated by an inflammatory cascade
Recent studies suggest that eosinophils promote the differentiation of the monocytes into alternatively activated macrophages (M2) during postpartum repair
Expression of epithelial specific genes such as Desmogleins and Keratin 16 as well as inflamatory associated genes and genes involved in ECM synthesis , processing and repair
In contrast to ripening phase , myeloid derived immune cells play an important role in this phase of remodelling
Postpartum cervical repair
Monocytes entered the cervix during ripening phase are differentiated to macrophages and polarised to both M1 and M2 phenotypes with onset of labour or postpartum
Matrix debris clear up
Increased activity of HA metabolising enzyme , hyaluronidase 1, and subsequent increase in low MW HA (Akgul et al .2012 )
Cervical ripening
Enzymatic degradation
Hormonal regulation
Increase in
proteoglycan
Inflammatory mechanism
↓P4
↑E2
↑RELAXIN
PROSTAGLANDIN
Hormonal regulation
Progesterone:
P4 or con. of P4 receptors cervical ripening
Activation of NFκB in turn
Inhibit P4 receptor activity TIMP’S
cervical ripening
.
Relaxin Relaxin stimulates MMPs expression on cervix. promotes both epithelial cells and stromal cells
accumulation
By stimulating cell proliferation& inhibiting apoptosis
Relaxin act on fibroblastic cell receptors
Relese of MMPs causes collagenolysis( TIMP’S)
Mechanism of relaxin induced hydration in cervix not understood.
But, Enlargement of cervial arteries my be a factor and it stimulate procollagenase and also reduces TIMP’s
Relaxin may act cervix through stimulation of PG synthesis
Prostaglandin
Prostaglandin have important role in cervical ripening PGE2 → Chemokine (IL8) → Neutrophils → degranulation → MMPs →
collagen degradation
A.-R. Fuchs et al. / Prostaglandins & other Lipid Mediators 70 (2002) 119–129
Estrogen Estrogen receptors are expressed in cervix at term.
sensory neurons have also been implicated in cervical ripening.
substance P release from neurons terminating in the cervix and spinal cord peaks before parturition.
mRNA levels of calcitonin gene related peptide,which colocalizes with substance P increases at term and its expression increased by estrogen
Trends in Endocrinology and Metabolism 21 (2010) 353–361
Withdrawal of P4 + Proinflam stimulus Act NFkB (Schmitz et al. 2004)
GAGCYTOKINES
-CERVIX
MACROPHAGE-FETAL
iNOs
COX2
NOPG
IL 8neutrophi
ls
IL 1,TNFα IL 8
FIBROBLAST
MMPsNEUTROPHIL
Inflammatory mechanism
Matrix Metalloproteinase (MMPs) play important role in cervical ripening
MMPs secreted by 1.Stromal cells
2.Fibroblasts
3.Smooth muscle cells
4.Inflammatory cells invading cervix(final)
Enzymatic degradation
Cervical total GAG content with progression of pregnancy &
accompanied by dramatic changes in composition.
Function of proteoglycans : 1.Decorin modulate the collagen fibril & spacing
and access to proteases.2. Versican It influences structural disorganization
of the ECM
Hyaluronan synthase 2 expression & subsequent in Hyaluronic acid (HA) is a distinct feature of cervical ripening.
Proteoglycans
(Mahendroo,et al 1996) Trends in Endocrinology and Metabolism 21 (2010) 353–361
In the first step (during ripening), hyaluronic acid & its association with proteoglycan ( versican) is required
Just prior to or during the onset of labor The expression of Hyaluronidase & ADAMTS1 leads
to the disruption of HA–versican cross links going to breakdown in to HA and versican, respectively
The breakdown to smaller size products might be a second step in the loss of cervical tensile strength and integrity required for cervical dilation and birth
(Mahendroo,et al 1996) Trends in Endocrinology and Metabolism 21 (2010) 353–361
(Mahendroo,et al 1996) Trends in Endocrinology and Metabolism 21 (2010) 353–361
(Mahendroo et al. 1999). Trends in Endocrinology and Metabolism 21 (2010) 353–361
conclusion
Incremental and progressisive changes in the ECM occur in a P4 rich environment during softening with further rapid and more aggressive changes to the ECM upon the loss of P4 function during cervical ripening and dilatation
To complete loop of remodelling and allow subsequent pregnancies, proinflammatory and immunosupressive processes modulate tissue repair postpartum
Dynamic, cumulative changes in the crvical ECM are initiated early in the pregnancy and culminate in the formation of highly disorganised ECM of unique composition that allows for the loss of tissue integrity resulting in cervical opening during parturation
Top Related