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The Role of Low Molecular Weight Heparan Sulfate in Skin

Rejuvenation and Wound Healing

Mark J. Tager, M.D., Medical Consultant, Senté, Inc., San Diego, CA

Abstract

Low molecular weight Heparan Sulfate is the active ingredient found in Senté Dermal Repair Cream (San Diego, California). A biologically active glycosaminoglycan, Heparan Sulfate facilitates important wound healing and skin rejuvenation processes in the body including growth factor and stem cell enablement, collagen regulation, anti-oxidation, thrombolysis, skin-soothing and water-binding properties. Given the vast scientific evidence on the role that Heparan Sulfate plays in the skin, incorporation of the molecule as an active ingredient is both merited and beneficial to skin repair and health. Introduction

A burgeoning body of literature has accrued that demonstrates wound healing to be a complex,

yet orderly process that is essential to maintain the integrity of the largest organ in the body, the skin. In

the absence of wound healing, even the slightest compromise of the skin could be potentially fatal.

Fortunately, wound healing and regeneration processes exist, at the center of which reside Heparan

Sulfate, a glycosaminoglycan (GAG) – a linear polysaccharide consisting of repeating disaccharide units

of variable length – which when bound to a core protein form Heparan Sulfate proteoglycans (HSPGs)

(Figure 1).

Figure 1: Heparan Sulfate Molecule

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HSPGs are located in all tissues, and may be classified as either membrane-bound, secretory, or

basement membrane (extracellular matrix) associated (Table 1) 1.

Table 1: Heparan Sulfate Proteoglycans

TYPE EXAMPLES LOCATION FUNCTIONS - Membrane–Bound - Syndecans, Glypicans,

Betaglycan, CD44v3 - Epithelial cells, Fibroblasts, Leukocytes

- Cell - ECM attachment - Cell - cell interactions - Cell motility - Co-receptors - Ligand binding and processing - Cytokine, Chemokine, Growth Factor regulation

- Secretory vesicles - Serglycin - Mast cells, Hematopoietic cells

- Packaging and maintenance of granular contents - Process regulation after release (i.e. inflammation and wound repair)

- Basement membrane - Perlecan, Agrin, Collagen XVIII

- Basement membranes, Epithelial cells

- Organize basement membrane structure and function - Facilitate cell migration

HSPGs serve integral functions in the numerous and complex pathways that contribute to wound

healing including, but not limited to, cellular adhesion, migration, and differentiation, regulation of

growth factor expression, organization and maintenance of the basement membrane structure and function

and facilitation of stem cell recruitment and differentiation (Figure 2) 2-7.

Figure 2: Functions of Heparan Sulfate Proteoglycans !

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!!!!!!!!!!!!!!!!!!!!!!!(Esko Labrotory.n.d. Retrieved from http://eskolab.ucsd.edu/vascular.shtml )

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Unlike other proteoglycans, HSPGs are located throughout all layers of the skin. In addition,

improvements in diabetic skin ulcers and retardation of the aging process further support the importance

of HSPGs8,9,10,11.

Role of Heparan Sulfate in Wound Healing In order to understand Heparan Sulfate’s role in wound healing, it is essential to be familiar with

its critical role in maintaining skin health. HSPGs have the unique ability to bind and interact with many

components of the extracellular matrix. Further, HSPGs are responsible for maintaining the structure of

the basement membrane, regulating many interactions with growth factors and other extracellular matrix

proteins, and for directing cellular adhesion, migration and differentiation.

Following injury, normal wound healing usually undergoes an orderly process of hemostasis and

inflammation, a proliferative phase consisting primarily of re-epithelialization, angiogenesis, and collagen

formation, and tissue remodeling culminating in formation of a scar 12,13. HSPGs are integral throughout

the entire wound healing process with the ultimate goal being restoration of skin health. Certain features

of HSPGs (Table 2) 1 may explain their ability to coordinate many of the complex mechanisms that

contribute to wound healing (Table 3) 8,14-19.

Table 2 Table 3

Features of Heparan Sulfate Proteoglycans

Contributions of HSPG to Wound Healing

• Polyanionic – attract and retain water • Variable GAG chain size and number -

depending on source and growth conditions

• Not limited to interact with only HS – modifiable

• Number and sulfation state variability • Dynamic ligand binding sites • Properties dependent on cell type

• Attract and retain water • Organize basement membrane • Mediate cell migration, proliferation and

differentiation • Mediate growth factor synthesis and

expression • Mediate chemokine and chemokine

receptor expression and function • Regulate enzyme function • Regulates inflammatory and

hematopoietic response • Regulates hemostasis

Throughout the wound healing process HSPGs essentially facilitate similar processes; however,

the components involved differ. For example, HSPGs primarily address hemostasis 20 and inflammation 9,21 in the early phase of wound healing while they primarily address the tensile properties of the healing

wound at later stages.

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Effect of Aging and Disease on Wound Healing

The effects of aging and disease on wound healing are complex and varied depending on the

model used for assessment 11,22,23. As noted in (Figure 3) as skin ages there is atrophy of the extracellular

and cellular matrix, loss of vascularization, alteration in collagen organization, and thinning of the

epidermis.

Figure 3: Aging of the Skin

Whereas older animals may still have relatively normal healing, albeit delayed in one model 22,

regeneration may be the primary mechanism of wound healing in young skin 10,11. It is clear that there is

altered expression of skin proteoglycans, which may play a role in the physical properties and response to

injury of skin 24.

Altered expression of HSPGs also occurs in disease states, such as diabetes and smoking that lead

to suboptimal wound healing. In both of these disease states, normal wound healing may be restored

through the delivery of Heparan Sulfate analogues 23. Of note, restoration of the extracellular matrix

milieu towards a more normal one has been show to improve wound healing towards normal.

Heparan Sulfate in Tissue Regeneration

One of the more exciting areas in skin biology is that of regeneration. Consider the potential

benefits of being able to regenerate normal skin (i.e. scar less skin). As discussed wound repair in fetal

skin does just that. Heparan Sulfate is involved in and regulates several aspects of stem cell physiology

that make it a prime candidate to assist with regeneration of skin following injury.

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Heparan Sulfate has been shown to mediate hematopoietic stem cell homing 25. It also has been

shown to facilitate growth factor mediated mesoderm differentiation of embryonic stem cells 3.

Importantly, Heparan Sulfate exerts control over the skin’s stem cell niche 7. Taken together, these and

other data support the possibility of tissue regeneration following injury with targeted use of Heparan

Sulfate and HSPGs.

Clinical Potential of Heparan Sulfate for Wound Healing, Tissue Rejuvenation and Tissue Regeneration

An understanding of the critical role that Heparan Sulfate plays in maintaining skin health and

promoting wound healing, has lead to the development of a topical low molecular weight formulation of

Heparan Sulfate (Senté Dermal Repair Cream). The low molecular weight HS formulation allows for

robust penetration in the epidermis. Although the HS molecule is 10k Dalton’s, penetration is thought to

be facilitated by the long thin, rod-like molecular structure and it’s negative charge (Figure 4).

Figure 4: Penetration of the epidermis by low molecular weight Heparan Sulfate in mouse skin with two applications 1% HS

Low molecular weight Heparan Sulfate is significantly smaller than proteins in topically applied

growth factor products whose molecular weights vary from 18kd-140kd. Further the low molecular

weight Heparan Sulfate was shown to induce various effects, including a profound rehydration of the

skin, potential anti aging effects, and a beneficial effect on the combined endpoint of subjective

symptoms and objective signs (hematoma color) following a surgical procedure (Figure 5). The effect on

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tissue bruising is thought to be mediated by thrombinogenesis and promotion of the fibrinolytic process

through both intrinsic and extrinsic pathways.

Heparan Sulfate has been shown to activate proactivants, antagonize plasmin inhibitors, produce

anti-Xa and anti-complement activity and activate anti-thrombin III 26. Although these results are

promising, further studies on the efficacy of this agent in other populations need to be performed before it

can be widely adopted.

Figure 5: Effect of Heparan Sulfate Cream on Hematomas and/or Subcutaneous Hematic Extravasations

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(Polieri, T. Et al, 2012)

Summary

Heparan Sulfate is a ubiquitous glycosaminoglycan that exists in all tissue types in its free or

protein bound forms. Heparan Sulfate regulates numerous processes critical to skin homeostasis, repair,

and regeneration. A proprietary low molecular weight Heparan Sulfate has been developed to exploit the

beneficial effects of naturally occurring Heparan Sulfate. This low molecular weight Heparan Sulfate is

the active ingredient in Senté’ Dermal Repair Cream, which has shown significant promise in this regard.

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References

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162 South Rancho Santa Fe Road, Suite F40 Encinitas, CA 92024

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