Compositions and methods for promoting hair growth
(75) Inventor: Boris E. Goldman, 2019 Breton, SE., Grand Rapids, Michigan 49546 (US)
Type: U.S.
( * ) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 U.S.C. 154(b) by 0 days.
(21) Appl. No.: 08/390,628
(22)
Filed: Feb. 17, 1995
Male pattern baldness (MPB) affects 60-80% of the male caucasian population with advancing age. Anderson, R. D., Clin. Plast. Surg. 1987:14,(3):447.
Various etiologies for MPB have been proposed which include age, genetic androgens and scalp tension. In particular, in 1942 and 1951, it was reported that the etiology of MPB was related to an interdependent relationship of age, genetic predisposition and androgens.
While not intending to be based by theory,
it is believed that local tissue hypoxia may be the underlying pathophysiology by which age, genetics and androgens interact to cause baldness. The method of the present invention is based on the recognition of this underlying baldness-inducing pathophysiology.
A study was performed to determine if there is a relative microvascular insufficiency and associated tissue hypoxia to regions of bald scalp in men with male pattern baldness as compared to hair bearing scalp in men with no baldness.
Eighteen male volunteers (age ≧18 years old), all of which were non-smokers, were used in the study. Nine of the men had MPB, with either Juri degree II or Ill (fronto-parietal or fronto-parietal-crown baldness). Juri, J. et al., Clin. Plast. Surg. 1982:9:255. Nine of the men were controls, with no MPB. Both groups had similar mean ages, the mean age of the bald subjects was 33.8 years .+-.2.3; while the mean age of the control subjects was 28.6 years .+-∅6. All measurements were obtained while the subjects were seated with an ambient temperature of about 25-30 degrees centigrade.
As shown in FIG. 2, the temporal scalp temperature was statistically significantly higher (approximately 1° F. (0.6°-1.1° F.)) than frontal scalp temperature in both bald subjects and controls. However, there was no significant difference in scalp temperatures between bald subjects and controls.
Thus, any differences in scalp blood flow and PtcO.sub.2 observed between bald subjects and controls can not be attributed to differences in scalp temperature.
Scalp blood flow, which is proportional to maximum initial slope (d PtcO.sub.2 /dt), was significantly lower in the bald subjects relative to controls. Comparing individual slopes reveals that
in the bald subjects the frontal (non-hair bearing region) blood flow (30.3.+-.3.93) was significantly less than the temporal (hair bearing region) blood flow (66.8.+-.5.40).
In control patients, there was no significant difference between the frontal blood flow (56.3.+-.9.32) and the temporal blood flow (79.2.+-.8.94).
Overall, scalp blood flow of control subjects was significantly greater than that of MPB subjects. Klemp et al., using a Xenon washout technique,
also found that subcutaneous blood flow to normal scalps was greater than that of MPB patients.
In addition, the present study was also able to document that
the temporal blood flow is significantly greater than the frontal blood flow in MPB subjects; while in control subjects there was no significant difference between frontal and temporal regions.
Also, there was no significant difference between blood flow to the temporal regions in MPB subjects and controls.
Finally, a previously unknown local tissue hypoxia in bald scalp compared to hair bearing scalp was identified.
Due to anatomical considerations, there is a relative microvascular insufficiency to regions of the scalp that lose hair in MPB. The scalp is not avascular in bald subjects; however, there is a relative microvascular insufficiency to those regions that lose hair compared to those that do not, and this results in a relative local tissue hypoxia below the level needed for hair growth.
The following suggests that a local tissue hypoxia may be the underlying pathophysiology by which age, genetics, and androgens interact to cause MPB.
Thus, improving local tissue PO.sub.2 of the frontal and crown scalp may be a prerequisite to preventing or reversing early MPB. This might be accomplished medically or surgically. However, a combined treatment of vasodilator, estradiol and/or a 5-α-reductase inhibitor presently represents the optimum medical treatment for early MPB.
Anatomy. Due to the underlying anatomy,
there is a relative microvascular insufficiency to regions of the scalp which lose hair in MPB, which is associated with a local tissue hypoxia in those regions.
The vascular supply of the scalp is derived from branches of the internal carotid artery and branches of the external carotid artery. Dingman, R. O. et al., Clin. Plast. Surg. 1982:9:131.
The frontal region of the scalp, which loses hair in MPB, is primarily supplied by the supraorbital and the supratrochlear arteries. These are relatively small branches of the internal carotid artery system. The temporal and occipital regions of the scalp, which do not lose hair in MPB, are supplied by larger branches of the external carotid artery. Specifically, these are the superficial temporal, posterior auricular, and occipital arteries. Further, the frontal and vertex regions of the scalp overly the galea aponeurotica, which is relatively avascular. The temporal and occipital regions of the scalp overly the temporalis and occipitalis muscles, which provide a rich network of musculocutaneous perforator blood vessels. These anatomical differences contribute to the tenuous nature of the dermal blood supply to the frontal and crown regions of the scalp.
The mechanism by which vascular insufficiency causes hair loss is not known. However, Hunt and Pai
showed that collagen syntheses by fibroblasts is significantly compromised when tissue PO.sub.2 <40 mm Hg. Hunt T. K. et al., Surg. Gynecol. Obstet. 1972:135:351. Ther may be an analogous situation with keratin production by hair follicle cells.
As described in Example 1,
there is a local tissue hypoxia to regions of the scalp that lose hair in MPB. This local tissue hypoxia may result in decreased mature keratin production and thus manifest as diminished hair fiber formation. Hunt and Pai, supra, have found that
in a hypoxic environment collagen synthesis is significantly decreased.
Given the inherent similarity between collagen and keratin, it is reasonable to presume that the inability to form covalent cross links
in a hypoxic environment will result in decreased keratin deposition similar to that found with collagen.
Decreased keratin deposition would result in decreased hair growth just as decreased wound healing was seen by Hunt and Pai when collagen deposition was decreased.
The DHT-receptor complex is responsible for external virilization and development of most male secondary sex characteristics. The conversion of testosterone to DHT requires the enzyme reductase activity (as well as NADPH). Takayasu, S. et al., JCE&M 1972:34(6):1098-1101. Estradiol production from testosterone also occurs in the periphery and recent immunohistochemical studies have revealed that the aromatase enzyme is present in hair follicles, with accentuated staining during anagen phase. Sawaya, M. E et al, J. Cutaneous. Pathol. 1992:19(4):309-314.
The aromatization of testosterone requires hydroxylation and oxidation.
Testosterone synthesis in MPB subjects should not be affected by scalp hypoxia, since the majority of testosterone in males is produced in the testis.
In the hypoxic environment of the bald scalp, DHT synthesis should not be significantly impaired.
Schweikert and Wilson have documented that
5-α-reduction of testosterone to DHT was increased in hair roots from the frontal scalps of balding individuals as compared to other hair bearing scalp sites in the same individuals or to frontal hair roots from women and non-balding men
Estradiol synthesis, however, should be stoichiometrically decreased in a hypoxic environment.
Three moles of oxygen are required to convert one mole of testosterone to one mole of estradiol. In a hypoxic region, the ratio of DHT to estradiol (DHT/estradiol) should be increased.
Sawaya has shown that
men with MPB have nearly a two fold increase in 5-α-reductase activity of hair follicles in balding frontal scalp, than in hair bearing occipital scalp.
However,
hair follicles in the frontal region had nearly three times less aromatase activity than hair follicles in the occipital region in men with MPB. Sawaya, M. E. Ann. N.Y. Acad. Sci. 1991:642:376-383. Finding that
the DHT/estradiol ratio is elevated in bald scalp as compared to hair bearing scalp in MPB subjects, is consistent with what would be expected in a hypoxic tissue environment.
If one were to develop a gradual local tissue hypoxia of the frontal scalp, the DHT/estradiol ratio might increase locally to a critical level at which point receptor hormone interactions might result in down regulation or inhibition of hair follicle cell function.
In turn, this might result in the ultimate conversion of terminal hair to villus hair, and the development of MPB. This inhibition may take the form of altering the number of hair follicle cells in anagen phase as compared to telogen phase.
Orfanos and Vogels, in a controlled, randomized, double blind study, found that
application of .025% estradiol for 6 months in subjects with MPB results in a decrease in the number of telogen hairs in 63% of those treated.
A similar reduction was found in only 37% of the controls.
No regrowth of new hair was found in either group. Orfanos. C. E., et al., Dermatologica 1980:161(2):124-132.
The addition of estradiol to bald scalp would serve to locally decrease the DHT/estradiol ratio, This appears to decrease the number of hair follicles in resting phase.
However, the delivery of adequate O.sub.2 would be required to achieve keratin synthesis and hair growth.
Thus, it is not surprising that hair regrowth did not occur with the addition of estradiol alone to bald scalps, without concomitant measures to correct the local tissue hypoxia.
Hair Follicle Genetics. In contrast to the "Donor Dominance" theory,
hair follicles in the frontal and crown regions of the scalp may not be genetically different from those in the temporal and occipital regions.
Rather,
a local tissue hypoxia may alter the local hormonal milieu, specifically the DHT/estradiol ratio, and thus account for the androgen stimulated difference in hair production in these regions in MPB subjects.
The clinical observation of progressive lower extremity hair loss in patients with peripheral vascular disease of the lower extremities favors a tissue hypoxia theory.
A donor dominance theory for hair loss in this clinical scenario, would imply that the hair follicles in the tibial region are genetically predisposed to lose hair while those in the thigh region are not in patients with distal lower extremity vascular disease.
In Orentreich's original experiment (1959),
bald scalp transplanted to hair-bearing scalp did not grow.
This may have occurred because the hair follicles in the bald scalp were irreversibly atrophic from chronic hypoxia. The fact that autografts from hair bearing scalp grew hair when transplanted to bald scalp appears to be contradictory.
However, when transplanting hair bearing autografts, an incision is made in the scalp at the recipient site. This adds the confounding variable of neovascularization in that region.
This neovascularization may provide sufficient O.sub.2 to allow the local hormonal milieu to be permissive for hair growth.
Hamilton has clearly documented that genetics play an important role in MPB. However, its role may be more specifically related to the genetic predisposition for a particular vascular anatomy or the predisposition for small vessel disease, than to differences between individual hair follicles.
http://www.lens.org/lens/patent/US_5480889_A/fulltext
Προσπάθησα να ξεχωρίσω τα πιο ουσιαστικά από αυτή την έρευνα ώστε να μην γίνει ιδιαίτερα κουραστική και δυσνόητη για όποιον ενδιαφέρεται.
Δεν ξέρω πόσο σημασία έχει το ότι δημοσιεύτηκε το 1995. Βέβαια για να την βρει κάποιος ίσως έπρεπε να ψάξει πολύ.
Την αναφέρω εδώ, γιατί εξηγεί τον λόγο ουσιαστικά που κάποια πράγματα, φυσιολογικά κατά κανόνα που συμβαίνουν κατά την εφηβεία σε όλους μας, όπως η αντίσταση στην ινσουλίνη και η αύξηση του ορμονικού μας προφίλ, έχουν αντίκτυπο σε όσους έχουμε προδιάθεση για ανδρογενετική αλωπεκία.
Αυτό που φάνηκε πολύ καθαρά από την έρευνα αυτή, είναι ότι στα σημεία που χάνουμε μαλλιά, την nw6 περιοχή δηλαδή, υπάρχει υποξικό περιβάλλον.
Αν κάποιος δεν γνωρίζει τι εννοούμε με τον όρο υποξία, αφορά μειωμένη παροχή οξυγόνου στους ιστούς μέσω του αίματος που το μεταφέρει. Αυτό μπορεί να συμβεί και τοπικά, όπως για παράδειγμα μετά από δυσλειτουργία ενός αιμοφόρου αγγείου αλλά και από άλλους παράγοντες όπως η πίεση του αίματος μας, η ποιότητα και το οξυγόνο που μεταφέρει.
Αυτό που έχει σημασία, είναι ότι σε ένα υποξικό περιβάλλον, η αναλογία της dht/estradiol αυξάνεται. Όσο πιο υποξικό αυτό το περιβάλλον, τόσο περισσότερο το ορμονικό προφίλ στην περιοχή διαταράσσεται.
Κατά κάποιο τρόπο, μπορούμε έτσι να εξηγήσουμε γιατί σε μερικούς δουλεύει κάτι, σε άλλους όχι, σε άλλους λιγότερο κλπ.
Επίσης γιατί τα μαλλιά πλάι και πίσω δεν επηρεάζονται, όπου πιστεύω δίνει μια πολύ λογική εξήγηση που αφορά στο ότι η nw6 περιοχή τροφοδοτείται από το αγγειακό σύστημα της έσω καρωτίδας αρτηρίας, ενώ οι περιοχές που δεν χάνουμε μαλλιά τροφοδοτούνται από το αγγειακό σύστημα της έξω καρωτίδας αρτηρίας.
Οι διαφορές σε αυτά τα 2 αγγειακά δίκτυα, είναι πως η έξω καρωτίδα αρτηρία, περιέχει ευρύτερες και μεγαλύτερες διακλαδώσεις αγγειακού δικτύου και έτσι παρέχει περισσότερο οξυγόνο στους ιστούς και στα κύτταρα που τροφοδοτούν, ενώ αντίθετα η έσω αρτηρία, είναι πιο επιρρεπής σε οξείδωση, στένωση και γενικότερα σε παθήσεις που αφορούν το αγγειακό σύστημα.
Τέλος, αναφέρει πως μεταμόσχευση θυλάκων από την φαλακρή περιοχή στην περιοχή τριχοφυίας δεν αναπτύχθηκαν, προφανώς λόγω της καταπόνησης - ατροφίας που είχαν υποστεί από την χρόνια υποξία.
Σε αντίθεση με τη μεταμόσχευση θυλάκων από άλλες περιοχές στη φαλακρή περιοχή που ενώ φαίνεται παράδοξο, αναφέρει πως η νεοαγγείωση είναι ο παράγοντας που παρακάμπτει αυτό το υποξικό περιβάλλον και τα μαλλιά αναπτύσσονται πλέον κανονικά.
Υπάρχουν και άλλες έρευνες, τις οποίες θα αναφέρω κάποια στιγμή, που δείχνουν τι συμβαίνει σε ένα υποξικό περιβάλλον σε ότι αφορά το κολλαγόνο, την εναπόθεση ασβεστίου και τους ινώδη και ουλώδη - συνδετικούς ιστούς.
Σημασία όμως έχει, πως κατά την προσωπική μου άποψη, τίποτα απ όλα αυτά δεν θα συναίβεναν αν δεν υπήρχε το θέμα της χρόνιας υποξίας στην περιοχή.
Συμπεράσματα μπορεί να βγάλει ο καθένας μόνος του για το τι θα κρατήσει και τι όχι.