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COPYRIGHT 2008 JOURNAL OF DRUGS IN DERMATOLOGY INCREASE IN COLLAGEN TURNOVER INDUCED BY INTRADERMAL INJECTION OF CARBON DIOXIDE IN RATS Julio Cesar Tavares Ferreira MD,a Alessandra Haddad MD PhD,b Simone Arruda Navarro Tavaresc a. General Surgeon, Member of the Brazilian College of Surgeons, Member of Brazilian Medical Society for Intradermal Therapy b. Plastic Surgeon, MSc in Reconstructive Plastic Surgery from the Federal University of São Paulo – Escola Paulista de Medicina, Member of the Brazilian Society of Plastic Surgeons c. Physiotherapist, Specialist in Dermatologic-Functional Physiotherapy from Faculdade Integrada do Ceará; Member of the Brazilian Aesthetics Academy Abstract
Introduction: Results from clinical observations have demonstrated that percutaneous infiltration of carbon dioxide im-
proves the appearance of the skin in adjacent areas. No studies have been found in the literature that showed evidence
of histological changes caused by carbon dioxide injections.
Objectives and Methods: A blind cross-sectional pilot study was performed in the Departments of Pharmacology and
Morphology of the Federal University of Ceará, with the aim of histologically investigating whether intradermal and/or
subcutaneous injection of medicinal carbon dioxide would increase collagen turnover in rats. Ten male Wistar rats were
used, aged 3 months (2 animals) and 14 months (8 animals). The 2 younger rats were used as controls. Four of the older
rats received injections of saline solution (0.9%), and were also considered to be controls. In the remaining 4, carbon
dioxide was injected into the subcutaneous cellular tissue and intradermally. Biopsy samples were collected before and
after treatment with carbon dioxide.
Results: Collagen turnover increased in the treated animals in comparison with the controls. Compression of collagen
bundles in the tissue samples where intradermal injection was used was more intense than in the subcutaneous treatment.
The histological characteristics of the samples with carbon dioxide injected intradermally were similar to the characteristics
of the younger rats (controls).
Conclusions: The results obtained corroborate clinical observations of aesthetic improvements in the facial skin with car-
bon dioxide injections. Future research should address the comparison between intradermal and subcutaneous injections,
the volume of gas used, and the frequency of treatment sessions.
medium through which nutrients are offered to cells and into Human tissue changes with age. In the skin, these modifi- which cellular excreta are ejected.21,22 The extracellular ma- cations are more easily recognized.1,2 The modifications to the trix is composed of fluid and fibrous components. One of the collagen and elastin system cause wrinkles, atrophy, grooves, most common fluid components of the ECM is hyaluronic ptosis, and laxity. These are the most evident signs of old acid. In combination with certain proteins, this becomes a skin,3-6 which can result in significant psychological problems highly viscous and hydrophilic mucopolysaccharide. Elastin, for individuals. There is increasing interest in therapeutic fibronectin, and collagen are the basic elements of the fibrous resources for solving such problems.7 For this reason, the mor- component of the dermis. Collagen is the most abundant of phological and structural changes to the dermis related to these, and it is the main element of human skin. It is re- aging are constantly being studied. sponsible for maintaining the structural integrity of the skinby joining cells to other cells and the ECM. Many authors have shown that there are beneficial effectsfrom subcutaneous carbon dioxide (CO Collagen is an insoluble protein that forms fibers, which in 2) therapy for several clinical conditions.7-20 Intradermal injection of CO turn join together in bundles. Fibroblasts secrete the pre- been studied recently, especially because of the clinically fa- cursors of collagen, protocollagen types 1 and 3. Aging brings vorable results observed, its low cost, and safety.8 However, a decrease in the number of skin fibroblasts and, at the same there is a lack of scientific evidence regarding the histolog- time, an increase in collagenases, which catalyze the degra- ical modifications that occur with the intradermal injection dation of collagen. It also causes a reduction in the number of cells and vessels and this, together with biochemical changes in collagen constitution, leads to thinner collagen fibers. The collagen content per unit of skin area decreases Senile dermal modifications occur mainly in the extracellu- by 1% per year over the course of adult life and collagen fibers lar matrix (ECM), a substance within the extracellular space become disorganized, less compact and more granular; col- that provides the supporting structure to cells, as well as lagen becomes more rigid and less elastic. The consequence resistance to compression and stretching. It is also the of this is the loss of dermal volume in older individuals.

JOURNAL OF DRUGS IN DERMATOLOGY INCREASE IN COLLAGEN TURNOVER INDUCED BY MARCH 2008 • VOLUME 7 • ISSUE 3 INTRADERMAL INJECTION OF CARBON DIOXIDE IN RATS Some other clinical manifestations of aging, such as wrinkles, contraindicated for phlebitis, cardiac/respiratory insuffi- grooves, and atrophy, as well as changes in facial format, are ciency, renal/hepatic insufficiency, severe arterial hyperten- due to the new architecture of the skin's conjunctive tissue.23-35 sion, and pregnancy.8,10 Aging is a progressive, universal process that is subject to en-vironmental, genetic, and hormonal factors.7 Among the Carbon dioxide provokes local vasodilation and increased re- environmental factors associated with skin aging, ultraviolet gional blood flow and oxygen pressure; there is a reduction in radiation is the most important.36,37 the affinity of hemoglobin for oxygen, thereby resulting in moreavailability of oxygen for the tissue.36 Many authors have ob- served this phenomenon after subcutaneous injection of CO2, Many treatments have been used to reduce the effects of the using many different examination techniques.12,15-17,40-42 skin aging process. Antiaging treatments have included tretinoin (retinoic acid), antioxidants like vitamins C and E,phytoestrogens, dimethylaminoethanol, and many others in This study was designed to investigate whether CO2 injec- the form of creams, gels, and lotions. They can be used pro- tion into the dermis of Wistar rats can improve collagen phylactically, as coadjuvant therapies in some circumstances,or as the sole treatment. Invasive techniques are also availableand these seem to be more efficient, including chemical or Figure 1a. Procedures undertaken with the 2 younger Wistar rats (3
laser peeling, dermal filling with various substances or with months old, white circles) and the 8 older rats (14 months old,black/gray circles): GTI (intradermal CO infiltration), GTS (sub- solid implants, botulinum toxin, and many plastic surgery cutaneous CO infiltration), or infiltration of saline solution.
techniques. More recently, hormonal modulation has been proposed as a prophylactic method,38 and CO2 therapy is also being used as a promising technique against skin aging.8 Carbon Dioxide Therapy
Subcutaneous administration of CO2 is popularly known as
carboxitherapy.8,10 Subcutaneous infiltration is a recent in-novation in medicine, but the administration of CO2 began in France in the 1930s, where peripheral arteriopathy wastreated with CO2 gas.10,12,39,40 The publication of studies on CO2 therapy began in the 1950s, but most of the work papers were published between 1985 and 2002.12,14 The main indications for CO2 therapy are peripheral arteri- opathy,14,39 acrocyanotic syndrome,19 venous insufficiencyand foot and leg ulcers,13,41 adipose tissue accumulation,18,42symmetrical multiple lipomatosis,18 and others. In the 1990s, video laparoscopy was used for injecting quan-tities of more than 3 liters of CO2,8,43 at rates reaching 1 liter per minute without adverse effects.43 Thus, the use of this gas,which is formed naturally by the body at rest and during ex-ercise,10,42 is safe. Moreover, it is eliminated within a shorttime. Adjacent to the areas where CO2 was injected, surgeons noticed reductions in the quantities of adipose tissue and fibrous edema.8,15 This prompted new clinical research usingsubcutaneous CO2 to treat adiposity and aging.7,9,18 A histological study on patients treated with CO Figure 1b. Example of infiltration and punch biopsy site.
tions for adiposity showed that the treatment did not lead toany damage affecting the connective tissue, vascular bed, ornerve structures.15 The recent use of CO2 in angiographic procedures has proven the safety of this cheap and nonal-lergenic gas.44 Carbon dioxide does not provoke embolismeven with bolus injections of 100 ml, and a continuous fluxof 20 to 30 ml/second does not induce adverse reactions.45Local or systemic complications have not been reported inthe literature.11,15,46 The only side effects are pain, hematomascaused by the puncture, and a crepitation sensation causedby the small local subcutaneous emphysema, which disap-pears within 30 minutes.7,8 Carbon dioxide injections are

JOURNAL OF DRUGS IN DERMATOLOGY INCREASE IN COLLAGEN TURNOVER INDUCED BY MARCH 2008 • VOLUME 7 • ISSUE 3 INTRADERMAL INJECTION OF CARBON DIOXIDE IN RATS turnover and compare injections in the subcutaneous and Biopsy and Histological Analysis
intradermal layers.
On the sixth day after the CO2 infiltration therapy, the 8 14-month-old rats (4 treated and 4 controls) were again anesthetized with ether and the total skin thickness was This pilot study was a blind, interventional, cross-sectional biopsied using a 1-mm punch at the center of the 1-cm study, with qualitative analysis of the results, carried out in squares. Both the preprocedure biopsy specimens (from all 10 the Pharmacology and Morphology Departments of the Fed- animals) and the biopsy specimens collected after the pro- eral University of Ceará (UFC), from February to March in cedure (from the treatment group) were prepared for histo- 2006. The experimental study followed the principles for logical analysis. research using animals: the subjects had full access to waterand food before and after the procedure and their life cycles The specimens were fixed in formaldehyde and dehydrated in (diurnal and nocturnal) were respected. The study was ap- a series of increasing concentrations of ethyl alcohol. After proved by the Ethics Committee for Animal Research of this this, they were diaphanized, embedded in paraffin blocks and university. The animals were provided by the Pharmacology cut into 4-mm sections. The specimens were then subjected Department of UFC.
to Mallory's trichrome staining, in which collagen synthesis Ten male Wistar rats, born from the same mother and father,2 of them young (3 months old) and 8 of them old (14 Figure 2. Photomicrograph of Wistar rat dermis biopsy a) before
months old), were used. The rats were subjected to a skin and b) after subcutaneous CO infiltration, with less dispersed and
more numerous collagen fibers.
biopsy 1 day before the procedure and those presenting withdermatological or subcutaneous problems were excluded.
After either subcutaneous or intradermal CO the morphological alterations (quantity and arrangement) tothe dermal collagen fibers were evaluated (Figure 1a).
Preprocedure Biopsy
After undergoing anesthesia (by means of inhaling ether
from a cotton ball inside a ventilated chamber), all 10 ani-
mals (young and old) were shaved and skin samples were
collected by punch biopsy (1 mm diameter in the right
posterior flank, 3 cm distally from the femoral joint).
Procedure
One day after the first biopsy, areas of 1 cm2 were shaved and
marked out on the skin of each of the 8 14-month-old rats
(Group T=treated): 1 area on the left anterior flank and the
other on the right anterior flank (3 cm posteriorly to the
scapulohumeral joint).
A disposable needle (30 G 1/2) was attached to the Carbtekcarboxitherapy equipment (Estek, São Paulo, Brazil) bymeans of an appropriate device with an anti-reflux filter. Themanometer pressure was calibrated to 15 mmHg, with a flowvelocity of 20 mmHg. For 4 of the 14-month-old rats, CO2 infiltration was performed intradermally (GTI) on the right side. This was done by meansof introducing only the bevel of the needle into 1 of the ver-tices of the square that was marked out, until the intradermalinfiltration of CO2 caused a white papule in the center of the marked square. On the left side of the same rats, the injectionwas subcutaneous (GTS), with 3 mm of the needle introducedfrom 1 of the vertices of the square marked out, until the gasvolume was enough to cause skin distension in the marked area.
The point of the needle was kept in the corner of the square topreserve the central area for puncture biopsy (Figure 1b).
For the other 4 14-month-old rats (control group), injectionof saline solution (0.9%) into the subcutaneous tissue causeddistension of the areas marked out with squares.

JOURNAL OF DRUGS IN DERMATOLOGY INCREASE IN COLLAGEN TURNOVER INDUCED BY MARCH 2008 • VOLUME 7 • ISSUE 3 INTRADERMAL INJECTION OF CARBON DIOXIDE IN RATS is shown in blue. The analysis was performed by an experi- identification of each animal specimen (ie, whether it was enced pathologist using a binocular optical microscope with from the treated or the control group).
millimeter scale (Leitz Periplan GF 100X, Wetzlar, Germany).
Digital photos of the histological slices were taken (Collpix camera, Nikon, Japan). The pathologist was not aware of the No side effects were observed after the injection of CO2 or saline solution.
Figure 3. Photomicrograph of rat dermis biopsy after intradermal
Histological analysis showed intense collagen turnover in CO infiltration in a) 14-month-old Wistar rat and b) 3-month-old
the skin samples of the animals treated with CO2, especially in those with intradermal treatment, in comparison with theanimals that had only had saline solution injected in the der- mis. Collagen synthesis was shown by Mallory's staining. Thecollagen fibers were less dispersed (Figure 2) following bothsubcutaneous and intradermal CO2 infiltration. Intradermal injection made the collagen fibers more compact than did subcutaneous injection. After intradermal infiltration, the col-lagen arrangement in the dermis of the old animals in thisstudy was similar to that of the 2 young rats (Figure 3).
Subcutaneous saline solution injection into the control grouprats caused greater collagen fragmentation, comparing thepreprocedure biopsy with the biopsy after the procedure inthe control group (Figure 4).
Discussion
This study showed visible compacting of collagen fibers fol-
lowing CO2 infiltration, especially among the skin samples
with intradermal infiltration. Oria et al (2003), in a studyusing cadavers, had already demonstrated that aging causedthe collagen bundles to disperse, since collagen fibers aremore compact in young humans.47 In fact, after CO2 injection, the arrangement of the collagen in the dermis of the older ratsin this study was similar to that of the younger animals.
Figure 4. Photomicrograph of rat dermis biopsy after saline solu-
tion infiltration in a 14-month-old Wistar rat (control).
JOURNAL OF DRUGS IN DERMATOLOGY INCREASE IN COLLAGEN TURNOVER INDUCED BY MARCH 2008 • VOLUME 7 • ISSUE 3 INTRADERMAL INJECTION OF CARBON DIOXIDE IN RATS Many authors have shown that injection of CO 3. Lavker RM, Zheng PS, Dong G. Morphology of aged skin. Clin subcutaneous layer leads to an increase in the blood flow to Geriatr Med. 1989;5:53-67.
the area.12,15-17,40-42 This blood flow increase may lead to 4. Tsuji T, Yorifuji T, Hayashi Y, Hamada T. Light and scanning elec- neoangiogenesis in cases of chronic exposure to CO tron microscopic studies on wrinkles in aged persons' skin. Br J tion,14 and could partially explain the more intense collagen synthesis adjacent to the treated area in this study. In a ran- 5. Castelo-Branco C, Pons F, Gratacos E, et al. Relationship between domized, controlled study by Brandi et al, subcutaneous skin collagen and bone changes during aging. Maturitas. 1994;18: injections of CO 2 to treat adiposity caused an increase in oxy- gen pressure, and skin thickness, and a decrease in the cir- 6. Vitellaro-Zuccarello L, Cappelletti S, Dal Pozzo Rossi V, Sari-Gorla cumference of the treated areas. A histological examination M. Stereological analysis of collagen and elastic fibers in the nor- showed that the adipocyte membrane was broken, and that mal human dermis: variability with age, sex, and body region. Anat connective tissue, vessels, and nerves were preserved.15 Other studies are necessary to confirm these findings and the exact 7. Kede MPV, Sabatovich O. Dermatologia Estética. Rio de Janeiro: mechanism of action. It may be necessary to use hyaluronic Atheneu; 2004.
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ADDRESS FOR CORRESPONDENCE
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